Response to Peer Review Comments on the
May 2012 and April 2013 Drafts of
An Assessment of Potential Mining Impacts on Salmon
Ecosystems of Bristol Ba y, Alaska
U.S. Environmental Protection Agency
Region 10
Seattle, WA
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Table of Contents
1. OVERVIEW OF PEER REVIEW PROCESS FOR THE BRISTOL BAY ASSESSMENT 1
1.1 Peer Review of the May 2012 Draft 1
1.2 Follow-on Peer Review of the April 2013 Draft 2
2. STRUCTURE OF THE PEER REVIEW RESPONSE TO COMMENTS DOCUMENT 3
3. PEER REVIEWER COMMENTS AND EPA RESPONSES 4
3.1 Key Recommendations 4
3.2 General Impressions 47
3.3 Charge Question 1 73
3.4 Charge Question 2 90
3.5 Charge Question 3 112
3.6 Charge Question 4 127
3.7 Charge Question 5 146
3.8 Charge Question 6 161
3.9 Charge Question 7 174
3.10 Charge Question 8 184
3.11 Charge Question 9 194
3.12 Charge Question 10 205
3.13 Charge Question 11 225
3.14 Charge Question 12 235
3.15 Charge Question 13 250
3.16 Charge Question 14 259
3.17 Specific Observations 272
3.18 Appendices I and J 331
3.19 Follow-on Comments outside the Scope of the Original Peer Review 333
3.20 Follow-on Reviews Organized by Chapter 346
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In May 2012, the U.S. Environmental Protection Agency (EPA) publicly released the 1st external
review draft of An Assessment of Potential Mining Impacts on Salmon Ecosystems of Bristol Bay,
Alaska (hereafter, the May 2012 draft). This document was externally reviewed by 12 independently
selected expert peer reviewers. Based in part on the feedback received from this peer review, EPA
revised the draft assessment and, in April 2013, publicly released the 2nd external review draft of the
assessment (hereafter, the April 2013 draft). EPA then asked the same 12 peer reviewers to evaluate
how well the April 2013 draft addressed their original comments on the May 2012 draft.
This document presents (1) an overview of the peer review process, (2) all of the peer reviewers'
comments on both the May 2012 and April 2013 drafts of the assessment, and (3) EPA's responses to
the peer reviewers' comments.
1. OVERVIEW OF PEER REVIEW PROCESS FOR THE
BRISTOL BAY ASSESSMENT
1.1 Peer Review of the May 2012 Draft
EPA tasked Versar, an independent contractor, with conducting an external peer review of the May
2012 draft of the assessment. The peer review process is designed to provide a documented,
independent, and critical review of a draft assessment. Its purpose is to identify any problems, errors,
or necessary improvements to a document prior to its being published or otherwise released as a final
document. To conduct this external peer review, Versar assembled 12 independent experts to serve as
peer reviewers. These reviewers were selected from a pool of candidates that included experts
suggested during a public nomination process. In assembling the peer reviewers, Versar evaluated the
qualifications of each peer review candidate and conducted a thorough conflict of interest (COI)
screening process.
The 12 selected expert peer reviewers were:
• David A. Atkins, M.S., Watershed Environmental, LLC
• Steve Buckley, M.S., CPG, WHPacific
• Courtney Carothers, Ph.D., University of Alaska Fairbanks
• Dennis D. Dauble, Ph.D., Washington State University
• Gordon H. Reeves, Ph.D., USDA Pacific Northwest Research Station
• Charles W. Slaughter, Ph.D., University of Idaho
• John D. Stednick, Ph.D., Colorado State University
• Roy A. Stein, Ph.D., The Ohio State University (Peer Review Chair)
• William A. Stubblefield, Ph.D., Oregon State University
• Dirk van Zyl, Ph.D., P.E., University of British Columbia
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• Phyllis K. Weber Scannell, Ph.D., Scannell Scientific Services
• Paul Whitney, Ph.D., Independent Consultant
The peer reviewers were asked to evaluate the May 2012 draft assessment and provide a written
review of the draft document (the main assessment report and its appendices) by responding to 14
charge questions developed by EPA with input from public commenters. Peer reviewers were
charged only with evaluating the quality of the science included in the draft assessment and were not
charged with making any regulatory recommendations, commenting on any policy implications of
EPA's role or mining development in the region, or reaching consensus in either their deliberations
(during the peer review meeting, see below) or written comments. Peer reviewers were provided with
a summary of public comments on the May 2012 draft and given access to all public comments
submitted during the 60-day public comment period; however, they were not asked to evaluate or
respond to these submitted public comments.
A 3-day peer review meeting, coordinated by Versar, was held in Anchorage, Alaska on August 7-9,
2012. On the first day of the meeting peer reviewers heard testimony from approximately 100
members of the public. Peer reviewers deliberated among themselves on the second and third days of
the meeting; these deliberations were open to the public on the second but not the third day.
Following the public peer review meeting, peer reviewers were given additional time to complete
their individual written reviews. Versar provided these final written comments to EPA in their Final
Peer Review Meeting Summary Report for the May 2012 draft, which EPA received in September
2012. This document was released to the public in November 2012, and is available at
http://www.epa.gov/ncea/pdfs/bristolbav/Final-Peer-Review-Report-Bristol-Bav.pdf. EPA considered
these peer review comments, as well as comments received during the 60-day public comment
period, as we revised the May 2012 draft of the assessment.
1.2 Follow-on Peer Review of the April 2013 Draft
In April 2013, the same 12 peer reviewers were asked to conduct a follow-on review to evaluate
whether the April 2013 draft assessment was responsive to their original comments. EPA provided
reviewers with a draft response to comments document, in which EPA responses to peer review
comments on the May 2012 draft assessment were added to the Final Peer Review Meeting Summary
Report submitted by Versar.
In the follow-on review, peer reviewers were asked to go through their comments on the May 2012
draft, review EPA's draft responses to their original comments, and evaluate whether their original
review comments had been addressed sufficiently and whether appropriate changes had been
incorporated into the April 2013 draft of the assessment. EPA received these follow-on review
comments directly from the 12 peer reviewers in August to September 2013. A compilation of these
reviews, as they were received from each individual reviewer, is available at
http://cfpub. epa.gov/ncea/bristolbav/recordisplav.cfm?deid=242810#Download.
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2. STRUCTURE OF THE PEER REVIEW RESPONSE TO
COMMENTS DOCUMENT
This document includes all of the review comments received from the 12 expert peer reviewers on
both the May 2012 and April 2013 drafts of the assessment, as well as EPA's responses to those
comments. It generally has been organized to follow the structure of the Final Peer Review Meeting
Summary Report submitted by to EPA by Versar following peer review of the May 2012 draft.
Four types of comments and responses are included in Section 3 of this final response to comments
document, each in a different font type:
1. Peer reviewer comments on the May 2012 draft of the assessment (from Versar's Final Peer
Review Meeting Summary Report) are shown in plain black text.
2. EPA '.v responses to these review comments are shown in bold black italicized text.
3. Peer reviewer follow-on comments on the April 2013 draft of the assessment and EPA's
draft responses to peer review comments are shown in bold blue text.
4. EPA's final responses to peer reviewer follow-on comments on the April 2013 draft are
shown in bold blue italicized text.
In many cases only the first two comment types are shown, indicating that peer reviewers did not
have follow-on comments regarding their original comments or EPA's responses. Also, comments
from non-EPA authors of the appendices are provided in a few instances, using the font type under 2
above.
It is important to keep in mind that references to specific text features (chapters, sections, tables,
figures, and text boxes) in the different comment types are based on different drafts of the
assessment. In general, text features cited in type 1 comments (initial reviewer comments) refer to the
May 2012 (original) draft of the assessment; text features cited in type 2 comments (initial EPA
responses) refer to either the May 2012 or April 2013 (revised) draft of the assessment; text features
cited in type 3 comments (reviewer responses) refer to the April 2013 draft; and text features cited in
type 4 comments (final EPA responses) refer to the final assessment. We have tried to note the
appropriate draft of the assessment in our responses. Although earlier drafts of the assessment have
now been archived, they are still available to the public at the link provided in Section 1.1 (under the
History and Chronology tab).
Comments and responses are organized into the following sections, largely based on the structure of
Versar's final peer review report for the May 2012 draft of the assessment:
• Key Recommendations: major recommendations put forth by the peer reviewers, organized
by recommendation; each reviewer's comments on EPA's initial responses, where they were
provided, are listed under each recommendation.
• General Impressions: peer reviewers' individual general impressions, organized by
reviewer.
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• Charge Questions 1 through 14: peer reviewers' individual comments on the 14 charge
questions provided by EPA for review of the May 2012 draft, organized by reviewer.
• Specific Observations: peer reviewers' individual specific observations, organized by
reviewer.
• Appendices I and J: peer reviewers' comments on Appendix I (revised) and Appendix J
(new in the April 2013 draft), organized by reviewer.
• Follow-on Comments outside the Scope of the Original Peer Review: peer reviewers'
individual comments on the April 2013 draft that did not follow the structure of the original
peer review report, organized by reviewer. Procedural comments (e.g., cover letter text, etc.)
are included in this section.
• Follow-on Reviews Organized by Chapter: two sets of follow-on review comments for the
April 2013 draft (from Dr. Stein and Dr. Stednick) that were organized by assessment
chapter, rather than by the final peer review report.
3. PEER REVIEWER COMMENTS AND EPA RESPONSES
3.1 Key Recommendations
Scope of the Document
Articulate the purpose of the document more clearly via a primer on the Ecological Risk Assessment
process. If the purpose of the assessment is to inform EPA as the decision maker, then the level of
detail should correspond to this purpose. The authors should justify and explain what level of detail is
required.
EPA RESPONSE: Additional information on both the purpose of the assessment and ecological
risk assessment (ERA) in general has been added to Chapters 1 and 2, as well as the Executive
Summary. Section 1.2 includes information about the use of the assessment. The assessment has
been reorganized into two major sections (problem formulation, risk analysis and
characterization) to clarify where different chapters fall in the typical ERA process.
ATKINS RESPONSE: This response is adequate.
EPA FINAL RESPONSE: No response required.
BUCKLEY RESPONSE: The reorganization of the report clarifies the purpose of the
assessment and includes information on the intended audience. It also explains the ERA
process much better than the initial draft. The overall organization of the assessment has been
improved by identifying the assessment endpoints first, before outlining the potential risks. In
addition, the elimination of the No Failure/Failure sections in the draft report helps avoid
confusion on what type of system failures are being assessed.
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EPA FINAL RESPONSE: No response required.
DAUBLE RESPONSE: The first page of the Executive Summary now provides an excellent
lead-in to the document. The first four paragraphs clearly establish context and intent of the
main Assessment document. Further detail is provided in the first section, Scope of the
Assessment.
EPA FINAL RESPONSE: No response required.
SLAUGHTER RESPONSE: Chapter 1 provides a clear statement of the rationale underlying
the Assessment - why it was undertaken, an overview of how the Assessment was developed,
and a brief statement on how it might be used.
EPA FINAL RESPONSE: No response required.
WEBER SCANNELL RESPONSE: The reviewer believes that this comment has been
addressed in the revised Assessment. Of particular value is the description of the authority
under which the Assessment has been conducted (Section 1.1, page 1-2). The discussion of
limitations of the Assessment clarifies what is addressed and what is not.
EPA FINAL RESPONSE: No response required.
Include a statement upfront about the role of risk managers and other audiences, such as project
managers/engineers, regulators, mine owners/operators. Knowing their role ensures inclusion of
information necessary for any risk assessment by (1) describing the need for a risk assessment, (2)
listing those decisions influenced, and (3) characterizing what risk managers require from the risk
assessment.
EPA RESPONSE: Section 1.2 of the revised assessment discusses the use of the assessment.
ATKINS RESPONSE: This response is adequate.
EPA FINAL RESPONSE: No response required.
BUCKLEY RESPONSE: Section 1.2 discusses the use of the assessment in greater detail than
the initial draft. This information is also treated more thoroughly in the Executive Summary.
EPA FINAL RESPONSE: No response required.
DAUBLE RESPONSE: This comment was adequately described in Section 1.2 as well as
paragraph 3-5 of the Executive Summary.
EPA FINAL RESPONSE: No response required.
SLAUGHTER RESPONSE: Section 1.2 discusses possible use of the assessment, but does not
identify or define "risk managers" per se. Section 1.1 mentions "ecological risk assessment",
"risk assessors" ,"risk assessments", "risk analysis and characterization", "potential risks" and
"risks to assessment endpoints" ~ so who or what are "risk managers" - project engineers,
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regulatory authorities, actuaries, industry funding entities, indigenous people living in the
watershed?
EPA FINAL RESPONSE: The assessment does not identify or define risk managers, because it
does not address a specific regulatory action with an identifiable risk manager.
WEBER SCANNELL RESPONSE: This reviewer is satisfied that the initial comments have
been addressed by Section 1.2.
EPA FINAL RESPONSE: No response required.
Explain why the scope for human and wildlife impacts was limited to fish-mediated effects, as well
as why fish-mediated effects on humans were limited to Alaska Native cultures. Reviewing effects
beyond fish-mediated ones (e.g., potential for complete loss of the subsistence way of life) would
improve the assessment.
EPA RESPONSE: The scope of the assessment has been clarified throughout the document,
particularly in Chapters 1 and 2. Throughout the assessment we acknowledge that direct effects of
large-scale mining on wildlife and Alaska Native cultures may be significant, but that these direct
effects are outside the scope of the current assessment.
ATKINS RESPONSE: This response is adequate.
EPA FINAL RESPONSE: No response required.
BUCKLEY RESPONSE: The scope of the assessment is outlined in the Executive Summary
and explains which potential impacts are considered and which are not and why.
EPA FINAL RESPONSE: No response required.
CAROTHERS RESPONSE: Overall, the scope of the assessment has been more clearly
articulated. Figure 2.1 is helpful to convey the focus points of this assessment, as well as
other important impacts and groups that fall outside of this scope. The Revised Assessment
explains why the scope for human impacts was limited to fish-mediated effects; however, the
EPA Response also notes the prevalence of direct human impacts discussed in public
comment of the May 2012 draft watershed assessment. These public comments, in addition
to peer review comments, prompted an expanded discussion of direct impacts of mining on
people in the Revised Assessment, particularly in Chapter 12. Given the narrow focus of the
majority of the assessment on fish-mediated human impacts, the important addition of a
discussion of direct effects in Chapter 12 could be more clearly contained in a separate
section to avoid confusion. The section should also be prefaced with the clarification that it
is a partial review of direct effects that have been identified in previous case studies, rather
than a review, summary, or study of all possible impacts.
The Revised Assessment also clarifies the focus on Alaska Native cultures in at least two
places:
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"Fish-mediated effects on Alaska Natives were considered because
sustainability of the region's fish populations is critical to the future of
Alaska Natives in Bristol Bay, and because concern about the region's
fishery resources prompted original requests from Alaska Natives that
USEPA examine issues in the Bristol Bay watershed" (1-3)
"Although Alaska Natives are not the only people that would potentially
be affected by mining in the region, Endpoint 3 focuses on Alaska Native
populations because of the centrality of salmon and other salmon-
dependent resources to their way of life and well-being, and because this
assessment was initiated in response to requests from federally recognized
tribal governments to restrict large-scale mining the watersheds" (5-2)
Both of these statements indicate that the assessment focuses primarily on Alaska Natives in
the region for two reasons: 1) the centrality of salmon to the indigenous cultures of the
region, and 2) the original request for the assessment came from Alaska Natives and
federally-recognized tribal governments. It would helpful to also clarify if the EPA had
special obligation to conduct this review given the government-to-government relationship of
these tribes with the federal government. The addition of this second point (that Alaska
Native cultures are considered an endpoint in this assessment in part because tribal
governments asked for the assessment to be conducted) should also be added to the Executive
Summary. As written, the Executive Summary's discussion of scope (ES-2) discusses wildlife
and Alaska Native cultures together as endpoints given their dependence on salmon. As
discussed in the first peer review process, this grouping is awkward and potentially offensive.
Sections that link discussion of these two endpoints (e.g., Section 13.4.2) should be divided
into separate sections.
EPA FINAL RESPONSE: In the final assessment we have moved the discussion of direct effects
on Alaska Native cultures in Chapter 12 to Box 12-1 to clarify that potential direct effects are only
mentioned and not evaluated, are separate from salmon-mediated effects, and are not the focus of
the assessment.
In Chapter 5, we have added text to Section 5.4 that clarifies EPA's responsibility to work with
federally recognized tribes on a government-to-government basis.
In the Executive Summary, we have separated the secondary endpoints in the "Scope of the
Assessment" section, recognizing that the wildlife and Alaska Native culture endpoints are
separate and different. There is a separate section for each secondary endpoint in the Executive
Summary.
DAUBLE RESPONSE: I am comfortable with revisions made to describe the scope of the
assessment. As far as potential effects to Alaska Native cultures, it's my opinion that fish-
mediated impacts should be the focus. Further, risk of large-scale mining activities to their
subsistence lifestyle is covered as well as it can be at this point in time.
EPA FINAL RESPONSE: No response required.
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SLAUGHTER RESPONSE: Despite the primary focus of the Assessment on salmonids, the
authors have done a creditable job of identifying probable (actually, inevitable and
irreversible) consequences for Alaska Native culture of a PLP-style mineral extraction project
in the Bristol Bay watershed. Similarly, consequences for wildlife populations are identified.
Both topics received careful attention in appendices to the 2012 draft of the Assessment;
incorporation of materials from those appendices into appropriate sections of this revised
Assessment is commended.
EPA FINAL RESPONSE: No response required.
WEBER SCANNELL RESPONSE: The reviewer understands the limitations of the
Assessment and is satisfied.
EPA FINAL RESPONSE: No response required.
WHITNEY RESPONSE: The revised assessment does a better job of clarifying that direct
effects of mining on wildlife are outside the scope of the current assessment but does not
explain why direct effects on wildlife are outside the scope of work. The concept that wildlife
are not a component of the salmon ecosystem is not addressed. If wildlife are thought not to be
a component of the salmon ecosystem, the assessment should explain why this is the case.
EPA FINAL RESPONSE: We do not state and do not believe that wildlife are not part of the
salmon ecosystem. The assessment addresses salmon-mediated risks to wildlife, but direct effects
ofpotential mining on wildlife are outside the scope of the assessment. Given the economic,
ecological, and cultural importance of the region's key salmonids, and stakeholder and public
concern that a mine could affect those species, the primary focus of the assessment is the
abundance, productivity, and diversity of these fishes. Wildlife and Alaska Native cultures are also
considered as endpoints, but only as they are affected by changes in salmonidfisheries.
Be more consistent throughout the document in terms of the level of detail provided for the different
scenarios and stressors. For example, the document has devoted 36 pages to the discussion of
catastrophic Tailings Storage Facility (TSF) failure, while sections on the pipeline, water treatment,
and road/culvert failures are brief. Indeed, the long discussion on the TSF failure belies a certainty
and understanding of dam failure dynamics that is inaccurate.
EPA RESPONSE: The revised assessment includes more failure scenarios (e.g., diesel pipeline
failure, wastewater treatment plant failure, and refined seepage scenarios) in Chapter 8. It also
explains why these specific failure scenarios were chosen, and discusses these scenarios in greater
detail than the previous draft (i.e., to more closely match the level of detail originally provided only
for the TSFfailure scenario). Also see detailed responses to comments on Charge Question 5.
ATKINS RESPONSE: This response is adequate.
EPA FINAL RESPONSE: No response required.
BUCKLEY RESPONSE: The inclusion of additional system failure scenarios does indeed more
closely match the level of detail of the TSF failure scenario. However, the level of detail does
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still seem to imply a certainty and understanding of the impacts of a tailings dam failure which
are simply beyond the scope of the assessment.
EPA FINAL RESPONSE: To evaluate the assessment scenarios, we nuist assign specific values to
different parameters. We have bounded these values where possible to present a range ofpossible
outcomes, and uncertainties in all of the analyses are clearly acknowledged throughout the
assessment.
DAUBLE RESPONSE: The Revised Draft Assessment is now a more balanced document in
terms of level of detail for individual failure scenarios. I believe the amount of text devoted to
each failure scenario is appropriate for the level of perceived risk and for the amount of
information available.
EPA FINAL RESPONSE: No response required.
SLAUGHTER RESPONSE: The more detailed and expanded treatment in Chapters 7, 8, 9,10
and 11 of the revised Assessment is greatly appreciated. The new Assessment gives more
balanced and appropriate consideration to potential failure scenarios which are in many ways
at least in equal importance with potential TSF failure.
EPA FINAL RESPONSE: No response required.
WEBER SCANNELL RESPONSE: As discussed under Peer review Question 5, the additional
information on other failures is an important component of the revised Assessment. I note that
failures also are discussed in Appendix 1.1 also commend EPA for including references to
possible long-term management of the site.
EPA FINAL RESPONSE: No response required.
Technical Content
Mine Scenario
Consider the document to be a screening-level assessment of all potential stressors. Focusing on
failure mode overemphasizes catastrophic events (e.g., TSF failing), rather than considering all
potential stressors, such as holding mine owners strictly accountable for their day-to-day activities
with regard to best practices.
EPA RESPONSE: Additional information on the purpose and scope of the assessment has been
added to Chapters 1 and 2. A screening of all potential stressors, including individual chemicals, is
presented in Section 6.4.2. Also see detailed responses to Charge Question 2 on the use of "best
practices" and responses to Charge Question 5 on failure scenarios.
ATKINS RESPONSE: This response is adequate.
EPA FINAL RESPONSE: No response required.
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BUCKLEY RESPONSE: There still seems to be room for improvement on the organization of
the assessment in trying to identify the potential stressors from catastrophic events versus
normal operations. Chapters 7-11 are better organized and help to outline these various system
failure scenarios.
EPA FINAL RESPONSE: We believe that the reorganization of the April 2013 draft assessment
accomplishes this; however, we have added clarification that effects of both catastrophic failures
and normal operations are evaluated in the assessment in Chapter 1.
DAUBLE RESPONSE: While it may appear the document focused on failure mode, these are
the types of events of primary concern. Thus, they require more discussion in terms of both
potential effects and uncertainty. One suggestion is to add a statement early in both the
Executive Summary and Introduction that states something like "This document includes an
assessment of potential failure scenarios, as well as effects that may occur during day-to-day
operations of a large-scale mine."
EPA FINAL RESPONSE: This clarification has been added to Chapter 1.
SLAUGHTER RESPONSE: The greater detail and much more comprehensive in-depth
analysis in Chapter 6 and in the subsequent topic-specific chapters greatly enhance the utility
and credibility of the Assessment.
EPA FINAL RESPONSE: No response required.
WEBER SCANNELL RESPONSE: The additional information that was included in the
revised assessment satisfies my concerns that were stated in the initial comment. I am especially
pleased that the revised Assessment includes discussions of ions other than copper and of
chemicals typically used in this type of mining.
EPA FINAL RESPONSE: No response required.
Reexamine the document's use of historical data and case studies to describe and estimate the risk of
failure for certain mine facilities (including the TSF, pipeline, water treatment, etc.), as these
examples from extant mines may not be an appropriate analog for a new mine in the Bristol Bay
watershed.
EPA RESPONSE: The TSFfailure range was, and still is, based on design goals, not the
historical data. The historical TSFfailure data are provided as background. The pipeline failure
rates are based on the most relevant historical data from the petroleum industry. They are directly
relevant to the dieselpipeline, and experiences at the Alumbrera mine (described in the previous
draft) and the Antamina and Bingham Canyon mines (added to this draft) suggest that they also
are relevant to the product concentrate pipeline. Water treatment failure rates were not quantified.
However, recent reviews cited in the revised draft indicate that water collection and treatment
failures have been reported at nearly all analogous mines in the U.S. The estimation of culvert
failure frequencies has been revised and is now based on only recent literature (2002 and later).
We believe that these estimates are appropriate.
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ATKINS RESPONSE: This response is adequate.
EPA FINAL RESPONSE: No response required.
BUCKLEY RESPONSE: Culvert failure frequency based primarily on large woody debris
loading in forest streams is probably not appropriate information to accurately estimate failure
frequency along the transportation corridor. Ice and floods would probably have more impacts
on stream crossings. There is not much discussion of other crossing methods other than bridges
which might reduce the impacts of stream crossings on fish in Box 10.2 Culvert Mitigation.
EPA FINAL RESPONSE: As noted in Section 10.3.2.3 of the final assessment, the cited culvert
failure frequencies are from modern roads, are not restricted to forest roads, and represent the
most relevant data available. It is also noted in this section that forested streams inevitably carry
more woody debris that could block culverts, andforested vegetation types represent 68% of the
potential transportation corridor area.
Box 10-2 summarizes the design approaches in the 2001 Memorandum of Agreement between the
Alaska Department of Fish and Game and the Alaska Department of Transportation and Public
Facilities (ADOT) that help to ensure culverts are designed and installed to provide efficient fish
passage. Box 10-2 also calls attention to ADOT's standard design criteria presented in the Alaska
Highway Drainage Manual. Additional mitigation measures are discussed in Box 10-3.
DAUBLE RESPONSE: I was impressed with how much new literature was added to the
Revised Draft, particularly with the number of relevant examples from mining and other
industry. I found the use of "box text" to highlight specific examples to be very informative.
EPA FINAL RESPONSE: No response required.
SLAUGHTER RESPONSE: RE pipeline failures, the revised Assessment does reference both
the 2012 Ft. Knox AK incident, and the 2010 Kalamazoo MI (Enbridge Energy) pipeline failure
(p. 11-6). The Alumbrera, Antamina, and Bingham Canyon incidents discussed on pp. 11-14 to
11-16 are instructive, as they are considered modern, current-practice mines. The detailed
analyses of hypothetical Knutson and Chinkelyes creeks spills are well thought out and helpful.
The analysis of possible waste-water treatment facility failure in Chapter 8 is useful, as is the
discussion of the Fraser River as an (inappropriate) analogue for Bristol Bay waterways. The
culvert discussions in Chapter 10 are appropriately expanded in comparison with the 2012
draft Assessment.
EPA FINAL RESPONSE: No response required.
WEBER SCANNELL RESPONSE: The discussion of pipeline failures in the revised
Assessment also includes failures from human error. The revised Assessment contains more
comprehensive discussions of different failures. I am satisfied that the revisions have addressed
the initial comment.
EPA FINAL RESPONSE: No response required.
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Expand the discussion on the use of "best" management practices, as the document states that the
mine scenario employs "good," but not necessarily "best" practice. For a mine developed in the
Bristol Bay watershed, only "best" practice likely would be appropriate and anything less may not be
permitted. Even so, without a track record of "best" practice (e.g., new technologies), we cannot
assume that technology, by itself without appropriate operational management controls, can always
mitigate risk.
EPA RESPONSE: The term "best management practices" is a term generally applied to specific
measures for managing non-point source runofffrom storm water (40 CFR Part 130.2(m)).
Measures for minimizing and controlling sources ofpollution in other situations often are
referred to as best practices, state of the practice, good practice, conventional, or simply mitigation
measures. We assume that these types of measures would be applied throughout a mine as it is
constructed, operated, closed, and post-closure, and have used the term "conventional modern "
throughout the assessment to refer to these measures. To remove any ambiguity related to the
subjectiveness of terms "good" or "best", we have removed them in the revision and have provided
definitions for relevant terms used in Box 4-1.
ATKINS RESPONSE: This response is adequate.
EPA FINAL RESPONSE: No response required.
BUCKLEY RESPONSE: These changes help reduce confusion about "good" and "best"
management practices.
EPA FINAL RESPONSE: No response required.
DAUBLE RESPONSE: Box 4.1 does an adequate job of resolving this comment. The topic is
further covered in Appendices I and J.
EPA FINAL RESPONSE: No response required.
SLAUGHTER RESPONSE: OK.
EPA FINAL RESPONSE: No response required.
WEBER SCANNELL RESPONSE: I agree with the changes; however, I also note the valuable
information provided in Appendix I. Appendix I includes discussion of different methods for
tailings disposal and the related stabilities, discussions of conventional practices for different
aspects of the mining operation and discussions of "best" practices that could be used (e.g.
selective flotation, page 10 of Appendix I). The information in this Appendix is a valuable
contribution to the Assessment.
EPA FINAL RESPONSE: No response required.
Adopt a broader range of mine scenarios (not only minimum and maximum) so as to bound potential
impacts, especially at smaller mine sizes (e.g., 50th percentile). Underground mine development,
with its different impacts, also should be considered and included in the assessment.
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EPA RESPONSE: A third mine size scenario (250 million tons) has been added to the assessment,
to represent the worldwide median sized porphyry copper mine (based on Singer et al. 2008).
ATKINS RESPONSE: This response is adequate.
EPA FINAL RESPONSE: No response required.
BUCKLEY RESPONSE: The addition of the .25 hypothetical mine scenario helps bracket the
potential impacts described in the assessment and there is a short discussion about the potential
impacts from large-scale underground mine development.
EPA FINAL RESPONSE: No response required.
DAUBLE RESPONSE: The third scenario is an excellent addition. More important, in my
mind, was comparative data on other mines within the region, for example Table 4.1.
EPA FINAL RESPONSE: No response required.
SLAUGHTER RESPONSE: OK.
EPA FINAL RESPONSE: No response required.
WEBER SCANNELL RESPONSE: The reviewer notes the addition of the 250-million tons
mine scenario and the expanded discussions of other deposits in the region that could possibly
be developed.
EPA FINAL RESPONSE: No response required.
Based on the hypothetical mine scenario, perpetual management of the geotechnical integrity of the
waste rock and tailings storage facilities, as well as perpetual water treatment and monitoring, will
most likely be necessary (i.e., a "walk away" closure scenario after mining ends may not be
possible). Therefore, emphasize how monitoring and management of the geotechnical integrity of
waste rocks and tailing storage facilities should continue "In Perpetuity" (i.e., for at least tens of
thousands of years). Discuss what conditions would need to be met to allow "walk away" closure in
the Bristol Bay environment gaining insight into these observations from mines where perpetual
treatment and monitoring are ongoing (e.g., the Equity Silver Mine in British Columbia).
EPA RESPONSE: The conditions for closure and the potential need for perpetual site
management are discussed in general terms in the revised assessment. The primary condition
assumed to be required is water chemistry that meets all criteria and permit conditions and that is
stable or improving. However, even though there are some facilities with "perpetual treatment"
conditions in place, there is obviously no information about how these facilities perform over very
long periods of time.
ATKINS RESPONSE: This response is adequate.
EPA FINAL RESPONSE: No response required.
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BUCKLEY RESPONSE: The revised assessment clarifies the potential conditions at closure
and some of the water treatment scenarios which could take place.
EPA FINAL RESPONSE: No response required.
DAUBLE RESPONSE: Given my experience with assessments of long-term risk of
contaminants from the Hanford Site in southeastern Washington State, I can understand the
suggestion for 10,000 year or "in perpetuity" scenarios. However, I believe this risk scenario is
difficult if not impossible to describe give the huge range of possibilities for mining
development and potential impacts on the environment. I am comfortable with the general
terms provided in the Assessment.
EPA FINAL RESPONSE: No response required.
SLAUGHTER RESPONSE: The revised Assessment repeatedly acknowledges that there is no
extant precedent for "perpetual" monitoring, facility maintenance, and treatment if required to
maintain either ecosystem function or simply maintain acceptable water quality.
EPA FINAL RESPONSE: No response required.
WEBER SCANNELL RESPONSE: In the response to the initial comments (Charge questions),
I have noted various places in the document where reference to perpetual treatment and a need
for sufficient bonding has been added. My initial concerns were that this issue had not been
adequately highlighted. The revisions to the Assessment satisfy those concerns.
EPA FINAL RESPONSE: No response required.
Identify, in technical detail, how exploratory effects (e.g., drill holes, blasting, overflight, etc.) were
managed. This includes roads, airstrips, helipads, camps, fuel dumps, and ATV trails that have
already been developed or imposed on the watershed, and what "mitigation" already has been
undertaken on those sites. Assess the consequences/impacts of these activities in the Cumulative
Risks section.
EPA RESPONSE: The effects of exploratory activities are outside of the scope of this assessment.
ATKINS RESPONSE: This response is adequate.
EPA FINAL RESPONSE: No response required.
DAUBLE RESPONSE: I disagree, in part. Exploratory activities are one part of mining
development where Stage 1= exploratory, Stage 2=construction, Stage 3=operation, and Stage
4-site closure. The Main document should at least provide a brief description of whether
specific exploratory activities such as drill holes, blasting, roads, airstrips/helipads, camps and
trails fit within or are "superseded" by the overall mine development footprint. I would argue
this description would suffice and that exploratory activities need not be discussed in either a
mitigation or cumulative risk chapter.
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EPA FINAL RESPONSE: A text box discussing exploratory activities has been added to Chapter
2 of the final assessment.
SLAUGHTER RESPONSE: This statement simply acknowledges that this Assessment is not
truly comprehensive. Exploratory activities (e.g., drill holes, blasting, helicopter and fixed-wing
overflights, etc.), including "pioneer" roads or airstrips, helipads, camps, fuel dumps, and
ATV trails that have already been developed or imposed on the watershed, are an inevitable
precursor to project implementation and "pave the way" for the project(s). Such activities are
thus an integral component of a project such as the potential Pebble mining development, and
clearly are directly relevant to this Assessment. I recall hearing reference to such ongoing
activities in public testimony during the 2012 Anchorage meeting, and anecdotal evidence is
available from many sources, such as Carter (2012).
EPA FINAL RESPONSE: A text box discussing exploratory activities has been added to Chapter
2 of the final assessment.
WEBER SCANNELL RESPONSE: No additional comments.
WHITNEY RESPONSE: If exploratory activities are outside the scope of the assessment it may
not be possible to conduct a Cumulative Assessment that should address past activities.
EPA FINAL RESPONSE: The assessment is not meant to be a cumulative impact assessment that
considers all human activities currently occurring the region; rather, its purpose is to evaluate
potential effects of one specific activity, large-scale mining.
Risks to Salmonid Fish
Place potential mining impacts in the context of the entire Bristol Bay watershed by emphasizing the
relative magnitude of impacts. For example, of the total salmon habitat, assess the proportion lost due
to mining. Further, reflect on the non-linear nature of the relationship between habitat and salmon
production; 5% of the habitat could be critical and thus responsible for 20% or more of salmon
recruitment. Intrinsic potential, which measures the ability of particular habitats to support fishes,
would lend credibility to this analysis.
EPA RESPONSE: We are unable to build a complete Intrinsic Potential (IP) model, as this would
require validation and more elaborate construction of metrics appropriate to this region. Our
preliminary characterization provides the building blocks for assessing the distribution of key
habitat-forming and constraining features across these watersheds. We now include a
characterization of the major drivers of habitat potential across the watershed and place the mine-
site specific effects in this context (Chapters 3, 7, and 10).
ATKINS RESPONSE: This response is adequate.
EPA FINAL RESPONSE: No response required.
BUCKLEY RESPONSE: The revised assessment does a better job of providing some context to
the potential impacts of the various mine scenarios in Chapter 7.
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EPA FINAL RESPONSE: No response required.
DAUBLE RESPONSE: I noted several significant improvements in relating salmon habitat lost
in terms of its rearing and/or spawning potential. Species distribution and habitat use maps
have been "upgraded" throughout the document to reflect life history attributes in relation to
mining development.
EPA FINAL RESPONSE: No response required.
REEVES RESPONSE: There is no need to build an IP model from scratch. Rather, EPA could
draw from results of studies that have employed the concept. Generally, a small proportion of
the landscape is responsible for a large proportion of the production. See the attached draft of
Bidlack et al., which is in review, on Chinook salmon in the upper Copper River. Simply
stating the amount of miles of stream/habitat that may be affected may not accurately
represent the impact of mine operations.
EPA FINAL RESPONSE: We agree. We reviewed the Copper River IP when beginning this
assessment, and recognize the value of specific applications. Text has been added to Section 7.2
highlighting the value of the coarse-scale characterization in 1) providing insight into differences
in stream valley characteristics across spatial scales, and 2) emphasizing spatial variation in
stream characteristics and potential fish habitat quality and quantity.
SLAUGHTER RESPONSE: This is an appropriate response.
EPA FINAL RESPONSE: No response required.
WEBER SCANNELL RESPONSE: The reviewer notes the additional information provided in
Chapters 3, 7 and 10.
EPA FINAL RESPONSE: No response required.
Include a section on the impact of Global Climate Change with explicit reference to a monitoring
program that will allow scientists, if the mine is built, to distinguish between effects of climate
change and mining effects on the physical and biological components of this ecosystem.
EPA RESPONSE: Climate change projections and potential impacts are now included in Chapter
3, and as important external factors in the risk analyses presented in Chapters 7, 9,10, and 14.
Development of a monitoring program to distinguish between mining and climate change effects is
outside of the scope of the assessment.
ATKINS RESPONSE: This response is adequate.
EPA FINAL RESPONSE: No response required.
BUCKLEY RESPONSE: The revised draft includes several new sections dealing with the
potential role of climate change.
EPA FINAL RESPONSE: No response required.
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DAUBLE RESPONSE: The topic of climate change was extensively and adequately covered
throughout the revised Assessment, both in terms of additive risk and uncertainty. The authors
are to be commended for their careful attention to this complicated topic.
EPA FINAL RESPONSE: No response required.
REEVES RESPONSE: The discussion of the potential impact of climate change in the revised
document is good. I have two additional suggestions. First, changes in temperature are
presented for air temperature only. You should attempt to discuss what this means for water
temperatures. Generally, a two degree change in air temperature translates to a one degree
change in water temperature. Or, at least state that there is not a corresponding one-to-one
degree change in air and water temperature so that the reader is aware of the potential change
in water temperature. Second, I think that it would be good to include Fig. 3 from McCollugh
(1999. EPA-910-R-99-010). This figure shows the relation between changes in water
temperature and time of emergence of fry, which is potential impact of increasing water
temperatures from climate change and the altered water temperatures from mining operations.
EPA FINAL RESPONSE: Figure 3-19, which presents the relationship between temperature and
time from fertilization to emergence, has been added to the final assessment. We have also added
text that discusses the relationship between air temperature and water temperature (Section 3.8).
SLAUGHTER RESPONSE: Incorporation of potential climate change consequences into the
body of the Assessments is appropriate, and the discussions are well-considered and
reasonable.
EPA FINAL RESPONSE: No response required.
VAN ZYL RESPONSE: The author would suggest that the comment about "an explicit
reference to a monitoring program" did not imply that EPA should develop such a plan as part
of the Second Draft. The main insight of this comment is that environmental effects from
potential future mining in Bristol Bay can be related to climate change as well as mining and
that specific monitoring plans should be developed for mining projects in Bristol Bay to allow
clearly distinguishing between these effects. It is recommended that this comment be included
in the final document.
EPA FINAL RESPONSE: This point is made in Box 14-2 of the assessment.
WEBER SCANNELL RESPONSE: The revised Assessment contains different references to
climate change and resulting risks to the aquatic environment. For example, an increase in
precipitation and flooding is discussed on page 7-59 of the revised Assessment. Possible risks
from increased summer temperatures are discussed on page 8-63. The reviewer is satisfied that
the issue of climate change has been integrated into the Assessment.
EPA FINAL RESPONSE: No response required.
Explicitly recognize that the transportation corridor and all associated ancillary development,
including future resource developments made possible by the initial mining project, will necessarily
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and inevitably have impacts (hydrologic, noise, dust, emissions, etc.). These impacts will vary in
duration, intensity, severity, relative importance, spatial dispersion, and inevitably expand
geographically through time with further "development." These impacts should be incorporated into
the Cumulative Risks section.
EPA RESPONSE: The cumulative risk section (Chapter 13) has been expanded to include the
multiple transportation corridors, ancillary mining development and secondary development
associated with multiple mines in a qualitative discussion. The issues addressed in the assessment
of the transportation corridor (Chapter 10) have also been expanded to include chemical spills,
dust, invasive species, and road treatment salts.
ATKINS RESPONSE: This response is adequate.
EPA FINAL RESPONSE: No response required.
BUCKLEY RESPONSE: The reorganization of these chapters provides additional information
on potential impacts from the transportation corridor, and reads more clearly than the initial
assessment.
EPA FINAL RESPONSE: No response required.
DAUBLE RESPONSE: I am comfortable with revisions made on this topic in both the
transportation and cumulative risk chapters.
EPA FINAL RESPONSE: No response required.
SLAUGHTER RESPONSE: The addition of Chapter 10 is greatly appreciated. Chapter 13 is
largely successful in attempting a comprehensive overview of cumulative effects; that chapter
will hopefully not be treated as an "afterword" but rather will be viewed as equally important
as the topic-focused chapters that precede it. Induced and cumulative consequences will be
inevitable upon construction of the initial mine project and transportation corridor, and will be
irreversible for the Bristol Bay watershed, ecosystem, and human population (Alaska Native
and others), let alone effects on salmonids.
EPA FINAL RESPONSE: No response required.
WEBER SCANNELL RESPONSE: The reviewer is satisfied with these changes.
EPA FINAL RESPONSE: No response required.
WHITNEY RESPONSE: The Cumulative Risk Section does not address the impact of
commercial fishing. Merely stating that the commercial fishery is sustainable and closely
monitored does not mean that it has no impact on the salmon ecosystem. I cited Hilborn's (2005
- citation in original comments) opinion that fishing has an impact in my first set of comments
and I commented that commercial fishing reduces the amount of MDN returned to the salmon
ecosystem. Neither of these points are addressed.
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EPA FINAL RESPONSE: The assessment is not meant to be a cumulative impact assessment that
considers all human activities currently occurring in the region; rather, its purpose is to evaluate
potential effects of one specific activity, large-scale mining. We agree that commercial fishing has
an effect, but this effect is not relevant to this assessment.
Incorporate current research findings into stream crossing and culvert-design practices (e.g., arch
culverts, bridges, etc.).
EPA RESPONSE: We describe current culvert design practices in a box titled "Culvert
Mitigation" in Chapter 10.
ATKINS RESPONSE: This response is adequate.
EPA FINAL RESPONSE: No response required.
BUCKLEY RESPONSE: There is not much discussion of other crossing methods other than
bridges which might reduce the impacts of stream crossings on fish in Box 10.2 Culvert
Mitigation.
EPA FINAL RESPONSE: Box 10-2 summarizes the design approaches in the 2001 Memorandum
ofAgreement between the Alaska Department of Fish and Game and the Alaska Department of
Transportation and Public Facilities (ADOT) that help to ensure culverts are designed and
installed to provide efficient fish passage. Box 10-2 also calls attention to ADOT's standard design
criteria presented in the Alaska Highway Drainage Manual. Additional mitigation measures are
discussed in Box 10-3.
DAUBLE RESPONSE: I appreciate that new research findings were incorporated in the
Revised Draft document, primarily in section 10.3.2.3 (which appeared somewhat biased
negatively towards potential magnitude of risks). Given that culvert failure is one risk to fish
populations from development of the transportation corridor, this risk should be specified in
paragraph one of section 10.3 Potential Risks to Fish Habitats and Populations. I would argue
that current culvert design practices are not covered in Box 10.2. Rather, this box (with the
exception of the Tier 1-Stream Simulation Design which is not alluded to in the text) provides
useful detail on regulations associated with culvert design and placement.
EPA FINAL RESPONSE: Culvert failure is one of a number of risks to fish populations from
development of a transportation corridor. The beginning of Section 10.3 addresses the overall
risks of road development in the Bristol Bay region, and there is no need to specifically call out
culvert failure. We disagree that Box 10-2 does not cover current design practices, given that three
design approaches from the 2001 Memorandum of Agreement between the Alaska Department of
Fish and Game and the Alaska Department of Transportation and Public Facilities are
summarized here.
SLAUGHTER RESPONSE: OK.
EPA FINAL RESPONSE: No response required.
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WEBER SCANNELL RESPONSE: The reviewer is satisfied with these changes.
EPA FINAL RESPONSE: No response required.
Recognize in the assessment that risk and impact are not equivalent. Risk may be low, but the
potential impact could be huge (e.g., in the case of a TSF failure).
EPA RESPONSE: Risk has been defined in many ways, even by risk assessors. The conmienter
seems to define risk as probability. To avoid that potential source of confusion, we use the term
"probability" for that concept. Similarly, the conmienter seems to use "impact" where we use
"effect" or "magnitude of effect". We use "risk" to refer to both concepts combined—that is, an
event or effect and its probability.
ATKINS RESPONSE: This response is adequate.
EPA FINAL RESPONSE: No response required.
BUCKLEY RESPONSE: This seems to be a reasonable way to deal with the confusion of
terms.
EPA FINAL RESPONSE: No response required.
DAUBLE RESPONSE: I am comfortable with the terminology and definitions of risk as
provided in the Revised Draft Assessment.
EPA FINAL RESPONSE: No response required.
SLAUGHTER RESPONSE: To repeat my earlier comment: Section 1.2 discusses possible use
of the assessment, but does not identify or define "risk managers" per se. Section 1.1 mentions
"ecological risk assessment", "risk assessors" ,"risk assessments", "risk analysis and
characterization", "potential risks" and "risks to assessment endpoints" ~ so who or what are
"risk managers" - project engineers, regulatory authorities, actuaries, industry funding
entities, indigenous people living in the watershed?
EPA FINAL RESPONSE: The assessment does not identify or define risk managers, because it
does not address a specific regulatory action with an identifiable risk manager.
WEBER SCANNELL RESPONSE: Perhaps including a box with these definitions would be
helpful.
EPA FINAL RESPONSE: We have added a text box that explains failure probabilities in greater
detail (Box 9-3), but believe that definitions of the other terms are fairly straightforward and do
not require a text box.
Recognize and justify chronic behavioral endpoints, such as those potentially affecting survival and
long-term success of fish populations.
EPA RESPONSE: The chronic behavioral effects of copper on salmonids, the primary endpoint of
concern, were described in Chapter 5 and are now described in Chapter 8. Although those effects
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occur at lower levels of copper than conventional survival, growth and reproduction endpoints for
salnionids, they are less sensitive than the conventional endpoints for aquatic invertebrates.
ATKINS RESPONSE: This response is adequate.
EPA FINAL RESPONSE: No response required.
BUCKLEY RESPONSE: The new format treats these issues more clearly.
EPA FINAL RESPONSE: No response required.
DAUBLE RESPONSE: I noted additional text related to behavioral effects in Chapter 8. While
of value in providing for perhaps a greater level of protection, behavior (such as avoidance or
olfactory response) is a much more difficult endpoint to measure and extrapolate to the real
world than endpoints such as survival, growth and reproduction. I am comfortable with the
level of detail provided in the Revised Draft Assessment as it relates to potential behavioral
effects on salmonids.
EPA FINAL RESPONSE: No response required.
SLAUGHTER RESPONSE: The detailed discussion of leachate toxicity and exposure-response
for aquatic organisms, including salmonids, in Chapter 8 was very helpful. The careful
discussion of uncertainties in Chapter 8 (and throughout the revised Assessment) is also
appreciated.
EPA FINAL RESPONSE: No response required.
WEBER SCANNELL RESPONSE: The reviewer is satisfied.
EPA FINAL RESPONSE: No response required.
Wildlife
Recognize that the draft assessment did not account for all levels of ecology, such as the individual
(e.g., a bald eagle nest), population, community, ecosystem, and landscape levels. Fold other levels
of organization into the stressors assessment where appropriate or justify a more limited approach.
EPA RESPONSE: As is appropriate for an ecological risk assessment (as opposed to an
environmental impact assessment), this assessment focuses on a specific, limited set of endpoints
as defined in Chapter 5. We have added text in Chapters 2 and 5 to explain both why these
endpoints were selected, and that responses other than those considered in the assessment, at
multiple levels of ecological organization, are likely but are outside the scope of the assessment.
ATKINS RESPONSE: This response is adequate.
EPA FINAL RESPONSE: No response required.
BUCKLEY RESPONSE: The revision explains the ERA process much better and outlines the
decision to use the given assessment endpoints as well as the limitations of the scope of the
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assessment.
EPA FINAL RESPONSE: No response required.
DAUBLE RESPONSE: I agree that the number of individual endpoints and levels of
organization must be limited in an assessment that covers such a broad geographic area.
EPA FINAL RESPONSE: No response required.
SLAUGHTER RESPONSE: The authors do recognize that the full ecological web of Bristol
Bay and its watershed is the ultimate "receptor" of whatever activities take place. I accept that
a more comprehensive analysis at all levels is "outside the scope of the assessment."
EPA FINAL RESPONSE: No response required.
WEBER SCANNELL RESPONSE: The additional information in Chapters 2 and 5 clarify the
use of different endpoints. The reviewer is satisfied.
EPA FINAL RESPONSE: No response required.
WHITNEY RESPONSE: The revised assessment does a much better job of defining endpoints.
Yet more work needs to be done to define the salmon ecosystem. For example, if multiple levels
of ecological organization, such as "ecosystem" are outside the scope of the assessment as stated
above, EPA should consider changing the current title of the document that focuses the
assessment on "salmon ecosystems".
EPA's assessment discusses a few ecosystem functions and passes over many others. For
example, salmon perform an important ecosystem function by returning MDNs to the
watershed portion of the Bristol Bay ecosystem. I can't help wonder why this ecosystem
function is discussed in detail but is supposedly "outside the scope of the assessment." Wildlife
provide a variety of ecosystem functions in the salmon ecosystems but are judged to be "outside
the scope of the assessment." So it appears that some ecosystem functions such as returning
MDNs are within the scope of work but some aspects of returning the MDN (i.e., movement of
MDN to terrestrial components of the watershed) are outside the scope of work. Are wildlife a
component of the salmon ecosystem or not? If they are not, don't mention wildlife's role in the
MDN processes. I'm not clear where the salmon ecosystem (structure and function) starts and
where it stops in the watersheds.
The assessment title states "...salmon ecosystems of Bristol Bay..." but has not included the
impact of a major predator in the salmon ecosystems, commercial fishing, in Bristol Bay, as
part of the analysis. Not including the impact of commercial fishing in the assessment and not
comparing the impact of commercial fishing to potential impact(s) of the mine appears to side
step a very important issue that should be explicitly addressed in any direct or cumulative
assessment of mining impacts. Would the mine bring an end to commercial fishing in Bristol
Bay? Greatly reduce commercial fishing? Slightly reduce commercial fishing? Or have little or
no effect on commercial fishing? The answer to these questions seem critical to a CWA
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assessment.
EPA FINAL RESPONSE: Wildlife are part of the salmon ecosystem, and are assessed in terms of
fish-mediated effects; as stated in Chapter 2, only direct effects of mining on wildlife are outside
the scope of the assessment. Commercial fishing is outside the scope of the assessment, in terms of
both its impacts on salmon ecosystems and how it would potentially be affected by large-scale
mining.
Discuss in the document fishes other than salmonids. The assessment focuses on risks to sockeye
salmon in the Bristol Bay watershed (and also considers anadromous salmonids, rainbow trout, and
Dolly Varden), but does not account for potential impacts to other members of the resident fish
community. Further, primary and secondary production, including nutrient flux was not addressed.
Expanding the assessment to consider other levels of organization, including direct as well as indirect
effects on wildlife and other fish, would provide additional context in the assessment of mine-related
impacts.
EPA RESPONSE: See response to comment above; we also incorporated additional information
from Appendices A, B, and C into the Chapter 5 text, to provide additional detail on the area's
biota. We chose our endpoints for reasons described in Chapters 2 and 5. Other endpoints,
including indirect effects on fish and wildlife, are now discussed more explicitly, but are generally
considered outside the scope of the assessment.
ATKINS RESPONSE: This response is adequate.
EPA FINAL RESPONSE: No response required.
BUCKLEY RESPONSE: These changes improve the organization of the document and bring
information from some of the Appendices forward into the document.
EPA FINAL RESPONSE: No response required.
DAUBLE RESPONSE: This bullet is actually two separate comments. I am now comfortable
with the amount of information provided in the main document on fishes other than salmonids.
A remaining weakness, however, is lack of discussion of mining leachates on primary
production. While fish are the principal species of concern, the role of algal/periphyton
communities in streams potentially impacted by mining activities should be acknowledged.
Specifically, scouring by sediments and flocculation due to leachates are likely impacts to algal
and invertebrate production that would affect fish populations due to reduced food supply.
EPA FINAL RESPONSE: Toxic effects on primary production are discussed in a new subsection
in Chapter 8. Based on leachate compositions, significant flocculation of metal hydroxides is
judged to be unlikely.
SLAUGHTER RESPONSE: OK ~ The authors do recognize that the full ecological web of
Bristol Bay and its watershed is the ultimate "receptor" of whatever activities take place. Other
fish are mentioned in the draft Assessment. I accept that a more comprehensive analysis at all
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levels is "outside the scope of the assessment."
EPA FINAL RESPONSE: No response required.
WEBER SCANNELL RESPONSE: My initial comments requested that some of the
information in these Appendices be integrated into the main body of the Assessment. I note
that this was done and believe that the expanded discussions in Chapters 2 and 5 address my
initial comments.
EPA FINAL RESPONSE: No response required.
Human Cultures
Use case histories to provide insight and anticipate mining impacts on Alaska Natives (e.g., those
exemplifying the Exxon Valdez oil spill impacts, cumulative effects of oil and gas development in
the North Slope region, and social impacts related to mining development in Alaska).
EPA RESPONSE: Examples from applicable case studies, including the Exxon Valdez oil spill,
are cited in Chapter 12 of the revised assessment.
ATKINS RESPONSE: This response is adequate.
EPA FINAL RESPONSE: No response required.
CAROTHERS RESPONSE: The inclusion of these case studies has strengthened the report.
These case studies provide insights into both fish-mediated effects to cultures and
communities, as well as direct effects from resource exploration and development.
EPA FINAL RESPONSE: No response required.
DAUBLE RESPONSE: The Exxon Valdez oil spill case study, as presented in Chapter 12, is
relevant.
EPA FINAL RESPONSE: No response required.
SLAUGHTER RESPONSE: Section 12.2, while relatively short in relation to the importance of
the issue, does provide an overview of consequences for Alaska Natives, and acknowledges that
those consequences would be long-lasting and effectively irreversible.
EPA FINAL RESPONSE: No response required.
WEBER SCANNELL RESPONSE: Although the area of human cultures is outside my area of
expertise, I note expanded discussions in Chapter 12.
EPA FINAL RESPONSE: No response required.
As noted above (Scope of the Document), clarify why the scope was limited to fish-mediated effects.
The potential direct and indirect impacts for human cultures extend far beyond fish-mediated impacts
(e.g., potential complete loss of the subsistence way of life). The rationale for this narrow focus
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should be fully explained. In addition, a clear explanation should be given for why fish-mediated
human impacts focused only on Alaska Native cultures.
EPA RESPONSE: The assessment focuses on a specific, limited set of enclpoints as defined in
Chapter 5. We have added text to explain both why these endpoints were selected, and that
responses other than those considered in the assessment are likely but are outside the scope of the
assessment. The assessment was expanded (Chapters 5 and 12) to acknowledge that there are a
wide range of potential direct and indirect impacts to indigenous culture, but they are outside of
the scope of this assessment. The discussion ofpotential effects to indigenous cultures was
expanded to explain that a loss of subsistence resources would extend beyond a loss offood
resources to social, cultural, and spiritual disruption. The text has been expanded to acknowledge
the strong cultural ties of many non-Alaska Natives to the region, and potential effects on all
residents from loss of a subsistence way of life. However, the focus of the assessment remains on
effects on indigenous cultures resulting from effects on salmon.
ATKINS RESPONSE: This response is adequate.
EPA FINAL RESPONSE: No response required.
CAROTHERS RESPONSE: See comments above under "Scope of the Document." The
expanded discussion of subsistence and recent research in the region in Chapter 5 has greatly
strengthened the assessment. The revisions of the language in the Revised Assessment to
reflect the whole suite of physical, social, cultural, economic, and spiritual aspects of
subsistence have also adequately addressed earlier concerns raised.
EPA FINAL RESPONSE: No response required.
DAUBLE RESPONSE: Chapter 5 outlines (using EPA jargon not necessarily translatable to
the general public, e.g., Section 5.1), how assessment endpoints were selected and how they
relate to Alaska Native cultures. Chapter 5, while emphasizing fish-mediated effects on Alaska
Natives, also includes several graphics and supporting test that relates to recreational fisheries.
EPA FINAL RESPONSE: No response required.
SLAUGHTER RESPONSE: OK - Chapters 12 and 13 do address the broader direct and
indirect effects on Bristol Bay watershed residents.
EPA FINAL RESPONSE: No response required.
WEBER SCANNELL RESPONSE: The area of human resources is outside my area of
expertise; I have no further comment.
EPA FINAL RESPONSE: No response required.
Water Balance/Hydrology
Better characterize water resources and assess the potential effect of mine development on these
resources by (1) generating a diagram similar to the conceptual models beginning on page 3-7 to
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illustrate the potential effects of mine construction and operation on surface- and ground-water
hydrology; (2) developing a quantitative water balance and identifying water gains and losses; (3)
identifying seasonality of hydrologic processes, including frozen soils and their associated values
(e.g., mm/yr) for each component of the water balance; (4) incorporating these processes into a
landscape characterization; (5) evaluating how global climate change will influence these hydrologic
processes and rates; and 6) using this characterization to demonstrate the expected hydrologic
modification associated with the mine scenarios and infrastructure development.
EPA RESPONSE: The original Figure 4-9 (Figure 6-5 in the revised assessment) has been revised
to more clearly show water management in the assessment's mine scenarios. In addition, three
schematics illustrating water flows under each of the mine size scenarios (Figures 6-8 through 6-
10) have been added to Chapter 6, as have quantitative water balances for each mine size
scenarios. A qualitative discussion of climate change is included in Chapters 3 (Section 3.8) and
14 (Box 14-2).
ATKINS RESPONSE: This response is adequate.
EPA FINAL RESPONSE: No response required.
BUCKLEY RESPONSE: It seems that some additional explanation of the water balance
results would be appropriate. Perhaps an additional diagram which is somewhere between the
simplified cartoon in Figure 6.5 and the detailed Tables such as 6.8 would help the reader
visualize the results of the water balance model.
EPA FINAL RESPONSE: We believe that combination of Figures 6-5, 6-8 through 6-10, and the
detailed values presented in Tables 6-3 and 6-8 provide adequate explanation of the water balance.
Although it may be possible to add the detailed values from Tables 6-3 and 6-8 onto the figures, we
believe this would make the figures too complicated.
DAUBLE RESPONSE: Figure 6.5 is an excellent general schematic of water management and
water balance processes for the mine scenarios. Figures 6.8-6.11 are quite helpful in
understanding local processes related to groundwater and surface water movement. The
summary of water balance flows in Table 6.3 provides additional specific detail. Overall, the
discussion of water balance/hydrology is much improved.
EPA FINAL RESPONSE: No response required.
SLAUGHTER RESPONSE: The much more comprehensive hydrologic analyses of the revised
Assessment are welcome. These allow more detailed consideration of the hydrologic aspects of
the various mine scenarios presented. While there can still remain questions (not detailed in
this review) about the many necessary assumptions involved in those analyses, they do appear
realistic and point out the significant consequences of alternative scenarios.
EPA FINAL RESPONSE: No response required.
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WEBER SCANNELL RESPONSE: The revisions to the draft Assessment help clarify the
water management issues. This reviewer is pleased that water flows are shown for each mine
scenario.
EPA FINAL RESPONSE: No response required.
Demonstrate the interconnectedness of groundwater, surface water, hyporheic zone, and its
importance to fish habitat. Address how interconnectedness changes over time - seasonally, and with
varying weather (e.g., wet vs. dry summers or years, and over the long term as climate changes).
EPA RESPONSE: We lack the data to demonstrate this interconnectedness in a spatially and
temporally uniform manner, but do include examples of known points of high connectivity
(Chapter 7) and qualitatively discuss the potential role of climate change (Chapter 3).
ATKINS RESPONSE: This response is adequate.
EPA FINAL RESPONSE: No response required.
BUCKLEY RESPONSE: Figure 7.14 helps provide some additional information on surface
and groundwater interconnectivity and fish habitat. Given the numerous locations where the
document mentions these features as being critical to the understanding of the watersheds it
seems that a more detailed treatment of these factors is warranted.
EPA FINAL RESPONSE: Figure 7-14 came from a report (Wobus et al. 2012) that was
coauthored by Dr. Ann Maest, which had been peer reviewed for EPA by an independent review
panel. Although the peer review supported the use of the information in Wobus et al. (2012), we
have withdrawn this information and citations of Wobus et al. (2012) because accusations of fraud
in another matter against Dr. Maest led to questions concerning the potential for fraud in Wobus
et al. (2012). This report was used only to support our analyses, and its removal has not changed
the assessment's findings.
A more detailed look at surface water-groundwater connectivity will be essential for any further
action (e.g., mine permitting).
DAUBLE RESPONSE: Simply acknowledging that these interconnections exist and their
relative importance to fish habitat such as spawning and rearing satisfies this reviewer.
EPA FINAL RESPONSE: No response required.
SLAUGHTER RESPONSE: Given the lack of site-specific hard data, the revised Assessment
does fairly acknowledge the importance of surface water/groundwater interactions.
EPA FINAL RESPONSE: No response required.
WEBER SCANNELL RESPONSE: Section 7.3.2.1 of the revised Assessment (page 7-51)
discusses the complex groundwater-surface water connectivity in the deposit area and the lack
of information to describe linkages and possible changes with mine development. This chapter
also discusses using the sustainability boundary approach (page 7-51). I believe the initial
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comment was written, in part, to request that the Assessment recognize the importance of these
interconnected systems. The discussion of the sustainability boundary approach includes
possible risks to aquatic habitats. I recognize the paucity of information to model these linkages
and believe the general discussion presented in this section of the Assessment addresses the
initial comment.
EPA FINAL RESPONSE: No response required.
Provide information on all rivers, including ephemeral and intermittent streams, and first-order to
main-stem streams that could be potentially influenced by the proposed mine, its ancillary facilities,
and the transportation corridor.
EPA RESPONSE: Due to lack of consistent coverage, we rely on the NHD hydrography layer in
this analysis, and can only address ephemeral and intermittent streams qualitatively (Chapter 7).
ATKINS RESPONSE: This response is adequate.
EPA FINAL RESPONSE: No response required.
BUCKLEY RESPONSE: Use of the NHD layer seems appropriate at this level of assessment.
Hopefully more detailed information on stream character and location will be developed in the
future.
EPA FINAL RESPONSE: No response required.
DAUBLE RESPONSE: I found the amount of detail provided on the stream network to be
sufficient given the limitation of comprehensive stream survey and other hydrographic data.
EPA FINAL RESPONSE: No response required.
REEVES RESPONSE: Highlight more prominently in the document (Ch. 7) the fact that the
NHD layer does not accurately represent smaller streams, which may be important
ecologically, and the consequences of this to the analysis.
EPA FINAL RESPONSE: Box 7-1 describes the inadequacy of the National Hydrography Dataset
(NHD) and the National Wetlands Inventory (NWI) data layers for capturing features with
potentially important ecological functions. Enhanced discussion of the importance of headwater
streams and wetlands is included in Chapter 7 in the final assessment.
SLAUGHTER RESPONSE: The NHD data are necessarily broad-brush; I recognize that on-
the-ground work would be required to adequately understand finer-scale hydrologic issues
including ephemeral and intermittent streamflow. Nevertheless, such "small" features can be
significant in streamflow generation, in transport of nutrients or contaminants, and in
immediate sensitivity to perturbation, be that human-caused, seasonal weather, or climate
change. Simply glancing at the streams and landscapes shown in figures 3-8 and 3-11 allows
one to visualize the finer-grain flowpaths which cannot be discerned at the scale of those photos
or the accompanying maps.
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EPA FINAL RESPONSE: A broader discussion of the potential importance of headwater streams
to downstream waters in included in Chapter 7. Revised figures in Chapter 7 also provide a clearer
presentation of headwater stream and wetland loss under the mine footprints.
WEBER SCANNELL RESPONSE: This comment highlights the need for on-the-ground
surveys of potentially affected areas should mine development proceed. The need for more
information was discussed in various sections of the revised Assessment.
EPA FINAL RESPONSE: No response required.
Emphasize the importance of a thorough characterization of the leaching potential of acid-generating
and non-acid generating waste rock and tailings, given the low buffering capacity and mineral
content in the streams and wetlands that could receive runoff and treated water from the proposed
mine. Recognize that collection and treatment of runoff and leachate generated will be critical to
maintain baseline water chemistry in these streams and wetlands.
EPA RESPONSE: We agree that these are important issues, and the discussion of leachate from
waste rocks and tailings has been expanded in the revised assessment (Chapter 8).
ATKINS RESPONSE: This response is adequate.
EPA FINAL RESPONSE: No response required.
BUCKLEY RESPONSE: Chapter 8 is better organized, however it seems that some additional
diagrams would help the reader visualize the information contained in the Tables 8.1 to 8.3 i.e.
where and what does this information potentially impact.
EPA FINAL RESPONSE: The information is available to the reader in the tables and the reaches
are mapped in Figures 7-14 through 7-16.
DAUBLE RESPONSE: I appreciate that issues associated with water collection, treatment and
discharge are now discussed separately in Chapter 8. Although failure of the tailings dam
would be catastrophic, the likelihood of such an event is much lower than those impacts
occurring from normal operations. Consequently, the expanded discussion of impacts of
leachates from all possible sources is relevant.
EPA FINAL RESPONSE: No response required.
SLAUGHTER RESPONSE: Leachates are extensively considered in the revised Assessment.
EPA FINAL RESPONSE: No response required.
WEBER SCANNELL RESPONSE: The reviewer is satisfied with the additional information.
EPA FINAL RESPONSE: No response required.
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Geochemistry/Metals
Reference the most current geochemistry data on potentially acid-generating, non-acid generating,
and metal leaching so as to describe any potential effects of seepage and changes to surface- and
ground-water quality via non-catastrophic failure.
EPA RESPONSE: We used the geochemistry data in PLP's Environmental Baseline Document,
as summarized by the USGS in Appendix H. The effects of seepage on water quality are analyzed
in Chapter 8 of the revised assessment.
ATKINS RESPONSE: This response is adequate.
EPA FINAL RESPONSE: No response required.
DAUBLE RESPONSE: These changes are noted and appropriate.
EPA FINAL RESPONSE: No response required.
SLAUGHTER RESPONSE: OK.
EPA FINAL RESPONSE: No response required.
WEBER SCANNELL RESPONSE: No further comment.
EPA FINAL RESPONSE: No response required.
Explain how contaminants/metals were selected (and others ignored) by EPA as causes for concern.
Information should be included on additional metals and their toxicity so as to assess impacts of
potential leachates. The Pebble Limited Partnership baseline document presented additional metals
that might be useful to include in the assessment.
EPA RESPONSE: The revised assessment describes the selection of contaminants and other
stressors of concern in Section 6.4.2. Additional metals, process chemicals and dissolved solids are
now included.
ATKINS RESPONSE: This response is adequate.
EPA FINAL RESPONSE: No response required.
DAUBLE RESPONSE: Agreed that other contaminants of concern are now mentioned. But,
why was section 6.4 Conceptual Models placed in Chapter 6 Mine Scenarios? While I agree it
might serve as a transition or setup to the risk assessment chapters that follow, it is too
important to be included as a add-on to Chapter 6.1 think this section (which is mostly
methodology) should either be moved to the end of Chapter 5 Endpoints or made a separate
chapter. This change would only require slight re-wording of text in the paragraph on p. 6-36
that begins with "In this section...."
EPA FINAL RESPONSE: As the commenter acknowledges, we believe the conceptual models
provide a good transition between the problem formulation and risk analysis and characterization
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sections of the assessment. We also believe that it is appropriate to consider the conceptual model
diagrams after the specific mine scenarios have been introduced in Chapter 6, as this informs the
source-to-stressor portions of the diagrams.
SLAUGHTER RESPONSE: To me (lacking expertise in this field) the consideration of
contaminants and stressors in the revised Assessment appears comprehensive and competent.
EPA FINAL RESPONSE: No response required.
WEBER SCANNELL RESPONSE: The additional discussion of other elements, process
chemicals and dissolved solids addresses the initial comment.
EPA FINAL RESPONSE: No response required.
Mitigation Measures
Incorporate the critical mitigation information from Appendix I into the main report's mine
scenarios. Include standard mitigation measures that could provide insight into how well they might
work in this context. If this information is not included in the main report, then justify its absence.
EPA RESPONSE: Mitigation measures incorporated into design and operation to minimize
potential impacts were included in the assessment, as were some reclamation measures for
closure; these measures are made clearer in the revised assessment. These mitigation measures
were a sub-set of those presented in Appendix I. The assessment assumes that measures chosen for
the scenarios would be effective. Mitigation to compensate for effects on aquatic resources that
cannot be avoided or minimized by mine design and operation would be addressed through a
regulatory process that is beyond the scope of this assessment. Nevertheless, in response to public
and peer comments we have included a discussion of compensatory mitigation in Appendix J of
the revised assessment.
ATKINS RESPONSE: This response is adequate.
EPA FINAL RESPONSE: No response required.
BUCKLEY RESPONSE: The addition of the information in Appendix J helps to explain where
and when mitigation might enter into the regulatory process.
EPA FINAL RESPONSE: No response required.
DAUBLE RESPONSE: Appendix I lacks a summary or conclusion section, otherwise it reads
well. Appendix J provides a good description of regulatory requirements and methodology.
Considerations and potential mitigation measures were carefully and clearly described. The
opportunities for mitigation (against the regulatory backdrop) were summarized within the
watershed and challenges outlined. One suggestion is to strengthen the last statement within
the Conclusion section. Revise to perhaps something more along the lines of "No viable
alternatives could be identified to address impacts of this type and magnitude."
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EPA FINAL RESPONSE: We have added the following statement to the start of the Conclusions
section of Appendix J: "There are significant challenges regarding the potential efficacy,
applicability and sustainability of compensation measures proposed by commenters for use in the
Bristol Bay region, raising questions as to whether sufficient compensation measures exist that
could address impacts of the type and magnitude described in the Bristol Bay Assessment."
SLAUGHTER RESPONSE: The mitigation measures discussed in Appendix I are, as stated,
"conventional". Despite the statement above that "The assessment assumes that measures
chosen for the scenarios would be effective", after again reviewing Appendix I it seems to me
that there is large uncertainty that all those measures would be effective in actual practice in
the Bristol Bay watershed environment. Many of the measures discussed in Appendix I are
generalities - i.e., Sections 1.1,3.1, 5.0, 7.1, 8.1, 9.1 ~ with questionable applicability to a
potential Pebble project.
EPA FINAL RESPONSE: As stated in Appendix I (introductory section and Section 1.1), the
selection of mitigation measures is site-specific and depends on many factors. Appendix I presents
a number of mitigation methods for various waste streams that are used in current mining
practices, and it purposely presents these in a general sense. It is not meant to suggest that all
mitigation methods presented in Appendix I be used in the assessment scenarios, but rather that
the methods chosen for the scenarios represent a subset of the many options that exist, when
taking into account site-specific factors. Additionally, a number of the mitigation methods chosen
for the scenarios were presented in Gliaffari et al. (2011) as being "permittable" for the Pebble
deposit location.
WEBER SCANNELL RESPONSE: The revised Assessment now includes more information on
mitigation measures; the revised Appendix I is a valuable addition to the Assessment. The
reviewer is satisfied with these changes.
EPA FINAL RESPONSE: No response required.
WHITNEY RESPONSE: Any discussion of CWA Section 404 should at least mention "No Net
Loss" and the likelihood that No Net Loss could be achieved. The top of page 12 of Appendix J
implies that No Net Loss cannot be achieved within the salmon ecosystems of Bristol Bay. If
this is the case, it should be clearly stated.
I am pleased that Appendix J discounts the proposal to remove beaver dams.
The EPA response to the (rhetorical) suggestion for discussion of the concept that commercial
fishing could be reduced as a mitigation measure (Appendix J Section 3.3.2.6) seems to assume
that commercial fishing is not at all related to or concerned with the potential impact(s) of the
mine. I, on the other hand, consider commercial fishing to be an important component of the
salmon ecosystem of Bristol Bay. EPA's broad jump in logic from Hilborn's paleontological
analysis to the conclusion of no opportunity for mitigation is VERY wide and appears to
obfuscate Hilborn's (2005) statements that fishing, as most human activities, has a negative
impact on biodiversity. As stated above and below, the revised assessment would be improved
by addressing commercial fishing for several reasons:
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1. A cumulative impact analysis should consider past impacts and commercial fishing
has had a past impact on the salmon ecosystem.
2. Some commercial fishermen are likely native Americans and a reduction in the
commercial take could be a fish mediated impact.
3. Commercial fishing has definitely reduced the number of fish returning to spawn
and returning MDNs to the ecosystem.
4. The assessment certainly addresses the positive importance of MDNs to the salmon
ecosystem. If it addresses the positive importance, it should also address the negative
importance of the past loss of MDNs due to the commercial take.
I was hoping to see some analysis of using diversion ditches as opportunities to mitigate for
both wetland and riparian impacts. What I saw was a general statement that spawning
channels are not good mitigation. I realize that some mitigation measures are not successful but
my experience is that with proper engineering and biological success criteria plus a good
monitoring program it is possible to achieve effective wetland, riparian and fish mitigation. A
good example is the Weyerhaeuser Headquarters Landfill in Washington where Interfluve
Consultants created good habitat for cutthroat trout out of a run-on-diversion channel around
the landfill footprint. There are many more examples of effective fish mitigation in created
channels that a brief conversation with Interfluve (Hood River, Oregon) could provide.
EPA FINAL RESPONSE: Conclusions regarding the potential efficacy, applicability, and
sustainability of proposed compensation measures have been clarified in Appendix J. Reducing
commercial fishery harvests to compensate for fish losses due to large-scale mining is not
consistent with the definition of compensatory mitigation (40 CFR 230.92). Thus, we have deleted
the discussion of this measure from the revised Appendix J. Section 3.4 of revised Appendix J
references measures that were proposed by commenters but are not consistent with the definition
of compensatory mitigation and are therefore not discussed further. Reference to the suggestion to
reduce commercial fishery harvests has been added to this section, but no further discussion is
necessary. Appendix J has also been expanded to include more detailed discussion of the potential
efficacy, applicability, and sustainability ofpotential measures proposed to expand habitat
connectivity, quality, and quantity as recommended (see Sections 3.3.1.1 - 3.3.1.3 of revised
Appendix J).
Emphasize mitigation measures (e.g., minimization, compensation, reclamation) in the main report,
as they ultimately influence the range of mining impacts and consider time frames of mitigation or
reclamation measures (e.g., immediate response, long-term reclamation).
EPA RESPONSE: See response to previous comment. Mitigation measures are discussed at
greater length in the revised assessment report (e.g., Chapter 4 and Appendix J).
ATKINS RESPONSE: This response is adequate.
EPA FINAL RESPONSE: No response required.
BUCKLEY RESPONSE: The addition of the information in Appendix J helps to explain where
and when mitigation might enter into the regulatory process.
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EPA FINAL RESPONSE: No response required.
DAUBLE RESPONSE: The discussion of mitigation measures in Chapter 4 and Appendices I
and J seems adequate.
EPA FINAL RESPONSE: No response required.
SLAUGHTER RESPONSE: See previous comment. Appendix J (to my reading) strongly
indicates that compensatory mitigation is essentially inapplicable to the Bristol Bay watershed.
EPA FINAL RESPONSE: Based on our review, we conclude that "[t]here are significant
challenges regarding the potential efficacy, applicability and sustainability of compensation
measures proposed by commenters for use in the Bristol Bay region, raising questions as to
whether sufficient compensation measures exist that could address impacts of the type and
magnitude described in the Bristol Bay Assessment."
WEBER SCANNELL RESPONSE: The reviewer is satisfied. Further note: Appendix J
presents a realistic summary of possible mitigation measures and their value in the subject
area.
EPA FINAL RESPONSE: No response required.
Uncertainties and Limitations
Clarify the uncertainty vs. certainty in Chapter 8 by (1) defining levels of uncertainty and (2)
assessing the certainty of some mine impacts. Discuss data limitations in the context of uncertainty.
EPA RESPONSE: The individual analysis chapters and the revised Integrated Risk
Characterization (Chapter 14) discuss certainties and data limitations to a greater extent, as
suggested.
ATKINS RESPONSE: This response is adequate.
EPA FINAL RESPONSE: No response required.
BUCKLEY RESPONSE: This is a much better way to outline the uncertainty and data
limitations.
EPA FINAL RESPONSE: No response required.
DAUBLE RESPONSE: Chapters 8 through 12 each have uncertainty sections. Chapter 7
includes a section on uncertainties and assumptions. The Integrated Risk Assessment (Chapter
14) covers uncertainties and data limitations. Thus, I believe this topic is covered.
EPA FINAL RESPONSE: No response required.
SLAUGHTER RESPONSE: Throughout the revised Assessment, the discussions of "risk
characterization" and "uncertainty" are well-thought-out and useful - for example, Sections
8.2.5, 8.3.3, 8.3.4,10.5.
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EPA FINAL RESPONSE: No response required.
WEBER SCANNELL RESPONSE: The reviewer is satisfied with the changes.
EPA FINAL RESPONSE: No response required.
Articulate early in the document how much uncertainty is acceptable. The assessment provides little
insight with respect to the decisions the document is intended to support.
EPA RESPONSE: Acceptable levels of uncertainty can be defined prior to an assessment if a
decision and a decision maker are identified and if data will be collected by a specified design to
implement a specified model, as described in EPA's Data Quality Objectives process. However,
because this assessment is based on available data and is intended as a background scientific
document rather than a decision document, it is not possible to specify the amount of uncertainty
that is acceptable. Rather, the available data determine the uncertainty and if the assessment is
subsequently used to inform a decision, the decision milker must determine whether the level of
uncertainty is acceptable.
ATKINS RESPONSE: This response is adequate.
EPA FINAL RESPONSE: No response required.
BUCKLEY RESPONSE: The revised draft does a better job in the Executive Summary
identifying the use of the assessment and the uncertainties and limitations of the assessment.
EPA FINAL RESPONSE: No response required.
DAUBLE RESPONSE: I agree with the EPA response.
EPA FINAL RESPONSE: No response required.
SLAUGHTER RESPONSE: Concur with the above response; the various discussions of
uncertainty in the body of the revised Assessment provide a "feel" for the unknown or
unpredictable, without attempting to quantify specific boundaries or levels.
EPA FINAL RESPONSE: No response required.
WEBER SCANNELL RESPONSE: The information presented in the Executive Summary and
Chapter 1 clarifies this. The reviewer accepts that this is an appropriate approach, given the
amount of available data.
EPA FINAL RESPONSE: No response required.
Editorial Suggestions
The title of the document leads one to believe that the assessment addresses the entire Bristol Bay
watershed; rather, the report deals with two major rivers and their watersheds, the Nushagak and
Kvichak. Thus, the title should be changed to reflect the emphasis on these two rivers and their
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watersheds. A possible title may be "An Examination (or identification) of the Potential Impacts of
Mining and Mining Associated Activities on Salmon Ecosystems in the Nushagak River and Kvichak
River watersheds, Bristol Bay."
EPA RESPONSE: The assessment addresses multiple scales: the Bristol Bay watershed, the
Nushagak and Kvichak River watersheds, the watersheds of the three streams draining the Pebble
deposit, and the watersheds crossed by the transportation corridor. These multiple scales, and how
they are used throughout the assessment, are described more clearly in the revision (Chapter 2).
ATKINS RESPONSE: This response is adequate.
EPA FINAL RESPONSE: No response required.
DAUBLE RESPONSE: I was not one for changing the title, rather suggested an expanded
description of geographic scope. One issue I have with the revised Assessment was the use of
the phrase "multiple spatial scales" (second full paragraph p. ES-2). This term is commonly
used by stream ecologists to describe different measurement scales of habitat assessments (i.e.,
individual, reach, watershed). As such, the term suggests a hierarchical approach, which was
not the case for this assessment. I prefer the term first used on p. 1-3 (third full paragraph
Chapter 1 of the main document) "multiple geographic scales." I suggest relevant wording in
the E.S. be revised to be consistent with the description used throughout the Introduction of the
main document. In addition, please revise text under section 2.2.2 Spatial Scales and Table 2.1
to show that data was considered across five "geographic scales."
EPA FINAL RESPONSE: This change has been made in the final assessment.
SLAUGHTER RESPONSE: OK.
EPA FINAL RESPONSE: No response required.
WEBER SCANNELL RESPONSE: The reviewer has no further comment and accepts the title
as is.
EPA FINAL RESPONSE: No response required.
Revise the Executive Summary to more precisely reflect the findings in the document.
EPA RESPONSE: The Executive Summary has been rewritten to reflect the revised assessment
findings.
ATKINS RESPONSE: This response is adequate.
EPA FINAL RESPONSE: No response required.
DAUBLE RESPONSE: I was impressed with the revised Executive Summary (ES). This
section might be the most important part of the revised Draft Assessment due to being the only
thing some people will read. Thus, it is important that it be an accurate, yet synthetic, version
of the main document. Supporting graphics, e.g., Tables ES.3, ES.4 and Figure ES.6 are
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excellent choices. Note, however, that topics in the E.S. are not presented in parallel format or
in the same sequence of topics (in terms of heading structure) with those in the main document.
Headings in the E.S. include the word "risks" while comparable sections in the main document
do not. The E.S. uses the term common-mode failures, which I infer is the same topic as those
discussed in Chapter 8 of the main document.
EPA FINAL RESPONSE: The audience for the Executive Summary is, as the comment suggests,
different from that of the rest of the document. We believe these differences in style and
terminology are appropriate when writing for a broader audience.
SLAUGHTER RESPONSE: The Executive Summary of the revised Assessment is provides a
comprehensive overview. (I still question the discussion of probabilities in relation to TSF dam
failure (p. ES-21), as noted in my other comments.)
EPA FINAL RESPONSE: The comment concerning probabilities is addressed where it appears.
WEBER SCANNELL RESPONSE: The reviewer is satisfied with the expanded Executive
Summary.
EPA FINAL RESPONSE: No response required.
The appendices contain detailed and useful information that should be summarized and included in
the main document (e.g., Appendix E: Economics, Appendix G: Road and Pipelines, and Appendix I:
Mitigation). Additionally, consider expanding the preface to include information on the use of the
appendices. If the information is not included in the main report, then justify its absence.
EPA RESPONSE: More information from the appendices was brought forward into appropriate
chapters of the revised report. The purpose of the appendices—to provide the detailed background
characterization necessary for the ecological risk assessment—has also been clarified in Chapter
2. The document no longer contains a preface because that material has been incorporated into
Chapters 1 and 2.
ATKINS RESPONSE: This response is adequate.
EPA FINAL RESPONSE: A brief Preface has been added to the final assessment, but the
material referred to in the original comment above is still found in Chapters 1 and 2.
CAROTHERS RESPONSE: More information from Appendix E (as well as Appendix D) has
been included in the main body of the report, but as described below, more information from
Appendix E is relevant to include, particularly Alaska Native engagement in commercial
fishing and fish-based tourism in this region.
EPA FINAL RESPONSE: A paragraph has been added to Section 5.4.2.1 that includes
information on the close connection between the Alaska Native community and the regional
economy, incorporating regional employment information from Appendix E.
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DAUBLE RESPONSE: I noted several examples where specific Appendices were cited in the
main document as a source for more detailed information. It was also apparent that material
was brought forward where appropriate.
EPA FINAL RESPONSE: No response required.
SLAUGHTER RESPONSE: I support the decision to incorporate much of the previous
Appendix information into the body of the Assessment (as recommended in 2012).
EPA FINAL RESPONSE: No response required.
WEBER SCANNELL RESPONSE: In the response to charge questions, the reviewer noted the
additional information in the main body of the document. The changes enhance the discussions
and provide valuable information. The concerns of this reviewer have been satisfied.
EPA FINAL RESPONSE: No response required.
Discuss in more detail the instructive and well-thought-out conceptual models (pages 3-7 to 3-11)
illustrating the impacts of mining on Bristol Bay ecosystem processes. Also, consider expanding the
conceptual models to include wildlife, fish-wildlife interactions, vegetation/terrestrial habitat, and
hydrologic processes. Allow them to guide the text because they appear detailed and complete.
EPA RESPONSE: Additional information on the use of conceptual models throughout the
assessment has been incorporated into Chapter 2. The more comprehensive conceptual models
presented in Chapter 6 (Chapter 3 in the original draft) have been broken into their relevant
component parts throughout the risk analysis and characterization chapters, to better frame the
specific pathways addressed in each chapter. Additional conceptual models considering impacts on
wildlife, Alaska Native populations, and cumulative effects of multiple mines have been added to
Chapters 12 and 13.
ATKINS RESPONSE: This response is adequate.
EPA FINAL RESPONSE: No response required.
DAUBLE RESPONSE: This reviewer considers the conceptual models as an attempt to
provide a visual representation of a more much complicated (and largely unquantifiable)
process than can be described in words. It was helpful to include a separate model for separate
chapters. This representation simplified the thought process. One challenge is that Box 2.1 (so-
called guide to conceptual model diagrams) was presented well before the first (complicated)
model in Chapter 6. Thus, the reader is forced to refer to the box to sort out elements that
composed the various pathways, modifiers, etc. One thing that would help Box 2.1 is to provide
specific examples of modifying factors (note the description is not exactly in layman's terms),
for example, temperature. Also, perhaps a short version of what is included under "When
viewing these diagrams..." could be added to the legend of each individual conceptual model to
aid the reader. For example "Arrows leading from one shape to another indicate a cause-effect
relationship with bold lines, arrows and outlines indicating high-priority pathways that were
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evaluated." Finally, there are up/down arrows within most boxes. The legend should state what
these mean.
EPA FINAL RESPONSE: Box 2-1 and the legends of the conceptual model diagrams have been
modified as suggested.
SLAUGHTER RESPONSE: The addition of conceptual models and flow charts throughout the
revised Assessment is really appreciated - they add clarity to the issues.
EPA FINAL RESPONSE: No response required.
WEBER SCANNELL RESPONSE: Chapter 6 contains an expanded and clarified discussion of
conceptual models used in the Assessment. Although Figure 3.2A-D in the earlier draft
presented figures representing the conceptual models used in the Assessment, these diagrams
were difficult to interpret without sufficient accompanying information. Discussions on
conceptual models in the current revision have been augmented by the list of stressors (Table 6-
9) and following text. The discussions in Chapters 12 and 13 also help clarify the potential
stressors and endpoints. The reviewer is satisfied that the initial comments have been
addressed.
EPA FINAL RESPONSE: No response required.
WHITNEY RESPONSE: The conceptual wildlife model in Chapter 12 is a good addition and
clearly shows that direct effects on wildlife are outside the scope of the current assessment. See
comments above and below for the need to explain why direct impacts on wildlife are outside
the scope and why wildlife species are not a part of the salmon ecosystems of Bristol Bay.
EPA FINAL RESPONSE: These comments are addressed where they appear.
Incorporate the information contained in the conceptual models into a formal framework, such as a
Bayesian or other decision-analysis models.
EPA RESPONSE: This is an excellent suggestion for future efforts, but is beyond the scope of the
current assessment.
Creating a Bayesian Belief Network would require that the Agency convene experts to subjectively
estimate the probabilities of each transition in the conceptual models. In contrast, this assessment
is intended to elucidate the risks from potential mining based on available data and analyses of
those data.
A Decision Analysis would require that alternative outcomes be specified, the utility of each
outcome for a decision milker be defined and the probabilities of each outcome be estimated for
each possible decision so that the expected utilities of each outcome can be calculated. Because
this assessment is not a decision document, these requirements are not feasible or appropriate.
ATKINS RESPONSE: This response is adequate.
EPA FINAL RESPONSE: No response required
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DAUBLE RESPONSE: I agree with EPA's comment.
EPA FINAL RESPONSE: No response required.
SLAUGHTER RESPONSE: OK.
EPA FINAL RESPONSE: No response required.
WEBER SCANNELL RESPONSE: The reviewer accepts the EPA response.
EPA FINAL RESPONSE: No response required.
Generate a standard operating protocol for significant figures and use it throughout the document.
EPA RESPONSE: The authors have carefully addressed this issue. Numbers from the literature
or from the PLPEBD retain the number of significant figures in the original. Numbers derived
for this assessment have the appropriate number of significant figures given the precision of the
input data and uncertainties due to modeling and extrapolation.
ATKINS RESPONSE: This response is adequate.
EPA FINAL RESPONSE: No response required.
DAUBLE RESPONSE: I am convinced proper homework was done on this topic.
EPA FINAL RESPONSE: No response required.
SLAUGHTER RESPONSE: OK.
EPA FINAL RESPONSE: No response required.
WEBER SCANNELL RESPONSE: Perhaps a statement in the text could be added to explain
this (there may already be such clarification, but I did not find it.)
EPA FINAL RESPONSE: A paragraph explaining the use of significant figures has been added
to Section 2.1.1.
Remove all references to Mount St. Helens as a surrogate for a TSF failure. Using a non-human-
caused release of material into the ecosystem as an analogue for a mine failure is not comparable in
terms of likelihood or risk for a human-caused release. It would be more appropriate to extrapolate
from the impacts of known mine failures.
EPA RESPONSE: We are puzzled by this comment. The Mount St. Helens data were used strictly
to address the rate of benthic habitat recovery from a massive deposition offine mineral particles.
The hydrological processes that determine the recovery of substrate texture and the requirements
offish or aquatic invertebrates are not known to depend on whether mineral particles were from a
natural event or an anthropogenic event. We have reviewed the literature on known mine failures.
They studied tailings spills in terms of toxicity but not in terms ofphysical habitat effects, which is
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why we used Mount St. Helens data. Nevertheless, we have removed references to Mount St.
Helens in the revised assessment to eliminate concern.
ATKINS RESPONSE: This response is adequate.
EPA FINAL RESPONSE: No response required.
DAUBLE RESPONSE: The issue was raised primarily because of concern raised by some
members of the peer review panel that more relevant examples were available and should be
used. I have no issue if these references are used in the context of deposition of mineral
particles similar in nature to those that could be released during a TSF failure.
EPA FINAL RESPONSE: Because the usefulness of Mount St. Helens as an example appeared to
be the minority opinion, all mention of Mount St. Helens has been removed from the final
assessment.
SLAUGHTER RESPONSE: I was not enthusiastic about removal of all reference to Mount St.
Helens, simply because that event does provide a case history of massive sediment loading and
long-term stream and landscape response. However, I think I understand the concern that
heavy reference to Mount St. Helens might imply that the volcanic eruption was analogous to a
TSF dam failure, though the causes would be unrelated. I would be comfortable with again
utilizing the sediment remobilization, channel and habitat "recovery" information from Mount
St. Helens research in generalizing about consequences of a major TSF dam failure.
EPA FINAL RESPONSE: Because the usefulness of Mount St. Helens as an example appeared to
be the minority opinion, all mention of Mount St. Helens has been removed from the final
assessment.
VAN ZYL RESPONSE: The author would like to provide some further input about the use of
Mount St. Helens data as a surrogate for the "rate of benthic habitat recovery from a massive
deposition of fine mineral particles". The geochemical composition, particle size and the
temperature at the time of deposition of the fine materials from the Mount St. Helens event
must be compared to that of tailings before this event can be used as a surrogate. The EPA
Responses indicate that "we have removed references to Mount St. Helens in the revised
assessment to eliminate concerns", however on p. 9-27 of the Second Draft there is a reference
to Major et al. (2000). On p. 15-40 of the Second Draft this reference is given as: Major, J., T.
Pierson, R. L. Dinehart, and J. E. Costa. 2000. Sediment yield following severe volcanic
disturbance — A two-decade perspective from Mount St. Helens. Geology 28: 819-822. This
seems to still refer to Mount St. Helens in terms of long-term sediment transport. There seems
to be a disconnect between the statement in the EPA Responses and the Second Draft that must
be corrected.
EPA FINAL RESPONSE: This was an oversight in the revised assessment and it has been
corrected in the final assessment. All references to Mount St. Helens now have been removed from
the final assessment.
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WEBER SCANNELL RESPONSE: The reviewer is satisfied with this change; removing
reference to Mt. St. Helens eliminates potential confusions.
EPA FINAL RESPONSE: No response required.
Ensure that the draft assessment remains part of the public record, allowing the document history to
remain intact.
EPA RESPONSE: All drafts of the watershed assessment will remain part of the public record.
ATKINS RESPONSE: This response is adequate.
EPA FINAL RESPONSE: No response required.
DAUBLE RESPONSE: No comment.
EPA FINAL RESPONSE: No response required.
SLAUGHTER RESPONSE: OK.
EPA FINAL RESPONSE: No response required.
WEBER SCANNELL RESPONSE: The reviewer appreciates that this is being done.
EPA FINAL RESPONSE: No response required.
Research Needs
What are the acute and chronic impacts of mixtures of contaminants, including metals, acid mine
drainage, etc., on the fauna and flora of the Nushagak River and Kvichak River watersheds? What
species are most sensitive and might surrogate species exist for those for which we do not have data?
Review the European literature and regulatory requirements for additional data.
EPA RESPONSE: The acute and chronic impacts of contaminant mixtures, including metals and
acid mine drainage (i.e., metals in low pH-waters) were addressed using concentration additivity
models in the leachate chemistry tables in Chapters 5 and 6 (now Chapters 8 and 11). Additional
toxicity data were obtained by searches of the EU and OECD database eChem, EPA's ECOTOX
and the Environment Canada site. More metals are now included. In general, metals are most
toxic to aquatic arthropods rather than fish, as discussed for copper.
ATKINS RESPONSE: This response is adequate.
EPA FINAL RESPONSE: No response required.
DAUBLE RESPONSE: What I found in the Revised Assessment was considerably more
toxicity data, including information from the most recent open-literature publications. The
potential risk of exposures to contaminant mixtures (a complicated topic) was addressed using
the additive model, which is about all you can do without having specific mixture data.
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EPA FINAL RESPONSE: No response required.
SLAUGHTER RESPONSE: This seems to be well covered in the revised Assessment.
EPA FINAL RESPONSE: No response required.
WEBER SCANNELL RESPONSE: The reviewer is satisfied, but realizes that should mine
development go forward, it may be necessary for permit applicants to conduct specific toxicity
studies. These potential studies are beyond the scope of the Assessment.
EPA FINAL RESPONSE: No response required.
Can an inventory of nutrients, total organic carbon, and dissolved organic carbon inputs to aquatic
environments be developed that demonstrates their relative magnitude and spatial variation from
headwaters to Bristol Bay? What is the relative importance of marine-derived nutrients relative to
other nutrients from watershed and terrestrial sources? What is the current atmospheric input of
nutrients?
EPA RESPONSE: These data would be very useful in the risk assessment but are not currently
available for the Bristol Bay region. We agree this is a research need.
ATKINS RESPONSE: This response is adequate.
EPA FINAL RESPONSE: No response required.
DAUBLE RESPONSE: Given the emphasis in this document on the importance of marine-
derived nutrients from salmon populations on the Bristol Bay watershed, it would be
instructive if an example or two was provided from the literature on the relative magnitude
and/or importance of nutrient inputs to watersheds from anadromous fish populations,
terrestrial, atmospheric and/or autochthonous sources.
EPA FINAL RESPONSE: Text has been added to Chapters 5 and 7 citing research that
demonstrates the relative proportion of marine-derived nutrients in freshwater taxa in the region
and the relative contributions of other subsidies.
SLAUGHTER RESPONSE: OK.
EPA FINAL RESPONSE: No response required.
WEBER SCANNELL RESPONSE: The reviewer agrees with the EPA response; this is a
research need that should be fulfilled at the permitting stage.
EPA FINAL RESPONSE: No response required.
What are the locations of subsistence areas and can these areas be characterized and differentiated by
collecting local environmental and ecological knowledge (e.g., fish overwintering areas, climate
change, ecological shifts, etc.)?
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EPA RESPONSE: The revised assessment incorporated current data on subsistence use areas
available fromADF&G. EPA acknowledges that these data are incomplete and would encourage
additional collection of subsistence data and Traditional Ecological Knowledge.
ATKINS RESPONSE: This response is adequate.
EPA FINAL RESPONSE: No response required.
CAROTHERS RESPONSE: The Revised Assessment includes more detailed information
about subsistence harvests and use areas (e.g., Figure 5.12). The necessary caveats that these
data are coarse and incomplete, and that additional studies of traditional ecological knowledge
(especially in times of social and environmental change) are greatly needed, are important to
highlight in the main text (e.g., coarseness and limitations of data explained in Box 5.1 should
also be repeated in main text).
EPA FINAL RESPONSE: Caveats on subsistence data and a reference to Box 5-2 (Box 5-1 in the
April 2013 draft of the assessment) have been added to Section 5.4.2.2.
DAUBLE RESPONSE: No comment.
EPA FINAL RESPONSE: No response required.
SLAUGHTER RESPONSE: That is probably all that you can do at this stage. Figure 5-12
attempts to show generalized subsistence use.
EPA FINAL RESPONSE: No response required.
WEBER SCANNELL RESPONSE: This comment is outside my area of expertise. I defer to
the other reviewers who are more qualified to comment on subsistence issues.
EPA FINAL RESPONSE: No response required.
What impact might mining have on other important wildlife species in the basin (e.g., freshwater
seals in Iliamna Lake)?
EPA RESPONSE: The scope of the assessment is focused on potential risks to salmon from large-
scale mining and salmon-mediated effects to indigenous culture and wildlife. Direct effects on
wildlife from large-scale mining are likely to be important and Appendix C (now a stand-alone US
Fish and Wildlife report) provides useful information for a future evaluation of direct effects on
wildlife from large-scale mining. We agree that this is an important area for future research.
ATKINS RESPONSE: This response is adequate.
EPA FINAL RESPONSE: No response required.
DAUBLE RESPONSE: No comment.
EPA FINAL RESPONSE: No response required.
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SLAUGHTER RESPONSE: OK.
EPA FINAL RESPONSE: No response required.
WEBER SCANNELL RESPONSE: The reviewer is satisfied.
EPA FINAL RESPONSE: No response required.
What is the comprehensive hydrologic regime of the specific project mining area, and the broader
watershed system as characterized by baseline monitoring, spatial distribution, and quantitative flow
of surface- and ground-waters?
EPA RESPONSE: Comprehensive spatial estimates of mean annual flow are now presented in
Chapter 3. Quantification of spatial and temporal patterns of groundwater flows is an
acknowledged highly desirable product, but it not feasible within the scope of this assessment.
Results of an independent groundwater-surface water modeling effort are described in Chapter 7.
ATKINS RESPONSE: This response is adequate.
EPA FINAL RESPONSE: No response required.
DAUBLE RESPONSE: It is apparent that the hydrological description was much expanded.
These additions are appropriate and informative.
EPA FINAL RESPONSE: No response required.
SLAUGHTER RESPONSE: The revised hydrologic analyses of the Assessment are explained
well and are very useful. Admittedly, much site-specific data would be required to thoroughly
understand the complete surface water/groundwater system, in its current state and potentially
during and after mine implementation.
EPA FINAL RESPONSE: No response required.
WEBER SCANNELL RESPONSE: This reviewer acknowledges that in-depth discussions of
groundwater and surface water are beyond the scope of the Assessment and beyond the
availability of information at this time. In-depth data on flows will be required should the
project proceed to the permitting stage. The reviewer is satisfied that sufficient available data
have been used in the Assessment.
EPA FINAL RESPONSE: No response required.
What is the cumulative impact of commercial fisheries on the Bristol Bay watershed, especially in an
ecosystem context as related to marine-derived nutrient and energy flow? Acknowledge that
commercial fishing has had an impact on the amount of marine-derived nutrients returned to the
watersheds.
EPA RESPONSE: The impact of commercial fisheries on the watershed is not within the scope of
this assessment. Information on commercial fisheries management has been added in Box 5-2.
However, the purpose of this assessment is not to assess the relative effects ofpotential mining and
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commercial fishing—it is to evaluate potential effects on endpoints if a mine were to be developed,
given existing conditions and activities in the region.
ATKINS RESPONSE: This response is adequate.
EPA FINAL RESPONSE: No response required.
DAUBLE RESPONSE: I am satisfied with the additional information on commercial fisheries
management practices included in the assessment.
EPA FINAL RESPONSE: No response required.
SLAUGHTER RESPONSE: I note that commercial and subsistence harvest are both
considered in Chapter 5. The Assessment thus does reference commercial harvest, even if not
evaluating the long-term consequences of that harvest, with or without mining activity in the
Bristol Bay watershed.
EPA FINAL RESPONSE: No response required.
WEBER SCANNELL RESPONSE: One of the intents of the review committee in making this
comment was to state that this is not a completely unaltered watershed; that there have been
effects to the ecosystem by fishing and subsequent removal of nutrients. However, the EPA
statement "given existing conditions" serves to separate pristine from existing conditions.
Perhaps a statement in the Executive Summary that the Assessment examines impacts of
mining activities in the existing conditions of the Bristol Bay region (for example, Page ES-4,
paragraph 3: "This is not an in-depth assessment...") would clarify this issue.
EPA FINAL RESPONSE: This clarification has been made in the Executive Summary.
WHITNEY RESPONSE: The logic used here is not clear. The logic assumes commercial
fishing is sustainable and therefore has no impact on salmon or the salmon ecosystem and
therefore commercial fishing can be ignored without an adverse consequence to the assessment.
Such an assumption is not factual. Commercial fishing kills 70% of the sockeye every year.
This has to have an impact on the salmon ecosystems of Bristol Bay. If this is not the case
explain why and explain why Hilborn (2005) as cited in my original comments is wrong.
EPA FINAL RESPONSE: This is an assessment of the potential effects of mining; it is not an
assessment of the effects of commercial fishing or other influences (e.g., subsistence or
recreational fishing, predation, disease) on salmon populations. We do not state that commercial
fishing has no impact on salmon or salmon ecosystems, but these impacts are not relevant to
evaluating how mining may affect salmon populations.
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3.2 General Impressions
David A. Atkins, M.S.
The Bristol Bay Watershed Assessment (the Assessment) presents a comprehensive overview of
current conditions in the watershed and establishes the uniqueness and global importance of the area
to global salmon ecology (e.g., the report states that nearly 50% of the global sockeye salmon
population comes from Bristol Bay and nearly 50% of the salmon in Bristol Bay come from the
Nushagak and Kvichak Rivers, which encompass nearly half of the watershed area). The report also
describes in detail the importance of the fishery to Native Alaska cultures, the importance and
uniqueness of subsistence activities, and the scale of the commercial fishery. Furthermore, the report
also outlines the reliance of the local economy on the salmon fishery.
EPA RESPONSE: No change suggested or required.
ATKINS RESPONSE: None.
EPA FINAL RESPONSE: No response required.
There is no question that a mine, especially of the type and magnitude analyzed in the Assessment,
could have significant impacts and that if these impacts are not or cannot be properly managed and/or
mitigated, the consequences could be profound. The Assessment presents a mining scenario based on
preliminary documents prepared for the Pebble Project, which sets out a conventional approach for
development of a very large mine that includes open-pit and block-cave underground mining
methods and conventional waste rock and tailings management. Development of the mine as
proposed would eliminate streams and wetlands in the project area permanently. The importance of
this impact is not put in context of the watershed as a whole, so it is not possible to determine the
magnitude of the risk to salmon. The Assessment also did not consider whether there are any
methods that could effectively minimize, mitigate or compensate for these impacts.
EPA RESPONSE: A characterization of the landscape factors influencing salmon habitat
potential is now included to provide context for the stream habitat impacts described in the
document (Chapter 3). The assessment describes the magnitude of risks to salmon habitat. Due to
lack of knowledge of limiting factors, ascribing comprehensive risks to salmon populations is not
feasible in this assessment. Mitigation to compensate for effects on aquatic resources that cannot
be avoided or minimized by mine design and operation would be addressed through a regulatory
process that is beyond the scope of this assessment. Nevertheless, in response to public and peer
review comments we have included a discussion of compensatory mitigation in Appendix J of the
revised assessment.
ATKINS RESPONSE: This response is adequate.
EPA FINAL RESPONSE: No response required.
The Assessment also focuses on the risk of failure of the tailings storage facility, a low probability,
but high impact scenario. The Assessment further describes the potential for long-term acid and
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metals production from waste rock and the necessity for water treatment. Under the mining scenario
as described, perpetual management of the geotechnical integrity of the waste rock and tailings
storage facilities and perpetual water treatment could be necessary. In addition, failure is always a
possibility, albeit a possibility that is difficult to quantify with any degree of certainty as explained in
the Assessment. The Assessment also does not consider alternative engineering strategies (so called
'best practice' approaches) that could lessen the risk of failure and possibly the necessity for
perpetual management and water treatment. As such, the report could be considered a screening level
assessment that presents the likelihood of occurrence and corresponding consequences of failures
under the presented development scenario, but does not describe the magnitude of risk to salmon.
EPA RESPONSE: With regard to the terminology of "best", "good", or other terms for the
practices used, what was intended to be conveyed in the assessment is that we assumed modern
mining technology and operations. Measures for minimizing and controlling sources ofpollution,
outside of stormwater requirements, may be referred to as best practices, state of the practice, good
practice, conventional, or simply mitigation measures. We have added a text box in the revision
(Chapter 4) to discuss terms. Mitigation measures considered feasible, appropriate, and
'permittable' (as per Ghaffari et al. 2011) were considered in the assessment, and these are
measures common to other copper porphyry mines. Evaluation of alternative strategies (e.g., other
options presented in Appendix I) is outside the scope of this assessment, but such evaluation
should be part of the permitting process for a specific mining plan. The assessment describes the
magnitude of risks to salmon habitat. Due to lack of knowledge of limiting factors, production,
and demographics, ascribing comprehensive risks to salmon populations is not feasible for this
assessment.
ATKINS RESPONSE: I concur with this response. It does highlight information on alternative
strategies that may come from a specific mining plan as it is assessed in the permitting process.
EPA FINAL RESPONSE: No response required.
Steve Buckley, M.S., CPG
The assessment attempts to evaluate the potential impacts of mining development in the Nushagak
and Kvichak watersheds. The main deficiency in the assessment is that it uses only two hypothetical
mine scenarios to bracket the potential impacts of mining activities on the ecological resources in the
watershed. Both of these mine scenarios are larger than the 90th percentile of all porphyry copper
deposits in the world. In order to properly assess the potential effects of mining activities, in the
absence of any specific mining proposal, a minimum mine scenario on the order of the 50th percentile
of worldwide porphyry copper deposits would be more appropriate. Three or four mine scenarios
would allow for a broad range of analysis, and the reader would be able to put the potential impacts
of mining development in wider perspective.
EPA RESPONSE: A third mine size scenario (Pebble 0.25, 250 million tons) is included in the
revised assessment, to represent the worldwide median size porphyry copper mine (Singer et al.
2008).
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BUCKLEY RESPONSE: This is a major improvement in the assessment.
EPA FINAL RESPONSE: No response required.
A large part of the assessment provides information related to catastrophic potential system failures
such as tailings dam failures and pipeline ruptures. There is inadequate information on, and analysis
of, potential mitigation measures at the early stages of mine development, which would attempt to
reduce the impacts of mining activities on fish and water quality. The bulk of the document is
dedicated to evaluating the impacts of tailings dam failure on aquatic resources and yet in Chapter 4,
the assessment provides a probability of tailings dam failure at 1 in every 2,000 mine years.
EPA RESPONSE: Mitigation measures were included in the draft assessment and are more
clearly identified in the revision. Analysis of alternative mitigation measures would be part of a
permitting process and is outside the scope of this assessment. A discussion of compensatory
mitigation in the Bristol Bay watershed has been added as Appendix J in the revised assessment.
Although failures of a TSF might be rare, they do happen, their effects may be very damaging,
and they could be devastating to local communities; thus, the assessment evaluates what risks
might be evident should such an event occur. The revised assessment also expands the evaluation
of risks for some lesser magnitude, but higher probability, events.
BUCKLEY RESPONSE: The reorganization of the assessment improves the discussion about
when and where mitigation measures might enter the regulatory process and the addition of
several additional system failures brings more balance to the TSF failure analysis. The level of
detail on the TSF analysis still might present the reader with the sense that the impacts from
this type of system failure can be modeled or predicted beyond actuality.
EPA FINAL RESPONSE: No response required
The assessment identifies the interconnectivity of groundwater, surface water, and fish habitat as
being a major component of the quality of the fishery in the watershed yet puts relatively little effort
into the analysis of the detailed relationships between groundwater, surface water, water quality, and
fish habitat, even though this is likely the most important factor in assessing the potential impacts of
mining activities on the fisheries in the watershed.
EPA RESPONSE: We lack the data to demonstrate this interconnectedness in a spatially and
temporally uniform manner, but do include examples of known points of high connectivity and
modeled locations of high groundwater-surface water interaction (Chapter 7).
BUCKLEY RESPONSE: The addition of Figure 7.14 improves the understanding of some of
these relationships. More effort could be put into bringing this information forward given its
importance to understanding the watershed and fish habitat.
EPA FINAL RESPONSE: We agree that Figure 7-14 provided useful information on
groundwater and fish habitat, but we have removed it from the final assessment. Figure 7-14 came
from a report (Wobus et al. 2012) that was coauthored by Dr. Ann Maest, which had been peer
reviewed for EPA by an independent review panel. Although the peer review supported the use of
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the information in Wobus et al. (2012), we have withdrawn this information and citations of
Wobus et al (2012) because accusations of fraud in another matter against Dr. Maest led to
questions concerning the potential for fraud in Wobus et al. (2012). This report was used only to
support our analyses, and its removal has not changed the assessment's findings.
Additional mine scenarios and a more detailed investigation of the geomorphology, surface, and
groundwater hydrology and their relation to fish habitat would provide the reader with a more
accurate and more useful scope of analysis.
EPA RESPONSE: We now describe the broad geomorphic context for stream habitat in the
Nushagak and Kvichak River watersheds by characterizing gradient and watershed terrain
(Chapter 3). The revised scenarios include an additional mine size (representative of the worldwide
median size). The revision includes more failure scenarios (e.g., diesel pipeline failure, quantitative
water treatment failure, and refined seepage scenarios) and explains why these particular failure
scenarios were chosen.
BUCKLEY RESPONSE: The addition of the stream characterization in Chapter 3 and the
analysis of the 0.25 mine scenario are major improvements.
EPA FINAL RESPONSE: No response required.
Courtney Carothers, Ph.D.
Synopsis: EPA's draft document examines the potential impacts of large-scale mining development
on the quality, quantity, and genetic diversity of salmonid fish species in the Nushagak River and
Kvichak River watersheds of Bristol Bay, Alaska. To the extent that both wildlife and Alaska Native
communities in the region depend upon salmonids, fish-mediated impacts to these other "endpoints
of interest" are also explored. A hypothetical mining scenario, informed by current exploration,
planning, and study in the Pebble deposit area, is described using minimum and maximum estimates
for mine production and includes the construction of a transportation corridor to Cook Inlet. Even in
the absence of any failures or accidents, construction and operation of such a mine would have
significant impacts to salmonids in stream systems proximate to the mine footprint with some related
impacts to wildlife and human communities. At least one or more accidents or failures are expected
to occur over the long lifetime of the mine. Immediate and long-term severe impacts to salmonids are
expected to occur with any significant failure, with relatedly pronounced impacts to wildlife and
Alaska Native communities in the region. Multiple mines in the region would amplify these impacts.
EPA RESPONSE: No change suggested or required.
General impressions: Overall, the main report is well-written and presents information in multiple
ways, including: narrative, conceptual models, images, figures, and tables. The report synthesizes a
large amount of information, much of which is described in detail in the report's appendices. The
report highlights the unique characteristics of this watershed: incredibly productive and sustainable
salmon fisheries, relatively little large-scale modification of the natural environment, and active
subsistence-based indigenous cultures still occupying their homelands and many still using their
Native language. Making central these features of the watershed, the tone of the report suggests that
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some negative impacts to salmonids, wildlife, and Alaska Native cultures are necessarily expected to
accompany any large-scale mining development and operation in this region.
EPA RESPONSE: No change suggested or required.
The document should provide a clear articulation of the scope of human impacts considered in this
assessment. The main report considers only fish-mediated impacts to Alaska Native cultures. The
restriction of scope to only fish-mediated impacts should be further clarified. A host of social,
cultural, and economic impacts would accompany large-scale mining development in this region.
These direct and indirect human impacts, both positive and negative, were the focus of many public
comments on the EPA draft document, yet they fall outside of the scope of consideration in this
report. If the narrowed scope of fish-mediated impacts is justified, these other impacts should be
clearly identified as outside of the scope of this report. At times in the report (e.g., p. 5-77), these
other impacts are superficially mentioned. Unless a full treatment of these impacts is included
(including a presentation of a large literature explores these impacts internationally, e.g., Ballard and
Banks 2003), this cursory discussion should be removed. If maintained, the narrow scope should be
reiterated throughout the report to remind the reader that these larger human impacts are not
considered.
EPA RESPONSE: The scope of the assessment has been more clearly articulated in Chapter 2,
which also now contains an overview conceptual model diagram demonstrating which potential
sources, stressors, and responses associated with large-scale mining were considered outside of
scope. The fact that direct impacts to Alaska Native cultures are not within the scope of the
assessment does not imply that they will not occur or that they are unimportant, and this has been
clarified in Chapters 2 and 12.
The report should articulate more clearly why Alaska Native cultures are the only human groups
included in the assessment of fish-mediated human impacts. The report notes: "because... Alaska
Native cultures are intimately connected and dependent upon fish,.. .the culture and human welfare
of indigenous peoples, as affected by changes in the fisheries are additional endpoints of the
assessment" (ES-1-2). This suggests that the limitation of fish-mediated human considerations to
Alaska Native cultures is not due to government-to-government relationship between tribes and the
federal government, nor the special status afforded by environmental justice concerns, but rather
because of their close connections to, and dependence on fish. Arguably, other human groups also
have connections to fish and depend upon on salmon in this region in various ways, but are excluded
from analysis of potential impact in this report. This comment is not meant to detract from the
importance of the focus on Alaska Native cultures and the primarily indigenous communities in this
region for assessing fish-related impacts. Rather, the comment is made to suggest the inclusion of a
clear justification for this focus, or the broadening of scope to include other human groups who are
also connected to, and dependent upon, salmon in this region (e.g., substantial information on the
economic dimensions of salmon resources in this region is summarized in Appendix E, but little is
presented in the main report). Additionally, the assessment of fish-mediated effects to Alaska Native
cultures is primarily focused on subsistence fisheries. More discussion of the role of commercial
engagements in salmon fisheries (e.g., commercial harvesting, processing, recreational fishing
businesses and employment) in the watershed communities in this region would be helpful.
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EPA RESPONSE: We focused on the Alaska Native communities in response to the original
request we received from nine federally recognized tribal governments. The text (Chapter 12) has
been expanded to acknowledge the strong cultural ties of many non-Alaska Natives to the region,
and potential effects on all residents from loss of a subsistence way of life. However, the focus of
the assessment remains on effects on indigenous cultures. The importance of the commercial
fishery to the regional culture has been added to the text.
CAROTHERS RESPONSE: Comments here are addressed above in response to clarification
of scope in Section 1, Key Recommendations [Section 3.1 in this document].
EPA FINAL RESPONSE: See responses under previous section.
Dennis D. Dauble, Ph.D.
Overall, the main report and each of the accompanying appendices were well written. I was unable to
identify major inaccuracies or bias in the material as presented. There were shortcomings in the main
report, however. For example, some topics would benefit by being expanded (Sections 5.6 and 8.7),
while others have more detail than appeared necessary (Section 6.1). The assessment effectively
addressed three appropriate time periods: (1) operation, (2) post-closure, and (3) perpetuity. Potential
effects are bounded by a minimum and maximum mine size, which is also appropriate. Inclusion of
inference by analogy strengthened the conclusions reached in the assessment and helped validate
results obtained from model predictions.
EPA RESPONSE: Previous Section 5.6 (wildlife and culture) has now been expanded and treated
as a stand-alone chapter (Chapter 12). The summaiy of risks from the mine scenarios (previous
Section 8.7, now Chapter 14) has been expanded to include fish-mediated risks to wildlife and
culture, and more numerical results are included.
DAUBLE RESPONSE: These changes are all improvements to the May 2012 Draft
Assessment. Each chapter now begins with a clear description of what it includes. On a more
editorial note, Chapters 7, 8,11,12, and 14 begin with an overview of what follows, but have no
heading. In contrast, Chapters 9 and 13 begin with an Introduction or Overview heading.
These differences may have been due to different authors and different writing styles.
EPA FINAL RESPONSE: The introductory sections of Chapters 9 and 13 have been reorganized
to match the other chapters.
Most figures and tables were useful. The conceptual models and accompanying illustrations of
potential habitat effects (Figs 3-2A and C) are important because they provide a view of complicated
pathways and relationships among potential activities and environmental attributes. However, these
relationships are not revisited in any detail later in the document. I recommend discussing the
conceptual models in more detail in the main report (Section 3.6) and summary section in Chapter 8.
EPA RESPONSE: Additional information on the use of conceptual models throughout the
assessment has been incorporated into Chapter 2. The more comprehensive conceptual models
presented in Chapter 6 (previously in Chapter 3) have been broken into their relevant component
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parts throughout the risk analysis and characterization chapters, to better frame the specific
pathways addressed in each chapter.
DAUBLE RESPONSE: Having separate (and less complicated) conceptual models relevant to
specific risk scenarios is an improvement.
EPA FINAL RESPONSE: No response required.
The Integrated Risk Assessment (Chapter 8) did a creditable job of summarizing habitat losses and
risks from mine operations. What is missing, however, are quantitative descriptions of habitat lost
relative to total habitat available in the larger watershed and individual systems. Habitat loss should
be further discussed in terms of salmonid life stage and productivity (i.e., not all stream miles are
equal).
EPA RESPONSE: Unfortunately, no salmon habitat characterization is available for the region.
The State of Alaska has not even identified all anadromous streams in the region. Productivity
data are not available, even for the streams studied by the Pebble Limited Partnership. However,
the revised Chapter 14 contains tables summarizing habitat loss in stream lengths and wetland
areas.
DAUBLE RESPONSE: My question may have been misinterpreted (or poorly worded). What I
found in the revised Draft Assessment is a much improved description of habitat use by
salmonids of concern, including stream miles and locations for both spawning and rearing
(where known). I did not expect that habitat information was available for the entire
watershed. There was some information on productivity in terms of the range of returning
adults.
EPA FINAL RESPONSE: No response required.
If anything, the conclusions could be strengthened. The summary of uncertainties and limitations
(Section 8.5) dwells on things that "could not be quantified" due to lack of information, model
limitations, or insufficient resources. Thus, this reader was left somewhat in limbo as to the potential
magnitude of effects from mining activities. (Note that this "neutral voice" is carried throughout the
Executive Summary). Many people might interpret such statements of uncertainty as no proven
effect. My point is that probable environmental consequences of mining activities are much greater
than this report alludes to, given that consequences are likely, even if their magnitude is "uncertain."
EPA RESPONSE: We use a neutral voice throughout the document to convey the neutral
scientific perspective of this scientific assessment. We tried to convey the qualitative likelihood of
occurrence when quantitative probabilities were not obtainable. This section has been edited in
Chapter 14 of the revised draft to make the relationship between uncertainty and probability of
occurrence clearer.
DAUBLE RESPONSE: I am content with changes made to Chapter 14.
EPA FINAL RESPONSE: No response required.
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Section 8.7 is perhaps the most important section of the report. It should be comprehensive, i.e.,
cover all resources and be more quantitative. Missing from the summary were impacts on wildlife,
human culture, resident fish, and other ecological resources. Essential details from Appendices A, C,
E, F, and I, for example, could be synthesized and moved into the main report.
EPA RESPONSE: The summary of risks from the mine scenarios (Chapter 14 in the revised draft)
has been expanded to include fish-mediated risks to wildlife and culture and more numerical
results.
DAUBLE RESPONSE: Chapter 14 is a much improved version of what was formerly in
Chapter 8.
EPA FINAL RESPONSE: No response required.
Gordon H. Reeves, Ph.D.
The purpose of the report is unclear, which makes it difficult to assess. The report focused on the
potential impact of a hypothetical mine on salmon and salmon habitat in two watersheds in Bristol
Bay, AK. However, it is not clear whether the analysis was intended to be a case study of the
potential impacts of a hypothetical mine under the various scenarios presented or whether the intent
was to develop a framework for assessing mining scenarios. These are two very different objectives,
which makes it critical that the purpose be clearly stated in the beginning of the document so that
reviewers and others understand the purpose of the document. There certainly was much confusion
among members of the review panel and the people who commented on the report because of this.
EPA RESPONSE: We have clarified the purpose of the assessment in Chapters 1 and 2.
I think that the credibility of the report could be improved substantially if the analyses were
formalized and more clearly articulated and defined. The authors could consider using a decision
support process, such as a Bayesian approach (see Marcot, B.G., J.D. Steventon, G.D. Sutherland,
and R.K. McCann. 2006. Guidelines for developing and updating Bayesian belief networks applied
to ecological modeling and conservation. Canadian Journal of Forest Research 36: 3063-3074). This
would provide more transparency to any analysis and allow others to better understand how results
and conclusions were derived. Also, it would identify critical relations that should be considered and
provide insight about the consequences of not considering them. This will undoubtedly take
additional time and effort, but I believe it would be well worthwhile. Examples of where such
analysis has been done are in: (1) Armstrup et al. 2008. A Bayesian Network Modeling Approach to
Forecasting the 21st Century Worldwide Status of Polar Bears. Pages 213-268. In E.T. DeWeaver et
al., editors. Artie Sea Ice Decline: Observations, Projections, Mechanisms, and Implications.
Geophysical Monograph 180. American Geophysical Union, Washington, D.C.; and (2) Lee, D.C. et
al. 1997. Broadscale Assessment of Aquatic Species and Habitats. Vol. Ill, Chapter 4. U.S. Forest
Service, General Technical Report PNW-GTR-405. Portland, Oregon.
EPA RESPONSE: Creating a Bayesian Belief Network would require that the Agency convene
experts to subjectively estimate the probabilities of each transition in the conceptual models. In
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contrast, this assessment is intended to elucidate the risks from potential mining based on
available data and analyses of those data.
I thought one of the strongest aspects of the report were the conceptual diagrams of relations between
the various aspects of the development and operation of a mine and the components of the ecosystem
that influence salmon and their habitat (Chapter 3). These diagrams show the components of the
ecosystem, the relation among them, and how mine impacts could potentially influence given parts of
the ecosystem directly or indirectly as a result of cascading effects. They are a good first step in
developing a decision support framework, as suggested in the previous paragraph. There was,
however, little discussion about them in the text and it was not clear if or how they were used or
considered in the analyses. The authors should, at the very least, clearly identify which parts of the
networks were considered and why these particular avenues were pursued and others were not. This
would provide additional insights into potential limitations of the analyses and results.
EPA RESPONSE: The more comprehensive conceptual models presented in Chapter 6 (previously
in Chapter 3) have been broken into their relevant component parts throughout the risk analysis
and characterization chapters, to better frame the specific pathways addressed in each chapter.
If this was a case study, the report appeared to have considered available literature and reports on all
aspects of the mine, its operation and the parameters that could be affected by it. I am not familiar
with this literature so it is not possible for me to comment on the adequacy of the literature and
reports considered. Assumptions about the location and operation of the mine seemed reasonable and
the authors clearly articulated limitations of available data and other information concerning the
mine's location and operation. I found the consideration of the mine during the various phases of
development and operation and the discussion about potential development of other mines in the area
particularly insightful. Inclusion of experiences from other mining operations was also helpful in
understanding the conclusions about potential impacts of the mine and its operation over time.
Additionally, the consideration of the potential development of other mines in the area was
particularly insightful and provided a good picture, albeit not in depth, of potential cumulative effects
on aquatic resources in the Bristol Bay area.
EPA RESPONSE: No changes suggested or required
Parts of the report on the ecology of fish and aquatic ecosystems, road, and culverts - topics that I am
familiar with - were covered very well and the conclusions about potential impacts of the mine and
its operation generally seemed justified. The authors presented available data and information on fish
distribution and abundance relative to the presumed location of the various components of the mine
operation. Their analyses were appropriate but rather cursory, which is not unexpected given the
restrictions of time and available data. However, there are some additional considerations and
analyses that could be done, which I think would improve the report. I identify these in answers to
specific charge questions. Limitations of the results were readily acknowledged. However, as
mentioned above, there are additional limitations that resulted from only considering selected
potential avenues of impacts. These should be discussed in the revision.
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EPA RESPONSE: The discussion of scope (Chapter 2), endpoints (Chapter 5), and uncertainties
(throughout the risk analysis and characterization chapters) has been expanded in the revised
assessment.
The authors do a good job of summarizing the scientific literature on salmon ecosystems, roads, and
culverts. Most of this is from studies in areas outside of Bristol Bay. Interpretations of the findings
were accurate. However, there was no discussion about potential limitations on the application of the
studies to the area being considered. For example, Furniss et al. (1991) deals with roads in forest and
rangeland settings. These are very different environments than Bristol Bay, which suggests that road
impacts will likely differ. Much attention is given to "headwater streams" and their ecological
importance (p. 5-19 - 5-21). Headwater streams for the area of consideration need to be defined so
that appropriateness of the application of the literature can be better judged.
EPA RESPONSE: Headwater streams in the study area are now more fully described (Chapter 7).
Because the potential mining described in the assessment would take place in an undeveloped
area, much of the literature is necessarily from areas outside of Bristol Bay. However, to the extent
possible we used examples from representative environments. With respect to Furniss et al. (1991),
though it focuses on forest and rangeland roads, it is a seminal publication on the potential effects
of roads, particularly as they relate to salmon. The general conclusions of that paper should be
applicable to the transportation corridor described in the assessment.
REEVES RESPONSE: I agree that Furniss et al. (1991) is a seminal paper on roads and their
impacts on aquatic organisms and ecosystems. However, it deals with forest roads that are
much different in many ways from the roads considered in this assessment. The differences
should be made more explicit. Also, you should look at Lee et al. (1997 USDA Forest Service
Gen. Tech. Report. PNW-GTR-405, vol. Ill pp. 1057-1713) for additional potential impacts of
roads. Again, this pertains to forest roads and limitation of the application to Bristol Bay
should be acknowledged.
EPA FINAL RESPONSE: The information in Furniss et al. (1991) pertains specifically to
salmon, and the general conclusions of that paper should be applicable to the transportation
corridor proposed in the assessment. As suggested by the commenter, we acknowledge in the final
assessment that forest roads differ from mining roads and provide some clarifying text on this. We
also note that forested vegetation types represent 68% of the potential transportation corridor area,
and that culvert failure frequencies cited in the assessment are from modern roads, are not
restricted to forest roads, and represent the most relevant data available (Section 10.3.2.3). We also
examined Lee et al. (1997). It contained useful information on potential impacts of roads (largely
forest roads), but because much of this information had already been retrieved from other
publications we did not cite it.
A major component that is missing from the report is consideration of the potential impacts of
climate change. Climate change is identified as a factor in the conceptual model of potential habitat
and water quality effects associated with mine accidents and catastrophic failures (Fig. 3-2D).
However, I believe that it is a key factor that will have influence in all aspects of the assessment, not
just failures and natural disturbance events (Fig. 3-2C). It needs to be considered in other aspects,
such as water quality and availability. Climate change should also be included in any analysis
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because it will be critical to build it into any monitoring program that is developed in order to be able
to differentiate its impact on salmon and their habitat from potential impacts of the mine.
EPA RESPONSE: Climate change projections and potential impacts are now included in Chapter
3 (Section 3.8). It is mentioned as an important external factor in the risk analyses presented in
Chapters 7, 9, and 10, and the issue is summarized in Box 14-2.
Charles W. Slaughter, Ph.D.
The Assessment (Volume 1 - Main Report) provides a fairly comprehensive review of fisheries-
driven issues, from the perspective of salmonids. Appendices (Volumes 2 and 3) are very
informative. The high significance of the Bristol Bay watershed, specifically of the Nushagak and
Kvichak river systems, for commercial fisheries on the global scale and for sport and subsistence
fisheries at the regional and local scales, was appropriately described.
EPA RESPONSE: No changes suggested or required.
SLAUGHTER RESPONSE: OK.
EPA FINAL RESPONSE: No response required.
The potential risks and impacts are fairly and succinctly stated. Given the extremely long-term nature
of the projected Pebble project, and the irreversible changes which would be imposed to the region,
the risks seem, if anything, understated. I attribute this to the decision to focus this Assessment on
salmon and anadromous fisheries, with less attention on "salmon-mediated" impacts - i.e., effects on
indigenous culture, on wildlife other than salmon, etc.
EPA RESPONSE: No changes suggested or required.
SLAUGHTER RESPONSE: OK.
EPA FINAL RESPONSE: No response required.
Chapter 2 (Characterization of Current Condition) provides only a superficial overview of the
landscape of the Bristol Bay watersheds; a reader would preferably have access to Wahrhaftig (1965)
or Selkregg (1976), as only two (relatively dated) suggestions, to gain a more comprehensive
understanding of the region.
EPA RESPONSE: Additional information on the physical environment of the region (e.g.,
geology, vegetation, etc.), along with an expanded treatment of the regional landscape, has been
incorporated into Chapter 3 (e.g., Figures 3-4 through 3-7). Chapter 3 also includes the suggested
citations.
SLAUGHTER RESPONSE: Chapter 3 is a great improvement. The detailed maps and
discussions of the physiographic setting, hydrologic landscapes, aquatic habitats, water quality,
seismicity, and existing development of the region are comprehensive and informative.
Explanation of methodology, as in Box 3.1, Box 3.3, and throughout the entire document, is
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very helpful. This chapter now allows a reader to gain a more realistic understanding of the
Bristol Bay watershed setting.
EPA FINAL RESPONSE: No response required.
The "Water Management" section (4.3.7) seems cursory, highly generalized, and optimistic.
Statements such as "uncontrolled runoff would be eliminated"; "water from these upstream reaches
would be diverted around and downstream of the mine where practicable"; and
"Precipitation... would be collected and stored..." do not indicate actual (proposed) practices or
techniques, nor inspire confidence that actual runoff events during "normal" conditions, let alone
during hydrologic extremes (such as a rain-on-snow event with underlying soils still frozen), would
be planned for or actually managed adequately.
EPA RESPONSE: Water management measures are more clearly described and discussed in
Section 6.1.2.5 of the revised draft, and in sub-sections for the mine components in the scenarios.
The assessment no longer contains a no failure scenario, so complete water collection is not
longer assumed. Rather, standard and common practices are incorporated.
SLAUGHTER RESPONSE: The revised Section 6.1.2.5 does provide a better discussion of
water handling. Since this is all hypothetical, we must accept such statements as "If
contaminated groundwater was detected, monitoring wells would be converted to collection
wells or new recovery wells would be installed, and water from the well field would be pumped
back into the TSF or treated and released to stream channels." (p. 6-12). Easier said than done!
The last sentence on p. 6-13 states "Runoff at the port site would be pumped to the mine site in
the return water pipeline, contributing to the mine's water supply and avoiding the need for
treatment at the port." What runoff at the port site is being considered - surface runoff from
impervious surfaces at the port itself? Or does this suggest that streamflow at or in the general
vicinity of the port would be captured and utilized to augment water supply at the mine? If the
latter, then a separate evaluation of hydrologic resources, and permitting, would be necessary.
EPA FINAL RESPONSE: The sentence refers to runoff from disturbed areas at the port site.
Para. 6.2.2.3 - The generality that water released to streams "would comply with permitted
discharge requirements", but may differ from "natural stream water" in actual characteristics,
locale, rates, or timing, would not be reassuring to issues of salmon sustainability - based on
information provided elsewhere in the assessment concerning extreme sensitivity of salmon
(and other organisms) to seemingly minor or very localized water characteristics.
EPA FINAL RESPONSE: The effects of chemicals are discussed in Chapter 8. However, we know
of no method for determining whether a particular change in water chemistry would result in
changes in stream fidelity of returning salmon.
Para. 6.2.2.3 - The last sentence summarizes percentage of water to be reintroduced to
streams; it would also be appropriate to emphasize that this envisions LOSS of 26%, 60%, and
30% of total flows under the three scenarios.
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EPA FINAL RESPONSE: Chapter 7 deals with the conversion of these losses to stream/low after
accounting for other demands and sources; it would not be appropriate to nuike these
generalizations.
Perhaps I missed it, but I found no acknowledgment of the potential presence of or consequences of
perennially frozen soils - permafrost - in the Bristol Bay watershed, or more specifically in the
Pebble ore deposit locale or the proposed transportation corridor. Selkregg (1976), Fig. 136, shows
soils of the Pebble locale as INT/2g, INT/1 g - HYP, or SOU/2g-HYP - that is, well-drained gravelly
soils (INT) or well-drained acidic soils (SOU) with interspersed peaty, poorly-drained shallow
discontinuous permafrost. There is abundant literature on the influence of permafrost on engineered
structures, roads, hydrology, etc. Even if the bulk of the terrain involved in the proposed Pebble
mine, road and infrastructure project is founded on well-drained gravelly soils, any interspersed
permafrost-underlain terrain can prove problematic in terms of landscape stability, potential erosion,
and consequent structural, engineering, hydrologic and water quality issues. See Specific
Observations for a few suggested references in.
EPA RESPONSE: We have expanded our characterization of the soils and permafrost distribution
in the Bristol Bay watershed in Chapter 3 of the revised assessment. As part of this expansion, we
summarize the nature and distribution of permafrost by physiographic region.
SLAUGHTER RESPONSE: The inclusion of detailed maps and information from Selkregg
(1974) is appreciated. Figure 3.4 now acknowledges the possibility of isolated permafrost
presence in both the Pebble locale and through the entire proposed transportation corridor.
Note that the presence of perennially frozen ground (permafrost) is not necessarily detrimental
to construction; fine-grained (silts) high ice content frozen soils pose major problems, but
coarse-grained soils with low frozen water content can be stable upon thawing.
EPA FINAL RESPONSE: No response required.
While there is extensive discussion of a proposed transportation corridor, there was no mention of
construction of a major airfield. A project of this magnitude would undoubtedly require development
of a facility in close proximity to the mine(s) capable of handling CI 30 and commercial jet passenger
and cargo traffic, at least to the 737 class, if not 747.1 don't know what the footprint for such an
airfield would be, but it would be substantial, and with requisite roads, fuel handling, etc., would be a
major project in itself. This would seem to be a logical component of a comprehensive assessment of
the potential Pebble project.
EPA RESPONSE: The scope of the assessment has been clarified in Chapter 2, and construction
and operation of a new airport is considered outside the scope of the assessment. We would expect
that a full evaluation of any future mining permit applications and subsequent National
Environmental Policy Act Environmental Impact Statements would consider these effects if a new
airport is proposed.
SLAUGHTER RESPONSE: Again - if this assessment does not or cannot address the full suite
of probable consequences of the PLP project, what agency or entity does have that
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responsibility? Is this just putting off the responsibility for truly comprehensive evaluation to
(presumed) future NEPA review?
EPA FINAL RESPONSE: If the Pebble Limited Partnership decides to move forward with a
proposed mine, it would need to apply for a Clean Water Act Section 404permit from the U.S.
Army Corp of Engineers (among other permits). Any permit decision by the U.S. Army Corp of
Engineers would need to comply with the National Environmental Policy Act, and a project of this
scope would presumably require development of an Environmental Impact Statement.
As noted in the Executive Summary, the Assessment does NOT address several major components of
the (hypothetical) Pebble project, including electrical generation and transmission, a deep-water port,
or "secondary development" and associated infrastructure which would follow an initial mining
project. A truly comprehensive analysis should incorporate full analysis of these aspects. This
Assessment is thus inadequate in terms of considering potential broader consequences for the Bristol
Bay watershed system.
EPA RESPONSE: The scope of the assessment has been clarified in Chapter 2, and we have
stated throughout the text that areas outside of scope may also be important factors.
SLAUGHTER RESPONSE: Again - if this assessment does not or cannot address the full suite
of probable consequences of the PLP project, is this just putting off the responsibility for truly
comprehensive evaluation to (presumed) future NEPA review?
EPA FINAL RESPONSE: See response to previous comment.
John D. Stednick, Ph.D.
The purpose of the document is not clearly stated in either the Executive Summary or the
Introduction. Need to specifically identify the document as an environmental risk assessment. There
is a misconception that it is a CWA Section 404(c) review, rather than an environmental risk
assessment. The document should have the utility to inform future users of the risk to the watershed
resources from mining activities in the watershed. The assessment can be used by others for decision
making purposes, and includes current and appropriate methodologies for all identified stressors,
such that study results can be duplicated. And all stressors are evaluated to a similar level of detail.
EPA RESPONSE: Additional information on both the purpose of the assessment and ecological
risk assessment (ERA) in general has been added to Chapters 1 and 2, as well as the Executive
Summary. Section 1.2 includes information about the use of the assessment. The assessment has
been reorganized into two major sections (problem formulation, risk analysis and
characterization) to clarify where different chapters fall in the typical ERA process.
The document characterizes the potential environmental effects of an open pit mine over a copper
porphyry complex in southwest Alaska using a hypothetical mine design based on similar ore
deposits and mine complexes elsewhere. Proposed mine activity has been identified by the Pebble
Limited Partnership though Northern Minerals Dynasty and should be cited to improve applicability
of the risk assessment. Furthermore, a wider range of mining scenarios should be developed and
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analyzed for environmental risk assessment. Environmental consequences were estimated by the
environmental risk assessment model approach for both 'no-failure' and 'failure' scenarios. The
Executive Summary concluded that the effects of mine development resulted in significant salmon
habitat losses. Potential effects on other aquatic species were not identified. The assessment
evaluated environmental risks under the development and closure scenarios using large catastrophic
events and did not include smaller, yet more frequent excursions or system failures. Nor did the
assessment look at the full range of mine development scenarios, specifically what are the risks
associated with a smaller underground operation?
EPA RESPONSE: The assessment used the Pebble deposit and its characteristics, as described by
Northern Dynasty Minerals in the Ghaffari et al. (2011) report. That report is cited extensively in
both the original review draft and the revision. A median-sized mine (based on worldwide mine
sizes) has been added to the scenarios in the revised assessment. Because the number of potential
failures is extremely large, it is necessary to choose a representative set of failure scenarios. The
final document includes more failure scenarios (e.g., diesel pipeline failure, quantitative water
treatment failure, and refined seepage scenarios) and explains why the particular failure scenarios
were chosen. Underground mining is a potential for any mining site that has high-quality ore
located at depth, but sources ofpotential impact considered in scope for the assessment would be
common for either a surface or an underground mine (e.g., water withdrawal, tailings dam
failure, water treatment failure, seepage, etc).
The conclusions of the Executive Summary are strongly worded (e.g., pages ES 13 to 24), yet the
uncertainties presented later in the report make the strong conclusions tenuous. An expanded
discussion of uncertainties and limitations may temper those 'conclusions.'
EPA RESPONSE: Each risk analysis chapter of the revised assessment now includes an
uncertainty section. The Executive Summary has been rewritten to reflect the revised assessment
text.
Site characterization/description of current conditions is too brief. More information is needed for a
full site characterization. Any reader unfamiliar with the setting would not fully understand the
physical, biological, or ecological inventories and linkages in the study area. The risk assessment of
failure and no failure are covered in Chapters 5 and 6 with varying levels of detail and substantiation
of conclusions. Statements like "salmon is important in the human diet, thus a salmon loss affects
human health" seem like a weak argument, especially when additional information in the appendix
suggests a larger effect.
EPA RESPONSE: Additional information on the region's physical environment has been added to
Chapter 3 (e.g., Figures 3-4 through 3-7), and additional information on the region's biological
communities from Appendices A through C has been incorporated into the main text. The purpose
of the appendices—to provide the detailed background characterization necessary for the
ecological risk assessment—has also been clarified in Chapter 2.
The Pebble Limited Partnership has a large environmental baseline database (EBD), but does not
appear to be cited or used. Justification for the inclusion or exclusion of these data should be made.
Reference is often made to various data, but these data were not presented.
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EPA RESPONSE: The Pebble Limited Partnership's (PLP's) EBD was used and cited more than
70 times in the original draft and even more in the revised assessment. Data from the PLP EBD
concerning hydrology, water quality, and biology of the streams on the site and along the
transportation corridor have been extensively incorporated into the assessment in the analyses in
Chapters 7 through 11. However, to the extent possible, the assessment relies on peer-reviewed
literature.
Review and revise the water balance section, which would include: 1) generating a diagram or
conceptual figure similar to page 3-7 to illustrate the potential effects of mine construction and
operation on surface and groundwater hydrology; 2) developing a quantitative water balance for
surface and groundwater resources; 3) incorporating seasonality (especially assessing the role of
frozen soil); 4) identifying hydrologic processes and their associated values (e.g., mm/yr) for each
component of the water balance in time and space, and then incorporating into a landscape
characterization; 5) demonstrating the interconnectedness of groundwater, surface water, and the
importance to fish habitat and stream productivity; 6) evaluating the influence of global climate
change on these hydrologic processes and rates; and 7) using this characterization demonstrate the
expected hydrologic modification associated with the mine scenarios and infrastructure development
and closure scenarios.
EPA RESPONSE:
1) We included schematics to illustrate potential effects of mine construction and operation of
surface hydrology, including effects via groundwater changes (e.g., Figure 6-5, Figures 6-8
through 6-10).
2) Our water balance focuses on surface water hydrology (including interactions with
groundwater). A comprehensive groundwater hydrology water balance is beyond the scope of the
assessment.
3) The core of our analyses is an annual water balance, but we have maintained the simple
approach to seasonality used in the first draft of the assessment.
4) We have adopted a basic approach to representing the dominant hydrologic processes at the
mine site; a comprehensive representation of all hydrologic processes is beyond the scope of this
assessment.
5) Throughout the assessment, we have identified and quantified the interconnectedness of
surface water, groundwater, and their importance to fish habitat and stream productivity.
6) A section on potential climate change effects has been added to Chapter 3.
7) We have used our updated water balance and hydrologic modeling approaches to estimate
expected responses of mine scenarios, infrastructure development and closure scenarios.
One common theme that emerged from the public comment session during the peer review meeting
in Anchorage, AK was the questioning of the document timing, from draft release to the public
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comment period to the unannounced completion of a final document. These concerns should be
addressed in the new document.
EPA RESPONSE: This type of contextual information is not directly relevant to the ecological
risk assessment, but clarification of the timing and use of the assessment has been included in
Chapter 1.
Roy A. Stein, Ph.D.
Accuracy of Presentation. Overall, I was pleased with the accuracy of the presentation. Typically,
peer-reviewed citations to the scientific literature were cited as supportive documentation for most all
of the factual information (though the well-developed appendices, e.g., Appendix E: Economics;
Appendix I: Mitigation, could be used to far better advantage, see below). Unfortunately, in the main
report, many data are missing, especially with regard to salmonid populations, their diversity (both
across species wand within species across populations), their relative population sizes, their
distribution across the watershed, their vital rates (i.e., recruitment, growth, and survival across life
stages), and to what extent the Pebble Mine and its associated activities will reduce these populations
(for there is no question they will indeed be reduced through both the mine footprint and all allied
operations in the drainage), both through impacts on individual populations and the overall
production of salmonids (and other fishes) in the Bristol Bay watershed.
EPA RESPONSE: We now include figures showing reported salmon species distributions and
salmon diversity by HUC-12 watersheds across the Nushagak and Kvichak River watersheds
(Figures 5-3 through 5-8). Information on population sizes and vital rates are limited for the
region, but are reported where known. Due to lack of comprehensive estimates of limiting factors
across the impacted watersheds, population-level effects could not be quantitatively estimated
except for the most severe cases, where total losses of runs could be reasonably assumed
Whereas I am relatively confident about accuracy of the fisheries information included, I cannot
comment in detail regarding the accuracy of the mining information or impacts on the Native
Alaskan cultures (though the impact of the mine on this culture was confined to fish-mediated
effects). That a Native Alaskan culture 4,000 years old is in jeopardy bothers me greatly; might this
complete subsistence way of life in the Bristol Bay watershed be eliminated with the exploitation of
the copper via open-pit mining? In turn, what impacts might there be on subsistence users, other than
Native Alaskans? Even though these sections seemed reasonably well presented (with caveats above)
and appropriately supported with citations, they do lie beyond my expertise.
EPA RESPONSE: No changes suggested or required
My concerns about the document revolve around issues that were not considered, i.e., Global Climate
Change, "In Perpetuity" issues, groundwater-surface water exchange issues (owing to missing
information), impacts of Routine Mine Operations in a more realistic setting, the seemingly undue
influence on a failure of the Tailings Storage Facility, and other somewhat more minor issues (see
comments below). With any revision, the authors should include this information by eliminating
redundancy (see below), thereby not increasing document length.
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EPA RESPONSE: We have thoroughly revised our approach to quantifying hydrologic responses
to the mine scenarios. We explicitly include groundwater-mitigated effects on surface waters.
Climate change projections and potential impacts are now included in Chapter 3 (Section 3.8), and
are considered as important external factors in the risk analyses as summarized in Box 14-2. See
responses to the commenter's specific comments and to Dr. Stednick's hydrologic comments
below.
Clarity of Presentation. Generally speaking, I believe that the writing was intelligent, reasonably
insightful, and, more specifically, on task. One significant criticism with regard to the presentation
revolves around the organization of the document. As detailed below, the organizational scheme lent
itself to redundancy, from the Introduction through the various chapters to the Integrated Risks
Characterization chapter. Owing to this redundancy, the report is likely too long by about 20% and
any revision and shortening should serve to improve its impact on readers.
EPA RESPONSE: The assessment has been reorganized to eliminate redundancy and help clarify
the structure of the document.
The conceptual block and arrow diagrams (pages 3-7 to 3-11) were quite instructive. They nicely
demonstrate the interactions that occur within this mining scenario. The main report would be much
improved if text were to review this set of interactions. Clearly, a tremendous amount of time, effort,
and thought went into generating these diagrams and it is indeed a true shortcoming of the main
report that essentially no text was spent stepping through these diagrams.
EPA RESPONSE: Additional information on the use of conceptual models in the assessment has
been incorporated into Chapter 2. The more comprehensive conceptual models presented in
Chapter 6 (previously in Chapter 3) have been broken into their relevant component parts
throughout the risk analysis and characterization chapters, to better frame the specific pathways
addressed in each chapter. Additional conceptual models considering impacts on wildlife, Alaska
Native populations, and cumulative effects of multiple mines have been added to Chapters 12 and
13.
Soundness of Conclusions. The conclusions were well supported, where there were published data to
support them. Many statements that could be interpreted as conclusions were often more qualitative
than desirable in a review document such as this one, owing to the lack of information (percent of
salmonids lost owing to routine mine operations, impacts of mining and the transportation corridor
on wetlands, extent of groundwater-surface water disruptions, just to name a few). Consequently, the
soundness of the conclusions are somewhat compromised by a lack of information.
EPA RESPONSE: No changes suggested or required
In addition, what would aid readers is a succinct statement of the purpose (risk assessment? impact
on water quality and then through to fishes and beyond? etc.) and scope (relatively narrow impact of
the mine on salmonids and ripple effects out from there) of the document early in the initial chapter.
In so doing, both reviewers and readers will be informed as to the direction of the document and thus
better informed as they move through the document.
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EPA RESPONSE: Additional information on both the purpose of the assessment and ecological
risk assessment in general has been added to Chapters 1 and 2, as well as the Executive Summary.
Finally, a portion of the public testimony complained about the process, specifically about the time
allowed for document review, the data reviewed, the validity of the hypothetical mine, etc. Though I
found most all comments to be somewhat disingenuous, I still would offer the following advice:
Provide a section upfront that deals with process issues surrounding the review, i.e., explaining the
constraints under which EPA was operating; without a section like this, complaints, such as those
described above (coming from just one segment of the public), will go unanswered.
EPA RESPONSE: Chapters 1 and 2 now clarify the purpose of the assessment and document how
public participation was incorporated into the process (e.g., Box 1-1).
William A. Stubblefield, Ph.D.
The document, "An Assessment Of Potential Mining Impacts on Salmon Ecosystems of Bristol Bay,
Alaska," is a well-written, comprehensive document that employs a risk assessment-type approach to
an a priori evaluation of potential environmental effects on the ecosystem and potential receptor
species (e.g., salmon) that may be affected by a potential copper mine located in the Bristol Bay area
of Alaska. This document is somewhat unique, in that no actual mine has been proposed at the
location and few site- or project-specific data are available. Therefore, no specific information about
development plans and potential operational and closure activities associated with the mine are
available. Rather, the authors have attempted to develop a hypothetical mine and attempted to assess
possible environmental effects associated with mine development, operation, and closure. Although
interesting, the potential reality of the assessment is somewhat questionable. It is also unclear why
EPA undertook this evaluation, given that a more realistic assessment could probably have been
conducted once an actual mine was proposed and greater detail about operational parameters
available. The approach taken in the document attempted to be comprehensive and evaluated a
variety of scenarios that may affect aquatic resources in the Bristol Bay region. Given the importance
of salmon populations in the area, both from a financial and societal perspective, it is important that a
comprehensive evaluation of potential environmental effects associated with mine development and
operations be conducted. The authors have attempted to conduct such a comprehensive evaluation
and have attempted to quantify (to the extent possible) the probability of adverse effects occurring.
Implementation of this approach is proper, and with the correct data, can provide a comprehensive
evaluation of potential environmental effects. Unfortunately, because of the hypothetical nature of
the approach employed, the uncertainty associated with the assessment, and therefore the utility of
the assessment, is questionable.
EPA RESPONSE: We respectfully disagree that the hypothetical nature of the approach
compromises the utility of the assessment. All mining plans are hypothetical They change in
response to the results of assessments, regulatory requirements, public input, and unforeseen
conditions and events. They cease to be hypothetical only after the mine is closed At every step in
the process, assessments of the current plan are useful even though plans will change. This
assessment is based largely on a preliminary plan, published by Northern Dynasty Minerals
(Ghaffari et al. 2011). Although layout of mining components in a future mine plan may differ
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somewhat from the preliminary plan or the assessment scenarios, the main components of mining
would remain the same for open-pit mining (and underground mining would face the same waste
issues).
STUBBLEFIELD RESPONSE: It would appear that on this topic the reviewer and the US
EPA authors are likely to continue to disagree. The hypothetical nature of the approach
presented in the original assessment document was sufficiently vague to the degree of
confidence in the assessment may limit its utility to risk decision-makers due to the high degree
of uncertainty associated with the evaluation. By increasing the information upon which
environmental exposure concentrations and environmental effects concentrations are estimated
and taking into account site-specific environmental conditions, a more robust assessment with
less uncertainty can be developed. This does not suggest that the original "screening level"
approach has no utility; it merely suggests that the degree of uncertainty associated with the
assessment may not have been sufficient to provide risk decision-makers with sufficient
information upon which to make long-term project decisions.
EPA FINAL RESPONSE: The purpose of the assessment is to determine the significance of the
region's ecological resources and evaluate potential impacts of large-scale mining on these
resources. We believe that the assessment has met these goals and provides sufficient technical
information and analyses to inform future decision making.
A variety of uncertainties and data needs were identified as a result of this effort and this alone may
provide sufficient value to justify the document and approach. For example, the authors note that
there is not an abundance of chronic toxicity data considered in deriving the EPA's ambient water
quality criteria for copper and that there is an uncertainty associated with whether the biotic ligand
model (BLM) adequately protects species of concern in Bristol Bay. It would seem appropriate for
EPA (perhaps in concert with industry) to develop the data to improve our understanding of copper
toxicity and to ensure that regulatory standards are, in fact, appropriate for their intended use. A
substantial body of data evaluating copper chronic toxicity has been developed by the copper
industry as a result of regulatory requirements driven by the European REACH regulations. It may be
beneficial for EPA to examine these data, thus resulting in a reduction in any uncertainty associated
with the evaluation of environmentally acceptable metals concentrations. It should also be noted that
similar datasets and biotic ligand models exist for number of other metals that may be of concern at
the Bristol Bay site.
EPA RESPONSE: We have examined the EU's 2008 Voluntary Risk Assessment of Copper (the
relevant REACH document). Although they do derive a chronic species sensitivity distribution, it is
because of the way they include and aggregate data, rather than the generation of new data. In
particular, they have no data for sensitive aquatic insects, so the EU does not resolve that problem.
The BLM was used for copper because copper is the contaminant of greatest concern and because
the copper BLM has been approved by EPA's Office of Water. Other metals with BLMs, such as
zinc and nickel, occur at much lower levels in leachates.
STUBBLEFIELD RESPONSE: The EU's copper voluntary risk assessment does, in fact,
include additional data than that considered in the US EPA's original copper Ambient Water
Quality Criteria. For example, data for freshwater mussels represent a "new" species that was
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included in the EU's document. The assessment authors are correct, however, in that new data
are not available for additional insect species, especially representatives from Ephemeroptera,
Plecoptera or Trichoptera orders (i.e., EPT species). Field population data suggest that these
organisms may have greater sensitivity to the effects of copper than those currently considered
in the existing species sensitivity distribution. Currently no standardized (i.e., OECD, ASTM or
EPA) laboratory test methodologies exist for conducting chronic toxicity test with EPT species.
US EPA may want to consider the possibility of conducting or funding a research program
aimed at the development of chronic tests methodologies for these species in order to assure
that they are adequately protected by AWQC.
EPA FINAL RESPONSE: The EU's freshwater nuissel data are not new (1993,1994 and 1997).
EPA has funded research in addressing test methods for aquatic insects.
One suggestion that would improve the document is that EPA should include a basic description of
the risk assessment process and the relationship between the risk assessor and the risk manager, i.e.,
the decision maker. They must include a discussion of why the assessment is being conducted, the
decisions that will be informed, and what information they need from the risk assessor.
EPA RESPONSE: Additional contextual information for the assessment has been included in
Chapter 1, and additional information on ecological risk assessment has been incorporated into
Chapters 1 and 2. The assessment has also been restructured into problem formulation and risk
analysis and characterization sections, to make the assessment's structure as an ecological risk
assessment clearer.
STUBBLEFIELD RESPONSE: Substantial improvements were made in the revised
assessment to address the concerns raised in my initial review comments. Through a
combination of revision, reorganization, and expansion in Chapters 1 and 2, the authors have
provided the appropriate background and description of the approach used in the preparation
of this assessment.
EPA FINAL RESPONSE: No response required.
Taken from the USEPA's Guidelines for Ecological Risk Assessment (EPA630/R-95/002F; April
1998). Note 2nd sentence re: the role of the risk manager.
"2.1. THE ROLES OF RISK MANAGERS, RISK ASSESSORS AND INTERESTED PARTIES
IN PLANNING
During the planning dialogue, risk managers and risk assessors each bring important
perspective to the table. Risk managers, charged with protecting human health and the
environment, help ensure that risk assessments provide information relevant to their
decisions by describing why the risk assessment is needed, what decisions it will influence,
and what they want to receive from the risk assessor. It is also helpful for managers to
consider and communicate problems they have encountered in the past when trying to use
risk assessments for decision making.
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In turn, risk assessors ensure that scientific information is effectively used to address
ecological and management concerns. Risk assessors describe what they can provide to the
risk manager, where problems are likely to occur, and where uncertainty may be
problematic. In addition, risk assessors may provide insights to risk managers about
alternative management options likely to achieve stated goals because the options are
ecologically grounded. "
EPA RESPONSE: Section 1.2 in the revised assessment discusses uses of the assessment.
STUBBLEFIELD RESPONSE: I concur, the revised Chapter 1 adequately describes the
purpose and use of the assessment.
EPA FINAL RESPONSE: No response required.
Dirk van Zyl, Ph.D., P.E.
Planning and designing a large mine, and especially one in a sensitive environmental setting such as
Bristol Bay, involves many iterations before a design evolves that is provided for further public
considerations. The EPA elected to use a design, developed for Northern Dynasty Minerals Ltd. in a
preliminary assessment prepared following the guidance of National Instrument (NI) 43-101, as the
basis for extensive evaluations in their risk assessment. The resulting risk assessment can be at best
characterized as preliminary, screening level, or conceptual. There are both technical and process
issues that must be addressed before this risk assessment can be considered complete or of sufficient
credibility to be the basis for a better understanding of the impacts of mining in the Bristol Bay
watershed.
EPA RESPONSE: We respectfully disagree that the hypothetical nature of the approach
compromises the utility of the assessment. All mining plans are hypothetical. They change in
response to the results of assessments, regulatory requirements, public input, and unforeseen
conditions and events. They cease to be hypothetical only after the mine is closed. At every step in
the process, assessments of the current plan are useful even though plans will change. This
assessment is based largely on a preliminary plan, published by Northern Dynasty Minerals
(Ghaffari et al. 2011). Although layout of mining components in a future mine plan may differ
somewhat from the preliminary plan or the assessment scenarios, the main components of mining
would remain the same for open-pit mining (and underground mining would have the same waste
issues).
With respect to the proposed transportation corridor, we note in the assessment that "Although
this route (the one proposed in the EPA scenario) is not necessarily the only option for corridor
placement, the assessment of potential environmental risks would not be expected to change
substantially with minor shifts in road alignment. Along any feasible route, the proposed
transportation corridor would cross many streams, rivers, wetlands, and extensive areas with
shallow groundwater, including numerous mapped (and likely more unmapped) tributary streams
to Iliamna Lake (Figures 10-1 and 10-2)."
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There are a number of items that require specific attention prior to finalizing the report. While my
comments below provide further details, from a global perspective the following aspects must be
addressed:
• A better sense about the range of impacts from a mining project that use not only different
technologies but also different lay-out options in its development than that assumed in the
EPA Assessment;
• More attention to the use of appropriate order of magnitude numbers reflective of the quality
of data, e.g. less accuracy is obtained when 1:62,500 scale vs. 1:12,500 scale maps are used;
• Correction of errors associated with misquoting and incorrect use of information in the
literature; and
• A critical review and rewrite of the Executive Summary to reflect the tone, terminology,
information sources and results of the main body of the report. One example of an error and
one of inconsistent terminology are:
o Page ES-10: "Thus, the mine draws on plans published by the Pebble Limited
Partnership (PLP)", this is incorrect as the plans that were used were prepared for
Northern Dynasty Minerals Ltd.
o Page ES-10: "... our scenario reflects the general characteristics of mineral deposits in
the watershed, contemporary mining technologies and best practices..." The main
body of the report emphasizes on a number of occasions (such as Page 4-1,4-17) that
"Our mine scenario represents current good, but not necessarily best, mining
practices".
My comments contained above and below are based on a single review of the report, i.e. contractual
time constraints were such that I could not afford a second review of the report. It is therefore
possible that there are other errors remaining in the report that I did not observe in my review. It is
therefore recommended that after making these corrections and edits that EPA subject the report
again to a rigorous independent review.
EPA RESPONSE: The scenarios evaluated are meant to represent those expected to be present as
typical for mining porphyry copper deposits of this type. Although layout of mining components at
a site may differ somewhat from what we present in the scenarios, the main components of mining
would remain the same for open-pit mining (and underground mining would have the same waste
issues). Therefore, no change is required for technologies presented in the original assessment,
and we have noted in the assessment that there could be different layouts than what we have
presented
Errors and inconsistencies in sections of the document are noted and have been corrected in the
revised assessment. With regard to the terminology of "best", "good", or other terms for the
practices used, what was intended to be conveyed is that we have assumed modern mining
technology and operations. The terms are qualitative when generally interpreted, or have a
regulatory meaning (for example, "best management practices" applies to the setting of
stormwater control, but not specific to mining sites), and thus we have eliminated their use in the
revised assessment. The assessment is being re-reviewed by the external expert reviewers.
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Phyllis K. Weber Scannell, Ph.D.
My comments on EPA's draft document, An Assessment of Potential Mining Impacts on Salmon
Ecosystems of Bristol Bay, Alaska, follow a three-day peer review meeting in Anchorage, AK. On the
first day of the meeting, the Peer Review Team heard testimony on the importance of the resources in
the potentially affected area and on possible effects of mineral development on the fish and wildlife
resources and on local residents. The issues of mineral development are complex, particularly with
respect to protecting the environment and the interests of local residents. I understand and appreciate
the complexity of these issues; however, the charge of the Peer Review Team is to review EPA's
draft document, An Assessment of Potential Mining Impacts on Salmon Ecosystems of Bristol Bay,
Alaska, and offer suggestions to strengthen the report. My comments, included below, are focused
on the accuracy and thoroughness of the draft document.
The document "An Assessment of Potential Mining Impacts on Salmon Ecosystems of Bristol Bay,
Alaska" and the accompanying appendices provide an in-depth and thoroughly documented
description of the environment and resources of the areas under consideration for mineral
development, although not in the entire Bristol Bay region. Appendices A and B are particularly
thorough in describing the salmon and non-salmon fishes in the region; the discussion of species
specific fish sensitivities to certain toxicants adds important information for future consideration of
project development.
EPA RESPONSE: No change suggested or required.
The assumptions for developing and operating large porphyry copper mine may not be aligned with
features of a future mining project. Too much emphasis was placed on effects of catastrophic
failures, such as failure of a tailings dam or pipeline, and too little emphasis on the need to identify
and control seepage water, run-off from PAG (potentially acid generating) and NAG (not acid
generating) waste rock areas, and water treatment.
EPA RESPONSE: Because the number ofpotential failures is extremely large, it is necessary to
choose a representative set offailure scenarios. The revised assessment includes more failure
scenarios (e.g., diesel pipeline failure, quantitative water treatment failure, and refined seepage
scenarios) and explains why the particular failure scenarios were chosen.
The document discussed effects of dewatering on suppressing stream flows and groundwater inputs
but did not consider effects of the discharge of treated wastewater. The section on hydrology
illustrates the need for more complete hydrologic information before any project development. The
need for bypassing all clean water sources around a development site should be addressed.
EPA RESPONSE: The revised assessment more clearly presents that clean water would be
diverted around the site, retained in settling ponds, and released following settling and/or
treatment, if required Discharge of treated wastewater is analyzed and discussed in greater depth
in the new Chapter 8 (Water Collection, Treatment, and Discharge). We agree that detailed
hydrologic information is critically important for responsible project development, and additional
hydrologic information may be available and/or acquired for any future mine plan in this
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watershed. We have updated our hydrologic analyses to include some aspects of surface
water/groundwater interaction in the mine scenarios.
As stated in my response to charge questions, I believe that the two most important questions for
mineral development in this region are: can a mine be designed and operated for future closure? and,
if not, is it acceptable to develop a large porphyry copper mine in a region of high value salmon
habitat that will essentially require perpetual treatment? These two questions must be addressed when
considering protection of the fish, wildlife, and human resources of the region.
EPA RESPONSE: We agree that these are important questions to be addressed but they are risk
management, not risk assessment, questions. The purpose of the assessment is to evaluate risks to
the salmon fishery from large-scale mining. Risk management decisions will be made during the
permitting process. No changes to the assessment were made in response to this comment.
Paul Whitney, Ph.D.
Response (with a wildlife perspective) - The main document is fish centric and it should be, given
the importance of salmon in the Bristol Bay ecosystem. Wildlife (aquatic, wetland and upland
species) and terrestrial resources related to potential mine and haul road impacts are glossed over.
The summary write ups for several species of wildlife (Appendix C) are very good regarding natural
history and some potential impacts. Information in Appendix C tends to focus on the proposed mine
site and less on the proposed haul road and game management units in the Kenai Mountains.
EPA RESPONSE: Direct effects on wildlife and terrestrial resources are outside the scope of the
assessment, as clarified in Chapter 2. Effects on wildlife are now treated in Chapter 12.
WHITNEY RESPONSE: The clarification provided in Chapter 2 is not tight. For example, the
statement "We focus on freshwater habitats, because the most exceptional ecological feature of
the Bristol Bay watershed is its fish populations" (p 2-5, para 3, lines 2 and 3) is subjective at
best and is in the eye of the beholder. What is clear to me is that the decision not to consider
direct impacts to wildlife is political and relates to the Clean Water Act. Asserting that
"exceptional" has an ecological or scientific meaning and explains why direct impacts on
wildlife are not considered confuses rather than clarifies.
EPA FINAL RESPONSE: The assessment addresses fish-mediated risks to wildlife, but direct
effects ofpotential mining on wildlife are outside the scope of assessment (Chapter 2). Appendix C
provides useful information for future evaluation of direct effects on wildlife from large-scale
mining.
USFWS RESPONSE: We acknowledge the comment regarding quality of Appendix C.
Information in Appendix C is intended to focus on the entire Nushagak and Kvichak River
watersheds to the extent that data exist. To the extent that a potential mining-related road is within
the Nushagak and Kvichak River watersheds, information about selected wildlife species is
included in Appendix C. Information about selected wildlife species on the Cook Inlet side of the
Chigmit Mountains is not included in the wildlife report. The Kenai Mountains are not in the
Nushagak and Kvichak River watersheds.
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WHITNEY RESPONSE: Appendix C is what it is but the above response is circular. Direct
impacts on wildlife are outside the scope of the assessment so it really doesn't matter that
wildlife resources along the entire road are not discussed. Is one to assume that impacts along
the road segments outside the Bristol Bay watersheds are not significant? The circular
reasoning in the above responses is of little consequence here but circular reasoning in other
responses is more of a concern.
EPA FINAL RESPONSE: The portion of the road outside the Bristol Bay watershed is outside of
the scope of the assessment for all endpoints. Therefore, no judgment is made concerning the
significance of effects outside the watershed No circular reasoning is employed.
A variety of authors have obviously contributed to the documents and it appears that the direction
given to them or their interpretation of goal statements varies. For example, if one of the goals of the
assessment is to evaluate the risk to wildlife due to risk to fish (Executive Summary, page 1, last
para) it's not clear why so much verbiage in Appendix C (wildlife) is devoted to species such as
caribou that are not closely associated with fish. Information in Appendix C could be used to assess
direct impacts if the scope of the assessment is expanded. For example, if the goal is to assess the
impact of potential mining on the ecosystem (see Executive Summary page 1, para 1), the
information on caribou in Appendix C is more relevant. The apparent diversity of goal statements
cited in the main assessment gives mixed messages regarding the clarity of the presentation (see
more detailed discussion below).
EPA RESPONSE: As the commenter notes, the scope of the assessment is focused on potential
risks to salmon from large-scale mining and salmon-mediated effects to indigenous culture and
wildlife. EPA agrees with the commenter that direct effects on wildlife are likely to be important
and that Appendix C (now a stand-alone USFWS document) provides useful information for an
evaluation of direct effects on wildlife from large-scale mining. We would expect that a full
evaluation of any future mining permit applications and subsequent National Environmental
Policy Act Environmental Impact Statements would consider these direct effects. The revised
assessment acknowledges the potential for direct effects on wildlife as well as risks due to fish, but
states that these effects are outside the scope of the assessment.
USFWS RESPONSE: The scope ofAppendix C is broader than that of EPA's assessment because
it is a USFWS document prepared to serve various purposes, including statewide or regional land
use planning, completion of environmental documentation for permitting of development projects,
and activities related to Landscape Conservation Cooperatives in Alaska. The former Appendix C
is now a separate USFWS report which is cited by the assessment but is no longer an appendix of
the assessment. However, information in the USFWS report document has been used by EPA to
provide a more complete assessment of overall watershed resources at risk due to potential mining,
and to strengthen the assessment of risks to wildlife from fish-mediated effects of the mine in the
revised assessment.
WHITNEY RESPONSE: Please reread the last sentence in the above Response. What does it
mean that risks due to fish are outside the scope?
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EPA FINAL RESPONSE: The conmienter has misread the sentence, which we acknowledge
could have been written more clearly. Direct effects on wildlife are out of scope, and effects on
wildlife mediated by fish are within scope (as stated in Chapter 2).
The charge question related to wildlife asks for an evaluation of the risk to wildlife due to the risk to
fish. If the risk to fish cannot be quantified because there is little or no demographic information,
then any evaluation of risk to wildlife can't be quantified and must be qualitative. Merely stating that
a qualitative increased risk for fish will also result in a qualitative increased risk for wildlife is not
adequate. I am not satisfied with such an obvious and general conclusion. I do not understand why
the scope of the main document is limited to an indirect evaluation of fish-caused risk to wildlife.
The following responses to charge questions leans more toward an ecosystem evaluation that
includes, not only risk of fish to wildlife, but also risk of direct wildlife and vegetation loss to fish
and other direct risks to wildlife, such as noise and human presence.
EPA RESPONSE: We acknowledge that there are numerous potential direct risks to wildlife from
large-scale mining. However, this evaluation is outside of the scope of the assessment. The revised
assessment provides a clearer explanation of the reasons for its defined scope.
WHITNEY RESPONSE: See other responses in this document.
EPA FINAL RESPONSE: No response required.
3.3 Charge Question 1
The EPA '.v assessment focused on identifying the impacts ofpotentialfuture large-scale
mining to the fish habitat and populations in these watersheds. The assessment brought
together information to characterize the ecological, geological, and cultural resources of
the Nushagak and Kvichak watersheds. Did this characterization provide appropriate
background information for the assessment? Was this characterization accurate? Were
any significant literature, reports, or data missed that would be useful to complete this
characterization, and if so what are they?
David A. Atkins, M.S.
Based on my general understanding of the watersheds, I consider the general background information
presented in the Assessment accurate and sufficiently complete for the endpoints of this watershed
assessment in the following areas:
• General view of Pacific salmon populations
• General view of resident (non-anadromous) fish
• Wildlife populations
• Native cultures
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EPA RESPONSE: No change suggested or required.
ATKINS RESPONSE: None required.
EPA FINAL RESPONSE: No response required.
The Assessment also describes the current economics of the watershed, including commercial and
sport fishing and subsistence activities.
EPA RESPONSE: No change suggested or required.
ATKINS RESPONSE: None required.
EPA FINAL RESPONSE: No response required.
Additionally, the report highlights several general aspects of the area that make the fishery unique in
both its abundance and diversity:
• The unique hydrology of the area (strong groundwater and surface water interaction) that
contributes to stable flows and temperatures favorable for salmon reproduction.
• The importance of anadromous fish in transferring marine-derived nutrients to upland areas
and thus providing nutrients to areas that would naturally be nutrient poor.
• The lack of roads and infrastructure that make the area unique as one of the few intact
ecosystems remaining in the world, and possibly unique for this type of fishery.
EPA RESPONSE: No change suggested or required.
ATKINS RESPONSE: None required.
EPA FINAL RESPONSE: No response required.
It would be helpful in the background section to better describe the uniqueness of the Bristol Bay
watershed ecosystem in the Pacific Northwest. This could include a description of other similar
ecosystems in the region that have undergone development and documentation of any changes in fish
populations associated with this development. The Assessment does mention the Fraser River as an
analogue, but the scale of development in this watershed, and even the success of the salmon fishery,
seems to be a point of contention, with some saying mining and fish coexist, and other saying the
impacts are severe.
EPA RESPONSE: The unique conservation value of Bristol Bay fisheries is now discussed in
Chapter 5.
ATKINS RESPONSE: The uniqueness of the watershed is adequately described in Chapter 5.
Organizing this information in terms of endpoints also better frames the context of the
assessment.
EPA FINAL RESPONSE: No response required.
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It would also be helpful to better explain fish resources in the proposed project area in comparison to
other areas within the watershed. I understand some of the necessary data may not be available for
the project area. It would be helpful to know, however, if the habitat in the project area is typical,
exceptional, or inferior to that in other areas of the watershed.
EPA RESPONSE: We now include figures showing reported salmon species distributions and
salmon diversity by HUC-12 watershed, across the Nushagak and Kvichak River watersheds
(Figure 5-3; Figures 5-4 through 5-8). It is informative to note that salmonid diversity is relatively
high in the project area. Information on population sizes and vital rates are limited for the region,
but are reported where known. In addition, we include summaiy statistics and figures of stream
and valley characteristics across the assessment area (Section 3.4), and compare stream attributes
in the project area to those of the larger watersheds (Section 7.2.1). These results generally
illustrate that the project area contains streams of a size and gradient well within the range of
suitability for salmon, as amply demonstrated by the distribution of spawning and rearing salmon
within the project area streams (Figures 5-4 through 5-8).
ATKINS RESPONSE: The information presented in these sections adequately addresses the
concern.
EPA FINAL RESPONSE: No response required.
Regarding geological resources, the report describes the Pebble deposit and five other mineral
deposits in the Nushagak and Kvichak watersheds. It would be helpful to know if there are other
mineral resources or oil and gas resources in the Bristol Bay watershed as a whole that could also be
exploited. It would also be helpful to describe the portion of the watershed that is off-limits to
development due to park and protected area status vs. those lands that are open to mineral
development.
EPA RESPONSE: The scope of the assessment was to evaluate the potential impacts from large-
scale mining on salmon resources; thus, consideration of prospective oil or gas development in the
area was outside the scope. The mineral resources identified in the assessment are those in the
Bristol Bay watershed that have had some level of identification or exploration at this time. Mine
claims within the Nushagak and Kvichak River watersheds are shown in Figure 13-1 and
discussed in greater detail throughout Chapter 13. The assessment assumes that mining would
occur on lands open to mineral development.
Protected areas within the Bristol Bay watershed and the Nushagak and Kvichak River watersheds
are shown in Figures 2-3 and 2-4. We have clarified in the text that the Nushagak and Kvichak
River watersheds represent the least-protected area of the Bristol Bay watershed Other state
documents exist that map out areas in the Bristol Bay watershed off-limits to development.
ATKINS RESPONSE: The information presented in these sections and figures adequately
addresses this concern.
EPA FINAL RESPONSE: No response required.
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Steve Buckley, M.S., CPG
The background information presented in the characterization of the ecologic, hydrologic, and
geologic resources is overly broad in scope. Specifically, the descriptions of the relationship between
landforms, streams, and surface water and the interaction with groundwater are mentioned as very
important to fish in the watersheds, yet there is insufficient detail to assess these interactions and
consequently, the characterization of these resources is weak. There is more detailed information
available in the Environmental Baseline Document (EBD) regarding the relation between landforms,
streams, groundwater, and fish habitat in the watershed.
EPA RESPONSE: Descriptions of the region's physical environment have been expanded in
Chapter 3. We provide additional detail on the broad-scale habitat characteristics of the
watersheds, but providing the detail necessary to assess groundwater interactions comprehensively
is beyond the scope of this document, and data are not available to do so.
BUCKLEY RESPONSE: The revision improves the treatment of this issue but given how
critical this information is to understanding the watershed, fish habitat and the potential
impacts from mining, a more comprehensive analysis will be required at some point.
EPA FINAL RESPONSE: No response required.
Courtney Carothers, Ph.D.
The background information presented on the ecological and geological resources of the Nushagak
and Kvichak watersheds appears to be appropriate and accurate. The report notes that there is a lack
of quantitative data on salmonid populations in this region, a lack of a full identification and
characterization of salmon presence, spawning, and rearing areas, and a lack of detailed
understanding of how local stream and river system features (e.g., temperature, habitat structure,
predator-prey relationships, limiting factors) affect salmonid production in the region. Further,
climate change is noted to be affecting local conditions. These unknowns are important to stress
throughout the report.
EPA RESPONSE: Each risk analysis chapter of the revised assessment now includes an
uncertainty section. Climate change is now incorporated more explicitly as an important external
factor that could interact with mining impacts (Box 14-2).
The cultural characterization presented in Appendix D presents detailed information on historical and
contemporary Yup'ik and Dena'ina communities of this region, stressing the centrality of salmon and
subsistence in these cultures. This assessment benefits from the time-depth of relationships
developed by Boraas and Knott. Overall, this section of the report is based on standard ethnographic
methods, although the research design and analysis could be explained in more detail (and described
in a separate methods section). The "voices of the people" sections are helpful to present directly the
perspectives given by local people. These quotes reveal the complexity of subsistence and
contemporary village concerns in this region. At times, the cultural assessment can minimize this
complexity.
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EPA RESPONSE: Additional detail was added to the methodology section of Appendix D.
As detailed in the specific comments below, potential risks and impacts to subsistence are
underestimated and at times framed in the report as primarily ones of physical health and economic
factors. As described in Appendix D, harvesting, processing, sharing, and consuming wild foods are
central to social, cultural, spiritual, psychological, and emotional well-being in Yup'ik andDena'ina
cultures. The subsistence lifestyle is considered central to the health of the people and communities
of this region. This is particularly important to note for indigenous communities who continue to
cope with the legacies of colonialism. This point is made in Appendix D (but at times could also be
strengthened there, as suggested below), and is articulated in some of the quoted interview material.
EPA RESPONSE: The assessment text regarding the importance of the subsistence way of life has
been expanded to recognize the centrality of subsistence to the social, cultural, and spiritual well-
being of the indigenous cultures.
Recent data on subsistence harvests, use areas, and local context collected for the PLP Environmental
Baseline Document (as well as evaluation and discussion of such data, e.g., Langdon et al. 2006) and
by the Alaska Department of Fish and Game (e.g., Fall et al. 2012) would be a useful addition to the
cultural characterization. Other studies of local traditional ecological knowledge (e.g., Kenner 2005)
may help to supplement the assessment of the abundance and distribution of fish species in this
region, or to supply information on other less-studied freshwater fishes. Recent research on the
contemporary salmon-based livelihoods of the region (e.g., Holen 2011, 2009a, and 2009b; Hebert
2008; Donkersloot 2005) would also be helpful to include. An inclusion of case studies of salmon-
based cultures that have suffered depletions of their resource base would add to the presentation of
likely fish-mediated impacts to culture (e.g., Colombi and Brooks 2012).
EPA RESPONSE: The suggested references were consulted during the revision of the report and
the discussion of subsistence has been expanded. In addition, case studies have been cited where
applicable in the discussion of potential effects to indigenous cultures in Chapter 12.
Appendix E also characterized the economic baseline of the region. Why is this dimension not asked
about here?
EPA RESPONSE: The focus of the assessment is potential effects on salmon from large-scale
mining. There are two secondary endpoints: salmon-mediated effects on wildlife and Alaska
Native culture. The economics related to potential salmon-mediated effects are not evaluated
because they are outside the scope of the ecological risk assessment. Appendix E presents
information regarding the economic value of salmon, which is provided as backgroundfor the
descriptive material in Chapter 5 and could be used as a basis for future analyses. However, this
assessment does not include an economic endpoint.
CAROTHERS RESPONSE: Additional methodological detail was added to Appendix D, but
the revised Appendix D was not included for review and was "not considered part of the
evaluation being conducted under this contract" (Statement of Work, p 1), so could not be
reviewed.
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I found evidence throughout the Revised Assessment that supports EPA's response that "the
assessment text regarding the importance of the subsistence way of life has been expanded to
recognize the centrality of subsistence to the social, cultural, and spiritual well-being of the
indigenous cultures" (EPA Response, p 40).
Suggested references on subsistence harvests, use areas and local context were included in the
Revised Assessment. Section 5.4 of the Revised Assessment (updating section 5.6 of the original
report) is substantially improved from the first draft assessment.
I disagree with the EPA response that Appendix E on the economics of salmon in the region is
not relevant to explore the salmon-mediated effects to Alaska Native cultures (EPA Response, p
39). Just as salmon are central to culture, they are central to the mixed (market and non-
market) economies of the Alaska native communities of the region. The dependence of the local
communities and cultures on commercial fishing and tourism, as well as the links between these
commercial engagements and subsistence fisheries are important aspects to consider in
evaluation salmon-mediated effects to Alaska Native cultures. Some additional information
from Appendix E has been added to the report. More of this information, particularly that
information relevant to the Alaska Native communities in the region (e.g., community
engagement in, and dependence on, commercial fisheries) would enhance the report. The fish-
mediated potential impacts to commercial fishing would affect Alaska Native cultures;
commercial fishing has long been a part of the communities and cultures in this region.
Additional references on subsistence and mixed economies would strengthen the revisions (e.g.,
p 5-36, last paragraph, no references provided; Krieg et al. 2007, Wolfe and Walker 1987,
among others would be helpful references to add).
Krieg, T.M., J.A. Fall, M.B. Chythlook, R. LaVine, and D. Koster. 2007. Sharing, Bartering,
and Cash Trade of Subsistence Resources in the Bristol Bay Area, Southwest Alaska. Alaska
Department of Fish and Game, Division of Subsistence Technical Paper No 326, Juneau.
Wolfe, R.J. and R.J. Walker. 1987. Subsistence Economies in Alaska: Productivity, Geography,
and Development Impacts. Arctic Anthropology 24(2): 56-81.
EPA FINAL RESPONSE: Additional information from and references to Appendix E regarding
local employment in commercial fishing and recreational sectors have been added to Chapter 5.
Chapter 12 now acknowledges the potential effects of decreased commercial fishing and tourism
opportunities on Alaska Native communities. The references provided by the reviewer also have
been added.
Dennis D. Dauble, Ph.D.
As noted in the approach, characterization of and risk to ecological resources emphasized salmon and
other important sport and commercial fish species. Consequently, the description of non-salmonid
species generally lacked estimates of population size, except for sport and subsistence catch statistics.
There was a long list of other resident fish in Appendix A, but their role in the Bristol Bay watershed
(including the Nushagak River and Kvichak River watersheds) is not described in any detail there or
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in the main report. Available data on known or perceived ecological interactions among salmonid
and resident fish should be included in the assessment.
EPA RESPONSE: The assessment endpoints—salmonid fishes and their effects on wildlife and
Alaska Native cultures—have been clarified in Chapters 2 and 5; other fish species are thus
outside the scope of the assessment. However, we recognize in the text that other fishes (as well as
other biota) are important components of the ecosystem, and have included a table of all
documentedfish species in the region in Chapter 5 to better reflect the fish fauna in the region.
DAUBLE RESPONSE: While I understand why many fish species are outside the scope of the
assessment, what's still missing is information on known ecological interactions (i.e., predation,
competition) within the fish community. It's possible these interactions have as much influence
on the salmonid fish population as mining impacts or global climate change might have, for
example, Table 5.1 is a start. Another table or brief description of the ecological role of each
important or abundant fish species in the Bristol Bay watershed-in relation to salmonids would
be useful.
EPA FINAL RESPONSE: Additional discussion of the role of salmon in the region's foodwebs
has been added to Chapter 5 (e.g., Box 5-3).
Another limitation to the salmon-centric assessment is that risk assessment endpoints, described in
Chapter 3 of the main report, do not address other aquatic ecological resources. Consequently, while
there was acknowledgment of ecological dependencies among salmon, other fishes, and land
mammals, very little information was provided on primary and secondary production processes of
aquatic communities. For example, the relative importance of marine-derived nutrients (MDN) in the
form of salmon eggs and carcasses is discussed, but there is only brief mention of aquatic insects in
the diet salmonid species. What nutrient levels occur in these stream systems with and without
MDN?
EPA RESPONSE: We recognize that nutrient status, and more important prey availability, is a
critical component of habitat capacity for fish in these systems, and may be strongly driven by
salmon derived nutrients. We concur that more information is needed regarding potential limiting
factors for salmon productivity and capacity, and that food availability may be one such factor.
The role of aquatic invertebrates in the diet of salmonids receives more attention in the revised
draft, and is an essential part of the risk assessment for water treatment and discharge, given the
relatively high sensitivities of aquatic invertebrate taxa to metals. However, because water
chemistry data may not provide a complete picture of trophic status, particularly where direct
consumption of salmon flesh, eggs, and fry is of such high importance as it is in many of the area
streams, we determined that nutrient status of area streams is outside the scope of this assessment.
DAUBLE RESPONSE: I defer to EPA's judgment on this topic.
EPA FINAL RESPONSE: No response required.
A description of major groups of aquatic invertebrates in terms of biomass and seasonal abundance
should be included in the main report. Further, aquatic and terrestrial food webs and linkages need
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more embellishment. One approach might be to add narrative text with the conceptual model
discussion, including descriptions of community structure, function, and biomass.
EPA RESPONSE: Additional detail on foodwebs is beyond the scope of this assessment (as
detailed in Chapters 2 and 5). Further, available data are inadequate to assess risks at that level of
specificity. For example, there are no acute copper toxicity data for any aquatic insects and only
one old chronic value for a caddisfly.
DAUBLE RESPONSE: I don't agree that detail on food webs as it relates to salmonids is
beyond the scope of the assessment. No acute copper toxicity data for any aquatic insects? Note
that effects on primary production were also ignored in the document.
EPA FINAL RESPONSE: A subsection has been added to Chapter 8 on the toxicity of copper to
primary producers and the propagation of that effect through foodwebs to fish. Additional text on
aquatic-terrestrial foodwebs and aquatic macroinvertebrate assemblages has been added in
Chapter 5 (e.g., Box 5-3).
More detail on river and lake limnology would be helpful. For example, the hydrology of the
watershed is mainly limited to a brief discussion of salmonid habitats. The geology of the basin
emphasizes geology of mining areas and mineral processes. A more landscape-based description is
warranted given the importance of geology to surface water processes and groundwater movement.
The report would benefit from having a summary table listing lake size/volume and river
length/discharge for watersheds potentially affected (and not affected) by mining activities.
EPA RESPONSE: We now include maps of geology and estimated mean annual flow for the study
region (Chapter 3).
DAUBLE RESPONSE: River length can be easily inferred from new, detailed maps of the
watershed and specific water bodies. Mean annual flows are also now presented in Chapter 3.
Consequently, this comment was largely resolved.
EPA FINAL RESPONSE: No response required.
Also missing were specific habitat requirements for rearing of juvenile salmon. A brief description of
where pink and chum salmon spawn and rear in the Bristol Bay watershed relative to other salmon
species should be included in the main report. There was nothing in Appendix A on where coho,
pink, and chum salmon reside within the Bristol Bay watershed.
EPA RESPONSE: Identified spawning and rearing habitats for the five Pacific salmon species are
reflected in Figures 5-3 through 5-8, and additional text on salmon life histories has been included
in Chapter 5.
DAUBLE RESPONSE: Figures 5-3 through 5-8 and supporting narrative text are excellent
additions to the main document.
EPA FINAL RESPONSE: No response required.
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Each appendix has a wealth of supporting information and could serve as a stand-alone document.
However, having to work back-and-forth between the main report and appendices to interpret critical
aspects of the assessment presents a challenge. Don't assume the average reader will read (and
interpret) these appendices. To help remedy, the authors of the main report should strive to directly
cite relevant information (and/or a specific appendix) that supports their conclusions.
EPA RESPONSE: Additional information from Appendices A and B has been pulled into Chapter
5 of the main assessment. In addition, the purpose of the appendices has been clarified in Chapter
2.
DAUBLE RESPONSE: This approach is now apparent throughout the main document and is
both informative and helpful to the reader.
EPA FINAL RESPONSE: No response required.
Gordon H. Reeves, Ph.D.
The assessment, which included the report and appendices, was comprehensive and thorough
regarding the ecological resources of the Nushagak and Kvichak watersheds. The best available data
on fish numbers and distribution (Alaska Dept. of Fish and Game's aerial escapement counts, records
from the Anadromous Waters Catalog and Alaska Freshwater Fish Inventory, and the Environmental
Baseline Document of the Pebble Limited Partnership (2011)) were used for the assessment. These
data formed the foundation for much of the assessment on potential impacts to anadromous
salmonids and their freshwater habitat in these watersheds and their characterization appeared to be
accurate. The authors also appeared to have thoroughly identified and considered all of the
appropriate literature.
EPA RESPONSE: No change suggested or required.
Charles W. Slaughter, Ph.D.
If only Volume 1 (the Main Report) is considered, the characterization of some aspects of the
Nushagak and Kvichak watersheds would have to be termed cursory. Chapter 2, Volume 1
(Characterization of Current Condition) provides only a superficial overview of the landscape of the
Bristol Bay watersheds; a reader would preferably have access to Wahrhaftig (1965) or Selkregg
(1976), as only two (relatively dated) suggestions, to gain a more comprehensive understanding of
the region. Similarly, Volume 1 provides a relatively superficial discussion of non-fish wildlife
concerns, or human/cultural concerns.
EPA RESPONSE: Additional information on the region's physical environment from Selkregg
(1974) has been included in Chapter 3. We have also clarified that our discussion of biological
communities focuses on the assessment endpoints, as defined in Chapters 2 and 5.
SLAUGHTER RESPONSE: Chapter 3 is a great improvement. The detailed maps and
discussions of the physiographic setting, hydrologic landscapes, aquatic habitats, water quality,
seismicity, and existing development of the region are comprehensive and informative.
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Explanation of methodology, as in Box 3.1, Box 3.3, and throughout the entire document, is
very helpful. This chapter now allows a reader to gain a more realistic understanding of the
Bristol Bay watershed setting.
EPA FINAL RESPONSE: No response required.
By contrast, the information provided in Appendices A-H appears to be comprehensive and complete
for each subject field. (Appendix I appears to be a general "template" summary, not tailored to the
Bristol Bay watershed environment).
EPA RESPONSE: The purpose of the appendices vs. the main assessment document has been
clarified in Chapter 2. Appendix I is not meant to be specific to any given region, but discusses
options that are possible and notes that their applicability is dependent on site-specific constraints.
What would be chosen for the Bristol Bay watershed environment, given a mining plan and permit
application, also would be dependent on regulatory decisions.
SLAUGHTER RESPONSE: OK. The clarification is appreciated, as is the inclusion of much
material from the appendices into the narrative of the revised Assessment.
EPA FINAL RESPONSE: No response required.
As noted in the Executive Summary, the Assessment does NOT address several major components of
the (hypothetical) Pebble project, including electrical generation and transmission, a deep-water port,
or "secondary development" and associated infrastructure, which would follow an initial mining
project. A truly comprehensive analysis should incorporate a full analysis of these aspects.
EPA RESPONSE: The scope of this assessment was tailored to its purpose, as clarified in the first
two chapters. We would expect that a full evaluation of any future mining permit applications and
subsequent National Environmental Policy Act Environmental Impact Statements would consider
these components.
SLAUGHTER RESPONSE: Again - to me, this simply means that this assessment does not (or
cannot, presumably because of limited EPA authority) address the full suite of probable
consequences of the PLP project. Permit application and NEPA review hopefully would be
more adequate and comprehensive.
EPA FINAL RESPONSE: The assessment is sufficiently comprehensive to meet its stated purpose.
It is not intended to be an environmental impact assessment.
John D. Stednick, Ph.D.
The site characterization needs to be expanded. The report needs to better characterize the physical
setting. There are a variety of data sources that can be used to better describe the physical setting. It
would be useful to see geology, geomorphology, soils, vegetation, digital elevation maps,
hypsometric curves of the watersheds in question, streamflow data, and precipitation data—
especially storm events and water quality data for surface and groundwater over time and space.
Various geographical information system maps would be useful here.
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EPA RESPONSE: Maps displaying information about the physical setting have been added in
Chapter 3.
The salmon populations and habitat linkage needs to be better documented since many of the mine
impacts are resulted from hydrologic modification. Figures 3-2A to 3-2E represent good thinking and
an understanding of the linkages and potential effects of mining on these resources. The linkages to
indigenous peoples is illustrated in Figure 3-2E, but little text is presented, referring the reader to the
Appendix. The other conceptual models are not adequately addressed in the text. These flow charts
provide an opportunity to present processes and linkages as related to potential effects of mine
development activity and need to be developed within the text. Indeed, they seem to stand alone with
little discussion of potential effects. Additionally, not all charts have adequate materials in the
appendix for coverage, thus the variability in resource coverage is inconsistent and infers either a
writing bias or data (lack of) bias.
EPA RESPONSE: Conceptual models are now linked with relevant text, and are included in each
of the risk analysis and characterization chapters.
The assessment concludes that a hydrologic modification will have detrimental salmon habitat
consequences. The groundwater contributions to streamflows are important, both hydrologically and
ecologically. Additional streamflow and groundwater data are needed to represent this linkage.
Similarly, additional water quality data over time and space are needed and should include water
hardness for metal standards. Depth to groundwater as related to streamflow, age dating of waters,
and streamflow modeling would all be useful to illustrate the groundwater upwelling and hyporheic
exchanges.
EPA RESPONSE: We have incorporated a figure illustrating modeled and observed groundwater
upwelling zones (Chapter 7).
Site disturbance will be significant, yet there is no discussion of soil erosion. Soil erosion and
subsequent suspended sediment transport would have the potential to have significant effects on
water quality, channel delivery efficiency, salmon, salmon habitat, and metal transport. There is a
generic discussion of road construction related to erosion, but road standards, road location, road
usage, road maintenance (salting, grading, or watering), and length of roads would help in the risk
assessment.
EPA RESPONSE: Soil erosion on the mine site is not assessed because the scenario prescribes
that runoff will be directed to retention basins. Salts used to reduce dust and improve winter
traction on roads are discussed in Section 10.3.3 (Chemical Contaminants in Stormwater Runoff).
Road usage and length are also factored into the risk assessment (e.g., in the assessment of
chemical spills (Section 10.3.3) and potential impacts from dust (Section 10.3.5)). Potential
mitigation measures for stormwater runoff erosion, and sedimentation are discussed in Box 10-3.
Are any endangered or threatened species present, either state or federally listed?
EPA RESPONSE: Text has been added to Chapter 5 stating that there are no state or federal
endangered or threatened species in the region.
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Roy A. Stein, Ph.D.
Overall Characterization. The characterization of the resources of the Nushagak and Kvichak
watersheds was appropriate and accurate in the ecological arena save for the issues discussed below.
Geological and cultural resources seemed adequately characterized, but they are not within my
expertise. Finally, given the emphasis on these two watersheds (not the entire Bristol Bay watershed),
might there be some consideration of a more circumscribed document title?
EPA RESPONSE: The assessment deals with multiple spatial scales (now clarified in Chapter 2).
The Bristol Bay watershed is the largest spatial scale considered in the assessment, and it is the
only one that encompasses all of the issues discussed in the document.
Broad Scale Comments:
Global Climate Change I. Risks to salmonids seem far greater than what is reviewed throughout
this portion of the document. Missing, in my view, is any consideration of Global Climate Change,
especially in light of the expected life of the mine (25-78 years), applied directly to the Bristol Bay
Watershed (save for a brief mention on page 5-28, 2nd full paragraph). Given our current
understanding, general changes likely include more intense precipitation events and increased
temperature (and then of course, all that follows from these two changes and as models become more
sophisticated, more specific geographically localized impacts could be assessed). With more intense
storms come a greater likelihood of a failure of Tailings Storage Facilities (i.e., commensurate with
more frequent and more intense flooding), more acidity from Pre-Tertiary waste rock (which will
enter quite vulnerable, poorly buffered streams), and greater sediment influx into streams (and
increasing fines in the gravel by as little as 5%, quite a small proportion, "... causes unacceptable
effects on salmonid reproduction" (page 8-6; also see Chapter 7), which could occur during "routine
operations", especially in light of the fact that sediment influx into streams is a cumulative process).
Increased stream temperatures, depending on the absolute increase over a period of 78 years (and
beyond, see "in perpetuity" comments below), could lead to reductions in salmon spawning success,
as extant populations are specifically adapted to the current temperature regime. As is apparent, both
increasing intensity of storms and increasing temperature will likely compromise salmon spawning
success, and growth and survival of their offspring in the freshwater environment of Nushagak and
Kvichak rivers.
EPA RESPONSE: Climate change projections and potential impacts are now included and
discussed in Chapter 3 and are included as important external factors in the risk analyses
presented in Chapters 7, 9,10, and 14.
What this would entail, at the very least, is a discussion of a monitoring system to quantify the
impacts of Global Climate Change whose impacts on the ecosystem can then be differentiated from
mine impacts. My concern is that if the mine is built, all negative impacts of the mine on salmonids,
etc., could be attributed to Global Climate Change rather than the true culprit which would be the
mining activities.
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EPA RESPONSE: Climate change projections and potential impacts are now included in Chapter
3 and Box 14-2 includes a discussion of the need for future monitoring to differentiate climate
change effects from large-scale mining effects.
Global Climate Change II. Indeed, climate change is affecting Alaskan salmon as demonstrated (in
a paper that just appeared online July 11, 2012) by a loss of a late-migrating population of pink
salmon in a small stream near Juneau, in favor of an early-migrating one. Genetic evidence supports
this explanation for Kovach et al. (2012) had 17 generations of data (since 1979) showing the
reduction of the September spawners in favor of the late-August ones in response to increasing
stream temperatures. As Kovach et al. (2012) write in their concluding paragraph:
"We no longer observe the clear phenotypic distinction between early- and late-migrating
individuals that was once present in the system. Apparently, the very-late-migrating
phenotype has been greatly reduced or potentially lost. Although microevolution may have
allowed this population to successfully track environmental change, it may have come at the
cost of a decrease of within-population biocomplexity - the loss of the late run. This is not a
surprising result; by definition, directional selection will decrease genetic variation.
However, it does highlight the importance of maintaining sufficient genetic and phenotypic
variation within populations in order for them to have the ability to respond to environmental
change."
The ramifications of this work are obvious. As pointed out in the report (pages ES-8, 2-22, 5-28 as
just a few examples), the exceptional quality of the Bristol Bay salmon stocks depend on the pristine
quality of a set of quite diverse aquatic habitats, which has led to the development of genetically
diverse stocks of salmon within species, each uniquely adapted to particular habitats. Reducing this
variability by mining on top of the rivers that produce >50% of the wild sockeye salmon in Bristol
Bay serves to reduce the flexibility with which these stocks respond to any environmental change
(most notably Global Climate Change), and most notably during the time course of the Pebble Mine.
EPA RESPONSE: Climate change projections and potential impacts are now discussed in Chapter
3 and include these points.
Groundwater Exchange. One of the key aspects of this system is the importance of groundwater
exchange with surface streams and this groundwater contributes mightily to salmonid egg incubation
success and survival (page 2-21). Simultaneous with this is the fact that the water demands of the
proposed mine will require more than just surface waters available to it, but rather the mine will have
to exploit groundwater resources to support its operations. This is yet another risk to salmonid
success for reduction in the availability of groundwater will lead to increased temperatures in
summer (see pages 3-7, 5-28, 5-29) and less inviting overwinter habitats (pages 5-20, 5-29), further
exacerbating both mining and climate change effects.
EPA RESPONSE: We have updated our hydrologic analyses to represent the probable influence
of mine scenarios on surface water/groundwater interaction. Climate change projections and
potential impacts are now discussed in Chapter 3.
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Exploration Effects. During the public testimony segment, several Alaskan Natives argued that
impacts owing to exploration have already occurred. A series of points were made: 1) exploration
equipment was left behind, despoiling the landscape, 2) noise from helicopters frightened moose
making them less vulnerable to exploitation, and 3) habitat change has already begun just due to
exploration activities.
EPA RESPONSE: We acknowledge this testimony, but potential or actual impacts of exploration
activities are outside the scope of the assessment as defined in Chapter 2.
EPA FINAL RESPONSE: A text box briefly discussing exploratory activities has been added to
Chapter 2 in the final assessment.
"In Perpetuity." Following up on the idea of increased risk (see previous points) to salmon, I
struggled with the idea of this mine being monitored and maintained "in perpetuity" (e.g., pages ES-
2, 4-32, 4-34). First, this relates directly to the Global Climate Change issues, in that these changes
likely will continue to build through time, further exacerbating negative impacts on salmon. Even
without climate change, salmon are in peril from mining operations in the Nushagak and Kvichak
rivers; with climate change, the cards are stacked against them.
EPA RESPONSE: The post-closure phase of mining begins when reclamation is completed and
monitoring and maintenance commences using the controls put into place during closure; exactly
how long the site would require monitoring and maintenance is unknown, and thus may be 'in
perpetuity'. There are no existing examples from which to evaluate success of treatment in
perpetuity. No mine in Alaska has maintained a tailings pond into post-closure, although one
small mine did maintain a pond during a many year hiatus from operations. Under AS 72.90.040,
financial assurance is required to be sufficient to cover expenses for as long as treatment need is
predicted, even into perpetuity (e.g., Red Dog Mine). Maintaining a water cover over the tailings is
a part of the reclamation and closure plan for the Red Dog Mine. The comment is noted and
understood. No changes suggested or required.
Second, what regulatory or institutional mechanisms currently available place the responsibility of
these efforts on the corporation "in perpetuity"? Because mining companies come and go, might
there be mechanisms that come into play if this particular company goes bankrupt? Might there be
some sort of bonding process that protects the environment from the mine's remains into the long-
term future? If not, should new legislation be pursued? Acknowledgement of this important issue
should be front and center in the document, in my view.
EPA RESPONSE: There are many requirements that have to be met including compliance with
the CWA § 404(b)(1) Guidelines and adequate financial assurance under AS 72.90.040. The
former would lead to the least environmentally damaging preferred alternative and the latter to
having adequate financial resources to cover the cost ofperpetual treatment. These issues would
be addressed in a permit process. Our purpose in the assessment is to evaluate the potential effects
of the primary features of a mine, assuming conventional modern mitigation measures. Additional
information on the regulations and financial assurance issues associated with mining has been
added in Chapter 4 (Boxes 4-2 and 4-3). The comment is noted and understood.
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Third, I began the review process with idea that the mine would be built, would capture its resources,
and then would end by restoring the site. The scenario that includes monitoring and maintenance
1,000 years into the future continues to bother me. One solution that comes to mind is that Federal or
state government would be charged with these monitoring and long-term maintenance activities, paid
for by a hefty tax on the minerals removed from this site.
EPA RESPONSE: Currently, the solution is the requirement and provision of adequate financial
assurance (under AS 72.90.040, when speaking specifically about Alaska) by the company. The
comment is noted and understood. No change suggested or required
Finally, I am not encouraged by any of the text surrounding this issue, the two most relevant quotes
(pages 4-31 and 5-45, respectively) being:
"There are no examples of such successful, long-term collection and treatment systems for
mines, because these time periods (100's to 1000's of year) exceed the lifespan of most past
large-scale mining activities, as well as most human institutions."
"We know of no precedent for the long-term management of water quality and quantity on
this scale at an inactive mine."
EPA RESPONSE: The post-closure phase of mining begins when reclamation is completed and
monitoring and maintenance commences using the controls put into place during closure; exactly
how long the site would require monitoring and maintenance is unknown, and thus may be 'in
perpetuity'. There are no existing examples from which to evaluate success of treatment in
perpetuity. No mine in Alaska has maintained a tailings pond into post-closure although one small
mine did maintain a pond during a many year hiatus from operations. Under AS 72.90.040,
financial assurance is required to be sufficient to cover expense for as long as treatment need is
predicted, even into perpetuity (e.g., Red Dog Mine). Maintaining a water cover over the tailings is
a part of the reclamation and closure plan for the Red Dog Mine. The comment is noted and
understood. No changes suggested or required
And, finally, a quote from Chapter 8 on page 8-13:
"The promises of today's mine developers may not be carried through by future generations
of operators whose sole obligation is to the shareholders of their time (Blight 2010)."
EPA RESPONSE: The comment is noted and understood. No changes suggested or required
William A. Stubblefield, Ph.D.
The EPA's assessment document presents a seemingly comprehensive compilation of the data
associated with the ecological, geological, economic, and cultural resources of the Bristol Bay area.
The characterization as presented seems to provide appropriate background information for the
assessment considering the hypothetical nature of the evaluation. Without having specific knowledge
of the area in question, it is not possible to provide an assessment as to whether the characterization
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was accurate. I'm unaware of significant literature, reports, or data that were specific to the site and
would be useful for consideration. The assessment should be expanded to include greater detail
regarding the environmental aspects of the site.
EPA RESPONSE: Additional information on the physical environment of the region and
assessment endpoints has been incorporated into Chapters 3 and 5.
STUBBLEFIELD RESPONSE: I agree, substantial additional information on the physical
environment of the region and the assessment endpoints has been incorporated into Chapters 3
and 5. This helps in the overall description of the Bristol Bay environment and helps
characterize potential environmental concerns.
EPA FINAL RESPONSE: No response required.
Dirk van Zyl, Ph.D., P.E.
The geological information was taken from documents prepared to conform to and in compliance
with the standards set by National Instrument 43-101 (NI 43-101) (Ghaffari et al., 2011). This
regulatory instrument emphasizes resource information for projects. While I cannot comment on the
accuracy of the regional geological information, the document should reflect accurate geological
information of the Pebble District as known at the time when the report was prepared.
EPA RESPONSE: The assessment uses geological information available for the Pebble site area.
Geological information from Selkregg (1974) has been incorporated into Chapter 3.
My review did not include the Environmental Baseline Document (EBD) of the PLP. However, in
scanning that document, it seems that more site-specific information on site hydrogeology may be
available than was described in the EPA Assessment. While the latter refers to the EBD extensively
in terms of fish populations, etc., it does not refer to it for much of the site physical characterization.
EPA should address this in edits to the Draft Assessment.
EPA RESPONSE: Additional site-specific hydrogeology information has been incorporated in
Chapters 3and 7 and in the calculation of water quality values in Chapter 8. EBD data were used
along with USGS data for hydrologic analysis in both drafts of the assessment, but the sources of
data were not discussed as extensively in the previous draft.
VAN ZYL RESPONSE: No further comments on Question 1.
EPA FINAL RESPONSE: No response required.
Phyllis K. Weber Scannell, Ph.D.
The Environmental Assessment presents a well-documented discussion of the fish and wildlife
resources of the Nushagak River and Kvichak River Watersheds, with more limited discussions of
the remainder of the Bristol Bay Watershed. The document discusses interactions among species,
including nutrient flows and the importance of groundwater systems; however, information on
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contributions of marine-derived nutrients and existing pressures on the environment are not as
complete, or lacking. The information is general in nature. Should mine development go forward, it
will be necessary to obtain ecological information specific to the potentially affected areas. The
information should include timing of fish spawning, egg hatch, in-migration and out-migration, and
similar specific life-history information for important wildlife species.
EPA RESPONSE: We have clarified the use of information at different scales (Bristol Bay
watershed and Nushagak and Kvichak River watersheds in the problem formulation chapters,
smaller spatial scales in the risk analysis and characterization chapters). General information on
assessment endpoints is included in Chapter 5, with more detailed information included in the
appendices.
WEBER SCANNELL RESPONSE: Reviewer is satisfied with this approach.
The revised draft contains new sections 2.2.1 Topical Scope and 2.2.2 Spatial Scales. The
section 2.2.1 defines the limits of the assessment ("we do not consider all potential sources of
risk...") and the focus ("potential effects on freshwater habitats").
Section 2.2.2 defines the five spatial scales used in the Assessment and the use of broader
spatial scales for describing the physical, chemical and biological environments and effects of
multiple mines.
These two sections provide needed clarity to the Assessment and satisfy the initial concerns
expressed by this reviewer.
EPA FINAL RESPONSE: No response required.
Paul Whitney, Ph.D.
Fish Population Estimates. There are several places in the text where impacts of the loss and
degradation of habitat on fish populations was not quantified because of the lack of demographic data
for salmonids (e.g., page ES-26, third bullet). These statements are only partially accurate. It is true
that population models such as life tables or Leslie matrices require population age class data to
estimate population numbers. However, even if demographic data are available, these population
models do not relate population estimates to habitat quality. Incomplete data and relating fish
population estimates to habitat quality are not an uncommon problem in ecology and there are many
approaches for dealing with this issue. Approaches such as Ecosystem Diagnosis and Treatment
(McElhany et al. 2010), Expert Panels (Marcot et al. 2012), Bayesian nets (Lee and Reiman 1997),
Discussion with experts (Appendix G), or Weighing Lines of Evidence (Section 6.1.5) are just some
of the methods for relating habitat quality to fish abundance. Models and expert opinions, of course,
bring their own uncertainties but it seems better to have quantitative estimates (and discussion of the
estimates) of all the potential fish losses due to habitat loss than no estimate at all.
EPA RESPONSE: Approaches such as EDT, mentioned above, were considered, but rejected due
to lack of stream-reach specific information needed to provide the sort of quantitative estimates
desired. Expert panels and Bayesian Belief Networks are recognized as potentially providing
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useful guidance for identifying key uncertainties and directing future research and monitoring
efforts. However, this was deemed outside the scope of this assessment, and we instead focus on
the risks associated with the types of habitat change that would be expected under the mine
scenarios outlined We restrict quantitative estimates of population level effects to the most severe
cases where total losses of runs could be reasonably assumed
Even though the Executive Summary indicates that the impacts of loss and degradation of habitat on
fish populations could not be quantified, the text does provide some estimates. For example, the
assessment (page 6-11, first full para) estimates "that the combined effects of direct losses of habitat
in the North Fork Koktuli, downstream in the mainstem Koktuli and beyond, and impacts on
macroinvertebrate prey for salmon could adversely affect 30 to 50% of Chinook salmon returning to
spawn in the Nushagak River watershed." This type of statement, and the basis for the statement
followed by a discussion of uncertainty, is a good example of the estimates that would better describe
possible impacts of the example mine on salmonids. Another example estimate appears on page 6-39
for four species of salmon.
EPA RESPONSE: We restrict quantitative estimates of population level effects to the most severe
cases where total losses of runs could be reasonably assumed, such as the example given above.
The text of the revised assessment has been clarified for consistency regarding feasibility of
estimates.
3.4 Charge Question 2
A formal mine plan or application is not available for the porphyry copper deposits in the
Bristol Bay watershed. EPA developed a hypothetical mine scenario for its risk
assessment, based largely on a plan published by Northern Dynasty Minerals. Given the
type and location of copper deposits in the watershed, was this hypothetical mine scenario
realistic and sufficient for the assessment? Has EPA appropriately bounded the magnitude
of potential mine activities with the minimum and maximum mine sizes used in the
scenario? Are there significant literature, reports, or data not referenced that would be
useful to refine the mine scenario, and if so what are they?
David A. Atkins, M.S.
The hypothetical mining scenario presented in the Assessment is based on a "Preliminary
Assessment Technical Report" of the Pebble deposit prepared for Northern Dynasty Minerals by
Wardrop (referred to as Ghaffari et al. 2011), in conformance with Canadian National Instrument 43-
101 (NI 43-101) which is used to set standards for public disclosure of scientific and technical
information about mineral projects of companies on bourses supervised by the Canadian Securities
Administrators. By most accounts, the Pebble deposit is a world-class deposit and the Wardrop report
counts nearly 11 billion tonnes of total resource. It is unlikely that all the ore currently identified
would be mined, so 11 billion tonnes would be an upper bound for this particular deposit. It is also
certain that exploiting the Pebble deposit would have to be at a scale large enough to justify the
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capital investment to build an infrastructure in such a remote area. Although the Assessment is
ostensibly about any mining development in the Bristol Bay watershed, the use of the Wardrop
scenario for Pebble effectively makes the report an assessment of mining the Pebble deposit.
EPA RESPONSE: The purpose of the assessment is to estimate potential impacts of large-scale
surface porphyry copper mining on salmon ecosystems in the Bristol Bay watershed. The
preliminary plan for mining the Pebble deposit was used as the basis for the assessment because
that deposit is the most likely to advance in the near term. Also, the Agency believes that mining of
other porphyry copper deposits in the watershed would proceed with a similar approach, since the
scenarios used are similar to what has been done at other porphyry copper deposits. Therefore, it
is appropriate to use Northern Dynasty Minerals' 2011 plan for the Pebble deposit (Ghaffari et al.
2011) as the basis for the scenarios; however, a final mine plan may differ from what is presented
in Ghaffari et al. (2011). Chapter 13 of the revised assessment also considers the potential
cumulative effects of additional smaller copper porphyry mines in the watershed No change
suggested or required.
ATKINS RESPONSE: The response adequately addresses the concern.
EPA FINAL RESPONSE: No response required.
The question then becomes what size mine is feasible from a technical and economic point of view.
The Pebble deposit mine plan, as presented in the Wardrop report, outlines three scenarios:
• An "investment decision case" for a 25-year mine life that would mine 2 billion tonnes of
ore;
• A "reference case" for a 45-year mine life that would mine 3.8 billion tonnes of ore; and
• A "resource case" for a 78-year mine life that would mine 6.5 billion tonnes of ore, or 55% of
the total measured, indicated and inferred resource.
The Assessment chose minimum and maximum mine sizes of 2 billion and 6.5 billion tonnes of ore,
respectively. Thus, the resource estimate used for the Assessment is the same as that for the two end
members presented by Wardrop. This would make the mine one of the largest in the world,
exceeding the size of the 10th percentile of global porphyry copper deposits by an order of magnitude
(see Appendix H of the Assessment). Mines that ultimately become this size usually expand by
increments, as exploration discovers new ore zones and expansion permits are granted.
EPA RESPONSE: Yes, the scenarios represent large-scale mines. The purpose of the assessment
is to estimate potential impacts of large-scale surface porphyry copper mining on salmon
ecosystems in the Bristol Bay watershed, so large mine sizes are appropriate. It is quite likely that
large mines would be created in increments, but this would not influence our assessment, as we
have evaluated impacts based on volumes of material released in the event offailures or accidents
and on material processed as proposed in Ghaffari et al. (2011) as reasonable for a deposit of this
size, regardless of the time period for mine operation. However, we have included a third, smaller
mine in our revision to represent the median-sized porphyry copper mine on a worldwide basis
(250 million tons).
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ATKINS RESPONSE: This discussion and inclusion of the 250 million ton scenario is
adequate.
EPA FINAL RESPONSE: No response required.
The Wardrop report further delineates Pebble West as a low-grade deposit near the surface that
would most efficiently be mined using open-pit methods, with Pebble East as a deeper, higher-grade
deposit that would most efficiently be mined using underground methods (specifically block-caving).
Mine facilities, as outlined in the Wardrop report, would include:
• Open-pit mining utilizing conventional drill, blast and truck-haul methods for near-surface
deposits.
• Underground, block-cave methods for deeper deposits.
• A process plant with throughput of 200,000 tonnes/day that utilizes conventional crush-grid-
float technology with secondary gold recovery.
• Other mine-site facilities, including:
o Tailings storage.
o Waste rock storage (the estimated waste/ore strip ratio is 2:1).
o A natural-gas fired power plant,
o Shop, office, and camp buildings.
o Pipelines to ship ore concentrate slurry to the port facility; return water from the
tailings slurry after separation at the port facility; and fuel.
EPA RESPONSE: No change suggested or required.
ATKINS RESPONSE: None.
EPA FINAL RESPONSE: No response required.
This mining and ore processing approach is conventional, and the Assessment includes these
elements. A mine developer may present alternative plans that could vary or alter how the mine is
developed, but the fundamental components would most likely remain the same.
EPA RESPONSE: We agree with this comment. No change suggested or required.
ATKINS RESPONSE: None.
EPA FINAL RESPONSE: No response required.
Because the Assessment is presented as a general assessment of mining risks and impacts in Bristol
Bay and not a specific analysis of the Pebble Project, reliance on the scenario presented in Wardrop
makes the assessment overly specific. Further, Chapter 7 provides more specific information on
"Cumulative and Watershed-Scale Effects of Multiple Mines," which presents analysis of potential
impacts from mining five additional deposits in various stages of development (presumably from
early exploration to pre-feasibility). The information presented in Chapter 7 seems more like another
mining scenario than a cumulative impacts assessment. Therefore, I would suggest a broader range of
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potential mining scenarios be organized as follows, with the detail of assessment necessarily
becoming more speculative with each subsequent scenario in the list (due to the lack of geologic and
engineering information on the other deposits):
• Development of one, average-sized porphyry copper deposit (50th percentile or 250 million
tonnes of ore as described in Appendix H) in the location of the Pebble deposit.
• Development of a mega-mine in the location of the Pebble deposit (of the range between 2
and 6.5 billion tons of ore) that may develop after multiple expansion and permitting cycles.
• Development of a mining district consisting of an average-sized Pebble mine and other
potential mines (i.e., those presented in Chapter 7).
• Maximum development of all identified potential resources to their most likely ultimate
extent.
Considering this broader range of scenarios would help the reader to better understand the range of
potential risks and impacts.
EPA RESPONSE: The Pebble deposit is located in the watershed of interest, the deposit is similar
to other copper porphyry deposits in the world, and components of the scenarios are common and
anticipated for any such deposit of this type; thus, we feel that use of the Pebble deposit
characteristics and location is appropriate. The revised assessment includes an additional mine
size scenario (Pebble 0.25) representing the worldwide median size porphyry copper mine (Singer
et al. 2008). The revised assessment expands the cumulative impacts discussion (Chapter 13)
further by including transportation corridors and secondary impacts.
ATKINS RESPONSE: This discussion adequately addresses the concern.
EPA FINAL RESPONSE: No response required
Steve Buckley, M.S., CPG
Additional mine scenarios are necessary to appropriately bound the magnitude of potential mine
activities. The maximum mine size in the mine scenario seems appropriate given the existing public
information on the Pebble deposit. The minimum mine size of 2 billion tons exceeds the 90th
percentile of global porphyry copper deposits. Using a minimum mine scenario in the range of 250
million tons or in the 50th percentile range of global porphyry copper deposits would be more
appropriate to bound the lower end of the magnitude of potential mine activities. It would also be
useful to include some variation in mining methods. This could include incremental development of a
smaller open pit in the lower grade zones of a deposit, along with a portion of the higher grade
deposit being mined by underground block caving methods to further assess the minimum potential
impact of the mine scenario.
EPA RESPONSE: The revised assessment includes a mine size scenario (Pebble 0.25)
representing the worldwide median-sized porphyry copper mine as presented in Singer et al (2008).
The revision does not evaluate risks from hazards for underground mining, but a brief discussion
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of underground mining is included in Chapter 4. The failures assessed would apply whether the
mining technique were underground or surface.
BUCKLEY RESPONSE: The revised assessment is a major improvement with the addition of
mine scenario 0.25 and the brief discussion of underground mining.
EPA FINAL RESPONSE: No response required.
Courtney Carothers, Ph.D.
The hypothetical mine scenario was closely based on a probable mine prospect under development.
As such, it appears to be realistic and sufficient, if challenging to conceptualize as fully hypothetical
given this association.
EPA RESPONSE: No change suggested or required.
The report notes that the Pebble deposit may exceed 11 billion metric tons (4-17). The rationale for
choosing 6.5 billion metric tons as a maximum size is based "most likely mine to be developed (4-
19)." The rationale for not choosing a higher potential maximum could be explained.
EPA RESPONSE: Both the 2 and the 6.5 billion ton scenarios were presented in Ghaffari et al.
(2011) as economically viable, technically feasible, and permittable. The purpose of the assessment
was to estimate potential impacts of large-scale surface porphyry copper mining on salmon
ecosystems in the Bristol Bay watershed; the 6.5 billion ton mine is a large mine. Because this size
mine is on the lower bound of a maximum size, it is a conservative assumption for the risk
assessment. Thus, for the purposes of the assessment, it is not necessary to hypothesize an even
larger mine.
CAROTHERS RESPONSE: EPA responses are sufficient.
EPA FINAL RESPONSE: No response required.
Dennis D. Dauble, Ph.D.
The hypothetical mine scenario initially appeared realistic and useful in terms of potential project
scope. However, it was apparent during the public hearing, and upon further discussion between
members of the panel, that assumptions on mine size should be revisited based on deposit
characteristics and extraction potential. Also, assumed practices and operations should be verified
against current best-practice and State of Alaska permitting guidelines.
EPA RESPONSE: The revised assessment includes a smaller sized mine that is based on the
median-sized porphyry copper mine on a worldwide basis. The State ofAlaska does not have
permitting guidelines that address the size of a mining operation. Land use activities were
previously subject to stipulations meant to minimize surface damage or disturbance under 11
Alaska Administrative Code (AAC) 96.140, but this regulation was repealed in December 2002.
The State does have statutory and/or regulatory requirements for an approved Plan of Operations
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(11AAC 86.800), a Reclamation Plan (Alaska Statute (AS) 27.19.30) and appropriate Financial
Assurance (AS 27.19.040).
DAUBLE RESPONSE: The three mine scenarios as presented in the revised Assessment cover
a realistic range of potential development.
EPA FINAL RESPONSE: No response required.
Referenced literature provides appropriate context, however, I cannot help believe that information
on environmental impacts from past mining activities conducted in the Rocky Mountain metal belt
would be relevant to this assessment in some cases. It is also possible that recent published
information from Holden Mine in northern Washington State would help establish context for effects
of leachates and model results that predict downstream transport of tailing material in a wilderness
setting, for example.
EPA RESPONSE: Environmental impacts from historic mining are the basis for understanding
that risks from hazards of mining need evaluation. Modeling of tailings transport was based on the
expected characteristics of tailings for the Pebble deposit. There is an expanse of literature on
Superfund sites and interactions of metals associated with sediments and their leaching. We
included a number of selected sites in our background information, but to include all possible sites
would get further away from the scope of the assessment, which was to evaluate potential effects
within the Bristol Bay watershed
DAUBLE RESPONSE: In this reviewer's opinion, the writers did an adequate job of providing
comparative information from other mineral development sites.
EPA FINAL RESPONSE: No response required.
Gordon H. Reeves, Ph.D.
No comments on this question.
Charles W. Slaughter, Ph.D.
Given the available information base for the ore deposits of the Bristol Bay watershed, and the
publicity which has attended the Pebble planned development over the past several years, the
Assessment's hypothetical mine scenario seems fairly realistic. Further, it is appropriate that the
Assessment consider the probable impacts of other future mineral development projects once an
initial entry (presumably Pebble-Northern Dynasty Mnerals) has been accomplished. Such
subsequent development - "cumulative effects over a long time period" - could (and should) receive
more emphasis than is accorded in the Assessment.
EPA RESPONSE: The assessment of cumulative effects of multiple mines is given more emphasis
in the new Chapter 13.
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SLAUGHTER RESPONSE: Given the present relatively unaltered state of the Bristol Bay
watershed, the inevitable and irreversible cumulative effects - on salmon and on the entire
human-landscape-wildlife biota complex - of additional mines and ancillary and induced
development are certainly as significant in the long term as is the initial (proposed) Pebble
mine scenario(s). Chapter 13 is a great improvement to the Assessment, and does recognize
many probable consequences and cumulative effects of multiple mines and "induced
development". The attempt to provide an overview of the primary current mining claims is
appreciated. This leads to another question: Does EPA, or any other State or Federal entity,
have legal or "moral" standing to more fully evaluate such long-term cumulative impact on this
large, undeveloped, presently controversial piece of the United States?
EPA FINAL RESPONSE: With respect to the legal authority of agencies to evaluate cumulative
impacts, implementing regulations for various statutes require that cumulative impacts be assessed
during project review/permitting. Examples are the National Environmental Policy Act (NEPA)
and the Clean Water Act (CWA) 404permit program The Council on Environmental Quality
regulations (40 CFR § 1500 -1508) define the impacts and effects that nmst be addressed and
considered by federal agencies in satisfying the requirements of the NEPA process. These include
direct, indirect, and cumulative impacts. The NEPA regulations at 40 CFR Parts 1508.7 define
cumulative impact as "the impact on the environment which results from the incremental impact
of the action when added to other past, present, and reasonably foreseeable future actions
regardless of what agency (federal or non-federal) or person undertakes such other actions."
Cumulative effects on an aquatic ecosystem are also required to be considered by the permitting
authority pursuant to the CWA 404 regulations at 40 CFR Part 230.11(g). 40 CFR 230.1(d) states:
"Fundamental to these Guidelines is the precept that dredged or fill material should not be
discharged into the aquatic ecosystem, unless it can be demonstrated that such a discharge will not
have an unacceptable adverse impact either individually or in combination with known and/or
probable impacts of other activities affecting the ecosystems of concern."
Your comment also asks whether agencies have "moral standing" to more fully evaluate long-term
cumulative impacts. Although agencies do not act based on moral grounds, agencies do have
guiding principles by which they operate. These principles form the backdrop for agency decision
making. For example, EPA's stated mission includes the statement that "environmental protection
is an integral consideration in U.S. policies concerning natural resources, human health,
economic growth, energy, transportation, agriculture, industry, and international trade, and these
factors are similarly considered in establishing environmental policy." Similarly, the United States
Army Corps of Engineers and the State ofAlaska have principles that guide their decision making
with respect to the environment. The United States Army Corps of Engineers Environmental
Operating Principles "were developed to ensure that Corps of Engineers missions include totally
integrated sustainable environmental practices. The Principles provided corporate direction to
ensure the workforce recognized the Corps of Engineers role in and responsibility for sustainable
use, stewardship, and restoration of natural resources across the Nation and, through the
international reach of its support missions." In 1971, the Alaska Legislature set out the Alaska
Department of Environmental Conservation's mission as follows: "to conserve, protect and
improve its (Alaska's) natural resources and environment and control water, land and air
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pollution in order to enhance the health, safety and welfare of the people of the state and their
overall economic and social well being." These broad policy or mission statements could support a
decision to take a comprehensive look at the long-term cumulative impacts of mining in the Bristol
Bay watershed
John D. Stednick, Ph.D.
The document does not adequately bound the range of mine scenarios. The minimum mine
development scenario is not adequately addressed. A frequent criticism during the public comment
session was that mine plans presented in the assessment are not representative of current standards. A
compilation of existing world porphyry mine complexes as well as other types of mines specific to
Alaska would better inform the reader of mining processes and potential risks. The physical setting in
Southwest Alaska is not the same as the Bingham Mine in Salt Lake City. Currently, the document
refers to a particular mine in a particular risk assessment (stressor), e.g., the Fraser River for salmon,
Aitik for chemistry, and Altiplano for pipeline failures.
EPA RESPONSE: The revision includes a smaller mine size that represents the worldwide median
size for a porphyry copper mine (Singer et al. 2008), to help with the issue of the range of
scenarios. EPA disagrees that the mine scenarios evaluated are not representative of current
standards. This view apparently stems from use of the term "good" rather than "best" practices in
the draft assessment. The reason for using that term is that the term "best management practices"
is a term generally applied to specific measures for managing non-point source runofffrom
stormwater (40 CFR Part 130.2(m)). Measures for minimizing and controlling sources ofpollution
in other situations are often referred to as best practices, state of the practice, good practice,
conventional practice, or simply mitigation measures. We assume that these types of measures
would be applied throughout a mine as it is constructed, operated, closed, and maintained post-
closure, regardless of the qualifier that one wishes to place with it. A text box was added to the
revised Chapter 4 that discusses terms to help clarify our intention for descriptors used The
Fraser River example was considered because it had been used as an analogue by others, but was
dismissed as not representative of Bristol Bay. Other mines that are noted in the assessment are
illustrative of specific issues only and are not used for risk evaluation in the Bristol Bay
watershed Atlhough physical settings are not the same, the components and the impacts are
similar and thus included to help a reader understand where and how these things occur.
The Bureau of Land Management has identified certain lands that will be excluded from
development. This reference needs to be followed up.
EPA RESPONSE: The purpose of the assessment was to estimate potential impacts of large-scale
surface porphyry copper mining on salmon ecosystems in the Bristol Bay watershed This
presupposes that our mine scenarios are located in areas that are not excluded from development.
The majority of land in the two watersheds is state land that is available for mine development,
and Figures 2-3 and 2-4 now indicate protected areas within the Bristol Bay watershed
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Roy A. Stein, Ph.D.
Hypothetical Mine Scenario. Though mining does not lie within my area of expertise, I thought that
this scenario helped me understand the potential impact of a mine of this magnitude in a wilderness,
pristine watershed. I find it difficult to comment as to whether this scenario is realistic and sufficient,
though I did use this scenario to guide my comments below. From the text, it is apparent that this is a
realistic scenario, based on documents filed by the company with the Canadian government. This
makes this scenario the most realistic one could expect.
Minimum and Maximum Mine Size. For me, as an ecologist, this bounding helped me to
understand the potential impacts of the Pebble Mine, though I did not understand what the
probability of either mine size happening in the near term. Understanding these probabilities
would be helpful to the readers.
Mine-Size Continuum. Is it more likely that the initial Pebble Mine will be maximum or
minimum in size? Wouldn't it be far better to review a continuum of mine sizes from the
smallest that is economically feasible to one that is intermediate in size and then to one (or
two) that would take to the largest realistic mine size? With this continuum, the reader begins
to understand the overall impact of various mine sizes on the Bristol Bay ecosystem. Some
reflection on these mines sizes and their impacts would have helped me interpret the
Environmental Risk Assessment with some additional insight.
EPA RESPONSE: The State ofAlaska does not have permitting guidelines that address the size of
a mining operation. Many identified deposits never become developed mines for various reasons,
and it is unknown how many deposits exist and are economically viable for exploration of mining
feasibility. Once it is decided to develop a site, there are a number of things that must occur before
a mine begins operation. Thus, it is not possible to predict the probability of either mine size
happening in a specific period, at least with any certainty. All we can say is that there are deposits
that have the potential to be mined in the future.
It is more likely that an initial mine would begin at a smaller scale and become larger and perhaps
be permitted in stages of increasing size. However, there are different approaches in how plans are
presented and these depend on multiple factors, including economics and projected costs/gains in
prices of the metal being mined For example, if it were not economically viable to mine only a
small part of a known large deposit, a larger mine would be proposed and planned for. The revised
assessment includes a size scenario that represents the worldwide median-sized mine to provide
more of a continuum of sizes.
One Watershed. Given the productivity of salmon from these two river systems (50% of the
sockeye salmon in Bristol Bay are produced from these rivers), might there be some thought given to
limiting the mining operations to a single watershed, either the Nushagak or the Kvichak (page ES-
2)1 In so doing, in a single stroke, the impact of this mine on salmon is reduced by 50% or more.
Could the Pebble Mine be confined to one watershed, such as where the majority now falls - in the
Nushagak River (both the north and south forks of the Koktull River) watershed? Even so, this
suggestion becomes especially pertinent to Chinook salmon spawning in the Nushagak River, for this
run is "near the world's largest" (page ES-5), but yet the Nushagak watershed is small relative to
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other watersheds (such as the Kuskokwim and the Yukon) where Chinook salmon are abundant. As a
result, any impacts to the watershed by a mine of this size are magnified, another concern when
considering this location. Without mining expertise, I cannot judge whether it would be possible to
mine in only one of the watersheds, rather than both. Even so, some consideration should be given to
this suggestion.
EPA RESPONSE: Restricting impacts to one watershed would change the risks, and could be a
part offuture mine plans. We chose to represent a suite of realistic mine scenarios based upon
preliminary mining plans and the location of the ore deposit which lies in both watersheds.
William A. Stubblefield, Ph.D.
No comments on this question.
STUBBLEFIELD RESPONSE: No additional comments on this question.
EPA FINAL RESPONSE: No response required.
Dirk van Zyl, Ph.D., P.E.
The hypothetical mine scenario adopted by the EPA relied almost exclusively on the document
prepared for Northern Dynasty Minerals (NDM), one of the partners of the Pebble Limited
Partnership. Developing a mine plan for a specific ore body is a large task and is undertaken by a
large team of engineers and scientists. In the process of developing a mine plan many options are
considered for each facility and its components, including mining methods, process design options,
waste rock management options, tailings management options, shipment of product, etc. The
hypothetical mine scenario was prepared by an independent consulting company for one of the
partners and this plan does not necessarily represent the design and management options that will be
selected for developing this ore body. Because of ore grades and the deposit style, it is most likely
that an open pit mine will be developed as assumed in the report for the western lower grade ore
body and that underground mining will be used for the eastern higher grade ore body. The size of the
ore body and the strip ratio for an open pit mine are completely dependent on metal prices and
production costs at the time of mine development. Metal prices and production costs will also be a
major factor in deciding whether to first develop an underground mine instead of an open pit mine.
While some of the components of the final mine may contain elements of the conceptual mine, it is
impossible to know whether the hypothetical mine scenario is realistic, as will be further discussed in
the comments below.
EPA RESPONSE: It is acknowledged in the assessment that the mine scenarios might not look
exactly like a mine presented in a mining plan. The assessment is not a mining plan and is not an
evaluation of a mining plan; it simply uses current information for the Pebble deposit because it is
a large ore deposit which has had extensive exploration with potential for development in the near
future. An additional scenario has been included in the revision to match the worldwide median
mine size and show a better continuum of scenarios possible. We consider our scenarios to be
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realistic, as they were presented as possible layouts for the Pebble deposit and stated in Ghaffari et
al (2011) as being "economically viable, technically feasible, and permittable".
To address the issue of sufficiency it is necessary to understand the range of potential outcomes
related to the various options. For the most part, the EPA study used the information from the NDM
document for evaluating impacts to salmonids. Using different options, both technological as well as
site selection, for some or many of the facilities could result in impacts that are different from those
described in the report. I would therefore suggest that using only the present hypothetical mine
scenarios is insufficient. There could be a range of impacts, such as the surface areas of facilities,
which in some cases could be smaller than what was chosen and in other cases larger. However, this
does not mean that the hypothetical mine represents "average conditions." I therefore consider the
mine scenario not sufficient for the assessment.
EPA RESPONSE: It is acknowledged in the assessment that the components in the mine scenarios
might not be exactly what would be proposed in a mining permit application for this location or
for other locations within the Bristol Bay watershed The purpose of the assessment was to
evaluate potential impacts of large-scale surface porphyry copper mining in the Bristol Bay
watershed, so the assessment was not meant to represent "average conditions." However, an
additional mine size scenario has been included in the revision to match the worldwide median
porphyry copper mine size and show a better continuum of scenarios possible.
The minimum and maximum mine sizes selected by EPA are 2 billion tonnes mined over 25 years
and 6.5 billion tonnes mined over 78 years; in both cases, the daily ore processing rate is 200,000
tonnes. As indicated above, the final economic mine size at the time of development will be
determined by metal prices and production costs. Note that production costs, as used here, include all
the considerations related to regulatory, environmental and social aspects of the mine and its
environs. Mining companies typically make investment decisions for periods of 20 to 30 years. It is
seldom, if ever, that a new investment will be made based on a 78 year mine life; however, the
upside potential will be taken into account when an investment for a shorter mine life is made. It is
also unlikely that environmental regulatory agencies will consider issuing a permit, including closure
plans, etc. for a 78-year project. Furthermore, even if the mine ultimately continues for 78 years, it is
certain that the operating and environmental control technologies and societal expectations will
change in that period and therefore the elements used by EPA for the maximum size hypothetical
mine will certainly not be valid for such a long mine life. It is therefore my conclusion that assuming
the development of a 2 billion tonne ore body is realistic, but that assuming development of a 6.8
billion tonne ore body, using static technology assumptions, is not.
EPA RESPONSE: Although it is true that an actual mine likely would be permitted in increments,
the assessment never stated that the 78-yr scenario would not be done this way. In fact, the
assessment does not discuss how such scenarios would be permitted at all, and to do so is outside
the scope of the assessment. The purpose of the assessment is to estimate potential impacts of
large-scale surface porphyry copper mining on salmon ecosystems in the Bristol Bay watershed,
and that necessarily assumes that the mine scenarios are permitted It is true that some
technologies would have advanced over time from 'day one' of mine scenario development, and we
acknowledge this in our assessment. It is impossible to predict, however, how impacts from use of
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future technologies would differ from those in use today, or how they would change conditions
existing at the time they began being used We can only present and predict potential impacts
based on use of the most appropriate technologies available at the current time. No change
suggested or required
The EPA assessment report includes a range of the literature and reports in evaluating the selected
mine scenario. However, I have a number of specific comments about various aspects of the report as
well as the references.
Good practice vs. best practice. On p. 4-1 of the report, the EPA states: "Described mining
practices and our mine scenarios reflect the current practice for porphyry copper mining around the
world, and represent current good, but not necessarily best, mining practices". EPA does not clarify
this decision, nor does the report clarify the distinction between "good" and "best" practices. It can
only be concluded that "best" will be better than "good". On the basis of this, it is inconceivable to
me that the Bristol Bay communities, the Alaska regulatory authorities as well as Federal Regulatory
Authorities will not demand that the company follow "best mining practices," however that is
defined at the time. It is also inconceivable to me that the company will not follow "best mining
practices" in the design and development of such a mine. During the engagement processes, the
stakeholders will have to agree what represents "best" practice in the design of the mining project. It
is important to note that most of the failure statistics used as a basis for the evaluations in the report
are derived from data gathered over the last 50 years or so (e.g. refer to p. 4-45 of report). It may be
argued that this information is mostly for mines following "good" practices and, in many cases, for
projects that had a lower standard of care. To my knowledge, there are no statistics available that
compare failure rates of facilities designed and operated under "good" practice to those designed and
operated under "best" practices, whatever definitions are used for "good" and "best".
EPA RESPONSE: The term "best management practices" is a term generally applied to specific
measures for managing non-point source runofffrom stormwater (40 CFR Part 130.2(m)).
Measures for minimizing and controlling sources ofpollution in other situations often are
referred to as best practices, state of the practice, good practice, conventional, or simply mitigation
measures. We assume that these types of measures would be applied throughout a mine as it is
constructed, operated, closed, and post-closure, regardless of the qualifier that one wishes to place
with it. To remove any ambiguity and subjectiveness of terms "good" or "best", we have removed
them in the revision and have added Box 4-1, which includes definitions for several terms used
EPA also is not aware of any statistics available that compare dams designed (and/or operated)
under different standards; however, the probabilities for dam failure used in the assessment were
not derived solely from the historical record Historical failures were discussed as supporting
background information and present a defensible upper bound on the failure probabilities. The
failure probabilities used in the assessment are based on Alaska's dam classification and required
safety factors applied to the method of Silva et al (2008). The data presented by Silva et al (2008)
consider only the annual probability offailure from slope instability, but the methodology is
equally applicable to other failure modes. The discussion offailure probabilities in the revision
(Chapter 9) is expanded to clarify this issue.
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VAN ZYL RESPONSE: The author agrees that from a regulatory perspective "best
management practices" (BMPs) is typically used for non-point source runoff. However, the
term is also in much broader use in practice to refer to other activities and this is somewhat
recognized. Addition of Box 4-1 helps to clarify this point.
EPA FINAL RESPONSE: No response required.
Mine scenarios. The executive summary indicates (p. ES-11): "The mine scenario includes
minimum and maximum mine sizes, based on the amount of ore processed (2 billion metric tons vs.
6.5 billion metric tons), and approximately corresponding mine life spans of 25 to 78 years,
respectively". This seems to indicate that the mine life cycle in the first case consists of 25 years of
operational life followed by closure and, similarly for the second case, 78 years of operational life
followed by closure. However, a careful review of the water management section (section 4.3.7)
indicates that this is not the case. The EPA water balance calculations are simplified to a set of
deterministic values in Table 4-5 for four water management stages during the overall mine life
cycle: start-up, operations minimum mine (25 years), operations maximum mine (78 years), and
post-closure. For post-closure, only the 78-year mine life numbers are used. It therefore seems that
EPA is not considering that the 25-year mine will close, but that its life will automatically be
extended to 78 years. Does this mean that the EPA really does not evaluate the minimum mine size
completely, i.e. the 25-year mine life followed by closure? It is important that this be clarified as it
would be inconsistent not to evaluate closure of the 25-year mine. It is possible that additional
evaluations, or at least additional explanations, will be required to clarify this.
EPA RESPONSE: The reviewer is correct. Our water balance calculations only explicitly present
the closure of the Pebble 6.5 scenario. The water balance for the Pebble 0.25 and the Pebble 2.0
scenarios would be similar, but in those scenarios there would be no water captured in TSF 2 or
TSF 3 and the amounts captured in the pit would be proportionally smaller, as they are in the
operating scenarios. While the pit is filling in each of the three scenarios, the total amount of
water captured is slightly less than the amount captured during operations, and about 35% to 45%
of the water captured is available for reintroduction to the streams. Once the pit is full, the amount
captured at the mine pit area drops substantially and 100% of the captured water is reintroduced.
Post closure flows for the three mine scenarios are presented in Table 6-8.
Tailings management technologies. Ongoing technology development has resulted in a broader
range of tailings management options than only slurry tailings disposal. Filtered dry stack tailings can
be considered as a realistic option, even for mines with higher production rates. Flotation of
remaining sulfides in the tailings before deposition is also a realistic option for mines; it has been
done successfully at the Thompson Creek Mine in Idaho for the last 18 plus years. While these
technologies are mentioned, they are not selected for reasons such as technology not being
appropriate for the climatic conditions and concerns with disposal of pyrite waste. Both of these are
not insurmountable technical issues and adopting such management options will reduce failure
probabilities and potential impacts following a failure. The failure mode of a filtered dry stack
facility not containing sulfides will be completely different from a slurry impoundment and the
potential environmental impacts of these other tailings management options will definitely be far
smaller than those for the selected mine scenario using slurry tailings disposal.
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EPA RESPONSE: Selective flotation to lower the pyrite content has been added to the discussion
of processing in Chapter 4 and referenced in Chapter 6 as being done in the assessment scenarios.
How tailings are managed within the impoundment can affect water chemistry and a dry stack
with sulfides removed may produce the best water quality results after reclamation if the fate of the
sulfide tailings is never considered. According to Ghaffari et al. (2011), 14% of the tailings
produced would be pyritic (with the selective flotation method used), which equates to an average
of28,000 tons/day in a 200,000 tons/day mining operation, or over 255 million tons during a 25-
year estimated lifetime for that scenario. These tailings need to be managed in such a manner that
oxidation does not lead to acidic drainage and the most effective way is to deposit them
subaqueously. Additionally, a "rule of thumb" for design of dry stack tailings is to allot 25 acres
for every thousand dry tons of tailings per day over the life of a 20-year operation (SME Mining
Engineering Handbook 1973). Assuming our scenario of200,000 tons per day processed and that
99% of this material was waste tailings, this would amount to 4900 acres (25 *200,000 *.99/1000)
or 19.8 km2 over 20 years. This exceeds the internal surface area taken up by the TSFfor tailings
deposited over 25 years for the same mass of material processed per day by 5.6 km2; thus, even if
there were not a risk of the PAG tailings acidic leaching potential, dry stack tailings disposal at
this site would create additional surface area loss versus the scenario's traditional dam
VAN ZYL RESPONSE: The response refers to a "rule of thumb" from the SME Mining
Engineering Handbook (1973) about allotment of space for dry tailings. The author is not
aware of any hard rock dry tailings management projects in the 1970's, these really came to
being in the 1980's and 1990's. It is therefore not clear what experience base was used to
establish this "rule of thumb". The author has not reviewed the reference, however assuming
100 pcf density for the dry tailings the rule indicates a height of tailings stack of about 130 ft.
This clearly is dependent on the topography and there is no reason not to construct stacks that
are higher. There is no reason why the overall area covered by dry tailings should be larger
than the footprint of a slurry tailings deposit as the dry density of placed and compacted
tailings will be higher than that of slurry tailings. The statement that "
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are underground mines with high-grade ore and relatively low quantities of tailings (e.g.
Greens Creek, a lead, silver, zinc mine in southeast Alaska; and Pogo, a gold mine in
eastern interior Alaska).
It should also be noted that it is not only higher energy costs but also capital and other
operating costs that make this technology more expensive. However, if this tailings
management method results in lower environmental risks then it should be seriously
considered and potentially included in project considerations, even if only to enumerate the
lower risks, e.g., the tailings failure scenario will not occur because there is no fluid stored and
all surface water can be diverted. This issue of acid drainage can also be addressed in the
design of the facility, note that acid drainage collection and treatment from the tailings
impoundment is included in the present assessment.
EPA FINAL RESPONSE: We agree with the conmtenter that the statement "dry stack tailings
disposal at this site would create additional surface area loss versus the scenario's traditional
dam" is not correct and should be removed from our initial response. Information on dry stack
tailings management has been expanded in the final assessment (Box 4-7), and this information
clarifies that dry stack tailings management would not result in a larger tailings storage footprint.
Waste rock management. The waste rock management plan on p. 4-13 calls for the potentially acid
generating (PAG) waste rock to be separated from the rest of the waste rock and states that the "PAG
waste rock might be placed in the open pit at closure to minimize oxidation of sulfide minerals and
generation of acid drainage". However, on p. 4-33 it is stated that: "PAG waste rock will be
processed through the flotation mill prior to mine closure, with tailings placed into the TSF (tailings
storage facility) or the mine pit." These two alternatives represent completely different management,
economic and environmental conditions and are not consistent. Milling the PAG waste rock
represents a higher cost than placing the PAG rock in the pit and placing the PAG waste rock tailings
in the TSF will increase the size of the TSF. Placing the PAG tailings in the pit will set up a
completely different management scenario than placing the PAG waste rock in the pit. The EPA
should clarify which option or range of options they select for evaluation and use that consistently in
the assessment.
EPA RESPONSE: These statements have been made consistent. The revised assessment scenarios
include processing the PAG waste rock over the course of operations to minimize the length of
time a PAG waste rock pile would be on the surface, and thus minimize its potential for oxidation
and subsequent release of acidic leachate. There is no longer mention of PAG rock being disposed
in the pit at closure (Section 6.3.3).
Water balance and management - waste rock. Mine site water balance and management is a very
complex issue as recognized by the EPA on p. 4-27: "... water balance development is challenging
and requires a number of assumptions". Because of these uncertainties, complex probabilistic
dynamic models are employed at mines where the site details are better defined than that of the EPA
hypothetical mine scenario. The information in Box 4-2 indicates that the "captured flows include
water captured at the mine site and the TSFs (Table 4-5). The total amount of water captured at the
mine site includes net precipitation (precipitation minus evapotranspiration [footnote: during
operations most of these areas will not be covered with vegetation and the correct terminology here is
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"evaporation"]) over the areas of the mine pit, the waste rock piles, and the cone of depression
(without double-counting any areas of overlap)". On p. 4-23 it is stated that: "Monitoring and
recovery wells and seepage cut-off walls would be placed downstream of the piles to manage
seepage, with seepage directed either into the mine pit or collection ponds". Figure 4-9 shows this
schematically where leachate from the waste rock enters the groundwater that then flows to the mine
pit or to the monitoring and collection well. However, if net precipitation only includes the
components above (precipitation minus evapotranspiration), effectively excluding infiltration, and if
this net precipitation is captured from that waste rock pile (as stated in Box 4-2), then there should
not be any water available to infiltrate into the waste rock pile, i.e. there should not be any leachate.
All references to seepage from the waste rock piles are incorrect following the EPA's assumptions of
total capture of net precipitation. In addition, the approach that is used in the water balance is
inconsistent with observed field performance and descriptions in the literature, as is it difficult to
imagine a case where there is zero infiltration into a porous waste rock pile (e.g. Nichol et al., 2005
and Fretz et al., 2011). The EPA must clarify the whole water balance model and the evaluations. For
the assessment to have any credibility, the water balance and management evaluations should reflect
realistic conditions.
EPA RESPONSE: The term "evapotranspiration" has been corrected to 'evaporation' in the
revised assessment when discussing the operational phase. Total precipitation equals the sum of
evaporation, transpiration (where applicable), runoff, and infiltration. Net precipitation included
in the water balance includes all water falling onto the site components minus water leaving only
via evaporation (i.e. it includes both runoff and infiltration). Leachate/seepage water originates
from precipitation which has infiltrated the waste rock piles or tailings onto which it fell.
Therefore, the discussion of seepage is not incorrect, and there is no indication that the scenarios
represent "zero infiltration", as we discuss (as noted in the comment made) how seepage and
leachate are managed However, the water balance section has been revisedfor clarity (new
Section 6.2.2). As the commenter notes, the assessment discusses seepage collection systems.
However, the assessment does not assume total capture. Our water balance assumes that 50% of
the leachate that is lost from the TSFs and from the portion of the waste rock piles outside the
drawdown zone of the pit escapes into the groundwater and eventually into the streams.
Dam failure - tailings storage facilities. During operations, "water falling within the perimeter of a
TSF would be captured directly in the TSF, but runoff from catchment areas up-gradient of the TSF
would be diverted downstream" (p. 4-27). At closure, water would be removed from the TSF
providing more storage, but also maintaining a small pool to "keep the core of the tailings hydrated
and isolated from oxidation" (p. 4-32). This seems to assume that the diversion systems will be kept
in place and most likely will be upgraded to divert up-gradient surface water around the tailings
impoundment. It is likely that the design criterion for the upgraded diversion system during the post-
closure period will be the probable maximum flood (PMF) as is done at a number of mines. Dam
failure analyses were done assuming that the flood leaving the TSF includes the PMF inflow from
the up-gradient catchment, excess water on top of the tailings and 20% of the tailings volume (Box 4-
8). While one can argue that a failure including all these materials may be a plausible, although a
very low likelihood event during operations, it seems less probable that such a failure will take place
for the mine closure period when an upgraded diversion system is in place. Also, during the closure
phase, the tailings will consolidate and be less mobile. Note that the densification behavior of oil
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sand tailings referred to on p. 4-32 (i.e. the Wells, 2011 reference) does not apply to copper tailings.
The presence of clay minerals and bitumen in the mature fine tailings portion of the oil sand tailings
is the source of the different behavior (Znidarcic et al., 2011).
EPA RESPONSE: It is assumed that post closure scenarios will have drainage facilities in place
that could safely pass storm events. However, the decision was made to assume a failure that was
consistent for both the operational and post operation scenarios. The PMF would overtop the
main dam of the TSF and drain into the North Fork Koktuli as a representative failure, assuming
that drainage facilities were either not yet operational or had failed. It is important to note that the
PMF peak flow generated only 291 cms, which is small when compared to the peak flow release at
the failing dam (149,263 cms and 11,637 cms for the large and small failures, respectively). 20%
was selected to represent the volume released from the TSF because it fell within a reasonable
range when compared to release volumes of historic failures. The 20% volume included both
solids and pore water.
VAN ZYL RESPONSE: The author indicated in his 2012 [comments] that the analogy to
consolidation of oil sand tailings is incorrect. The Second Draft includes the following
statements: "Although oil sands are different from porphyry copper tailings, the principle is the
same. Lack of data specific to porphyry copper tailings suggests a cautious approach, so we do not
assume that the tailings consolidate to a fully stable land form. Thus the system may require
continued monitoring to ensure hydraulic and physical integrity in perpetuity'1''. The author agrees
that the principles are the same, however where it is estimated to take 200 years plus for a
mature fine oil sand tailings facility to consolidate, a hard rock facility will consolidate during
the operational life (refer to Caldwell et al, 1984; Oliveira and van Zyl, 2006a and 2006b).
While long-term monitoring will be required, especially if the decision is made to store water
on the impoundment, the tailings will be completely consolidated, i.e. no excess pore pressures
will remain.
Tailings specific gravity (Second Draft p. 9-12): The report notes that the specific gravity of the
bulk tailings is 2.61 and that of the pyritic tailings is the same. This is incorrect. The specific
gravity of pure pyrite is about 5.0, however when mixed with other minerals as in tailings one
can typically use a value of 4.2 to 4.5. Please correct this and update the calculations on p. 9-12.
EPA FINAL RESPONSE: Wells (2011) and Oliveira and van Zyl (2006a and 2006b) agree that
the consolidation of tailings with low sand content may slow substantially or effectively cease in a
relatively short period of time after operational loading ends. The assessment makes the same
point, noting that continued strength gain from long-term consolidation cannot be relied upon and
that confirmation would be required to document continuing strength gains.
We performed a literature search of copper tailings specific gravities (SG) and found reported
values ranging from 2.67 to 4.2. Most of the cited references do not state a density for a separate
pyritic tailings stream, but the citations pertain to mines that have ore with high pyrite content.
Higher iron (SG = 7.9) or higher pyrite (SG = 5.0) content appears to correlate with higher
specific gravities of the tailings. Although the literature search supports the reviewer's statement
that the pyritic tailings solids could have a higher specific gravity, it is inconclusive with respect to
the Pebble deposit pyritic tailings stream. Values in the range proposed by the reviewer appears to
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be inconsistent with the ore and tailings specific gravities reported in Ghaffari et ah (2011). For
the greatest consistency with the field data and with the detailed nuiss balance analyses reported by
Ghaffari et al. (2011), we use specific gravity values of 2.63 for the bulk tailings solids and 3.00 for
the pyritic tailings solids. Because the pyritic tailings make up only about 14% of all the tailings,
variation in the pyritic tailings specific gravity up to as high as 4.2 would only affect the average
tailings nuiss and volume properties by about 1 %.
Reclamation slope of waste rock. On p. 4-32 it is stated that: "We assume that NAG waste rock
would be sloped to a stable angle (less than 15%) (Blight and Fourie, 2003)". I contacted Profs.
Geoff Blight and Andy Fourie about this statement and received the following response from Prof.
Blight: "The only reference to 15 degrees (not 15%) slopes is the following, talking about the outer
tailings, not waste rock covered, slopes of decommissioned TSFs: "it must be remembered that the
outer slopes will need to be rehabilitated, and that for vegetation to be stable, and surface erosion
minimal, the maximum outer slope should not exceed 15 degrees." This error in reference must be
corrected; it is recommended that more typical closure slopes of about 30% (or 3H:1V, about 18
degrees) for waste rock should be used in the evaluations.
EPA RESPONSE: The text has been changed to correctly read 15 degrees in Chapter 4 and
Appendix I.
Phyllis K. Weber Scannell, Ph.D.
The Environmental Assessment discusses a hypothetical mine (given that mine plans have not been
developed). Page 4-5 of the document states that "rocks associated with porphyry copper deposits
tend to straddle the boundary between net acidic and net alkaline.." The Pebble Project
Environmental Baseline Report (SRK 2011, Chapter 11) summarizes testing on the samples from the
pre-Tertiary porphyry mineralized rock in Pebble East Zone (PEZ) and Pebble West Zone (PWZ).
The metals leaching/acid rock drainage study showed acidic conditions occurring immediately in
core with low NP, but the average delay to onset of acidic conditions was estimated to be about 20
years. Copper was leached in the highest concentrations, but Co, Cd, Ni, and Zn also leached from
samples from PEZ. Wacke (sedimentary rock) samples from PEZ and PWZ leached As, Sb, and Mo,
in addition to Cu. (SRK, page 58). The available information on acid generation and metals leaching
appears to be preliminary. Development and permitting of a viable mine plan will require extensive
sampling and data analysis of ore samples, plans for classifying waste rock (as PAG and NAG), and,
possibly, plans for collecting and treating runoff and seepage waters.
EPA RESPONSE: We agree that developing and permitting a viable mine would require extensive
information. The assessment is not a mining plan. The scenario presents a suggested treatment
option for mining influenced water and settling ponds for water that is simply stormwater runoff.
No change required.
WEBER SCANNELL RESPONSE: Reviewer agrees that no change is required; however,
reviewer still believes that the available information on metals leaching was not adequately
addressed in the initial draft Environmental Assessment. Perhaps some statement in the
Assessment that addresses the need for in-depth sampling for acid generation and metals
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leaching would suffice. The primary concern of this reviewer is that the Assessment did not
adequately discuss potential leaching of metals other than Cu and that much of the information
contained in the SRK report was not used.
The reviewer notes that Section 8.2.2.2 Other Metals has been added to the revised draft
Assessment. This new section provides much needed information on the toxicity of elements
other than Cu and recognition that these elements may be of concern. New Section 8.2.2.3
addresses concerns of total dissolved solids, a potentially significant stressor to aquatic
communities. Inclusion of these two sections greatly strengthens the revised Assessment.
EPA FINAL RESPONSE: We agree that the PLP's leaching data appear to be preliminary and
additional leach testing is advisable. Uncertainties associated with the leaching data are listed in
Section 8.2.5. The assessment used mean PAG and NAG leachate concentrations because, based
on Ghaffari et al. (2011), waste rock would be segregated only into those two categories. However,
if rock is segregated by other types such as wacke, they should be assessed separately.
The Environmental Assessment seems a bit premature in making an assessment of the potential for
acid rock drainage (ARD) or metals leaching (ML). Data on metals other than Cu are insufficient and
possible toxicities to fish are not addressed. Further, the description of the potential mine may not
reflect a likely mine scenario. It is difficult to calculate potential risks to the environment without a
specific mine plan. The section of the Environmental Assessment should be revised as more data on
ARD and ML become available.
EPA RESPONSE: The assessment uses the geochemistry data that are available from the Pebble
Limited Partnership. Copper was emphasized in the review draft because we believed, and still
believe, that it is the contaminant of greatest concern. Toxicities to fish of the other metals were
not discussed because they had been screened out. However, the revised assessment explains the
screening process and the selection of copper in more detail in a new section on the identification
of stressors of concern (Section 6.4.2) and more metals have been added to the screening
assessment. The toxicities of all metals reported in the leachate are now addressed either as
individual elements or, in the case of major ions, as contributors to total dissolved solids. The mine
scenario is based on the most recent preliminary plan released by Northern Dynasty Minerals
(Ghaffari et al. 2011).
WEBER SCANNELL RESPONSE: The reviewer is pleased that this additional information
has been added.
The reviewer notes the additional information on different elements and total dissolved solids,
as noted above.
EPA FINAL RESPONSE: No response required.
Paul Whitney, Ph.D.
Reclamation Plan. I am not familiar with the Northern Dynasty Minerals mine plan. I wonder if their
mine plan includes a Reclamation Plan. If not, why not? If their mine plan includes a Reclamation
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Plan, why isn't it presented as part of the Bristol Bay Assessment? The feasibility of reclaiming the
waste rock and tailings areas and possibility the pit (page 4-23, last para, last sentence) seems
important for evaluating the acceptability of the example mine. I am not aware of any mine
regulating agency that does not require a Reclamation Plan as part of a mine application. I wonder if
a Reclamation Plan that involved placing waste rock and tailings back in the pit and reducing surface
infiltration would greatly reduce the need for water treatment.
EPA RESPONSE: The assessment is not a mine plan. The Northern Dynasty Minerals document
relied upon for information in the assessment (Ghaffari et al 2011) is a preliminary mine plan
and does include conceptual reclamation measures which we have used in our scenarios. The
State of Alaska requires a Reclamation Plan of all mining facilities unless they are very small (AS
27.19.010). EPA's revised scenarios utilize blending throughout the mine life to eliminate the need
for long-term storage of PAG waste rock. Reclamation activities for the scenarios are discussed
more clearly in the revision and are activities that are considered feasible and common at other
similar existing mining sites. The scenarios in the assessment assume that reclamation is properly
completed, but concentrates the discussion on impacts that are expected even with such activities.
Best Mining Practices. The assessment refers to the example mine plan as having both the "best"
mining practices (e.g., page ES-10, five lines from the bottom) and "not necessarily best" mining
practices (e.g., page 4-17, four lines from the top). Both of these statements can't be accurate.
EPA RESPONSE: With regard to the terminology of "best", "good", or other terms for the
practices used, what was intended to be conveyed is that we have assumed modern mining
technology and practices. The terms are qualitative when generally interpreted, or have a
regulatory meaning (best management practices), and thus we have eliminated their use in the
revised assessment to avoid confusion. These terms have been clarified in Box 4-1.
Noise Levels. The mine plan should provide information on the location, frequency, and size of
blasting, sound level isopleths around the mine, and efforts to minimize sound levels as the mine
develops. I wonder if a majority of the sound levels will attenuate as mining activities move deeper
into the ground or if will there be a hundred years of blasting at the surface level. The interviews with
the villagers indicate that blasting and helicopter noise is a concern (Appendix D, Cultural
Characterization, page 94). A characterization of current noise levels in relation to the area and
timing of current and past wildlife use would help to determine if the whole or parts of the
watersheds are less than pristine.
EPA RESPONSE: Noise from large-scale mines is outside of the scope of this assessment because
it is not known to affect salmonid populations. EPA agrees that a full evaluation of any future
mining permit applications and subsequent National Environmental Policy Act Environmental
Impact Statements would consider these direct effects on wildlife.
Water treatment during the winter. I wonder if it will be possible to treat water during the winter.
Will such treatment have to occur in a warm building? If so, what are the temperature consequences
of releasing warm treated water into streams?
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EPA RESPONSE: Although water quality standards for temperature are directed toward summer
maximum temperatures, we emphasize the importance of the year-round thermal regime to which
salmon are adapted Abnormally warm temperatures could accelerate egg maturation and reduce
survival of incubating salmon. We state that a protective approach would discharge water that met
baseline thermal regime conditions throughout the year, and describe the risks associated with
failure to meet this regime.
Yes, it is possible to treat water during the winter, and treatment facilities would be contained in
structures to prevent freeing of the treatment plant. While the Alaska water quality standards (18
AAC 70) do contain maximums for water temperature, even the most stringent of these (13°C) may
be too high for winter-time discharge. Very likely, following a permit application, ADF&G would
determine an appropriate temperature for winter discharge and the facility would have to meet this
value, especially for discharges to anadromous streams. Temperature can be easily lowered during
the winter by exposure to ambient air.
Cone of Depression. I have worked on pit mines where hydrogeologists model the lateral extent of
the cone of depression and have mapped the lateral extent as an area around the pit. The lateral extent
of the cone of depression, illustrated in Figure 4-9, appears to be underestimated and has no effect on
streams or wetlands. The figure has no scale. Is the lateral extent of the cone of depression in Figure
4-9 based on modeling (see Box 4-2, para 3, last sentence)? If so, how many NWI wetlands and
meters of stream are in the area used for the model? If there are wetlands or streams in the modeled
area, how far down stream will the cone of depression influence stream flow and wetland hydrology?
The information in Box 4-2 doesn't clearly (at least to me) deal with the proportions of run-on and
run-off water. If the diverted run-on water is supposed to mitigate the cone of depression, will it be
available for downstream resources? Why won't diverted water seep back into the near-by pit versus
mitigating the cone of depression? The answer to these questions is on page 5-72, but merely
indicating there will be a reduction is not very informative.
EPA RESPONSE: The cone of depression is now projected to dewater streams and wetlands with
which it intersects. These losses are incorporated into the water balance calculations used to
estimate changes in downstream streamflow presented in Chapter 7. The lateral extent of the cone
of depression was estimated using the Dupuit-Forcheimer discharge formula for steady-state
radial flow into a fully penetrating well in a phreatic aquifer with a diameter equal to the average
mine pit diameter. The radius of influence was determined by balancing the net precipitation
falling within the cone of depression with the calculated flow into the mine pit. Section 6.2.2.1 and
Box 6-2 in the revised draft (Section 4.3.7 and Box 4-2 in the original draft assessment) contain
additional details on the methodology.
Our estimate of the mine pit inflow agrees closely with the estimate provided in Ghaffari et al.
(2011). The estimated cone of depression would extend about 1.2 km beyond the pit rim The water
within the cone of depression that would flow to the mine pit is included in the water balance. The
revised assessment presents estimates of the changes in streamflow at individual downstream
gages.
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Figure 4-9 (now Figure 6-5) is merely a schematic of the flows and is not to be interpreted as an
exact representation of the expected flow regime. The figure is not to scale and is not based on
modeling.
All of the precipitation falling within the cone of depression is considered to flow into the mine pit.
These losses are incorporated into the water balance calculations used to estimate changes in
downstream streamflow presented in Chapter 7. Streams within the cone of depression would dry
up. The assessment assumes that water from streams upstream of the cone of depression would be
diverted through pipes or channels to locations on streams downstream of the cone of depression.
The diverted water would not seep or flow into the mine pit.
Run-on and run-off water terminology. I am used to referring to up gradient or adjacent water that
runs onto the pit or tailings facilities as run-on water and to water from the mine or storage facilities
as run-off water. The assessment doesn't always distinguish these two types of water. For example,
on page 4-13, line 6 refers to precipitation run-off water as up gradient water. On page 4-26, the first
bullet refers to run-off water as water running off mine facilities. The terminology overlap makes it
difficult (at least for me) to understand how the run-on and run-off water will be captured and
diverted around the mine facilities or used for other purposes. In addition to calculations, diagrams of
the diversions would be helpful. Will there be parallel diversion ditches around the facilities, one for
run-on and one for run-off water? Will one or both of these ditches be lined? How will the water in
these ditches be influenced by the cone of depression? These questions are alluded to in the
discussion on page 4-27(second para), but are not explicitly addressed. I am sure engineers can and
have answered these questions for other mines with water balance analyses. It would be interesting to
see an explicit summary of the water balance for the various facilities. Such analyses would be good
for the example mine plan during operation and once the mine is no longer a net consumer of water
(page 5-44, para 2). Without the water balance analyses, potential impacts are not easily understood
or quantifiable.
EPA RESPONSE: A single diversion ditch intercepts up-gradient surface water and routes it
around the areas disturbed by mining, preventing it from mixing with waters that have
encountered site materials. The revised assessment includes a more detailed water balance
(Chapter 6).
Some ideas for how to manage and separate run-on and run-off water might help determine which
streams might dry up and what type of mitigation measures (i.e., lining ditches) could minimize the
impact. In addition, if run-on water can be maintained in a diversion ditch, what is the opportunity
for developing a reclamation plan for the ditches? Such plans might be able to minimize and partially
compensate for lost reaches of headwater streams.
EPA RESPONSE: The revised assessment does include some possible reclamation activities for
closure, although others could be proposed for an actual mining plan. Water would continue to be
diverted around areas where the water could encounter contaminants. Mitigation to compensate
for lost streams would be addressed through a regulatory process that is beyond the scope of this
assessment. Nevertheless, in response to public and peer comments we have included a discussion
of compensatory mitigation in Appendix J of the revised assessment.
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WHITNEY RESPONSE: See my response to Mitigation Measures.
EPA FINAL RESPONSE: Response is included under Mitigation Measures.
Protective approach. A "protective approach" is mentioned on page 5-30 (para 3, last sentence). This
has something to do with water management and would be good to explain.
EPA RESPONSE: This has been clarified in Chapter 7.
3.5 Charge Question 3
EPA assumed two potential modes for mining operations: a no-failure mode of operation
and a mode involving one or more types of failures. Is the no-failure mode of operation
adequately described? Are engineering and mitigation practices sufficiently detailed,
reasonable, and consistent? Are significant literature, reports, or data not referenced that
would be useful to refine these scenarios, and if so what are they?
David A. Atkins, M.S.
The no-failure scenario attempts to quantify the impacts from developing the footprint of the project
alone. In reality, various failures and accidents inevitably occur, and they may have a range of
impacts from inconsequential to large. So this scenario is presented to describe the minimum impact
that could be expected from project development assuming everything works as planned.
EPA RESPONSE: This comment is a correct interpretation of our "no-failure" scenario. Because
this distinction was not clear to many other readers, the revision no longer uses the term "no
failure". The no-failure scenario from the draft assessment has been changed to a chapter on the
effects of the footprint of a mining operation, without regard for operational problems (Chapter 7).
ATKINS RESPONSE: I concur with the modification to describing 'footprint' impacts.
EPA FINAL RESPONSE: No response required.
The mine will, by necessity, remove those streams and wetlands that are beneath the pit, waste rock,
tailings and processing plant development areas. There should be some flexibility in siting facilities
other than the pit or underground workings. For the 'no-failure' scenario, the Assessment presents
lengths of stream and areas of wetlands that would be lost due to physical displacement of the aquatic
resources from mine development and reduction in flows from mine water management. The
assessment presents the following resources that would be lost and that have been shown to be
spawning or rearing habitat for coho, Chinook, and sockeye salmon, or have resident populations of
rainbow trout and Dolly Varden:
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2 5-year scenario
78-year scenario
Eliminated or blocked streams (km)
87.5
141.4
Reduced flow (>20%; km)
2
10
Eliminated wetlands (km2)
10.2
17.3
Given the range of uncertainty with the proposed mine plan, presenting stream lengths and wetland
areas to the tenth place implies unrealistic accuracy. Significant figures should be checked and
consistent throughout the document, and ranges should be presented if known (e.g., results for the
pits could be presented with more accuracy since we know where they will be, whereas other
facilities that could be located in different areas should be presented with an appropriate range of
uncertainty).
EPA RESPONSE: The authors have carefully addressed this issue. Numbers from the literature
or from the PLPEBD retain the number of significant figures in the original. Numbers derived
for this assessment have the appropriate number of significant figures given the precision of the
input data and uncertainties due to modeling and extrapolation.
ATKINS RESPONSE: The discussion and modification adequately address the concern.
EPA FINAL RESPONSE: No response required.
The impacts as presented appear substantial, mainly because of the very large nature of the project.
However, it would be helpful to describe the significance of this loss, specifically with regard to the
following questions:
What impact would the loss to streams and wetlands have on the fishery within the Nushagak and
Kvichak basins?
EPA RESPONSE: Impacts of habitat loss and alteration are very difficult to quantify given the
lack of information on limiting factors, production and capacity estimates. We were unable to
comprehensively evaluate impacts at the population level, except for the most severe cases where
total losses of runs could be reasonably assumed.
ATKINS RESPONSE: This remains a significant gap in the assessment that will require
further data collection and interpretation.
EPA FINAL RESPONSE: We agree that, ifplanning for mines in the Bristol Bay watershed
proceeds, additional data collection and interpretation concerning salmonidpopulation biology
and response of salntonids in the watershed to disturbance, habitat loss, and toxicity would be
required.
Is this loss significant in comparison to the fishery as a whole?
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EPA RESPONSE: Losses of streams and wetlands under the mine footprint could not be related to
the fishery due to reasons listed above. For the TSFfailure scenario that completely eliminates or
blocks access to suitable habitat in the North Fork Koktuli River, we estimate that the entire
Koktuli portion of the run (-29% of Nushagak escapement) could be lost. Higher proportional
losses would occur if significant downstream effects occurred due to transport of toxic tailings
fines beyond the Koktuli as modeled under the Pebble 2.0 TSFfailure.
ATKINS RESPONSE: Same as above.
EPA FINAL RESPONSE: Same as previous response.
Are there local communities that could be affected by this specific loss?
EPA RESPONSE: Wildlife and resident fish communities would be affected by reductions in
spawning salmon. Local communities would also be affected by the reduction, which is now
discussed in Chapters 12 and 13 (e.g., Chapter 13 now contains tables which refer to specific
subsistence resources used by individual communities).
ATKINS RESPONSE: This discussion is adequate.
EPA FINAL RESPONSE: No response required.
Is fragmentation of the resource from this loss a significant impact (i.e., are there stocks that are
unique to the project area)?
EPA RESPONSE: Stock structure and genetic diversity are not well known at the project scale,
but based on evidence from other parts of Bristol Bay watersheds, local adaptation is highly likely.
Discussion of fragmentation effects is now included in Chapters 7 and 10.
ATKINS RESPONSE: This discussion is adequate.
EPA FINAL RESPONSE: No response required.
There is no discussion of engineering and mitigation practices in this section. The responsible
regulatory authority would require the project proponent to present a mitigation plan to compensate
for these impacts before permitting. Measures would include minimization of impact through facility
siting, reclamation if possible, and compensation if reclamation were not feasible. A thorough
analysis of possible mitigation approaches and the likelihood of their success are necessary to fully
evaluate impacts from the 'no-failure' scenario.
EPA RESPONSE: Mitigation measures for design and operation are more clearly called out in the
revised assessment. While measures chosen here may differ from what is required during the
regulatory process, the assessment is not a mining plan and not an evaluation of a mining plan.
The assessment assumes that measures chosen for the scenarios would be as effective as possible
and examines only accidental failures rather than a failure to choose a proper mitigation measure.
Mitigation to compensate for effects on aquatic resources that cannot be avoided or minimized by
mine design and operation would be addressed through a regulatory process that is beyond the
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scope of this assessment. Nevertheless, in response to public and peer comments we have included
a discussion of compensatory mitigation in Appendix J of the revised assessment.
ATKINS RESPONSE: This response highlights the fact that the assessment is not an
evaluation of a mining plan, but rather more general. As such, the new material is acceptable
and the revisions are appropriate for the intention of the document.
EPA FINAL RESPONSE: No response required.
Steve Buckley, M.S., CPG
The engineering and mitigation designs associated with the no-failure mode of operation are
inadequate. There is no detailed discussion of engineering practices. There is insufficient discussion
of any potential mitigation measures and there is a lack of any detailed research into applicable
engineering and mitigation methods. Appendix I provides some engineering and mitigation practices
along with water quality mitigation and monitoring during closure; however, these are not discussed
or accounted for in the main assessment document.
EPA RESPONSE: Mitigation measures, including wastewater treatment and closure and post-
closure monitoring and maintenance, were included as part of the mine scenarios in the draft
assessment, and this discussion has been expanded in the revised assessment. The mitigation
measures proposed within the mine scenarios are those that could reasonably be expected to be
proposed for a real mine (they are a subset of options presented in Appendix I), all of which were
presented as appropriate for the Pebble deposit in Ghaffari et al. (2011). Mitigation to compensate
for effects on aquatic resources that cannot be avoided or minimized by mine design and operation
would be addressed through a regulatory process that is beyond the scope of this assessment.
Nevertheless, in response to public and peer comments we have included a discussion of
compensatory mitigation in Appendix J of the revised assessment.
BUCKLEY RESPONSE: The reorganization and additional discussions presented in Appendix
J clarify when and where mitigation would become part of the regulatory process. The chapter
organization is much better than the first draft with respect to Failure/No Failure modes.
EPA FINAL RESPONSE: No response required.
Courtney Carothers, Ph.D.
The no-failure mode of operation appears to be described adequately. The engineering and mitigation
practices appear to be sufficiently detailed, reasonable, and consistent, although I have no particular
expertise with which to evaluate this part of the assessment.
EPA RESPONSE: No change suggested or required.
It would be helpful to have a clear statement about how well the local (geotechnical, hydrologic, and
environmental) conditions in this region have been studied and characterized. How much is
understood about the seasonal variation in these conditions and how those variations would affect
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these scenarios? How well are statistics from mines and TSFs constructed in very different
environments likely to apply here?
EPA RESPONSE: TSFfailure probabilities are based on Alaska's dam classification and
required safety factors applied to the method of Silva et al. (2008). The discussion offailure
probabilities is expanded to clarify this issue. Therefore, the failure is not a consequence of any
specific site conditions or seasonal phenomena. However, the discussion of local and regional
conditions has been expanded in the revised assessment. It is recognized that some issues such as
hydrology are very complex and additional information will be useful in future analysis of any
mine plans.
CAROTHERS RESPONSE: EPA responses are sufficient.
EPA FINAL RESPONSE: No response required.
Dennis D. Dauble, Ph.D.
The description of the no-failure mode for mine operation appears adequate in terms of potential
mitigation measures that might be employed. I have limited knowledge of current engineering
practices and subsequent risks to the environment from best practices of modern mines, including
those operating under optimal conditions. However, it would be helpful to include a short discussion
on which mitigation measures would be most applicable to mining activities in the Bristol Bay
watershed.
EPA RESPONSE: Standard design mitigation measures considered feasible, appropriate, and
'permittable' (as per Ghaffari et al. 2011) were considered and are discussed in Chapter 6 and
Appendix I of the revised assessment; these are standard measures common to other copper
porphyry mines. Evaluation of measures that would be proposed for an actual mine would occur
through the regulatory process. Whether these same measures would be appropriate for all
locations within the Bristol Bay watershed would depend on the given site's specific
characteristics.
DAUBLE RESPONSE: The topic of mitigation is adequately covered in Chapter 6 as well as
Appendices I and J of the revised assessment.
EPA FINAL RESPONSE: No response required.
Gordon H. Reeves, Ph.D.
No comments on this question.
Charles W. Slaughter, Ph.D.
Based on the actual history of other major resource extraction projects in Alaska and throughout the
world, a "no failure" assumption seems unrealistic. Rather, the assumption should be that there will
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be failures, of varying modes and magnitudes, over the life of the project. This reality is recognized
in several sections of text.
EPA RESPONSE: Our intention for the "no-failure" scenario was to identify and evaluate the
unavoidable environmental effects if all systems and mitigation measures operated perfectly, and
to separate those effects from a scenario where systems periodically failed. The "no failure"
chapter has been eliminated. The revised assessment differentiates between potential effects from
the footprint of a mine (Chapter 7), water treatment (Chapter 8), TSFfailures (Chapter 9), the
transportation corridor (Chapter 10), and pipeline failures (Chapter 11).
SLAUGHTER RESPONSE: The revision appropriately recognizes that in any human-
designed and engineered system there will be glitches or failures; I applaud the decision to
eliminate the no-failure scenario. The chapters cited do more adequately outline potential
consequences of those specific features (mine footprint, water treatment, and so on).
EPA FINAL RESPONSE: No response required.
In some sections in the Assessment, presumed "mitigation practices" are either cursory, optimistic, or
so general as to be un-supported. Examples include Section 4.3.7's cursory, generalized statements
about handling water: "Uncontrolled runoff would be eliminated... The mine operator would capture
and collect surface runoff and either direct it to a storage location... or reuse or release it after testing
and any necessary treatment"; "... water from these upstream reaches would be diverted around and
downstream of the mine where practicable"; "precipitation would be collected and stored..."; and
"Assuming no water collection and treatment failures, this excess captured water would be treated to
meet existing water quality standards and discharged to nearby streams, partially mitigating flow lost
from eliminated or blocked upstream reaches." Other examples from Chapter 6: "... assuming no
water collection and treatment failures" and "excess captured water would be treated... and
discharged to nearby streams..."
EPA RESPONSE: Water management (mitigation) measures are more clearly described and
discussed in the revised Section 6.1.2.5, and in sub-sections for the mine components in the
scenarios. However, the intent of the assessment is not to specify technologies, beyond those
already identified by the existing preliminary mining plans. Rather, the assessment focuses on the
environmental outcomes of conventional modern mining practices and effluents.
SLAUGHTER RESPONSE: The revised assessment does more clearly articulate possible
hydrologic (water management or "water balance") issues, as in Section 6.2.2.3, Section 7.3.2,
and Chapter 8. Given the relatively limited quantitative data available, the writers are to be
commended for their efforts. However, I must confess to a remaining impression of optimistic
generalities concerning some aspects of the water issues (perhaps inevitable because this is all
speculation on a possible project, rather than evaluation of a specific proposal). Examples: in
Section 6.2.2.3, "This released water may differ from natural stream water in chemistry and
temperature, but would comply with permitted discharge requirements. Water may be
reintroduced at locations, flow rates, or times of year that differ from baseline condition." And
in Section 6.2.2.4, "....This water would be expected to be relatively clean and, if properly
managed to control turbidity, could most likely be released without chemical treatment to
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maintain or augment streamflow." And Section 6.3.4, (Post-closure), assumptions about
monitoring runoff from NAG waste piles, establishment of constructed wetlands, and a
presumably adequate well field downstream of the TSF to monitor water quality.
EPA FINAL RESPONSE: We believe that we have addressed those issues adequately. The quoted
statements express an assumption of the routine operations scenarios that collected water would
be treated to permit limits before discharge and that those permit limits include both national
criteria and state standards. This statement refers to water from dewatering overburden. Such
water, if turbidity was controlled, is expected to resemble background surface water. We state that
it "could most likely be released without treatment" but if not, then treatment would be required
before discharge. Finally, these assumptions refer to post-closure conditions under permit. If, as
discussed elsewhere, the site was abandoned without meeting these assumptions, then negative
effects would occur.
John D. Stednick, Ph.D.
The no-failure mode is not adequately described. Assessment of the effects of the mine is based on
large risk failures of low probability and did not include low risk failures of higher probability. The
report concludes (and emphasizes) that the mine footprint will disrupt/disturb contributing watershed
and wetland areas and result in hydrologic modification. The hydrologic modification affects
salmonid habitats, particularly in low flow conditions. Regulatory oversight will include the State of
Alaska, and certainly mitigation measures would be required. The task is to address the adequacy of
these mitigation measures.
EPA RESPONSE: Our intention for the "no-failure" scenario was to identify and evaluate the
unavoidable environmental effects if all systems and mitigation measures operated perfectly, and
to separate those effects from a scenario where systems periodically failed. The revised assessment
no longer uses the term "no-failure", and does address effects from scenarios having higher
probability and lesser magnitude (e.g., failure to collect or treat leachate water) in addition to
those with louver probability and higher magnitude (e.g., TSFfailure). Mitigation to compensate
for effects on aquatic resources that cannot be avoided or minimized by mine design and operation
would be addressed through a regulatory process that is beyond the scope of this assessment.
Nevertheless, in response to public and peer comments we have included a discussion of
compensatory mitigation in Appendix J of the revised assessment.
Pollutant/toxicity assessment focused on copper. Other metals can be presented to show the range of
metal concentrations for chronic and acute toxicity. Suitability of treatment processes for all
wastewaters can be included to address potential effects on receiving waters.
EPA RESPONSE: Although copper is emphasized due to its dominance of the toxicity of
leachates, other metals were and are presented (Chapter 8).
The discussion of roads is mostly related to fish blockage and some soil erosion. Information on
current design standards was not included and tended to relay on dated references from logging
roads.
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EPA RESPONSE: The discussion of roads covers risks related to filling and alteration of
wetlands, stream crossings, fine sediments, dust deposition, runoff contaminants, and invasive
species. Information on current design standards is now included within text boxes throughout
Chapter 10, and relies on recent literature. The failure frequencies cited in the assessment are
from modern roads and not restricted to forest roads. One of the papers used for general
information (Furniss et al 1991) focuses on forest and rangeland roads, but it is a seminal
publication on the potential effects of roads, particularly as they relate to salmon.
There were no engineering or mitigation practices described in this section or in the document.
EPA RESPONSE: Mitigation measures, including wastewater treatment and closure and post-
closure monitoring and maintenance, were included in discussion of the mine scenarios in the
draft assessment as part of the design. This discussion has been expanded in the revised
assessment.
Roy A. Stein, Ph.D.
No Failure Operations and Their Impact. What about the failure of continued monitoring, of
continual inspection, of continual, rigorous oversight? This is more insidious than a catastrophic
failure of some sort, but perhaps just as dangerous (in fact, one research geochemist testified during
public testimony that of 150 hard-rock mines, none operated without leakage of leachate). How can
we be sure that mine operators will be held strictly accountable for their actions with regard to best
mining practices (a point emphasized by those who testified in favor of the Pebble Mine that indeed
best management practices would be used), meeting all the various and sundry regulations, and
communicating all of these activities back to the regulatory organization? Will there be a force of
will on the part of EPA or other regulatory body to be sure that all activities of the operator are
appropriate and within regulatory limits? The down-side of poor monitoring and lack of rigorous
oversight is the loss of salmonid populations. These losses are, in my view, less important than
compromising human health and life. Yet, at the Upper Big Branch Mine in West Virginia, dust
standards have been exceeded for years, leading to a dust explosion that killed 29 miners on April 5,
2010. In turn, even surviving miners were not immune to these dust impacts, for they suffer from
"black lung", a condition that literally shortens their life by decades. In turn, much of the monitoring
of these conditions has historically been the responsibility of the owner corporation, rather than an
independent regulatory body, much like "the fox guarding the chickens". Here at the Pebble Mine
site, where only fish (but, of course, Native Alaskan subsistence users, plus other human users as
well) are at stake, would one expect rigorous oversight by appropriate regulatory bodies? Skepticism
leads to cynicism when contemplating the Upper Big Branch Mine case history in the context of the
Pebble Mine proposal.
EPA RESPONSE: Our intention for the "no-failure" scenario was to identify and evaluate the
unavoidable environmental effects if all systems and mitigation measures operated perfectly, and
to separate those effects from a scenario where systems periodically failed The "no failure"
chapter has been eliminated The revised assessment differentiates between potential effects from
the footprint of a mine (Chapter 7), water treatment (Chapter 8), TSFfailures (Chapter 9), the
transportation corridor (Chapter 10), and pipeline failures (Chapter 11).
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Holding the mining company accountable is done through the regulatory process and is outside
scope of this assessment.
Engineering Practices and Mitigation. I did not think that mitigation was well described in text, but
Appendix I is quite well developed and was instructive to me as I moved through the documents. I
would suggest including the ideas in Appendix I in the mitigation section of the main report. Other
comments on mitigation issues can be found below associated with Question 12.
EPA RESPONSE: Mitigation measures for design and operation are included in the assessment
(Chapter 6), and are those that reasonably could be expected to be proposed for a real copper
porphyry mine (they are a subset of options presented in Appendix I). Many, if not all, of these
measures were presented as appropriate for the Pebble deposit in Ghaffari et al. (2011). Mitigation
to compensate for effects on aquatic resources that cannot be avoided or minimized by mine design
and operation would be addressed through a regulatory process that is beyond the scope of this
assessment. Nevertheless, in response to public and peer comments we have included a discussion
of compensatory mitigation in Appendix J of the revised assessment. Mitigation measures have
been explained more clearly throughout the revised assessment.
William A. Stubblefield, Ph.D.
It is interesting and appropriate that the EPA has included both modes of operation in conducting this
assessment. This approach provides some degree of "bounding" for the assessment; however, the
degree of accuracy (i.e., predictability) for either scenario cannot be known at this time. The
document appropriately acknowledges that there are a variety of potential mitigating factors (e.g.,
acts of God, accidents, market changes) that may render the assumptions used in this assessment
incorrect.
EPA RESPONSE: Our intention for the "no-failure" scenario was to identify and evaluate the
unavoidable environmental effects if all systems and mitigation measures operated perfectly, and
to separate those effects from a scenario where systems periodically failed. There were a number
of comments on this approach so the revised assessment no longer uses the term "no-failure" and
addresses effects from the foot print (i.e., the no failure scenario), failure scenarios having higher
probability and lesser magnitude (e.g., failure to collect or treat leachate water), andfailure
scenarios having lower probability and higher magnitude (e.g., TSF failure).
No change suggested or required.
STUBBLEFIELD RESPONSE: I agree with the new approach suggested by EPA.
EPA FINAL RESPONSE: No response required.
Dirk van Zyl, Ph.D., P.E.
The no-failure mode of operation failures is based on surface disturbances and potential blockages
caused by the various facilities. For example, for the mine pit, TSF and waste rock facility, the
surface areas of these facilities are used as a basis for calculating the streams and wetlands affected
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by the mining activities. While the failure mode is adequately described, engineering and mitigation
practices are not adequately described by EPA.
EPA RESPONSE: Mitigation measures associated with the mine components (e.g., waste rock
pile, TSF, etc.) were discussed in the sections presenting those components. They were not
repeated in the section on failures. These measures are included again in the revised assessment
(Chapters 4 and 6), but are described in greater detail. However, the emphasis of the assessment is
on the consequences offailures rather than on the details of how inadequate mitigation may cause
the failures.
The EPA Assessment states on p. 8-1 "Routine operations are defined as mine operations conducted
according to conventional practices, including common mitigation measures, and that meet
applicable criteria and standards". The adverse effects listed are: direct impacts as a result of removal
of streams in footprint of mine pit and waste storage areas; reduced streamflow resulting from water
retention; removal of wetlands in the footprint of the mine; indirect impacts of stream and wetland
removal; diminished habitat quality in streams below road crossings; and inhibition of salmonid
movement from culverts that may block or diminish use of full stream length.
EPA RESPONSE: No change suggested or required
Any mine in Bristol Bay will have to undergo a rigorous and lengthy regulatory review and
permitting process. I do not know of a process that will exclude consideration of the impact of all
mine facilities on the streams and wetlands in the region. Therefore, I would suggest that the full
implications of "mine operations conducted according to conventional practices, including common
mitigation measures, and that meet applicable criteria and standard" should have been addressed in
the report. The EPA (2003) document on Generic Ecological Assessment Endpoints for Ecological
Risk Assessment specifically details the applicability of Section 404 of the CWA in addressing
community and ecosystem-level endpoints. "The CWA provides authority for the Corps to require
permit application to avoid and minimize wetlands impacts and requires EPA to develop, in
coordination with the Corps, the criteria used for Section 404 decisions. When damages to wetlands
are unavoidable, the Corps can require permitees to provide compensatory mitigation". It is unclear
why this was not included in the evaluations.
EPA RESPONSE: This is not a permitting document. The purpose of the assessment is to evaluate
the effects of the operation of a mine on salmon ecosystems in the Bristol Bay watershed, while
following conventional practices, including common mitigation measures. Once those effects are
described, then it is appropriate to determine 1) if unacceptable environmental effects are likely to
occur and 2) whether those effects can be offset (made acceptable from a regulatory standpoint)
with compensatory mitigation. In other words, compensatory mitigation is a next step and not
within the scope of this assessment. Nevertheless, we have included a discussion of compensatory
mitigation in Appendix J in the revised assessment.
Similarly, one would expect that the regulatory reviews will require that the impacts resulting from
loss of streams, streamflow and road crossings will be addressed through engineering designs,
proposed mitigation measures, as well as regulatory and community engagement best mining
practices (see discussion above on "good" vs. "best" practices).
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EPA RESPONSE: Our scenarios included mitigation measures through engineering design and
operations to reflect standard industry practices. The purpose of the assessment was to evaluate
risks in the presence of these measures. The conmienter is correct that alternatives for such
measures would be evaluated during the permitting (regulatory) process. No change suggested or
required.
On p. 4-33, it is stated that "Environmental impacts associated with premature closure may be more
significant than those associated with planned closure, as mine facilities may not be at the end
condition anticipated in the closure plan and there may be uncertainty about future reopening of the
mine". Further text describes potential negative impacts from such a premature closure. One of the
outcomes of the regulatory review and permitting will be the establishment of financial assurance
that will provide State and Federal Regulatory Agencies with the financial resources to accommodate
a closure. These obligations are typically reviewed on a 3 or 5-year interval to also make sure that
they are adequate to cover premature closures. If the mining company is still managing the site, then
they will have responsibilities under all Federal and State Regulations and the dire picture painted by
the EPA Assessment should not come to pass.
EPA RESPONSE: The revision includes language that addresses financial assurance (Box 4-3).
Because of this major oversight of the realities when permitting and operating a mine it is essential
that the scenarios be reviewed by evaluating the effects that regulatory requirements and resulting
mitigation methods would have on the no-failure conditions before completely reworking the no-
failure mode of operations and their impacts. Other significant reports and data that should be
reviewed include typical permitting documents and resulting requirements for similar mines in the
US and Canada to obtain a range of potential outcomes. The results from such an evaluation will also
contribute significantly to the discussions in Alaska when the Pebble Mine and other mines in Bristol
Bay are brought forward to permitting.
EPA RESPONSE: Our intention for the "no-failure" scenario was to identify and evaluate the
unavoidable environmental effects if all systems and mitigation measures operated perfectly, and
to separate those effects from a scenario where systems periodically failed. The revised assessment
no longer uses the term "no-failurebut simply presents effects from scenarios having higher
probability and lesser magnitude (e.g., failure to collect or treat leachate water) as well as those
having lower probability and higher magnitude (e.g., TSF failure).
VAN ZYL RESPONSE: No further comments on Question 3.
EPA FINAL RESPONSE: No response required.
Phyllis K. Weber Scannell, Ph.D.
Chapter 4 provides a detailed description of a hypothetical mine design for a porphyry copper deposit
in the Bristol Bay watershed. Some of the assumptions appear to be somewhat inconsistent with
mines in Alaska. In particular, the descriptions of effects on stream flows from dewatering and water
use do not account for recycling process water, bypassing clean water around the project, or treating
and discharging collected water.
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EPA RESPONSE: The issues mentioned were discussed in Sections 4.2.3 (tailings storage) and
4.3.7 (water management) in the original draft document. They are now addressed in Chapter 6 of
the revised document, which describes the mine scenarios, and in Chapter 4, which provides
generic background on porphyry copper deposits and mining. Streantflow effects presented in
Chapter 7 now reflect a complete water balance, including water capture and re-use, bypass, and
discharge from the wastewater treatment facility, as suggested by the commenter.
WEBER SCANNELL RESPONSE: The reviewer is pleased that this additional information
has been added.
Chapter 4 of the revised Assessment contains an expanded description of the chemistry and
associated risks of porphyry Cu deposits (Section 4.2.2) and an expanded overview of the
mining process (Section 4.2.3). Chapter 6 of the revised Assessment presents descriptions of
potential mine development alternatives. The revised document has been reorganized to
provide in-depth descriptions of the plausible mine scenarios (Chapter 6). The descriptions of
the mine scenarios include expanded discussions of mining processes, ore processing, waste
rock management, tailings storage facilities, and water management. Chapter 6 of the revised
document provides an in-depth and needed background to the document. The reviewer also is
pleased that there is recognition of the possibility of activities extending in perpetuity (page 6-
16).
Much of the discussion of fish distribution has been moved to Chapter 7 of the revised
Assessment. This discussion has been revised and now includes more in-depth discussions
relating potential habitat loss and stressors to the mine scenarios.
The revisions to chapters 4, 6 and 7 satisfy the initial concerns raised by the reviewer.
EPA FINAL RESPONSE: No response required.
Section 4.3.8, Post-closure Site Management, raises critically important issues - can a mine in this
area be designed for closure? Is it acceptable to develop and operate a mine that will require
essentially perpetual treatment? It is my belief that these are the essential questions that should be
addressed during any mine permitting process.
EPA RESPONSE: We agree that these are important questions to be addressed, but they are risk
management, not risk assessment, questions. The purpose of the assessment is to evaluate risks to
the salmon fishery from large-scale mining. Risk management decisions will be made during the
permitting process. Thus, no changes to the assessment were made in response to this comment.
WEBER SCANNELL RESPONSE: The reviewer still believes that there is a potential risk to
the salmon fishery from large-scale disturbance of a mineralized area and that the sources of
risk may change over time as weathering of the exposed minerals occurs.
The reviewer notes some references to the possibility of perpetual treatment in the revised
document (e.g., page 6-16). I realize that the concerns raised in this comment are issues of risk
management; however, I believe it was necessary to suggest the possibility for long-term
management of the site.
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EPA FINAL RESPONSE: No response required.
Section 4.3.8.1 raises concerns about long term water quality and quantity from the mine pit. These
concerns need to be addressed during a mine permitting process. Pit water quality depends on how
the pit is developed, what reclamation will occur, if reclamation will be concurrent with mining, and
what kinds of water treatment will be used. Tailings storage facility (TSF) water quality depends on
how the mine tailings are managed; it may be possible to use dry stack tailings with sulfide removal
rather than submerged tailings.
EPA RESPONSE: We agree that water quality can be influenced by design and reclamation, but
when the latter entails creating a pit lake there is little flexibility for reclamation concurrent with
mining. How tailings are managed within the impoundment can affect water chemistry, and a dry
stack with sulfides removed may produce the best water quality results after reclamation if the fate
of the sulfide tailings is never considered. According to Ghaffari et al. (2011), 14% of the tailings
produced will be pyritic, which equates to an average of28,000 tpd in a 200,000 tpd mining
operation (over 255 million tons during a 25 year mine life). These tailings need to be managed in
such a manner that oxidation does not lead to acidic drainage, so the most effective way is to
deposit them subaqueously. Some suggested common mitigation measures for management of the
pit at and post closure are included in the revised assessment (Chapter 6).
WEBER SCANNELL RESPONSE: The reviewer is pleased that a discussion of the need for
mitigation and management of the pit at post closure has been included.
The discussion of the mine pit (Section 6.3.1) satisfies the concerns raised in the initial
comment.
EPA FINAL RESPONSE: No response required.
Paul Whitney, Ph.D.
Mitigation Plan. Most mine permit applications I have worked on include both mitigation to
minimize environmental impact and mitigation to compensate for environmental impact. The
assessment outlines a variety of mitigation measures to minimize impact, but no compensatory
mitigation. This is a concern, for I wonder if compensatory mitigation for the example mine is even
possible in the watersheds.
EPA RESPONSE: The purpose of the assessment is to evaluate the effects of the footprint and
operation of a mine that follows conventional practices, including common mitigation measures.
Once those effects are described, then it is appropriate to determine 1) if unacceptable
environmental effects are likely to occur and 2) whether those effects can be offset (made
acceptable) with compensatory mitigation. Determining compensatory mitigation is a next step and
outside the scope of this assessment; however, we have included a discussion of compensatory
mitigation in Appendix J in the revised assessment.
The watersheds are characterized with descriptors such as "pristine" (e.g., page 6-29, last para,
second line), "nearly pristine" (e.g., pages 2-25 and 7-2) and "exceptional quality" (page 2-20). It is
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also stated that the return of the salmon "fuel" (i.e., provide energy to) the terrestrial food web. If in
fact the watersheds are pristine or nearly pristine, the habitat is high quality and there is little, if any,
opportunity for compensatory mitigation (i.e., improving low quality habitat) in the terrestrial and
fresh water environments. For example, if 55 miles of streams and streamside wetlands are lost to the
mine footprint (page ES 15, first bullet), is it possible to find miles of very degraded stream to plan
for and implement compensatory mitigation? If one assumes a mitigation ratio of 3:1 for
enhancement, one might have to find 165 miles of degraded stream for compensation. I suspect (but
don't know) that there are very few (if any) miles of degraded stream where compensatory mitigation
could occur in the Bristol Bay watershed(s). If this is the case, it might not be possible to demonstrate
no net loss for waters of the US, and this is something EPA should be interested in.
EPA RESPONSE: The comment is correct in stating that the exceptional quality of the Bristol
Bay environment leaves little opportunity for compensatory mitigation. Determining compensatory
mitigation is outside the scope of this assessment; however, we have included a discussion of
compensatory mitigation in Appendix J in the revised assessment.
I agree that the ecological resources can be ranked as having high quality because the human
footprint on the habitat is small (i.e., few roads and villages), but from an energetics (i.e., fuel) and
food web perspective, the pristine characterization may not be accurate. The commercial catch of
approximately 27.5 million fish each year (up to 70% of the total number of sockeye produced) is a
lot of calories that are not flowing through the ecological foodwebs of the watersheds. Granted, some
of the commercial catch (if not caught) might not enter the watersheds, but some and perhaps a lot
would, especially in good run years. While the harvest level might be sustainable, the loss of energy
to commercial fishing causes pause to characterize the watersheds as pristine or nearly pristine. The
potential impact of fisheries on energy flow has been addressed by Pauly et al. (2000) and Libralato
et al. (2008). I wonder if it is technically possible that a reduction in the commercial fishery is a
compensatory mitigation measure.
EPA RESPONSE: Compensatory mitigation requirements address the needfor project proponents
to replace aquatic resources and ecosystem functions that their project has impacted. Reduced
fishing harvests would not replace lost spawning and rearing habitat. Further, it would remove the
burden of compensation from the party that caused the damage. Determining compensatory
mitigation is outside the scope of this assessment; however, we have included a discussion of
compensatory mitigation in Appendix J in the revised assessment.
WHITNEY RESPONSE: Pointing out that reducing commercial harvest would not replace lost
spawning and rearing habitat is very good and I appreciate the insight. None-the-less EPA
seems to have a hard time acknowledging much less discussing the negative impact commercial
fishing has on ecosystem energetics and nutrient cycling. Acknowledging these past, current
and future impacts would greatly improve the Cumulative Impact part of the EPA assessment.
EPA FINAL RESPONSE: Text has been added to Chapter 5 and Chapter 7 that provides further
detail regarding marine-derived nutrient dynamics and acknowledges that escapement increases
would lead to higher marine-derived nutrient inputs to these systems (although this may not
translate into increased salmon production, particularly where other factors are limiting).
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However, the assessment is not a cumulative impact analysis that considers the relative effects of
all sources of human intervention in the region. Its purpose is to assess potential effects of one
activity—large-scale mining. Thus, the effects of commercial fishing are outside the scope of the
assessment.
Effluent treatment. Water quality information in the assessment for benchmarks, background, and
leachate is extensive. A thorough review of the water quality and toxicity information is beyond the
scope of work of this review. After several reads of this information, it appears that the work is good
for copper. For example, work on salmonid olfaction and copper conducted by McCarthy et al.
(2007) is potentially important and is cited. The inhibiting effects of copper on olfactory receptor
neurons cited by McCarthy et al. (2007) at or above 2 jag/L are lower than the Alaska hardness-based
standards and the biotic ligand model (BLM) standard in Table 5-14, but are above the biotic ligand
model standard in Tables 5-15 and 5-16.1 assume this is due to differences in binding of copper by
dissolved organics but I am not sure. Whether one decides to use the 2 jag/L benchmark, or the even
lower BLM benchmarks that are in some cases below background values in Table 5-19,1 think the
key question is whether proposed leachate processing can cost-effectively achieve benchmarks that
hover around background concentrations. The answer is beyond my level of expertise.
EPA RESPONSE: BLM-derived copper criteria are derived for the different leachates. The values
depend on the co-occurring ions, which differ considerably among leachates and, in the case of
ambient waters, on dissolved organic matter. The low copper benchmarks would be achievable
with treatment by reverse osmosis, which has been used at other mines. Whether it is economically
feasible to achieve benchmarks close to background concentrations is outside the scope of the
assessment. No change suggested or required.
I do not agree with the assessment's critical question - whether or not effects are observed at these
low levels (page 5-57, Exposure-Response Data from Analogous Sites, second sentence). If effects
are observed at background concentrations, it seems unreasonable to ask for an even lower
benchmark than background concentrations. The uncertainties assessment at the bottom of page 5-57
also seems unreasonable. The possibility that background concentrations are not protective in
particular cases seems highly unlikely for one of the most productive salmon communities in the
world.
EPA RESPONSE: The passages cited by the reviewer refer to the possibility of effects at copper
concentrations below criteria, not below background. Similarly, the studies mentioned found
effects below criteria levels but above background concentrations.
WHITNEY RESPONSE: This isn't the way I read Table 5-19 - please recheck.
EPA FINAL RESPONSE: This response refers to a table in the 2012 draft that lists copper
criteria derived using the biotic ligand model and site water chemistries. As discussed in both
drafts, water in some upper tributaries of the South Fork Koktuli River exceeds those criteria.
Those concentrations are local background concentrations for streams draining the ore body, but
not regional or watershed background concentrations. That is a different issue from the discussion
of Exposure-Response Data from Analogous Sites (p. 5-57 of the 2012 draft), which addresses
studies that find apparent effects at copper concentrations below criteria.
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I can think of many questions that are more critical than looking for effects on salmonids at
background or near background concentrations of copper. For example, it might be more important
to ask what concentrations of copper will result in a significant impact on the salmonid populations
and to ask what impact a mixing zone would have on salmonid populations. Last but not least, what
are the potential impacts of all toxics on the many other non-salmonid species?
EPA RESPONSE: See response to previous comment regarding background concentrations
versus water quality criteria. Because water quality is so high at the site, the threshold for copper
toxicity is low based on the biotic ligand model. Effects on salmonid populations from exceeding
toxic thresholds cannot be estimated because the available monitoring data do not characterize
salmonid demographics or productivity in the streams draining the site. However, the analysis has
been expanded to include estimates of kilometers of stream habitat that would be exposed to
copper levels sufficient to cause aversion, sensory deprivation, decreased reproduction, or kills.
Mixing zones are not allowed by the State ofAlaska for water quality compliance in anadromous
streams, and the available stream data are not sufficient for mixing zone modeling. However, a
discussion of mixing zones, including the amount of mixing that would be required to reach
nontoxic levels, has been added. Non-salmonid fish are not included as endpoint species. However,
because copper and most other metals are most toxic to arthropods, the assessment implicitly
addresses non-salmonid fish (which depend on arthropods in the food web) as well.
3.6 Charge Question 4
Are the potential risks to salmonidfish due to habitat loss and modification and changes
in hydrology and water quality appropriately characterized and describedfor the no-
failure mode of operation? Does the assessment appropriately describe the scale and
extent of risks to salmonidfish due to operation of a transportation corridor under the no-
failure mode of operation?
David A. Atkins, M.S.
For the no-failure mode of mine operation, the risks to salmonid fish due to habitat loss and
modification in the vicinity of the project are described in terms of loss of lengths of stream or areas
of wetlands. Project proponents state that the mine will only impact a very small fraction of the
watershed (under a no-failure scenario). It is important to establish whether the modeled impact (e.g.,
the loss of 87.5 km of streams) is significant, both in terms of the absolute impact, as well as the
effect on ecosystem fragmentation.
EPA RESPONSE: Footprint effects on habitat loss are now characterized in relation to the
distribution of habitat conditions throughout the larger watersheds. Fragmentation effects are not
anticipated at the mine site, apart from blockage of headwater streams as described, but are
anticipated in the case of the transportation corridor (Chapter 10) and TSFfailure (Chapter 9).
ATKINS RESPONSE: This response is adequate.
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EPA FINAL RESPONSE: No response required.
In addition, project proponents often state they will preserve and even improve the fishery. As
mentioned in the answer to the previous question, it would be helpful to know what kinds of
mitigation efforts could be employed - minimization, reclamation and compensation - and have
some assessment of the potential effectiveness.
EPA RESPONSE: Mitigation measures, including wastewater treatment and closure and post-
closure monitoring and maintenance, were included in discussion of the mine scenarios in the
draft assessment, and this discussion has been expanded in the revised assessment. The mitigation
measures proposed within the mine scenarios are those that could reasonably be expected to be
proposed for a real mine (they are a subset of options presented in Appendix I), all of which were
presented as appropriate for the Pebble deposit in Ghaffari et al. (2011). Reclamation is not
mitigation, but the revised assessment also includes some suggested measures to be used in
closure/post-closure to reclaim the disturbed areas. Mitigation to compensate for effects on aquatic
resources that cannot be avoided or minimized by mine design and operation would be addressed
through a regulatory process that is beyond the scope of this assessment. Nevertheless, in response
to public and peer comments we have included a discussion of compensatory mitigation in
Appendix J of the revised assessment.
ATKINS RESPONSE: This response is appropriate and highlights the strengths of the
regulatory process that would assess compensation for effects that cannot be avoided or
minimized. The expanded discussion of mitigation is appropriate for the context of the
assessment. It does not address whether mitigation could improve the fishery.
EPA FINAL RESPONSE: Issues of whether mitigation could improve the fishery are now
addressed in Appendix J.
The Assessment determines that construction of the transportation corridor could alter the habitat,
chemistry, and the migration path across the corridor for the over 30 streams that the corridor will
cross or come near. The report further states that the corridor could affect 270 km of streams below
the corridor and 240 km of streams above, but that there is no way to assess the magnitude.
Therefore, the impacts of the corridor on fish populations are unknown, and this impact is not
described in a way that can allow a reviewer to draw any conclusion.
EPA RESPONSE: The revised assessment states that "the exact magnitudes of changes in fish
productivity, abundance and diversity cannot be estimated at this time," but summarizes the
species, abundances, and distributions that would potentially be affected. Also, the assessment
concludes that, assuming typical maintenance practices after mine operations, approximately 15 of
32 culverted streams with restricted upstream habitat would be entirely or in part blocked at any
time. As a result, salmonidpassage—and ultimately production—would be reduced in these
streams, and they would likely not be able to support long-term populations of resident species
such as rainbow trout or Dolly Varden.
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ATKINS RESPONSE: This response is appropriate. I am not an expert in culvert design and
maintenance, so have no basis to evaluate the appropriateness of the estimate of the number of
culverts that could be blocked at any time after mine operations cease.
EPA FINAL RESPONSE: No response required.
Further, the references for road design and construction practices seem to be more representative of
forest and rangeland roads than the type of road that would likely be constructed for this type of
project. It would be helpful to cite experience from other transportation corridors constructed for
mining and oil and gas projects and developed recently in Alaska.
EPA RESPONSE: Because the proposed mining would take place in an undeveloped area, the
literature is necessarily from areas outside of Bristol Bay. Further, we found no data concerning
the performance of culverts for mining or oil and gas projects in the region. However, to the extent
possible we used examples from representative environments. The failure frequencies cited in the
assessment are not restricted to forest roads. One of the papers used for general information
(Furniss et al. 1991) focuses on forest and rangeland roads, but it is a seminal publication on the
potential effects of roads, particularly as they relate to salmon. The general conclusions of that
paper should be applicable to the transportation corridor considered in the assessment.
Information on current design standards is now included within throughout Chapter 10, and relies
on recent literature.
ATKINS RESPONSE: The revised section is appropriate for the scope of the assessment.
Other designs may be implemented that could result in more favorable performance, but the
specific designs would have to be reviewed in detail and appropriate existing analogs would
have to be selected for performance evaluation.
EPA FINAL RESPONSE: No response required.
Steve Buckley, M.S., CPG
Risks to fish due to habitat loss and modification and changes in hydrology and water quality are
overly simplified given the broad parameters used to model these potential risks. More specific
details on the water balance would help define potential risks to fish from dewatering and habitat
loss. For example, there is no attempt to identify groundwater flow paths or the specific response of
various landforms to seasonal changes in precipitation and runoff, yet 34 pages are dedicated to an
attempt to quantify these impacts. More detailed information is needed to accurately quantify the
changes in anticipated runoff and infiltration in the proposed area to determine potential impacts to
hydrology and water quality.
EPA RESPONSE: A revised and much more detailed water balance and streamflow analysis is
now incorporated in the assessment (Chapters 6 and 7). The revised draft also includes estimates
of the specific changes in flow at individual gages. The commenter is correct that the assessment
does not specifically address the potential changes in landforms or, for that matter, to vegetation in
the land areas such as the drawdown zone which would be among the areas most affected by the
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mine development. We consider that any such changes would have only a secondary impact on
salmon relative to the impacts that the assessment does address.
BUCKLEY RESPONSE: The additional information presented in Chapter 3 on stream
characterization along with the information in Figure 7.14 on groundwater and fish habitat are
major improvements to the document.
EPA FINAL RESPONSE: We agree that Figure 7-14 provided useful information on
groundwater and fish habitat, but we have removed it from the final assessment. Figure 7-14 came
from a report (Wobus et al. 2012) that was coauthored by Dr. Ann Maest, which had been peer
reviewed for EPA by an independent review panel. Although the peer review supported the use of
the information in Wobus et al. (2012), we have withdrawn this information and citations of
Wobus et al. (2012) because accusations of fraud in another matter against Dr. Maest led to
questions concerning the potential for fraud in Wobus et al. (2012). This report was used only to
support our analyses, and its removal has not changed the assessment's findings.
Additional ecological information on the contributing watershed area for each fish bearing stream
crossing would help identify the potential impacts to fish due to the construction and operation of a
transportation corridor.
EPA RESPONSE: Additional information on watershed attributes (discharge, channel gradient,
floodplain potential) of streams crossed by the transportation corridor, and their importance to
salmonids, is now included in the analysis presented in Chapter 10.
BUCKLEY RESPONSE: This information is a critical addition to the revised assessment.
EPA FINAL RESPONSE: No response required.
Courtney Carothers, Ph.D.
Six key direct and indirect mechanisms are identified to pose potential risk to salmonid fish species:
eliminated or blocked streams (87.5-141.4 km), reduced stream flow, removal of wetlands (10.2-17.3
km), indirect effects of stream and wetlands removal (downstream effects likely diminishing fish
production), diminished habitat quality downstream of road crossings, and blocked movement of
salmonids at road crossings. These mechanisms are described clearly. The report appears to
appropriately describe the scale and extent of risks under a no-failure mode of operation, although I
have no particular expertise with which to evaluate this assessment.
EPA RESPONSE: No change suggested or required.
CAROTHERS RESPONSE: EPA responses are sufficient.
EPA FINAL RESPONSE: No response required.
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Dennis D. Dauble, Ph.D.
The assessment describes the number of stream miles impacted under each mode of operation,
including miles blocked and eliminated. Less specific were descriptions of impacts due to
sedimentation and leachates. What is lacking is quantitative estimates of spawning and rearing
habitat that would be lost relative to the total habitat available. Having this information would help
provide perspective of overall risk to individual watersheds and the Bristol Bay watershed as a
whole. Risks to salmonid fish due to changes in water quality (i.e., toxic materials) need to consider
differences in sensitivity and behavioral response according to salmonid life stage.
EPA RESPONSE: Stream habitat losses are now characterized in relation to the distribution of
habitat conditions throughout the larger watersheds (Chapters 3 and 7). The assessment of risks
from aqueous toxicity distinguishes overt toxic effects on early life stages from behavioral effects
on adults.
DAUBLE RESPONSE: Stream habitat losses and toxicity are well-described in terms of life
stage and species for each of the identified risk areas described in Chapters 7 through 11. One
problem is that many tables (e.g., 8.4-8.8) lack narrative text. These tables are somewhat
complicated and not self-explanatory and should not be introduced to the reader as a citation
without supporting narrative text. For example, what are quotients? Does a low quotient value
relative to the CMC or CC indicative of no risk? Not until Box 8.3 (or 20 pages after tables 8-4
to 8-8 is an explanation provided so that readers might know what the data in these tables
means. Strongly suggest that Box 8.3 be moved forward in this chapter and that narrative text
be added to the document.
EPA FINAL RESPONSE: A paragraph has been added to the end of Section 8.1.1 explaining the
quotients and their interpretation. Box 8-3 was not moved up because it addresses the
interpretation of quotients in the context of risk estimation rather than contaminant screening.
Surface water characteristics of site watersheds within the area of probable impact are detailed in
Table 5-17, but not so for other streams and lakes in the broader watershed. More information should
be presented where available. It is not clear whether potentially affected streams and lakes might be
nutrient limited (seems that they might be given their dependence on MDN). For example, include N
or P concentrations and some discussion about primary and secondary productivity.
EPA RESPONSE: We recognize that nutrient status, and more importantly prey availability, is a
critical component of habitat capacity for fish in these systems, and may be strongly driven by
salmon-derived nutrients. We concur that more information is needed regarding potential limiting
factors for salmon productivity and capacity, and that food availability may be one such factor.
However, because water chemistry data may not provide a complete picture of trophic status,
particularly where direct consumption of salmon flesh, eggs, and fry is of such high importance,
and because nutrient status is a water quality or habitat parameter not directly influenced by
mining operations as outlined in our conceptual models (e.g., Figure 7-1), we determined that
nutrient status of area streams is outside the scope of this assessment.
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DAUBLE RESPONSE: The amount of additional detail in Chapter 8 on stream hydrology is
impressive and useful for this reviewer. While nutrient status of the watershed relative to
mining impacts may be outside the scope of the assessment, this information should be included
as part of the characterization process.
EPA FINAL RESPONSE: Discussion of marine-derived nutrients has been expanded in the final
assessment (Section 5.2.5, Box 5-3).
I found risks to salmonid fish due to operation of the transportation corridor well-described with
respect to spatial distribution of fish and their habitats.
EPA RESPONSE: No changes suggested or required.
DAUBLE RESPONSE: No comment.
EPA FINAL RESPONSE: No response required.
Gordon H. Reeves, Ph.D.
The potential risks to the freshwater habitat of anadromous salmonids are appropriately characterized
and described for the no-failure mode of operation. The report considered the primary potential
impacts of mine development and operation that could impact habitat and quantified the impacts
where possible. The analyses seemed sound and logical, given the acknowledged limitations about
the actual mine location and operation.
EPA RESPONSE: No change suggested or required.
One possible factor that could influence the results was the use of the USGS 1:63,360 maps for
developing the stream network. These maps generally underrepresent the amount of small streams,
which can be ecologically important contributors to the overall productivity of the freshwater habitat
of anadromous salmonids. This is acknowledged in the limitations (p. 5-46). Thus, the potential loss
and modification of habitat that the report describes could be considered minimal at this time. It
would be prudent to confirm the accuracy of the stream layer developed from the 1:63,360 maps in
any future analysis.
EPA RESPONSE: We agree with this comment. No change to the assessment suggested or
required.
The potential impact of the mine development and operation on the productive capacity of the
various river systems could be developed more fully to gain better insights into potential impacts of
the mine. The authors considered the amount of habitat that could potentially be impacted by mine
development and operation by estimating the stream length that would be impacted and by
considering the percent of spawners of the various species (from ADF&G surveys) observed in
potentially impacted areas. However, the productive capacity of given stream reaches for a given fish
species can vary widely. Any additional analysis could consider using Intrinsic Potential (IP)
(Burnett et al. 2007. Ecological Applications 17:66-80), which considers local geomorphic features
to estimate the potential of a given stream reach to provide high quality habitat for a given species.
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The concept, developed for use in the Pacific Northwest (PNW), has been applied successfully for
Chinook salmon in the upper Copper River (A. Bidlack, EcoTrust, Cordova, AK, unpublished). The
IP model for Chinook salmon from the PNW that was used in the Copper River was modified after
discussion with local biologists. Similar modification may be needed for the PNW IP model for coho
salmon to be used in Bristol Bay.
EPA RESPONSE: We now include a characterization of stream channel gradient, watershed
terrain (% jlatland in lowland), and mean annual stream/low for all streams in the two
watersheds. We are unable to build a complete IP model, as this would require validation and
more elaborate construction of metrics appropriate to this region, but our preliminary
characterization provides the building blocks for assessing the distribution of key habitat-forming
and constraining features across these watersheds.
Another factor that I believe merits further consideration is the potential impact of altered thermal
regimes of discharge water from treatment facilities (p. 5-28). Warmer water could have potential
ecological impacts, particular during the time when eggs are in the gravel. Eggs could develop more
quickly and fry could emerge earlier as a result of even minor changes in water temperatures (see:
McCullough, D.A. 1999. A review and synthesis of effects of alterations to water temperature regime
on freshwater life stages of salmonids, with special reference to Chinook salmon. US Environmental
Protection Agency, Seattle, EPA 910-R-99-010. 279 p.; and McCullough, D.A., J.M. Bartholow, H.I.
Jager, and 11 co-authors. 2009. Research in thermal biology: burning questions for coldwater stream
fishes. Reviews in Fisheries Science 17: 90-113.). These changes could be significant ecologically.
EPA RESPONSE: This is now addressed in Chapter 8.
The report noted in several places that the potential impact on groundwater flows was not understood
at this time but that disruptions of flow paths could have critical impacts on aquatic resources. One
impact that was not mentioned is the loss of over-wintering habitat. K.M. Burnett (U.S.D.A. Forest
Service, PNW Research Station, Corvallis, OR, draft report) found that the major overwintering areas
for coho salmon in the Nome River, AK were at points of groundwater inputs. The groundwater
influx created areas that were less likely to freeze during winter.
EPA RESPONSE: Overwintering effects from thermal changes are now described in Chapter 7.
Charles W. Slaughter, Ph.D.
Yes, the risks to salmonids are well characterized with regard to the hypothetical mine operation
itself. However, I suggest that the concept of "no failure," if taken as applying to the entire operation
from inception through operation, is not realistic.
EPA RESPONSE: The "no failure" scenario was not meant to represent a realistic scenario.
Rather, it was meant to illuminate the effects that would occur solely from a mine footprint, even
in the absence of accidents or failure. The revised assessment no longer uses the term "no-
failure", but simply presents effects from scenarios having higher probability and lesser
magnitude (e.g., failure to collect or treat leachate water) and those having lower probability and
higher magnitude (e.g., TSFfailure).
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SLAUGHTER RESPONSE: OK.
EPA FINAL RESPONSE: No response required.
The Assessment makes a fair start toward considering the risks to salmonids from the potential
transportation corridor. However, the many issues regarding stream and wetlands directly or
indirectly affected by roads and pipelines are not fully explored. The extent (length, area) of streams
and wetlands affected, as outlined in the text, should be considered a very optimistic lower estimate.
The specific issues mentioned, such as bridge or road maintenance, culvert blockage or failure,
erosion from cuts, fills, and the roadway itself, are all significant. I simply suggest that the potential
consequences of imposition of the (hypothetical) transportation corridor, and future expansions
consequent to ancillary infrastructure development and further additional resource extraction
projects, would be broader, more severe and of more consequence (and thus should receive more
emphasis) than the Assessment indicates. I suggest more fully incorporating Frissell and Shaftel's
Appendix G into the body of the Assessment.
EPA RESPONSE: The revised assessment notes that the characterization of both stream length
and wetland area affected likely represents a conservative estimate of the potential effects of the
transportation corridor on hydrologic features of this area. The cumulative risk section (Chapter
13) has been expanded to include the transportation corridor, ancillary mining development and
secondary development. Additional information from Appendix G is incorporated into the main
text, and the appendix is referenced in a number of places.
SLAUGHTER RESPONSE: Acknowledgement of the conservative (low) estimate of wetland
and stream impacts is appropriate. Chapter 13 is a good addition to the Assessment. As noted
previously, the transportation corridor and "ancillary" or "induced" development activities
are, over the long term, as problematic for the Bristol Bay watershed and region as is the initial
PLP (proposed) mine.
EPA FINAL RESPONSE: No response required.
John D. Stednick, Ph.D.
To address this question, a water balance needs to be developed for the study area watersheds.
Develop a water balance that includes all the principal components and how they may vary in time
and space. The site characterization needs significant improvement, particularly as related to
hydrologic inventories and processes. Little to no data are presented on temperature, precipitation,
evaporation, frozen soils, soil moisture storage, and groundwater storage and movements. The data
that are presented often have unreasonable significant figures. The linkage between surface and
groundwater needs to be better demonstrated. Hyporheic exchanges are recognized as being
important, but the assessment does not demonstrate this linkage.
EPA RESPONSE: A complete annual water balance with patterns of temporal variability has been
developed and incorporated into the revised assessment. Detailed temporal variability is beyond the
scope of the assessment. The significant figures of reported data and analysis results have been
reduced to a reasonable number. Detailed data presentations on temperature, precipitation,
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evaporation, frozen soils, soil moisture storage, and groundwater storage and movements are
generally not reported. We cite sources of information, and data are cited and reported as needed
for assumptions of analyses conducted for the assessment. Additional information on surface
water-groundwater interactions has been added.
Iliamna Lake hydrology needs to be characterized. What are the inflows, outflows, and turnover
rates? What is the existing water quality in the lake? Aquatic life should be characterized as well.
What is the risk of pollutants entering the lake from the road corridor or upstream mine development
operations?
EPA RESPONSE: The overall hydrology of the lake was not included because none of the
scenarios would result in a change in the hydrology or water quality of the lake as a whole.
Rather, any effects in the lake would be limited to the vicinity of outflows from the affected
streams. Risks from contamination of tributaries to Iliamna Lake are discussed in Chapters 8,10,
and 11 of the revised assessment.
Climate variability is recognized as a game changer. What are the potential future scenarios for
temperature and precipitation changes in southwest Alaska, and how will these scenarios affect the
water balance? How will climate change affect the availability of water for mine operations,
including processing and potable uses?
EPA RESPONSE: Climate change projections and potential impacts are now discussed in Chapter
3.
Similarly, a complete water quality characterization is lacking. What is the water quality in surface
waters, groundwaters, in time, and in space? What is the definition of background water quality?
Numerous exploratory activities have taken place in the watershed and have the potential to affect
water resources. How were these separated or addressed? Given the geologic and geomorphologic
settings for the study area, are we comfortable that the watershed ridges delineate the watershed
area? Groundwater movements may ignore the physical watershed area boundary and follow
groundwater gradients. Streamflow measurements from the gauged watersheds could be useful in
answering this question. Similarly, the linkage of groundwater and hyporheic exchange needs to be
better demonstrated. Do these exchanges occur in all stream segments and gradients? What effect
does the groundwater have on stream temperatures? Are depth to groundwater readings available? Is
a groundwater monitoring program in place?
EPA RESPONSE: The water quality described as background by the PLP in their Environmental
Baseline Document was accepted as such in the assessment. Water quality in the three streams
that drain the site was presented in Table 5-17 (now Table 3-4). The assessment now includes
information on estimated groundwater interaction strength across the project area streams
(Figure 7-14).
EPA FINAL RESPONSE: We agree that Figure 7-14 provided useful information on
groundwater and fish habitat, but we have removed it from the final assessment. Figure 7-14 came
from a report (Wobus et al. 2012) that was coauthored by Dr. Ann Maest, which had been peer
reviewed for EPA by an independent review panel. Although the peer review supported the use of
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the information in Wobus et al. (2012), we have withdrawn this information and citations of
Wobus et al (2012) because accusations of fraud in another matter against Dr. Maest led to
questions concerning the potential for fraud in Wobus et al. (2012). This report was used only to
support our analyses, and its removal has not changed the assessment's findings.
The tables and hydrographs (pages 5-32 to 5-39) are unclear. What streamflow changes are
associated with what salmon species and life stage? A boundary condition for adults is different than
for fry.
EPA RESPONSE: Maps of species distributions in relation to affected stream segments are now
included in Chapter 7. The environmental flow analyses are not species or life stage specific, but
assume an overall risk associated with proportional deviations from the baseline flow regime.
The proposed mine will use large quantities of water in ore processing and transport. How much is
required and how will this affect water resources; both surface and groundwater?
EPA RESPONSE: The water balance has been extensively revised (Chapters 6 and 7), and
updated estimates are incorporated into the streamflow analyses provided in Chapter 7. Effects on
groundwater resources are explicitly incorporated in the analysis of the pit dewatering, associated
cone of depression, leachate leakage from the TSF and the waste rock piles, and interbasin
groundwater transfers.
The no-failure mode of operation is predicted to change the watershed contributing area and hence
streamflow, and uses the boundary condition of a 20% change in streamflow as significant salmonid
habitat loss. The assessment assumes a liner response between watershed area and streamflow
contribution, and a linear response between habitat productivity and watershed area.
EPA RESPONSE: A more comprehensive water balance is now used to estimate streamflows,
which incorporates losses and additions due to pit dewatering, and wastewater treatment plant
processing and distribution, such that the relationship of watershed area and streamflow is not
linear. We do not assume a linear response between habitat productivity and watershed area.
Upland settings are probably more productive in terms of productivity and should be addressed as
such.
EPA RESPONSE: Relative productivity of aquatic habitats has not been extensively documented
across the region.
Toxin assessment focused on copper, and other metals can be presented to show the range of metal
concentrations for chronic and acute toxicity, i.e., arsenic, molybdenum, silver, barium, and lead.
Given the very clean waters (low hardness and organic carbon), the chronic toxicity of various metals
should be evaluated. Water quality varies in time and space in the study area, and a better
characterization of water quality could be developed. Metal loads could be calculated with
streamflow records. What is the proportioning of dissolved versus total metals? Are metals
transported with sediments? Do organic carbon fluxes change in space or time?
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EPA RESPONSE: The influence of receiving water chemistry was incorporated to the extent that
current science allows. The toxicity of copper was corrected for water chemistry using the biotic
ligand model, and the toxicity of other metals was corrected for hardness, when models were
available. In each case, water chemistry of the individual receiving stream was used for the
correction. Also, instream concentrations are based on streamflows, including changes in
streamflows due to mine operations. Both sediment and organic matter concentrations are quite
low in all three streams at the Pebble site, so copper remains dissolved in the model and other
metals in leachates are likely to remain dissolved as well.
Salmonid risk from travel corridor: The proposed road location has the potential to affect 270 km of
stream between stream crossings and Lake Iliamna. The expected road erosion and sediment
production has known effects on salmonid resources. The discussion of the travel corridor does not
include the potential for road failures, landslides, blocked culverts, or ditch failure. The discussion
does not talk about traffic volume or the potential of hazardous material transport on the travel
corridor. Need to address road maintenance, fugitive road dust, and road chemicals either dust or ice
control.
EPA RESPONSE: The original draft assessment included discussion of the potential for road and
slope failures, blocked culverts, and soil erosion from road cuts, borrow areas, road surfaces,
shoulders, cut-and-fill surfaces, and drainage ditches. The revised assessment factors traffic
estimates into assessments of chemical spills from transport truck accidents (Section 10.3.3) and
impacts from dust (Section 10.3.5). Salts used for to reduce dust and improve winter traction are
discussed in Section 10.3.3. Potential mitigation measures for stormwater runoff, erosion, and
sedimentation are discussed in Box 10-3.
There is no discussion of water processing after delivery of the slurry to the sea port and return of
waters back to the mine site.
EPA RESPONSE: Section 6.1.2.5 of the revised assessment discusses that the water would be
returned to the process water ponds. The scenarios indicate that slurry water would be returned to
the site without treatment other than removal of solids.
Roy A. Stein, Ph.D.
No-Failure Mode of Operation. My comments regarding the no-failure mode of operations and
their impact on salmon can be found under Question 3.
EPA RESPONSE: See response to Question 3.
Road Use I: Page 5-60. Beyond calcium chloride, how can we be confident that the typical
chemicals that derive from highway use will not occur on this mine road (as noted on page 5-60)? Is
it because the low volume of traffic? If so, would not we expect accumulation through time... over
the 78 years of the mine operation (see Appendix G for some detailed analysis: should some of this
material be added to the main report?)? What about the impact of road dust on nearby aquatic
systems (wetlands, streams, rivers, etc.)?
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EPA RESPONSE: The text relating to traffic and contaminated runoff has been modified in the
revised assessment to read: "It is unlikely that the potential transportation corridor would have
sufficient traffic to significantly contaminate runoff with metals or oil, but stormwater runofffrom
roads at the mine site itself might contain sufficient metal concentrations to affect stream water
quality." Though traffic-associated contaminants may be expected to increase over time, they
would probably not be as significant as stormwater runoff-associated metals from the mine site. As
noted in the revised assessment, the main impact of dust from the transportation corridor on
salmonids would likely be a reduction in riparian vegetation and subsequent increase in fine bed
sediment. The main impact of dust at the mine site would be a direct increase in fine bed sediment
due to mine construction and operation (the effects of increased sediment loading are discussed in
Section 10.3.4).
Road Use II: Page 5-62 to 5-63 (plus Appendix G: again, as with other appendices, include more of
this information in the main report). Will there be frost heave of the road bed such that specific
structures will have to be installed to prevent this movement of the road bed? These roads will be
treated with chemicals, such as calcium chloride, to keep the dust down and contribute to an ice-free
condition, but no data are available for the impacts of these chemicals on nearby streams. How then
do we deal with this issue (page 5-62 and 5-63)? The suggestion is that one needs to have roads built
at least 8 meters from streams, but this cannot be the case in this situation, simply because of the
large number of streams, rivers, and wetlands along the road corridor? More detail as to the impact of
the transportation corridor should be added, including issues, such as truck accidents, fuel spills,
other chemical spills, etc.
EPA RESPONSE: The assessment does not address potential frost heave of the road bed,
although this factor will need to be considered during design of a road Additional information has
been added to the revised assessment on the potential impact of calcium chloride on nearby
vegetation, surface water, groundwater and aquatic species. According to the USDA Forest
Service (1999), application of chloride salts should be avoided within 8 m of water bodies. We
agree that the 8 m buffer zone for salts would be difficult to maintain, but it could be achieved at
some cost in dust suppression and winter road salting. It would not require keeping roads out of
that zone.
Additional information from Appendix G is incorporated into the main text, and the appendix is
referenced in a number of places. The revised assessment contains greater detail on the potential
impact of the transportation corridor. For example, the assessment now factors traffic estimates
into assessments of chemical spills from transport truck accidents (Section 10.3.3) and potential
impacts from dust (Section 10.3.5). Fuel spills are covered in Chapter 11.
Road Use III: page 5-71 (plus Appendix G). The road will intersect multiple streams and rivers
along the northern end of Iliamna Lake, where as many as one third of the sockeye salmon in this
lake spawn. And this is where the causeway across Iliamna Lake will be built as well. From my
perspective, it seems that impacts on spawning sockeye will be large in this area (without saying
anything about causeway: will there be culverts or bridges to allow water and fish to communicate
with the rest of the lake)? I would argue this is important, given salmon are attracted to certain odors
and water-flows and these odors and water-flows are coming from inlets streams into Iliamna Lake.
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Preventing any sort of blockage of water flow or salmon migration would be the goal. Are there other
issues that should be considered when building this causeway?
EPA RESPONSE: The assessment makes no mention of a causeway across Iliamna Lake. We
believe the commenter is referring to a proposed causeway over the upper end of Iliamna Bay,
which is part of Cook Inlet. Culverts or bridges would be built to allow fish access between streams
crossed by the proposed road and Iliamna Lake. The issue of culvert blockage is discussed in the
assessment.
Road Use IV. Points made by public testimony reinforces the idea that as this area is opened to the
public, the opportunity for new, invasive species to colonize this pristine ecosystem increases
dramatically, likely to 100%. Simply put, invasive species will now be carried by humans via the
road, inadvertently, into this previously inaccessible watershed.
EPA RESPONSE: We assume that the proposed road would be closed to the public during mining
operations but potentially could become a public road after mining operations cease. Even when
not open to the public, construction and operation of the proposed transportation corridor increase
the probability that new terrestrial and aquatic species will be transported to and potentially
establish themselves in the Bristol Bay region. If the road were opened to the public, the
probability of colonization by invasive species may increase further, but rates of introduction by
industrial and public vehicles cannot be distinguished given available information. Invasive
species are addressed in Section 10.3.6 of the revised assessment.
William A. Stubblefield, Ph.D.
The document appears to adequately address potential questions associated with habitat loss due to
hydrologic changes, especially considering the hypothetical nature of the mine and the lack of
specific detailed information regarding an actual proposed facility and all of the associated
operational details of the facility. The assessment of potential impacts and ecosystem protection
parameters is predominately based upon the publication of Richter et al. (2011). Additional support
and evaluation of these recommendations for fisheries populations in the Bristol Bay area should be
closely evaluated.
EPA RESPONSE: Prompted by this comment, we consulted with regional biologists and
hydrologists to evaluate the suitability of the sustainability boundary approach for flows. We asked
them if there was any reason that fish populations in these streams, or the specific hydrology of
the area, made it exceptional with regard to this approach (e.g., was there any reason to think that
the Richter approach was not applicable here). We received uniform support for applying this
approach to Bristol Bay streams. We strengthen our emphasis that this is a precautionary
approach, and that the detailed hydrologic and habitat modeling work that PLP contractors have
begun will help provide a useful basis for more sophisticated flow-habitat modeling.
STUBBLEFIELD RESPONSE: This response seems to adequately address the initial
comment.
EPA FINAL RESPONSE: No response required.
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Dirk van Zyl, Ph.D., P.E.
Chapter 5 of the EPA Assessment is entitled: "Risk Assessment: No Failure". Chapter 5 presents an
evaluation of habitat loss and modification resulting from the hypothetical mine. A summary of the
"risks" associate with the "no failure" case is provided in Chapter 8. There is specific focus on
evaluating the magnitudes of the losses and modifications to the environment.
EPA RESPONSE: No change requested or required.
A risk assessment addresses three questions (Kaplan and Garrick, 1981):
• What can happen? (i.e., What can go wrong?)
• How likely is it that that will happen?
• If it does happen, what are the consequences?
There are a large number of risk assessment methods and it is common to express the magnitude of
risk as a combination of likelihood of occurrence and consequences (IEC, 2009). This is the typical
outcome for engineering assessments of systems. For example, in the case of a Failure Mode and
Effects Analysis (FMEA), it would be typical to develop a risk matrix to combine likelihood of
occurrence and consequences to express the level or magnitude of risk in qualitative terms
(Robertson and Shaw, 2012).
The EPA Assessment describes the two components of risk but does not provide any information on
the magnitude of the risk. For example, for the no-failure condition it describes the length of streams,
areas of wetlands, etc. that will be impacted by developing the mine, i.e. the consequences. One may
argue that the likelihood of occurrence of these consequences is unity (or certainty) if the mine is
developed, as this is not specifically addressed by the report.
EPA RESPONSE: The risk assessment does address engineering risks in the manner specified,
including magnitudes of spills, leakage, etc., and the consequences for water and habitat quality.
We now explicitly clarify that losses of stream length are unavoidable for a project of this
magnitude (Chapter 7). The magnitude of the risk or the likelihood that the stream lengths will be
lost if the mine is constructed is 100%.
One would next expect an expression of the magnitude of this risk based on some comparison of the
consequences to a set of outcomes that could result in acceptable or unacceptable risks. The EPA
suggests this as an approach in its 1998 Guidelines for Ecological Risk Assessment (EPA, 1998): "In
some cases, professional judgment or other qualitative evaluation techniques may be used to rank
risks using categories, such as low, medium, and high, or yes and no". Quantitative approaches such
as fuzzy logic has also been used to develop expressions of magnitude of risk as described by EPA
(1998): "For example, Harris et al. (1994) evaluated risk reduction opportunities in Green Bay (Lake
Michigan), Wisconsin, employing an expert panel to compare the relative risk of several stressors
against their potential effects. Mathematical analysis based on fuzzy set theory was used to rank the
risk from each stressor from a number of perspectives, including degree of immediate risk, duration
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of impacts, and prevention and remediation management. The results served to rank potential
environmental risks from stressors based on best professional judgment".
EPA RESPONSE: Although the 1998 ERA Guidelines describe professional judgments as an
acceptable method for ranking risks in appropriate circumstances, it is not appropriate for this
assessment. The purpose of this assessment is not to rank risks. It is to estimate, as far as existing
data and knowledge allow, the risks associated with potential mining activities in the Bristol Bay
watershed EPA decided during the problem formulation that this assessment would be based as
much as possible on published science. An assessment based on elicitation of expert judgment
could be performed in the future, if desired.
It is unclear to the reader how significant a loss of 87.5 km of streams in the Nushagak River and
Kvichak River watersheds is to the overall ecosystem. Are there any criteria that can be used to
develop such an expression? Can a multi-stakeholder workshop (as is often done) be used to develop
such criteria and expressions of risk magnitude? Without having such expressions of risk magnitude
it is impossible for those without specific expertise in salmonids to evaluate whether this is a
significant risk. Price et al. (2010) states that: "Between 1999 and 2008, 3,500 fish passage barrier
culverts were replaced with fish-passable structures, reportedly opening nearly 5,955 km of fish
habitat in Washington streams (Governor's Salmon Recovery Office 2008)". Comparing the loss of
85 km to this gain of 5,955 km seems to imply that 85 km loss may represent a relatively small risk,
which may not be the case at all. However, the EPA Assessment does not provide any insight in the
magnitude of risk except to provide a value for the consequences.
EPA RESPONSE: The purpose of the assessment is not to assign significance to the risks, but to
provide information for decision makers on the consequences of mining.
EPA did conduct a multi-stakeholder conference to determine the significant endpoints and
exposure pathways for the assessment. However, EPA decided during the problem formulation
that this assessment would be based on published science. Therefore, a multi-stakeholder
workshop would not be an appropriate mechanism to estimate risks or their significance.
Comparing the potential loss of salmon-supporting streams in the Nushagak and Kvichak River
watersheds to restoration of streams in Washington for salmon recovery may not be very useful.
The comment does illustrate that seemingly inconsequential or insignificant losses have frequently
led to diminished or even lost salmon stocks. In the example cited, apparently 3,500 seemingly
inconsequential actions had to be remedied at public expense because of their cumulative impacts.
VAN ZYL RESPONSE: The response indicates that: "The purpose of the assessment is not to
assign significance to the risks, but to provide information for decision-makers on the
consequences of mining." It is the author's opinion that the decision-makers will also need
some context of comparative information to make a realistic decision. It seems to the author
that providing acute and chronic quotients in Chapter 8 effectively provides significance of
risks. Please consider the consistency of approaches.
EPA FINAL RESPONSE: From an ecological perspective, the quotients in Chapter 8 are
equivalent to the stream losses and flow alterations.
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Similar comments can be made with respect to the relative risks associated with the other losses of
ecological functions for other failure modes.
EPA RESPONSE: See response to previous comment.
It is recognized that it is important to maintain separation between the risk assessment and risk
management functions. As expressed by the National Research Council Panel in their report on
Science and Decisions (NRC, 2009): "The committee is mindful of concerns about political
interference in the process, and the framework maintains the conceptual distinction between risk
assessment and risk management articulated in the Red Book. It is imperative that risk assessments
used to evaluate risk-management options not be inappropriately influenced by the preferences of
risk managers".
EPA RESPONSE: We agree with this comment and its implication that assessors should not judge
significance. No changes suggested or required
Providing an expression of risk magnitude should not interfere at all in the separation of risk
assessment and risk management, but should provide the risk manager with one extra level of
analysis and insight from the expert assessor of the problem at hand. Multi-stakeholder interaction
will only serve to enhance the value of the risk ranking.
EPA RESPONSE: See response to previous comment on this topic.
On p. 4-33, it is stated that after closure: "No PAG waste rock would remain on the surface". It is
also stated in Chapter 4 that PAG and NAG waste will be segregated. On p. 5-48, it is stated that:
"However, the primary concern during routine operation would be waste rock leachate. That leachate
would become more voluminous as the waste rock piles and uses of waste rock for construction
increased during operation. After mine closure, it would be a major source of routinely generated
wastewater along with water pumped from the TSF and pit. Leachate composition from tests of the
three waste rock types (Tertiary, East Pre-Tertiary, West Pre-Tertiary) is presented in Tables 5-14
through 5-16". There is no specific indication which of these waste rock types could be described as
PAG or NAG and Chapter 5 seems to assume that these 3 samples are representative of the total
amount of waste rock, about 4 billion tonnes for one mine scenario. If all the PAG material will be
removed from the surface, as stated in the scenario in Chapter 4, and the NAG will not generate acid
drainage, then it is difficult to understand why the waste rock piles and waste rock used for
construction (supposedly all NAG at this stage) would be the major source of "routinely generated
wastewater."
Note that it is further unclear why there would be water pumped from the tailings and the pit if the
TSF were closed, as discussed above, and if it will take the mine pit 100 to 300 years to fill. Some
clarification is in order.
EPA RESPONSE: This issue has been clarified in the revised assessment. PAG and NAG waste
rocks would be identified during the course of mining, but the available test results indicate that
pre-Tertiary rock is PAG. The PAG waste rock would be segregated and none would remain at
mine closure. However, some will be on the surface during operation. In addition, the NAG waste
rock produces potentially toxic leachates that must be collected and treated Water could be
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pumped from the TSFs and the pit for treatment before discharge. Treatment ofpit water would
occur once it is a source rather than a sink.
A further reference to the fate of waste rock after closure is found on p. 5-77 of the EPA Assessment:
"Under the mine scenario, the mine pit, waste rock piles, and TSF would remain on the landscape in
perpetuity and thus represents permanent habitat loss." It should be noted that the scenario states that
PAG will not remain on the surface, whatever volume and area of land surface that represents.
EPA RESPONSE: Section 6.3.3 of the revised assessment clarifies that no PAG waste would
remain on the surface.
The descriptions of exposure and exposure-response resulting from the transportation corridor in
Section 5-4 of the EPA Assessment focus on potential impacts and make use of references that are
clearly not representative of the expected road construction. A number of these references date from
1975 and 1976 (p. 5-59) and are not necessarily representative of road design and construction
practices in 2012. On p. 5-62, the following statement and reference is given: "Sediment loading
from roads can severely affect streams below the right-of-way (Furniss et al., 1991 and references
therein)". This reference is specifically focused on forest and rangeland roads, clearly not
representative of a major transportation road between a mine and the port facilities from where its
products are shipped. This publication contains many recommendations specifically for forest and
rangeland roads and some of them are indicative that it is not applicable to the transportation corridor
for a major mine access road: "Design cut slopes to be as steep as practical. Some sloughing and
bank failure is usually an acceptable trade-off for the reduced initial excavation required" (p. 306);
and "stream crossings can be considered dams that are designed to fail. The risk of failure is
substantial for most crossings, so how they fail is of critical importance" (p. 310). The reference also
refers to the application of oil as a dust abatement additive on p. 312, which is hardly acceptable
practice. In my review, I did not find that any of the references used in the EPA Assessment refer
specifically to mine roads such as those considered for the transportation corridor at the Pebble Mine
scenario.
EPA RESPONSE: The information cited from the two publications noted by the commenter is still
true today. The first use of Darnell (1976) was incorrect, and has been changed to Furniss et al
(1991). Although Furniss et al (1991) focuses on forest and rangeland roads, it is a seminal
publication on the potential effects of roads, particularly as they relate to salmon. The general
conclusions of that paper should be applicable to the transportation corridor described in the
assessment. Furniss et al (1991) lists a number of guidelines for road design and construction
that will help minimize adverse effects on salmonid habitats. It does not specifically advocate the
application of oil as a dust abatement additive. It merely states that whatever chemicals are used,
they should be applied so as not to enter streams, and that subsequent transport of these
substances into water courses should be evaluated
The failure frequencies cited in the revised assessment are from modern roads and not restricted to
forest roads. Because the proposed mining would take place in an undeveloped area, the literature
used in the assessment is necessarily from areas outside of the Bristol Bay region. However, we
used recent literature from representative environments to the extent possible. Lastly, information
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on current design standards that would be used along the proposed transportation corridor is now
included within text boxes throughout Chapter 10.
It is further interesting that it is stated on p. 5-60 that there will be 20 bridges and 14 culverts along
the road without referring to this as an assumption, and no reference is cited for this information.
Will there be a change in impact if the decision is made to build 30 bridges and 4 culverts or 34
bridges and no culverts?
EPA RESPONSE: The estimate of 20 bridges came from Ghaffari et al. (2011). In the revised
assessment, crossings that would be bridged (now 18) are based on mean annual streamflows, as
explained in the text. If a decision was made to build more bridges andfewer culverts, there would
be a change in impact, but scenarios with 30 or more bridges are probably not realistic.
The discussion on the potential impacts of the transportation corridor on salmonids serves the
purpose of highlighting some aspects that engineers and fish biologists must take into account when
designing and maintaining the final transportation corridor for the Pebble Mine and other mines in
the Bristol Bay area. However, this assessment does not appropriately describe the scale and extent
of the risks to salmonid fish due to operation of a transportation corridor under the no-failure mode of
operation.
EPA RESPONSE: The "no failure" mode of operation was meant to illuminate the effects that
would occur solely from a mine footprint, even in the absence of accidents or failure. This term
has been eliminated in the revised assessment. The no-failure scenario from the draft assessment
has been changed to a section on the effects of the footprint of a mining operation, without regard
for operational problems (Chapter 7). The revised assessment places the streams along the
transportation corridor into the context of the entire Nushagak and Kvichak River watersheds with
respect to important watershed attributes such as discharge, channel gradient, and floodplain
potential. Potential risks to fish habitats and populations associated with the proposed corridor are
then evaluated in some detail.
Phyllis K. Weber Scannell, Ph.D.
The no-failure model makes a number of assumptions about how the mine will be developed - some
may be accurate, some may be considerably different. It is important to take under consideration that
Pebble is currently a prospect, not a mine. Should this project proceed to mine development, it will
be incumbent on the mining company to develop a rigorous mine plan that includes detailed
information on all aspects of a future project. This mine plan will be reviewed by state and federal
staff with experience in large project development.
EPA RESPONSE: EPA agrees with this comment. No changes suggested or required.
WEBER SCANNELL RESPONSE: The reviewer is satisfied.
The expanded descriptions of different mine scenarios contained in the revised Assessment
clarify the possible sources of risk to salmonid fish.
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EPA FINAL RESPONSE: No response required.
The no-failure model discusses the amount of riverine habitat that will be lost to mining by the mine
pit, tailing storage facility, and waste rock dumps. Anadromous fish habitat is protected under Alaska
Statute 16.05.840-870. The statute requires review of a project potentially affecting fish habitat and,
where necessary, avoidance, mitigation, or compensation. A project must provide free passage of
fish; the project cannot be placed in such a way that fish are prohibited from moving into the
upstream reaches. Estimates of habitat loss from the mine footprint are not possible without a more
detailed plan of operations for the mine.
EPA RESPONSE: The scenarios presented are meant to represent those expected as typical for
mining ofporphyry copper deposits of this type, and are based on preliminary mine plans from
Northern Dynasty Minerals (Ghaffari et al. 2011). Although layout of mining components at a site
may differ somewhat from what we present in the scenarios, the main components of mining will
remain the same for open-pit mining. Given stream density in the area, direct losses of stream and
wetland habitat of a similar magnitude would be inevitable with projects of the specified
magnitudes.
WEBER SCANNELL RESPONSE: The reviewer agrees.
The expanded discussions of the possible mine scenarios are important additions and help
clarify possible effects to the aquatic environment.
EPA FINAL RESPONSE: No response required.
There are many aspects of the development of a large mine project that need thorough review to
ensure that habitats are protected. These include, but are not limited to: classification and storage of
waste rock, lower grade ore, overburden, and high grade ore; development and maintenance of
tailings storage facilities; development and concurrent reclamation of disturbed areas, including
stripped areas and mine pits; collection and treatment of point and non-point source water; quantity
and timing of discharges of treated water; monitoring of ground water, seepage water and surface
water; and biomonitoring. The transportation corridor will require review and permitting of every
stream crossing of fish-bearing waters. In addition, plans should be developed for truck wheel-
washing to minimize transport of contaminated materials.
EPA RESPONSE: EPA agrees that these aspects would need to be subject to a thorough review
during the development and approval of a detailed mining plan. No changes suggested or
required.
WEBER SCANNELL RESPONSE: The reviewer is satisfied.
The revised Assessment provides some discussion of the in-depth reviews that would be
required during the permitting process. This information addresses the concerns raised by the
reviewer.
EPA FINAL RESPONSE: No response required.
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Paul Whitney, Ph.D.
Material Resource Areas. Material resource areas, mentioned on page 4-34, for the road and pipelines
should be discussed in more detail. Will aggregate be required? If so, where are the aggregate
resources in relation to floodplains? I spent a summer surveying material resource areas for a
proposed arctic and subarctic pipeline and access road. Suitable material resource areas are sizeable
and are often important (e.g., aggregate) for wildlife (such as bears that hibernate or survive the
winter in dens) and fishery resources. Sometimes dens can only be excavated in non-permafrost (i.e.,
aggregate) soils. It appears the project area is in a zone of discontinuous permafrost, but permafrost
could be more continuous in the higher elevations along the road through the Kenai Mountains. An
accurate assessment should determine the permafrost location(s), as well as the area and importance
of material resources for fish and wildlife. In addition, Reclamation Plans for the material resource
areas should be briefly discussed to ensure that areas mined for aggregate will not avulse and capture
streams.
EPA RESPONSE: We agree with the commenter that the impacts of material resource areas to
wildlife, fisheries, and other subsistence resources could be significant and must be addressed in
an environmental impact statement and as part of the 404permit review. Review ofpotential
material resource areas was not included in the scope of this assessment.
Water for Dust Control. Dust control for the 86-mile proposed haul road will likely require a lot of
water. Where will this water come from? Withdrawal from streams crossed by the haul road could
have impingement and flow reduction consequences. Adequate screening could solve the
impingement issue. Some back-of-the-envelope calculations could determine if water withdrawals
for dust control could alter the projected hydrographs when salmonids are present in the streams.
EPA RESPONSE: We expect water for dust control to be a small amount from any one source.
Permits would be required from the State ofAlaska that would address impingement issues. We do
not expect this to be a major issue.
3.7 Charge Question 5
Do the failures outlined in the assessment reasonably represent potential system failures
that could occur at a mine of the type and size outlined in the mine scenario? Is there a
significant type of failure that is not described? Are the probabilities and risks of failures
estimated appropriately? Is appropriate information from existing mines used to identify
and estimate types and specific failure risks? If not, which existing mines might be
relevant for estimating potential mining activities in the Bristol Bay watershed?
David A. Atkins, M.S.
The Assessment focuses on some low probability, high impact failures (e.g., TSF failure), and
presents summaries of failures at existing mines. The majority of the focus is on catastrophic failures,
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such as TSF, pipeline, water collection and treatment, and road and culvert. Anecdotal information
regarding mine failures is numerous, but often not well documented, so it is difficult to get
information on the details of failures of other projects. It is also difficult to extrapolate the probability
of failure from one site to the next, and the report stresses the wide range of uncertainty, depending
on design and environment. Without a more detailed understanding of the mine plan and associated
engineering, as well as additional detailed analysis, it is difficult to determine if the failure
probability estimates presented in the Assessment are reasonable.
EPA RESPONSE: The authors concur with the conmienter that it can be "difficult to get
information on the details offailures of other projects". The statistics for historic tailings dam
failures are derived from the largest available database and include many tens of thousands of
dam-years. The pipeline failure data cover millions of kilometer-years ofpipeline experience. The
data on failures of water collection and treatment systems and of culverts are less extensive. We
also recognize that even with detailed engineering and design information, the prediction of
failure probabilities is extremely difficult. Finally, since all of these low-probability failures are
statistical phenomena, the actual experience at any one site could be vastly different than another
similar site, even when the failure probabilities have the same distribution.
ATKINS RESPONSE: This response is adequate.
EPA FINAL RESPONSE: No response required.
The focus on catastrophic failures also takes attention away from what is probably a more likely
scenario. Every project is subject to accidents and smaller, non-catastrophic failures that have
varying degrees of consequence. Sometimes these failures are easily identified and fixed and other
times they can go un-noticed for periods of time.
EPA RESPONSE: Because the number ofpotential failures is extremely large, it is necessary to
choose a representative set offailure scenarios. The revised assessment includes more failure
scenarios (e.g., diesel pipeline failure, quantitative wastewater treatment plant failure, truck
accidents and spills, and refined leachate seepage scenarios) and explains why these particular
failure scenarios were chosen.
ATKINS RESPONSE: This response is adequate.
EPA FINAL RESPONSE: No response required.
It would be helpful to describe some smaller-scale failures that have occurred at mine sites. A partial
list includes: accidents and spills along the transportation corridor or within the mine site;
unanticipated seepage of contaminated water that may be difficult to detect, collect and treat;
movement of water along preferential flow pathways that are difficult to characterize; temporary
failure of water collection and treatment systems; mistakes in engineering analysis that underestimate
the volume of water that must be collected and treated or overestimate the volume of water available
for use; and designing based on incomplete data and understanding of climate conditions.
EPA RESPONSE: There is a wide variety of failures that could occur, including those provided by
the conmienter. Because the number ofpotential failures is extremely large, it is necessary to
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choose a representative set offailure scenarios. The revised assessment includes more failure
scenarios (e.g., diesel pipeline failure, quantitative wastewater treatment plant failure, truck
accidents and spills, and refined seepage scenarios) and explains why these particular failure
scenarios were chosen.
ATKINS RESPONSE: This response is adequate.
EPA FINAL RESPONSE: No response required.
Steve Buckley, M.S., CPG
The engineering failures reasonably represent potential system failures outlined in the mine scenario
based on historic porphyry copper deposits of this type. It is less clear if the failures reasonably
represent a mine scenario based on state of the art engineering and mitigation practices. Appendix I
provides some information related to potential system failures and possible mitigation measures
designed to minimize these risks but these are not treated in any detail in the assessment. It would be
difficult to pull together the most modern engineering and mitigation practices from around the world
but it could help bound the risks associated with modern mine development.
EPA RESPONSE: Our purpose in the assessment is to evaluate the risks from hazards resulting
from a mine operated with appropriate mitigation measures for design, operation, monitoring and
maintenance, and closure. Accidents and failures happen regardless of mitigation measures; thus,
effects of several failures are evaluated. Mitigation measures related to our mine scenarios are
now clearly discussed in Chapter 6.
BUCKLEY RESPONSE: The revisions clarify when and where potential mitigation measures
would be treated in the regulatory process.
EPA FINAL RESPONSE: No response required.
The Red Dog mine in northwest Alaska might be relevant for estimating potential mining activities in
the watershed. Although the characteristics of the deposit differ significantly, at roughly 150 million
tons it is half the size of a reasonable minimum mine scenario and would be helpful to characterize
some minimum mine development scenario.
EPA RESPONSE: A third mine size scenario, representing the worldwide median size porphyry
copper mine (Singer et al. 2008), is included in the revised assessment.
BUCKLEY RESPONSE: This improves the assessment.
EPA FINAL RESPONSE: No response required.
Courtney Carothers, Ph.D.
The potential failures outlined in this assessment include: tailings dam failures, pipeline failures,
water collection and treatment failures, and road and culvert failures. These failures appear to
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represent the key potential failures for this mining scenario, their risks appear to be estimated
reasonably, and statistics from existing mines appear to be used appropriately, although I have no
particular expertise with which to evaluate this assessment. As we discussed in our peer review
panel, the focus here is on catastrophic failure. More detail should be provided on likely non-
catastrophic failures, ones that would be more difficult to detect.
EPA RESPONSE: Because the number ofpotential failures is extremely large, it is necessary to
choose a representative set offailure scenarios. The revised assessment includes more failure
scenarios (e.g., diesel pipeline failure, quantitative water treatment failure, and refined leachate
seepage scenarios) and explains why these particular failure scenarios were chosen. We did
include leachate seepage scenarios (Chapter 8), which would be more difficult to detect than
catastrophic failures.
CAROTHERS RESPONSE: EPA response is sufficient.
EPA FINAL RESPONSE: No response required.
Dennis D. Dauble, Ph.D.
My experience in system failure of mines of the size and type outlined in the scenario is limited.
However, what does seem to be missing is the long-term effects of leachates to receiving water
bodies in any type of risk scenario, including both non-failure and failure modes. That is, assuming
no catastrophic failure, how might tailings constituents interact with aquatic habitats seasonally, such
as during periods of snowmelt and severe rainfall events?
EPA RESPONSE: The original assessment contained a scenario in which tailings leachate was
not fully contained and reached a stream (Section 6.3). The revised assessment includes estimates
of leachate escaping from the TSFs and from the waste rock piles, bypassing the collection
systems, and entering the streams (Chapter 8). The estimated loadings of copper and other
elements from these leachate flows are included in stream concentration estimates. The
assessment discusses the impacts of these concentrations on the aquatic habitat and biota.
The conmienter is correct that we did not include a scenario in which the dam does not fail, but
snowmelt and severe rainfall would result in overtopping and release of untreated water. That is
very plausible, but there are just too many possible failure scenarios to include more than a few of
them,
DAUBLE RESPONSE: If the scenario is plausible, it should be included in the assessment.
However, if the potential risk is covered based on a similar or parallel scenario, then it should
be stated as such.
EPA FINAL RESPONSE: We have added a spillway release scenario to Chapter 8 of the final
assessment.
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Gordon H. Reeves, Ph.D.
No comments on this question.
Charles W. Slaughter, Ph.D.
Potential failures seem reasonable, based on history of other mining operations. However, the
consequences of hydrologic extremes during winter (frozen soil) conditions are not adequately
addressed. The possibility of the mining operation and the transportation network encountering
discontinuous permafrost is not mentioned, although at least some soils maps indicate permafrost
presence.
EPA RESPONSE: Wahrhaftig (1965) reports that permafrost is sporadic or absent in the
Nushagak-Bristol Bay Lowland (Table 3-1). If permafrost were detected during project
development or construction, the designs would need to address any potential impacts on the
infrastructure and potential impacts of the infrastructure on the permafrost. Frozen soil could
improve vehicular access to parts of the project site and minimize the disturbance from such
access.
The occurrence of an extreme hydrologic event, such as heavy rainfall on frozen soil or heavy rain
on an existing snowpack, could produce unusually heavy runoff and higher than normal stream
flows. We analyzed the impact of a tailings dam failure during the Probable Maximum
Precipitation (PMP) event, thereby generating the Probable Maximum Flood (PMF). The
increased flow due to precipitation was, in most of the scenarios, small compared to the flow
released from the TSF. Any increases in the peak runoff due to frozen soil or melting snowpack
would also be small relative to the TSF release, so the modeled scenario can be considered a
reasonable bounding estimate.
SLAUGHTER RESPONSE: Relative to a TSF failure flow release, agree.
EPA FINAL RESPONSE: No response required; however, in the final assessment, flooding to
generate overtopping is no longer simulated.
Designs for the components of the mine infrastructure would need to consider the natural cold
region conditions and incorporate appropriate design features and safety factors to achieve an
acceptable level of performance. Gliaffari et al. (2011) says "The Pebble deposit is located under
rolling, permafrost-free terrain in the Iliamna region of southwest Alaska..." and "The deposit is
situated approximately 1,000ft amsl, in an area characterized by tundra, gently rolling hills and
the absence of permafrost." Gliaffari et al. (2011) describes the transportation corridor thusly:
"The road route traverses terrain generally amenable to road development... There are no
significant occurrences ofpermafrost or areas of extensive wetlands." Nevertheless, if sporadic
areas of permafrost are discovered, the designs will need to address the interactions between the
infrastructure and the permafrost.
SLAUGHTER RESPONSE: Recognition of the Wahrhaftig and Selkregg references in the
revised Assessment is appreciated. Concern with encountering permafrost involves both
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engineering questions - i.e., soil stability upon thawing (dependent on grain size and
distribution), frequency of freeze/thaw occurrences, and broader "ecosystem" questions of
landscape dynamics and ecosystem function if previously perennially frozen ground warms -
as is probable both upon surface disturbance and consequent to long-term climate warming.
I don't understand your statement, "Frozen soil could improve vehicular access to parts of the
project site and minimize the disturbance from such access." Perhaps you are suggesting that
winter-only off-road vehicular access (with adequate snow cover) would be a management
option, as has been implemented in sectors of the North Slope and along the Dalton Highway?
While existence of a deep snowpack can improve over-snow vehicle travel (snow machines,
tracked vehicles), I fail to see how either perennially or seasonally frozen soil might either
"improve vehicular access" or "minimize disturbance." See Slaughter C.W., C.W. Racine,
D.W. Walker, L.A. Johnson, and G. Abele. 1988. Use of off-road vehicles and the consequences
for Alaska permafrost environments: a review. Environmental Management 14(l):63-72., or
Slaughter, C.W., and J.W. Aldrich. 1989. Annotated bibliography on soil erosion and erosion
control in subarctic and high-latitude regions of North America. PNW-GTR-253, Pacific
Northwest Research Statin, USDA Forest Service, Portland OR. 234 p., among many possible
references.
You cite Ghaffari et al. (2011) as saying: "The road route traverses terrain generally amenable
to road development...There are no significant occurrences of permafrost or areas of extensive
wetlands." Based on your Figure 3.4, there should be only limited (if any) permafrost
encountered, and of course, engineering measures would be taken with whatever soil or
geologic conditions are actually encountered. But given your estimates throughout the
Assessment of the length of streams and areas of wetlands which would be encountered in the
transportation corridor (i.e., Section 10.3.1, Box 10.1), do you concur with Ghaffari's
characterization (almost dismissal) of wetlands encountered by the road route?
EPA FINAL RESPONSE: We agree with the commenter's point about frozen soil and vehicular
access, and retract this from our earlier response. The cited quote from Ghaffari et al. (2011) is
not included in the assessment, and was included in our earlier response to illustrate the relative
lack ofpermafrost in the area (as supported by Figure 3-4). We address effects of the
transportation corridor on wetlands in Chapter 10.
The probability approach outlined for potential TSF dam failure is unpersuasive. It is difficult to
relate to a number like "0.00050 failures per dam year," or to the implication on p. 4-47 that one can
expect a tailings dam failure only once in 10,000 to one million "dam years." This could suggest to
the casual reader that failure of the hypothesized TSF1 dam (for which one "dam year" is one year)
should not be anticipated in either the time of human occupation of North America, or the span of
human evolution.
EPA RESPONSE: The commenter is correct. The proposed dams, if designed, built, and
maintained to current engineering best practices, would be anticipated to have a low annual
probability offailure. However, the failure probability would not be zero. The writers concur with
the commenter that these low probability numbers may be difficult for the casual reader to grasp,
so we now also present estimates ofprobability in terms ofprobability failure over different time
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periods. The discussion of this issue has been expanded to clarify that the failure rate is a design
goal and is not based on empirical evidence.
SLAUGHTER RESPONSE: The revised and expanded discussion of Chapter 9 helps. Section
9.1.2 does clarify your reasoning. Box 9.1 and Table 9.1 demonstrate that failures can and do
occur. I remain uncomfortable with employing the terminologies of "dam year" or "mine year"
which allow suggesting one failure every 2000 mine years, or every 714 to 1754 mine years. A
cursory reading might well allow the impression that this means 2000 or 714 or 1754 years of
TSF1 at Pebble, and therefore possible failure is of no concern to the current or next ten to one
hundred generations. See also Table 14.1, which states that a tailings dam failure has a
recurrence frequency of 2500 to 250,000 years - allowing the interpretation a Pebble TSF
won't occur for the next 2500 years, so why worry? Could the text and/or an addendum to the
relevant tables and boxes, explicitly differentiate between your "probabilities" and "recurrence
frequencies", versus "predictions"? A calculated recurrence interval says nothing about an
event actually occurring this year, next year, or 2500 years in the future; I still suspect that
some readers and decision makers may not immediately understand this.
EPA FINAL RESPONSE: We agree that the probabilities and frequencies can be difficult to
understand. We have added Box 9-3, which explains how the failure frequencies and probabilities
are derived and how they can be interpreted. A condensed version of this material has been added
to the Executive Summary.
Box 4-6 suggests that the Operating Basis Earthquake (OBE) for a 7.5-magnitude event at the Pebble
locale has an estimated return period of 200 years. Such a return interval probability is difficult to
interpret, given the lack of historical seismic records for the region; in any event, such a return period
estimate is in no way predictive of future seismic activity, in year 2012 or year 2212. (The suggested
200-year return period should also be viewed in light of the 79-year suggested operating life of the
hypothetical Pebble operation, probable longer-time operations at other mineral extraction sites
which would be developed following implementation of Pebble and building from the infrastructure
associated with Pebble, and also the projected very long persistence of the TSFs following cessation
of active mining).
EPA RESPONSE: Box 9-2 of the revised assessment (Box 4-6 in the original draft) provided the
OBE and return period determined by NDM in the Preliminary Assessment. A detailed
engineering design and safety evaluation is outside the scope of this assessment. The discussion of
seismicity (Section 3.6) addresses the uncertainty in interpreting and predicting earthquake
magnitude and recurrence in the Pebble area.
SLAUGHTER RESPONSE: Figure 3.15 is particularly helpful, as is the revised discussion
offered in Section 3.6. Of course, I concur with elimination of the reference to a 200-year return
period for a 7.5-magnitude event.
EPA FINAL RESPONSE: No response required.
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Box 4-6 does note that "The return periods stated in Alaska dam safety guidance are inconsistent
with the expected conditions for a large porphyry copper mine developed in the Bristol Bay
watersheds, and represent a minimal margin of safety."
EPA RESPONSE: The return periods used are consistent with the Alaska Dam Safety Guidance,
however the operator could include an additional margin of safety in the design for critical
structures. The return period and seismic safety factors do not inform the failure analysis in this
assessment, but would be important considerations during the review process for any future mine
plan.
SLAUGHTER RESPONSE: OK.
EPA FINAL RESPONSE: No response required.
John D. Stednick, Ph.D.
The assessment reasonably addresses potential large system failures, but should include a variety of
smaller and perhaps more frequent failures (see Question 4). A large tailings storage facility failure
compared to a blocked road drainage culvert. The level of detail in the assessment of the potential
system failures varies considerably and baits the question—why? Does this demonstrate lack of
understanding of failure prediction, lack of failure prediction, or writing team expertise?
EPA RESPONSE: We do not believe that a blocked culvert requires or deserves the same level of
analysis as a tailings dam failure and spill. The latter is a much more complex phenomenon with
multiple consequences that require evidence and analysis such as the potential toxicity of the
spilled tailings. In contrast, blockage of a culvert is a relatively straightforward phenomenon.
Further, a TSF failure poses a much greater concern for stakeholders and local communities due
to the large magnitude of potential effects.
Tailings storage facility: The liquefaction phenomenon, internal and external erosion, seepage, and
overtopping are some of the main failure modes of tailings storage facilities. A large quantity of
stored water is the primary factor contributing to most tailings storage failures. The risk of physical
instability for a conventional tailings facility can be reduced by having good drainage and little (if
any) ponded water. Some suggest that the tailing pond freeboard should be able to accommodate the
100-year, 72-hour storm/streamflow event. What are the State of Alaska standards? Discuss the
probability of failure of a TSF from other than overtopping by a precipitation/streamflow event. The
potential of seismic activity and its effect on tailings storage and other earthworks needs to be
addressed.
EPA RESPONSE: The historic failure probabilities for tailings dams presented in the assessment
include all modes of failure, including slope instability, liquefaction, overtopping, erosion, and
seismic activity. Historical failures were discussed as supporting background information and
present a defensible upper bound on the failure probabilities. The failure probabilities used in the
assessment are based on Alaska's dam classification and required safety factors applied to the
method of Silva et al. (2008). The data presented by Silva et al. (2008) consider only the annual
probability offailure from slope instability, but the methodology is equally applicable to other
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failure modes. The discussion of failure probabilities in the revised assessment (Chapter 9) is
expanded to clarify this issue.
Chemical transport spill: Mine development and ore processing will require significant loads of
petroleum and chemical products. Although the exact processing formulations are not given, most
copper porphyry mines use similar formulation in ore flotation and processing. How will chemicals
be stored, transported, and recycled? What are the opportunities for accidents to occur?
EPA RESPONSE: Storage of chemicals is addressed in the assessment. Petroleum transport is by
pipeline and an assessment of the risk of spills has been added in Chapter 11 of the revised
assessment. Process chemicals would be transported by truck. Discussion of truck transport and
potential for accidents has been included in Chapter 10, including a quantitative analysis of the
risk of wrecks that cause spills into streams or wetlands.
Roy A. Stein, Ph.D.
Failures Appropriate for Mines of this Size and Type. Given my background, I can't answer with
any authority, though the comparisons seemed appropriate, though clearly no extant mines are as
large as the one proposed herein. Some of the public testimony spoke directly to comparisons with
existing mines in dry areas would be completely inappropriate because it is the hydrology of the
Bristol Bay watershed that would make it so very vulnerable to mining impacts.
EPA RESPONSE: No change suggested or required
Failures Not Described? I speak to failures associated with routine operations previously in this
review, as well as chemical spills along the transportation corridor. Also included herein should be
impacts of the Cook Inlet Port and potential spills, accidents, etc., on the marine ecosystem.
EPA RESPONSE: Because the number ofpotential failures is extremely large, it is necessary to
choose a representative set offailure scenarios. The revised assessment includes more failure
scenarios (e.g., diesel pipeline failure, quantitative water treatment failure, and refined seepage
scenarios) and explains why these particular failure scenarios were chosen. Discussion of
transport and potential for accidents has been included in Chapter 10, but risks are not evaluated
Potential impacts in Cook Inlet are important and should be considered in the regulatory process
should a company submit a permit. However, because this is an assessment of the Bristol Bay
watershed, evaluation of impacts from the port (and transportation corridor outside the Nushagak
and Kvichak River watersheds) is outside the scope of this assessment.
Probabilities and Risks of Failures. These seemed reasonably well documented, though again this
falls outside of my expertise. Even though out of my realm, I still would have liked a more
quantitative assessment of these risks, developed in a rigorous, defensible way. I am discouraged
when I understand that history (in the eyes of the mining company) is not a good predictor of the
future because technology has taken us so much farther along, reducing risks of whatever failure
significantly. In my view, this is a specious argument and one that should be roundly put to bed by
the authors of this report. History is indeed the absolute best predictor of the future and technological
changes that have occurred since past mines must be absolutely and critically evaluated to determine
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if indeed risks do go down. This is a serious issue and one that should be addressed with some rigor
by the authors.
EPA RESPONSE: Historical failures were discussed as supporting background information. The
failure probabilities used in the assessment are based on Alaska's dam classification and required
safety factors applied to the method of Silva et al (2008). We have strengthened the discussion of
failure probabilities (Chapter 9) to the extent that available evidence allows.
Existing Mines as Comparisons. Given my background, I can't answer with any authority, though
the comparisons seemed appropriate, though clearly no extant mines are as large as the one proposed
herein (nor does it incorporate all we have learned in the mining business since the last mine for
which we have data). Even so, I again caution the authors that these existing, historical mines provide
the best data we have to estimate risks of failure and that, under no circumstances, should one accept
the indefensible argument that progress with mine safety (speaking broadly, not just human health)
has progressed to the point that these risks, previously quantified in these older mines, are now small.
As suggested above, we have no other quantitative values for risk, except for existing mines and we
cannot simply erroneously lower the risk based on new, untested technologies.
EPA RESPONSE: We agree that it is appropriate to include in our scenarios technologies that are
in current use and not those that are untested, and thus have done so. No change suggested or
required
Proportional Losses of Salmon. Is it possible to estimate the proportion of the salmon runs
compromised in the face of major failures in tailing storage facilities or other failures? In other
words, I would recommend adding a chapter that uses best estimates of salmon produced within the
Bristol Bay watershed and then assess the maximum impact of, let's say, a Tailing Storage Facility
failure—with this failure, might we lose 10%, 40%, or 75% of our salmon productivity? In addition
to this estimate, one might estimate the number of stocks or unique genetic units lost with a major
failure? I know these numbers are difficult to get, but if one begins with escapement from these
systems as well as insights from harvest, we may be able to bound these impacts. Only in this fashion
can we put these data into context. This exercise also will serve to counter the argument by the
mining company that they are only destroying some small percentage of salmon habitat and hence
(assuming a linear relationship between habitat lost and salmon eliminated) only some very small
percentage of salmon. Because losing 2% of critical headwaters habitat may translate to huge losses
of salmon (say 20%), one simply cannot assume a linear relationship between habitat and salmon.
Explicitly making this argument improves the rigor of the main report.
EPA RESPONSE: The fact that salmon productivity cannot be assumed to be linearly related to
habitat has been more explicitly elaborated in the revised assessment. Due to lack of
comprehensive estimates of limiting factors across the impacted watersheds, population level
effects could not be quantitatively estimated, except in the most severe cases where total losses of
runs could be reasonably assumed Our ability to estimate population level effects was limited to
situations that were assumed to completely eliminate habitat productivity and capacity in an entire
watershed for which estimates of escapement could be inferred For this assessment, these
conditions are only met in the TSFfailure scenario that completely eliminates or blocks access to
suitable habitat in the North Fork Koktuli River. In that case, we estimate that the entire Koktuli
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portion of the run (-29% of Nushagak escapement) could be lost. Higher proportional losses
would occur if significant downstream effects occurred due to transport of toxic tailings fines
beyond the Koktuli as modeled under the Pebble 2.0 TSFfailure.
Correlations between Ocean and Terrestrial Conditions. From the literature (see Irwin and
Fukuwaka. 2011. ICES J. Mar. Sci. 68: 1122 as just one example), we know what climatic conditions
lead to poor rearing conditions in the ocean, thus compromising growth and ultimately survival of
salmon. Given these ocean conditions, might we have correlative effects in the terrestrial
environment, thus leading to a cumulative effect of ocean and terrestrial impacts? For example, if
particular oceanic conditions underlie poor survival, might this correlate with an increased
probability of flooding, leading to a higher probability of a Tailings Storage Facility failure, leading
to a cumulative synergistic effect that could be multiplicative in its negative impact on salmon
populations? Was there any attempt to correlate these impacts? Just how realistic is it to reflect on
these sorts of multiplicative effects? Might these effects have a catastrophic effect on salmon
populations?
EPA RESPONSE: Pursuing this hypothesis would require a research effort that is beyond the
scope of this assessment.
William A. Stubblefield, Ph.D.
The scope of failures described in the assessment seems to be sufficiently comprehensive and all
likely failure-types are considered. The probabilities and risks for failure seem to be adequately
estimated, given the state-of-the-science; however, these estimates are likely to be very sensitive to
site-specific concerns and operational considerations. Once site-specific information is available, it is
likely that much better estimates of failure potential at a site can be developed.
EPA RESPONSE: We agree that more site-specific information could support more site-specific
estimates. No change required.
STUBBLEFIELD RESPONSE: I concur, the US EPA authors have acknowledged the benefit
of more site-specific information and until that information becomes available there is little
additional that can be done to estimate failure potential.
EPA FINAL RESPONSE: No response required.
Dirk van Zyl, Ph.D., P.E.
Failure modes outlined in the EPA Assessment do not reasonably represent the potential failures that
could occur at a mine of the type and size outlined in the mine scenario.
The EPA Assessment considers a series of large, or catastrophic, type failures. The failure modes
considered in the mine scenario include four major items: tailings management facility; pipelines;
water collection and treatment; and road and culvert. These failure modes are included in the risk
assessments for a mine of this type and size, either qualitatively as is typically done in FMEA, or
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quantitatively. However, the range of failure modes will also consider many other types of failures
that can also occur during regular mine operations. These other types of failures may result in the full
spectrum of risks (from insignificant to very high) depending on site and mine life-cycle conditions.
Performing extensive analyses for the four major items implies that they could occur and that they
are the only failure modes that will be significant.
EPA RESPONSE: It is true that any of the failures analyzed could occur, as based on historic and
current knowledge of mining; however, a focus on these failures does not imply that they are the
only failures that will be significant. Because the number ofpotential failures is extremely large, it
is necessary to choose a representative set of failure scenarios. The revised assessment includes
more failure scenarios (e.g., diesel pipeline failure, quantitative water treatment failure, and
refined seepage scenarios) and explains why these particular failure scenarios were chosen.
Responses to the other parts of the current question (Are the probabilities and risks of failures
estimated appropriately? Is appropriate information from existing mines used to identify and estimate
types and specific failure risks? If not, which existing mines might be relevant for estimating
potential mining activities in the Bristol Bay watershed?) are further discussed in my responses to
other questions below.
EPA RESPONSE: No change suggested or required.
VAN ZYL RESPONSE: No further comments on Question 5.
EPA FINAL RESPONSE: No response required.
Phyllis K. Weber Scannell, Ph.D.
This section focuses on catastrophic failures; however, there are a number of non-catastrophic
failures that can occur at a mine site. Non-catastrophic failures include leakage of contaminated
water to ground or surface waters from PAG waste rock, the tailing storage facility, and exposed ore
surfaces, and from emergency discharge of untreated water from the TSF and ore spills from trucking
accidents. Such failures can be minimized or prevented with good site planning and monitoring. An
additional "failure" has been experienced at a mine in Alaska when the water elevation of the tailing
pond was sufficiently high to cause groundwater flow across a natural divide into an opposite
drainage.
EPA RESPONSE: Because the number ofpotential failures is extremely large, it is necessary to
choose a representative set of failure scenarios. The review draft contained a scenario in which
tailings leachate was not fully contained and reached a stream (Section 6.3 in the original draft).
The revised assessment document includes more failure scenarios (e.g., diesel pipeline failure,
truck accidents, quantitative water treatment failure, and refined seepage scenarios) in Chapters 8,
10 and 11 and explains why these particular failure scenarios were chosen.
WEBER SCANNELL RESPONSE: The reviewer is pleased that this section has been
expanded.
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The sections of the revised draft that address potential failures have been substantially revised
and expanded. The current draft Assessment is much improved and satisfies the concerns
initially expressed by this reviewer. In particular, I note the following sections as providing
important information:
Chapter 8, Section 8.1.3 provides an in-depth discussion of post-closure sources of
contamination, primarily from the pit lake. This section concludes: "In sum, failure to collect
and treat waters from the waste rock piles, TSFs, or mine pit could expose biota in the streams
draining the post-closure mine site to contaminated water." It is important to recognize that
these risks may extend in perpetuity.
Chapter 10 provides an expanded description of the transportation corridor. The explanation
of bridges and culverts has been clarified (Section 5.4.1 in the previous draft; section 10.3.2.1 in
the current draft).
Chapter 10, Chemical Contaminants in Stormwater Runoff (Section 10.3.3 in the current draft;
Section 5.4.2 in the previous draft) has been revised. The current revision provides more
thorough explanations of possible risks from storm water.
EPA FINAL RESPONSE: No response required.
Paul Whitney, Ph.D.
Sediment Transport. The failure analysis indicates a sediment transport study was beyond the scope
of the assessment. Not only is such a study important for fish resources, it is important for all
ecological resources, especially plant community succession along the stream and a delta into Bristol
Bay.
EPA RESPONSE: We agree that a sediment transport study is important to fully characterize the
watershed and potential impacts from large-scale mining. The scenarios indicate that runoff
eroding sediment from the site would be directed to sediment retention basins. Sediment runoff
from the road is considered in Chapter 10. The development and implementation of a model of
sediment (i.e., tailings) transport after the initial tailings outflow would require a research and
development effort that is beyond the scope of this assessment.
This might seem extreme, but the failure analysis indicates the Koktuli, Mulchatna, and Nushagak
Rivers would stabilize into a new channel after a failure and not continue to work their way across
the floodplain and eventually transport materials hundreds of miles down river. The Mount St.
Helens eruption, given as an analogy in the assessment (page 6-3), certainly moved sediment into the
Columbia River Channel, the Columbia River Estuary, and Pacific Ocean over a hundred miles
away. Copper concentrations in the Columbia River estuary as a result of the eruption ranged from 1
to 43 jag/L (Lee 1996). The upper limit of the range is approximately 20 times greater than the no-
effect benchmark listed in the assessment. The downstream consequences of changes in sediment
transport and water/sediment chemistry for fish and wildlife are sometimes very large, not
anticipated (see Peace Athabasca Delta response below), and costly to remediate. Solutions for the
Peace Athabasca Delta involving check dam construction may not be directly applicable to a tailings
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dam failure analysis in the assessment but may have some value short of dredging. I'm not sure how
it would work, but a mitigation effort (page 4-32, para 3, last sentence) using bulk tailings would
apparently be placed down gradient to catch tailings in the event of a failure. Is this a safety check
dam? It is possible that the assessment could be improved if this and other redundant efforts to
minimize risk could be discussed in more detail and considered in the failure analysis.
EPA RESPONSE: We have clarified this in Chapter 9 of the revised assessment. Our intent was to
describe a channel becoming reestablished in the deposited tailings and slowly reworking the
entire valley bottom, moving the fine material downstream We agree that tailings would be carried
downstream to Bristol Bay over the long term with adverse impact to waters. The mitigation
addressed in the comment, where a levee was created downstream to capture the flow of tailings,
was not our intent. We described a reclamation scenario where the tailings are dewatered and
sloped to eliminate the chances of mass failure of the impoundment. Mitigating impoundment
failure by creating a second dam downstream would greatly increase the mine footprint on salmon
habitat.
I agree with the assessment's statement on page 6-11 (6 lines down) that impacts of a tailings dam
failure to fish would extend down the mainstem Koktuli River and possibly further. If the Mount St.
Helens analogy is a good one, the impacts could reach Bristol Bay. Even if the Mount St. Helens
analogy is not a good one, I suspect sediments would continue to move down river as the river(s)
moved across their floodplains through time. I also agree with the assessment's statement that the
time to reach dilution approaching background would be very long, as the sediments in tributary
rivers to Bristol Bay will be continually reworked (page 6-25) and resuspended.
EPA RESPONSE: We agree with the commenter. No change suggested or required
As a terrestrial ecologist, I have always been impressed by the impact of Bennett Dam on sediment
transport in the Peace Athabasca Delta ecosystem over 600 miles away (Cordes 1975). The
assessment does mention the potential impact of toxics on the likelihood of plant community
succession on deposited tailings (page 6-10), but this causal pathway was not assessed. Given the
increases in metal concentrations in the Columbia River Estuary cited by Lee (1996) for the Mount
St. Helens eruption, an assessment of downstream sedimentation and changes in sediment chemistry
should be addressed. The likelihood that far reaching impacts of a failure could influence plant
succession and wildlife habitat quality is probably not anticipated but given the Mount St. Helens
analogy and the lessons learned from Bennett Dam, the likelihood of such impacts deserve more
attention.
EPA RESPONSE: This comment recommends expanding the scope of the assessment to include
direct effects on terrestrial plants and wildlife habitat. The scope was set during the planning and
problem formulation processes to encompass the expressed concerns of the Alaska Native
organizations that asked the Agency to address potential mining in the Bristol Bay watershed, as
well as the needs of the Agency's decision makers. This scoping process is in keeping with the
Guidelines for Ecological Risk Assessment (USEPA 1998). The commenter may be more familiar
with Environmental Impact Statements, which are full disclosure documents and therefore are
more broadly focused
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WHITNEY RESPONSE: The reasons for not including direct impacts on wildlife given here do
not align with statements provided by Natives that impacts on wildlife are more important than
impacts on salmon (page 5-77 in first draft). The reason(s) for not including wildlife should be
consistent. I can't help but wonder if the Alaska Native organizations are not interested in
direct impacts to wildlife. While living in Alaska I recall that a variety of birds and mammals
and their parts were are still are important for nutrition, warmth, adornment and trade. For
example ermine and short tailed weasels are used in a variety of ways on ceremonial dress.
EPA FINAL RESPONSE: Although it is clear that Alaska Native communities and other
organizations have concerns about direct effects on wildlife, their petitions to the USEPA stressed
the central importance of salmon.
Sediment Benchmarks. Once again, as a terrestrial ecologist with ecological risk assessment
experience, I know that sediment chemistry and determining toxic benchmarks for sediments is very
complex and subject to varied opinions. I admire the MacDonald et al. (2000) effort to reach
consensus on sediment benchmarks but I have three concerns. First, the consensus values listed in
MacDonald et al. (2000) are geometric means of values from several sources. The mean consensus
values likely do not equate to No Observed Effect Concentrations, which would probably be lower
than the mean values. Second, the lack of observed effects was sometimes for a "majority" of
sediment dwelling organisms, but not all (MacDonald et al. 2000, Table 1). Third, some of the
sources used for the mean values included interstitial water, but apparently not all (Table 1). I will
always remember Dr. John Stein (currently the acting director of NOAA's Northwest Fisheries
Science Center in Seattle) standing up at a workshop for the Columbia River Channel Deepening
Project. He had a small bottle of sediment and water in his hand and, while shaking it, he said
something to this effect: It's the pore water we are interested in. Considering that a proposed mine, at
some point, will be reviewed by NOAA, it seems appropriate to consult with NOAA regarding
benchmarks for all the species of sediment/pore water-dwelling organisms likely to occur in the
potentially effected watersheds addressed in the assessment.
EPA RESPONSE: We agree that pore water concentrations are generally useful predictors of
toxic effects of sediment, and sediment pore water toxicity is addressed in the assessment.
However, the MacDonald et al. (2000) benchmarks are also a useful line of evidence. NOAA has
been consulted during the development of this assessment. No change required.
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3.8 Charge Question 6
Does the assessment appropriately characterize risks to salmonid fish due to a potential
failure of water and leachate collection and treatment from the mine site? If not, what
suggestions do you have for improving this part of the assessment? Are significant
literature, reports, or data not referenced that would be useful to characterize these risks,
and if so what are they?
David A. Atkins, M.S.
Water treatment failures of varying scale occur at virtually every site that treats water, and mine sites
are no exception. The risk of failure of water treatment described in the assessment is useful as
background, but as the report states, the risk is highly uncertain. A non-catastrophic water treatment
system failure is fairly likely to occur at some point during the mine life, and, hence, requires a
detailed assessment. The treatment in the Assessment is cursory (less than one page). This type of
failure is much more likely than a TSF failure (which receives more than 20 pages of analysis), and
therefore requires a much more thorough treatment given the probability of occurrence and
likelihood of impact to salmon species.
EPA RESPONSE: The wastewater treatment failure scenario has been expanded and is now
detailed and quantified in Chapter 8 of the revised assessment. Additionally, the non-catastrophic
failures of seepage collection from the TSF and waste rock piles also have been included as
scenarios with new and refined analyses.
ATKINS RESPONSE: This response is adequate.
EPA FINAL RESPONSE: No response required.
The background water chemistry indicates mineral concentrations are very low. Therefore, water
treatment will be challenging if background conditions are to be met. Treatment will be especially
challenging given the sensitivity of the species of concern to concentrations of copper, for instance,
as well as the sensitivity to temperature that may be difficult to match in a water treatment system.
EPA RESPONSE: A mine would not necessarily have to match the low background
concentrations, but would at minimum be held to the water quality standards that protect the
existing and designated uses of the waterbodies where a discharge might occur. In the Bristol Bay
area, all waterbodies are protected for all uses and permit limitations would be derived to be
protective of the most stringent applicable Alaska Water Quality Standards (WOS). In addition, we
believe that compliance with the more recent Federal Water Quality Criterion for copper would be
necessary to protect aquatic life.
ATKINS RESPONSE: This response is adequate.
EPA FINAL RESPONSE: No response required.
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During mine operation, a lapse in treatment would likely be identified and addressed quickly. This
type of treatment failure is ephemeral and would likely have a short-term impact on the fishery,
depending on the time of year of occurrence. It is likely that any impacts to the fishery could recover
in subsequent years after the problem is fixed. The site will require water treatment long after
closure, possibly in perpetuity. This period is more problematic, as a water treatment failure could go
unnoticed for some time or the resources may not be available to correct it quickly, depending on
how long after closure the failure occurs and the stewardship of the treatment system.
EPA RESPONSE: A failure during operation would be corrected quickly only if it did not require
extensive repairs or the manufacture and import of replacement equipment. EPA agrees that water
collection and treatment failures after mine closure would be less likely to be corrected in a timely
manner. In addition, events after closure, such as filling of the pit, would affect water quantities
and qualities in ways that would affect treatment success. A discussion of this issue has been
added to Chapter 8 of the revised assessment. A discussion offinancial assurance has been added
in Box 4-3.
ATKINS RESPONSE: This response is adequate.
EPA FINAL RESPONSE: No response required.
Steve Buckley, M.S., CPG
Less than a page (4-39) is devoted to the failure of water and leachate collection and treatment. This
seems inadequate given it would be one of the main systems that could impact fish at the potential
mine site. In contrast, 20 pages are devoted to tailings dam failure (p.4-39 to 4-60).
EPA RESPONSE: The wastewater treatment failure scenario has been expanded and is now
detailed and quantified in Chapter 8 of the revised assessment.
BUCKLEY RESPONSE: This reorganization is helpful along with the additional information
on wastewater treatment failure scenarios.
EPA FINAL RESPONSE: No response required.
Courtney Carothers, Ph.D.
The report concludes that wastewater and leachate treatment and collection failures could expose
local streams to mildly to highly toxic water harmful to invertebrates and fish species. Depending on
the type of failures, these exposures could last from a period of hours to years. The report notes that
in the case of Red Dog Mine, Alaska, the water treatment system was inadequately designed, but
does not discuss why such a design was approved and allowed to be implemented, nor does it discuss
the likelihood of replicating such a design flaw in future mining scenarios.
EPA RESPONSE: The Red Dog Mine's treatment system was inadequately designed because the
amount of water to be treated was underestimated. Mine site hydrology is often difficult to predict
and treatment systems may fail despite the intent of mining companies and regulators.
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CAROTHERS RESPONSE: EPA response is sufficient.
EPA FINAL RESPONSE: No response required.
Dennis D. Dauble, Ph.D.
More information on local hydrology, including seasonal runoff patterns (e.g., peak flows) and
groundwater movement would be useful. I found no description of existing water quality
characteristics of potential receiving waters, except what is included in Table 5-17 of the main report.
Are these values (such as hardness, which moderates metal toxicity) consistent throughout the
watersheds, including downstream lakes? Other questions include: What volumes of leachates might
be collected and treated versus volumes not captured and subsequently released downstream? Is
copper the only constituent of concern to aquatic animals? Are there processing chemicals that would
also be toxic?
EPA RESPONSE: Monthly flow patterns for area streams are now presented in Chapter 7. The
three streams described in Table 7-17 are the three potential receiving waters for any site effluents.
The water balance, including leachate volumes, is now described in the assessment (Chapter 6).
Copper is the primary contaminant of concern. Others are described in the new Section 6.4.2.3
and discussed in Chapters 8 and 11.
DAUBLE RESPONSE: I noted hardness values were now included in Chapter 3. Also, several
new maps (Figures 6-1 to 6-3 and 6-8 to 6-11) provide sufficient detail of regional and local
hydrology that flow paths for receiving waters are clearly understandable.
EPA FINAL RESPONSE: No response required.
The assessment should also consider and discuss relative risk to aquatic ecosystems from
downstream transport of sediment-bound metals to Iliamna Lake, if deemed probable.
EPA RESPONSE: Although metals in aqueous emissions would partition to sediment, and the
sediment would mobilize during high flows and eventually reach the lake, this route is not judged
to be significant. Toxicity is caused by dissolved metals, and concentrations from release of metals
from transported sediment to lake water are likely to be minor.
DAUBLE RESPONSE: I defer to EPA's judgment on this topic.
EPA FINAL RESPONSE: No response required.
Gordon H. Reeves, Ph.D.
The report focused primarily on the lethal effects of the contamination from leachate and water
treatment and collection failures. However, could there be ecological consequences to fish and
invertebrates that are not directly lethal but that could have ecological consequences over the long
term? I suggest that this needs to be considered more fully in this assessment.
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EPA RESPONSE: The report addresses both acute lethal effects and chronic lethal and nonlethal
toxic effects to both fish and the invertebrates on which they feed. It is highlighted in the text when
estimated concentrations are sufficient to cause acute lethality. Such effects are important not only
because they are severe but also because they could occur during episodic exposures.
Sockeye salmon are most abundant salmon in Bristol Bay and a primary species of focus in this
analysis. The direct impacts of mine and mine-related activities have been considered but there
appears to be a lack of consideration of the impact on zooplankton, the food source for sockeye. If
this were a deliberate omission, then a statement about why it was omitted is required. The revision
should include this if it was an oversight.
EPA RESPONSE: Any effluents would be released to the streams draining the site. In those
ecosystems, zooplankton are rare and the primary food organisms for fish are benthic
invertebrates. However, the toxicological data used to assess effects on invertebrates are
dominated by planktonic crustaceans. Therefore, if toxic concentrations of metals reach Iliamna
or other lakes, the toxicity assessment would actually be more relevant to the plankton that occur
there than to the insects in the receiving streams. Hence, the numerous references to effects on
aquatic invertebrates are relevant to zooplankton and no new analyses are needed.
Charles W. Slaughter, Ph.D.
No. Text suggests that a monitoring well field downslope from the TSF (and presumably from all
hypothetical TSFs) would detect seepage; such seepage would then be intercepted and either returned
to the TSF or "treated and released to the stream channel." Either action presupposes adequacy of
monitoring seepage and subsurface flow (both spatially and temporally); returning such water to the
stream further presupposes fully adequate treatment to meet both regulatory and aquatic biota
requirements for water quality and flow regime.
EPA RESPONSE: The water treatment and leachate capture discussions have been expanded and
are now detailed and quantified in Chapter 8 of the revised assessment.
SLAUGHTER RESPONSE: The extensive revisions and added analysis of Chapter 8 are very
helpful. Qualifications and cautions in the text are also appropriate - such as "Even a small
number of flowpaths with higher than expected hydraulic conductivity could significantly
affect the direction and quantity of flow" (p. 8-11); "Wells would not catch all flows from the
mine site given its geological complexity and the permeability of surficial layers" (p. 8-12); the
last sentence in Box 8.1 (p. 8-20); "...although post-closure water treatment failures would be
less consequential, they also would be less likely to be promptly detected and corrected" (p. 8-
21); "...it is much too soon to know whether mines that are permitted for perpetual water
collection and treatment....can actually carry out those functions in perpetuity" (p. 8-22);
"...releases of water contaminated beyond permit limits would be likely over the life of any
mine at the Pebble deposit"(p. 8-22).
EPA FINAL RESPONSE: No response required.
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Assumptions are very generalized and optimistic: "assuming no water collection and treatment
failures" and "excess captured water would be treated... and discharged to nearby streams..." - this
assumes both "no failures" over the life of the operation, and that such treated "excess captured
water" could be successfully treated before release to fully meet both regulatory water quality criteria
and the possibly more sensitive biological requirements of individual invertebrates and fish stocks
(Appendices A & B).
EPA RESPONSE: Water management (mitigation) measures are more clearly described and
discussed in Section 6.1.2.5 of the revised assessment, and in sub-sections for the mine
components in the scenarios. Our intention for the "no-failure" scenario was to identify and
evaluate the unavoidable environmental effects if all systems and mitigation measures operated
perfectly, and to separate those effects from a scenario where systems periodically failed. However,
the "no failure" scenario is no longer included. The purpose of the assessment is to describe the
potential adverse environmental effects that could exist even with appropriate and effective site
mitigation measures. The assessment is not intended to duplicate or replace a regulatory process,
which is where required permit discharge limits for water quality would be determined.
SLAUGHTER RESPONSE: Agree that the brief discussion in Section 6.1.2.5, in concert with
Chapter 8, more comprehensively treats water management and hydrologic issues. I still
suggest that current or future regulatory water quality criteria may not be adequate to meet
and sustain the possibly more sensitive biological requirements of aquatic invertebrates and
fish stocks.
EPA FINAL RESPONSE: No response required.
John D. Stednick, Ph.D.
The TSF is designed to hold the tailings under water to minimize the oxidation of pyritic materials
and limit ARD or AMD production. The TSF will be underlain by hypalon to capture leakage waters.
There is the possibility of failure to collect waters from the TSF—either surface runoff or leakage
with or without storm (precipitation) events. There is also the possibility of failure of the treatment
plant to treat the wastewater. Such treatment systems in Colorado usually have a bypass pond to
temporarily hold waters for later pump back and treatment as a result of power failure, plant going
off-line, storm events, or plant maintenance.
EPA RESPONSE: The May 2012 draft assessment contained a scenario in which tailings leachate
was not fully contained and reached a stream (Section 6.3); however, this has been refined with
new data in the April 2013 draft for seepage from the TSF and waste rock piles that escapes
capture from the mitigation measures (Chapter 8). Additionally, the scenario presents a suggested
treatment option for mining influenced water and settling ponds for stormwater runoff. A
wastewater treatment plant failure scenario in the April 2013 draft of the assessment assumes
emergency storage capacity has been exceeded or the bypass system fails.
The waters in the study area have very low buffering capacity; metal toxicity would occur at low
concentrations and dilution of metals would require time and space. The maximum index counts on
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page 6-39 are confusing and not well related to the risk characterization. Copper was used as an
example metal, but other metals are also toxic and further characterization of the waste rock can be
presented. Further analysis of a water and leachate collection failure can be made over time: the
effects of dilution flows over the various months with low flows, or when adult salmon are present in
the stream as opposed to juveniles - or, when juveniles are emerging. The toxicity quantification is
difficult and appears more of an academic exercise here, rather than site specific.
EPA RESPONSE: Undiluted leachate concentrations are used to calculate the hazard quotients
(we assume that is what the reviewer means by "maximum index counts"), to screen the
constituents for contaminants of concern, and because the State ofAlaska does not allow mixing
zones in anadromous streams. However, dilution was considered in the failure scenarios for waste
rock leachates and tailings leachates. Copper was emphasized because it is by far the most toxic
metal relative to concentrations in rock, tailings and concentrate leachates. Site specific water
chemistry was used to estimate the toxicological benchmarks for copper and for metals with
hardness-dependent toxicity. More detailed analyses of dilution are included in Chapter 8 of the
revised assessment.
Leachate collection from the tailings area is only briefly described. What are the State of Alaska
standards for collection and treatment? What are the potential effects of not collecting or treating the
tailings leachate waters? Compare the detail and length of leachate discussion to the TSF failure
discussion (see earlier comments).
EPA RESPONSE: There are no specific AK State standards for collection and treatment of
tailings leachate, but any discharge to waters of the United States requires a Clean Water Act
Section 402 (CWA § 402) permit. In Alaska, the Department of Environmental Conservation
issues these permits under the Alaska Pollutant Discharge Elimination System program Such
permits would contain effluent limitations that are protective of the State WQS. The original draft
assessment contained a scenario in which tailings leachate was not fully contained and reached a
stream (Section 6.3 of the May 2012 draft); however, this has been refined with new data in the
revision (Chapter 8) for seepage from the TSF and waste rock piles that escapes capture from the
mitigation measures.
Given the hydrologic connection between surface and groundwaters, what effect will interception of
all waters on the TSF do to the surrounding wetlands and groundwater levels? Again the lack of a
water balance does not let the reader determine if this water interception is significant or will have
significant resource effects.
EPA RESPONSE: The water balance presented in the revised assessment quantifies the amount
of water captured at each TSF under each scenario. The assessment also presents the percentage
change in streamflow at existing gages in the North Fork Koktuli, the South Fork Koktuli, and the
Upper Talarik.
The water balance presented in the assessment looks at the overall amount of water dedicated to
consumptive uses, which therefore would no longer be available to contribute to groundwater
recharge or stream flow. Furthermore, the assessment attempts to quantify the annual amount of
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and percentage increase or decrease in streamflow for individual stream reaches. These stream
flow results are presented in Chapter 7 of the revised assessment.
Our analysis does not attempt to explicitly calculate groundwater levels or drawdown except within
the cone of depression around the mine pit. Our analysis assumes that all precipitation that falls
outside the actual mine footprint (i.e., the physically disturbed areas) would continue to contribute
to groundwater recharge and stream flow, although the exact flow patterns would change due to
collection of surface runoff and stream diversions. Areas within the footprint would most likely see
some decrease in the groundwater levels due to the collection, management, and possible
treatment of surface runoff, with some potential increases downstream of the points of water
release from the wastewater treatment plant. Overall, the cumulative reduction in streamflow
would be approximately equal to the amount of water retained on the site as tailings pore water.
Most, if not all of these failures are the result of human error. What safeguards will be in place?
What are the best mining practices to minimize human error?
EPA RESPONSE: The mitigation measures proposed within the mine scenarios are those that
could reasonably be expected to be proposed for a real mine (they are a subset of options presented
in Appendix I), all of which were presented as appropriate for the Pebble deposit in Ghaffari et al.
(2011). We assume that these types of measures would be applied throughout a mine as it is
constructed, operated, closed, and maintained through post-closure. Because the possibility for
human error is inherent in any activity in which a human is involved, accidents and failures
happen. Human error-caused accidents and failures are minimized when the humans involved
follow careful and responsible management of the mining site. No change suggested or required
Roy A. Stein, Ph.D.
Groundwater Connectivity and TSF Construction I. Extensive connectivity between surface
water and groundwater means that any failure will allow contaminated waters to flow quickly to
areas of importance for salmon. And, indeed how does one build a tailings pond (coarse textured
glacial drift in the Pebble Mine area) with this much permeability? Why would one only line the
tailings dam; shouldn't the entire Tailings Storage Facility be lined? Would not this be "Best
Practice"?
EPA RESPONSE: Our estimates of the expected leakage from the full TSFs range from about 2 to
6 mVmin. If a mine at the Pebble deposit goes forward, the design of the TSFs should include a
more thorough flow analysis that would calculate the expected rate offlow and associated flow
paths from the TSFs. If the calculated leakage rates were unsatisfactory from an environmental,
operational, or economic perspective, the designer could incorporate other design elements (e.g., a
liner) to reduce the expected leakage rate. Full liners beneath TSFs are not always used; however,
there is a growing requirement to use liners to minimize risks of groundwater contamination, with
new mines in Australia being required to justify why one wouldn't be required (Commonwealth of
Australia 2007). Liners are not required in the US. Whether something is "best" depends on the
specifics of the site. The mitigation measures proposed within the mine scenarios are those that
could reasonably be expected to be proposed for a real mine (they are a subset of options presented
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in Appendix I), all of which were presented as appropriate for the Pebble deposit in Ghaffari et al.
(2011). Evaluation of different mitigation measures to determine if lining the facility would be
"best" for this site would be part of the regulatory process and thus is outside the scope of this
assessment.
Groundwater Connectivity and TSF Construction II: A water-impermeable barrier will be
installed only on the interior dam face and nowhere else. To prevent communication between these
facilities and the groundwater, is it feasible to map groundwater inputs before the facility is filled,
place barriers over these areas, and thereby reduce influx of groundwater into the facility and perhaps
prevent movement of toxic water into the groundwater? I make this point with some hesitation,
given the point made on page 5-29:
"Projecting specific mining-associated changes to groundwater and surface water
interactions in the mine area is not feasible at this time."
EPA RESPONSE: See response to previous comment.
Failure of Leachate and Water Collections. See my comments under Question 12 below. In
addition, I see this as a huge undertaking for which monitoring and response (mitigation) are clearly
as important as the actual plan to capture these wastes.
EPA RESPONSE: We agree with this comment. No change suggested or required
William A. Stubblefield, Ph.D.
The risk assessment attempts to consider the effects of metal discharges for water and leachate from
the mine site. This assessment is based on metals concentrations measured in potentially "similar"
mine waters from other sites; concentrations of metals are likely to differ based on source material
and operational differences. The effects concentrations used in the evaluation are based on US EPA
ambient water quality criteria (AWQC) for metals, and this approach is appropriate for "screening
level" evaluations. It should be noted that exceedence of an AWQC does not portend the occurrence
of adverse effects. Ambient water quality criteria are derived in such a way that they are intended to
represent "safe concentrations." In other words, if environmental concentrations remain below the
AWQC, it is assumed that unacceptable adverse effects will not occur; exceedence of an AWQC
suggests that adverse effects may occur to some species, but that this must be evaluated more closely.
Salmonid species are not the most sensitive organisms in the copper AWQC species sensitivity
distribution (SSD); therefore, direct effects on salmon are even less likely at concentrations in the
range of the AWQC.
EPA RESPONSE: Effluents or ambient waters from mines at other sites were not used The
leachate concentrations used (except for the product concentrate leachate) are from available
results of material leaching tests from the Pebble deposit. Otherwise, we agree with these
comments. The assessment used criteria for screening, but then examines the toxicity data more
closely, including field data to determine potential effects (e.g., aversion, sensory inhibition,
mortality and reduced reproductive success of salmonid fish). The greater sensitivity of aquatic
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insects was described in the original draft of the assessment and is further highlighted in the
revised assessment. The protectiveness of the copper criterion is considered in both the original
and revised assessments.
STUBBLEFIELD RESPONSE: Section 8.2.2.1 provides a good discussion of the copper
standard used in conducting the Bristol Bay assessment. It describes the existing state
standard, the incorporation of the biotic ligand model calculations and its effect on site-specific
copper criteria, the importance of "nonstandard" endpoints (e.g., olfactory concerns), and the
concerns that the US EPA has about the "protectiveness" of the existing criteria. The authors
identify a group of recent scientific publications that have "identified effects on aquatic insect
populations and invertebrate communities at concentrations below water quality criteria for
the dominant metals (cadmium copper and zinc)." This is an intriguing finding that may run
counter to previous assumptions regarding the protection afforded by water quality criteria. It
could also have far-reaching consequences for water quality criteria and their derivation
procedures. Field-based assessments are frequently difficult to evaluate due to confounding
factors. Because of this alternative approaches, such as mesocosms, are frequently used to
assess community or population level concerns under more "controlled" environmental
conditions. A number of mesocosm studies have been conducted with copper in recent years
and these studies should be evaluated and considered in assessing the adequacy of the copper
criteria.
One statement contained in Chapter 8, Section 8.2.2.1 suggests that the EPA may believe that
the AWQC for copper may be significantly underprotective. That statement indicates that:
"Based on the literature cited above and the author's experience, resolution of this uncertainty
by additional research and testing is likely to lower the chronic criterion by approximately a
factor of 2 and not as much as a factor of 10."
This is a concerning statement especially when one considers the ramifications if this is in fact
correct. For example, the table below presents the BLM copper criteria based on the mean
water chemistries in the mine scenario watersheds (taken from Table 8.11) with consideration
of a 2-10 fold "uncertainty" factor. These values are compared to background copper
concentrations in the same river segments (taken from Table 8.19). All values are in (ig/L.
Stream
CMC
CMC
(2-10 factor)
ccc
CCC
(2-10 factor)
Background
range
South Fork Koktuli River
2.4
1.2-0.24
1.5
0.75-0.15
0.42-2.4
North Fork Koktuli River
1.7
0.85-0.17
1.1
0.55-0.11
0.31-0.61
Upper Talarik Creek
2.7
1.35-0.27
1.7
0.85-0.17
0.21-0.5
This assessment suggests that if the BLM chronic criteria concentrations are "under-
protective" by the suggested 2-10 factor, a significant portion of the streams would be in
violation of the copper criteria based on only background concentrations.
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EPA FINAL RESPONSE: The factors of 2 to 10 were suggested by the cited authors, not EPA.
They have been deleted to avoid misinterpretation.
It is interesting to note that the risk assessment document states that copper is one of the "best-
supported criteria. However, it is always possible that it would not be protective in particular cases
due to unstudied conditions or responses." Further, the document goes on to suggest that organisms
such as mayflies etc. are important to the aquatic ecosystem but are not considered in the copper
AWQC and therefore may not be sufficiently protective. It also suggests that because an acute-
chronic ratio approach is employed to correct the final acute value to obtain a final chronic value,
there may be increased uncertainty associated with the protectiveness of the chronic criterion. This
appears to be an area where EPA might benefit by conducting research (either alone or in concert
with industry) to reduce uncertainty in the criteria to an acceptable level. In addition, additional
chronic toxicity data may be available from research conducted in response to the European REACH
regulations and consideration of this research may reduce the level of uncertainty in the criteria.
Bioavailability correction via the BLM approach is only considered for copper in the risk assessment;
biotic ligand models have been developed for a number of metals (e.g., zinc, nickel) and these should
be considered in the assessment as well. Finally, the assessment approach seems to use a sum TU-
based approach for assessing "metals mixture" impacts. This is based on an assumption of additive
interactions among the metals. Although this is probably the best assumption in going forward,
limited data are available to support this approach.
EPA RESPONSE: We have examined the EU's 2008 Voluntary Risk Assessment of Copper (the
relevant REACH document). Although the authors could derive a chronic species sensitivity
distribution, that is because the way that they include and aggregate data differs from EPA's
method. They apparently did not generate new test data for the assessment. In particular, they
have no data for sensitive aquatic insects, so the EU assessment does not resolve that problem The
BLM was used for copper because it is the contaminant of greatest concern and because the
copper BLM has been approved by the EPA's Office of Water. Other metals with BLMs, such as
zinc and nickel, occur at lower levels in leachates relative to their toxicities, so BLM modeling was
not justified.
STUBBLEFIELD RESPONSE: The US EPA authors are to be commended for taking the time
to review the EU's voluntary risk assessment of copper. This document represents the most
recent evaluation of copper environmental toxicity that this reviewer is aware of. Additional
data that were generated as part of the copper industry environmental research program are
reflected in this document (e.g., data for freshwater mussels). Differences do exist between the
US EPA and EU approach for endpoint assessment (EC10 vs EC20), aggregating data, and
statistically deriving "thresholds." However, the data are available to permit threshold
calculation using either method. EPA is to be commended for the use of the copper BLM in
conducting this assessment; it represents the current state-of-the-science and provides the most
accurate method for deriving thresholds considering site-specific physicochemical parameters.
BLMs for other metals such as zinc, nickel, and cobalt exist in the peer-reviewed scientific
literature, but have not yet gained regulatory acceptance by the EPA Office of Water. It is
anticipated that this will come with time. EPA did not consider the BLMs for these other
"lessor" metals because of their "lower levels in leachates relative to their toxicities." This may
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be a reasonable approach; however, when using an additivity-based approach (LTU) when
assessing metal mixtures, it may be advisable to "correct" for bioavailability in even the
"lesser" metals, when possible.
EPA FINAL RESPONSE: Using an additivity model required equivalent benchmarks for each of
the constituents. The BLMs for metals other than copper do not provide values equivalent to acute
and chronic water quality criteria.
Areas where additional research would be beneficial include:
• Mixtures: Information regarding the potential interactive effects of multiple metal exposures
would be useful and would reduce assessment uncertainty.
• Species sensitivity concerns: there is extremely limited data (esp. chronic datat) on all of the
salmon species of concern in Bristol Bay
• Additional data, especially chronic toxicity data and data for additional metals for which no
water quality criteria exists, would be extremely helpful.
EPA RESPONSE: We agree that these are good research topics. No change is suggested or
required.
STUBBLEFIELD RESPONSE: To the extent possible, EPA may want to consider conducting
these research programs or funding others to do so. Also, based on the comments/revisions in
the Bristol Bay assessment there may be concern that the US EPA's current ambient water
quality criteria for copper, and perhaps other substances, do not adequately address potential
effects to "sensitive" insect species (e.g., Ephemeroptera, Plecoptera or Trichoptera orders).
Currently no standardized (i.e., OECD, ASTM or EPA) laboratory test methodologies exist for
conducting chronic toxicity test with EPT species. EPA may want to develop methods that
could be used to assess toxicity to these organisms.
EPA FINAL RESPONSE: EPA and USGS are both working on test protocols for mayflies
(Ephemeroptera).
Dirk van Zyl, Ph.D., P.E.
The EPA Assessment does not identify or appropriately characterize the risks to salmonid fish due to
a potential failure of water and leachate collection and treatment from the mine site. It only estimates
the likelihoods of occurrence and the consequences. See discussion under Question 4 above
regarding suggestions for improving estimation and expression of the magnitude of risks to salmonid
fish due to potential failure of water and leachate collection and treatment from the mine site.
EPA RESPONSE: We believe that the likelihood of an occurrence and its consequences constitute
an appropriate and generally accepted definition of risk. We have estimated those to the extent that
existing information allows. We have added to the discussion of leachate contamination, including
estimation of the magnitude of leachate escaping the collection system and entering surface waters
(Chapter 8).
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Water collection and treatment failure likelihood. An estimate is presented for the amount of
seepage that may flow from the TSF. Similar estimates are not presented for the waste rock piles.
The effects of the effective exclusion of oxygen from the saturated or partially saturated tailings
should be considered in developing an estimate of the water quality of the resulting seepage. It may
be an important factor in reducing the oxidation of sulfide minerals remaining in the interior of the
TSF. This same effect could also mitigate the release of poor water quality in the long-term following
closure. The precipitation on the site may be sufficient to effectively retain a suction saturated profile
in parts of the TSF.
EPA RESPONSE: The revised assessment presents an estimate of the amount of seepage from the
waste rock piles (Table 6-3). The water quality of the leachate from the TSF was modeled with the
concentrations reported from the tailings humidity cell tests. The reported copper concentration of
0.00533 mg/l is lower than some of the reported groundwater concentrations, and is the same
order of magnitude as the highest reported stream concentration of 0.0013 mg/l. The TSF at
closure was modeled with free standing water at the surface and with downward flow with an
estimated gradient between 0.07 and 0.12.
Water collection and treatment failure consequences. Water collection and treatment is being
done at a number of mines in North America. Past experience at the Red Dog mine is quoted;
however, there are many other examples that could have been examined. An important example is
that of the Equity Silver Mine in British Columbia (Aziz and Meints, 2012): "Acid Rock Drainage
(ARD) was discovered at the Equity Silver Mine in the interior of British Columbia in 1981. The
latest water treatment plant was installed in 2003, 9 years after the mine closed in 1994, and is the
fourth successive treatment plant for the site that has treated ARD for a period of over 30 years.
Discharge water quality was maintained since 1991 except during two high flows associated with
freshet conditions in 1997 and 2002. ARD collection and treatment system upgrades were installed
after 2002 and these have performed well through three large freshet conditions in 2007, 2011 and
2012. The timeframe for treatment is perpetuity and financial assurance is in place for a total amount
of $56,291 million through a long-term security bond (letter of credit) with the BC Provincial
Regulatory Authority. The security bond is reviewed by stakeholders every 5 year". Collection and
treatment at Equity Silver indicates that companies are committing to long-term water treatment of
ARD and that regulatory frameworks are in place to protect water quality in downstream streams and
rivers. It is recommended that EPA perform a more thorough review of other sites where water
treatment occurs to better characterize this failure mode.
EPA RESPONSE: We have been unable to obtain a copy of the cited report. The 2010
Sustainability Report, which is available, does not contain these specifics. This mine apparently
has begun perpetual water treatment. A comprehensive review of mine sites with water treatment
systems is beyond the scope of this assessment.
VAN ZYL RESPONSE: No further comments on Question 6.
EPA FINAL RESPONSE: No response required.
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Phyllis K. Weber Scannell, Ph.D.
This section of the report provides an in-depth discussion of possible sources and fates of
contaminated water. Chapter 6.3 discusses possible adverse effects from early mine closure or
prematurely shutting down a water treatment system. These issues highlight the need for a mine plan
that includes concurrent reclamation, sufficient bonding to conduct reclamation in the event of an
early shut down, and plans and specifications for collection and bypass of clean water and collection
and diversion to a water treatment system of contaminated water.
EPA RESPONSE: We agree with this comment. No change suggested or required.
WEBER SCANNELL RESPONSE: The reviewer is satisfied.
The reviewer agrees that no changes are needed to the Assessment. The reviewer notes
information in the revised assessment that supports the need for a rigorous review and
permitting process (Box 4.2) and financial assurance (Box 4.3) and references to the Red Dog
Mine as required perpetual treatment. This additional information addresses the concerns
raised by the reviewer in her initial comments.
EPA FINAL RESPONSE: No response required.
The Risk Characterization (Section 6.3.3) discusses possible contaminant loads to downstream
waters. As stated in this section, it "serves to indicate the large potential risk from improperly
managed waste rock leachate." This statement highlights the need for an in-depth mine plan with
sufficient monitoring and fail-safe provisions. An emergency discharge of untreated waters from a
tailings storage facility could be made to a collection pond for later treatment or the tailings pond
could be engineered to accommodate a higher flood event so the likelihood of overtopping is
minimized.
EPA RESPONSE: The waste rock leachate scenario referenced by the conmienter has been
eliminated and replaced with a more detailed and realistic scenario for waste rock leachate
collection and treatment (Chapter 8).
WEBER SCANNELL RESPONSE: The reviewer is satisfied that this issue has been addressed.
The additional information in Chapter 8 satisfies the concerns initially raised by the reviewer.
EPA FINAL RESPONSE: No response required.
Section 6.3.3 (Risk Characterization) states "Alternatively, water collection and treatment failure
could be a result of an inadequately designed water treatment system which could result in the
release of inadequately treated water as at the Red Dog Mine, Alaska (Ott and Scannell 1994,
USEPA 1998, 2008). In that case, the failure could continue for years until a new or upgraded
treatment system is designed and constructed." This statement is misleading and overly simplistic;
the water treatment system at the Red Dog Mine was designed to treat the predicted flows. However,
the stream bypass and collection systems were constructed in 1991 to intercept seepage waters. The
additional water that was collected and treated dictated construction of a second water treatment
system in 1992. Sand filters were added in 1993 to remove fine particulate Zn. The issue was not
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that the water treatment was inadequate, but that the pre-mining hydrologic data was insufficient and
that state, federal, and mine officials lacked experience in mine construction on permafrost soils.
EPA RESPONSE: The water treatment failure at Red Dog was, as the comnienter describes, the
result of an unintended failure to design a plant that was adequate for the mine and site. The
passage has been expanded to clarify the nature of the failure.
WEBER SCANNELL RESPONSE: The reviewer is satisfied that this issue has been addressed.
The description of water treatment failure at Red Dog (Chapter 8) is sufficiently detailed and
accurate for the goals of this Assessment. The reviewer is satisfied that the initial comment has
been addressed.
EPA FINAL RESPONSE: No response required.
Overall, the discussions of risks to salmonid fish due to a potential failure of water and leachate
collection and treatment from the mine site highlight the need for more comprehensive information
on groundwater, including delineating flow pathways, depth to surface, and water volumes.
Additional information is needed on water collection, storage, and treatment at future mine facilities.
EPA RESPONSE: Discussions of wastewater collection and treatment have been considerably
expanded in Chapter 8.
WEBER SCANNELL RESPONSE: The reviewer is satisfied that this issue has been addressed.
The discussions of wastewater collection and treatment contained in Chapter 8 of the revised
Assessment are a valuable addition to the document. The initial concerns expressed by the
reviewer have been addressed.
EPA FINAL RESPONSE: No response required.
Paul Whitney, Ph.D.
No comment on this question.
3.9 Charge Question 7
Does the assessment appropriately characterize risks to salmonidfish due to culvert
failures along the transportation corridor? If not, what suggestions do you have for
improving this part of the assessment? Are significant literature, reports, or data not
referenced that would be useful to characterize these risks, and if so what are they?
David A. Atkins, M.S.
The description of culvert failure is necessarily general because there are currently no designs. The
general data on culvert failures presented for the types of culverts described in the references cited
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(principally for forest and range land) indicate a high probability of failure (30-66% failure rate). It is
probable, however, that the transportation corridor for the project would be constructed to a higher
standard than most of the roads included in these papers. It would be helpful to know if similar data
are available for highly engineered roads of the type likely to be built for the project.
EPA RESPONSE: The assessment assumes modern mining technology and operations. We did
not find information explicitly from highly engineered roads, but to the extent possible we used
recent literature from representative environments. The failure frequencies cited in the revised
assessment are from modern roads and are not restricted to forest or rangeland roads.
Information on current design standards is now included in text boxes throughout Chapter 10.
ATKINS RESPONSE: This response is adequate.
EPA FINAL RESPONSE: No response required.
Steve Buckley, M.S., CPG
The references provided in this section emphasize culvert failures in the Pacific Northwest and
Tongass National Forest. The streams and culverts in these regions are heavily influenced by large
woody debris loading. It would be more appropriate to classify the various potential stream crossings
by watershed and the amount of large woody debris available to be recruited to the stream and
influence culvert blockage.
EPA RESPONSE: Many of the references in the assessment relate to the Pacific Northwest,
because much work on culverts and potential impacts on salmon have been performed there.
Flanders et al. (2000) has been deleted in the revised assessment. The failure frequencies cited in
the revised assessment are from the best available literature concerning modern roads, and are not
restricted to forest roads.
BUCKLEY RESPONSE: The bulk of the information presented on culvert failure research
relates to roads in forested watersheds and these may not be as applicable to the proposed
transportation corridor. The additional information provided on the character of each
potential stream crossing is more useful for the assessment of the potential impacts of the mine
road to fish passage.
EPA FINAL RESPONSE: Text has been added further explaining the difference between forested
and non-forested riparian vegetation for culvert functioning.
Courtney Carothers, Ph.D.
Culvert failures due to blockage and erosion are noted to be common and are likely to occur in this
scenario. Culvert failures would prevent the movement of fish, which could eliminate a year class
from blocked stream systems and fragment upstream and downstream populations, increasing
likelihood of localized population depletions and extinctions. Monitoring and maintenance of
culverts can be expected to decrease after mine operation, increasing the risks of these failures. The
report appears to appropriately characterize risks to salmonid fish due to culvert failures along the
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transportation corridor, although I have no particular expertise with which to evaluate this
assessment.
EPA RESPONSE: No change suggested or required.
CAROTHERS RESPONSE: EPA response is sufficient.
EPA FINAL RESPONSE: No response required.
Dennis D. Dauble, Ph.D.
Mitigation practices, such as new culvert design, was well described, as was bridging of roadways
and porous fills to mitigate risks due to culvert failure along the transportation corridor. This
assessment also included appropriate risk characterization for both the no-failure and failure
scenarios. There should be literature available from the Washington State Department of
Transportation on fish passage relative to culvert placement and design. Otherwise, I have no
suggestions for improvement.
EPA RESPONSE: We have examined literature on fish passage relative to culverts from the
Washington State Department of Transportation. Culvert failure frequencies from their 2012
paper, in which approximately 62% of culverts were identified as total or partial barriers, were not
used in the assessment because we could not determine the age of examined roads.
DAUBLE RESPONSE: I had no serious issues with the assessment of potential culvert failures.
However, I can't help but believe that data on timing of road construction for WA State DOT
projects would be available. In terms of aquatic invasive species (Section 10.3.6.1), no plausible
vector was described for their transport. What types of construction equipment or mining
infrastructure would expected to lead to the introduction of aquatic invasive species? Typical
examples would be recreational vehicles, such as boats, but that does not seem applicable.
Suggest you introduce the topic but tone down the risk relative to mining operations.
EPA FINAL RESPONSE: The section on invasive species emphasizes riparian terrestrial species
because they are most likely to be carried by construction equipment and by shipments of
materials. The discussion of aquatic invasive species has been edited to downplay the probability
of occurrence relative to terrestrial species, to clarify that the most likely vector is construction
equipment that has been used in stream crossings, and to explain that the concern is based on
large scale issues from the introduction of noxious invasive species.
Gordon H. Reeves, Ph.D.
The literature review of culverts and their potential impacts on fish and fish habitat is very thorough
and the presentation of results is accurate. However, most of the cited material is from studies done
in areas outside of Bristol Bay and the direct applicability of results is problematic. This should be
done in the revision.
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EPA RESPONSE: Because the proposed mining would take place in an undeveloped area, nuich
of the literature is necessarily from areas outside of Bristol Bay. However, to the extent possible we
used examples from representative environments, and applied the results to the proposed mine.
I think that there are potential mitigation measures that were not presented. The primary one, besides
the use of bridges, as suggested in the report, is making all culverts be arch culverts. These culverts
make use of the stream bottom, which reduces the potential for the culverts to become perched and
impede upstream movement, and are less likely to change the gradient than other culvert types. All
culverts could, as recommended in the report, be at least one bank width, which is larger than
required by the state of Alaska. This would minimize the possibility of plugging with debris.
EPA RESPONSE: A number of culvert types (e.g., arch culverts) may be used on the proposed
transportation corridor; it is not in EPA's purview to suggest which ones should be used
However, culvert design approaches specified in the Memorandum of Agreement between the
Alaska Department of Fish and Game and the Alaska Department of Transportation and Public
Facilities (ADF&G and ADOT 2001) are described in Box 10-2 of the revised assessment.
The review of potential road impacts lacked two possible consequences. One is that roads could be
corridors for the introduction of invasive species, plants and animals. The consequences of the
successful establishment of non-native species could have critical ecological impacts on native
species and the ecosystem. The second consequence is that a road will allow greater access to
streams where access was previously limited. Fish populations could be more easily and intensively
harvested in sport and subsistence fisheries, which adds additional stresses to the populations. Lee et
al. (1997. Assessment of the condition of aquatic ecosystems in the Interior Columbia River basin.
Chapter 4. Eastside Ecosystem Management Project. PNW-GTR-405. Portland, OR: U.S.
Department of Agriculture, Forest Service, Pacific Northwest Research Station.) found a direct
relation between road access and the status of salmonid populations in the Columbia Basin.
EPA RESPONSE: We agree with the commenter that roads could be corridors for the
introduction of invasive species. The potential impacts of invasive species as a result of
construction and operation of the proposed transportation corridor are discussed in Section 10.3.6
in the revised assessment. With respect to stream access, EPA assumes that the proposed road
would be closed to the public during mining operations but potentially could become a public road
after mining operations cease. If that were the case, there would be greater access to streams and
fish populations. However, the potentially important impact to fish would likely occur from
secondary (induced) development, or development resulting from the introduction of industry,
roads and infrastructure associated with mining. This is briefly discussed in Section 13.3 in the
revised assessment. Improved accessibility would increase hunting and fishing pressure, as well as
competition with existing subsistence users.
Charles W. Slaughter, Ph.D.
No. The Assessment does not adequately address the road/stream crossing/culvert issue. Given the
projected transportation corridor, Pebble locale to Cook Inlet, and the inevitability of a further
network of "minor" roads in the mine and TSF locale, plus additional infrastructure linkages,
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road/culvert/stream crossings are a major concern for aquatic habitat and fisheries. Readers of the
Assessment should be directed to Frissell and Shaftel's Appendix G for a more comprehensive
discussion of this important topic.
EPA RESPONSE: The revised assessment addresses the road/stream crossing/culvert issue in
detail Secondary development is now described qualitatively in Chapter 13 of the revised
assessment. The reader is repeatedly directed to Appendix G for more details.
SLAUGHTER RESPONSE: Chapter 10 now provides much better information on the entire
culvert issue. Fish passage, proper (or improper) culvert design and construction, maintenance
requirements, and consequences of failure are more adequately outlined.
EPA FINAL RESPONSE: No response required.
The specific consequences of a failure on salmonid habitat and biology are portrayed well.
EPA RESPONSE: No changes suggested or required.
SLAUGHTER RESPONSE: OK.
EPA FINAL RESPONSE: No response required.
John D. Stednick, Ph.D.
No. It is unclear how the estimate that 50% of the culverts would fail was obtained, given that the
literature shows a range of 30 to 60% (Section 4.4.4). What literature was used? Are road BMPs
satisfactory in this environment? Have the Alaska BMPs been audited? Culvert repair taking a week
to several repairs in a month seems high. If the road crosses a critical salmon rearing stream,
conservative pipe sizing or bridgework could be considered. The direct loss or inaccessibility of
upstream salmon habitat does not necessarily translate to salmon loss. Timing of culvert blocking
event with salmon migration and duration of blockage should be considered. Need to include
references to Alaska Department of Natural Resources and Alaska Department of Transportation.
EPA RESPONSE: The literature showed a range of 30 to 61 %, with an average of roughly 50%.
The literature used was noted in Section 10.3.2.1. However, Flanders et al. 2000 was deleted in the
revised assessment, bringing the average culvert failure frequency to 4 7%.
Best management practices (BMPs) or mitigation measures would be used to minimize potential
impacts to salmon ecosystems from construction and operation of the proposed transportation
corridor. These BMPs, and their likely effectiveness, are now discussed in text boxes throughout
Chapter 10 (e.g., Box 10-2). Environmental characteristics along the transportation corridor
would likely render the effectiveness of standard or even "state of the art" mitigation measures
highly uncertain. Further discussion on this is contained in Box 10-5 of the revised Assessment.
We are not aware of any audits of Alaska BMPs.
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The text relating to culvert repair considers that the proposed mining would occur in an often
harsh, remote environment.
Design considerations (including sizing) for culverts are now discussed in Box 10-2. Culverts
would be designed in accordance with guidance in Alaska Highway Drainage Manual (ADOT
1995) and the Memorandum of Agreement between the Alaska Department of Fish and Game and
the Alaska Department of Transportation and Public Facilities (ADF&G and ADOT 2001). Both
of these documents are cited within Box 10-2.
Blockage of a culvert by debris or downstream erosion would prevent the in-and-out migration of
salmon and the movement of other fish among seasonal habitats. The direct loss or inaccessibility
of upstream salmon habitat does not necessarily translate to loss of a population of salmon, but
production would ultimately be reduced If blockage of a culvert by debris or downstream erosion
occurred during in-migration of salmon and persisted for several days, it would result in the loss
of spawning and rearing habitat. If it occurred during out-migration and persisted for several
days, it could cause the loss of a year class of salmon from a stream
What are the design considerations for the culverts? What precipitation/streamflow relationships will
be used for sizing purposes? What are the usual casual mechanisms for culvert failure? How much
woody material do these streams carry? Do culverts fail from debris plugging, road slumps, or
overtopping by storm events? What road BMPs will be implemented?
EPA RESPONSE: Design considerations (including sizing) for culverts are now discussed in Box
10-2. Culverts would be designed in accordance with guidance in Alaska Highway Drainage
Manual (ADOT 1995) and the Memorandum of Agreement between the Alaska Department of
Fish and Game and the Alaska Department of Transportation and Public Facilities (ADF&G and
ADOT 2001).
As noted in Section 10.3.2, culverts are deemed to have failed if culverts (and thus fish passage)
are blocked (e.g., by debris, ice, or beaver activity) or if stream flow exceeds culvert capacity,
resulting in overtopping and potential road washout. The causal mechanisms for culvert failure
are briefly discussed in Section 10.3.2.
We do not have an estimate of the amount of woody material carried by streams in the assessment
area.
BMPs (e.g., stormwater runoff and fine sediment mitigation) that would be implemented are now
discussed in text boxes throughout Chapter 10 of the revised assessment.
Roy A. Stein, Ph.D.
Sizing Culverts: Page 5-61. Here the suggestion is that "Culverts must be 0.9 times the ordinary
high-water width..." and where the channel slope is less than 5%, the "the culvert is allowed to be
0.75 times" this same metric. Does this take into account global climate changes, which would mean
higher flow rates than historically has been the case? Shouldn't culverts be sized larger than what
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historical flow rates would suggest, given that Climate Change will likely result in more intense
storms and therefore greater stream flows than has historically been the case?
EPA RESPONSE: The commenter makes a good point. We do not believe that the sizing
suggestions noted by the commenter (found in the Memorandum of Agreement between the
Alaska Department of Fish and Game and the Alaska Department of Transportation and Public
Facilities (ADF&G andADOT 2001) take into account global climate change. Climate change
projections and potential impacts are now included in Chapter 3. We note in Chapter 10 of the
revised assessment that climate-related changes, such as increased flood frequency and shorter
return interval for major flood events, would likely undermine the structure of the proposed
transportation corridor and stream crossings. The variability and magnitude of stream flows could
also enhance other impacts described in the chapter. Interactions between climate change and
mining risks are discussed in Box 14-2.
Culvert Failures: Page 6-42. Culvert failure rates of 30-66% suggest we are doing something
wrong with establishing these culverts to maintain stream flow under a road. How might we reduce
this rate of failure (larger culverts? placement issues? solutions of any sort?)? In fact, if indeed 50%
of the culverts will be blocked (see bottom of page 6-43), are we not dealing with an unacceptable
solution of running streams under roads? Might there be some replacement of these culverts with
bridges; certainly, bridges are more expensive to build, but they simply do not have the failure (i.e.,
blockage) rate that culverts do. Might there be a trade-off here between initial investment costs (high
for bridges) and salmon protection (fewer blockage events)? What would Best Management
Practices tell us in this context?
EPA RESPONSE: In the revised assessment, culvert failure frequencies are reported as 30 to
58%, with an average failure estimate of 47%. The likelihood of extended blockages would be low
during mine operations because the roadway would be monitored daily to ensure that failures
could be rapidly identified and repaired However, the likelihood would increase after mine
operations cease, if inspection and maintenance frequencies declined to those of typical roads.
Best management practices (BMPs) or mitigation measures would be used to minimize potential
impacts to salmon ecosystems from construction and operation of the proposed transportation
corridor. These BMPs, and their likely effectiveness, are now discussed in text boxes throughout
Chapter 10.
Bridges would generally have less impact on salmon than culverts, but can result in the loss of
long riparian side channels if they do not span the entire floodplain. The actual decision as to
what type of structure (bridge versus culvert) would be constructed at each crossing would be
made by industry engineers in consultation with state permitting staff.
William A. Stubblefield, Ph.D.
Potential effects on salmonid populations were evaluated due to culvert blockage and failures.
Culvert blockages will prevent salmon passage leading to possible effects on reproductive success.
Literature data for the incidence of culvert failures were used in assessing failure probability. This
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seems to be an appropriate approach given the hypothetical nature of the mine used in the
assessment; however, this is not my area of expertise and I am not aware of additional data that
should be considered.
EPA RESPONSE: No change suggested or required.
STUBBLEFIELD RESPONSE: No additional comment on this question.
EPA FINAL RESPONSE: No response required.
Dirk van Zyl, Ph.D., P.E.
Road and culvert failure likelihood. The likelihood of road and culvert failures is discussed in
Section 4.4.4 (p. 4-62). This section relies on the paper by Furniss et al. (1991) for a number of
aspects. As was pointed out above, this paper is focused on forest and rangeland roads and is not
applicable to the access road for the Pebble Mine. It is recommended that further evaluations be done
of similar roads at mines constructed between mines and port facilities to update this section.
EPA RESPONSE: Furniss et al. (1991) does focus on forest and rangeland roads, but it is a
seminal publication on the potential effects of roads, particularly as they relate to salmon. The
general conclusions of that paper should be applicable to the transportation corridor proposed in
the assessment. The failure frequencies cited in the revised assessment are from modern roads and
not restricted to forest roads. Because the proposed mining would take place in an undeveloped
area, much of the literature used in the assessment is necessarily from areas outside of Bristol
Bay. However, to the extent possible we used recent literature from representative environments.
We found no literature concerning the operational success of culverts on roads between mines or
connecting mines and ports.
Road and culvert failure consequences. The failure consequences discussed in Section 6.4 seem to
be based on almost total regulatory failure during and after operations. The information also serves to
highlight the aspects that should be considered when designing, operating and maintaining the access
road during operations and subsequently during closure.
EPA RESPONSE: In the revised assessment, consequences of failures and routine operations are
covered in Chapter 10. The failure consequences are not based on almost total regulatory failure.
Rather, they take into account the use of best management practices (BMPs) or mitigation
measures that are discussed in text boxes throughout Chapter 10. Nonetheless, environmental
characteristics along the transportation corridor would likely render the effectiveness of standard
or even "state of the art" mitigation measures highly uncertain. Further discussion on this is
contained in Box 10-5 of the revised assessment.
VAN ZYL RESPONSE: No further comments on Question 7.
EPA FINAL RESPONSE: No response required.
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Phyllis K. Weber Scannell, Ph.D.
The risks to salmonid fish due to culvert failures would be minimized by implementation of permits
by Alaska Department of Fish and Game (ADF&G), Habitat Division. Under A.S. 16.05.840-870,
Alaska has some of the most protective laws for fish and fish habitat in the United States. Further,
given the lack of specific information on road alignments, construction methods and stream
crossings, it is not possible to calculate lengths of affected streams, quantify loss of fish habitats, or
predict failures of culverts, side slopes, etc. The document would be strengthened if it included
specific information on locations of spawning and rearing habitats and estimated the contribution of
fish habitats in the Nushagak River and Kvichak River Watersheds to the Bristol Bay fishery.
EPA RESPONSE: Best management practices (BMPs) or mitigation measures that would be used
to minimize potential impacts to salmon ecosystems from construction and operation of the
proposed transportation corridor are now discussed in text boxes throughout Chapter 10. Box 10-2
specifically refers to fish habitat regulations under Title 16.
As noted in the revised assessment, uncertainty exists in the characterization of streams and
wetlands affected by the proposed transportation corridor. Based on the chosen road alignment
scenario (which agrees with that proposed in Gliaffari et al. 2011) we feel that we are justified in
estimating the potential footprint of the proposed corridor and its potential impact on fish habitats
and populations. We note in the revised assessment that "Although this route (the one proposed in
the EPA scenario) is not necessarily the only option for corridor placement, the assessment of
potential environmental risks would not be expected to change substantially with minor shifts in
road alignment. Along any feasible route, the proposed transportation corridor would cross many
streams, rivers, wetlands, and extensive areas with shallow groundwater, including numerous
mapped (and likely more unmapped) tributary streams to Iliamna Lake (Figures 10-1 and 10-2)."
Specific information on locations of spawning and rearing habitats along the proposed
transportation corridor is difficult to obtain; as noted in the revised assessment, the Alaska
Anadromous Waters Catalog and Alaska Freshwater Fish Inventory do not necessarily
characterize all potential fish-bearing streams because of limited sampling along the corridor.
Nonetheless, the revised assessment summarizes the species, abundances, and distributions that
would potentially be affected, and places the streams along the transportation corridor into the
context of the entire Nushagak and Kvichak River watersheds with respect to important watershed
attributes such as discharge, channel gradient, and floodplain potential. As far as placing
potential mining impacts in the context of the entire Bristol Bay watershed, we are unable to build
a complete IP model, as this would require validation and more elaborate construction of metrics
appropriate to this region. However, our preliminary characterization provides the building blocks
for assessing the distribution of key habitat-forming and constraining features across these
watersheds.
WEBER SCANNELL RESPONSE: The reviewer agrees with the EPA response; however, it is
important to note that extensive fish sampling before project development will be necessary to
provide adequate protection to the fishery.
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The discussions of fish and fish habitats have been revised and expanded in the 2013 draft
Assessment. Chapter 10 presents a more thorough discussion of fish presence, what sampling
has been done and where there is a lack of information. This revised chapter relates the
information on fish presence, abundance (where known) and habitat use to different scales of
the Nushagak and Kvichak River watersheds. As presented, the reader is better able to
understand the potential loss of habitat, especially with development of a transportation
corridor. EPA is to be commended for this revision; Chapter 10 strengthens the entire
Assessment.
EPA FINAL RESPONSE: No response required.
Paul Whitney, Ph.D.
Criteria for bridge versus culvert installations along the proposed haul road. The dynamic process of
beaver dams causing streams to move across the floodplain should also be a criterion for determining
if and where culverts are installed for a potential road (pages 4-36 and 4-63). Even if salmonids are
not present at a stream crossing, the mosaic of active and decayed beaver ponds in the floodplain can
be important rearing areas for forage fish and benthic drift that are utilized by salmonids (Snodgrass
and Meffe, 1997; Schlosser and Kallemeyn, 2000). If beaver dams (but not salmonids) are present
above proposed stream crossings, bridges or causeways that allow the streams to move across the
floodplain should be recommended versus a culvert.
EPA RESPONSE: The revised assessment is based on the assumption that crossings over streams
with mean annual flows greater than 0.15m3/s would be bridged However, the actual decision as
to what type of structure (bridge versus culvert) would be constructed at each crossing would be
made by industry engineers in consultation with state permitting staff We agree with the reviewer
that beavers can have an important influence of channel location and morphology. However,
beavers move frequently, so over the life of the road the locations of beaver dams would change
and therefore seem unlikely to provide a good criterion for crossing designs.
Beaver are known to block culverts at the upstream ends. Beaver-proof culverts are an option, but all
the designs I am aware of would certainly hinder, if not block, movement of forage fish and benthic
drift. Causeways or bridges are the best way to encourage beaver activity (i.e., functions) and all the
benefits that accrue.
EPA RESPONSE: The actual decision as to what type of structure (bridge versus culvert) would
be constructed at each crossing would be made by industry engineers in consultation with state
permitting staff.
Toxic plume. Spills of transported chemicals are not quantified in the culvert failure section of the
assessment. I have participated in a mine risk assessment and a landfill risk assessment where spills
of cyanide and landfill leachate have been modeled. While I did not conduct the plume movement
analyses, stream hydrologists readily calculated how far spilled materials would move down stream
until the concentrations of chemicals in streams reached acceptable benchmarks. The longevity of a
spill of chemicals for copper processing should be calculated. It appears that the Water Treatment
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failure assessment on page 6-39 conducted some sort of plume analysis to determine the potential for
an impact on Iliamna Lake. Perhaps it is possible to use this analysis, or at least the model, to address
the consequence of a spill of transported chemicals.
EPA RESPONSE: We have modeled the transport of spills from pipeline failures and emissions
from the wastewater treatment plant and leakage of leachates. In Section 10.3.3.1 of the revised
assessment we estimate the number of reagent spills that would occur over the roughly 25-year life
of Pebble 2.0 scenario. We did not conduct a plume analysis for a spill of transported chemicals,
but given the toxicity of sodium ethyl xanthate (Section 6.4.2.3) we expect that a spill of this
compound into a stream along the transportation corridor would cause a fish kill. Given the
uncertainty concerning the nature and magnitude of a truck accident and spill, we decided that a
quantitative analysis of transport and fate would not materially contribute to the value of the
assessment.
3.10 Charge Question 8
Does the assessment appropriately characterize risks to salmonidfish due to pipeline
failures? If not, what suggestions do you have for improving this part of the assessment?
Are significant literature, reports, or data not referenced that would be useful to
characterize these risks, and if so what are they?
David A. Atkins, M.S.
The discussion of pipeline failures is based on published failure rates, principally for oil and gas
pipelines. This analysis results in a pipeline failure rate of one per 1,000 km per annum. This is a
pretty generic number that does not consider actual pipeline design. Rather it indicates that pipelines
designed using standard practices do fail with a fairly high frequency. The Assessment does not
apply this failure rate to the gas and diesel pipelines because "they are not particularly associated
with mining." Without the mine, there would be no pipeline. So given that this rate of failure is
quantifiable based on good data and that the pipeline would be built to serve the project, this risk
should be considered.
EPA RESPONSE: The assessment assumes that pipeline design follows standard ASME practices.
A diesel pipeline failure and resultant spill into two creeks has been added in Chapter 11 in the
revised assessment. A gas leak is considered but is not analyzed because of the lack of significant
causal linkage to fish production.
ATKINS RESPONSE: This response is adequate.
EPA FINAL RESPONSE: No response required
A concentrate pipeline spill would have differing impacts depending on when and where the spill
occurred, with deposition in Lake Iliamna likely being the worst outcome. As noted in the report, it is
likely that a pipeline spill would be detected rapidly and that the volume of the spill would be limited
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and amenable to remediation. A better description of how concentrate pipeline failures have occurred
would be helpful to better understand the risk for this project (e.g., the July 2012 Antamina
concentrate pipeline failure, although this pipeline would operate under a much different pressure
regime due to extreme altitude change).
EPA RESPONSE: Consolidated, statistically representative data on concentrate pipeline failures
are not readily available, although anecdotal evidence from some case studies can be found. The
pipeline failure statistics reviewed for the assessment come primarily from oil and gas pipelines,
but also include some water and hazardous liquid pipelines. The perfornmnce of mining
concentrate pipelines is not expected to be better than the perfornmnce of oil pipelines, because
concentrate pipelines would be expected to be more susceptible to internal corrosion and abrasion.
The 2012 Antamina concentrate pipeline failure in Peru was reportedly caused by the rupture of a
pipe elbow in a valve station. The regulatory, geographic, and operating conditions of the
Antamina pipeline may differ greatly from those of the concentrate pipeline in the assessment
scenarios. A discussion of causes and probabilities ofpipeline failures is included in Section 11.1
of the revised assessment. The revised assessment also includes discussions of concentrate spills at
the Bingham Canyon, Utah, and Alumbrera, Argentina, copper mines (Section 11.3.4.2).
ATKINS RESPONSE: This response is adequate.
EPA FINAL RESPONSE: No response required
Steve Buckley, M.S., CPG
The assessment does generally describe the potential risks to fish from hypothetical pipeline failures.
EPA RESPONSE: No changes suggested or required.
Courtney Carothers, Ph.D.
A pipeline failure would be expected to release toxic leachate into stream systems in the
transportation corridor, none of which would dilute the leachate enough to prevent severe toxic
effects (both immediate and long-term). The report discusses three pipeline failures in the Bajo de la
Alumbrera mine in Argentina. The largest pipeline failure lasted two hours (compared to only two
minutes of exposure hypothesized in the current mine scenario). The report could more clearly
describe this case and its likely effects. The report appears to appropriately characterize risks to
salmonid fish due to pipeline failures, although I have no particular expertise with which to evaluate
this assessment.
EPA RESPONSE: We agree that it would be desirable to have more information on the effects of
the largest Bajo de la Alumbrera spill, but we have included all information on that failure that is
available.
CAROTHERS RESPONSE: EPA response is sufficient.
EPA FINAL RESPONSE: No response required
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Dennis D. Dauble, Ph.D.
The risks to salmonid fish due to release of pipeline concentrate/slurry and leachates (as return water)
are well described. However, risks of a diesel fuel spill are not. More detail could be provided on
reclaimed water. For example, what toxic constituents (and at what volumes) would be released to
the environment if these pipelines failed?
EPA RESPONSE: A diesel pipeline failure and resultant spill into two creeks has been added in
Chapter 11 in the revised assessment. New data on concentrate leachate in the slurry have been
added, and it is assumed to also describe the return water.
DAUBLE RESPONSE: I appreciate the addition to the assessment. What's missing, however,
is an explanation of which mine scenario was selected from the pipeline discussion and why.
Not until section 11.3.4.4 was it stated that pipeline failures would be likely under the Pebble
6.5 scenario. What about Pebble 0.25 and 2.0? Were they considered? If not, please state why.
Also, the last two bullets under 11.5.5 Uncertainties appear as conclusion statements, not
uncertainties.
EPA FINAL RESPONSE: The failure rate is assumed to be constant. Failure is most likely under
the Pebble 6.5 scenario because it would have the longest duration. Those bullets begin with a
statement of uncertainty and conclude by stating what can be concluded given that uncertainty,
which was recommended by another reviewer in the previous round of peer review.
Gordon H. Reeves, Ph.D.
Assuming that characterizations of the pipeline failure are accurate, the potential impacts on fish and
fish habitat are appropriate and reasonable. It was clear that the effects of a pipeline failure could be
major, depending on the duration and timing of the spill, because of the concentration of metals in
the slurry, the particular life-stage present, flow conditions, and the reduced potential to fully remove
the material from a stream or wetland afterwards.
EPA RESPONSE: No change suggested or required.
The one question that I had about this section was the potential impact on phytoplankton and
zooplankton in Lake Iliamna, particularly at the local scale. I assume that any spill from pipeline
failure would have potential impacts on the lake and on phytoplankton and zooplankton, the major
food for juvenile sockeye salmon. The ecological consequences would depend on the extent and
intensity of any spill and on how juvenile sockeye use areas near tributary streams. I would expect
that a spill could be particularly detrimental if juvenile sockeye use the area near or adjacent to natal
streams when they enter the lake. I think this should be considered in more detail in any additional
analysis.
EPA RESPONSE: The toxicity data for species sensitive to copper and most other potentially toxic
metals are derived from planktonic crustaceans, so it is already addressing planktonic lake species
more directly than stream benthic species. However, the more detailed analyses of aqueous
releases in the revised assessment (Chapter 11) provide a better basis for addressing the risk of
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exposure in Iliamna Lake. Because the aqueous phase of the product concentrate slurry would
enter the stream briefly and would be rapidly diluted in the lake, it is not judged to be a major risk
to plankton relative to the potentially sustained direct effects on salmon eggs and larvae of the
deposited solid phase or relative to stream invertebrates, which would have much less benefit of
dilution.
Charles W. Slaughter, Ph.D.
No. Concerns with pipelines crossing streams, watercourses and wetlands are similar to those earlier
expressed for the road corridor. On-site investigation may well reveal many more "watercourses,"
including intermittent and ephemeral streams, than the 70 crossings cited; possible pipeline failures
thus may have much wider potential for impacting salmonids than is indicated in the Assessment.
EPA RESPONSE: The document has been edited to indicate that 70 is a minimum value.
SLAUGHTER RESPONSE: OK.
EPA FINAL RESPONSE: No response required
The "probability" argument on p. 6-32 is an understandable attempt at quantification, but is
unpersuasive. Given the spill history of TAPS, pipelines in the Prudhoe Bay field, and recently in
Montana (?), suggesting the probability (with what confidence limits?) that there would be only 1.5
stream-contaminating spills or two wetland-contaminating spills over 78 years of operation seems
wildly optimistic (and what is half a spill?).
EPA RESPONSE: If you think of the mine as a repeated experiment (i.e., many mines with
concentrate pipelines of that length and duration), we would expect a mean frequency of 1.5 spills.
A more straightforward explanation is that we expect 1 or 2 spills, given the scenario. These
frequencies are based on a large data set, not just the TAPS experience (which is an atypical
pipeline design and much larger than the diesel line) or the spill in the Yellowstone River (which is
a single event). An explanation of the frequency has been added in Section 11.1 of the revised
assessment.
SLAUGHTER RESPONSE: The narrative of Section 11.1 is helpful. Many uncontrolled
variables inevitably affect the length/duration/failure analysis; I can envision an argument that
the transportation corridor pipelines will be in a tightly-controlled (at least in early years)
setting and subject to stringent inspection and maintenance, in contrast to many thousands of
miles of pipeline in more urban or trafficked locales, with much more opportunity for
vandalism, ignorance (ignoring the "do not dig here" warnings), or accidental damage - so the
PLP corridor pipelines should be more reliable than the historical record might indicate.
Of course, the TAPS line is much larger, insulated, partially above-ground on thermopiles and
partially buried, and atypical in size; it may also be atypical in that at time of construction, it
was designed with state-of-art flow and pressure sensors, automated control systems, regular
aerial patrol inspection, etc - yet still experiences incidents, as does the network of gathering
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lines on the North Slope. And of course, the Yellowstone river spill was a single event - as is
every spill ~ so does not of itself provide frequency analysis.
Given three pipelines (excluding the natural gas line) and your failure probability estimates on
p. 11-5, is it fair to say that under the 25-year PLP 2.0 scenario 8 or 9 spills would be expected
(3 x 2.8), and under the 78-year PLP 6.5 scenario 24 to 27 spills would be expected (3 x 8.6)?
This would seem in accord with your estimate of virtual certainty (99.9% chance) that at least
one pipeline would fail, regardless of mine size.
EPA FINAL RESPONSE: The first two paragraphs of the comment suggest that, even though it
might be argued that the pipelines would be subject to an unusual level of maintenance and
protection, the history of the TAPS pipeline suggests that even when special attention is provided,
failures occur. Therefore these comments support the assessment and no change is required.
Concerning the third paragraph, we do not provide the combined spill frequencies for the
pipelines because their consequences would be quite different. Therefore, we have not added a
statement to the effect that failure of at least one line is virtually certain.
Assuming that any spill (over the 78-year project span) would last only two minutes (p. 6-32, p. 6-
34), with a consequent minimal volume of spilled material, also seems highly optimistic. Even
highly-automated systems, with redundant sensors and automatic responses, are susceptible to error
or failure, and the Bristol Bay watershed environment is not benign with regard to mechanical
apparatus. The authors appear to recognize this with their discussion of the Alumbrera incident.
EPA RESPONSE: The scenario has been modified to a 5-minute response. Also, more
information has been added about the possibility of system failure or human error in response to
this and similar comments. The uncertainty discussion in Chapter 11 indicates that the exposure
scenario is predicated on the successful operation of a remote shutoff There may be extreme
weather or geological events that render the remote shutoff system inoperable. We did not evaluate
those events, so the assessment may underestimate these risks.
SLAUGHTER RESPONSE: OK. The hypothesized Chinkelyes and Knutson analyses seem
quite appropriate, and provide good illustrations of the possible consequences of a spill at a
water crossing. I also appreciate the discussion of potential human error, Section 11.3.4.2, and
Table 11.9, Section 11.5.5. There may well be optimism about SCADA systems but something
or someone can always mess up!
EPA FINAL RESPONSE: No response required
The specific consequences of a failure on salmonid habitat and biology are portrayed well.
EPA RESPONSE: No changes suggested or required.
SLAUGHTER RESPONSE: OK.
EPA FINAL RESPONSE: No response required.
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John D. Stednick, Ph.D.
The pipeline corridor consists of four pipelines over a distance of 86 miles. No information was
provided on pipeline structure or placement, other than mentioning of stream crossings. The pipeline
failure of concentrate slurry was modeled using chemistry from the Aitik (Sweden) mine. Is this best
approximation? That mine is about 80 years old and is processing ore from the edge of the pit, with
much lower sulfur content than Pebble.
EPA RESPONSE: More information on the pipeline structure and placement was provided in
Section 6.1.3.2 of the revised assessment. We have replaced the USGS leachate data from the Aitik
product with analyses from actual concentrate slurry provided by Rio Tinto to describe the
aqueous phase of the slurry and the return water, which would be alkaline (Section 11.3.2.1).
However, the Aitik data are used to estimate the risks from deposition of the product in a stream or
wetland The environmental leaching of the concentrate would resemble the USGS's leaching test
of the concentrate, not the alkaline solution in the pipeline slurry. To the best of our knowledge,
no other aqueous leach test of a porphyry copper product concentrate is available.
Pipeline failures can be significant in any environment and spill or pipe break prevention requires
significant monitoring. Will automatic shutoff controls be included? Are workers stationed 24
hours/day every day? Some of the past Alaska failures were in winter conditions, when things were
not easily visible—under ice or snow cover. How will this be addressed?
EPA RESPONSE: Our scenarios include remotely-operated valves tied to a supervisory control
and data acquisition (SCADA) continuous monitoring system tied to a continuously staffed control
room The remotely-operated valves could be triggered either manually or through software, but
we expect that except in the event of a clear rupture of the pipeline, the SCADA signals would
trigger an alarm that would initiate manual intervention by the operator. Consistent with best
management practices, we have assumed that the pipeline would be visually inspected along its full
length at least daily, and that the inspection protocols would consider the difficulties of detecting a
spill under snow or ice. Potential remedial actions for cleanup up of diesel, product concentrate
and return water spills are discussed in Chapter 11.
The toxicity approach seems reasonable. What is the anticipated chemistry of the return waters?
Diesel spill monitoring? The geometric mean of three values (which references) indicates that there
is a 14% probability of failure in each pipeline in each year. This is not acceptable at any level.
EPA RESPONSE: The return water is assumed to be the same as the aqueous phase of the slurry
water. A diesel spill scenario has been added in Chapter 11. The pipeline failure rate reported in
the assessment is similar to the rates calculated in studies by others and represents several large
datasets. Some of the reported failures are due to corrosion, which tends to result in small
releases; some of the failures are due to mechanical impacts, which tend to produce larger
releases; some are due to other causes. The buried pipelines in our scenarios would be expected to
have a lower incidence of rupture from third party activities, but may have a higher incidence of
rupture due to landslides or earthquakes than the overall dataset. Corrosion or corrosion leaks
could go undetected for longer periods of time compared to an aboveground pipeline.
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Roy A. Stein, Ph.D.
Pipeline Failures I. What dictates 14 km between automatic shut-off valves; shouldn't this distance
be shorter as the pipe becomes larger, i.e., related to the amount of liquid/slurry that would be spilled
upon pipe failure? Shouldn't all of these pipelines be double-walled? What would Best
Management Practices tell us in this context?
EPA RESPONSE: The distance between valves appears to be consistent with current practices.
The pipelines are described as double-walled in above-ground reaches. A double-walled pipeline
along the entire length of a pipeline might be desired from a purely environmental protection
standpoint; however, it may not be feasible or cost effective to do this. Therefore, we have proposed
the most commonly used (and accepted method) of double-walled construction over any water
bodies. There are a large number offactors that go into standard practices for design,
construction, and testing of pipelines. In the draft assessment, we included a selected number of
these factors as examples of our design mitigation measures. In the revised assessment (Section
6.1.3.2), we have included a statement that the design would follow the standards of the American
Society of Mechanical Engineers, to indicate that modern mitigation measures would be included.
Pipeline Failures II. Like all other failures, it seems to me that "Standard Operating Procedures
(SOP)" for mitigation should be in place in anticipation of any future spill or contamination of the
environment. I do not think that these procedures need to be in this report, but an acknowledgement
of their presence and that mining companies will follow these SOPs in response to any spills that
occur, be it pipeline, TSF, truck, leachate bed, etc.
EPA RESPONSE: We agree that a mining company should have an SOP for remediating spills,
but we have not been able to find such an SOPfor remediating a product concentrate pipeline
spill.
William A. Stubblefield, Ph.D.
Potential effects on salmonid populations were evaluated due to potential pipeline failures as part of
the risk assessment. This evaluation focused on potential failures associated with the pipelines for the
product concentrate slurry and return water. No consideration of the natural gas or diesel pipelines
was presented, stating that such pipelines "are common and the risks are well-known." Although I
would acknowledge the failures in natural gas and petroleum pipelines are common, I would not
discount the potential effects to salmon populations associated with such spills.
EPA RESPONSE: A diesel pipeline failure and resultant spill into two creeks has been added in
Chapter 11. Natural gas is not a contaminant of concern because it would vaporize and, at worst,
burn, which would not pose a significant risk to salmonid fish.
STUBBLEFIELD RESPONSE: The revised document evaluates the potential effects to aquatic
organism populations as a result of a petroleum diesel fuel spill. The document attempts to
examine the available literature and characterizing the acute and chronic effects of diesel fuel
on aquatic organisms. However, it is apparent is that there is little high quality information
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available that has been gathered in any sort of consistent manner that would permit an
adequate quantitative evaluation of the effects of a diesel fuel spill. Inconsistent approaches in
characterizing hydrocarbon exposures (i.e., differing analytical methods) and inconsistent
approaches in conducting toxicity tests make it virtually impossible to apply a quantitative
approach to the evaluation of diesel fuel spill effects at this time. Hydrocarbon toxicity models
such as the Target Lipid Model (DiToro et al. 2000 a,b) or PETROTOX (Redman et al 2012)
offer the best approach to assess hydrocarbon mixture toxicity; however, substantial analytical
characterization of hydrocarbon concentrations are needed. For purposes of the Bristol Bay
assessment the approach taken is probably adequate given that conclusions can be reached
about the potential effects of a diesel spill. It should be recognized, however, that the state of
the science for evaluating hydrocarbon mixture toxicity is somewhat lacking and additional
research is needed.
Di Toro DM, McGrath JA, Hansen DJ. 2000a. Technical basis for narcotic chemicals and
poly cyclic aromatic hydrocarbon criteria. I. Water and tissue. Environ Toxicol Chem 19:1951-
1970.
Di Toro DM, McGrath JA. 2000b. Technical basis for narcotic chemicals and poly cyclic
aromatic hydrocarbon criteria. II. Mixtures and sediments. Environ Toxicol Chem 19:1971-
1982.
EPA FINAL RESPONSE: No response required.
Evaluation of potential impacts due to a spill of product concentrate slurry or return water was based
on extant data from an existing copper mine in Sweden; to the extent that this slurry and return water
is representative of similar materials coming from the Pebble mine, this approach is appropriate. The
assumptions used in the amount of material that might possibly be spilled seems appropriate and
based on past experience and realistic assumptions; however, these assumptions need to be
reconsidered if and when a real mine plan is prepared.
EPA RESPONSE: The Aitik leachate is no longer used to estimate the aqueous phase of the
slurry, in response to other comments. Because the slurry would be alkaline, appropriate
analytical data were obtained from Rio Tinto (Section 11.3.2.1). However, the Aitik data are still
used for the leaching of the concentrate in a stream or wetland where neutral water would be the
leaching agent. No other relevant data are available.
STUBBLEFIELD RESPONSE: As previously stated, to the extent that slurry and return water
used in the assessment is representative of similar materials coming from the Pebble mine, this
approach is appropriate.
EPA FINAL RESPONSE: No response required
Dirk van Zvl, Ph.D., P.E.
The EPA Assessment does not identify or appropriately characterize the risks to salmonid fish due to
pipeline failures. It only estimates the likelihoods of occurrence and the consequences. See
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discussion under Question 4 above regarding suggestions for improving estimation and expression of
the magnitude of risks to salmonid fish due to pipeline failures.
EPA RESPONSE: We believe that the likelihood of an occurrence and its consequences constitute
an appropriate and generally accepted definition of risk. We have estimated those to the extent that
existing information allows.
Pipelines failure likelihood. The EPA Assessment focuses on the failure of the concentrate pipeline
because "We do not assess failures of the natural gas or diesel pipelines here because such pipelines
are common, their risks are well known and they are not particularly associated with mining". I find
this statement puzzling because all pipeline failures should be of concern. It is further puzzling
because the likelihood of pipeline failures for the concentrate pipeline is derived from the failure
statistics for pipelines in the oil and gas industry (p. 4-60). Failure of the Baja de la Alumbrera
concentrate pipeline in Argentina is suggested as an analog, indicating that such failures can occur;
however, I disagree that "it suggests that concentrate pipeline failures are common at a modern
copper mine." This last statement is not supported by any further analysis of concentrate pipeline
failures at other modern copper mines. It is recommended that such analyses be performed or that the
text be edited to indicate this shortcoming.
EPA RESPONSE: The revised assessment contains an analysis of the risks of a diesel pipeline
spill in Section 11.5. Natural gas is not a contaminant of concern because it would vaporize and,
at worst, burn off, which would not pose a significant risk to salmonid fish (Chapter 11). The
quoted statement is literally correct. Baja de la Alumbrera is a modern copper mine and pipeline
failures are common there. This suggests that failures are common. Further, concentrate pipeline
failures at the Antamina and Bingham Canyon mines are now discussed However, the statement
in the revised assessment has been weakened by changing "common " to "not uncommon." To
support that statement, a review ofpipeline failures at U.S. porphyry copper mines has been added
(Section 11.1). However, we have not found a sufficient record ofproduct concentrate pipeline
operations to develop a probability offailure that is specific to that pipeline type.
Pipelines failure consequences. Failure consequences are focused on the release of concentrate into
water. As indicated in Appendix H of the report, the analog concentrate from the Aitik mine is
dominated by chalcopyrite, a sulfide mineral which contains the copper. If the concentrate is
submerged under water in relatively slow flowing streams then very little long-term release of the
copper will occur, as the water does not contain sufficient oxygen to allow for sulfide oxidation. It is
only when the concentrate is transported to locations above the water level that oxidation and release
of metals will occur.
EPA RESPONSE: Subaqueous oxidation of sulfides does occur in well oxygenated waters as this
comment recognizes by stipulating "relatively slow moving streams". However, as the flow data in
the spill scenario indicate, these are not slow moving streams. Subaqueous leachate column tests
are conducted to assess the potential for subaqueous oxidation. Tests conducted by the Pebble
partnership indicate the potential for subaqueous oxidation. Salmonids require high dissolved
oxygen levels, so salmonid streams are necessarily well oxygenated. For example, the EBD states
that mean dissolved oxygen levels for the North Fork Koktuli River was 10.2 ppm This oxygen
would oxidize the sulfides.
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VAN ZYL RESPONSE: No further comments on Question 8.
EPA FINAL RESPONSE: No response required.
Phyllis K. Weber Scannell, Ph.D.
This section of the document focuses on effects of pipeline failures; however, without a viable mine
plan, descriptions of pipelines and estimates of possible effects are speculative. The resource
developer may opt to build a pipeline to transport fuel from the coast to the mine site or slurry
concentrate to the port. Construction of any pipelines would require review and approval by state
and federal agencies, such approvals would likely contain monitoring plans to ensure pipeline
integrity. However, the risks of pipeline failures should not be minimized; the Fort Knox Mine near
Fairbanks recently experienced a 45,000 gallon spill of cyanide solution after a bulldozer struck a
supply line (Fairbanks Daily News Miner, August 24, 2012).
EPA RESPONSE: We agree that the specific locations ofpipelines and requirements for
monitoring may differ from our scenario, which is based on preliminary mine plans (Ghaffari et
al. 2011). However, we believe our scenario is plausible and allows an evaluation of potential
impacts from pipeline failures. The Fort Knox spill has been added to the assessment as an
example of spills due to human error in Section 11.1.
WEBER SCANNELL RESPONSE: The reviewer is pleased that the Fort Knox spill was added
as an example of human error; including the Fort Knox example demonstrates that pipeline
failures can and do happen.
No further comment; my concerns have been addressed.
EPA FINAL RESPONSE: No response required
The risks of a pipeline failure to salmonid fish depend on the duration of the spill, the type of
material spilled (return water or concentrate), the location of the spill (in the uplands or in a
waterway), and the timing. The effects of a pipeline failure in a waterway when juvenile salmon are
present would be far more severe than a pipeline failure in an upland area.
EPA RESPONSE: We agree with this comment. Discussion of spill location and life stage exposed
has been expanded in Section 11.3, and the other issues have been carried over from the original
draft of the assessment.
WEBER SCANNELL RESPONSE: The reviewer is pleased that this discussion has been
expanded.
The revised draft Assessment has expanded the information on pipeline failures to include
clearer explanation of different types of failures, probability of failure and possible effects to
fish at different life stages. The arguments presented in this section (Chapter 11) are made
stronger by discussing the role of human failure (page 11-6). The sections on exposures (11.3.2)
and exposure-response (section 11.3.3) are well-documented and a valuable contribution to this
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chapter. This reviewer is pleased with the revisions made to this section; the concerns
expressed in the initial comments have been satisfied.
EPA FINAL RESPONSE: No response required.
Given that there currently is no information on road alignments or locations of future pipelines, it is
not possible to estimate the number of stream crossings (70, page 6-30) or an exact length (269 km,
page 6-30) of potentially affected waterways. The risks from pipeline failures outlined in the draft
document should be revised when more specific information on the mine plan of operations becomes
available.
EPA RESPONSE: The road alignment and length in Northern Dynasty Mineral's preliminary
mine plan (Gliaffari et al. 2011) were used in this assessment. The number of stream crossings
was also detailed in that plan, and we checked these values using USGS data. We would expect
that risks would be re-evaluated as part of a future specific transportation corridor plan. No
change required.
WEBER SCANNELL RESPONSE: The reviewer agrees that no change is required.
The reviewer agrees that this comment has been adequately addressed.
EPA FINAL RESPONSE: No response required
Paul Whitney, Ph.D.
Refer to comments/responses to Questions 2 and 7.
EPA RESPONSE: See responses to those questions.
3.11 Charge Question 9
Does the assessment appropriately characterize risks to salmonidfish due to a potential
tailings dam failure? If not, what suggestions do you have for improving this part of the
assessment? Are significant literature, reports, or data not referenced that would be useful
to characterize these risks, and if so what are they?
David A. Atkins, M.S.
The Assessment generically describes tailings dam failures and the potential impact in detail. It also
uses some site-specific information on tailings supernatant and humidity cell leachate. There is no
question that a tailings dam failure would be catastrophic for the fishery and the project, and although
low probability, is the single largest risk to the fishery. A tailings dam failure could harm a very large
area of the watershed for a very long period of time and could require a massive and expensive
remediation effort.
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EPA RESPONSE: We agree. No change suggested or required.
The tailings deposition and storage methods outlined in the Wardrop NI 43-101 report and presented
in the Assessment are conventional for the industry and comply with Alaska State regulations.
Because of the dire consequences of a failure in this highly sensitive and unique environment, it
would be necessary to employ state of the art methods for tailings management and go 'beyond
compliance' when designing and constructing this facility. This may include employing methods that
are novel, incur significant additional cost for construction, and lead to a more stable and lower
maintenance facility in the long term, such as dry stack or paste rock tailings (blending waste rock in
with tailings in the impoundment to provide extra geotechnical stability). These methods, however,
are not common practice and in some instances are still under development.
EPA RESPONSE: The assessment addresses state of practice methods to identify potential risks
that could result from such practices. We agree that there is a possibility that a mining proponent
could design and propose practices that go beyond the state ofpractice in order to reduce potential
risks.
ATKINS RESPONSE: This response is adequate.
EPA FINAL RESPONSE: No response required.
Steve Buckley, M.S., CPG
The assessment does generally describe the potential risks to fish from tailings dam failures.
EPA RESPONSE: No change suggested or required.
Courtney Carothers, Ph.D.
In the event of a tailings spill, invertebrates and fish would be exposed to toxic tailings and leachate.
Actual tailings failure examples suggest the range of exposure would spread to an area more than 100
km. Copper would be especially toxic to invertebrates, fish eggs and larvae. Toxicity would last for
decades. The report appears to appropriately characterize risks to salmonid fish due to a potential
tailings dam failure, although I have no particular expertise with which to evaluate this assessment.
EPA RESPONSE: No change suggested or required.
CAROTHERS RESPONSE: EPA response is sufficient.
EPA FINAL RESPONSE: No response required
Dennis D. Dauble, Ph.D.
Tailings deposition is described in Chapter 4 of the main report, but I could not find anything that
described potential risks to fishes, including effects to aquatic food webs and loss of fish spawning
and rearing habitat.
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EPA RESPONSE: The TSFfailure description and the assessment of risks were presented in
separate chapters in the original draft assessment, but have now been moved into one location
(Chapter 9) for clarity.
DAUBLE RESPONSE: This change is a big improvement over the previous draft. What I like
is the inclusion of analogous sites: Clark Fork, Coeur d'Alene River, and Soda Butte Creek to
the discussion. The summary of evidence concerning risks (table 9.11) was also helpful.
EPA FINAL RESPONSE: No response required
As noted in the text, the sediment transport model used could only simulate sediment transport and
deposition -30 km downstream of the mine site. Thus, potential effects to fish habitats were not well
quantified for the mainstem Koktuli River (and beyond), in addition to the Mulchatna and Nushagak
rivers. Is there a likelihood that any tailings material might reach Lake Iliamna? If not, say so in the
document. It is equally useful to say where impacts will not occur (as it relates to sensitive habitat) as
it is to describe where impacts are likely and reasonable.
EPA RESPONSE: None of the 3 TSFs are in the watershed of Iliamna Lake. The hydrology of the
site has been clarified and better maps added to clarify this issue. Risks to Iliamna Lake from
water treatment failures, even if they occur in the Nushagak drainage, are now noted (e.g.,
transport of toxic leachate from the South Fork Koktuli to Upper Talarik Creek via groundwater
exchange between theses basins; Chapter 8). However, sediment (i.e., tailings) would not follow
that route.
DAUBLE RESPONSE: The new maps are a welcome addition. It was useful to learn tailings
sediments would not likely reach Lake Iliamna and that transport of toxic leachates from
groundwater exchange would be a minor pathway.
EPA FINAL RESPONSE: No response required
The assessment deemed that it was "not possible" to determine how far the initial slurry deposition
would extend, how far re-suspended sediments would travel, and how long erosion processes would
continue. It seems that information from other mine closure sites could be used by assessment
authors to infer effect by analogy. The statement alluding to potential sediment run out distance at the
bottom of page 4-56 of the main report should be included in the summary of effects. This is an
important point.
EPA RESPONSE: The revised assessment now includes a clearer description of the magnitude
and duration of effects. We apply the runout distance equations of Rico et al. (2008) to conclude
that under Pebble 2.0 scenario dam failure conditions, runout distance exceeds 307 km (190
miles), reaching the marine waters of Bristol Bay (Section 9.3.2).
DAUBLE RESPONSE: The new description is now sufficient, given the limitations of
modeling.
EPA FINAL RESPONSE: No response required
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Gordon H. Reeves, Ph.D.
Assuming that characterizations of the dam failure are accurate, the potential impacts on fish and fish
habitat are appropriate and reasonable. Impacts, like those of a pipeline failure, are likely to be
widespread in the watershed and to be long lasting, resulting from inundation of areas by sediments
and contaminants in the water. I think that potential impacts across the broader scale could be
developed and highlighted more fully. Also, consideration of Intrinsic Potential (see response to
Question 4) could provide additional insights into potential impacts of a tailings dam failure.
EPA RESPONSE: Although we were unable to conduct a full Intrinsic Potential modeling
exercise, we have quantified the distribution of classes of gradient, mean annual flow, and %
flatland for reaches of the site watersheds where TSFs would be placed As highlighted in the
report, streams - especially those downstream of the TSFs in the mainstem North Fork Koktuli
and South Fork Koktuli — are low-gradient, floodplain prone channels that currently support
spawning populations of several salmon species, rainbow trout, and Dolly Varden.
I think that potential consequences of climate change on hydrographs should have been considered in
this section. More precipitation is projected to occur as rain in the winter rather than snow for many
parts of AK. How would this potentially impact the tailings dam facilities? This seems to be a key
piece of information that is needed to better understand the risk of dam failure and the potential for
impacts on aquatic resources.
EPA RESPONSE: Climate change projections and potential impacts are described in Chapter 3,
and referenced here as a key uncertainty for in perpetuity management of the TSFs and other
mine infrastructure. The probabilities for dam failure discussed in this assessment involve dams
constructed in a variety of climates. Any potential increase in precipitation due to climate change
is but one of the conditions for which the dams would need to be designed A design developed to
handle a higher level ofprecipitation would be expected to have a similar failure probability to one
designed for an area of lower precipitation as long as the same design standards, e.g. the safety
factor against overtopping, were used in both designs. Of course, if the design did not consider the
possibility of increased precipitation as a design factor, and climate change did cause such an
increase, then the probability of failure would be higher.
I thought that results to date of the impacts of the volcanic eruption at Mt. St. Helens, while not
exactly the same as a mine operation, were not useful in considering long-term impacts and the
response of aquatic ecosystems to such major disturbances. The impacts on streams are still more
prevalent and extensive than what is described in the report. Most stream systems are transporting
large amounts of fine sediment and areas of exposed gravels are rare.
EPA RESPONSE: Extensive discussion of the Mount St. Helens analogy has been removed at the
prompting of several reviewer comments including this one. We have retained key references from
the region that are illustrative for considerations of likelihood offine sediment transport and
recovery (or lack thereof).
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Charles W. Slaughter, Ph.D.
Yes. Physical consequences of TSF dam failure are fairly portrayed. I would only suggest that
effects of initial sediment deposition and long-term remobilization and redeposition would extend
beyond the spatial and temporal limits of the modeling used in the Assessment.
EPA RESPONSE: Agreed. We now more clearly state that remobilization and deposition could be
extensive; potentially reaching Bristol Bay.
SLAUGHTER RESPONSE: I concur that the revised Assessment provides a much better
characterization of potential TSF dam failure. The difficulties with quantitatively analyzing
sediment deposition and remobilization further downstream are appreciated.
EPA FINAL RESPONSE: No response required
Employing advanced eco-hydraulic modeling tools such as MIKE-11, MIKE-SHE (DHI,
Copenhagen), and consultation with state-of-art practitioners (IAHR-International Association for
Hydraulics Research, UI Center for Ecohydraulics Research, and others), along with improved high-
resolution input data such as LIDAR survey of the complete Kvichak and Koktuli/Nushagak systems,
would allow a more complete estimate of potential hydrologic and sedimentation (and consequently
biotic) consequences of TSF dam failure for the entire river system, headwaters to Bristol Bay.
EPA RESPONSE: We agree that LIDAR survey data would greatly improve the understanding of
the project area topography. Alternative modeling platforms coupled with LIDAR have the
potential to improve the estimates provided in this assessment, but these data collection and
modeling efforts were not within the scope of this project.
SLAUGHTER RESPONSE: Understood - your mandate was not to do such field work and
subsequent analysis, which takes a lot of time, expertise, dollars, and advanced modeling
capabilities. Such an effort could be a future task as the project (potentially) moves forward.
EPA FINAL RESPONSE: No response required.
John D. Stednick, Ph.D.
The tailings dam failure was modeled and the distance of sediment transport was estimated. The
modeled tailings dam failure used an estimate of 20% mobilization from the tailings ponds. How was
this value determined? The model was run to a stream length of 30 km (the rivers confluence), yet
the report acknowledges that a sediment pulse could run for hundreds of kilometers. The moisture
content of the tailings is estimated to be 45% by volume (page 4-50); the 20% volume of sediment
may be underestimated. This initial risk to salmonid fish is clear, but the persistence of the sediment
affect could be discussed.
EPA RESPONSE: 20% was selected as a reasonable estimate, falling within the range of historic
failure release volumes (e.g., Azam and Li 2010 state 1/5 (i.e., 20%) and Dalpatram 2011 states 20-
40%). We agree that the total volume released during a failure would vary depending on water
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content, consolidation of tailings, and meteorological conditions in the valley during the time of
the failure. We also agree that the sediment initially deposited on the valley floodplains and the
sediment that remains downstream of the failed dam would become a continuous source of
tailings, with the potential to re-suspend during each subsequent rainfall-runoff event that occurs
before any sort of mitigation/clean-up efforts could be implemented to control this process. The
20% used was based on recent literature for the amount that is generally released from these types
of dam failures. The tailings dam failure was intended to be a conservative analysis to shed light
on whether a failure is a significant concern in the Nushagak River watershed
The Mount St. Helens analogy is inappropriate for a variety of reasons and such comparisons should
be removed from the assessment.
EPA RESPONSE: Use of the Mount St. Helens analogy has been removed.
The probable maximum precipitation (PMP) value was extrapolated from Miller (1963) and the
assessment commented how this value might be reduced upon further analysis. Conversely,
additional data could increase this value. There was no discussion of the recurrence interval of this
24-hour storm.
EPA RESPONSE: The assessment used the published PMP from Technical Paper No. 4 7 (the
current guidance available from NOAA, at www. mvs. noaa.gov/oh/hdsc/studies/pny). html). Within
TP 47 the 24- hour PMP values presented exceed those provided for the 100-year 24-hour event.
While actual planning, design, and construction of a TSF dam will require additional study, for
the purposes of this assessment we relied on readily available information and current published
guidance for the determination of a design storm event with the magnitude that would likely be
considered during design of the dam The published PMP was applied to a Type-1 storm within
HEC-HMS to determine a flood hydrograph that would result in the watershed located above the
TSF as described for the purposes of this assessment. This hydrograph is expected to peak at 291
cms and was applied to the hydraulic model to cause an overtopping and subsequent failure of the
TSF dam The flood wave generated by the dam failure had a peak flow of149,263 cms and
11,637 cms (large and small dam failures respectively). The hydrology discussed and applied
related to the dam failure represents a precipitation and runoff event of the magnitude that the
dam would be expected to accommodate, but in this assessment was used as a mode of failure.
EPA FINAL RESPONSE: In the final assessment, flooding to generate overtopping is no longer
simulated.
No hydrologic data were provided. The streamflow gauging stations operated by the US Geological
Survey near the study area suggest peak streamflow rates from snow melt and from rain events. The
hydrograph shape and magnitude help determine if rain or snowmelt dominated. In the assessment,
the peak flow estimate from the Natural Resources Conservation Service runoff method used a Type
la storm distribution, the least intense precipitation distribution, but the literature would suggest that
a Type 1 distribution would be more appropriate for Alaska. How does this storm event compare to
the measured flood at Ekwok (page 4-50)? The curve number (CN) was not identified, nor the
methods used to calculate that value. Similarly, the watershed slope, time to peak, hydraulic length,
channel routing functions, and channel resistance methods or results were not presented. What
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precipitation data are available? The design of culverts, bridges, and storm water ponds all require
good precipitation records and the confidence in that estimate is based on record length.
EPA RESPONSE: We agree that the Type-1 storm is appropriate for Alaska. This has been
corrected and updated. Additional hydrologic parameters were also included in the update to better
describe the development of the HEC-HMS model. It is important to note that this hydrologic
event was used to provide a mode offailure for the dam. The flood wave generated by the dam
dwarfs the PMP hydrograph and the runoff from the storm event is not relevant.
EPA FINAL RESPONSE: In the final assessment, flooding to generate overtopping is no longer
simulated.
The comparison is unclear for a 3,313 nrVs flow in a 2,551 km2 watershed area to the TSF flow of
1,862 m7s and an area of 1.4 km2. What was the precipitation and recurrence interval for the Ekwok
storm? The relation of groundwater flows to streamflow during storm events needs to be evaluated.
The flood producing precipitation events in this area no doubt add to groundwater flows.
EPA RESPONSE: This discussion was provided to help the reader understand the magnitude of
the dam failure flood wave relative to an event that was experienced by a local community. We
also wanted to draw attention to the fact that such a failure would occur in the upper end of the
watershed where typical storm events do not generate floods of such magnitude. We acknowledge
that the two watersheds are not similar and the intent was not to draw comparisons of runoff
potential from one watershed to another, just to help the reader gain context.
EPA FINAL RESPONSE: In the final assessment, flooding to generate overtopping is no longer
simulated.
With a new estimate of precipitation depth of known recurrence interval, the design storm could
result in a higher flood event with greater velocities and greater sediment transport ability, along with
a greater sediment volume released from the TSF, resulting in a greater risk to salmonid fish and
habitats.
EPA RESPONSE: We agree. The tailings dam failure was intended to be a conservative analysis
to shed light on whether a failure would be a significant concern in the Nushagak River
watershed No change suggested or required.
Roy A. Stein, Ph.D.
TSF Failure and Remediation. The text on pages 6-1 to 6-2 states:
"Remediation may occur following a tailings spill, but it is uncertain. A spill would
flow into a roadless area and into streams and rivers that are too small to float a
dredge, so the proper course of remediation is not obvious."
At this juncture in time, this statement points to the fact that we do not have the technology, or the
appropriate operating procedures, in place to remediate a TSF spill. Does this essentially let the mine
operator "off the hook"? Should we be promulgating mining activities in locations where we cannot
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remediate spills, given our current state of knowledge or ability to apply current techniques? What
guidance would "Best Management Practices" provide for this situation?
EPA RESPONSE: The intent of the statement is to point out the challenges of remediation of a
large-scale tailings spill in a remote area. Large-scale tailings cleanup is challenging even in
urban and more developed rural areas where there is road/rail access for equipment and transport
of contaminated sediment. In the assessment watersheds, the only current access to downstream
areas is provided by the rivers themselves, which are generally too small for large-scale dredging
equipment.
William A. Stubblefield, Ph.D.
Potential effects on salmonid populations were evaluated due to tailings dam failures. Tailings dam
failure would potentially result in the release of large volumes of mine tailings and associated
contaminated waters, leading to possible acute and long-term effects on salmon populations. It is also
important to note that direct effects on salmon may be very species dependent, due to life-cycle
differences, and the time at which the dam failure occurs. Potential effects due to sediment
inundation/impaction can adversely affect habitat, leading to decreased spawning. Evaluation of the
potential for tailings dam failure effects considered acute and chronic risks due to aqueous exposures,
chronic risks due to sediment exposures, and risks due to dietary exposures. All of these seem to be
appropriate exposure pathways and all were adequately considered, although site-specific
information will improve risk predictions.
EPA RESPONSE: Agreed. No change suggested or required.
STUBBLEFIELD RESPONSE: No additional comments are provided.
EPA FINAL RESPONSE: No response required
Dirk van Zyl, Ph.D., P.E.
The EPA Assessment does not identify or appropriately characterize the risks to salmonid fish due to
a potential tailings dam failure. It only estimates the likelihoods of occurrence and the consequences.
See discussion under Question 4 above regarding suggestions for improving estimation and
expression of the magnitude of risks to salmonid fish due to potential tailings dam failure.
EPA RESPONSE: We believe that the likelihood of an occurrence and its consequences constitute
an appropriate and generally accepted definition of risk. In this case we have estimated those for a
tailings dam failure to the extent that existing information allows. Although fish abundance data
are limited for this region, we did identify the potential magnitude of a tailings dam failure to the
Chinook run of the Nushagak River.
TSF failure likelihood. The failure statistics given on p. 4-45 are based on tailings failure statistics
over the last 50 years or so. Was there also a review of the operational histories, and therefore
failures, of tailings impoundments designed and constructed in the last 10 to 15 years? It is
recognized that one of the failures identified in Box 4-4 (Aurul S.A. Mine, Baie Mare, Romania) falls
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in this category. However, many of the failures included in the analyses are associated with older
tailings facilities, especially those associated with large releases of tailings solids. A significant
improvement in tailings management is the implementation of an Independent Tailings Dam Review
Board (ITRB) for large mining projects (Morgenstern, 2010). An example of the activities of an
ITRB is given in Minera Panama (2012). Morgenstern (2010) provides a listing of tailings failures
from 2001 and 2010 and comments that "in no case, to the knowledge of the Writer, was there
systematic third party review" of the failed facilities as would be the case when an ITRB is active. I
expect that a tailings review board will also be used for the Pebble Mine and the behavior of a
tailings management facility designed and operated under these conditions will be more
representative of the potential failure likelihoods expected for such a facility. It is expected that this
likelihood will be much lower than those used in the evaluations of the scenario in the EPA
Assessment.
EPA RESPONSE: The probabilities for dam failure used in the assessment were not derived solely
from the historical record Historical failures were discussed as supporting background
information and present a defensible upper bound on the failure probabilities. The failure
probabilities used in the assessment are based on Alaska's dam classification and required safety
factors applied to the method of Silva et al (2008) which compares dams designed, constructed,
and/or operated under different standards. The discussion of failure probabilities in the revision
(Chapter 9) is expanded to try to clarify this issue.
TSF failure consequences. It is difficult to estimate the volume of tailings that will be released when
a tailings impoundment fails. The release of 20 percent of tailings from a slurry deposited TSF may
be realistic when it contains a large pool and is subjected to a large flood, but it is unrealistically high
for a TSF containing a small or no pool (such as in the case of a filtered dry stack). I would consider
the assumption that a release of 20% of the tailings material for the Pebble mine scenario is on the
high side, even during operations. When the mine is closed and the tailings reclaimed I would
consider the 20% release assumption as unrealistic, especially if the closure implementation included
a diversion system designed for the PMF. It is further unrealistic to assume that the released tailings
will remain in the downstream channels and flood plains following the failure. In the case of the
Aznalcollar Tailings Dam failure in Spain, all the released tailings downstream of the mine were
removed. While such a removal action will impact parts of the watershed, it will help to recover the
area faster than leaving all the tailings in place and will also reduce the longer-term impacts on
downstream water quality. I therefore disagree with the assumption on p. 6-2 that "the assessment
assumes that significant amounts of tailings would remain in the receiving watershed for some time
and remediation may not occur at all." Box 6-1 provides "background on relevant analogous tailings
spill sites" and three historic sites are used as analogs. These are not realistic analogs, as they all
relate to historic mining under completely different scenarios. While the material historically released
in these streams were from base metal mines, the circumstances of their release, especially in the
case of the Clark Fork and the Coeur D'Alene Rivers, were very different. Long-term uncontrolled
releases occurred in these river systems due to regulatory circumstances or historically acceptable
practices that differ significantly from those in the 21st Century.
EPA RESPONSE: We concur with the commenter that the estimation of the potential release
volume is difficult and inexact. The release of 20% of impounded tailings used in our analysis is
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well below the reports of 30% to 66% in the historic record. Dry stacking was not proposed in the
Ghaffari et al. (2011) report and has not been proposed in our scenarios. Ghaffari et al. (2011)
proposed maintaining a pond on the top of the TSF to keep the pyritic tailings submerged,
implying that the bulk of the tailings would remain saturated. We acknowledge that there are other
tailing management strategies that could reduce the potential risk of failure.
The remediation of the 1998 Aznalcollar Tailings Dam failure in Spain was completed within the
6 months between the April failure and the onset of heavy rains in October. The Aznalcollar area,
near Seville, has a much drier and warmer climate than the Bristol Bay area. It is also a heavily
farmed area with flatter topography and far better access. The success at removing the tailings
from the Aznalcollar failure would be difficult to replicate in the Bristol Bay area, and significant
amounts of tailings would remain in the receiving watershed for some time.
Box 6-1 in the original draft assessment (now Box 9-1) clearly states that the analogs presented
"provide evidence concerning the nature of exposures to aquatic biota". They are not used to
address the probability of a tailings dam failure or other aspects of the release of tailings.
VAN ZYL RESPONSE: No further comments on Question 9.
EPA FINAL RESPONSE: No response required
Phyllis K. Weber Scannell, Ph.D.
The assessment considers two possible failures of the tailings dam: a partial-volume failure occurring
during mine operations and a catastrophic failure occurring during or after mine operations. The
partial-volume failure (as modeled in the assessment) would result in a greater than 1,000-fold
increase in discharge and the catastrophic failure in a greater than 6,500-fold discharge.
EPA RESPONSE: No change suggested or required.
WEBER SCANNELL RESPONSE: The reviewer agrees that no change is required.
The reviewer agrees that this comment has been adequately addressed.
EPA FINAL RESPONSE: No response required.
The discussion of tailings dam failures describes possible changes in channel and floodplain
morphology and briefly mentions that the tailings deposition would be a source of easily
transportable, potentially toxic material.
EPA RESPONSE: No change suggested or required.
WEBER SCANNELL RESPONSE: The reviewer agrees that no change is required.
The reviewer agrees that this comment has been adequately addressed.
EPA FINAL RESPONSE: No response required.
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The potential for increased metals loadings to river and lake systems is understated. Although there
are no current predictions of tailings water quality, the water quality of tailings water from similar
mines could be used to model increases in metals loading from dam failures.
EPA RESPONSE: The original draft and the revised assessment use tailings leachate data from
the PLPEBD (see Chapter 8). We believe that is more defensible than use of tailings leachates
from other mines.
WEBER SCANNELL RESPONSE: The reviewer agrees that no change is required.
The reviewer agrees that this comment has been adequately addressed.
EPA FINAL RESPONSE: No response required.
In addition to the partial-volume failure and the catastrophic failure, there are other possible sources
of metals loadings from the tailings pond. Examples are emergency releases of untreated tailings
water, seepage of tailings water into the groundwater, and flow from the tailings pond to groundwater
in an adjacent drainage as the head (i.e. hydrostatic pressure) is increased as the tailings pond is
filled. The last example was experienced at the Red Dog Mine when the increased elevation of the
tailings pond caused water to flow underground into the Bonns Creek drainage instead of the Red
Dog Creek drainage. Interception ditches were installed after the increases in metals loading to
Bonns Creek were detected.
EPA RESPONSE: Because the number ofpotential failures is extremely large, it is necessary to
choose a representative set offailure scenarios. The original and revised drafts of the assessment
include "seepage of tailings water into the groundwater, and flow from the tailings pond to
groundwater in an adjacent drainage" but not emergency releases of tailings water.
WEBER SCANNELL RESPONSE: The reviewer is satisfied.
The reviewer agrees that this comment has been adequately addressed. The reviewer notes that
sections on potential failures have been expanded. The current draft contains much valuable
information that is presented in a clear and defensible way.
EPA FINAL RESPONSE: No response required.
Paul Whitney, Ph.D.
Duration. I agree with the assessment that it would take a "very long time" (page 6-25, first full para,
last line) to reach concentrations that would not exceed threshold exposure levels. A "very long time"
could mean hundreds of years to one person or geological time (i.e., millions of years) to another
person. The assessment could be improved if some sidebars are put on the time likely required for no
risk dilution or "more normal channel and floodplain." One suggestion would be to estimate the
amount of time it would take the river/stream to move across the floodplain in the "relatively
undisturbed" Bristol Bay watershed. I would also like to know whether reclamation or rip rap or rock
weirs in areas with spilled tailings would reduce or extend the time to reach "more normal"
conditions.
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EPA RESPONSE: We agree that geomorphic analyses of channel/floodplain recovery following a
TSFfailure would help improve the estimation of recovery time, but such an analysis would be a
research and development effort beyond the scope of this assessment. Analogous examples of
recovery following massive contributions of sediment to stream systems were explored (e.g., Mount
St. Helens) but were not uniformly valued by reviewers, and were dropped from the assessment.
3.12 Charge Question 10
Does the assessment appropriately characterize risks to wildlife and human cultures due to
risks to fish? If not, what suggestions do you have for improving this part of the
assessment? Are significant literature, reports, or data not referenced that would be useful
to characterize these risks, and if so what are they?
David A. Atkins, M.S.
The assessment does a good job analyzing the importance of fish resources to other wildlife and to
Alaska Native communities. The lack of site-specific information in the report results in only very
general conclusions that there 'would be some effect.' Of course, wildlife in the project area and any
traditional use of these lands would be affected by project construction under the no-failure scenario.
However, due to the lack of information, it is unclear if this is an area rich in other wildlife or if there
are traditional native land users that rely on the area. Although the conclusion of this section is
necessarily general, it would be helpful to have more detailed characterization of wildlife and native
use in the project area.
EPA RESPONSE: More information about subsistence harvest use in the area of the mine
scenarios and other areas of the watershed that may be affected by mining activities has been
added to the report. Because the scope of the assessment includes potential effects to Alaska Native
communities related to salmonids, this has been the focus of the evaluation ofpotential effects on
indigenous cultures. However, EPA recognizes that there are potential effects due to loss of
subsistence harvest areas for other species, as well as potential effects on non-Alaska Natives who
practice a subsistence way of life. This is clarified in the revised assessment (particularly in
Chapters 12 and 13).
As the conmienter notes, there is limited information about the use of specific mining claim areas
by wildlife. The Pebble Limited Partnership Environmental Baseline Data Report includes data on
the presence/absence of wildlife species around the Pebble claim, but we are not aware of any data
on abundance of wildlife, so a more detailed characterization of a specific mine claim area may
not be possible. There is some information about subsistence use of the mining claim areas which
has been published by Alaska Department of Fish and Game. General areas of wildlife harvests
have been added as a figure to the revised assessment.
ATKINS RESPONSE: This response is adequate.
EPA FINAL RESPONSE: No response required.
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Under the failure scenario, a tailings dam failure, in particular, would be catastrophic for wildlife and
Alaska Native communities that use the area.
EPA RESPONSE: A new Figure 5-2 illustrates that subsistence use of fish is extensive in areas
downstream of the TSF in the Mulchatna and Nushagak Rivers, and this fact is now referenced.
Effects of a TSFfailure on wildlife are now discussed in Section 12.1.
ATKINS RESPONSE: This response is adequate.
EPA FINAL RESPONSE: No response required.
Steve Buckley, M.S., CPG
No comments on this section.
Courtney Carothers, Ph.D.
Wildlife: The sections discussing risk to wildlife resulting from effects on salmonids are fairly short.
Those animals that directly feed on these fish are likely to be impacted, as well as those that depend
on other resources enhanced by the marine-derived nutrients supplied by salmon carcasses. The
report concludes that the primary aquatic contaminant is copper (5-75), but notes that the ore
processing chemicals are unknown, as are their toxicities (5-59). These unknowns could be noted as
potential contaminants.
EPA RESPONSE: Section 8.2.2.5 now includes a discussion of ore processing chemicals and their
toxicity.
Human cultures: Overall, the main report (and Appendix D) describes the central role that salmon
play in both Yup'ik and Dena'ina culture, both traditionally and in contemporary communities. As
noted above, the scope of the assessment focusing on these two cultural groups should be made more
clearly. Appendix E, for example, focuses on other human groups local to this region, and those who
migrate to the region for commercial fishing and recreation, who may also be affected by risk to fish
in this region. The vulnerabilities listed in Appendix D (p. 4-5) could be listed in the main report
more clearly as risks.
EPA RESPONSE: The assessment text has been expanded to identify these vulnerabilities.
Literature on the effects of contaminated or declining resources on subsistence communities could be
utilized to describe likely impacts in more detail. For example, the report notes: "the actual
responses of Alaska Native cultures to any impacts of the mine scenario is uncertain" (ES-26). While
the specific responses are uncertain, likely responses can be predicted (and many are articulated in
Appendix D). There are data on the psychological, social, cultural, and economic disruptions caused
by the Exxon Valdez oil spill (e.g., Braund and Kruse 2009; Palinkas et al. 1993), the cumulative
effects of oil and gas development in the North Slope region (e.g., Braund and Associates 2009; NRC
2003), and social impacts related to mining development in Alaska (e.g., TetraTech 2009; Storey and
Hamilton 2004). Drawing on some of this literature could help provide likely scenarios for impacts to
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Alaska Native subsistence-based communities from decreased quality, quantity, or diversity of
salmonids. Current and recent responses to salmon shortages in the Yukon-Kuskowkim region may
also be helpful to include.
EPA RESPONSE: The references provided have been reviewed and information from case studies
used where appropriate to provide data on responses of Alaska Native communities to disruptions
in subsistence resources (see Chapter 12).
Clearly the impacts to subsistence are not just lost food sources, but loss of healthy subsistence
lifeways, loss of practices, loss of cultural connections to the past, loss of connection to specific
places, loss of teaching and learning, loss of sharing networks, loss of individual, community, and
cultural identity, among others as detailed in Appendix D. This point could be made more forcefully.
As noted above and detailed in the specific comments below, subsistence is framed at times in the
report as primarily important for physical health and economic necessity. The cultural, social,
psychological, and spiritual aspects of subsistence livelihoods should also be consistently
highlighted.
EPA RESPONSE: The assessment has been expanded to bring forward more information on the
psychological, cultural, social, and spiritual connections between Alaska Native cultures and fish.
As discussed Appendix D, Alaska Native cultures in this region and other regions in the state are also
dependent upon the cash economy, both for subsistence production and for other needs. The role of
commercial salmon fishing or other wage engagements related to salmon in the study communities,
while discussed in Appendix E, is not given much discussion in the main report. How dependent is
the subsistence economy upon commercial and recreational fisheries and in this region?
EPA RESPONSE: Additional information about the connections between the subsistence way of
life and the commercial and recreational fisheries has been added to the text of the revised
assessment.
There is a brief mention of non-fish related impacts to Alaska Native communities in the main report
(5-77). Unless a full treatment of these impacts (positive and negative) is included, these paragraphs
should be removed. While in general, I am supportive of an increased scope (i.e., it is incredibly
difficult to isolate only salmon-mediated impacts to Alaska Native communities), these other
economic, social, and cultural impacts are not presented fully in the analysis, nor was the
ethnographic research designed to investigate these impacts, so passing mention of them here does
not seem appropriate.
EPA RESPONSE: The text of the assessment has been clarified to indicate the scope of the
assessment does not include an evaluation of direct effects on indigenous culture or human
welfare, because it is limited to aquatic pathways and impacts. However, the fact that there would
be direct effects is acknowledged in Chapter 12, consistent with comments from peer reviewers and
the public.
CAROTHERS RESPONSE: While the EPA Response notes that additional discussion of the
connections between subsistence and commercial fishing in this region has been added to the
report, I did not find much evidence of these additions. One instance of this addition in the
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Revised Assessment includes a short paragraph (5-36) only briefly mentioning these
connections. Chapter 5, Section 5.4, for example, could include a discussion of Alaska Native
engagements in, and dependence on, commercial fishing and fish-related tourism businesses in
the region. Similarly, Chapter 12, Section 12.2 could include a section that discusses how
decreased commercial fishing and tourism opportunities would affect Alaska Native
communities and cultures. Some of this information is contained in Appendix E and could be
brought forward into the main body of the report.
As noted above, the report makes clear the scope of the assessment of human impacts is limited
to fish-mediated effects. However, the EPA Response notes that Chapters 5 and 12 have been
expanded to acknowledge the range of direct and indirect impacts of mining to human cultures
and communities. At times, there is some slippage between the defined scope and the partial
inclusion of direct impacts. For example, the list of salmon-mediated effects on Alaska Natives
(section 12.2, p 12-6) lists a direct effect of mining on social systems ("a shift from part-time to
full-time wage employment in mining or mine- associated jobs would affect subsistence
gathering capabilities by reducing the time available to harvest and process subsistence
resources.") This is not a salmon-mediated effect, but a direct effect of mining. I agree that
these direct effects are highly important to consider and deserve acknowledgement and
discussion in the report. However, because the scope has been narrowly defined as salmon-
mediated effects, the interspersing of some direct effects into sections that describe salmon-
mediated effects calls into question this focus. As stated above, the discussion of direct effects
could be contained within separate sections in Chapters 5 and 12. These sections should
reiterate that a full treatment of these direct effects is outside of the scope of this assessment,
and as such the abbreviated discussions are necessarily cursory and incomplete. Given the
number of public comments that focused on direct effects, this clarification and
acknowledgement is appropriate and may be less confusing if placed in separate sections within
the report.
EPA FINAL RESPONSE: Additional information from and references to Appendix E regarding
local employment in commercial fishing and recreational sectors have been added to Chapter 5.
Chapter 12 now acknowledges the potential effects of decreased commercial fishing and tourism
opportunities on Alaska Native communities. A new text box (Box 12-1) has been added to
Chapter 12 to briefly discuss direct effects and better differentiate them from indirect, or salmon-
mediated, effects.
Dennis D. Dauble, Ph.D.
There is considerable detailed information in Appendices D and E relating to impacts of the project
to the economy. This information includes how salmon affect all segments of the population, such as
cultural resources of Native Peoples. However, not addressed in detail were long-term impacts to
Native Peoples that might occur after losing a way of life that includes salmon. The description of
potential impacts to their health and welfare should be expanded. There are numerous examples of
how Columbia River tribes have been negatively impacted due to loss of fish resources (and fishing
as a lifestyle) as a result of dam construction. These impacts go beyond simple economics.
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EPA RESPONSE: We recognize that there is a great deal of information about cultural and
health effects on indigenous populations from loss offish resources. We have referenced some
case studies in the assessment (with a primary focus on Alaska), and have expanded the discussion
ofpotential effects from a loss of salmon resources in Chapter 12.
DAUBLE RESPONSE: The case studies are helpful. I agree that Alaska's native peoples are a
unique situation.
EPA FINAL RESPONSE: No response required.
The report should include a discussion of effects specific to unique user groups. That is, some
communities rely almost solely on sockeye; kings are more important to others. These impacts could
be segregated by watershed, for example. Also, some groups have more option for subsistence
gathering if sockeye and Chinook salmon resources are impacted. Potential impacts of a declining
salmon population due to mining operations would be less for them than groups "on the edge" who
currently rely mainly on salmon.
EPA RESPONSE: The text of the draft assessment (Section 5.4.2.2) has been expanded to
acknowledge the differences between communities with regard to use and reliance on salmon and
other fish resources.
DAUBLE RESPONSE: Although text was revised in Chapter 5 to acknowledge differences in
reliance between Chinook and sockeye salmon, these differences were not brought forward to
risk assessment discussions in Chapter 12. Discussion in section 12.2.3 should address the
declining state of economy for some upper watershed cultures and specify which resident group
expressed a desire for jobs and development.
EPA FINAL RESPONSE: Based on public comments, support for economic development related
to large-scale mining is not limited to the upper watershed cultures, and many residents in the
upper watershed have expressed concerns about environmental and social consequences of large-
scale mining. Therefore, we have added comments from those supporting economic development
related to mining into Box 12-2 (Box 12-1 in the previous draft), but have not associated this
support to any one region.
Disturbance of wildlife from noise and roadways should be included with respect to migration
corridors and critical habitat. Highlight species most likely at risk from human disturbance, habitat
loss/displacement (from the project footprint), and loss of salmon. For instance, do some piscivorous
species have the ability to shift their diet to include another source of protein? If so, how would this
shift affect the human culture with reference to a subsistence lifestyle?
EPA RESPONSE: We recognize that there are potential direct effects on wildlife from large-scale
mining operations, including disturbances from noise and roadways; however direct effects on
wildlife are outside of the scope of the assessment, as explained in Chapter 2. We would expect
that a full evaluation of any future mining permit applications and subsequent National
Environmental Policy Act Environmental Impact Statements would consider these direct effects on
wildlife.
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DAUBLE RESPONSE: It would be informative (and in my opinion within the scope of the
assessment) to include additional narrative text on wildlife species having the greatest
dependency on salmon as a prey base.
EPA FINAL RESPONSE: Box 5-3, which considers the role of salmon in terrestrial and aquatic
food webs, has been added to the final assessment. There is also additional narrative text in
Appendix C describing those wildlife species that have strong connections to salmon.
Gordon H. Reeves, Ph.D.
These topics are outside my area of expertise so I cannot comment on if the report adequately
characterizes the risk to wildlife and human cultures. I am familiar with some of the literature on the
importance of salmon to wildlife and the report represents the finding fairly and accurately. I cannot
provide any additional literature, reports, or data.
EPA RESPONSE: No change suggested or required.
Charles W. Slaughter, Ph.D.
No. The Assessment clearly qualified that its objective was to consider risks to salmonids, and only
inferentially consider "salmon-mediated" effects.
EPA RESPONSE: No change suggested or required.
SLAUGHTER RESPONSE: The revised Assessment does provide a better consideration of
both wildlife and human culture aspects - at least in part in response to other review comments
on the first draft. Sections 12.2 and 12.3 are succinct summaries, which should be considered
by all decision makers regarding this or other "development" proposals. The final bullet of p.
12-17, thought it might have been re-worded, appropriately states that mitigation for lost
subsistence resources or cultural values is not feasible.
EPA FINAL RESPONSE: No response required.
Appendix C provides a comprehensive discussion of non-fish wildlife and the relation of those
populations to salmon. However, the Assessment itself (Volume 1) provides only a brief summary in
Chapter 2.2.3, which could allow a cursory reader to perhaps conclude that wildlife populations have
little risk of impact from the hypothetical Pebble project. Is this the intent of the Assessment authors?
A more in-depth reading of Appendix C allows inferring potential consequences to wildlife and birds
of "salmon-mediated" impacts of mining development.
EPA RESPONSE: We have clarified assessment endpoints and provided additional background
information from Appendices A and B in Chapter 5. Direct effects on wildlife are outside the scope
of the assessment (as stated in Chapter 2), but their potential importance is acknowledged in
Chapter 12.
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The assessment has been expanded to include more information from Appendix C of the draft
report (now an independent U. S. Fish and Wildlife Report).
The scope of the assessment is focused on potential risks to salmon from large-scale mining and
salmon-mediated effects to indigenous culture and wildlife. EPA recognizes the complexity of
potential direct, secondary, and cumulative effects on wildlife. We would expect that a full
evaluation of any future mining permit applications and subsequent National Environmental
Policy Act Environmental Impact Statements would consider these complexities and utilize the
information in U.S. Fish and Wildlife report (Appendix C of the draft report.)
USFWS RESPONSE: We acknowledge the comment about the comprehensive discussion of
wildlife and the relation of selected species to salmon in Appendix C. Appendix C could be used as
the basis of an assessment ofpotential impacts of mining on wildlife, but decisions related to
assessment scope with regard to potential impacts of mining on wildlife is the responsibility of
EPA.
SLAUGHTER RESPONSE: OK. Inclusion of these materials in the body of the Assessment,
rather than simply in an Appendix, strengthens the document.
EPA FINAL RESPONSE: No response required.
Appendix D provides a comprehensive and useful discussion of the indigenous people of the Bristol
Bay region and of their traditional ecological knowledge and cultures. Appendix D clearly lays out
the vulnerabilities and risks (summarized on p. 4-5 and pp. 150-153) associated with the
(hypothetical) major resource extraction projects. However, the Assessment (Volume 1) provides
only cursory consideration of these human aspects of the potential project - on p. ES-23, and in
Section 2.2.5. Presumably, this is because the EPA mandate is to conduct an ecological risk
assessment, rather than assessment of consequences for human populations, whether indigenous,
native, resident, non-native, non-resident, or the larger cash economy world as represented by the
State of Alaska, Northern Dynasty Minerals, or Pebble Limited Partnership.
EPA RESPONSE: The scope of the assessment related to Alaska Native cultures is limited to
salmon-mediated effects—that is, potential effects on indigenous culture if there are negative
effects on salmon. The assessment draws on the more comprehensive information in Appendix D
to evaluate these risks. The text of the revised assessment has been expanded to include and
discuss the vulnerabilities and risks to Alaska Native culture from potential large-scale mining.
SLAUGHTER RESPONSE: OK. The revised text in Sections 12.2 and 13.4.2, while brief, do
add substance to the Assessment. (I make the assumption that the original Appendices A-H are
still a part of the overall Assessment.)
EPA FINAL RESPONSE: Appendices A through J are part of the assessment. No response
required.
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John D. Stednick, Ph.D.
The effect on wildlife section largely focuses on the return of nutrients to the land in various shapes
and forms and adds little to the risk discussion. Other than marine-derived nutrients, other stressors
exist. What are the consequences of the mine operation on other wildlife habitats? Habitat
fragmentation? Noise and light disruptions, etc.?
EPA RESPONSE: The scope of the assessment is focused on potential risks to salmon from large-
scale mining and salmon-mediated effects to indigenous culture and wildlife. EPA recognizes the
complexity of potential direct, secondary, and cumulative effects on wildlife and would expect that
a full evaluation of any future mining permit applications and subsequent National
Environmental Policy Act Environmental Impact Statements would consider these complexities.
The final assessment acknowledges the potential for direct effects on wildlife (Chapter 12).
Mine development will require the use of explosives. What are the effects of the nitrate and ammonia
in the air following each detonation? The National Trends Network data suggest that the area
receives about 1 kg/ha/yr of nitrogen in precipitation. Thus, the increase in atmospheric inputs from
the explosions may exceed the marine-derived nutrients. What are the consequences?
EPA RESPONSE: See response to previous comment. Also, stressors evaluated were based on
how they would significantly affect our primary endpoint of interest (the region's salmon
resources) and their relevance to EPA's regulatory authority and decision-making context.
Although atmospheric inputs from mining operations are a potential source of contamination to
streams, they are not considered as significant as other stressors and are not regulated under the
Clean Water Act. Finally, because of terrestrial nitrogen fixation, nitrogen is not believed to be the
most important marine derived nutrient.
The potential loss or change in lifestyles of indigenous peoples is important, but this information
seems relegated to Appendix D. Include more of this information in the main body of the text.
Actually, there is a significant amount of information in the appendices that should be brought
forward.
It is unclear why there is such variability in the detail or depth of assessment of each of the stressors.
Why does the TSF failure section have 34 pages while the section on potential effects on native
peoples only has a few pages with a reference to an appendix? The unevenness of the coverage
needs to be addressed.
EPA RESPONSE: The text of the revised assessment has been expanded to incorporate more of
the background information from Appendix D and a more comprehensive evaluation ofpotential
salmon-mediated risks to indigenous culture. The assessment's primary endpoint is the abundance
and production of salmonid fish, so effects on those receptors are treated in more depth than the
secondary endpoints,fish-mediated effects on wildlife and Alaska Native cultures.
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Roy A. Stein, Ph.D.
Risks to Wildlife. The importance of salmon in bringing Marine Derived Nutrients (MDN) into
these freshwater ecosystems and watersheds and their role in influencing wildlife and associated
interactions between wildlife and human cultures was well described. Loss of these nutrients would
severely compromise wildlife, and thereby human (through reductions of subsistence harvest),
populations. The appendix dealing with wildlife was quite detailed and well done and it would serve
the main report well for the authors to include critical information from this appendix.
EPA RESPONSE: No change suggested or required.
USFWS RESPONSE: We acknowledge the comment regarding the quality of Appendix C.
Comments related to the scope of the assessment are not specific to Appendix C and are the
responsibility of EPA.
Risks to Native Alaskan Culture I. I thought that the assessment could be approved if the same
approach used for the mine, i.e., a case history approach, was used for human cultures. Surely,
there exist situations where salmon have declined or have been reduced by
development/exploitation (the Fraser River, perhaps?) where subsistence by Native Alaskans
was historically paramount. Once the salmon were reduced, what was the impact on the Native
Alaskans subsistence culture? How did the Native Peoples respond? From whence did they get
sustenance, cash, etc.? What sort of displacement occurred?
EPA RESPONSE: We recognize that there is a great deal of information about cultural and
health effects on indigenous populations from loss offish resources. We have referenced some
case studies in the assessment (with a primary focus on Alaska), and have expanded the discussion
ofpotential effects from a loss of salmon resources.
Risks to Native Alaskan Culture II. The only risks reviewed here came via salmon-mediated
impacts on the culture of Native Alaskans. Direct impacts of the mine through jobs (potentially
positive), wildlife (likely negative), etc. all could be discussed briefly, serving to broaden the overall
impact of the mine and its associated activities on Native Alaskans.
EPA RESPONSE: We acknowledge that the scope of the assessment is limited to salmon-mediated
risks to indigenous culture and that there would be many other potential effects (positive and
negative) from development of large-scale mining in the region. Direct impacts to Alaska Native
culture have been acknowledged in the revised report, but are outside of the scope of the
assessment.
Risks to Other Cultures. I was a little surprised that little text was spent on recreational anglers,
commercial fishers, subsistence users (other than Native Alaskans), etc. Appendices provide some
guidance here and this text need not be voluminous, but mentioning these impacts of the mine on
these groups would improve the main report.
EPA RESPONSE: The discussion in the revised assessment has been expanded to acknowledge
potential effects on non-Alaska Native subsistence users. We acknowledge that there are potential
impacts on recreational anglers and commercial fishers. However, because the assessment focused
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on fish-related effects to Alaska Native culture, an evaluation of potential impacts to the
recreational and commercial sectors is outside of the scope of this assessment.
William A. Stubblefield, Ph.D.
Potential effects to wildlife and human cultures are briefly addressed in the risk assessment. No
"quantitative" assessment of potential effects is provided. For the most part, it appears that potential
affects to both wildlife and human cultural endpoints are directly proportional to the injury suffered
by salmon populations as a result of any spills or failures. Given the level of detail available at this
point in time regarding mine operations and closure, that is probably about as far as any assessment
could go. I'm not aware of any literature reports or data that would assist in further characterization
of these potential injuries.
EPA RESPONSE: No change suggested or required.
STUBBLEFIELD RESPONSE: No additional comments are provided.
EPA FINAL RESPONSE: No response required.
Dirk van Zyl, Ph.D., P.E.
The EPA Assessment does not identify or appropriately characterize the risks to wildlife and human
cultures due to risks to fish. It only estimates the likelihoods of occurrence and the consequences. See
discussion under Question 4 above regarding suggestions for improving estimation and expression of
the magnitude of risks to wildlife and human cultures due to risks to fish.
EPA RESPONSE: We believe that the likelihood of an occurrence and its consequences constitute
an appropriate and generally accepted definition of risk. We have estimated those to the extent that
existing information allows.
VAN ZYL RESPONSE: No further comments on Question 10.
EPA FINAL RESPONSE: No response required.
Phyllis K. Weber Scannell, Ph.D.
The document focuses on effects to wildlife that would occur from failures - tailings dam failure,
pipeline failure, etc. There are other sources of disturbance to wildlife that should be addressed in a
future mine plan and agency review and permitting. Other mines in Alaska limit truck traffic on the
haul road during caribou migrations, incinerate all kitchen waste, educate workers on bear safety, and
prohibit inappropriate disposals of food containers or other wildlife attractants. Other factors that
might need to be addressed to protect wildlife are limiting air traffic and noise during certain times of
the year. Unless addressed, these issues are more likely to cause detrimental effects to wildlife than
dam or pipeline failures.
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EPA RESPONSE: No change suggested or required. We agree with the reviewer that any future
mine plan would require an evaluation of, and mitigation for, direct effects on wildlife.
WEBER SCANNELL RESPONSE: The reviewer agrees that no change is required.
The reviewer is satisfied with the revised Assessment.
EPA FINAL RESPONSE: No response required.
Paul Whitney, Ph.D.
Problem Formulation for Wildlife. If one addresses the problem formulation for wildlife at face
value, the answer is pretty straight forward. The assessment tells us that the consequences of loss and
degradation of habitat on fish populations could not be quantified because of the lack of quantitative
information concerning salmon, char, and trout populations (page ES-26, third bullet). Furthermore,
we learn that indirect effects, such as risks to wildlife, cannot be quantified (page 5-75, para 1, last
line). Stating that reduced salmon production would reduce the abundance and production of wildlife
(page 5-75, para 1, last sentence) is accurate but not appropriate for a document that is intended to
provide a scientific and technical foundation for future decision making (page ES-1, para 1, last
sentence). It is certainly possible to provide a more complete scientific and technical response to a
question regarding impact to wildlife. I respectfully suggest that the first step in developing a more
complete scientific and technical response is to modify Question 10 by deleting the words "due to
risks to fish" and to separate the risk analysis for wildlife from the risk analysis for human culture. A
revised wildlife question should address both indirect and direct risks. A revised human culture
question should address (among many other risks) both direct and indirect risks to fish and wildlife.
EPA RESPONSE: As the reviewer notes, the scope of the assessment is focused on potential risks
to salmon from large-scale mining and salmon-mediated effects to indigenous culture and wildlife.
We agree with the reviewer that direct effects on wildlife are likely to be important. We would
expect that a full evaluation of any future mining permit applications and subsequent National
Environmental Policy Act Environmental Impact Statements would consider these direct effects.
The revised assessment acknowledges the potential for direct effects on wildlife as well as risks due
to fish.
Mixed Messages. The assessment and questions given to the review committee give mixed messages
regarding the scope of work. A variety of statements and conclusions in the assessment are inter-
related, as one would expect for a document that addresses ecosystem issues. While acknowledging
the overlapping issues and responses, I offer the following discrete points that give me mixed
messages regarding the scope of work and an appropriate characterization of risks to wildlife. Since
these points are related, there is some repetition of information but each of the following items
address a discrete issue.
1. The PREFACE (para 2) clearly states "Our goals in conducting this assessment are to
complete an objective assessment of the potential impacts of large scale mining on aquatic
resources in the Bristol Bay watershed." This statement is subject to wide interpretation by
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this reviewer and by the document itself. For example, aquatic resources include many
species of wildlife and the Cederholm papers indicate that there are 137 species of wildlife
that are associated or closely associated with fish. Wildlife species and their associations are
aquatic resources but have been glossed over in the assessment. The lack of follow-through
in implementing the above goal statement (i.e., not addressing aquatic wildlife and wildlife
associated with fish) is problematic. One can readily understand that timing and budget
constraints result in some statements indicating that data are just not available or that certain
types of modeling, while possible, were not conducted. However, it is difficult to understand
why potential impacts to wildlife are limited to indirect effects due to loss of fish if the
assessment was truly conducted as an assessment of aquatic resources. The message is mixed
because the goal is to assess aquatic resources, but many aquatic resources are not assessed.
EPA RESPONSE: The assessment has been revised and reorganized to better explain the
goals and objectives of the assessment. As stated in previous responses to comments, the
focus of the wildlife assessment is limited to salmon-mediated effects.
2. The assessment was supposedly conducted as an ecological risk assessment (Abstract, line 5).
One of the first steps of an ecological risk assessment is to state well defined endpoints. Suter
(1993, page 22) presents 5 criteria that any endpoint should satisfy. My notes are in brackets.
a. Societal relevance (Assessment appears to do a good job of identifying concerns
of people living near the area of the proposed mine. Yet, many of the potential
endpoints listed in site models (e.g., Figure 3-2E) are not addressed. The reason
for not assessing endpoints in the site models (such as wildlife quality and
quantity) should be provided. Better yet, clearly state both direct and indirect
endpoints for wildlife.)
b. Biological relevance (The biological - especially ecological - relevance is
incomplete. Wildlife and the functions they provide are relevant in that wildlife
comprise many of the secondary and tertiary consumer species in the ecosystem.
The upland and aquatic habitats utilized by wildlife are the indirect and direct
sources of many nutrient and energy inputs to fish in the Bristol Bay ecosystem.
The upland components of the Bristol Bay ecosystem should be assessed in more
detail to provide a biologically relevant assessment. If not, the assessment should
directly indicate why not).
c. Unambiguous operational definition (Overall a good job for a hypothetical mine.
See response to Question 2 for suggestions).
d. Accessibility to prediction and measurement (The inability to estimate the impact
on salmon numbers is problematic. Is the inability due to a lack of population
data, the unwillingness to utilize peer-reviewed methods other than demographic
population modeling, or some other reason? Furthermore, the potential reduction
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in marine-derived nutrients and the potential impact on wildlife can be assessed
and predicted - see below).
e. Susceptibility to the hazardous agent (The assessment does a good job on the
hazards for aquatic resources but not susceptibility to wildlife biotic (e.g., loss of
habitat) and abiotic stressors (e.g., ice dams and scouring, as well as hydrographs
and sedimentation influence on ecological succession). Furthermore, an adequate
ecological risk assessment should address ALL ecological stressors (e.g., loss of
habitat and disturbance) not just toxics).
Suter's five criteria should be addressed when selecting endpoints. All the endpoints selected
and illustrated in figures should be assessed. The incomplete assessment of quantitative
estimates of all the impacts on salmon, non-salmonid fish, wildlife, as well as community and
ecosystem parameters should be remedied.
EPA RESPONSE: The criteria above apply to the specific assessment endpoints
considered in the assessment, as described in Chapter 5. Each of these endpoints meets the
above criteria, and additional information describing endpoints within the ecological risk
assessment process has been added to the beginning of Chapter 5.
3. A complete assessment of aquatic resources as stated in the PREFACE should address both
direct and indirect risks to the many species of wildlife and wildlife habitat that are aquatic
resources and closely associated to aquatic resources. The list of all the aquatic species and
habitat is lengthy. A partial list of categories of wildlife and wildlife habitats that are aquatic
resources includes grebes, ducks, shorebirds, beaver, muskrat, otter, mink, and riparian,
emergent, and aquatic vegetation. The impact of mining on all of the aquatic resources is
given scant coverage in the assessment, with the possible exception of impact to wetlands.
The PREFACE provides wide ranging goals but the assessment has many gaps, and I wonder
why.
EPA RESPONSE: The latest draft of the assessment has been revised and reorganized to
better explain the goals and objectives of the assessment. Those goals and objectives focus
the assessment on salmonid fish and a limited qualitative discussion of the salmon-
mediated effects on wildlife and Alaska Native cultures. We acknowledge and agree with
the reviewer that there will be direct and indirect effects of mining on wildlife, but the
detailed evaluation of those effects will be left to the NEPA and permitting processes
should a mine be proposed
4. The Executive Summary (para 1) indicates ".. USEPA launched this assessment to determine
the significance of Bristol Bay's ecological resources and evaluate the potential impacts of
large-scale mining on these resources." The emphasis on salmonids does not fairly represent
the entirety of ecological resources. To me, ecological resources should include ecological
parameters such as plant community succession, species diversity, energy flow, and structure
and function, in addition to the information on salmonids.
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EPA RESPONSE: The scope of the assessment has been clarified in Chapter 2, and the
specific endpoints considered in the assessment are described in Chapter 5. We recognize
throughout the text that other ecosystem components are important and potentially will be
affected by large-scale mining, but fall outside this assessment's scope. Ecological risk
assessments focus on endpoints that are important to decision makers and stakeholders,
are susceptible to the stressors, and meet other criteria; they do not attempt to cover all
ecosystem components (Suter 1993, EPA 1998).
5. The Scope of the assessment (ES-,1 last para) indicates that "wildlife ... as affected by
changes in the fisheries are additional endpoints of the assessment." This informs the reader
that only wildlife species that are affected by changes in the fisheries will be an endpoint. Yet
many species of wildlife that are affected by changes in the fisheries are not addressed. In
addition, such an endpoint glosses over the importance of assessing fish that are affected by
changes in wildlife. For example, beaver modify aquatic habitat and terns prey on fish. The
scope of the assessment seems to brush over many of the important fish and wildlife
interactions discussed by Cederholm et al. (2000) and Cederholm et al. (2001) and to focus
mainly on marine-derived nutrients. I am pleased with the discussion of the marine-derived
nutrients but am not clear how the emphasis on this one interaction, which is not quantified in
the assessment, furthers the understanding of potential mining impact on the Bristol Bay
ecosystem.
EPA RESPONSE: We agree with the reviewer that there are many complex fish and
wildlife interactions in the study area and the revised assessment acknowledges this fact.
The assessment focused on loss of marine-derived nutrients to the system and on potential
loss offish as a food source for wildlife as important potential salmon-mediated effects on
wildlife. We would expect that a full evaluation of any future mining permit applications
and subsequent National Environmental Policy Act Environmental Impact Statements
would include analysis of other potential causes of effects on wildlife.
6. Gende et al. (2004) use a variety of methods to quantify both the marine-derived nutrients
and energy that transfer from salmon to terrestrial wildlife and habitats. For example, they
determined that bears moved nearly 50% of the salmon-derived nutrients and energy from
streams by capturing salmon and dragging the carcasses from the stream. Gende has also
worked with University of Alaska Associate Professor Mark Wipfli (Gende et al. 2002) on
the relationship of salmon to terrestrial habitats. Alaskan and national experts are likely
available to assist EPA in quantifying the movement of marine-derived nutrients to the
terrestrial ecosystem.
EPA RESPONSE: The references are appreciated We acknowledge that a more
quantitative evaluation of salmon-derived nutrients to the terrestrial ecosystem may be
possible. However, this type of evaluation would require further data collection and
significant analysis, which is beyond the scope of this assessment. A detailed evaluation of
the movement of marine-derived nutrients to the terrestrial ecosystem is not needed to
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assess the impacts of mining on salmonitls, and is more detailed than is needed for a
qualitative discussion of the salmon-mediated effects on wildlife and Alaska Native culture.
We would expect that a full evaluation of any future mining permit applications and
subsequent National Environmental Policy Act Environmental Impact Statements would
address potential effects to salmon-derived nutrients.
7. As mentioned above, the assessment does a fine job of emphasizing the importance of
marine-derived nutrients transported to the terrestrial environment but has relatively little
information on the importance of terrestrial-derived allochthonous nutrients transported to the
aquatic environment. Doucett et al. (2007) discuss methods for measuring terrestrial
subsidies to aquatic food webs using stable isotopes of hydrogen. The potential loss of
terrestrial subsidies due to mining might be as great as a potential reduction of marine-
derived nutrients. It would be informative to discuss the relative importance of marine-
derived, autochthonous, and allochthonous nutrients. Such information might influence "best
mining practices" and reclamation that can partially compensate for lost allochthonous
inputs.
EPA RESPONSE: See response to previous comment.
WHITNEY RESPONSE: The revised EPA text does address this issue but not in a
relative way.
EPA FINAL RESPONSE: Text has been added to Chapter 5 that cites research
demonstrating the relative proportion of marine-derived nutrients (MDN) in freshwater
taxa. Text also has been added to Chapter 7 describing how spatial context influences the
relative roles of MDN, autochthonous, and allochthonous subsidies.
8. Figure 3-2E indicates wildlife quality, quantity or genetic diversity, as well as wildlife
predation are important to Alaska Native Cultures. Tribal elders are said to have concern for
"potential direct effects on other subsistent resources" (which includes wildlife and
vegetation). In addition, Appendix D comments on concerns regarding wildlife (e.g.,
caribou) and vegetation (e.g., berry gathering) that are not directly linked to the fisheries. An
assessment of the direct impact of potential mining and the ongoing exploration on wildlife
and vegetation would address the concerns mentioned above. Once again, I wonder why the
site model figures outline so much detail that is not addressed in the assessment text.
EPA RESPONSE: The conceptual models were drafted to gain an understanding of all
potential sources, stressors, and effects from large-scale mining and have been revised to
clarify the scope of the assessment. EPA focused the assessment on potential risks to
salmonids and subsequent salmon-mediated effects on indigenous culture and wildlife.
There are many other potential risk pathways which are outside the scope of this
assessment, including potential loss ofplant and wildlife subsistence and other cultural
resources (see Figure 2-1).
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The conceptual models have been modified to more accurately reflect issues within the
assessment's scope, and to more clearly identify those pathways considered outside of
scope when they are included.
WHITNEY RESPONSE: The revised models more clearly identify those pathways
considered outside the scope. EPA might want to revise para 2 on page 5-1 that states
"(2) the abundance, productivity, or diversity of the region's wildlife populations" is one
of three endpoints in the revised assessment.
EPA FINAL RESPONSE: The final assessment has been revised to clarify that wildlife
endpoints are only considered in terms of fish-mediated effects.
9. Comments in the main assessment Volume 1 (page 5-76, first lines) indicate that information
on wildlife and potential direct impacts are being collected but are not included. Including
measures of direct wildlife impact in addition to indirect impact as a result of changes in
fisheries would greatly improve the assessment. There are many ways to estimate the impact
of habitat loss on wildlife (Morrison et al. 1998). A better understanding of impacts on
wildlife would presumably provide a better technical basis for designing a reclamation plan.
EPA RESPONSE: The scope of the assessment is focused on potential risks to salmon
from large-scale mining and salmon-mediated effects to indigenous culture and wildlife.
We agree with the reviewer that direct effects on wildlife are important and that there are
ways to estimate effects related to habitat loss. We would expect that a full evaluation of
any future mining permit applications and subsequent National Environmental Policy Act
Environmental Impact Statements would consider these direct effects. The revised
assessment acknowledges the potential for direct effects on wildlife. The assessment does
not include a reclamation plan and is not intended to support the development of a
reclamation plan.
10. The assessment (page 5-77, last sentence) states: "Although this assessment is focused on
salmon, the non-salmon-related impacts on native cultures from routine mine operation are
likely to be more significant..." If this is in fact the case, what better reason could there be
for increasing the scope to include wildlife, vegetation, community, and ecosystem structure
and function (i.e., non-salmon)? Methods and mine-related examples for assessing such an
increased scope are available from the Northwest Habitat Institute (nwhi.org) in Corvallis.
Discussions with Tom O'Neil, Executive Director, indicate that available data from the
Alaska GAP Analysis Project and the Alaska Natural Heritage Program could likely be used
to make such assessments.
EPA RESPONSE: See response to previous comment. This type of evaluation would be
valuable but would require further data collection and significant analysis, which is
beyond the scope of this assessment.
WHITNEY RESPONSE: If the statement in item 10 above is true and the non-salmon-
related impacts are more important to native cultures it seems inconsistent to say that
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Alaska Native organizations only asked for the assessment to address salmon-mediated
impacts on wildlife.
EPA FINAL RESPONSE: Although it is clear that Alaska Native communities and other
organizations have concerns about direct effects on wildlife and local communities, their
petitions to EPA stressed the central importance of salmon; thus, this was the focus of the
current assessment.
11. The risk assessment's focus on "indirect effects on wildlife" (page 5-1, para 2) is consistent
with some of the several goal statements that lean toward fish influence on wildlife. I have
difficulty reconciling this emphasis because further on in the text (page 5-75, para 1, last line)
it is stated that the "indirect effects cannot be quantified." If the indirect effects cannot be
quantified, one should think it is even more important to get a handle on the direct effects,
which can be assessed by any one of several wildlife methodologies (Morrison et al. 1998).
EPA RESPONSE: Wildlife is not a main focus of this assessment. We agree that a more
detailed assessment of direct and indirect impacts of mining to wildlife will have to be done
as part of the NEPA and permitting processes. This assessment is focused on salmon
because of the world class, outstanding salmon fisheries in Bristol Bay. Further, as a
keystone species, salmon serve as an excellent indicator of overall impacts to the
ecosystem
WHITNEY RESPONSE: If you are a hammer, everything looks like a nail. When the
hammer hits the nail all is well. If you are a fisheries biologist everything looks like
harvest/escapement. When harvest and escapement hit goals all is well. If you are a
fishery ecologist, the welfare of the salmon ecosystem looks like biodiversity, structure
and function. If it is possible that biodiversity, structure and function have changed,
you want to know why and what the consequences might be, The above EPA responses
are definitely made by a fishery biologist.
Does the above EPA response assume that all species of salmon are keystone species and
that no wildlife species are keystone? The keystone species concept may be a valid
reason for a fisheries biologist but various wildlife species such as sea otter, wolf, and
beaver have been considered keystone species. While the keystone species concept
allows ecologists to communicate with other ecologists and the public, the keystone
concept is a hypothesis and oversimplifies the complexity of ecosystem biodiversity,
structure and function.
The Clean Water Act, as far as I know, doesn't focus on fish populations but rather
ecosystem function. It is hoped decision makers give due consideration to the
importance wildlife has to ecosystem functions as they relate to salmon.
EPA FINAL RESPONSE: We agree that there are many important wildlife species in the
region that may experience direct effects from large-scale mining and that the ecosystem is
complex, but the focus of the assessment remains on salmon and those species that have
close connections to salmon.
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We agree with the reviewer 'v observations on keystone species. Appendix C discusses the
difference between "key" species included in Appendix C and discussed in the assessment
and "keystone" species. The assessment does not rely on identification of "keystone"
species.
There are sections of the Clean Water Act that focus on ecosystem function and aquatic
life as well as fisheries and wildlife.
12. The assessment indicates the exceptional quality of the fish populations and their importance
to the region's wildlife is due to five key characteristics. The fourth characteristic is "the
increased ecosystem productivity associated with anadromous salmon runs" (page 2-20,
Section 2.3). Similar statements are made by Woolington (2009). How is this increase
measured, and what is the baseline for the increase? I am sure the biologists that wrote about
the increase are trying to convey the concept that the energy and marine-derived nutrients
provided by salmonids is incorporated into the primary and secondary production in the
terrestrial ecosystems in the Bristol Bay watersheds. I am not sure that such a statement
considers the loss of energy and marine-derived nutrients as a result of commercial fishing. Is
it possible that commercial harvest may decrease ecosystem productivity compared to
productivity prior to pre-European (e.g., 200 hundred years ago) harvests? Perhaps it would
be more accurate to delete the word "increase." On the surface, this might seem like a small
edit but this edit is one of many edits needed to address, not only the existing conditions in
the watersheds, but also the existing conditions relative to "pre-European conditions." My
understanding of a Cumulative Impact Analysis is that it includes past assessments of
ecosystem resources and functions as well as current and future conditions (see discussion of
Cumulative Impacts in response to Question 11).
EPA RESPONSE: The purpose of the assessment is to evaluate potential effects of large-
scale mining on the fishery, not the effects of commercial fishing. Therefore, the potential
effects on wildlife associated with loss of marine-derived nutrients considers the present
condition of the watershed and fishery as a baseline for an evaluation ofpotential future
effects of large-scale mining.
13. Pauly et al. (2000) and Libralato et al. (2008) address the energy impacts of fisheries. I would
be interested to know if the impact of fisheries on marine-derived nutrients and energy
available to the wildlife and terrestrial ecosystems in the Bristol Bay watersheds could be
compared to the potential impact of the example mine on marine-derived nutrients and
energy available to the watersheds. Is the potential impact of the mine small in relation to the
impact of commercial fishing or very large compared to commercial fishing? Such
information would be informative for determining acceptability of risks. It is possible that
such a comparison could stimulate discussion of the possibility of compensatory mitigation
for losses due to mining.
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EPA RESPONSE: Compensatory mitigation for losses of aquatic resources from mining is
governed by a regulatory process outside the scope of this project. Nevertheless, in
response to public and peer comments we have included a discussion of compensatory
mitigation in Appendix J of the revised assessment.
WHITNEY RESPONSE: This EPA response is consistent with previous responses but
does not address my question.
EPA FINAL RESPONSE: Text has been added to Chapter 5 and Chapter 7 that provides
further detail regarding marine-derived nutrient (MDN) dynamics and acknowledges that
escapement increases would lead to higher MDN inputs to these systems (although this
may not translate into increased salmon production, particularly where other factors are
limited).
The scope of the cumulative portion of this assessment refers to cumulative risks of
multiple mines in the watershed, not a cumulative evaluation of all potential impacts in the
watershed Thus, evaluation of commercial fishing impacts is outside the scope of this
assessment.
14. The assessment could be greatly improved if more of the linkages and pathways illustrated in
the various Conceptual Models were addressed and if impacts on ecological parameters, such
as community succession (down gradient, in the lake and on tailings and waste rock) and
aquatic and upland structure and function, were addressed. For example, Site Reclamation is
illustrated and highlighted as orange boxes in three places on Figure 3-2C (I'm not sure what
the orange highlighting signifies, for there is no legend on this figure). Information on
possible wildlife limiting factors (e.g., calving and nesting habitat) and plant communities in
the watershed could improve the quality of Site Reclamation. A Reclamation Plan needs to
address the likelihood that reclamation can be implemented and if so what benefits it might
accrue through time. This type of information would likely result in a better risk assessment.
EPA RESPONSE: We agree that more detailed information on wildlife limiting factors
would need to be collected and evaluated as a part of a site reclamation plan. We would
expect that a full evaluation of any future mining permit applications and subsequent
National Environmental Policy Act Environmental Impact Statements would include this
information as a basis for a site reclamation plan.
15. The discussion of wildlife species in Appendix C is very good but little of the insight
provided in these descriptions of hunted or trapped species is reflected in the assessment of
impact of potential mining practices on wildlife. I cannot help but wonder (i.e., mixed
message) why Appendix C is so thick and so little of the good information in Appendix C is
reflected in the assessment document. For example, the impact of noise and human presence
related to mining and roads is addressed on page 54 (Appendix C). Such an impact on certain
sensitive species could be equal to or greater than the loss of wildlife habitat in the mine
footprint. Woolington (2009) indicates that the Red Dog Mine in Alaska has implemented
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certain measures that have reduced the impact of the haul road on wildlife. It would be good
to know what these measures are and if such measures would be equally effective for a road
relatively close to Anchorage.
EPA RESPONSE: The purpose of the appendices vs. the main assessment document has
been clarified in Chapter 1. The former Appendix C has now been published as a separate
US Fish and Wildlife Service document because it serves purposes for the USFWS beyond
the scope of EPA's assessment.
USFWS RESPONSE: We acknowledge the comment about the quality of Appendix C.
Comments related to the scope of the watershed assessment are not specific to Appendix C
and are the responsibility of EPA.
16. Will the proposed haul road to the mine be closed to the public and hunting? If so, the impact
of the road may not be high. I can remember Val Geist saying that wildlife behave the way
one teaches them to behave. Examples are deer in the streets of Banff Park during the
daytime and big horn sheep and elk foraging along the Trans Canada Highway in the Park.
The big horn sheep often stop traffic as people stop to observe them. Outside the Park, where
deer and elk are hunted, one is less likely to see deer and elk along the highway and deer take
on a more nocturnal existence.
EPA RESPONSE: For purposes of the assessment, we assume that the road would be
closed to the public during mining operations but potentially could become a public road
after mining operations cease. About 80% of the transportation corridor is on private land
owned by various Alaska Native Village Corporations, with which the Pebble Limited
Partnership has existing commercial partnerships. Alaska Native Regional Corporations
are charged with managing land and resources within their control in the best interests of
their shareholders. Chapter 13 includes a discussion on the potential impacts of increased
access due to additional roads.
The scope of the assessment is focused on potential risks to salmon from large-scale
mining and salmon-mediated effects to indigenous culture and wildlife. We have not
evaluated direct effects from a transportation corridor on wildlife. We would expect that a
full evaluation of any future mining permit applications and subsequent National
Environmental Policy Act Environmental Impact Statements would consider the direct
effects of the transportation corridor on wildlife.
17. As an arctic and sub arctic small-mammal wonk, I anticipate that any discussion of Alaskan
ecosystems will include some discussion of the less charismatic fauna (small mammals and
songbirds) and the functions they provide. Such discussion is given little attention in the
assessment.
EPA RESPONSE: These issues are outside the scope of the assessment, as specified in
Chapter 2. Appendix C (now an independent US Fish and Wildlife report) selected key
wildlife species for characterization, based on their direct dependence on salmon or on
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their roles in distributing marine derived nutrients through the ecosystem. It was not
possible to fully characterize every species. We recognize that there are multiple species
that were not fully characterized and that have important functions in the terrestrial and
aquatic ecosystem We would expect that a full evaluation of any future mining permit
applications and subsequent National Environmental Policy Act Environmental Impact
Statements would consider all species present in these watersheds.
USFWS RESPONSE: The USFWS selected key species to include in Appendix C and the
selection method is described in the report. We certainly concur that small mammals are
important from an ecosystem perspective, but they are less linked to fish or to public
concerns than the selected species. Songbirds were included in the wildlife report under
landbirds.
3.13 Charge Question 11
Does the assessment appropriately describe the potentialfor cumulative risks from
multiple mines? If not, what suggestions do you have for improving this part of the
assessment?
David A. Atkins, M.S.
According to the Assessment, cumulative risks result from the potential development of at least five
additional prospects: Humble, Big Chunk, Groundhog, Sill, and 38 Zone. Exploiting these prospects
would amount to development of a mining district (see discussion for Question 2 in regards to
appropriateness of the mining scenario).
EPA RESPONSE: No change suggested or required.
The Assessment quantifies the loss of stream lengths and wetland areas that potentially support
salmon and resident fish from the development of these projects under a 'no-failure' scenario. The
assessment is highly speculative given that mine development plans are not available for these
prospects.
EPA RESPONSE: Cumulative impacts assessments evaluate past, present and reasonably
foreseeable future actions that are temporally and spatially linked to the project under
consideration. The potential mines in the revised assessment are reasonably foreseeable based on
State of Alaska planning documents and industry exploration activities. We have expanded the
discussion of cumulative impacts in Chapter 13.
ATKINS RESPONSE: This response is adequate.
EPA FINAL RESPONSE: No response required.
As with the Pebble scenario, it would be helpful to put this loss of resource in perspective in terms of
the fish resources as a whole. It would also be helpful to describe any mitigation measures that are
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feasible to offset the impact of loss of streams and wetlands. Furthermore, it would be helpful to
better understand the role these developments could have in further fragmenting salmon populations.
EPA RESPONSE: Due to lack of comprehensive estimates of limiting factors across the impacted
watersheds, population level effects could not be quantitatively estimated except for the most
severe cases where total losses of runs could be reasonably assumed. Our ability to estimate
population level effects was limited to situations that were assumed to completely eliminate habitat
productivity and capacity in an entire watershed for which estimates of escapement could be
inferred. For this assessment, these conditions are only met in the TSFfailure scenario that
completely eliminates and blocks access to suitable habitat in the North Fork Koktuli River. In
that case, we estimate that the entire Koktuli portion of the run (-29% of Nushagak escapement)
could be lost. Higher proportional losses would occur if significant downstream effects occurred
due to transport of toxic tailings fines beyond the Koktuli as modeled under the full TSFfailure.
Compensatory mitigation is governed by a regulatory process outside the scope of this assessment
but will be an important part of any permitting process. Nevertheless, in response to public and
peer comments we have included a discussion of compensatory mitigation in Appendix J of the
revised assessment.
We have expanded the cumulative effects discussion (Chapter 13) to give a broader description of
streams, wetlands and fish at risk and have incorporated a discussion of the possible effects on
biological complexity and fragmenting salmon populations.
ATKINS RESPONSE: This response is adequate and points out the additional analyses that
would be required during the permitting process.
EPA FINAL RESPONSE: No response required.
The following potential subsidiary impacts from development of a mining district of this scale should
also be described in more detail or at least mentioned:
• The extensive road network required to support mines in the area and the attendant
development associated with this network.
• The camps associated with the project, in migration of workers to the project areas, and
the demand for resources to be imported from outside the area.
• Invasive species that may follow this scale of development.
EPA RESPONSE: The discussion about the cumulative effects of roads (including invasive
species), secondary development, and mining camps has been expanded in Chapter 13.
ATKINS RESPONSE: This response is adequate.
EPA FINAL RESPONSE: No response required.
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Steve Buckley, M.S., CPG
The assessment does describe the potential for cumulative risks from the development of multiple
mines in the area; however, the section is misleading in that it describes specific mine footprints and
tailings disposal sites at these prospects where there is no information on the size or character of the
potential future mine sites. The assessment does not describe the cumulative effects of mine
development.
EPA RESPONSE: We have modified the descriptions ofpotential future mines to make them less
specific (e.g., recognizing that mining infrastructure could go anywhere in the subject claim
blocks). We have expanded the discussion of potential cumulative effects to include the cumulative
effects of multiple mines and development induced by the advent of large scale mining in the
watershed (Chapter 13).
BUCKLEY RESPONSE: These revisions are a major improvement to the document.
EPA FINAL RESPONSE: No response required.
Courtney Carothers, Ph.D.
In general, the report suggests that effects from multiple mines would increase the prevalence and
cumulative impacts of the risks described for the one-mine scenario. Again, for the cultural
assessment, the conclusion is made that effects on humans would be primarily "direct and indirect
loss of food sources" (7-15). As the number of large-scale mines increases in this region, the entire
subsistence way of life could come under threat. This would be a much larger impact than lost food
sources.
EPA RESPONSE: The text of the revised draft assessment (Chapter 12) has been expanded to
clarify that a loss of the subsistence way of life goes well beyond the loss offood resources.
CAROTHERS RESPONSE: Chapter 12 now clarifies that the cumulative effects of multiple
mines on humans would not merely be a loss of food resources, but possibly the loss of
subsistence way of life.
EPA FINAL RESPONSE: No response required.
Dennis D. Dauble, Ph.D.
Individual risk is described in varying levels of detail with overall risk or effects considered to be
largely additive. However, the relative magnitude of the effects of mining each ore deposit is difficult
to discern. It is possible that one of the smaller ore sites could be developed within an acceptable risk
scenario, but it is difficult to determine given that the assessment is largely built on potential impacts
of the Pebble Mine. To put things in perspective (individually and cumulatively), there should be a
discussion of habitat lost given each individual mine footprint, during normal operation (includes
water treatment and withdrawal) and as a result of pollutant exposure. Also, Section 7.4.1 of the main
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report provides estimates of stream miles affected due to blockage and elimination, but provides
nothing quantitative for other direct and indirect impacts of mine operation. The cumulative risk
discussion in Chapter 7 could be expanded to link up with the conceptual model described in Chapter
3.
EPA RESPONSE: We cannot reliably predict the habitat loss due to additional mines. We have
tried to describe plausible examples of where additional mines could be developed on the basis of
active exploration on existing claim blocks. In the revised assessment (Chapter 13) we predicted
aquatic resource impacts based on a typical mine footprint being constructed anywhere in the
block and an average stream and wetlands density. We also expanded discussion of the impacts of
ancillary mine infrastructure and induced development. This provides a conservative estimate of
the cumulative effects of multiple mines and sheds light on whether cumulative effects are a
significant concern. We have developed a specific conceptual model for cumulative impacts and
used it to enhance the discussion.
DAUBLE RESPONSE: The expanded discussion on cumulative impacts and re-organization of
the document largely resolves my questions on this topic. However, it would be informative to
define what "more than minimal" means in Table 13.1, and to include the area or footprint of
each individual site. Note that area of each site are included later in narrative text, but in
different subsections. This information should be included in the Description, not in Potentially
Affected Waters. Finally, I think human development in the Pacific Northwest is a poor
analogy with respect to cascading effects on salmon populations (i.e., last paragraph of 13.5
Summary). Either remove this discussion or make a stronger argument that mining
development in Alaska is equivalent to hydro development + irrigation + deforestation + over-
fishing in the Columbia Basin.
EPA FINAL RESPONSE: There were five claims excluded from Table 13-1. Two had not had any
exploratory activity since 2007. The other three had activity in 2009 or 2010, but spent a total of
$3,000 or less on activity and activity was limited to either assays or surveying access routes. In
contrast, expenditures on the claims included in Table 13-1 were at least an order of magnitude
higher (lowest expenditure = $30,000) and most spent much more (eight claims with expenditures
of $100,000 to $2.3 million).
We had not intended a complete analogy and we have deleted the last two sentences of the final
paragraph to avoid confusion.
Gordon H. Reeves, Ph.D.
I found this chapter well done, even though the analysis was less extensive than what was done for
the Pebble Mine. It is clear that multiple populations would be put at varying degrees of risk
simultaneously if mine development occurs as is portrayed in this report. This certainly could
compromise the "portfolio effect" (Schindler et al. 2010 Nature 46513 June
2010|doi:10.1038/nature09060), which has maintained the long-term productivity of sockeye salmon
in Bristol Bay.
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EPA RESPONSE: We have added the portfolio effect to the discussion of the potential effect of
multiple mines.
Charles W. Slaughter, Ph.D.
Yes - but a qualified "yes." The Assessment appropriately outlines the probability of additional
resource extraction projects beyond Pebble itself, and recognizes that additional resource
opportunities (beyond the claims depicted in Figure 4-6), currently unknown or unverified, could
become viable or desirable to some interests in the future. Section 7.4 summarizes many of the risks.
However, the brief coverage (16 pages) accorded the entire subject of "cumulative risks" is not
consonant with the very long-term, spatially dispersed (and presumably linked by transportation and
communication corridors) impacts and risks of multiple mines (and associated infrastructure) in
many different sectors of the Bristol Bay watershed.
EPA RESPONSE: We have added to the cumulative effects section (now Chapter 13) by
discussing the effects of induced development, including transportation corridors, and the effects
of increased overall access in the watersheds (Box 6-1 discusses cumulative effects in terms of a
single mine). The cumulative effects assessment is not a definitive, quantitative evaluation. It is,
instead, a plausible example of how a mining district could develop and a conservative estimate of
the impacts to aquatic resources and fish. It is intended to shed light on whether cumulative effects
are a significant concern.
SLAUGHTER RESPONSE: Chapter 13 is a welcome and appropriate addition to the
Assessment. The detailed attention paid to other known mining claims or prospects is
appreciated. This chapter properly highlights the potential consequences of those mining
developments, which will become more likely (and economically feasible) if the initial PLP
project at Pebble proceeds as proposed.
(It was interesting to me to note the existence of Pebble South, which apparently directly
abuts Iliamna Lake; I don't recall any reference to that potential development during the
August 2012 meeting in Anchorage, nor any discussion during public testimony of the
likelihood of its proceeding if the initial Pebble project goes forward.)
While "induced development" is briefly considered (Section 13.3), that text is limited to
generalities. The discussion is appropriate, as far as it goes. However, a major long-term
consequence of actually implementing the PLP proposal, under any of the three scenarios, will
be the ancillary and "induced" activities which will inevitably follow. More in-depth
consideration of this broad topic, including second- and third-order effects on salmon and
"fish-mediated" cultural and wildlife values, should be undertaken in a truly comprehensive
assessment of the broader Bristol Bay watershed.
EPA FINAL RESPONSE: We agree that, if mine development moves forward, subsequent
assessments should be comprehensive and address induced development.
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John D. Stednick, Ph.D.
Cumulative risks can result from multiple risks (effects) from a single mine or individual risks from
multiple mines. This chapter identified potential risks from proposed mine activities; without
consideration of design standards or performance criteria, which is difficult without specific mine
designs/plans. Environmental risks were weighted equally - a TSF failure as compared to a blocked
culvert. The simple addition of stream length, as affected by various mine footprints, does not
represent a cumulative risk.
EPA RESPONSE: We have added to the cumulative effects section (now Chapter 13) by briefly
discussing the effects of induced development, including transportation corridors, and the effects
of increased overall access in the watersheds (Box 6-1 discusses cumulative effects in terms of a
single mine). The cumulative effects assessment is not a definitive, quantitative evaluation. It is,
instead, a plausible example of how a mining district could develop and a conservative estimate of
the impacts to aquatic resources and fish. It is intended to shed light on whether cumulative effects
are a significant concern.
Roy A. Stein, Ph.D.
Cumulative Risks from Multiple Mines. Clearly, as amply demonstrated in the Environmental Risk
Assessment, cumulative risks would be greater than those from just the Pebble Mine, even though
these risks are difficult to quantify. Important points made in this section deal with the economies of
scale that would benefit additional mines coming to the Bristol Bay watershed. After the first mine,
new mines become more profitable simply because some of the infrastructure (roads, power, fuel
pipelines, etc.) has already been provided, thus reducing cost outlays for the establishment of new
mines. To me, this seems as quite an insidious process, for once the door is swung open for the first
mine, then many more will follow owing to infrastructure considerations; with these additional mines
come far greater cumulative environmental risks. Quantifying these risks would help the reader and
the public understand what the ramifications of allowing one mine to begin operations might be.
More text attempting to quantify these cumulative impacts would be useful and instructive.
EPA RESPONSE: We have added to the cumulative effects section (now Chapter 13) by briefly
discussing the effects of induced development, including transportation corridors, and the effects
of increased overall access in the watersheds (Box 6-1 discusses cumulative effects in terms of a
single mine). The cumulative effects assessment is not a definitive, quantitative evaluation. It is,
instead, a plausible example of how a mining district could develop and a conservative estimate of
the impacts to aquatic resources and fish. It is intended to shed light on whether cumulative effects
are a significant concern.
William A. Stubblefield, Ph.D.
The potential for cumulative risks associated with the development of multiple mines in the Bristol
Bay watershed is not treated with a great degree of detail. Although each of the potential stressors
(e.g., water withdrawal, habitat illumination, road and stream crossings) are acknowledged and
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addressed, little quantitative consideration is given to the potential effects associated with
development of multiple mines. This, however, is probably appropriate given the hypothetical nature
of the single mine scenario and the potential for greater impacts associated with the development of
multiple lines. Short of concluding that "failures at one mine could be bad and failures at multiple
mines could be worse," little else could be concluded. It is noted that the multiple mines scenario
leads to multiple tailings impoundments, more roads and culverts, increased discharge potential of
contaminated waters and increased habitat loss and reduction of water resources and all of these lead
to potentially greater environmental injury as a result of failures.
EPA RESPONSE: We have added to the cumulative effects section (now Chapter 13) by briefly
discussing the effects of induced development, including transportation corridors, and the effects
of increased overall access in the watersheds (Box 6-1 discusses cumulative effects in terms of a
single mine). The cumulative effects assessment is not a definitive, quantitative evaluation. It is,
instead, a plausible example of how a mining district could develop and a conservative estimate of
the impacts to aquatic resources and fish. It is intended to shed light on whether cumulative effects
are a significant concern.
STUBBLEFIELD RESPONSE: Based on available information and some reasonable
assumptions, it appears that the EPA has addressed the comment satisfactorily.
EPA FINAL RESPONSE: No response required.
Dirk van Zyl, Ph.D., P.E.
The EPA Assessment does not appropriately describe the potential for cumulative risks from multiple
mines. In fact, the assessment does not identify the risks, only the likelihood of occurrence and the
consequences. See discussion under Question 4 above about estimating and expressing the magnitude
of risks and what is required to appropriately describe the potential for cumulative risks from
multiple mines.
EPA RESPONSE: We believe that the likelihood of an occurrence and its consequences constitute
an appropriate and generally accepted definition of risk. We have estimated those to the extent that
existing information allows.
The cumulative assessment is very conceptual at best, as there are no specific proposals from any of
the other potential resource areas. Cumulative impacts can only be evaluated once further details
about other potential mines and their plans are available. At this time, this section can at best be seen
as speculation.
EPA RESPONSE: The cumulative effects discussion is not meant to be a definitive, quantitative
evaluation. We have presented a plausible example of how a mining district could develop and a
simple estimate of the impacts to aquatic resources and fish. It is intended to shed light on whether
cumulative effects are a significant concern.
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It is impossible to improve this part of the assessment with the information on mine development
currently available; it can only be done when further information is published by the various mining
companies.
EPA RESPONSE: Definitive quantitative risk assessments offuture mines will need to wait for
more information on those mines and on the resources they could potentially impact. This
assessment is meant to identify potential issues of concern with development of large scale mining
in the two watersheds. Based on the information available now, is the possibility of cumulative
impacts from multiple mines and induced development a significant concern ? We have utilized the
existing information on the number of mining claims, the extent of recent exploration activities,
local and state land use plans, and the ubiquitous nature of fish habitat in the watersheds to shed
light on that question. Future environmental impact statements will provide more definitive
analyses. We have tried to improve the cumulative analysis by discussing the potential impacts
from entire mine footprints, transportation corridors, induced development and increased access.
VAN ZYL RESPONSE: No further comments on Question 11.
EPA FINAL RESPONSE: No response required.
Phyllis K. Weber Scannell, Ph.D.
There are two issues that should be considered: cumulative effects from a single mine and cumulative
effects from multiple mines. Cumulative effects from a single mine might include aquatic habitat
degradation from non-point sources, including run-off from exposed mineralized rock, seepage from
the tailings impoundment, contaminated dust, noise, and other forms of disturbance.
EPA RESPONSE: We added a discussion on the cumulative effects from a single mine (Box 6-1),
as well as discussion of multiple transportation corridors, induced development and increased
access (Chapter 13).
WEBER SCANNELL RESPONSE: The reviewer is satisfied that these items have been added.
The additional information on cumulative effects contained in the revised Assessment satisfies
the initial concerns of the reviewer.
EPA FINAL RESPONSE: No response required.
Cumulative effects from multiple mines are difficult to predict because there are too many
unknowns. It is frequently to the advantage of a mining company to take advantage of existing
infrastructure, without building new camps, new mills, etc. It is also possible to use an old mine pit
for tailings or waste rock disposal from a new site; however, none of these features can be
determined until there is sufficient exploration to determine if mining is feasible, to characterize the
deposit, and to develop a detailed mine plan. To date, there is not sufficient information to predict
cumulative effects from multiple mines.
EPA RESPONSE: We have expanded the discussion of cumulative impacts from multiple mines
in Chapter 13. The analysis of cumulative effects is largely qualitative rather than predictive. It is
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a plausible example of future cumulative effects that can shed light on whether cumulative effects
is an important topic for consideration as plans for mining in the Nushagak and Kvichak River
watersheds move forward.
WEBER SCANNELL RESPONSE: The reviewer is pleased that this discussion has been
expanded.
A number of changes have been made to the discussion of cumulative impacts from multiple
mines. I note the following changes that are particularly valuable:
The revised assessment has expanded table 7.1 (now Table 13.1), a list of known
prospects in the region. Each of these prospects is described in detail in the following
text.
Tables 13.2 through 13.7 summarize the potential effects to different fish species and
subsistence uses by development of different prospects in the region. These tables
increase the understanding of possible cumulative effects.
The final section of Chapter 7 (Section 7.4.7 of the original draft) has been expanded to
include a more in-depth discussion of the cumulative impacts of multiple mines. This
discussion now includes a more thorough description of possible habitat loss (Section
13.2.7.1) and water quality degradation (13.2.7.3). The section on potential effects on
assessment endpoints (Section 13.4.1) is an especially valuable contribution to the
Cumulative Impacts chapter.
The changes to the Cumulative Impacts discussion address the concerns I raised in my
initial comments.
EPA FINAL RESPONSE: No response required.
Paul Whitney, Ph.D.
Need to Address Past Impacts. EPA's guidance for reviewing cumulative impact analyses (EPA 1999
- most recent guidance on EPA's website) asks that past, present and reasonably foreseeable actions
be considered. The assessment's coverage of cumulative risks from multiple mines certainly
addresses "reasonably foreseeable" mines. Not addressed in the analysis is past impact(s) and how
such impact(s) might be additive to current and foreseeable impacts. As commented above,
commercial fisheries remove a lot of the salmon (up to 70% - over 10 million fish) annually from the
drainages associated with the mine. The continual annual reduction, or loss of energy and nutrients
that might otherwise return to the ecosystems, should be considered a past impact as part of the
cumulative impact analysis.
EPA RESPONSE: The purpose of the assessment is to evaluate potential effects of large-scale
mining on the fishery, not the effects of commercial fishing. Therefore, the assessment considers
the present condition of the watershed and fishery as a baseline for an evaluation ofpotential
future effects of large-scale mining. We have expanded the discussion on past, present and
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reasonably foreseeable actions in Chapter 13. Since the fishery has sustained itselffor over 100
years despite commercial fish harvesting, it is unclear to what degree reduced escapement to the
watersheds has had negative impacts. As Hilborn (2006) states, "Recentpaleoecological analysis
of returns to Bristol Bay show no indication of decreased production since commercial
exploitation began." Furthermore, the fishery is tightly managed by the Alaska Department of
Fish and Game, which reduces the harvest to increase escapement when necessary.
WHITNEY RESPONSE: I'm just citing EPA guidance for Cumulative Impact Analyses. I'm
taken back that it is "unclear" to what degree reduced escapement to the watersheds has had
negative impacts. Page ES-24 of the revised assessment clearly states that "The loss of these
nutrients from a reduction in salmon would likely reduce the production of riparian or upland
species." So it must be clear to EPA that the loss of MDNs due to a mine would likely reduce
ecosystem productivity in the watersheds. If this is clear for mining, I can't understand why it
is not clear to EPA that reduced escapement to the watersheds from past, current and future
commercial fishing has had negative effects.
Several citations (including Hilborn 2005, Pauly et al. (2000, and Libralato et al. (2008) were
provided in my original comments that address the negative impact of fisheries on biodiversity,
energy flow and nutrient cycling in the ecosystem. If these citations are "unclear" and my
previous comments about the impact of reduced MDN are unclear, there is not much else I can
do to explain that reduced escapement will result in less energy and MDN in the watersheds. To
me this is an obvious impact or as stated in Table 9 11 (9-50) a "Logical Implication". Perhaps
the fishery has sustained itself but a sustainable fishery is not evidence that there is no impact
of the fishery on the aquatic, riparian and terrestrial ecosystems of the Bristol Bay watershed.
EPA FINAL RESPONSE: Text has been added to Chapter 5 and Chapter 7 that provides further
detail regarding marine-derived nutrient (MDN) dynamics and acknowledges that escapement
increases would lead to higher MDN inputs to these systems, but also acknowledging that this may
not translate into increased salmon production, particularly where other factors are limited.
However, the assessment is not a cumulative impact analysis that considers the relative effects of
all sources of human intervention in the region. Its purpose is to assess potential effects of one
activity, large-scale mining; thus, the effects of commercial fishing are outside the scope of the
assessment.
I have prepared/managed cumulative impact analyses of fish and wildlife for a relatively small (e.g.,
a 200-acre aggregate mine) and a relatively large 7,100-acre coal mine in Washington. A cumulative
impact analysis of past, present, and future fish and wildlife losses for the coal mine expansion in a
large watershed indicated cumulative impacts of the expansion were less than one percent of past
mining, agriculture, urban and forest activities in the watershed. In addition, the cumulative loss
could be fully mitigated by compensatory restoration. I would be interested to know what the
estimated fish and wildlife loss is due to the example copper mine in comparison to the loss related to
the commercial fishery. In addition, I would be interested to know if potential fish and wildlife losses
due to mining could be fully mitigated. If the watershed is pristine or nearly pristine, the opportunity
for compensatory mitigation may be low. If the past impact of the commercial fishery is large and the
watersheds are not pristine, there may be opportunities. There is not much degraded habitat that
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could be improved by a mitigation plan. If such a cumulative impact analysis were conducted, it may
stimulate conversation about reducing commercial fishing to compensate for impact losses due to
mining.
EPA RESPONSE: Mitigation to compensate for effects on aquatic resources that cannot be
avoided or minimized by mine design and operation would be addressed through a regulatory
process that is beyond the scope of this assessment. Nevertheless, in response to public and peer
comments we have included a discussion of compensatory mitigation in Appendix J of the revised
assessment. Appendix J includes a discussion of the challenges of creating equivalent habitat for
anadromous and resident fish and why this would be particularly challenging in the context of the
Bristol Bay watershed Compensatory mitigation requirements address the need for project
proponents to replace aquatic resources and ecosystem functions that their project has impacted.
Reduced fishing harvests would not replace lost spawning and rearing habitat. Further, it would
remove the burden of compensation from the party that caused the damage.
WHITNEY RESPONSE: My intent for mentioning a reduction in commercial harvest to
compensate for potential impact(s) due to a large mine is more rhetorical than substantive. My
intent was to "stimulate conversation about reducing commercial fishing" or "wondering if it
was technically feasible" not to recommend it. The above EPA response is a good start at a
discussion. Potential impacts of the proposed mine could definitely reduce harvest and
escapement and what is the recourse? Some options for "out of kind" and "off site"
compensations are discussed in the recently added mitigation discussion and this is good.
EPA FINAL RESPONSE: See response to above comment.
3.14 Charge Question 12
Are there reasonable mitigation measures that would reduce or minimize the mining risks
and impacts beyond those already described in the assessment? What are those measures
and how should they be integrated into the assessment? Realizing that there are practical
issues associated with implementation, what is the likelihood of success of those
measures?
David A. Atkins, M.S.
The Assessment describes what is considered to be conventional 'good' mining practice, but does not
adequately describe and assess mitigation measures that could be required by the permitting and
regulatory process. A thorough analysis of possible mitigation measures as employed for other
mining projects and the likelihood that they could be successful in this environment would be
necessary.
EPA RESPONSE: With regard to the terminology of "best", "good", or other terms for the
practices used, what was intended to be conveyed in the assessment is that we assumed modern
mining technology and operations. The terms are qualitative when generally interpreted, or have a
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regulatory meaning. The term "best management practices" is a term generally applied to specific
measures for managing non-point source runofffrom stormwater (40 CFR Part 130.2(m)).
Measures for minimizing and controlling sources ofpollution in other situations are referred to as
best practices, state of the practice, good practice, conventional, or simply mitigation measures. We
have added a text box in the revision Chapter 4 to discuss terms. Mitigation measures considered
feasible, appropriate, and 'permittable' (as per Gliaffari et al. 2011), were considered in the
assessment, and these are measures common to other copper porphyry mines. Evaluation of
alternative strategies (e.g., other options presented in Appendix I for the mitigation of the same
issue) should be part of the permitting process for a specific mining plan. The State of Alaska does
have statutory and/or regulatory requirements for an approved Plan of Operations (11AAC
86.800), a Reclamation Plan (Alaska Statute (AS) 27.19.30) and appropriate Financial Assurance
(AS 27.19.040) and the revised Chapter 4 notes these requirements.
ATKINS RESPONSE: This response is adequate.
EPA FINAL RESPONSE: No response required.
It is highly likely that for mines located in the Bristol Bay watershed, conventional engineering
practices would not be sufficient. Therefore, it is important to consider mitigation on numerous fronts
when determining the viability of the project. A section on innovative and state-of-the-art approaches
for both mitigation and construction of mine facilities would be helpful to better understand if risks
can be minimized or eliminated given sufficient funds.
EPA RESPONSE: We agree generally that conventional engineering practices may not be
sufficient, but it may not be appropriate to test innovative approaches in a watershed such as the
Bristol Bay watershed We are not aware of innovative mitigation measures that have sufficient
history to be applicable to this location.
ATKINS RESPONSE: This area requires more research and would benefit from a survey of
current industry practice.
EPA FINAL RESPONSE: The scenarios, including mitigation measures, are based on current
industry practices as found in Northern Dynasty Mineral's preliminary plan (Gliaffari et al. 2011).
We agree that, if a mine were built in the Bristol Bay watershed, the mining companies involved
should research the full range ofpotentially applicable practices. However, the assessment cannot
assume a level ofpractice beyond that suggested by the potential permittee.
Under the no-failure scenario, the footprint of the mine (open pit, block-cave subsidence zone, waste
rock and tailings areas) will by necessity destroy habitat. There may be ways to create equivalent
habitat to compensate for lost habitat in areas within the watershed that are currently not productive
for fish. This form of mitigation may work for resident fish, but it is unclear if it would work for
anadromous fish that return to very specific locations to spawn.
EPA RESPONSE: Mitigation to compensate for effects on aquatic resources that cannot be
avoided or minimized by mine design and operation would be addressed through a regulatory
process that is beyond the scope of this assessment. Nevertheless, in response to public and peer
comments we have included a discussion of compensatory mitigation in Appendix J of the revised
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assessment. Appendix J includes a discussion of the challenges of creating equivalent habitat for
anadromous and resident fish and why this would be particularly challenging in the context of the
Bristol Bay watershed
ATKINS RESPONSE: This response is adequate.
EPA FINAL RESPONSE: No response required.
It is also becoming common practice to offset impacts from project development with preservation of
equivalent habitat areas that are also at risk from development (http://bbop.forest-trends.org/). It is
unclear if this is a feasible consideration for this project as this could involve allowing one
development (e.g., Pebble), while potentially taking away the development rights of others
(presumably for proper compensation).
EPA RESPONSE: See response to previous comment. The potential efficacy of using habitat
preservation as a form of compensatory mitigation for impacts in the Bristol Bay watershed is
discussed in Appendix J.
ATKINS RESPONSE: This response is adequate.
EPA FINAL RESPONSE: No response required.
Steve Buckley, M.S., CPG
There are many reasonable mitigation measures that could reduce the risks and impacts beyond those
described in the assessment. Some of these are contained in the Appendices and referenced therein
but not discussed in detail or described in the assessment. It is beyond the time constraints provided
in this review to develop an exhaustive research list of these potential mitigation measures; however,
EPA could include measures designed to: reduce the mine footprint and limit the number of
potentially affected watersheds; reduce, isolate, or eliminate the amount of potentially acid
generating waste; provide secondary containment measures for all pipeline corridors; and use natural
streambed arch culverts and bridges at fish bearing stream crossings.
EPA RESPONSE: The mitigation measures proposed within the mine scenarios are a subset of
options presented in Appendix I, all of which were presented as appropriate for the Pebble deposit
in Ghaffari et al. (2011). Appendix I includes multiple options for each source of contamination,
with some having specific applicability (e.g., site and material characteristics) and others being
more broadly applicable. Some additional mitigation measures have been added to the scenarios in
Chapter 6 of the revised assessment (e.g., processing PAG waste rock over the life of the mine and
selective flotation to minimize pyrite in tailings). Mitigation to compensate for effects on aquatic
resources that cannot be avoided or minimized by mine design and operation (e.g., by reducing the
footprint or limiting the number of affected wetlands) would be addressed through a regulatory
process that is beyond the scope of this assessment. Nevertheless, in response to public and peer
comments we have included a discussion of compensatory mitigation in Appendix J of the revised
assessment.
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BUCKLEY RESPONSE: This seems to be a reasonable approach.
EPA FINAL RESPONSE: No response required.
Courtney Carothers, Ph.D.
While I do not have knowledge of mitigation measures, a more thorough discussion of mitigation
measures could be included. Even if mitigation measures are largely deemed to be ineffective in this
case, they should be presented and evaluated as such.
EPA RESPONSE: EPA agrees with this comment and Appendix I is intended to provide that
discussion. The mitigation measures proposed within the mine scenarios are those that could
reasonably be expected to be proposed for a real mine (they are a subset of options presented in
Appendix I), all of which were presented as appropriate for the Pebble deposit in Ghaffari et al.
(2011). Evaluation of alternative strategies (e.g., other options presented in Appendix I for the
mitigation of the same issue) should be done during a permitting process for a specific mining
plan. The assessment assumes that measures chosen for the scenarios would be as effective as
possible.
CAROTHERS RESPONSE: EPA response is sufficient.
EPA FINAL RESPONSE: No response required
Dennis D. Dauble, Ph.D.
Potential mitigation measures are well described in Appendix I. I have no suggestions for additional
measures. Implementation of mitigation measures is entirely dependent on the regulatory framework
for operations and the oversight and monitoring practices that would be mandated as a condition of
the mining activity. Thus, some discussion of how/which mitigation practices would be most
applicable in the Bristol Bay watershed (and limitations thereof), given constraints and characteristics
of local hydrology and geology, is warranted.
EPA RESPONSE: The mitigation measures proposed within the mine scenarios are those that
could reasonably be expected to be proposed for a real mine, are a subset of options presented in
Appendix I, and were presented as appropriate for the Pebble deposit in Ghaffari et al. (2011).
Evaluation of alternative strategies (e.g., other options presented in Appendix I for the mitigation
of the same issue) should be done during a permitting process for a specific mining plan. Permit
applicant mitigation measures that reduce the risks identified in the assessment would be welcome
during the application process.
DAUBLE RESPONSE: The addition of Ghaffari et al. (2011) helps substantiate the discussion
of potential mitigation measures. Further, this topic is well-covered in both Appendices I and J,
as well as Chapter 7 of the main document.
EPA FINAL RESPONSE: No response required.
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Gordon H. Reeves, Ph.D.
I identified one potential mitigation for culverts - the use of open arch types that are at least one
bankfull width in size. As described in my response to Question 7, this could reduce many of the
potential impacts raised by the authors.
EPA RESPONSE: Suggestion noted. In our scenarios (Chapter 6), we assumed state-of-the-art
practices for design, construction, and operation of the road infrastructure, including design of
bridges and culverts for fish passage.
Charles W. Slaughter, Ph.D.
If it is assumed that the PLP project, or some similar development, were to go forward, I cannot
suggest mitigation measures beyond those discussed above. Since a major concern for salmonids -
perhaps THE major concern - is with consequences of the transportation corridor, simply having the
mine without the roads/pipelines would alleviate much potential risk. However, there is presumably
no practical, economically feasible way to not have the transportation corridor; air transport of all
materials to and from the site might technically be possible, but would not be economically feasible.
EPA RESPONSE: We agree that it would be infeasible to have a mine in this location without also
having road access. No change suggested or required.
SLAUGHTER RESPONSE: OK. One other off-the-wall thought, having recently again used
the Seattle monorail - might it be worth a brief look at life-of-project costs of establishing an
elevated monorail in lieu of the road system - thus avoiding many of the
stream/culvert/wetland issues (except during construction), possibly providing lower total $/
ton-mile freight costs Cook Inlet to Pebble, considering the many truck trips (>50/day)
projected annually, providing tighter control of access, and concurrently providing a platform
for the four pipelines? Just a "Popular Mechanics-style" thought...
EPA FINAL RESPONSE: Though these concepts may be worth consideration for the mining
companies, we cannot go that far beyond the state-of-practice in our scenarios.
John D. Stednick, Ph.D.
The purpose of this assessment is not to identify mitigation measures. This suggests that things can
be fixed by mitigation. Risks were identified for a variety of situations, and the preventative
measures would better address the mining impacts. Mitigation measures are also a mining cost that
needs to be determined by the mining company and compliance with state and Federal regulatory
authorities.
EPA RESPONSE: Comment noted. We agree that mitigation measures required for an actual
mine would be determined through the regulatory process. No change suggested or required.
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Roy A. Stein, Ph.D.
Mitigation: Complete Tailings Storage Facility (TSF) Failure. In some ways, some of the failures
reviewed herein are not really subject to mitigation. For example, if a Tailings Storage Facility (TSF)
completely fails, options for mitigation become limited very quickly. With a complete failure, it is
"game over", with toxic sediments flowing into the Nushagak River all the way to Bristol Bay,
thereby destroying the entirety of salmonid spawning habitat in this river by redirecting the channel
and inundating the gravel/cobble steam bed with sediment (meters in depth). Mitigation under these
circumstances is impossible, in my view. Given this scenario, I was surprised that the impacts were
only assessed 30 km downstream of the TSF failure; is this realistic? I think not, given what we
know of other mines.
EPA RESPONSE: We acknowledge the limitations of the hydrologic modeling. We now
emphasize more clearly the potential for the effects of TSFfailure to extend to Bristol Bay. The
potential for remediation (and associated risks) are discussed in Section 9.7.
The amount of text dedicated to a TSF failure is large (36 pages) as compared to other failures. I
suggest this section be shortened to bring it more in line with other sections. Briefly summarizing
impacts would focus the text and help the reader appreciate what it would mean to have a TSF failure
without having to wade through so much text.
EPA RESPONSE: We have revised this section of the assessment. However, given its importance
to stakeholders, local communities, and decision makers, it was not significantly shortened Other
accidents and failures are now addressed in more detail.
Dry Stacking Mine Tailings: Appendix I, page 9. Given the horrific impact of a TSF dam failure,
should mine operators consider a relatively new technique incorporating "paste tailings technology"?
Here, tailings are thickened by water removal (down to 20% water) and filtering; tailings are then dry
stacked onto a lined disposal site. These stacks "have a lower potential for structural failure and
environmental impacts" (Martin et al. 2002). I would encourage the authors to argue for this
substitute for the more traditional TSF for this solves at least two problems: 1) eliminates the
possibility of a TSF failure (a huge gain!) and 2) reduces the amount of monitoring and maintenance
of the waste tailings "In Perpetuity" (another major gain). Finally, what does "Best Management
Practices" have to say about these two approaches to the storage of tailings waste?
EPA RESPONSE: We agree that dry stack storage and paste storage are options for mine
proponents to consider. Although the option of using paste tailings is one that might be explored,
the type of tailings disposal that operators propose is generally based on two things: the type of
mine and the quantity of tailings. A balance would need to be considered between the low
risk/high impact of a tailings dam failure and the certainty of increased area of disposal and the
increased cost of tailings handling for paste tailings. A "rule of thumb" for design of dry stack
tailings is to allot 25 acres for every thousand dry tons of tailings per day over the life of a 20 year
operation (SME Mining Engineering Handbook 1973). This would amount to 4,900 acres (25
*200000 *.99/1000). Since paste tailings are more voluminous than dry and the scenario contains
a 25 year mine life rather than 20 years, the area of a paste tailings facility would exceed the
calculated amount resulting in over a 1/3 increase in the area occupied by tailings than
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contemplated in the current mine scenario. With a paste tailings facility, the monitoring and
maintenance of a large dam is removed but that is replaced by the monitoring and perhaps
treatment of the leachate draining through the tailings pile (that contains 20% water) as well as
the long-term maintenance of the cap that is placed over the tailings at the end of the mine life.
The choice of a tailings disposal methodology may be affected by the need to avoid or minimize
effects to wetlands or the technical feasibility of constructing the structural components of the
project.
Mitigation: Partial TSF Failure. If a TSF partially fails or is discovered beginning to fail, then I
believe mine operators have a chance to save the dam and thereby protect the river, but only if: 1) the
appropriate Standard Operating Procedures (SOP) for an emergency response are in place, 2) the
necessary equipment (my presumption here is that heavy, earth-moving equipment would be
required), materials, and supplies are onsite near the facility, and 3) trained personnel (meaning that
they have practiced these repair SOPs in the preparation for such an event) are available for
immediate action. One might argue that these procedures are more proactive than mitigating and I
would agree, reflecting the near impossibility of invoking any mitigation measures associated with
TSF failure.
EPA RESPONSE: Our scenarios presuppose that there are mitigation measures in place, but
examines the effects of a failure of those measures. EPA agrees that SOPs are part of a mining
operation and plan; however, inclusion of SOPs and details for emergency responses to a failing
dam were outside the scope of this assessment. No change suggested or required
Dredging: Post TSF Failure. In the text (pages 6-1 to 6-2), a reference is made to dredging
materials out of the river post spill. I can't imagine this would mitigate any losses of spawning
substrate for salmon. Indeed, because only 5% fines in gravel substrates compromise salmon
reproductive success (and perhaps even selection of these areas for spawning in the first place),
removal of meters of sediment with a dredge doesn't seem to be a solution. Whereas dredging might,
in a best-case scenario, reduce the time to recovery of the substrate, I don't believe it will hasten
recovery significantly. Dredging also serves to bring toxic sediments up into the water column
perhaps compromising all organisms in the system. By not dredging, we allow the natural system to
recover, which, in my view, would be preferable to any sort of "dredging mitigation". Some
reflection by the authors on this issue would be valuable.
EPA RESPONSE: Agreed Adverse effects of dredging are discussed in Section 9.7.
Mitigation: Pipeline Failure. With automatic shut-off valves stationed along all four pipelines, we
would expect to know precisely just how much effluent will be spilled during any single event. With
this information in hand, mine operators can easily anticipate spill size, toxicant characteristics and
thereby judge what equipment, materials, and supplies would be necessary for mitigating any spill.
As with the TSF failure, mine operators should have in place: 1) the appropriate Standard Operating
Procedures (SOP) for an emergency response, 2) the necessary equipment, materials, and supplies
onsite near the pipeline (given the length of the road, these items should be cached at several
locations along the road, such that response time is minimized), and 3) trained personnel (meaning
that they have practiced these mitigation SOPs in the preparation for such an event) are available for
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immediate action. Shouldn't pipes be double-walled? Again, what would "Best Mining Practices"
say in this context?
EPA RESPONSE: The original draft assessment included pipeline failure scenarios that
quantified the magnitude of spill events. The draft included the most commonly used and accepted
practice of using double walled pipes where above ground and water. There is, to the best of our
knowledge, no standard SOP for a product concentrate slurry spill As is discussed in the
assessment, terrestrial spills would be excavated Spills to streams might also be excavated,
although the physical damage to habitat would be considerable and the efficacy of excavation
would depend on how far stream flow had spread the material An assessment of diesel spills has
been added to the revised draft assessment in Chapter 11, and it refers to a NOAA and API report
for standard remedial practices.
Mitigation: Failure of Water and Leachate Collection. This failure differs from TSF and pipeline
failure, where failures are more akin to catastrophic, for here failure is somewhat more gradual in
coming (my guess is). Proactive vigilance is the watch phrase here where continual, careful
monitoring will indicate when failure begins. Because the "spill potential" is relatively small
(certainly compared to a TSF failure), less urgency is required on the part of mine operators.
However, as pointed out previously, just because the potential is small, over time the impacts could
be great. Hence, the mitigation undertaken with water and leachate collections would require (one
would hope) just the tweaking of the collection system in place to eliminate leakage through time.
Again, personnel trained in how to respond to these gradual increases in water and leachate leaks are
required to stay ahead of this issue, thus preventing any toxic materials from flowing downstream
into the Nushagak and Kvichak rivers.
EPA RESPONSE: The revised draft assessment acknowledges that the leachate capture system is
not likely to capture all leachate during routine operations and shows that water quality standards
would be exceeded in a considerable stream length as a result. Mitigation measures that ensure or
maximize the detection of leachate in groundwater before it reaches surface waters would be vital.
William A. Stubblefield, Ph.D.
I'm sure there are number of technological/engineering measures that could be implemented to
reduce the potential for environmental injury associated with development of mining in the Bristol
Bay watershed. The development of this a priori risk assessment provides useful information in
identifying were potential risks may exist and should provide mine development professionals with
the degree of guidance about the types of risks and potential consequences of mine activity failures.
Perhaps by recognizing the magnitude of adverse consequences associated with potential failures,
steps can be taken to implement safety measures early in the planning process that would render
mine development more acceptable. In addition, using the assessment to define areas of uncertainty
my provide direction for future research that would be beneficial for the project. Again, because of
the lack of detail associated with the hypothetical mine scenario, it is impossible to estimate the
likelihood of success of any mine control activities.
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EPA RESPONSE: One purpose of this assessment is to inform future decisions concerning mine
design and required mitigation. The purposes of the assessment are clarified in the revised
introduction (Chapter 1).
STUBBLEFIELD RESPONSE: I agree with the US EPA comment, Section 1.2 of the document
does an adequate job of clarifying several of the potential uses for this document. The question
originally posed asks "if there are mitigation measures that would reduce or minimize mining
risks and impacts beyond those described in the assessment." In my reading of Section 1.2 I
find no mention of this assessment providing information to industry engineers/environmental
scientists/decision-makers that would help inform them about potential risks (or
regulatory/stakeholder concerns) that may be mitigated by design/practice considerations. This
would appear to be an important use of this assessment. If industry is aware of potential risks
and/or concerns early in the development of a project it may be possible to take steps to
incorporate actions to mitigate identified environmental risks/concerns. My expertise is not
appropriate for evaluating possible mining mitigation measures but I'm sure others on the
review panel had that particular expertise.
EPA FINAL RESPONSE: The assessment, like other risk assessments, evaluates risks associated
with a potential action. The results can indicate what components of the potential action are
associated with the greatest risk and that information informs subsequent decisions concerning
the adoption of additional mitigation. However, it is not the role of this assessment to find and
recommend additional mitigation actions or technologies.
Dirk van Zyl, Ph.D., P.E.
Yes, there are reasonable mitigation measures that would reduce or minimize the mining risks and
impacts beyond those already described and incorporated by the EPA in the assessment. There are a
host of measures that are not addressed in the assessment and lists of these are identified below under
the headings of regulatory and engineering. This list is by no means exhaustive.
EPA RESPONSE: See response under the commenter's headings of "Regulatory" and
"Engineering" below.
While the EPA Assessment presents a series of potential mitigation measures in the main report, the
majority were rejected. Appendix J [sic] to the report also includes a generic discussion of mitigation
measures. The Main Report does not address the application or implications of these in any project
specific details, e.g. compensatory mitigation for wetlands, streams and other aquatic resources.
EPA RESPONSE: We did not reject the majority of potential mitigation options mentioned in the
report. The mitigation measures proposed within the mine scenarios are those that could
reasonably be expected to be proposed for a real mine. They are a subset of options presented in
Appendix I, were presented as appropriate for the Pebble deposit in Ghaffari et al. (2011), and are
common with mining of porphyry copper deposits. Mine design for the scenarios is closely based
on that presented in Ghaffari et al. (2011) and incorporates the mitigation measures included in
that mine design. Mitigation to compensate for effects on aquatic resources that cannot be avoided
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or minimized by mine design and operation would be addressed through a regulatory process that
is beyond the scope of this assessment. Nevertheless, in response to public and peer comments we
have included a discussion of compensatory mitigation in Appendix J of the revised assessment.
Multi-stakeholder engagement processes, such as Failure Mode and Effects Analysis, can be used to
further expand on these mitigation measures. It is recommended that EPA recognize these and
potentially other measures that may be proposed in the public comments and make a serious effort in
including the potential effects of these on failure likelihoods, consequences and risk magnitudes. It is
an important aspect of improving on the range of potential outcomes.
EPA RESPONSE: We recognize that other mitigation measures and mine designs have the
potential to address impacts and risks identified in the assessment. Evaluating the risks of all
potential mitigation measures and mine designs is not a goal of this assessment, which identifies
potential risks of concern from plausible mine scenarios based on current practices and a recent
plan (Ghaffari et al. 2011). A permit applicant's mitigation measures that further reduce the risks
identified in the assessment are appropriate for the application process.
Regulatory. The EPA Assessment neglects the typical outcomes resulting from the permitting and
regulatory processes for new mines, where permit stipulations may require specific actions resulting
from discussions, public comments and regulatory frameworks. The following is a partial list of
these:
• Section 404 of the CWA (See discussion under Question 3 above).
• Permitting stipulations and requirements for monitoring. Using permit stipulations for
monitoring can reduce a large number of the consequences identified in the report. For
example, the consequences associated with blocked culverts, etc. can be significantly
reduced by permit monitoring requirements and subsequent enforcement.
• Financial assurance will be required for mine closure. Financial assurance can be a very
beneficial tool during operations, premature closures, mine closure, as well as post-
closure monitoring and maintenance. Experience gained during operations can help
develop the closure and post-closure financial assurance requirements.
EPA RESPONSE: The assessment is intended to identify impacts and risks of concern which may
inform future NEPA and permitting processes. The revised assessment presents basic discussion
offinancial assurance and listings of requirements for permitting a mine in Chapter 4. The
assessment is not a mining plan and is not meant to replace the regulatory process for
development of mining plans for these prospects, but can inform that process about important
risks that should be addressed.
VAN ZYL RESPONSE: Box 4-3 on Financial Assurance is a good addition to the report. The
author would like to suggest a reworking of part of the introductory paragraph, namely:
"Thus, regulations also serve to hold an operator accountable for potential future impacts,
through establishment offinancial assurance requirements and imposition offines for non-
compliance with permit requirements." This sentence can be read to indicate that financial
assurance can be used to non-compliance with permit requirements. The author suggests that
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the sentence be modified to clarify the concepts, e.g. to (suggested inserts [underlined]): "77i«s,
regulations also serve to hold an operator accountable for potential future impacts, through
establishment of financial assurance requirements for closure and reclamation of the mine and
imposition offines for non-compliance with permit requirements during mine operations."
EPA FINAL RESPONSE: This clarification has been made in the final assessment.
Engineering. A number of engineering options are mentioned in the report but discounted in many
cases. Many of these engineering mitigations are currently used in the industry. The following may
repeat a number of those mentioned in the report:
• Redundancy, e.g. additional embankments may be considered downstream of the TSF to
contain tailings and supernatant that may be transported as a result of TMF failure. While
this may result in a larger local surface impact, it will protect downstream waters in the
case of a failure resulting in tailings discharge.
• Further processing of tailings to remove the remaining sulfides.
• Tailings management options other than slurry deposition, such as production and
management of filter cake.
• Waste rock management options to reduce releases during operations, e.g. addition of
lime to the PAG rock.
• High standards implemented for road design, construction, monitoring and maintenance.
• Double containment of all pipes containing concentrate and other materials. This is
already required under the International Cyanide Code for all pipelines containing
cyanide solutions.
EPA RESPONSE: The revised assessment presents background information on mining, including
a sub-set of mitigation measures from Appendix I, in Chapter 4 and the scenario-specific
information in Chapter 6. The option of selective flotation to reduce the amount of sulfide in the
bulk tailings, as well as processing of PAG waste rock over the course of operations, have been
included in Chapter 6. In the draft assessment, selective flotation was discussed in the background
information, but was missed in the scenarios. A double-walled pipeline along the entire length of a
pipeline might be desired from a purely environmental protection standpoint; however, it may not
be feasible or cost effective to do this given the length of the pipeline. Therefore, the assessment
proposed the most commonly used (and accepted method) of double-walled construction over any
water bodies. While EPA opted not to include redundancy in tailings embankments in the
scenarios, this option, as well as full pipeline double-wall construction, could be evaluated for
appropriateness during the regulatory process for any future permit application.
VAN ZYL RESPONSE: The comment that a double-walled pipeline along the entire length of
the pipeline not be feasible or cost effective to do this given the length of the pipeline" is
puzzling. This seems like a design comment not a risk assessment comment. Clearly if that is
the best option to reduce risks then it becomes part of the cost of doing business, unless other
option having similar low risks can be proposed. Please reconsider.
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EPA FINAL RESPONSE: The pipeline design was chosen to add a reasonable additional degree
of mitigation to Northern Dynasty Minerals' preliminary plan (Ghaffari et al. 2011) by double
walling the pipe at stream crossings. The quoted statement was provided as a supplementary
comment to explain that, in our judgment, adding double walling to the entire pipeline was more
than we could reasonably expect the mining companies to propose.
The likelihood of success of these proposed and other potential mitigation measures can be evaluated
by considering their impacts on the overall project. A range of alternative project technical
alternatives and facility-siting locations will have to be developed instead of using only the
hypothetical scenario.
EPA RESPONSE: The purpose of the assessment is to describe the potential adverse
environmental effects that could exist even with appropriate and effective site mitigation measures.
Considering alternative options is part of a permit application process and outside the scope of this
assessment. No change required.
Phyllis K. Weber Scannell, Ph.D.
There are many avoidance or mitigation measures that would be implemented to reduce or minimize
mining risks. I have described some possible approaches when answering the previous questions. To
summarize:
The two most important questions for reducing or minimizing mining risks are:
• Can a mine in this area be designed for closure?
• Is it acceptable to develop and operate a mine that will require essentially perpetual
treatment?
EPA RESPONSE: We agree that these are key questions that must be addressed in the regulatory
process. Our purpose in the assessment is to evaluate the risks resulting from a mine operated with
modern conventional mitigation measures for design, operation, monitoring and maintenance,
and closure. The regulatory process addresses significant and unacceptable risks. Chapter 4 of the
revised assessment discusses regulatory and financial assurance requirements for mining in
Alaska.
WEBER SCANNELL RESPONSE: This comment by the reviewer was intended to highlight
the importance of a rigorous regulatory process and the potential for long term risks to the
environment; she understands and agrees with the intent of EPA's risk evaluation.
The reviewer is pleased that Chapter 4 now includes a discussion of regulatory and financial
assurance requirements.
EPA FINAL RESPONSE: No response required.
Specific Measures that can be taken to minimize risk include:
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Limiting metals contamination and acid drainage:
• Design the mine pit to limit oxidation on pit walls. Where feasible, conduct concurrent
reclamation.
• Develop plans for classification and storage of waste rock, lower grade ore, overburden,
and high grade ore.
• Develop and maintain tailings storage facilities with fail-safe provisions. An emergency
discharge of untreated waters from a tailings storage facility could be made to a
collection pond for later treatment or the tailings pond could be engineered to
accommodate a higher flood event so the likelihood of overtopping is minimized.
Consider alternate methods for tailings disposal (dry stack following sulfide removal,
etc.).
• Implement concurrent reclamation of disturbed areas, including stripped areas and mine
pits.
• Collect and treat point and non-point source water.
• Design and implement plans for the quantity and timing of discharges of treated water;
especially if the treated water is high in total dissolved solids. Monitor ground water,
seepage water, and surface water.
• Design system for collection and bypass of clean water and collection and diversion of
contaminated water to a water treatment system.
• Require stations for truck wheel washing.
EPA RESPONSE: Many of the measures presented here were included in the scenarios and in
Appendix I and are mitigation measures commonly included for mining of this type. Other bullets
noted here are good suggestions for things to address during the regulatory process, should a
permit application be submitted.
WEBER SCANNELL RESPONSE: The reviewer agrees that many of the issues listed above
should be addressed during the regulatory process. The comment was initially made to
highlight the importance of a rigorous regulatory review.
The reviewer is satisfied and finds that the concerns have been addressed by additional
information in the revised Assessment.
EPA FINAL RESPONSE: No response required.
Protection of Fish Habitat:
• Review all in-stream activities in waters important to the spawning, rearing, or migration
of anadromous and resident fish.
• Design and implement a biomonitoring program.
• Review every road crossing of fish bearing waters to ensure free passage of fish.
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EPA RESPONSE: Suggestions noted for consideration during any future regulatory permitting
process.
Possible Measures to Limit Effects to Wildlife:
• At the planning stages, design aspects of the project to create or enhance wetland and
aquatic habitats for fish, bird, and wildlife species.
• Limit truck traffic on the haul road during migrations.
• Incinerate all kitchen waste.
• Educate workers on bear (or other wildlife) safety.
• Limit air traffic and noise during critical times of the year.
EPA RESPONSE: Suggestions noted for consideration during any future regulatory permitting
process.
WEBER SCANNELL RESPONSE: The reviewer agrees that many of the issues listed above
should be addressed during the regulatory process. The comment was initially made to
highlight the importance of a rigorous regulatory review.
The reviewer is satisfied and finds that the concerns have been addressed by additional
information in the revised Assessment.
EPA FINAL RESPONSE: No response required.
Paul Whitney, Ph.D.
Comments on Mitigation. The key word here is "reasonable." What is reasonable to a person not
involved in mining on a day to day basis will likely not be reasonable to a mining company executive
or mining engineer. The likelihood that "reasonable" means different things to different people is
exacerbated by the mixed messages regarding "best" mining practices (e.g., page ES-10, five lines
from the bottom) versus "not necessarily best" mining practices (e.g., page 4-17, four lines from the
top). As mentioned above, both of these statements can't be accurate. For purposes of this discussion,
I am assuming that there are many more mining practices that could be proposed to address many of
the uncertainties mentioned in the assessment. First of all, most of the mitigation measures
mentioned in the assessment provide one line of protection and I suspect there are many types of
redundant mitigation that could be implemented. Redundant protection such as: double-walled pipes
in all sections that cross floodplains (above and below grade); poly liner/vegetated caps to soak up
and capture run off water before it contacts waste rock; redundant clay, glacial till
(waste360.com/mag/waste_landfills_glacial_till); poly liners; and secondary liquid collection
systems.
EPA RESPONSE: We have revised the assessment to better explain the qualifying terms. What
was intended is that we have assumed modern conventional mining technology and operations.
The terms are qualitative when generally interpreted, or have a regulatory meaning ("best
management practices"), and thus we have eliminated their use in the revised assessment.
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Measures for minimizing and controlling sources ofpollution in other situations often are
referred to as best practices, state of the practice, good practice, conventional, or simply mitigation
measures. We assume that these types of measures would be applied throughout a mine as it is
constructed, operated, closed, and post-closure, regardless of the qualifier that one wishes to place
with it. To remove any ambiguity and subjectiveness of terms "good" or "best", we have removed
them in the revision and have added Box 4-1, which includes definitions for several terms used
Double-walled pipelines were included in the scenarios for sections above or beneath water bodies.
Redundant mitigation measures are appropriate for consideration during the permitting process.
I appreciate the assessment's discussion of the potential difficulties of using poly liners, but the
discussion might benefit from a review of Koerner et al. (2005) that provides another perspective on
the life of HDPE liners. The relationship of liner life to temperature is presented in their Table 2 and
a summary in the text indicates that covered liners have a "half life of 446 years at 20 degrees
Centigrade." This is a lot different from the 20 to 30 year estimate of service life cited in the
assessment on page 4-11 (last para). Appendix I does cite a 2011 version of the Koerner et al. (2005)
paper and appears to misquote it (page 9, last para, last full sentence). The Koerner et al. (2005)
paper estimates a "halflife of 446 years" not a "lifetime" of 446 years, as cited in Appendix I.
Perhaps Koerner updated his 2005 estimate in the 2011 version.
EPA RESPONSE: In the 2011 Koerner reference, there is conflicting text — the 446 years is listed
as the "lifetime", and later also as "half-life"; "449"years is also stated as the half-life and one is
referred to the Table in the report with the title of "Lifetime", where there is no such number. It
appears the author is using the terms half-life and lifetime to mean the same thing. Later in the
white paper, there is text that states "...its predicted lifetime (as measured by its half-life)...". The
following text has been used in Appendix I and is consistent with the reference: "...Koerner et al.
(2011) presents that a nonexposed HDPE liner could have a predicted lifetime ("as measured by
its half-life") of 69 years at 40°C to 446years at 20°C."
The discussion of liners has been moved to Chapter 4 in the revised assessment and includes 69 to
600 years as half-lives, based on Rowe 2005 and Koerner et al. 2011. The personal communication
reference has been removed.
WHITNEY RESPONSE: Thanks for looking into this issue and updating the text. EPA might
want to consider under what circumstances a non-exposed liner would experience 40 degree C
temperatures in the Bristol Bay watershed. 20 degree C might even be warmer than a non-
exposed liner would experience.
EPA FINAL RESPONSE: Laboratory tests and data from landfills estimate that high-density
polyethylene liner life spans range from about 450 to 600 years at 20°C, with longer service lives
expected at lower temperatures (Rowe 2005, Koerner et al. 2011).
I assume a mining engineer (if asked) could design a series of smaller impoundments or innovative
lined impoundments that could avoid a lot of the problems cited in the assessment. The trade-off
might be increased loss of natural resources due to a larger footprint and increased construction cost,
but the risk cited in the assessment and the risk of a catastrophic failure might be greatly lowered.
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EPA RESPONSE: An engineer could design a series of smaller impoundments that would likely
decrease the risk of catastrophic failure, but would impact a larger footprint and increase
construction costs. However, cumulative risk of failure would increase. More than one dam, even
if they are smaller, means a higher risk offailures, even if they contain less volume, as well as
more points where water management systems could fail, even if the dam itself does not.
I would be interested to know what THE BEST mining practices are. If the mitigation measures
mentioned in Appendix I are, in fact, the best, it should be so stated and taken into consideration in
the assessment. For example, page 4-21 of the assessment indicates the TSF would be unlined and
not have an impermeable barrier between the tailings and groundwater. Appendix I, page 9 indicates
TSFs can be lined if problems are expected. There is a lot of good information in the Koerner et al.
(2005) paper and Appendix I. It seems the types of mitigation measures in Appendix I could be better
captured in the main report.
EPA RESPONSE: The terms "best", "good" or other are qualitative when generally interpreted,
or have a regulatory meaning (best management practices when referring to storm water
measures). Measures for minimising and controlling sources ofpollution in other situations often
are referred to as best practices, state of the practice, good practice, conventional, or simply
mitigation measures. The multiple measures presented in Appendix I are options that might be
"best", depending on the site-specific conditions and any other constraints. More discussion on
mitigation measures has been added to the scenarios in Chapter 6 of the revised assessment.
Compensatory mitigation and reclamation are briefly mentioned in the assessment. A more detailed
discussion of the opportunities and feasibility of reclamation and compensatory mitigation might
reduce the likelihood of potential impacts of the example mine plan (see response to Question 3).
EPA RESPONSE: Mitigation to compensate for effects on aquatic resources that cannot be
avoided or minimized by mine design and operation would be addressed through a regulatory
process that is beyond the scope of this assessment. Nevertheless, in response to public and peer
comments we have included a discussion of compensatory mitigation in Appendix J of the revised
assessment.
3.15 Charge Question 13
Does the assessment identify and evaluate the uncertainties associated with the identified
risks?
David A. Atkins, M.S.
The Assessment states: the 'range of failures is wide, and the probability of occurrence of any of
them cannot be estimated from available data.' Uncertainty is addressed throughout the report,
typically with a qualitative discussion. There is a high degree of uncertainty with respect to how the
mine would be developed, operated and closed, as well as how any impacts would be mitigated. This
large uncertainty makes assessing risk difficult.
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EPA RESPONSE: No change suggested or required.
ATKINS RESPONSE: None.
EPA FINAL RESPONSE: No response required.
Steve Buckley, M.S., CPG
The assessment identifies some of the uncertainties associated with the identified risks but does not
evaluate these in great detail.
EPA RESPONSE: No change suggested or required.
Courtney Carothers, Ph.D.
The report includes specific sub-sections to discuss uncertainties for the risks associated with habitat
modification (Section 5.2.4), pollutants (5.3.4), and water collection and treatment failure (6.3.4).
Uncertainties related to abundance and distribution of fish in the watershed draining the mine site,
road and stream crossings, salmon-mediated effects on wildlife, salmon-mediated effects on human
welfare and Alaska Native cultures, tailings dam failure, pipeline failure, and road and culvert
failures are not discussed in separate sections; however, several uncertainties related to these risks are
noted throughout the report, and in summary sections (Sections 8.5 and 8.6).
EPA RESPONSE: We have added separate uncertainty sections to each of the major topics in the
risk assessment chapters.
CAROTHERS RESPONSE: EPA response is sufficient.
EPA FINAL RESPONSE: No response required.
The "sensitivity relative to overall results" of the key assumptions and uncertainties presented in
Table 4.8 in Appendix E (pp. 193-195) would be a helpful model to employ in the main report. For
non-experts in the technical dimensions of mine construction and operation, uncertainty rankings
would be useful. For example, "We are 'highly uncertain' about the accuracy of these predictions
given this unknown factor," or "We expect this uncertainty has a negligible effect on the model we
employ to calculate this risk."
EPA RESPONSE: The assessment has been restructured to consider certain impacts resulting
from the mine footprint (Chapter 7) separately from less certain impacts resulting from potential
failures (e.g., Chapters 8 and 9). For uncertainties considered in each chapter, we also have, when
possible, indicated a general categorization of (1) the level of uncertainty, and (2) the sensitivity of
our conclusions to this uncertainty.
CAROTHERS RESPONSE: EPA response is sufficient.
EPA FINAL RESPONSE: No response required.
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Dennis D. Dauble, Ph.D.
The most likely scenarios and probabilities of failure are described based on assumptions of project
size and magnitude. For the most part, estimated risks are conservative (i.e., effects are stated as
"likely" if no further information is available). A weakness of Integrated Risk Characterization
(Chapter 8 of the main report) is having a long list of identified uncertainties, which leads one to
speculate, "so what do we know?" Not being familiar with the formal risk assessment process, it
appears this "assessment" (which is loosely based on a risk assessment framework), falls short of
providing something with any degree of certainty.
EPA RESPONSE: The assessment does not state that effects are likely if no further information is
available. The assessment, as far as the available information allows, identifies potential events
and their effects, their probabilities of occurrence, and possible ranges. Uncertainties, inherent in
any risk assessment or mine plan, are clearly identified in the assessment.
DAUBLE RESPONSE: Either I have an improved understanding of risk assessment jargon as
a result of reviewing the document or the revised Assessment does a better job of explaining the
process.
EPA FINAL RESPONSE: No response required.
Gordon H. Reeves, Ph.D.
Uncertainties and limitations are explicitly identified and acknowledged for topics that I am familiar
with (fish and aquatic ecology and fish habitat) throughout the report. These are summarized
succinctly and clearly and the consequences to the findings are articulated.
EPA RESPONSE: No change suggested or required.
Charles W. Slaughter, Ph.D.
Yes. The authors fairly attempt (pp. ES-24-26, and in each chapter) to note the various uncertainties
and assumptions incorporated into the Assessment. Sections 8.5 and 8.6 briefly summarize those
uncertainties. A question remains concerning the "uncertainties" associated with assigning
probabilities to various failure scenarios; I remain unconvinced that those probabilities have real
meaning or significance for decision-making (see response to Question 5, above).
EPA RESPONSE: As explained in the assessment (particularly in Chapter 14), the probabilities
have various sources and different interpretations, which we have tried to make clear. Some of
them are more useful in decision making than others, but all are the best values that could be
derived from available information. Most are based on empirical frequencies, but some are
engineering goals or regulatory targets.
SLAUGHTER RESPONSE: The revised Assessment does fairly discuss uncertainties
associated with each sector; the authors have done a good job of outlining assumptions, data
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limitations, and the suite of "unknowns" contributing to uncertainty in projections. Similarly,
as mentioned earlier, the expanded discussion of use of probability analysis has been helpful.
EPA FINAL RESPONSE: No response required.
John D. Stednick, Ph.D.
The uncertainties are presented adequately.
EPA RESPONSE: No change suggested or required.
Roy A. Stein, Ph.D.
Uncertainties. I think that the Environmental Risk Assessment did a nice job of identifying
uncertainties surrounding this presentation, but a relatively poor job of quantifying them (at least
partially due to a lack of information). As a consequence, I found this section more than
disconcerting. Certainly, the authors have worked hard to present an accurate portrayal of the impact
of a large-scale open pit mine in the watershed of Bristol Bay. Even so, upon review of the list of
uncertainties with regard to this effort (pages 8-10 to 8-13), I conclude that we know little of what the
impact of this mine will be in any quantitative sense. Clearly, from the Environmental Risk
Assessment, we do know qualitatively what is likely to occur when a mine of this size and type will
be put into operation in this environment.
EPA RESPONSE: The goal of the assessment is to evaluate risks from large-scale mining to
salmon populations and secondary effects of salmon losses. Where applicable information was
available, we quantified our uncertainties to the extent possible. Where information was lacking,
we provided a qualitative assessment. This approach also reveals missing information that will be
needed for any future environmental assessment.
However, from the list of uncertainties, we are operating at the outside edge (and beyond in many
cases) of the semi-predictive models used in anticipating the impacts of the mine footprint, the
routine operations of the mine, and the impacts of failures of TSF, pipelines, and water/leachate
collections on extant salmon populations. And our knowledge of the baseline populations of the
seven species of salmonids is no better, for we do not know the size, diversity, distribution, or vital
rates (i.e., recruitment, growth, and survival across life stage) of these fishes.
EPA RESPONSE: We agree that we do not know everything we would like to know about fish
populations in the project area, but we do know the approximate extent of various species, and we
do know that spawning and rearing by salmon, Dolly Varden, and rainbow trout occur in the
project area. We summarize the types of risks to fish from plausible mine scenarios.
Couple these two sets of uncertainty and the prognosis outlined in the report is suspect, at the very
least, and somewhat anticipatory at best (I cannot bring myself to use the word "predictive"). I fully
realize that these are the cards the authors were dealt (I do applaud the authors for making the best of
an information-poor environment), but it seems to me that we are on tenuous ground when we
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attempt to predict the impact of the Pebble Mine on salmon, associated wildlife, and Native Alaskan
cultures in the Bristol Bay Watershed.
EPA RESPONSE: We agree that the assessment is not a definitive quantified prediction of all
impacts to salmon, wildlife, and Alaska Native cultures from large-scale mining. However, the
revised draft does develop more quantitative estimates of the implications of the mine scenarios
than the first review draft. The point of a risk assessment is to make the best prognostication
possible given the available information. The complexity of a large mine and of the receiving
ecosystems, as well as the unpredictability of the natural processes and human errors that would
challenge the integrity of a mine, make prediction tenuous even with the most detailed mine plan.
However, the assessment evaluates the likely impacts of a set of plausible mine scenarios, thereby
highlighting potential risks and impacts of concern. This will inform decisions going forward and
any NEPA or permitting processes in the future.
William A. Stubblefield, Ph.D.
The risk assessment attempts to identify and evaluate the uncertainties associated with each of the
recognized potential risks. The authors have, for the most part, successfully identified a number of
uncertainties that may affect the accuracy and conclusions of the risk assessment. Clearly, this
information should provide a basis for prospective mine planners and regulatory authorities to focus
their efforts to minimize potential environmental risks. In some cases the uncertainties identified are
probably best addressed through the development of additional data and this should guide future
research efforts undertaken prior to mine development and operation.
EPA RESPONSE: No change suggested or required.
STUBBLEFIELD RESPONSE: As discussed in my previous comments, the evaluation and
documentation of assessment uncertainties is critical to any risk assessment. This document has
clearly delineated the uncertainties associated with the various risk scenarios (both in the
executive summary and in the individual chapters). The revisions to the uncertainty section(s)
in this draft of the Bristol Bay assessment have been expanded, where appropriate, to address
concerns associated with revised assessment techniques. If I could offer one suggestion
associated with uncertainties would be that in the executive summary section "Summary of
Uncertainties and Limitations in the Assessment" some more specific mention should be made
of the uncertainties associated with the evaluation a toxicological endpoints and the
uncertainties associated with toxicological benchmarks. Most of these are delineated and
discussed in Chapter 8, Section 8.2.5. However, statements contained in the document like that
in Section 8.2.2.1 that states: "Based on the literature cited above and the author's experience,
resolution of this uncertainty by additional research and testing is likely to lower the chronic
criterion by approximately a factor of 2 and not as much as a factor of 10" suggest that the US
EPA believes that ambient water quality criteria may be significantly under protective of
aquatic organisms. If this is the case, clearly it is a source of major uncertainty and should be
identified as such.
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EPA FINAL RESPONSE: A statement has been added to the executive summary concerning
uncertainty in the aquatic toxicological endpoints.
Dirk van Zvl Ph.D., P.E.
The EPA Assessment does not identify the risks, only the likelihood of occurrence and the
consequences. See discussion under Question 4 above about risk. Uncertainties are identified and
evaluated for the likelihoods of occurrence and in some cases for the consequences. However,
because the magnitudes of the risks are not expressed, their uncertainties are also not explicitly
expressed.
EPA RESPONSE: We believe that the likelihood of an occurrence and its consequences constitute
an appropriate and generally accepted definition of risk. We have estimated those to the extent that
existing information allows.
The report identifies uncertainties in a number of sections, including in Chapter 8. In many cases,
these uncertainties are expressed in qualitative terms and are not quantified. The biggest
uncertainty/variability in the evaluation of a hypothetical project is associated with the potential
range of design features, waste management options and operational details that could be included.
This was completely overlooked in the analysis by assuming a specific design for the hypothetical
mine. The failure likelihoods and consequences on salmonid fish are very dependent on the
assumptions for the hypothetical mine. These uncertainties are neither clearly identified nor included
in the evaluations. This is a major shortcoming of the present analysis.
EPA RESPONSE: The comment is correct in stating that the scenarios are a major source of
uncertainty with respect to what might be implemented if an actual mine were developed.
However, the scenarios are intended to represent a mine using modern conventional practices and
are based on the preliminary mining plan put forward by Northern Dynasty Minerals as
"permittable" (Gliaffari et al. 2011). Any future plans put forward would undoubtedly differ, and
a permitted mine plan would differ from that put forward by the mining companies. The actual
operation of a mine, in turn, inevitably differs from the approved plans. Rather than attempt to
estimate the uncertainties in predicting all of those changes in plan, EPA chose to put forward
reasonable and typical scenarios, estimate some associated risks, and describe the uncertainties
associated with the risk estimation. Identification of the risks associated with a typical mine can
inform initial mine design and the NEPA and permitting processes. The revised draft makes this
clear.
VAN ZYL RESPONSE: No further comments on Question 13.
EPA FINAL RESPONSE: No response required.
Phyllis K. Weber Scannell, Ph.D.
The important features of the Environmental Assessment are to describe the fish, wildlife, and human
use of the subject area and to define possible risks from development of a large porphyry copper
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mine. There are many uncertainties associated with the identified risks and most were identified in
the document. The document could be strengthened by putting a greater emphasis on sources of
contamination (such as mine seepage, poorly designed collection systems, exposed pit walls, etc.) in
relation to the permeability of the soils.
EPA RESPONSE: The revised assessment includes more emphasis on sources of contamination
(e.g., diesel pipeline failure, quantitative wastewater treatment plant failure, and a refined seepage
scenario) and their potential hydrologic transport including through permeable soil and rock.
WEBER SCANNELL RESPONSE: The reviewer is pleased that the revised Assessment
included more in-depth discussions of sources of contamination.
The reviewer is satisfied and finds that the concerns have been addressed by additional
information in the revised Assessment.
EPA FINAL RESPONSE: No response required.
The 5th bullet on page 8-11 outlines important uncertainties for protecting fish species. These
uncertainties include life-stage-specific sensitivities to temperature, habitat structure, prey
availability, and sublethal toxicities. These factors must be considered should a mining project go
forward.
EPA RESPONSE: We agree with this comment. No change suggested or required.
WEBER SCANNELL RESPONSE: The reviewer agrees that no change is required.
The reviewer is satisfied and finds that the concerns have been addressed by additional
information in the revised Assessment.
EPA FINAL RESPONSE: No response required.
The 6th bullet on this page discusses the preliminary nature of leaching test data. These tests must be
sufficiently comprehensive to predict both short term and long term water quality from all sources,
including PAG and NAG waste rock, pit walls, and pyritic tailings.
EPA RESPONSE: We used the available leaching test data and agree with the comments about
future tests.
WEBER SCANNELL RESPONSE: The reviewer agrees that no change is required.
The reviewer is satisfied and finds that the concerns have been addressed by additional
information in the revised Assessment.
EPA FINAL RESPONSE: No response required.
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Paul Whitney, Ph.D.
Uncertainty summary. The discussion of uncertainties in the assessment is, in most cases,
appropriate. It seems that one could use these discussions as a scope for additional work needed prior
to an assessment that would properly assess risk of the example mine. As the uncertainty discussion
appears in the assessment, this reader wonders what to make of it. There is a lot of uncertainty in this
world that we find acceptable; the ultimate goal seems to determine if the cumulative uncertainty is
acceptable or not. Such an evaluation remains to be made and I'm not sure how it could be made
based on the level of information presented in the assessment and the current state of the uncertainty
discussions.
EPA RESPONSE: The goal of the risk assessor is to describe the uncertainty, not determine
whether it is acceptable. The acceptability of existing uncertainty is a judgment made by the risk
manager, who nmst decide whether to make a decision or defer the decision until more
information is available.
The summaries of uncertainty included in Sections 8.5 and 8.6 could be improved if some sort of
realistic and useful conclusion(s) could be presented. The Section 8.6 summary seems to "pile on"
uncertainties, rather than summarize the uncertainties in the assessment. While piling on is
informative, it is not the sort of summary I was looking for. Conclusions in the Section 8.5 summary
of conclusions remind us that the effects of mining on fish populations could not be quantified and,
as a substitute, the effects on habitat were used as a surrogate. So we are left with an estimate of 87.5
to 141.4 km of streams that would be removed and this would cause an adverse effect. Based on this
very general risk conclusion, we learn that "In summary, it is unlikely that there would be significant
loss of salmon subsistent resources related to the mine footprint" (page 5-77, last paragraph). First,
it's not clear how this conclusion was reached. Second, if such a conclusion was possible for
subsistent resources based on the data available, why couldn't such a conclusion be reached for sport
and commercial fisheries? Third, does it follow that no significant loss to salmon subsistence
resources would result in no significant loss to wildlife that utilize this resource? If so, such an
indirect analysis is not informative regarding an environmental assessment for the example mine.
Alternatively, a direct assessment of the loss of habitat using habitat-based population models for
both fish and wildlife would be much more informative.
EPA RESPONSE: Uncertainties are now discussed in each chapter of the assessment so they can
be more closely associated with a particular topic.
Additional information on the geographic scope of subsistence use in the area has been added to
the assessment and the conclusions clarified accordingly. Although there is some (incomplete)
information on subsistence use areas, similar data are lacking for the geographic scope of sport
and commercial fishing in the watershed
WHITNEY RESPONSE: The above response doesn't answer my question. Does EPA stand by
its conclusion of unlikely significant loss of salmon-subsistent resources related to the mine
footprint?
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EPA FINAL RESPONSE: Our conclusions about effects on subsistence salmon resources from
the mine footprint are explained in Section 12.2. Although there are no documented salmon
fisheries in the mine scenario footprints, these areas are usedfor harvesting other fish and wildlife
species. We also state that there are likely to be negative impacts on downstream salmon fisheries
from headwater disturbance and that those residents who use areas immediately downstream for
harvesting salmon and other fish would be most affected. Based on the available information, we
stand by the conclusions that there are currently no salmon harvesting areas within the scenario
footprints, but that there are likely to be effects on downstream salmon subsistence fisheries. It
should be noted that subsistence harvest data have some limitations, as outlined in Section 5.4.2.2.
There is not sufficient data to quantify the loss of salmon as a subsistence resource under various
scenarios or to quantify the fish-mediated effects to wildlife. Discussions of these topics have been
expanded to illustrate the complexity of the interactions and provide further qualitative
assessment. Direct effects on wildlife from habitat loss related to large-scale mining are outside of
the scope of this assessment.
Adaptive Management. Holling (1978) in his Adaptive Environmental Assessment and Management
book discusses political uncertainty and how adaptive management might be able to address the
issue. Considering that the mine being proposed is a multi-century system, it's poignant to realize
that Alaska was owned by Russia about 150 years ago and Oregon was being claimed by the Spanish
about 200 years ago.
EPA RESPONSE: The commenter is correct in pointing out the inapplicability of adaptive
management to decisions like whether to permit large scale mine development in the Bristol Bay
watershed Not only is the time horizon inappropriate, but mine permitting decisions cannot be
remade iteratively like the resource management decisions for which Hollings and Walters
developed adaptive management (e.g., setting annual fishing limits). However, careful monitoring
and revision of permit conditions, although not literally adaptive management, could have some of
its benefits. Monitoring requirements and provisions for modifying permits are beyond the scope
of this assessment.
Adaptive management is a tool designed to deal with uncertainties in risk evaluations (Ruhl and
Fischmann 2010). If implemented properly, with testable hypotheses of risk, adaptive management
may be something to consider for the example mine. My experience with adaptive management is
that adequate funds are seldom allocated to learn by doing, to test hypotheses and to implement new
management if hypotheses are not met. Formalizing financial instruments to ensure that funds are
available is equally difficult to negotiate. Nonetheless, I agree with Ruhl and Fischmann that the
theory of adaptive management is sound and may be the only way to deal with uncertainties such as
climate change. Considering the number of uncertainties identified in the assessment, for the scope of
work to clearly state hypotheses, to address the uncertainties, to fund studies to test the hypotheses,
and to fund alternative management if hypotheses are not met is cumulatively daunting. For example,
there are about 50 state variables in each of the Site Model Figures (3-2A, B, C and D). All totaled,
that's about 200 (50 x 4 figures) state variables for salmon alone. Considering there are 100s more
species, that's about 20,000 (200 x 100 species) state variables. Then there are fluxes/linkages
between the state variables and that is another 20,000 fluxes/linkages that should be monitored. For
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adaptive management to work, clear goals and hypotheses to assess whether observed data meet the
goals should be stated for approximately 40,000 variables and linkages. Then there is the task of
defining the monitoring methods and statistics to determine whether or not goals for the variables and
linkages are being met. I acknowledge that there are probably ways to trim down the monitoring
effort, but one can start to imagine the enormity of implementing a monitoring plan for adaptive
management. Then there is also what to do if goals are not realized. I am not aware of any alternative
to adaptive management other than contingency planning which often lacks the "learn by doing"
feature of adaptive management.
EPA RESPONSE: See response to previous comment.
Important wordsmithing. So many of the uncertainty evaluations make statements about certain
parameters that "could not be predicted" (page ES-20, para 4); "could not be quantified" (e.g., page
6-11, second full para); or are "unpredictable" (page 5-44, para, line 8). These are just a few of many
examples. It would be more acceptable, at least to me, to state that estimates were not included in the
assessment. This type of wording occurs in some parts of the assessment and might be more accurate.
EPA RESPONSE: Changes have been made in Chapter 7 (formerly Chapter 5) and Chapter 9
(formerly Chapter 6).
Vague wording. The assessment includes a lot language that seems vague, at least to me. The list is
long but includes: "highly pure water"; "other ecological responses"; "key wildlife"; "essential
wildlife"; "overall ecosystem functioning"; "serious population-level consequences"; "different
thermal characteristics"; "could be locally significant"; and "very long time." Lackey (2001)
acknowledges the need for scientists to communicate with the public using normative science but
expresses concerns that normative descriptors such as ecosystem health are subject to wide
interpretation. He suggests that the most direct alternative to using normative science is to simply and
clearly describe what is being discussed. The assessment would benefit if the normative type words
used above (any many more) were quantified with estimates, a range or some type of measureable or
testable parameter.
EPA RESPONSE: The authors have tried to be precise with the language of the assessment and
avoid normative terms. Changes to the text of the revised assessment have been made with this
comment in mind
3.16 Charge Question 14
Are there any other comments concerning the assessment, which have not yet been
addressed by the charge questions, which panel members would like to provide?
David A. Atkins, M.S.
Long-term risks from development of an open pit have not been characterized. It is difficult to
predict the chemistry of the lake that will form in the open pit, but there is some potential that water
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quality will be poor, which may be exacerbated by pit backfilling with waste rock. The pit lake could
impact waterfowl and may have some impact on groundwater if there is outflow when the lake
reaches an equilibrium level.
EPA RESPONSE: The potential pit was not assessed because it is not anticipated that salmon or
other fish (the primary assessment endpoint) would reach it. Therefore, it is out of scope. However,
a pit lake as a potential source of water to streams is briefly considered in the revised Chapter 8.
The scenarios no longer include the placement of acid generating waste rock in the pit at closure.
ATKINS RESPONSE: This response is adequate.
EPA FINAL RESPONSE: No response required.
Steve Buckley, M.S., CPG
None.
Courtney Carothers, Ph.D.
None.
Dennis D. Dauble, Ph.D.
Based on public comments and discussions that took place by panel members in Anchorage August
7-9 of this year, this report confuses in both intent and approach. Is the intent of EPA's assessment
to characterize potential impacts to the Bristol Bay watershed (title) or does it address a more defined
portion of the Nushagak River and Kvichak River watersheds (objective statement)? Was the
approach an "assessment" (a fairly broad term) or an "ecological risk assessment" (suggests a
specific scientific framework was applied to the risk/effects analyses)? These shortcomings should be
addressed in the final assessment document.
EPA RESPONSE: We have revised the discussion of purpose, scope and endpoints in response to
this and other similar comments (see Chapters 1 through 5 of the revised assessment). The
assessment addresses multiple spatial scales, as detailed in Chapter 2. It is an ecological risk
assessment, but that term is usually shortened to assessment to make the document more readable.
DAUBLE RESPONSE: My concerns and questions on the intent and approach of the
assessment were adequately addressed.
EPA FINAL RESPONSE: No response required.
Gordon H. Reeves, Ph.D.
The major issue that was not considered in the assessment was the potential impact of climate
change, particularly regarding the form and timing of precipitation. Admittedly, there is uncertainty
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about the magnitude of changes that will result from climate change, which makes it difficult to
consider. However, the potential consequences of climate changes on such topics as tailing site
facilities, water availability, and culvert failure seem appropriate. It will also be important to
consider potential impacts of climate change so their signal can be distinguished from potential mine
impacts during any monitoring that occurs.
EPA RESPONSE: Climate change projections, including increases in precipitation, are addressed
in Chapter 3 of the revised assessment. Projected precipitation increases are used as the basis for a
qualitative discussion of the link among changes in precipitation, hydrology, and mining including
site facilities, water availability, and culverts (Box 14-2). This box also discusses the importance of
monitoring impacts of climate change to distinguish between potential impacts of climate change
and potential impacts from the mine.
Charles W. Slaughter, Ph.D.
I would simply re-emphasize that a truly comprehensive assessment of the potential consequences of
a large-scale mineral extraction project, be it the "hypothetical" Pebble-like project or a different
endeavor, should fully consider both the immediate project-specific impacts, and the long-term
watershed-wide consequences of "ancillary" developments - such as other mines, which might
become economic once the primary project's infrastructure is in place. There should be full
recognition of the irreversible nature of such developments, and of the potential and limitations of
possible reclamation or mitigation measures for the full suite of resources and ecosystem "services"
involved, both short-term and long-term.
EPA RESPONSE: Ecological risk assessments generally have more limited scopes than
comprehensive environmental impact statements. This document is not meant to be a
comprehensive evaluation of all impacts potentially stemming from a large-scale mine, and its
scope has been more clearly defined in Chapter 2. We have added discussion to the cumulative
assessment chapter (Chapter 13) to emphasize the long-term watershed-wide consequences of
ancillary or induced development. We have added a discussion of compensatory mitigation in
Appendix J.
SLAUGHTER RESPONSE: Concur with the response. The entire Assessment is a major step
forward from the 2012 draft. The detail provided in all sectors, particularly in the hydrologic
("water balance"), water quality, and cumulative effects sectors, is really appreciated.
EPA FINAL RESPONSE: No response required.
John D. Stednick, Ph.D.
There are several references to streamflow measurements that would be especially helpful to better
characterize the site. The US Geological Survey has some streamflow gauging stations and
precipitation records that would complement the analysis. Annual precipitation values were derived
apparently from a computer model used to analyze global climate change at University of Alaska
Fairbanks. How do these data compare to field measurements? The prediction of a 10, 50, 100, or
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larger event using a short-term precipitation record, results in a larger error term on the predicted
streamflow. How common is the occurrence of rain on snow (ROS) streamflow events?
EPA RESPONSE: U.S. Geological Survey and PLP data are presented in Chapter 7 of the
assessment. We believe the SNA P data used in the assessment to be the best available for
summarizing precipitation inputs to large areas; these data have been updated from the May 2012
draft of the assessment. We used accepted, published data to estimate the size of the probable
maximum flood We do not make estimates of 10, 50, or 100 year events.
Dust production and transport: A variety of mining processes will generate dust. What are the wind
patterns, chemical composition, and opportunity to land in surface waters or wetland areas? What
potential is there for metal or toxin transport? Overburden removal will require explosives that leave
nitrate, ammonia, and often sulfur in the air. What about this transport? Or rain out?
EPA RESPONSE: Stressors evaluated in the assessment were based on how they would
significantly affect our primary endpoint of interest (the region's salmon resources) and their
relevance to EPA's regulatory authority and decision-making context. Although fugitive dusts
from mining operations are a potential source of contamination to streams, and should be
considered in a regulatory permitting process, they are not considered as significant as other
stressors chosen for the assessment and are not regulated under the Clean Water Act. Discussions
of transport dust and associated potential impacts are now included in Chapter 10.
The literature cited is often dated or lacking. The technical review panel has proposed numerous
references that can be used to strengthen the document.
EPA RESPONSE: We have reviewed all references suggested by the peer reviewers to the extent
possible, and have incorporated information where applicable.
Roy A. Stein, Ph.D.
IN PERPETUITY
Sustainable Salmon vs. One-Time Mine. Some irony exists as one considers the trade-off
between salmon and this mining operation (and make no mistake, we cannot have both
mining and productive salmon stocks in the Bristol Bay watershed). We are trading
sustainable salmon stocks that, with science-driven management, rigorous regulatory
oversight, and limited exploitation, should provide salmon literally 1000s of years into the
future against the development of a mine that will provide minerals in the relative short term
(within 25 to 78 years). As a result of the mining operation, the government (and likely it
will be the state or Federal government) will be saddled with a 1000 years (at a minimum,
based on the assessment) of monitoring and maintenance of this closed-mine site.
EPA RESPONSE: No change suggested or required
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MINERAL NEEDS
Strategic Needs. I was surprised that no section of the Environmental Risk Assessment
included any justification for why copper (does mining copper fulfill a strategic need for the
United States; most all sites I researched do not list copper as a strategic mineral for our
country), gold, molybdenum, and some additional rare earth elements were needed within the
context of our economy. Are other sources available? Are these specific elements in short
supply? Are they required for the United States to compete in worldwide markets regarding
cell phones, other electronic devices, or solar panels? For example, rhenium is used in the
aviation industry and some web sites suggest it is critical to our defense industry. Some
justification would have helped me understand this huge undertaking.
EPA RESPONSE: We agree that the strategic need for these resources should be discussed
in the broader NEPA environmental assessment process, but this topic is beyond the scope
of this assessment.
ORGANIZATIONAL ISSUES
Page 5-59. I struggled throughout the document with organizational issues. As I read more
and more text, I had the sense that I had read these facts or these perspectives previously. I
mention this above but it is here on page 5-59 that the issue is nicely summarized. Note the
text in the last paragraph of the page, where it discusses all of the important issues associated
with roads and stream crossings. My suggestion would be that these sections (for every
topic) be combined such that one section would exist for Roads, one for the Pipelines, etc. In
so doing, the reader can capture all of the relevant information about a specific aspect of the
mine in a single section of the report. I believe this would improve impact, readability, and
shorten the report substantially (and also serve to reduce what seems to be a fair amount of
redundancy).
EPA RESPONSE: We have reorganized the document in response to this and similar
comments to improve readability and clarity.
Pages 6-10 to 6-11. These pages reflect another example of redundancy. Text to this point
discussed and reviewed just how long we might expect the fine sediments to persist in rivers
and streams post tailings dam failure. Yet, here again, on pages 6-10 to 6-11, these numbers
are reiterated. Combining these sections would help the reader and reduce redundancy.
EPA RESPONSE: The TSFfailure analysis was formerly split between two chapters and
has now been combined into one (Chapter 9).
Section 6.3, Pages 6-36 to 6-42. Not to beat a dead horse, but in this section, nearly all of
the citations to tables and figures are to those tables and figures that are found in sections of
the report other than Section 6. This organizational scheme is what makes the report
cumbersome to read and follow the logic and the argument.
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EPA RESPONSE: The assessment has been completely reorganized, as suggested by
reviewers.
William A. Stubblefield, Ph.D.
None.
STUBBLEFIELD RESPONSE: No additional comments are provided.
EPA FINAL RESPONSE: No response required.
Dirk van Zyl, Ph.D., P.E.
The EPA Assessment mentions twice that "interactions with regional stakeholders" and interactions
with members of the Intergovernmental Technical Team were used to refine the analysis, etc. (p. ES-
2 and p. 3-6). A robust stakeholder process includes careful documentation of the stakeholders
identified during the project (which may include stakeholder mapping), records of meetings (attendee
lists, meeting notes, etc.), resolution of differences, etc. The EPA Assessment does not contain any
references to any such materials, which implies to me that the stakeholder process was informal and
not robust.
EPA RESPONSE: Details on stakeholder involvement in the assessment process have been added
in Box 1-1.
VAN ZYL RESPONSE: The addition of Box 1-1 provides very useful information for readers
of the Second Draft.
EPA FINAL RESPONSE: No response required.
Phyllis K. Weber Scannell, Ph.D.
At present, Pebble remains a prospect and there is no plan of operations for the mine. Should the
project move forward to development of a mine, it will be necessary to develop an in-depth mining
plan of operations. The mining plan should include the following:
• Transportation - of equipment and personnel and for shipping ore. Transportation of
ore, including loading facilities, wheel washing, and other measures to prevent ore
spillage and contamination.
• Siting of mine facilities, including tailings ponds, waste rock storage areas,
concentrate storage area, bypass systems for clean water, and collection systems for
contaminated water.
• Mill operations, including a description of the process for concentrating ore.
• Chemical and fuel storage and Spill Prevention and Contingency Plans.
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• Personnel housing, including handling of domestic waste (sewage, garbage).
• Water treatment plant. Processes that will be used, anticipated concentrations of
metals and TDS, anticipated discharge volumes, and predicted mass loadings.
• Monitoring plans for seepage from tailings ponds, waste rock storage areas, etc.
Monitoring likely will include a series of wells and possibly, a pump-back system.
• Predictions for acid rock generation and measures that will be put in place during
mining to minimize future seepage from the mine site.
• Plans for concurrent reclamation and future closure of the mine.
• Specifications for sufficient bonding to provide site stabilization and water treatment
in the event of a premature or temporary shut-down and reclamation at closure.
EPA RESPONSE: The comnienter is correct that these are important points that should be
considered in evaluation of a mining plan once submitted. No change suggested or required.
WEBER SCANNELL RESPONSE: The reviewer agrees that many of the issues listed above
should be addressed during the regulatory process. The comment was initially made to
highlight the importance of an in-depth mining plan and rigorous regulatory review.
The concerns raised by the reviewer in Question 14 have been addressed by the additional
information contained in the revised Assessment. The reviewer especially notes the expanded
descriptions of waste water management and potential failures, the descriptions of permitting
for large mines in Alaska (Box 4.2), the need for more in-depth sampling for PAG and NAG
and the expanded descriptions of potential sources of toxicity.
EPA FINAL RESPONSE: No response required.
After the Mine Plan of Operations is developed, an environmental assessment plan should be
developed that identifies potential effects to fish and wildlife and their habitats from specific
components of the mine (as listed above). In addition, the assessment should include cumulative
effects of nearby mines (if appropriate) on fish and wildlife habitats and water quality.
EPA RESPONSE: The comnienter is correct and we would expect these things to be considered
during the regulatory permitting process. No change suggested or required.
WEBER SCANNELL RESPONSE: The reviewer agrees that many of the issues listed above
should be addressed during the regulatory process. The comment was initially made to
highlight the importance of an in-depth mining plan and rigorous regulatory review.
The concerns raised by the reviewer in Question 14 have been addressed by the additional
information contained in the revised Assessment. The reviewer especially notes the expanded
descriptions of waste water management and potential failures, the descriptions of permitting
for large mines in Alaska (Box 4.2), the need for more in-depth sampling for PAG and NAG
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and the expanded descriptions of potential sources of toxicity. In addition, Box 4.2 describes
permit requirements.
EPA FINAL RESPONSE: No response required.
Among the most important issues that must be addressed are transportation, potential for acid mine
drainage and metals leachate, control of point and non-point pollution, and developing the mine for
future closure.
EPA RESPONSE: The commenter is correct and we would expect these things to be considered in
more detail during the regulatory permitting process. No change suggested or required.
WEBER SCANNELL RESPONSE: The reviewer agrees with the EPA response. The comment
was initially made to highlight the importance of an in-depth mining plan and a rigorous
regulatory review.
The concerns raised by the reviewer in Question 14(2) have been addressed by the additional
information contained in the revised Assessment. The reviewer especially notes the expanded
and clarified descriptions of possible effects from transportation (including roads and culverts)
and metals toxicity to fish.
EPA FINAL RESPONSE: No response required.
Paul Whitney, Ph.D.
Here are a number of other comments that do not fit neatly under the first 13 questions:
1. Unquantifiable wetland and riparian loss. There are many parameters that are supposedly
unquantifiable. An example "unquantifiable" parameter is the area of riparian floodplain
(page ES-14). Another example is the "unquantifiable area of riparian floodplain and wetland
habitat that would be lost..." (page 8-2, first sentence). There are many methods to
characterize or delineate riparian floodplain and wetland. For example, information in Table
5-23 and associated text on page 5-69 characterize wetland loss within 100 and 200 meters of
the road. This is a rather crude method but it is at least an estimate. Perhaps it would be
accurate to say that the area of riparian floodplain and wetland habitat lost was not
characterized. Such a statement would be more internally consistent with statements that the
natural system is "incompletely characterized" (page ES-25). Better yet, characterize the
wetland and riparian habitat losses using one of the many existing methods. Section 8.2 is a
good start. An explicit list of wetland and riparian loss estimates seems important for an EPA
review. Once a list of potential wetland and riparian losses is tallied, the next question is
whether or not it would be possible to compensate for such an impact. If it is not possible, it
might not be possible to achieve no net loss of wetland resources.
EPA RESPONSE: We agree that greater quantification of wetland and riparian losses is
essential for the NEPA and permitting processes that oversee compensatory mitigation and
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"no net loss". This assessment is based on existing information (including wetland
inventories) and, as the commenter has pointed out, reveals the areas where existing
information is lacking.
2. Combinations and Permutations of analyses. The review of the assessment is somewhat
complicated by the relationship of certain analyses to following analyses and so on. Take, for
example, the use of the Mount St. Helens eruption as a surrogate for a tailings dam failure.
One could assume that such an analogy is inappropriate and recommend that it be deleted
from the assessment. If this recommendation was followed for an initial baseline, all
subsequent information on distance moved, toxicity, remediation, and duration of impact
would no longer apply and would presumably be deleted. Alternatively, EPA might further
develop the Mount St. Helens eruption analogy and demonstrate why it is a useful part of the
assessment. If this is the case, the related following (i.e., secondary) information presented on
distance moved, toxicity, remediation, and duration would be retained. Then, it is appropriate
for a reviewer to comment on the adequacy of the following secondary information. Then, it
is a possibility that the secondary or following information is not accurate and the reviewer
has to consider that it could be dropped or retained. Soon, a reviewer of the assessment
document is wondering how to address an unwieldy and hard to follow combination of
initial, secondary, and tertiary events. More likely than not, most reviewers do not consider
all the combinations and recommendations. As a result, the reviewers' comments could fall
short of adequately addressing the restructuring of the main assessment. In short, EPA should
not assume that following the reviewers' comments will result in an assessment that
addresses the next iteration of initial, secondary, and tertiary comments.
EPA RESPONSE: We believe that this comment raises an important point. We did delete
the analogy to Mount St. Helens ash, as recommended by other peer reviewers. However,
as the comment indicates, that leaves the assessment with no analysis of recovery of
salmonid streams from the deposition of large volumes of fine particulate material
3. Address all levels of ecology. Ecological resources can be characterized at many levels of
organization. Populations are often characterized by birth and death rates. Communities are
often characterized by species diversity, succession, and associations of species. Ecosystems
are often characterized by structure, function, nutrient cycling, and energy flow. From a
wildlife perspective, the assessment does a fine job of discussing marine-derived nutrients
but concludes that ".. .the fish mediated risk to wildlife - cannot be quantified given available
data..." The assessment could be improved if information regarding community and
ecosystem parameters were quantified (or at least addressed at the level that marine-derived
nutrients were addressed). Woolington (2009) comments on the importance of certain serai
stages for wildlife. I am confident that an interview with him, reclamation specialists, and
others at ADF&G could provide a lot of information on community succession, plant
diversity, and wildlife habitat relationships. This information, in addition to the insight
provided in Appendix C, would provide a much better understanding of possible mine
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impacts and opportunities for compensatory mitigation. It is also possible that traditional
knowledge of villagers might provide insight to understanding plant community and
ecosystem parameters.
EPA RESPONSE: Ecological risk assessments are not intended to address all levels of
biological organization. Rather, as described in the Guidelines for Ecological Risk
Assessment (USEPA 1998), they focus on a limited number of assessment endpoints that
are most likely to influence a decision because of their importance and susceptibility. The
endpoints were selected in consultation with stakeholders and decision makers. Further,
even if more consideration of the effects of marine-derived nutrients on terrestrial plant
communities were included, the salmon-mediated effects of the mine on wildlife still could
not be quantified. We have clarified the assessment scope, and recognize that numerous
other important ecosystem components also could be affected.
4. Ecosystem evaluation. The Ecosystem Integrity Section (2.3.5) seems to miss the mark. It
mentions the "nearly pristine conditions," with the caveat that approximately 70% of salmon
returning to spawn are commercially harvested. This is then described as a managed and
sustainable landscape. Maintaining a sustainable resource is not an accurate characterization
of a nearly pristine ecosystem. First of all, sustainability means a lot of different things to
different people. For example, forests in the Pacific Northwest are managed in a sustainable
way but the ecosystem is hardly pristine. Hilborn (2005) discusses the multiple definitions of
sustainability. Instead of deciding which definition he likes the best, he indicates that
sustainability is like good art - it's hard to describe but we know it when we see it. Second,
Hilborn (2005) states: "The record shows clearly that almost all forms of human activity -
agriculture, forestry, urbanization, industrialization, and migration - reduce biodiversity of
natural flora and fauna. This is almost certainly the case with fishing as well." Hilborn
acknowledges the sustainability of the Bristol Bay fishery but I doubt if he would claim that
there is no impact of the fishery on the ecosystem of Bristol Bay.
EPA RESPONSE: Additional information on commercial fisheries management has been
added to Chapter 5 of the revised assessment. However, the purpose of this assessment is
not to assess the relative effects ofpotential mining and commercial fishing—it is to
evaluate potential effects on endpoints if a mine were to be developed, given existing
conditions and activities in the region.
WHITNEY RESPONSE: Hilborn clearly states that fishing most certainly has a
negative impact on biodiversity which is a negative impact. The negative past, current
and future impact of the Bristol Bay Fishery should be addressed in the Cumulative
Impact Analysis.
EPA FINAL RESPONSE: Text has been added to Chapter 5 and Chapter 7 that provides
further detail regarding marine-derived nutrient (MDN) dynamics and acknowledges that
escapement increases would lead to higher MDN inputs to these systems (although this
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may not translate into increased salmon production, particularly where other factors are
limited).
The scope of the cumulative portion of this assessment refers to cumulative risks of mining
in the watershed, not a cumulative evaluation of all potential impacts in the watershed
Thus, evaluation of commercial fishing impacts is outside the scope of this assessment.
Rather than emphasizing the nearly pristine conditions and sustainability of the fishery, I
suggest that other measureable characterizations of the aquatic and terrestrial ecosystem be
measured and quantified. For example, a description of plant communities and succession
would provide the reader with a better understanding of how plant communities are naturally
maintained, and subsequently, how possible mining activities might alter the successional
processes. Failure to address and understand such relationships led to unexpected
consequences for downstream plant communities, wildlife diversity, and village residents in
the Peace Athabasca (Cordes 1975) Delta when the Bennett Dam was built hundreds of miles
upstream on the Peace River. The drastic changes in the ecosystem function were related to
changes in just a few inches of water in the delta at certain times of the year. The Bristol Bay
assessment would be improved if the expected changes in the hydrographs and sediment
transport were related to the successional processes that maintain early successional plant
associations such as the alder-willow association, which is important for moose. The write up
for moose (Appendix C, page 33) indicates that these early successional associations are
maintained by bank scouring. It would be good to know the role of ice dams and anchor ice
on current levels of scouring and how changes due to mining might alter these important
sustainable functions. The assessment's emphasis on fish and fish mediated impacts runs the
risk of missing possible impacts on the terrestrial environment and downstream
sedimentation that would not only influence human culture but also the aquatic environment.
The impact on terrestrial resources and wildlife is not inconsequential to aquatic resources, at
least in my opinion. Throughout my evaluation, I cite references that discuss the importance
of specific associations between fish and wildlife.
EPA RESPONSE: A comprehensive assessment of potential impacts of large-scale mining
would need to consider all levels of ecological organization. The scope of this assessment,
however, is much narrower, as described throughout the problem formulation chapters
(Chapters 1-6). We clarified the assessment scope, and recognize that numerous other
important ecosystem components also could be affected.
5. Multi-directional fish and wildlife relationships. The assessment's emphasis on marine-
derived nutrients and the reduction of this salmon-derived resource only looks at a one-way
fish to wildlife interaction. Wildlife to fish functions, such as beaver dam building, are very
important wildlife to fish interactions. Both salmonid fish, as well as forage fish, receive
benefits from beaver functions such as tree felling, dam building, and food storage
(Snodgrass and Meffe, 1997; Schlosser and Kallemeyn, 2000). This issue is briefly
mentioned in Section 5.2.1.2 (para 1) and discussed on pages 5-19 and 5-22, but needs to be
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expanded to address the benefits for fish. The dynamic process of dam construction and dam
decay is important, not only for moving streams across the flood plain, but also for creating a
mosaic of plant associations and wildlife (e.g., moose) habitat in and near the floodplain. In
addition, such activities create a mosaic of habitat for forage fish. An accurate
characterization of the impact of a potential mine and road necessitates, not only an
assessment of the loss of fish on wildlife, but also the loss of wildlife and their functions on
fish. The influence of wildlife and terrestrial processes and functions on fish discussed in the
Cederholm papers needs to be included in the problem formulation step. The dynamic
process of beaver dams causing creeks to move across the floodplain should also be a criteria
for determining if and where culverts, versus bridges or causeways) are installed for a
potential road (pages 4-36 and 4-63).
EPA RESPONSE: Text has been added discussing the functional role of beaver dams in
Chapter 7. The discussion of wildlife in Chapter 5 has been expanded to acknowledge the
complexity of fish/wildlife interactions in the watersheds. Please note that the assessment
does not use beaver activity as a criterion for determining what type of structure (bridge vs.
culvert) would be constructed at each crossing. The revised assessment assumes that
crossings over streams with mean annual flows greater than 0.15m3/s would be bridged
However, the actual decision as to what type of structure would be constructed at each
crossing would be made by industry engineers in consultation with state permitting staff.
WHITNEY RESPONSE: Go Beavers!!! Nice job.
EPA FINAL RESPONSE: No response required.
6. Measuring fish wildlife interactions. Understanding and addressing the multi-directional
interaction of fish and wildlife are facilitated by an approach developed by the Northwest
Habitat Institute, introduced in Johnson and O'Neil (2000) and elaborated on the Northwest
Habitat Institute web site (nwhi.org). The Interactive Biodiversity Information System (IBIS)
database allows an assessment of fish and wildlife interactions and functional
characterizations (i.e., ecosystem functions). The IBIS database is a logical extension of the
Jack Ward Thomas Wildlife Habitat Relationships and the GAP analysis for the Pacific
Northwest. Such an analysis could build on information in the Alaska GAP database and the
Natural Heritage Program database in Alaska.
EPA RESPONSE: A comprehensive assessment of potential impact of large-scale mining
would need to consider all levels of ecological organization and interaction. The scope of
this assessment, however, is much narrower, as described throughout the problem
formulation chapters (Chapters 1-6). We clarified the assessment scope, and recognize that
numerous other important ecosystem components also could be affected.
7. Ecological risk assessment for toxic chemicals. The amount of information in the assessment
pertaining to ecological toxics risk is impressively large. The amount of time and team
expertise needed to adequately review this information is well beyond the scope of the
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proposed review. If a team was assembled to review this information, I would ask them to
consider:
a. The applicability of a probabilistic risk assessment to address some of the
uncertainty associated with the deterministic information presented in the
assessment;
b. Stressors in addition to toxics (e.g., habitat loss, noise, human
disturbance, light, and water warming in the winter); and
c. The relationship of stressors to populations in addition to no observed
effect levels.
I have worked on large scale impact assessments where the stress of habitat loss far exceeds
the potential stress of toxics. I would think EPA would want to know whether or not this is
the case for the example mine in their assessment.
EPA RESPONSE: The revised draft assessment evaluates the potential impacts from
habitat loss and toxic releases from plausible mine scenarios based on existing information
about the watersheds. The review panel includes an expert on aquatic toxicology who did
provide an excellent review of that material.
WHITNEY RESPONSE: Stubblefield is an excellent resource but I don't recall him
assessing the relative importance of toxic risk to loss of habitat risk. I remember asking
Stubblefield during one of the Anchorage Meetings with the peer group: Should risk to
habitat be addressed in an ecological risk assessment. He said yes. So it seems that a
salmon endpoint based on habitat should be considered jointly with the toxicological
component of the risk assessment.
The first draft mentioned gold as a resource but after talking to other peer reviewers I
was assured that gold ore would not be processed on site. The revised draft indicates
that pyrite tailings would be processed on site using a cyanide heap leach process. Given
this addition, it seems appropriate to mention the possibility of an accident while
transporting cyanide to the processing site. Similar analyses for the Crown Jewel
Project in Washington indicated a cyanide transportation spill into or near a creek
would have acute short-term impacts for many miles downstream. I would like to know
if ethyl xanthate, the primary chemical of concern in the revised assessment, is more
toxic than cyanide?
EPA FINAL RESPONSE: The endpoint is an attribute of a potentially affected ecological
entity. Habitat modification and toxic chemicals are stressors. Both are assessed in this
document.
An accidental spill of cyanide during transport is now addressed in Chapter 10 and has
been added to the Chapter 14 summary. Sodium ethyl xanthate as a potential stressor is
addressed in Chapters 8 and 11.
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8. My only regret in this review is that I could not visit the proposed mine site and watersheds
during the summer and the winter. I have flown over the Bristol Bay watersheds while
working for other mines in Alaska, but I have never been on the ground in these watersheds. I
am concerned that if I did visit the proposed sites my assessment points above might change
and even change dramatically. It is hoped that all the EPA staff and biologists working on the
assessment are able to visit the watersheds in the summer and winter.
EPA RESPONSE: No changes suggested or required.
3.17 Specific Observations
David A. Atkins, M.S.
1. Global: All significant figures should be reviewed to make sure they are reflective of the
level of uncertainty (i.e., using an estimate of 141.4 km of streams eliminated when this value
is probably realistically +/- 50%).
EPA RESPONSE: All significant figures in calculations and measurements made by EPA
have been reviewed and changed to reflect the uncertainty of the analysis. For example km
of stream is reported to the km Significant figures from cited documents are as reported in
the original document.
ATKINS RESPONSE: This response is adequate.
EPA FINAL RESPONSE: No response required.
2. Global: Many references cited in the text are not included in the reference list.
EPA RESPONSE: References have been updated.
ATKINS RESPONSE: This response is adequate.
EPA FINAL RESPONSE: No response required.
3. Global: The executive summary, main report, and appendices, in many instances, present
different information with sometimes different implications. These three levels of detail of
information should be more cohesive.
EPA RESPONSE: We have re-written the executive summary and main report to make
them more consistent with each other and the appendices.
ATKINS RESPONSE: This response is adequate.
EPA FINAL RESPONSE: No response required.
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4. Page ES-24 (P2): Suggest changing 'Cumulative Risks' to 'Cumulative Effects of Multiple
Mine Development.'
EPA RESPONSE: The title of the chapter (now Chapter 13) was changed.
ATKINS RESPONSE: This response is adequate.
EPA FINAL RESPONSE: No response required.
5. Page 3-2 (PI): The justification for excluding ancillary development from the assessment
should be better explained. In some instances, opening up an area for natural resource
development has had as much or more impact on the environment and ecosystems as the
development itself (for example, oil and gas development in some areas of the Amazon
Basin)
EPA RESPONSE: Discussion of ancillary mining infrastructure (in addition to the pit,
TSFs, waste rock piles, roads and pipelines) has been added to Box 6-1, and discussion of
induced development (development which follows initial development in an unimproved
setting) has been added to Chapter 13.
ATKINS RESPONSE: This response is adequate.
EPA FINAL RESPONSE: No response required.
6. Page 3-7 to 3-11: The conceptual models are quite helpful, but are not referenced or utilized
sufficiently when discussing impacts. It would be helpful to more fully incorporate them into
the assessment.
EPA RESPONSE: Sub-components of the conceptual models have been included at the
outset of the risk analysis chapters, to better frame the pathways evaluated in each chapter.
ATKINS RESPONSE: This response is adequate.
EPA FINAL RESPONSE: No response required.
7. Page 4-1 (PI, L9): Why does the assessment describe current 'good' and not 'best' practice?
The rationale for this decision needs to be described. In addition, it is likely that anything
other than 'best' practice would not be permitted in this context.
EPA RESPONSE: With regard to the terminology of "best", "good", or other terms for the
practices used, what was intended to be conveyed in the assessment is that we assumed
modern mining technology and operations. The terms are qualitative when generally
interpreted, or have a regulatory meaning. The term "best management practices" is a
term generally applied to specific measures for managing non-point source runofffrom
storm water (40 CFR Part 130.2(m)). Measures for minimizing and controlling sources of
pollution in other situations are referred to as best practices, state of the practice, good
practice, conventional, or simply mitigation measures. We have added a text box in the
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revision Chapter 4 to discuss terms. Mitigation measures considered feasible, appropriate,
and 'permittable' (as per Ghaffari et al. 2011) were considered in the assessment, and
these are measures common to other copper porphyry mines.
ATKINS RESPONSE: This response is adequate.
EPA FINAL RESPONSE: No response required.
8. Page 4-11 (P3, L10): The liner lifetime is quite low, and given the importance of this
assumption, would warrant more than a personal communication that does not appear in the
references (North pers. comm.).
EPA RESPONSE: The discussion of liners has been expanded and moved to Chapter 4
(Section 4.2.3.4) in the revision. The personal communication reference has been removed.
ATKINS RESPONSE: This response is adequate.
EPA FINAL RESPONSE: No response required.
9. Page 4-21 (PI, L4): Is the assumption about the TSF locations from the authors or from the
Wardrop 43-101 report?
EPA RESPONSE: The location of the TSFs is a combination of alternative sites described
in Ghaffari et ah 2011 (the Wardrop report), in the NDM 2006 Water Rights Application
(see reference list for Chapter 6), and our knowledge of site characteristics suitable for
tailings impoundments.
ATKINS RESPONSE: This response is adequate.
EPA FINAL RESPONSE: No response required.
10. Page 4-26 (S4.3.7-Water Managment): It would help to provide appropriate ranges for
numbers (e.g., the precipitation at the mine and TDF is 803 and 804 mm/yr, respectively,
which implies an unrealistic degree of certainty). It would also be helpful to include a
diagram. I am uncertain why 'cooling tower' water losses would be included in the mine
water balance since power generation would likely be at a remote location and other impacts
from power generation are not considered in this assessment.
EPA RESPONSE: In general, we have presented our best estimates for the parameter
values discussed in the assessment and have used these estimates in our analyses and
calculations. A full uncertainty analysis is beyond the scope of this assessment, so we have
provided ranges only for critical parameters such as the mine size. We followed the
Ghaffari et ah (2011) mine plan in placing power generation on the site, which is the
reason for the natural gas pipeline. Therefore, water use for cooling is appropriate.
Net precipitation at the mine site has been recalculated. The monthly mean flows for each
gage were summed across the year, producing an area-weighted average of860 mm/yr.
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Ghaffari et al. (2011) describe the construction of a combined-cycle natural gas-fired gas
turbine power plant at the mine site and estimate the cooling tower evaporative and drift
losses from the plant. The cooling tower losses were included because they would
constitute a substantial consumptive water use.
ATKINS RESPONSE: This response is adequate.
EPA FINAL RESPONSE: No response required.
11. Page 4-31 (P3, L6): How was the filling time of 100 to 300 years for the pit estimated? What
constitutes full (e.g., within x% of the pre-mining water table)?
EPA RESPONSE: The filling time was calculated from the estimated inflow rate to the
empty pit. Most of the groundwater infiltration would come from the uppermost 100 m and
the direct precipitation rate would be constant, so the filling rate would not decrease
significantly until the water level was close to the surface compared to the pit depths. We
recognize that as the water level approached the surface, the cone of depression would
shrink and the filling rate would decrease. We have not attempted to refine our analysis to
account for this decrease in rate and the available data do not merit such a refinement.
The filling time was simply calculated by dividing the pit volume by the inflow rate. In
practice, when the pit was full the pit level would be maintained below the overflow level by
pumping if treatment were required or be allowed to establish a natural outlet at its low
point if treatment was not necessary.
ATKINS RESPONSE: This response is adequate.
EPA FINAL RESPONSE: No response required.
12. Page 4-52: The PMP is based on the Miller (1963) reference (not included in the reference
list). How was it estimated?
EPA RESPONSE: The PMP was based on Technical Paper No. 47
(http://wMnv.nws.noaa.gov/oh/hdsc/PMP_documents/TP47.pdf). This PMP was used as the
precipitation input to a Type-1 (for Alaska) HEC-HMS simulation to calculate a runoff
hydrograph. 291 cms was determined to be the peak discharge from this 24-hour design
storm
ATKINS RESPONSE: This response is adequate.
EPA FINAL RESPONSE: In the final assessment, flooding to generate overtopping is no
longer simulated.
13. Page 5-22: Should refer to 'recapture efficiency' rather than 'recovery rate'. How were the
values of 16% and 63% derived?
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EPA RESPONSE: The words "recovery rate" were meant to be descriptive and not as a
defined technical term. There is no standard term in widespread usage for the parameter
reported (i.e. the percentage of excess water available for reintroduction into the streams
versus the total amount captured by the mine processes). In the revised assessment, we
have changed the wording to "reintroduced" (Table 6-3, Section 6.1.2.5). The
reintroduction percentages were calculated as part of the water balance. The water balance
totaled all the sources of water captured per year and then subtracted all of the annual
consumptive water losses. The remaining annual volume of water is excess water that the
mine does not need for operations and which is available for reintroduction to the streams.
The ratio of the annual reintroduced volume to the annual captured volume yields the
reintroduction percentage.
ATKINS RESPONSE: This response is adequate.
EPA FINAL RESPONSE: No response required.
14. Page 5-23: The mean annual unit runoff values are not reproducible from the values given for
drainage area and measured mean annual flow.
EPA RESPONSE: These values have been corrected.
ATKINS RESPONSE: This response is adequate.
EPA FINAL RESPONSE: No response required.
15. Page 5-32 to 5-39: Tables showing flow changes for different mine sizes and figures for
minimum mine size are difficult to interpret. A different presentation method and/or narrative
description would help.
EPA RESPONSE: Tables, figures, and text for this section have been revised
ATKINS RESPONSE: This response is adequate.
EPA FINAL RESPONSE: No response required.
16. Page 5-45 (S5.2.3): The preceding section (Section 5.2.2) focuses on 'Effects of Downstream
Flow Changes' and Section 5.2.3 focuses on wastewater treatment. It is not clear why this is
the sole focus of Section 5.2.3. In addition, only a short paragraph is included in this section.
Certainly there are other possible risks beyond water treatment, and even this discussion is
too cursory given the importance of the issue.
EPA RESPONSE: Discussion of water treatment has been expanded in Chapter 8 (a new
chapter in the revised assessment).
ATKINS RESPONSE: This response is adequate.
EPA FINAL RESPONSE: No response required.
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17. Page 5-45 (S5.2.4): This section states a number of assumptions that could result in under or
over estimating impacts on stream flow from the mine footprint. This section leaves the
impression there is a lot of uncertainty, both with assumptions behind the estimation and with
how successful any attempts at mitigation may be. Therefore, we are left with very large
error bars on estimates that should be reflected in the numbers presented for loss of length of
streams and areas of wetlands.
EPA RESPONSE: We have improved the rigor of the analyses regarding the impact of
mining on stream/low. We have attempted to be very explicit about our assumptions and
approaches, and we believe the analyses are appropriate and defensible.
ATKINS RESPONSE: This response is adequate.
EPA FINAL RESPONSE: No response required.
18. Page 5-46 (P3): This paragraph discusses the possibility that estimates of stream length
blocked by mine construction may be overestimated if engineered diversion channels are
successful. This is an important form of mitigation that needs to be evaluated further. It
would be helpful to evaluate mitigation efforts in similar types of systems to determine if
reconstructing streams is feasible and could be successful.
EPA RESPONSE: Appendix J includes a discussion of the efficacy of constructed
spawning channels. There is little evidence in the scientific literature to suggest that such
channels are effective at creating suitable spawning habitat. Furthermore, there is nothing
in the scientific literature that suggests salmon streams could be successfully reconstructed
in landscapes where significant alternations in area soils, hydrology and groundwater flow
paths have occurred, such as would be the case with the mine scenarios described in the
assessment.
ATKINS RESPONSE: This response is adequate.
EPA FINAL RESPONSE: No response required.
19. Page 5-59 (Bullet 4): Whole effluent toxicity (WET) testing and downstream biotic
community monitoring would likely be part of any discharge permit. This requirement would
not preclude developing a better understanding of protective discharge chemistry and
temperature requirements before permitting, especially given the quality of the receiving
water.
EPA RESPONSE: Appropriate WET testing and downstream biotic monitoring would be
desirable if a mine were permitted. Additional studies of site specific chemistry and
temperature tolerances may also be desirable. No change required.
20. Page 5-60 (S5.4.2): The statement that mine traffic will not be a large enough volume to
affect runoff needs support. Do we know the road will only be used for mine traffic? Can we
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estimate the volume of mine traffic for a mine of this size and then look at runoff from an
analog system?
EPA RESPONSE: This statement has been deleted from the assessment. However, we
found no analogous data that would allow us to quantify runoff
ATKINS RESPONSE: This response is adequate.
EPA FINAL RESPONSE: No response required.
21. Page 5-60 (S5.4.4.1): How was the number of stream crossings determined (e.g., what
criteria were used to define a stream vs. a channel)?
EPA RESPONSE: All USGS designated streams were included. No artificial channels
were identified and all natural channels are streams.
ATKINS RESPONSE: This response is adequate.
EPA FINAL RESPONSE: No response required.
22. Page 5-65 to 5-68 (S5.4.8.2): Text states that 240 km of stream upstream of the transportation
corridor has a gradient greater than 10% and, therefore, is likely to support fish. Should this
be less than 10% (as stated in the header to Table 5-22 and Table 6-9)? If so, how was the
<10% value chosen?
EPA RESPONSE: The comment is correct, though in the revised assessment we use <12%
as the criterion and cite a relevant source.
ATKINS RESPONSE: This response is adequate.
EPA FINAL RESPONSE: No response required.
23. Page 5-74 (S5.5): Salmon-mediated effects on wildlife seems under-analyzed in the report,
particularly when compared to the information presented in Appendix C.
EPA RESPONSE: The discussion of potential salmon-mediated effects on wildlife has
been expanded (Chapter 12).
ATKINS RESPONSE: This response is adequate.
EPA FINAL RESPONSE: No response required.
24. Page 5-75 (S5.6): As above, salmon-mediated effects on Alaska Native Cultures seems
under-analyzed in the report, particularly when compared to the information presented in
Appendix D.
EPA RESPONSE: The discussion of potential salmon-mediated effects on Alaska Native
cultures has been expanded (Chapter 12).
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ATKINS RESPONSE: This response is adequate.
EPA FINAL RESPONSE: No response required.
25. Page 6-3 (S6.1.2.1): I don't find the Mt. St. Helens analogy useful.
EPA RESPONSE: It has been removed.
ATKINS RESPONSE: This response is adequate.
EPA FINAL RESPONSE: No response required.
26. Page 6-9 (PI, LI): Why would 'present' resident and anadromous fish not suffer habitat loss
in the event of a TSF failure? Are they upstream of the area inundated?
EPA RESPONSE: Yes, these populations are upstream of the TSF-affected area. However,
they may be impacted by barriers to seasonal movement or fragmented by loss of
connectivity. This has been clarified in the text.
ATKINS RESPONSE: This response is adequate.
EPA FINAL RESPONSE: No response required.
27. Page 6-28 (S6.1.5): The 'Weighing Lines of Evidence' section is not well developed and not
particularly useful. It also does not inform the risk characterization and uncertainty
discussion.
EPA RESPONSE: EPA believes that it is important to weigh all relevant lines of evidence.
An explicit weighing allows readers and reviewers to see what was weighed and how it was
weighted. Such transparency is desirable in general. Therefore, the weighing of evidence
has been expanded and the method is better explained.
ATKINS RESPONSE: This response is adequate.
EPA FINAL RESPONSE: No response required.
28. Page 6-30 (PI, L2): The statement that risks of failure of the gas and diesel pipelines are not
considered because they are not particularly associated with mining makes no sense. Without
the mine, there would be no need for the pipeline. And if the types of failures and risks are
well known, then this is one of the areas that could actually be assessed with some degree of
certainty.
EPA RESPONSE: Diesel pipeline failure has been added. A gas pipeline is still not
assessed because it is judged to not pose a potentially significant risk to fish (see Chapter
11).
ATKINS RESPONSE: This response is adequate.
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EPA FINAL RESPONSE: No response required.
29. Page 6-36 (S6.3, P2): Designating closure as 'premature closure,' 'planned closure,' and
'perpetuity' with water treatment ceasing immediately, continuing until permits are
exhausted or water is nontoxic, or until institutions fail does not seem reasonable. Any of
these closure scenarios would be planned, and would involve regulatory compliance reviews,
bonding, etc. Walking away without continuing to collect and treat water would be an
unlikely scenario. The issue of treatment in perpetuity is a larger issue that needs to be treated
in detail.
EPA RESPONSE: The premature closure scenario is intended to address the possibility
that the closure plan is not followed. It highlights the need for adequate bonding and for
plans that include closure by the bond-holding agency.
ATKINS RESPONSE: This response is adequate.
EPA FINAL RESPONSE: No response required.
30. Page 6-37 (P4, L4): The report states that (acid generating) waste rock could be left in place
in the event of premature closure. This scenario should be addressed in the mine closure plan
and during the closure bonding process.
EPA RESPONSE: The premature closure scenario is intended to address the possibility
that the closure plan is not followed. It highlights the need for adequate bonding and for
plans that include closure by the bond-holding agency.
ATKINS RESPONSE: This response is adequate.
EPA FINAL RESPONSE: No response required.
31. Page 8-1 to 8-2: Given that this chapter discusses overall risk to salmon, it would be helpful
to put the estimates of km lost in terms of the total stream or watershed available habitat. We
need some context and metric for assessing significance.
EPA RESPONSE: In Table 2-1, we have explicitly expressed the relative areas of each
spatial scale as % of the scale above it (e.g., the % of the entire Bristol Bay watershed made
up of the Nushagak and Kvichak River watersheds, the % of the Nushagak and Kvichak
River watersheds made up of the mine scenario watersheds, etc.).
ATKINS RESPONSE: This response is adequate.
EPA FINAL RESPONSE: No response required.
32. Page 8-2 (S8.1.2): The focus on a few types of catastrophic failures does not reflect the
current typical mining scenario. Based on experience at other mines, it is more likely that
smaller-impact failures and accidents would occur during the mine life. It would be helpful to
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use some current case studies to illustrate this point.
EPA RESPONSE: The number of possible types, magnitudes, and combinations of
failures and accidents is virtually infinite. Therefore, we used a bounding strategy. The
potential effects are bounded by those of routine operations and a realistic severe failure or
accident. We also cite case studies from recent review's of mining failures and individual
failure cases to indicate some of the possibilities.
ATKINS RESPONSE: This response is adequate.
EPA FINAL RESPONSE: No response required.
33. Page 8-3 (T8-1): Why would most concentrate pipeline failures occur between stream and
wetland crossings?
EPA RESPONSE: Most of the transportation corridor is not on or adjacent to a stream or
wetland. Therefore, most failures would occur in those areas between stream and wetland
crossings.
ATKINS RESPONSE: This response is adequate.
EPA FINAL RESPONSE: No response required.
Steve Buckley, M.S., CPG
1. Page xii: ICF is referred to in the document page xvi, but not listed as acronym or
abbreviation.
EPA RESPONSE: ICF is the name of one of the contracting companies that has worked
on the assessment, and is only referred to as ICF in the introductory material (thus is not
included as an acronym or abbreviation).
2. Page ES-2 (P2, L5-6): "altered by geologic processes by would not degrade..." is unclear
EPA RESPONSE: Metals do not degrade but their chemical form may be altered (via
speciation, binding, formation of salts, etc.). This is explained in the revised Executive
Summary.
3. Page ES-24 (P4, L2): "geologic defects" in unclear.
EPA RESPONSE: This was clarified in the revised assessment.
4. Page 1-1 (P3, LI): "17 existing mine claims..." should read "existing claim blocks"
EPA RESPONSE: Corrected.
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5. Page 4-11 (P3, L10): "North pers. comm." There is no reference, date, or information on
North.
EPA RESPONSE: The discussion of liners has been expanded and moved to Chapter 4
(Section 4.2.3.4) of the revised assessment, and includes additional material and references
on liner lifetime. The personal communication reference has been removed
6. Page 5-20 (P4, L3): The "northeastern United States" not comparable to western Alaska.
EPA RESPONSE: We agree that these two regions differ in many important ways, but the
general patterns of headwater contributions of nutrients and other resources is shared
between them, as reflected in the numerous citations of studies from Alaska that follow in
this paragraph.
7. Page 7-1 (PI, L5): "claims blocks" should read "claim blocks."
EPA RESPONSE: Corrected.
8. Page 7-3 (P3, L4): As above
EPA RESPONSE: Corrected.
9. Page 7-6 (P2, L5): As above
EPA RESPONSE: Corrected.
10. Page 7-7 (P2, P4): As above
EPA RESPONSE: Corrected.
11. Page 8-1,2 (P2, P3): In the discussion of removal of stream kilometers and wetlands it would
be helpful to express these numbers in a percentage of the overall watershed stream
kilometers and wetlands to put perspective on these numbers.
EPA RESPONSE: In Table 2-1, we have explicitly expressed the relative areas of each
spatial scale as % of the scale above it (e.g., the % of the entire Bristol Bay watershed made
up of the Nushagak and Kvichak River watersheds, the % of the Nushagak and Kvichak
River watersheds made up of the mine scenario watersheds, etc.).
Courtney Carothers, Ph.D.
1. Page ES-2 (P3): "wildlife and the Alaska Native cultures of this region."
EPA RESPONSE: The Executive Summary has been rewritten to incorporate this change.
2. Page ES-5 (P2): "Chief among these resources are world-class commercial, sport, and
subsistence fisheries for Pacific salmon..."
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EPA RESPONSE: Language added to the revised assessment.
3. Page ES-8 (last P): 1. Should Alutiiq (Sugpiaq) cultural group also be included? Alutiiq
residents noted in Igiugig and Kokhanok (Appendix D, p 15). 2. Change 2nd sentence to: "In
contrast, the salmon base upon which indigenous peoples in the Pacific Northwest depend is
severely threatened."
EPA RESPONSE: 1. Although there are residents of other cultural groups in the
watersheds, the predominant cultures are Yup'ik and Dena'ina, so we have focused on
these groups but have added mentioned of the Sugpiaq/Alutiiq. 2. This sentence has been
edited.
CAROTHERS RESPONSE: In response to specific observation #3, the Revised
Assessment now includes the mention of "Aleut/Alutiiq people" inhabiting the Alaska
Peninsula (Revised Assessment, p5-2). Should this be rewritten as "Aleut/Unangan and
Alutiiq/Sugpiaq peoples," or is the cultural group being referred to only the
Alutiit/Sugpiat? If the latter, "Alutiiq/Sugpiaq people" should be used to be consistent
with current published usage. If the former is true, that both Aleut/Unangan and
Alutiiq/Sugpiaq peoples inhabit this region, it should be rewritten as "Aleut/Unangan
and Alutiiq/Sugpiaq peoples" for clarity. While many Alutiiq/Sugpiaq people refer to
themselves as Aleut in the English language, the usage of Aleut/Alutiiq is confusing. The
standard usage of Alutiiq/Sugpiaq is preferable.
EPA FINAL RESPONSE: We have added Box 5-1 to the final assessment, which
recognizes the Sugpiaq cultural group, acknowledges the descendents of this group in the
watershed, and clarifies that we focus on the primary cultural groups in the Nushagak and
Kvichak River watersheds, the Yup'ik and the Dena'ina. We have changed the reference
from "Aleut/Alutiiq" to "Sugpiaq" in Chapter 5.
4. Page ES-9 (PI): "Salmon are integral to the entire way of life in these cultures as subsistence
food, fishing and subsistence-based livelihoods, and as the foundation for..."
EPA RESPONSE: Language added to the revised assessment.
5. Page ES-9 (P2): "52% of the subsistence harvest, although for some communities this
proportion is substantially higher" (e.g., noted to be as high as 82% on pg 93 of Appendix
D).
EPA RESPONSE: Language added to the revised assessment.
6. Page ES-10 (PI): Could also add replacement value for subsistence resources or for salmon,
and the range of estimates for economic valuation of subsistence presented in Appendix E,
noting of that economic valuations do not fully capture the value of these practices.
EPA RESPONSE: Language added to the revised assessment.
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7. Page ES-14 (#1): Are these all the fish spp. at risk, or only the one deemed to be
commercially, recreationally valuable? Subsistence spp also include others. Should make
clear what the focus is.
EPA RESPONSE: This sentence refers to the sockeye being particularly at risk because
they spawn and rear below the road. Commercial or recreational value is not considered
8. Page ES-23 (P3): As noted above, other mines in Alaska (e.g., Red Dog) and oil and gas
development studies on North Slope may be useful to include predictions about how
subsistence practices will change with mining development and perceived impacts. Including
citations with these statements would be helpful.
EPA RESPONSE: Chapter 12 has been expanded to include discussions of and references
to studies of impacts to subsistence practices from resource extraction industries.
9. Page ES-23,24 (last P): "if salmon quality or quantity is adversely affected (orperceived to
be affected)"
EPA RESPONSE: Language added to the revised assessment.
10. Page ES-26 (last bullet): There is much data on cultural disruptions caused by the Exxon
Valdez oil spill, and cumulative effects of oil and gas development in North Slope region,
current salmon shortages in Yukon-Kuskowkim. Clearly subsistence is not about lost food,
but about lost lifeways, loss of practices, loss of teaching/learning, and loss of identity. This
point could be made more forcefully. While the specific impacts may not be entirely
predictable, there are likely outcomes that could be included based on experiences in other
regions of the state and/or world.
EPA RESPONSE: The point suggested was made more forcefully in Chapter 12 of the
revised assessment.
11. Page 1-2 (P2): "this assessment does not provide an economic or social cost/benefit
analysis..."
EPA RESPONSE: Language added to the revised assessment.
12. Page 2-15 (PI): Other important subsistence fish spp not listed in Table 2-5, e.g., whitefish
and winter freshwater fish are listed as integral subsistence species in Appendix D. Again
make focus here clear.
EPA RESPONSE: Scope of the assessment and the specific assessment endpoints
considered have been clarified in Chapters 2 and 5. Table 5-1 has been incorporated from
Appendix B to give a more complete view of the fish species found in the watershed
13. Page 2-18 (S2.2.4): The net economic valuation ranges presented in Table 73, Appendix E
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would be helpful to include here.
EPA RESPONSE: Because the assessment is not meant to be a cost-benefit analysis, we
only briefly consider the economic value of the assessment endpoints. In addition, Table 73
deals with the economic value of moose, caribou, and brown bear, which are only
considered in terms of fish-mediated effects.
14. Page 2-19 (last sentence): "because no alternative food sources are economic viable." This is
a bit of a misrepresentation. The point is that people choose to live subsistence lifestyles.
Even if food at the stores was cheap, many would choose not to substitute for subsistence
hunting, fishing and gathering. This narrow economic framing misses the cultural and
lifestyle component of subsistence, and frames it merely as food procurement. This is not the
case throughout the document, but in this instance I would suggest changing this sentence to
reflect the irreplaceability of the subsistence lifestyle (dependent on access to high-quality
foods) rather than the economic viability of substituting alternative food sources.
EPA RESPONSE: The revised assessment expands the discussion of the cultural and
lifestyle importance of subsistence (Chapters 5 and 12). The economic viability of
alternative foods is mentioned in Chapter 12, but in the context of a variety of benefits of
subsistence.
15. Page 2-20 (first sentence): Here and in Appendix D, the legal framework for federal and state
definitions of subsistence should be clarified. Several times in Appendix D an indigenous
subsistence priority is noted (e.g., pg 88: "No other state in the United States so broadly
grants a subsistence priority to wild foods to indigenous peoples as does Alaska."). The
authors should clarify what they mean by indigenous preference (i.e., as opposed to rural
preference?) in state and federal subsistence management. They should include particular
references and additional clarifying information.
EPA RESPONSE: Citations were included in Appendix D in response to this comment.
16. Page 3-2 (PI): "would be benign or have no effect on the environmental or social systems,"
EPA RESPONSE: Discussion of scope has been rewritten (Chapter 2).
17. Page 3-4 (PI): ".. .provide subsistence for Alaska Natives and others." Particularly because
subsistence is defined as a rural right in Alaska, all subsistence users should be included as
potentially affected groups.
EPA RESPONSE: References to non-Alaska Natives who practice a subsistence way of life
have been included in the assessment. However, the focus remains on Alaska Natives.
18. Page 3-11 (Fig 3-2E): This conceptual model appears less developed than the others. It would
interesting to work on expanding it out to include missing dimensions; e.g., add health and
healing activity (in addition to nutrition), cultural continuity (alongside social relations and
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linked to language and traditional ways of teaching). With a decrease in economic
opportunities comes an increase in reliance on transfer payments. Overall it is a nice
illustration, but strikes me as less complete than the others.
EPA RESPONSE: The conceptual model has been revised and expanded in response to
this comment.
19. Page 4-15 (Table 4-3): Estimation of 200,000 metric tons of ore processed per day is much
higher rate than any of the other mining operations listed in Table 4-4. Is this due to the
low/moderate quality of the ore?
EPA RESPONSE: Initially, we utilized the ore production rate that was available in
Ghaffari et al. (2011), but we have added a smaller sized scenario to the revised assessment
to be similar to the worldwide median-sized porphyry copper mine. Processing throughput
is generally a function of the quality of ore and the cost of mining and processing the ore.
Ghaffari et al. (2011) state: "The process is based on conventional grind-crush-float
technology, using proven plant equipment of the largest sizes that have been industrially
installed", which suggests that mining rates are limited also by the size of proven mineral
processing equipment.
20. Page 4-21 (last P): 208 m high dam is "much higher than most existing tailings dams." What
are average dam heights? Or how much higher than most existing tailings dams? Does this
high height affect probability of failures?
EPA RESPONSE: Table 4-1 presents dam heights at other Alaska mines, all of which are
significantly lower than 209 m Higher dams mean larger impoundments, storing more
tailings; thus, if failure occurs, more waste material can be released
21. Page 4-23 (P2): "a well field spanning the valley floor." This is unclear. Could it be added to
Fig 4-7? How often would groundwater be monitored?
EPA RESPONSE: The revision clarifies this sentence, adding that installation would be at
the downstream base of all tailings dams to monitor groundwater flowing into the valley. It
was not added to the revised figures primarily to keep the figure from becoming too busy.
22. Page 5-48 (PI): "effluents would be required to meet criteria." How different is treated
discharged water from unaffected water?
EPA RESPONSE: Estimates of wastewater composition have been added to the assessment
(Table 8-9). Background surface water data are presented in Table 8-10.
23. Page 5-59 (2nd bullet): Is there any information available on ore processing chemicals, how
much are used, and likely toxicities?
EPA RESPONSE: The toxicity of sodium ethyl xanthate, the primary processing
contaminant of concern, is now considered (Section 8.2.2.5). However, its concentration in
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tailings and concentrate slurries cannot be estimated with any reasonable confidence due
to the lack of publicly available information.
24. Page 5-76 (bullet list): The list of cultural factors that may be negatively impacted could
include others: individual, community, and cultural identity; sense of place and place
attachments; community sustainability; cultural unity/conflict avoidance.
EPA RESPONSE: The list of cultural factors that could be negatively impacted was
expanded in the revised assessment.
25. Page 6-46 (bullet list): In addition to the two listed, another should be added noted that
subsistence practices (harvesting, processing, sharing, consuming) are important for
psychological, social, emotional, and cultural health and well-being.
EPA RESPONSE: This section was clarified to focus on nutritional benefits. The
discussion of health benefits from subsistence practices was expanded elsewhere.
26. Page 6-47 (PI): "...the physical, psychological, social, and cultural benefits of engaging in a
subsistence lifestyle..."
EPA RESPONSE: Revision made.
27. Page 6-47 (PI): References should be added (and were included earlier in the report) for the
statement: "would likely employ a small fraction of Alaska Natives."
EPA RESPONSE: This section has been revised and references the experience of other
Alaska Native communities.
COMMENTS SPECIFIC TO APPENDIX D
1. Single-space for consistency with the rest of appendices
EPA RESPONSE: Appendix D has been single-spaced.
2. The title is a bit misleading. Only eight pages in the report discuss traditional ecological
knowledge, and here not in much depth.
EPA RESPONSE: The TEK section was expanded.
3. The research design, methods, and data analysis should be described in more detail. Clarify
sampling procedure (both for communities and individuals). For example, it is unclear if
younger generations, particularly active subsistence harvesters, were targeted as well as
elders and culture bearers. Interview protocol should be included clearly as an Appendix.
EPA RESPONSE: The methodology section has been expanded Villages were asked to
identify Elders and culture bearers for interviews. Younger generations and/or subsistence
harvesters were not targeted but could have been included by villages for interviews.
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4. This section may make a few overstatements (e.g., "only in Alaska are wild salmon
abundant").
EPA RESPONSE: Comment noted and taken into consideration during revisions.
5. P12 - "those outside of the state." Change to "outside the region," as many urban Alaskans
are not familiar with subsistence communities.
EPA RESPONSE: The text has been revised.
6. PI2 - "Since the questions dealt with a cultural standard, there were few alternative points of
views." Should cultural agreement be a matter of investigation rather than assumed? This
statement needs to be justified. Perhaps with the authors' 40+years of experience working
with these communities they have come to expect cultural agreement, especially among
elders. If this is the case, that should be clarified. To what extent did group interviews (2-6
people interviewed together, except for one single interview) also contribute to cultural
agreement? These details are important given that the results are given on an agree/disagree
format.
EPA RESPONSE: The text has been revised to clarify this point.
7. PI7 - 2,738 is listed in Table 2 and 2,329 is listed here.
EPA RESPONSE: The discrepancy has been corrected
8. P19 - Here is perhaps another example of overstatement - 100% of the population has access
to waters of the rivers and lakes. What is meant here? For subsistence, this access depends
upon having transportation and gear or social relations. Do 100% of people have this in this
region?
EPA RESPONSE: The text has been revised and a table added to clarify that the topic is
access to drinking water.
9. P20 - Reword "the archaeological work is largely due to five projects."
EPA RESPONSE: The text has been revised to clarify.
10. P26 - "located along a salmon stream indicates salmon were likely a primary resource."
EPA RESPONSE: Text has been revised.
11. P31-32 - Several of these quotes focus on social changes (e.g., elimination of dog teams,
relationships to commercial fishing changing over time). People likely harvest less fish now
because they do not support dog teams, yet now they need more money for fuel and
equipment. These are important considerations for understanding contemporary mixed
economy. These points are mentioned in this cultural characterization, but perhaps could be
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made a bit more clearly. At times, even the contemporary characterization reads a bit like
"timeless" traditional cultural relationships to the land and resources, yet it is important to
accurately characterize the subsistence-based communities in their full contemporary realities
and complexities.
EPA RESPONSE: The quotes in the section focus on history and culture.
12. P34 - "Large disruptions to the population have not been documented to occur until
epidemic..."
EPA RESPONSE: Text has been revised to clarify.
13. P34/5 - Both kashgee and qasgiq are used for men's house - it is also defined three times
over these first few pages of this section.
EPA RESPONSE: The text was revised.
14. P35 - "earlier bow and arrow wards" should either be explained or omitted.
EPA RESPONSE: Reference omitted from the revised text.
15. P38, first full paragraph, last sentence - What is meant by "observe the practice?" This
general statement is not adequately supported. Authors should provide specific instances or
more discussion if this point is to be included. As written, it risks conveying a static view of
TEK and practice and culture. Many indigenous communities in Alaska, e.g., Kodiak
villages, while exploited by a colonial economic system, also strategically adapted to benefit
from those systems in ways compatible with their village lifestyles (e.g., cannery and village
co-dependencies that elder fishermen in this region remember fondly; Carothers 2010). It
would be helpful to have more information on this context in this region (e.g., Hebert 2008;
Donkersloot 2005).
EPA RESPONSE: Text omitted from the revised draft.
16. P40 - More information would be useful on Alaska Native participation in commercial
fishing in this historic period up through the present.
EPA RESPONSE: Additional reference to Alaska Native participation in commercial
fishing has been added to the assessment text.
17. P47-48 - Ellam yua and tnughit are defined twice.
EPA RESPONSE: Comment noted No change made.
18. P81-84, Table 9 - Second/third part of questions no explained. Since this is an agree/disagree
table, remove other questions for which no information is presented. All questions would
ideally be contained in an interview protocol attached as an appendix.
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EPA RESPONSE: This change has not been made. The authors chose to both identify the
interview questions and the summary responses in this table. As identified in the
introduction the semi-structured interview format was not a "survey" in which one would
ask everyone the same set of questions (as required by structured interview protocol), but
the protocol called for respondents to talk about the subject elicited by the question. This is
a very standard interview technique in anthropology.
19. P87 - 'non-monetize' - but important to note that the modern subsistence economy now
depends upon cash inputs (ATVs, boats, snow machines, gas, parts, repairs, guns, nets, etc.).
EPA RESPONSE: The relationship between the modern subsistence way of life and the
market economy has been acknowledged in the appendix and the assessment text.
20. P88 - First full sentence, last sentence poorly worded.
EPA RESPONSE: This section has been slightly reworded for clarity.
21. P89-90 - The subsistence discussion is confusing.
EPA RESPONSE: No suggestions for revisions were made.
22. P92-93, Tables - Update with recent data if possible.
EPA RESPONSE: Tables 12 and 13 contain the most recent data available to the public.
23. PI 00 - If percentage of working age population not in labor force is a better measure, it
should be included rather than official employment rates (or in addition to).
EPA RESPONSE: These data were added to the appendix.
24. PI 10 - "Villagers in the study also eat store-bought foods, but do not prefer them" - make
clear again that most residents interviewed were elders or identified culture bearers. A
concern for many subsistence villages in other regions of Alaska is the displacement of
younger generations from fish camp and other subsistence practices, and preferences for store
foods, particularly candy and soda. If this region is unique in that regard, make that clear
here.
EPA RESPONSE: The text was revised to make it clear that the interviewees expressed
preference for subsistence foods. The section on nutrition was also expanded
25. Section C "Physical and Mental Well-being" - Subsistence for emotional/mental health
should be added as a sub-section here. Given the high rates of social problems in Alaska
Native villages (e.g., suicide, violence, addiction), many cultures talk about subsistence
practices as being healing activities or producing emotion, spiritual and/or mental health.
This important aspect isn't covered in the other sub-sections.
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EPA RESPONSE: The discussion of suicide was expanded and a discussion on behavioral
and mental health was added to the "Social Relations" section. The text of the assessment
was expanded to acknowledge the social and spiritual aspects of the subsistence way of life.
26. PI 13 - Makhoul et al. is listed as 2010 in references.
EPA RESPONSE: This error was corrected.
27. PI 14 - Change Local Wild Fish and Local Practices, and "ecologically, socially, culturally,
spiritually, and possibly even evolutionarily." Point is that subsistence salmon are not just
vehicles for protein and nutrition, but form the basis of incredibly important subsistence ways
of life that are irreplaceable.
EPA RESPONSE: The revision was made and the discussion of social and spiritual values
of the subsistence way of life was expanded in the appendix and the assessment.
28. PI 15 - Add 'cultural and social disruption' to the list of risks.
EPA RESPONSE: This revision was made.
29. PI 52, 2nd and last bullet points - These are risks of mining development, not of decreased
quality/quantity of fish (defined as outside the scope of this assessment). The last bullet point
would apply to fish-effects if reworded - some community members may decide it is not safe
to eat fish, causing factions of those who express concern and those who do not. Others to
possibly include: cultural loss as younger generations do not learn the practices of
subsistence; stress on other areas and communities of the region where people may target
subsistence resources; and health risks of eating contaminated fish.
EPA RESPONSE: Comment noted These topics were discussed in the assessment text
(Chapter 12).
30. PI56 - Sing to sign.
EPA RESPONSE: Correction made.
31. Several grammatical errors throughout.
EPA RESPONSE: Every effort was made to correct grammatical errors.
COMMENTS SPECIFIC TO APPENDIX E
1. P9 - Components of total value should include indigenous homeland for Alaska Native
cultural groups.
EPA RESPONSE: The value of indigenous homeland and the value of being able to
bequest that homeland and cultural traditions onto future generations is included in the
net economic value analysis presented in Section 5. Section 5.2 discusses and attempts to
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quantify the cultural value of engaging in a subsistence livelihood, referred to as the
"activity value". Additionally, Section 5.6 discusses the importance of the existence and
bequest value of the resource, and the challenges encountered in estimating these values.
2. P12 - Clarify usage of Aleut (Alutiiq/Sugpiaq?).
EPA RESPONSE: The Bristol Bay region includes Alutiiq/Sugpiaq Alaska Natives. This
has been clarified in the text of Appendix E.
3. P22 and 26 - Change Boraas citations to Boraas and Knott.
EPA RESPONSE: This change has been incorporated.
4. P32 - Much of recreational use is non-market and could be included in the list at end of 2nd
paragraph.
EPA RESPONSE: Because we do estimate the value of recreational fishing, sport hunting,
and non-consumptive wildlife viewing, these are not identified as non-market values in this
paragraph.
5. P96 - Citation for typical crew share of 10%?
EPA RESPONSE: This estimate is based on the author's interviews with crew members.
Appendix E has been revised to make this clear.
6. P122 - Reasons for differences in earnings between local residents and others is important.
The mixed subsistence-cash economy and cultural ideas about commercial work in this
region may offer an explanation. See: Koslow 1986, Langdon 1986, Carothers 2010.
EPA RESPONSE: These references have been added to Appendix E and a brief discussion
has been incorporated in the document.
7. P134 - Ugashik, Egegik, and South Naknek have over 30.
EPA RESPONSE: Thank you for noting that these communities have over 30 permit
holders per 100 residents. We have emphasized this in the text.
8. P136, last paragraph - This paragraph seems abrupt/misplaced. A more thorough discussion
is needed here to include these points.
EPA RESPONSE: This paragraph describes information in Table 39, which appears
immediately below the paragraph. The earnings data in Table 39 is from the US Census as
well as the Alaska Commercial Fisheries Entry Commission. As earnings data is limited
and the reasons for variation in earnings are not apparent, an additional discussion was not
incorporated.
9. P178, Section 4.3 - No discussion of role of regional and village Native corporations or the
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Community Development Quota program for federally-managed fisheries.
EPA RESPONSE: Section 4.3 provides a broad overview of the economy of the Bristol Bay
Region. Although specific entities and programs like the Native corporations and
Community Development Quota program are not named, the relative importance of
government at a state, regional, and local level is considered There are many other entities
that participate in the economy and government programs that support it. This model of
the regional economy does not identify specific government entities or programs.
10. PI 91 - While the majority of formal sector jobs are taken by nonresidents, may want to note
that local economy - subsistence - is all local and highly dependent on resources of the
region.
EPA RESPONSE: We appreciate this comment, and this section of Appendix E discusses
the local and regional importance of subsistence in paragraph 3. Because this information
is covered in detail in paragraph 3, additional information was not incorporated into the
paragraph summarizing jobs captured by the market.
11. PI93 - 2009 is mentioned as an unrepresentative year and given a sensitivity ranking of
"high." More information should be included on the anomalous 2009 - in what direction
should we expect to interpret data from this year compared to more average years, or those at
other ends of the extremes?
EPA RESPONSE: The yearly variation in the commercial fishing industry is described in
detail in Chapter 3. The 2009fishing data is given a sensitivity rating of high as the data
presented in Chapter 4 estimating commercial fishing wages and jobs rely on inputs from
the 2009fishing season.
There is no reason to believe that 2009 is inherently an unrepresentative year for the
fishery, but it is impossible to know if it is a representative year for the future performance
of the fishery. In order for the wage and job estimates presented in Chapter 4 to be
representative of future performance, the 2009 data used to represent the base year would
need to also be representative offuture performance of the commercial fishery.
To clarify that this is a potential bias as the future of the commercial fishery cannot be
predicted, the text associated with this item has been rephrased
12. P195 - Number of households engaged in subsistence - ADF&G data should provide
estimates.
EPA RESPONSE: The analysis relies on data from ADF&G; however, the item listed here
identifying the potential bias of the number of households engaged in subsistence
acknowledges that the data from ADF&G is purely an estimate. Should the data relied on
from ADF&G be found to be inaccurate for some reason, this analysis that relies on those
data would be biased accordingly.
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13. PI98 - ATV, snow machines, should be added to "boats and trucks"; work by Robert Wolfe
and others (Wolfe et al. 2009) suggests that about one third of households in Alaska Native
villages harvest the majority of subsistence foods (and share, especially with the least active
households). How does this finding affect these estimates?
EPA RESPONSE: We recognize that ATVs and snow machines are frequently used in the
subsistence harvest. The original data source used to develop these expenditure estimates
did not specify expenditures for these machines, and thus they are not identified in the
quantified expenditures. In this analysis the total expenditure estimates drive the analysis,
not the composition of what these expenditures purchased Differences in the composition
of expenditures would have a negligible bias, as identified in Section 4.8.
The finding from the Wolfe 2009 citation provided above would not affect these findings.
This analysis relied on the assumption that all native households are participating in the
subsistence harvest, and estimated expenditures based on that assumption. If some native
households are more active than others, the expenditures by less active native households
will be lower than those estimated here, but this will be offset by higher expenditures by
more active native households.
14. P202 - Explain why % of adults with 4+ years of college is used in this model? The model
was not explained clearly enough for me to understand it.
EPA RESPONSE: The percentage of adults with four or more years of college education
is used in the model along with other relevant regional variables to predict adjusted gross
income per capita for each community. This instrumental variable is included in the
analysis because it is a variable that is relevant for predicting adjusted gross income per
capita in each community. For additional information on the analysis used, please see
Duffield (1997).
15. Some fisheries, e.g., crab fisheries, are not included in the economic analysis, yet depend in
part of Bristol Bay ecosystems, as discussed in Appendix F.
EPA RESPONSE: As noted in the assessment, there are other species present that support
a commercial fishery, such as the crab fishery the commenter notes. Although Appendix E
is predominately focused on the importance of the salmon fishery, some considerations for
the commercial and subsistence value of these fisheries is included
Section 4.3 of Appendix E provides an overview of the regional economy, which fish
harvesting and processing. Table 53 estimates employment in the fish harvesting and
processing sector. As identified in the footnote to Table 53, these employment estimates
include fisheries in addition to the salmon fishery.
Appendix E also acknowledges and considers that subsistence harvests may include species
other than salmon. In Section 2.2 of Appendix E the general distribution of subsistence
harvest by Bristol Bay residents is presented As identified in this section, Bristol Bay
subsistence harvest includes salmon, non-salmon fish, birds and eggs, vegetation, marine
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mammals, marine invertebrates, and land mammals. Subsistence expenditures are
estimated based on the number of native households and expenditure estimates from
Goldsmith (1998). Goldsmith's expenditures consider subsistence expenditures more
broadly, thus these other species are included in the economic analysis.
16. References - Peterson et al. 1992 and Brown and Burch 1992 not included in references.
EPA RESPONSE: Change has been incorporated.
COMMENTS SPECIFIC TO APPENDIX G
1. Mitigation measures are largely concluded to be ineffective. Would be helpful to compare
mitigation measures and their success/failure in other mining examples.
EPA RESPONSE: Appendix G contains available information about mitigation measures
generally related to roads and pipelines. Mitigation measures are not specific to mining
operations.
COMMENTS SPECIFIC TO APPENDIX H
1. P7 - Exposure of groundwater and waterfowl to chemical contaminants are listed as main
environmental concerns from tailings storage facilities. Impacts to human health from
ingesting contaminated water or birds. Clarify in report that direct risks to human health are
not accessed (only through reduction or elimination of subsistence harvests?).
EPA RESPONSE: The assessment language has been clarified to acknowledge that there
are potential direct risks to human health, but that the scope of the assessment is limited to
potential effects to indigenous cultures related to salmon. An evaluation of human health
effects from ingestion of contaminated non-salmon subsistence foods is not within the
scope of the assessment. EPA expects that a full evaluation of any future mining permit
applications and subsequent National Environmental Policy Act Environmental Impact
Statements would consider these direct effects.
CAROTHERS RESPONSE: EPA responses are sufficient [although see note under 3,
above]. Revisions were noted to Appendix D and E. Responses seem sufficient, but as
these revised appendices were not provided for review, I cannot comment on these
revisions.
EPA FINAL RESPONSE: Electronic versions of the revised appendices were available to
the reviewers, but their review was not required as part of the follow-on review process.
Dennis D. Dauble, Ph.D.
1. Appendix B, Page 30: Table 1.1 suggest adding a column to indicate relative abundance, for
example, if individual fish species listed are abundant, common or rare. Also, are there
known differences in distribution and abundance for the Nushagak and Kvichak watersheds
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relative to those watersheds unlikely to be affected by mining activities?
EPA RESPONSE: This information, when known, has been added to Appendix B.
DAUBLE RESPONSE: More important, Table 5.1 includes a list of anadromous and
resident fish species reported in the Nushagak and Kvichak River watersheds and their
relative abundances.
EPA FINAL RESPONSE: No response required.
2. Appendix A, Page 42: The statement that diminished salmon runs present a "negative
feedback loop" where spawner abundance declines, appears to conflict with the last
paragraph on page 41.
EPA RESPONSE: The text describes bottom-up effects of marine-derived nutrients (MDN)
on stream ecosystems and points out that these linkages have not been empirically
established. The negative feedback loop mentioned in the following paragraph could result
from reductions in salmon-based resources that promote either bottom-up (i.e., a reduction
in salmon-derivedNandP) or direct (i.e., a reduction in salmon eggs andflesh that can be
consumed by fish) benefits to juvenile fishes. Further, the fact that bottom-up effects of
MDN have not been firmly established does not negate considerable circumstantial
evidence for bottom-up nutritional deficits in Columbia Basin spawning streams. Edits
have been made to help clarify.
DAUBLE RESPONSE: You present a convoluted argument. I could not find specific
edits but recognize the topic is more complicated than some might imagine. As long as it
is acknowledged somewhere that MDN is more important in systems that would
otherwise be nutrient-deficient and that this input may be more important in lentic
systems than lotic systems, I'm happy.
EPA FINAL RESPONSE: Edited text on this topic is now provided in Appendix A (pages
45-47). Additional text has also been added to Chapters 5 and 7 explaining the spatial
variability in the relative importance of MDN.
3. Appendix F, Page 3: Is there significant sediment transport from the Bristol Bay watershed to
the Nushagak and Togiak Bays/estuaries?
EPA RESPONSE: A new section was added to Appendix F that discusses the importance
of estuary habitat to salmon populations.
DAUBLE RESPONSE: The response did not address my question. Also, note that the
peer review panel did not receive copies of revised Appendices. I did, however, find a
reference in the main document about potential for sediments to be transported to
estuarine habitats.
EPA FINAL RESPONSE: Electronic versions of the revised appendices were available to
the reviewers, but their review was not required as part of the follow-on review process.
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The potential for transport of sediments to estuarine habitats is mentioned in the
assessment, but a thorough evaluation of the issue is beyond the scope of the assessment.
4. Appendix F, Page 7: What is the juvenile salmon resident time in Bristol Bay? How quickly
(and at what size/time of year) do they move from shallow nearshore to offshore habitats?
EPA RESPONSE: A new section was added to Appendix F that discusses the importance
of estuary habitat to salmon populations.
DAUBLE RESPONSE: Hopefully, this new section addresses my question.
EPA FINAL RESPONSE: No response required.
5. Page 8-15 (L2): Suggest deleting "likely." There will be impacts.
EPA RESPONSE: We believe this language is consistent with the uncertainties explained
in the assessment. No change has been made.
DAUBLE RESPONSE: No comment.
EPA FINAL RESPONSE: No response required.
Gordon H. Reeves, Ph.D.
1. Page 6-9 (PI): Why would resident fish not "suffer" immediate loss of habitat as a result of
dam failure like anadromous fish would?
EPA RESPONSE: This statement refers to fish located upstream of TSFfailure and
affected downstream reaches. This has been clarified in the text.
2. Couldn't fish move to another stream if a culvert is blocked and prevents upstream
movement? This may eliminate the fish from a particular stream for a year but it might not
reduce the overall productivity.
EPA RESPONSE: Elimination of access to a particular stream would of course reduce
local productivity. Whether or not it reduced productivity at some larger scale would
depend on how spawning and rearing habitat limit productivity at that larger scale, and the
relative contribution of the blocked stream to the larger population. These aspects are
generally unknown for the study area streams.
Charles W. Slaughter, Ph.D.
1. Global: Provision of full color versions of all figures would have been helpful to this review.
The selected color versions supplied here were useful - we should have had them all.
EPA RESPONSE: Comment noted.
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SLAUGHTER RESPONSE: The many figures and maps provided are greatly helpful.
EPA FINAL RESPONSE: No response required.
2. Page 2-4: Color codes are confusing - use of different colors for same "moisture state" in the
five regions doesn't make sense (to me).
EPA RESPONSE: Figure 2-2 (Figure 3-1 in the revised assessment) depicts hydrologic
landscapes across the Nushagak and Kvichak watersheds separated into their
physiographic divisions as defined by Wahrhaftig (1965), combined with their climate class
as defined by Feddema (2005). Each color group (e.g., yellow, green, red, etc) represents a
separate physiographic division while color intensity (e.g., light green to dark green)
represents the climate class within a given physiographic division. The use of different
colors is intended to show the variety of climate classes within a given physiographic
division, while also depicting similarities in climate class across different physiographic
divisions (e.g., darkest red and darkest green show that two areas having different
physiographic characteristics are alike in their climate class).
SLAUGHTER RESPONSE: The new figures and maps are very well thought out and
presented, throughout the revised Assessment.
EPA FINAL RESPONSE: No response required.
3. Page 3-4 (S3.4, LI): ...when mine is active
EPA RESPONSE: Correct (now in Section 4.2.4).
SLAUGHTER RESPONSE: OK.
EPA FINAL RESPONSE: No response required
4. Page 4-5 (last P): Refers to Fig. 3-1, but "existing road segments" listed are not shown on
Fig. 3-1, nor are several cited locales: Williams Port, Pile Bay, King Salmon, and Naknek.
EPA RESPONSE: This reference has been deleted.
SLAUGHTER RESPONSE: OK.
EPA FINAL RESPONSE: No response required.
5. Page 4-11 (first P): "The vast majority of tailings dams are less than 30 m in height..."
DOES THIS REFER TO TAILINGS DAMS AT ALL KNOWN MINING OPERATIONS,
OR TAILINGS DAMS ENVISIONED OR PROBABLY TO BE USED IN BRISTOL BAY
WATERSHED?
EPA RESPONSE: The sentence refers to all known mining operations. The text was
changed from "The vast majority of tailings dams..." to "The majority of existing tailings
dams..." (Chapter 4).
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SLAUGHTER RESPONSE: OK.
EPA FINAL RESPONSE: No response required.
6. Page 4-11 (first P): "Although upstream construction is considered unsuitable for
impoundments intended to be very high or to contain large volumes of water or solids... .this
method is still routinely employed." ARE THE TSFs SUGGESTED IN THIS
ASSESSMENT CONSIDERED "UPSTREAM," "DOWNSTREAM," OR
"CENTERLINE"? Para. 1, Section 4.3.5 (p. 4-21), states that "the most plausible sites" for
TSFs are "the higher mountain," which suggests that these TSFs would be "upstream"
facilities, therefore "considered unsuitable..."
EPA RESPONSE: The TSFs suggested in the scenarios would be constructed using the
downstream method and then switched to a centerline method. It is true that in this
location, the upstream construction would be unsuitable. The discussion of the upstream
method was intended for background and has been moved to Chapter 4 in the revision,
with the scenario-specific suggestions discussed in Chapter 6.
SLAUGHTER RESPONSE: The revisions in Chapter 4 and Chapter 6 are helpful in
clarifying this.
EPA FINAL RESPONSE: No response required.
7. Page 4-23 (P2): Text suggests that a monitoring well field downslope from the TSF (and
presumably from all hypothetical TSFs) would detect seepage; such seepage would then be
intercepted and either returned to the TSF or "treated and released to the stream channel."
Either action presupposes adequacy of monitoring seepage and subsurface flow (both
spatially and temporally); returning such water to the stream further presupposes fully
adequate treatment to meet both regulatory and aquatic biota requirements for water quality
and flow regime.
EPA RESPONSE: Yes, the well fields would be downstream from all embankments for all
TSFs and this has been clarified in the revision. It is assumed for the scenarios that
mitigation measures are operated appropriately. Text has been clarified in the new Chapter
6 to indicate that water would be treated to meet permit requirements. Scenarios in the
revised assessment evaluate effects from uncaptured seepage during routine operations
from both the TSFs and waste rock piles.
SLAUGHTER RESPONSE: The text acknowledges that well fields would not expect to
either detect or capture all seepage waters. Recognition of effects of uncaptured seepage
is appropriate. There remain (possibly unavoidable) generalized and optimistic
statements, such as "If contaminated groundwater was detected, monitoring wells
would be converted to collection wells or new recovery wells would be installed and
water from the well field would be pumped back into the TSF or treated and released to
stream channels." (p.6-12), or "...excess captured water would be treated to meet
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existing water quality standards and discharged to nearby streams, partially mitigating
flow lost from eliminated or blocked upstream reaches." (p. 6-15-6-16).
EPA FINAL RESPONSE: No response required.
8. P4-26 to 4-28 (S4.3.7): This "Water Management" section seems cursory, highly generalized,
and optimistic. Statements such as "uncontrolled runoff would be eliminated"; "water from
these upstream reaches would be diverted around and downstream of the mine where
practicable"; and "Precipitation... would be collected and stored...." do not indicate actual
(proposed) practices or techniques, nor inspire confidence that actual runoff events during
"normal" conditions, let alone during hydrologic extremes (such as a rain-on-snow event
with underlying soils still frozen) would be planned for or actually managed adequately.
EPA RESPONSE: Water management measures are more clearly described and discussed
in the revision (Section 6.1.2.5), and in sub-sections for the mine components in the
scenarios. Measures are standard and common to existing mine sites.
Collection and diversion structures would need to be designed and built to handle the
anticipated flows over the life of the mine, including during extreme weather events. The
details of these collection and conveyance systems are beyond the scope of this assessment
and are more properly in the domain of the permitting process when a specific mine plan is
proposed.
SLAUGHTER RESPONSE: The revised Assessment devotes much more attention to
hydrology and water management. The many analyses, figures and tables provide a
great deal of useful information, and undoubtedly would be utilized by PLP engineers if
they proceed to permit application and final design. The calculations and figures of
Section 7.3 seem quite reasonable, as are the findings of Sections 7.3.2, the statement of
uncertainties (Section 7.3.1.5), and the summary (Section 7.4).
EPA FINAL RESPONSE: No response required.
9. P4-29 (PI): Suggests that 20% more water than available would be required "during startup,"
and that difference would be satisfied "from water stored in the TSF"; if 20% more than is
available would be needed, where would it come from to be available from the TSF?
EPA RESPONSE: The water balance has been revised in Chapter 6. The mine operation
would capture more water than needed during all phases of operation. Water could be
stored in the TSF as soon as the starter embankment is operational. Ghaffari et al. (2011)
further explain: "Once the TSF starter embankment construction is complete, site water
will be diverted into this facility to ensure adequate make-up water for process plant start-
up. At this time, advanced open pit dewatering will commence. This water will either be
treated and discharged or diverted to the TSF, depending on environmental requirements."
SLAUGHTER RESPONSE: The revision is appropriate. Given the sensitivity of
salmonids and aquatic invertebrates to seemingly-minor or low-level perturbations of
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water quality and timing, the statement from Ghaffari et al (2011) that "This water will
either be treated and discharged or diverted to the TSF, depending on environmental
requirements" is not particularly reassuring.
EPA FINAL RESPONSE: No response required.
10. Page 4-29 (P3): Assumptions are very generalized and optimistic: "assuming no water
collection and treatment failures" and "excess captured water would be treated... and
discharged to nearby streams..." - this assumes both "no failures" over the life of the
operation, and that such treated "excess captured water" could be successfully treated before
release to fully meet both regulatory water quality criteria and the possibly more sensitive
biological requirements of individual invertebrates and fish stocks (Appendices A & B).
EPA RESPONSE: Water management measures are more clearly described and discussed
in the revision in Section 6.1.2.5, and in sub-sections for the mine components in the
scenarios. Measures are standard and common to existing mine sites. The revised
assessment considers water treatment failure quantitatively and includes refined scenarios
with new data for seepage from TSFs and waste rock piles.
SLAUGHTER RESPONSE: The revisions are appropriate. The revised Assessment
devotes much more attention to hydrology and water management. The many analyses,
figures and tables provide a great deal of useful information.
EPA FINAL RESPONSE: No response required.
11. Section 4.3.8: This and the previous section mention (but in my view, do not adequately
stress) the extremely long time frame for post-mining active management and oversight.
Many hundreds of years of active management is a longer time than many industrial,
corporate or governmental entities are capable of really embracing - witness the current US
Congressional practice of "kicking the can down the road" - a human trait.
EPA RESPONSE: This issue is addressed in Section 4.2.4 of the revised assessment.
SLAUGHTER RESPONSE: I have noted that the long time frame, and the potential
frailty of human institutions over that time frame, is now acknowledged in several
places in the revised Assessment.
EPA FINAL RESPONSE: No response required.
12. Page 4-32 (S4.3.8.2, P3): Suggests that pyritic tailings could be "shipped off site" - i.e., to
where? Deep ocean dumping, or Yucca Mountain?
EPA RESPONSE: For smaller amounts of tailings, the option of shipping them to an off-
site location for disposal might be an option; however, this is less likely with large mines
with high volumes of tailings, so has been removed in the revised assessment.
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SLAUGHTER RESPONSE: OK.
EPA FINAL RESPONSE: No response required.
13. Page 4-34 to 4-37 (S4.3.9): This reviewer finds the short Transportation Corridor sub-chapter
to be succinct, but inadequate and superficial in view of the long-term consequences of
imposition of the transportation corridor as portrayed. These deficiencies are addressed, in
part, in other sectors of the Assessment, most comprehensively in Appendix G.
EPA RESPONSE: The transportation corridor analysis has been substantially expanded,
and is now found in its own chapter (Chapter 10).
SLAUGHTER RESPONSE: This revision and upgrading to Chapter status is quite
appropriate. The more detailed considerations found in Chapter 10 more accurately
reflect the concerns of this (and other) reviewers about the potential transportation
corridor.
EPA FINAL RESPONSE: No response required.
14. Page 4-38 (Box 4-3, P2): Para. 2 states that the southwest extension of the Lake Clark Fault
is currently understood to extend to perhaps 16 +/- km from the Pebble ore deposit; however,
this is not reflected in Figure 4-11, which suggests that the Lake Clark Fault terminates
perhaps 100 km northeast of the Pebble locale. Elsewhere in Box 4.3, there is
acknowledgement that, while there is no evidence of recent tectonic activity in the immediate
Pebble vicinity, there is relatively little site-specific data or long-term historical seismic
record. I infer that any predictions concerning seismicity or earthquake occurrence of any
magnitude would have very high uncertainty.
EPA RESPONSE: Figure 4-11 (now Figure 3-15) has been revised to more accurately
illustrate the current understanding of the terminus of the Lake Clark Fault. Section 3.6
describes the uncertainties in predicting seismicity in the Pebble region.
SLAUGHTER RESPONSE: OK. The discussion of Section 3.6 is appropriate and is
appreciated.
EPA FINAL RESPONSE: No response required.
15. Page 4-41 (Box 4-4): Note that in each of the four tailing dam failure examples, the failed
structure was roughly an order of magnitude smaller (in height) than the hypothetical TSF-1
structure, yet those failures had major negative consequences.
EPA RESPONSE: Text was added to Section 9.1.1 in the revised assessment to indicate
that the dams in these failure examples were significantly smaller than the dams proposed
in our mine scenarios.
SLAUGHTER RESPONSE: The revision was noted.
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EPA FINAL RESPONSE: No response required.
16. Page 4-45 to 4-47 (S4.4.2.2): The probability approach to tailing dam failure is unpersuasive
as presented. It is difficult to relate to a number like "0.00050 failures per dam year," or to
the implication (p. 4-47) that one can expect a tailings dam failure only once in 10,000 to one
million "dam years." This could suggest to the casual reader that failure of the hypothesized
TSF1 dam (for which one "dam year" is one year) should not be anticipated in either the time
of human occupation of North America, or the span of human evolution.
EPA RESPONSE: The proposed dams, if designed, built, and maintained to current
engineering best practices, would be anticipated to have a low annual probability offailure
but the failure probability would not be zero. We concur with the commenter that these low
probability numbers may be difficult for the casual reader to grasp, so we also present the
estimates ofprobability in terms ofprobability failure over different time periods. For
example, an annual probability offailure of0.0005 equates to a 5% probability offailure
over 100years and a 39% probability of failure over 1000years. Text was also added to
clarify the basis for our failure rates.
SLAUGHTER RESPONSE: The clarification of probability analysis for TSF failure,
provided in the main body of the assessment, is appreciated. However, I still question
the message sent, both in the Executive Summary and in the larger report, that a TSF
failure has a "recurrence frequency of 2500 to 250,000 years." This might imply to a
reader that with 2500 years as the shorter time span stated, no one should worry about
a possible TSF failure, despite the report's documentation of actual failure incidents
elsewhere. I suggest eliminating reference to "recurrence interval" in this discussion.
EPA FINAL RESPONSE: Box 9-3 has been added to the final assessment to address
issues associated with understanding probabilities and frequencies of tailings dam failures.
17. Page 4-48 (Box 4-6): Box 4-6 suggests that the Operating Basis Earthquake (OBE) for a 7.5-
magnitude event at the Pebble locale has an estimated return period of 200 years. Such a
return interval probability is difficult interpret, given the lack of historical seismic record for
the region; in any event, such a return period estimate is in no way predictive of future
seismic activity, in year 2012 or year 2212.
Box 4-6 does note that "The return periods stated in Alaska dam safety guidance are
inconsistent with the expected conditions for a large porphyry copper mine developed in the
Bristol Bay watersheds, and represent a minimal margin of safety.
EPA RESPONSE: The return periods used are consistent with the Alaska Dam Safety
Guidance, but the operator could include an additional margin of safety in the design for
critical structures. The return period and seismic safety factors do not inform the failure
analysis in this assessment.
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SLAUGHTER RESPONSE: The discussion in the revised Assessment Section 3.6, along
with Table 3.5 and Figure 3.15, is quite helpful. It clarifies known seismic history and
acknowledges the "high degree of uncertainty" on this topic for the Bristol Bay
watershed.
EPA FINAL RESPONSE: No response required.
18. Page 4-50 to 4-60 (S4.4.2.4): The modeled hydrologic consequences of overtopping/flooding
of the hypothetical TSF1 dam/reservoir seem reasonable, given the relatively limited
hydrologic data set available for model input. Probable Maximum Precipitation and Probable
Maximum Flood results should be approximately "correct" and within the same order of
magnitude of potential storm and flood events. The potential consequences outlined (peak
flow volume, sediment transport and deposition, length of stream corridor impacted) appear
realistic for the scenario. I suggest that this topic and hypothetical result should be given
more visibility and emphasis in the assessment.
EPA RESPONSE: The dam failure was modeled as an overtopping event since the
possibility could exist. However, the magnitude of the PMP run-off as compared to the
resulting failure flood wave is very small. We agree that an actual dam design will consider
additional information, but this assessment did not investigate the hydrology of the PMF in
greater detail.
SLAUGHTER RESPONSE: As initially noted, the hydrologic sectors of the revised
Assessment, including this discussion of PMP and PMF in relation to volumes which
would be released by a TSF dam failure, are reasonable.
EPA FINAL RESPONSE: No response required; however, in the final assessment,
flooding to generate overtopping is no longer simulated.
19. Page 4-62 to 4-63 (S4.4.4): While accurate, this section does not adequately address the
road/stream crossing/culvert issue. Given the projected transportation corridor, Pebble locale
to Cook Inlet, and the inevitability of a further network of "minor" roads in the mine and TSF
locale, plus additional infrastructure linkages, road/culvert/stream crossings are a major
concern for aquatic habitat and fisheries. This issue receives more attention in Sections 5.4
and 6.4, and is mentioned elsewhere in Volume 1 (e.g., Table 8.1, Box 8-1, para. 8.1.2.4.).
Readers of the Assessment should be directed to Frissell and Shaftel's Appendix G for a
more comprehensive discussion of this important topic.
EPA RESPONSE: This issue is now analyzed in more detail in its own chapter (Chapter
10). The appendix is cited.
SLAUGHTER RESPONSE: I fully agree with the decision to highlight the
transportation corridor with a stand-alone chapter. The importance is readily
indicated, simply by reference the Figures 10.2,10.5, and 10.6; this importance fully
justifies the more comprehensive treatment of transportation corridor issues provided
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in Chapter 10. Inclusion of issues such as dust control and invasive species is
appropriate.
EPA FINAL RESPONSE: No response required.
20. Chapter 5: Assumes scenario of "no failure" for entire project, over complete project life. Is
this a realistic scenario, given experience with industrial developments in real-world settings
subject to vagaries of equipment, landscape, geology, weather, local climate, and human
judgment and decision making/execution?
EPA RESPONSE: The "no failure" scenario has been eliminated in response to several
comments, and is now considered in terms of mine footprint impacts in Chapter 7.
SLAUGHTER RESPONSE: OK.
EPA FINAL RESPONSE: No response required.
21. Page 5-1 (S5.1.1): Question: is "sampling extensively for summer fish distribution over
several years" adequate for characterizing fish populations, given the wide fluctuations in
salmon escapement and return note elsewhere in the Assessment (e.g., Table 5-1, para.
5.1.2)?
EPA RESPONSE: The answer to this question is of course dependent upon the objectives
of the characterization. For the purposes of this section of the assessment, identifying
species distributions within the study area, sampling was adequate for minimally
characterizing the distribution of salmon, Dolly Varden, and rainbow trout within the
project area, including known spawning areas.
SLAUGHTER RESPONSE: Can't disagree, since you qualify this as "minimally
characterizing distribution".
EPA FINAL RESPONSE: No response required.
22. Page 5-12 to 5-48 (S5.2): Estimates of habitat, wetland and stream blockage or loss seem
reasonable, but, as noted in the text, are probably conservative or "at the low end."
EPA RESPONSE: Agreed. No change suggested or required.
SLAUGHTER RESPONSE: OK.
EPA FINAL RESPONSE: No response required.
Estimates of probable streamflow diminution (p. 5-25) seem reasonable, but make no
reference to seasonality.
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EPA RESPONSE: We assume a constant seasonal demand, thus streamflow changes
follow baseline seasonal patterns under this analysis. We clarify that water managers may
alter holding and release of water to address environmental flow needs.
SLAUGHTER RESPONSE: The text, tables and figures of Section 7.3 demonstrate the
author's cognizance of seasonality of streamflow. The analysis seems thorough. I note
that (as in the earlier draft), projected streamflows do not meet the 20% sustainability
boundary for flow alterations (as in Figure 7-19).
EPA FINAL RESPONSE: No response required.
23. Page 5-29 to 5-30 (thermal regimes): This section makes no mention of aufeis or "nalyds,"
ice accumulations which can exert major control on spring and early summer habitat
availability and thermal conditions. For examples, see Slaughter (1990), among many other
references.
EPA RESPONSE: Citation and text have been added in Section 7.3.2.
SLAUGHTER RESPONSE: Aufeis is not only a concern for culvert blockage, through
that is a major concern for roads and highways - see Figures 1, 3 and 4 in Ashton and
Griffiths (1990). Aufeis can be widespread in natural channels and floodplains (see
Figures 1, 3, 6,10 and 11 in Slaughter (1990)), and may be induced by seemingly-minor
modification of natural water flow during winter conditions.
EPA FINAL RESPONSE: Agreed. Section 7.3.2.4 discusses the importance of
maintaining ice-free conditions for overwintering fish and the role of groundwater.
24. Page 5-30 to 5-31: Concur that maintenance of natural flow regime is the desirable target; the
"sustainability boundary" approach is a way to attempt managing within the "natural" bounds
of variability. Note: Figure 5-9 is map of streams and wetlands lost, not predicted flow
alteration hydrograph (see last sentence, p. 5-31).
EPA RESPONSE: Figure references have been updated.
SLAUGHTER RESPONSE: OK.
EPA FINAL RESPONSE: No response required.
25. Page 5-37 (Figure 5-10): UT100D - predicted flow is ALWAYS below lower 20%
sustainability boundary. UT100C, UT100C1, UTC100B -predicted flows are always within
the 20% +/- sustainability boundaries.
EPA RESPONSE: Figure has been revised, and data now presented in Table 8-1.
SLAUGHTER RESPONSE: Table 8-1 does not provide indication of predicted flows in
relation to 20% sustainability boundaries. Figures 7-15, 7-16 and 7-17 do depict
potential flow alterations which would exceed the 10% and 20% sustainability
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boundaries; these flow alterations are also noted; however, exceedances of sustainability
boundaries not highlighted in the last column of Tables 7-16, 7-17, and 7-18.
EPA FINAL RESPONSE: The figure has been revised and data are now provided in Table
7-19.
26. Page 5-38 (Figure 5-11): Predicted flow for two upper gages (SK100G, SK100F) is always
below the 20% sustainability boundary. Predicted flow at other gages appears to be near or
within the 10% and 20% lower sustainability boundary.
EPA RESPONSE: Figure has been revised, and data now presented in Table 8-2.
SLAUGHTER RESPONSE: See preceding comment.
EPA FINAL RESPONSE: See response to preceding comment.
27. Page 5-39 (Figure 5-12): Predicted high flow for NK119A is far below the lower 20%
sustainability boundary throughout the open water season. From onset of snowmelt, flow at
other gages is roughly at or within the lower 20% sustainability boundary.
EPA RESPONSE: Figure has been revised, and data now presented in Table 8-3.
SLAUGHTER RESPONSE: See preceding comment.
EPA FINAL RESPONSE: See response to preceding comment.
28. Page 5-41: Gage NK119A - is the estimated decrease of streamflow (minimum mine size)
63% (Table 5-13) or 73% (text)?
EPA RESPONSE: Values have been updated.
SLAUGHTER RESPONSE: OK.
EPA FINAL RESPONSE: No response required.
29. Page 5-41: In any case, text is clear: predicted flow reductions for North and South Forks
Koktuli River are materially below the lower 20% sustainability boundary. Text suggests that
while upper Talarik Creek would be essentially obliterated in this hypothetical scenario,
lower gaging stations on Talarik Creek might have partial augmentation of reduced flows,
from small tributary flows and groundwater; without supporting data, this suggestion seems
unsupportable.
EPA RESPONSE: Revised text illustrates important trans-watershed groundwater
contributions to lower Upper Talarik Creek.
SLAUGHTER RESPONSE: OK - but the trans-watershed groundwater contributions
are still hypothetical.
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EPA FINAL RESPONSE: Observations by contractors for the Pebble Limited Partnership
provide support for transfer of groundwater from the South Fork Koktuli River to the
tributary of Upper Talarik Creek at UT119A, and we cite PLP (2011: Chapter 7) in the
final assessment. This assumption is incorporated into our streamflow analyses.
30. Page 5-42 to 5-45: These pages fairly summarize the potential for substantive alterations to
streamflow regime and surface water/groundwater relationships.
EPA RESPONSE: No change suggested or required.
SLAUGHTER RESPONSE: OK.
EPA FINAL RESPONSE: No response required.
31. Page 5-44 (P3): "Once the mine is no longer a net consumer of water, we assume that flow
regulation through the water treatment facility could be designed to somewhat approximate
natural hydrologic regimes, which could provide appropriate timing and duration of
connectivity with off-channel habitats." I suggest that this is a highly optimistic assumption,
and does not address water quality questions (which are raised elsewhere in the Assessment).
EPA RESPONSE: We emphasize that the ability to manage flows will be dependent upon
sufficient infrastructure and flexibility in water management.
SLAUGHTER RESPONSE: OK - I'm not sure that you could do much more, since this
is all potential and hypothetical, and remains an optimistic assumption of future
"sufficient infrastructure and flexibility in water management."
EPA FINAL RESPONSE: No response required.
32. Page 5-45 (S5.2.3): This entire paragraph should receive greater emphasis.
EPA RESPONSE: This section (now Section 7.3.3) has been expanded.
SLAUGHTER RESPONSE: The risk characterization (Section 7.3.3), while brief, is
written well and provides the recommended emphasis.
EPA FINAL RESPONSE: No response required.
33. Page 5-46 (P4): Ignores variable-source-area concepts, which are widely accepted in
hydrologic and watershed analysis.
EPA RESPONSE: We respectfully disagree. The variable source area concept presents the
idea about the expansion and contraction of saturated areas that are the immediate source
of streamflow during storms. In does not invalidate the notion that the total drainage area
contributes with longflowpaths to streams. These longflowpaths ultimately contribute to
saturated zones that support perennial streaniflows.
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SLAUGHTER RESPONSE: Of course the total drainage area may contribute to
streamflow; the contributing area may shrink and expand depending on incoming
precipitation (or meltout of seasonal snowpack). Your "long flowpaths" may expand or
contract seasonally; I fail to see any argument here.
EPA FINAL RESPONSE: This text does not appear in the final assessment.
34. Page 5-46 (P5): Assumes requirement for more water than is available, but leaves hanging
the question of where that more water might be sourced. Given that the site is a watershed
headwaters, what might be tapped as additional water supply, and what might be the impacts
on that source(s)?
EPA RESPONSE: The revised water balance indicates that the mine would have the
capability to capture more water than it needs during all operational phases, including
start-up, from within the mine footprint.
SLAUGHTER RESPONSE: If we accept the revised water balance, then you would not
be looking for additional water supply.
EPA FINAL RESPONSE: This is correct; no change required
35. Page 5-59 to 5-63 (S5.4): See earlier cautions concerning stream crossings, culverts. Note
that road cuts and culverts are particularly susceptible to development of aufeis ("icings"),
often resulting from blockage or alteration of subsurface water movement during cold
conditions, as witnessed by long-standing AKODT maintenance issues - Richardson, Steese,
Dalton highways, for example.
EPA RESPONSE: The potential for culvert blockage by aufeis is discussed in Chapter 10
of the revised assessment.
SLAUGHTER RESPONSE: Aufeis is not only a concern for culvert blockage, though
that is a major concern for roads and highways - see Figures 1, 3 and 4 in Ashton and
Griffiths (1990). Aufeis can be widespread in natural channels and floodplains (see
Figures 1, 3,6,10 and 11 in Slaughter (1990)), and may be induced by seemingly-minor
modification of natural water flow during winter conditions.
EPA FINAL RESPONSE: Agreed. Section 7.3.2 discusses the importance of maintaining
ice-free conditions for overwintering fish, and the role of groundwater.
36. Page 5-60 (S5.4.2, PI): The statement that"... it is unlikely that a mine access road would
have sufficient traffic to significantly contaminate runoff with metals or oil" is unsupported;
it might be instructive to look at traffic loads for the access road from the Steese Highway to
the Ft. Knox mine, a much smaller operation than the proposed Pebble development.
EPA RESPONSE: This statement no longer occurs in the assessment.
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SLAUGHTER RESPONSE: OK.
EPA FINAL RESPONSE: No response required.
37. Page 5-60 (S5.4.2, P2): First sentence is correct. Second sentence is unsupported and
probably incorrect (see Appendix G). Yes, runoff from roads is location-specific; that does
not mean that runoff from roads would be insignificant to salmonids, given the very large
number of streams (perennial, intermittent, and ephemeral), and wetlands, which would be
intersected by the total road system of the Pebble project. This also seems to be contradicted
by Section 5.4.3.
EPA RESPONSE: This issue is now given more attention in Chapter 10.
SLAUGHTER RESPONSE: Again, I concur with the decision to address the
transportation corridor more comprehensively in a free-standing chapter.
EPA FINAL RESPONSE: No response required.
38. Page 5-60 (S5.4.4.1): There are many more water or seep crossings than 34 - see USGS
topog sheets, ACME Mapper, or Google Earth.
EPA RESPONSE: The number of crossings has been updated in the revised assessment.
SLAUGHTER RESPONSE: OK.
EPA FINAL RESPONSE: No response required.
39. Page 5-61 (S5.4.4.2 and 5.4.4.3): Development of aufeis ("icings") consequent to partial or
full culvert blockage, or induced by soil mantle compaction (i.e., by roads or off-road vehicle
traffic) can partially or wholly block stream channels. Such blockage, in association with ice
on the streambed, may last long past snowmelt and persist well into early summer, possibly
affecting fish movement.
EPA RESPONSE: The potential impact of aufeis on stream channels and potential
existence past breakup is discussed in Chapter 10 of the revised assessment.
SLAUGHTER RESPONSE: I can only assume (hope?) that conditions in the Bristol
Bay watershed may be less conducive to aufeis or nalyd ("icings") formation than in
interior and northern Alaska. Aufeis is not only a concern for culvert blockage, though
that is a major concern for roads and highways - see Figures 1, 3 and 4 in Ashton and
Griffiths (1990). Aufeis can be widespread in natural channels and floodplains (see
Figures 1, 3,6,10 and 11 in Slaughter (1990)), and may be induced by seemingly-minor
modifications of natural water flow during winter conditions.
EPA FINAL RESPONSE: Agreed. Section 7.3.2.4 discusses the importance of
maintaining ice-free conditions for overwintering fish and the role of groundwater.
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40. Page 5-62 (S5.4.5): While I don't have the specific citations at hand, there are published
analyses of dust effects associated with the North Slope haul road and Prudhoe Bay road
network. Obvious effects include accelerated snowmelt along the road corridor, and nutrient
or pollutant contributions to road corridor environs.
EPA RESPONSE: The revised assessment includes information from published literature
on dust effects in the Arctic (Chapter 10).
SLAUGHTER RESPONSE: The added information in Chapter 10 is appropriate.
EPA FINAL RESPONSE: No response required.
41. Page 5-63 (S5.4.6.3): Should it read ".. .impacting 270.3 km of stream..."? (Incidentally, it
is interesting that this coarse assessment finds it possible to state impact to within 100-meter
resolution.)
EPA RESPONSE: The revised assessment notes that risks to salmonids from de-icing salts
and dust suppressants could be locally significant, but we cannot state that the entire
stream length between potential road crossings and Iliamna Lake would be affected.
SLAUGHTER RESPONSE: OK.
EPA FINAL RESPONSE: No response required.
42. Page 5-65 (S5.4.7.3 and 5.4.8.3): Viewing the transportation corridor landscape, via maps,
Google Earth or ACME Mapper, gives me the impression that the estimate of 4.9 km2
wetlands directly impacted is a very low number. It is easy to play with the numbers given
on pp. 5-69 - 5-70, regardless of their accuracy; 66 km of road impacting wetlands, assuming
a 10-meter roadway footprint, yields 0.66 km2 of wetlands "under the road" (vs. 0.18 km2 in
the text). The 200-meter proximity to wetlands cited, over 66 km of road, yields some 13
km2 of wetland impact (vs. 7.3 km2 in the text). 80 km of road within 200 m of streams or
wetlands yields 16 km2 of road/wetland impact. Since these are all assumptions and
estimates, it is not possible to conclude that any of these figures would be the "true" area
impacted.
EPA RESPONSE: The 0.18 km2 refers to the area of wetlands which would be filled by the
roadbed "intersecting" wetlands (19.4 km length of roadbed x 9.1 m width of roadbed), and
does not include roadbed adjacent to wetlands (note that this area is 0.11 km2 in the revised
assessment due to a slight change in methodology for measuring road length). The 4.9 km2
(not 7.3 km?) area of wetland within 200 m of the length of road (on both sides) within the
study area is based on actual National Wetlands Inventory (NWI) data (the calculation
methodology is described in Box 10-1 of the revised assessment).
Though NWI data were utilized in this analysis, the 200 m road buffer was derived from a
literature estimate of the road-effect zone for secondary roads.
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SLAUGHTER RESPONSE: OK. Since these are all assumptions and estimates
(including the NWI data), it is not possible to conclude that any of these figures would
be the "true" area impacted.
EPA FINAL RESPONSE: No response required.
43. Page 5-74 (S5.4.10): Should this say impact rather than "risk"?
EPA RESPONSE: "Impact" could be used here, but we chose to use "risk" to note the
probability rather than certainty that salmon would be affected by the corridor-associated
activities/events listed
SLAUGHTER RESPONSE: OK.
EPA FINAL RESPONSE: No response required.
Text implies that even this "no-failure" scenario will impact salmonids; however, it is
apparently not possible to estimate specific changes or the magnitude of such changes.
EPA RESPONSE: The no-failure scenario has been eliminated in response to several
comments; effects resulting from the mine footprint are now discussed in Chapter 7. The
exact magnitudes of changes in fish productivity, abundance and diversity cannot be
estimated at this time, but the species, abundances, and distributions that would potentially
be affected are summarized in Chapter 10 of the revised Assessment.
SLAUGHTER RESPONSE: OK - as noted before, Chapter 10 is a valuable addition to
the Assessment.
EPA FINAL RESPONSE: No response required.
44. Page 5-74 to 5-77 (S5.6): This section seems cursory and understated, particularly in view of
the extensive discussion of Appendix D.
EPA RESPONSE: The discussion of fish-mediated effects on Alaska Native culture has
been expanded and is now in Chapter 12.
SLAUGHTER RESPONSE: The expanded discussion in Chapter 12 is appreciated.
EPA FINAL RESPONSE: No response required.
45. Section 6.1: Concur with general overview statements, and with conclusions regarding
immediate consequences of TSF dam failure, which would likely be as severe as or more
severe than stated in 6.1.2.1.
P. 6-6, first sentence - note that the failure scenario predicts over 70% fines <0,1 mm, vs. the
6% "natural" fines concentrations.
P. 6-13, last para. - the assumption that overtopping would not occur in winter is not
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warranted, as the authors admit when citing the Nixon Fork Mine incident. In the Bristol Bay
environment, a major rain-on-snow event in winter or spring is within the realm of
possibility, and of course human error is, if not inevitable, always possible.
EPA RESPONSE: We clarify that the scenario we chose to illustrate overtopping did not
occur during low-flow conditions, but was in response to a flood. We acknowledge that
failure at other times, and in response to other events, is possible (Section 9.3).
SLAUGHTER RESPONSE: OK - suggest that the brief statement on p. 9-15 that "an
overtopping event is only one potential failure mechanism" might be fleshed out a bit -
what other hydrologic events or conditions might lead to failure?
EPA FINAL RESPONSE: The TSFfailure scenarios have been revised. Box 9-4 and
associated text acknowledge various failure mechanisms, but clarify that outcomes would
likely be similar regardless of how the failure occurred.
46. Page 6-15 (Box 6.2): Box text implies that human error, lack of timely oversight and
correction was responsible - but never directly says "human error." The apparent assumption
that there is no hydrologic activity after freeze-up (or perhaps, after an ice cover forms on the
pool) was naive and incorrect. At least in that case, it appears that both dam and spillway
design (not adequately considering winter and ice conditions) and operation/inspection
(human error) were responsible.
EPA RESPONSE: The comment is probably correct. However, we have no evidence that
the commenter's conclusion that both engineering error and operator error were
responsible was correct.
SLAUGHTER RESPONSE: OK.
EPA FINAL RESPONSE: No response required.
47. Section 6.1.4.1: Appropriately recognizes the long time period for exposure, over extended
stream lengths, through both initial deposition and multiple re-mobilization and redeposition
events.
EPA RESPONSE: Agreed. No change suggested or required.
SLAUGHTER RESPONSE: OK
EPA FINAL RESPONSE: No response required.
48. Page 6-28 (S6.1.5 and Table 6-6): Seems jargon-laden and does not add to strength of the
Assessment.
EPA RESPONSE: Opinion has been divided concerning this explicit weighing of evidence.
Given that the analysis of risks to fish from exposure to spilled tailings involves six
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separate lines of evidence, EPA intended to show and discuss how the evidence was
weighed
SLAUGHTER RESPONSE: OK. It seems that the revised Assessment has better
wording and explanation.
EPA FINAL RESPONSE: No response required.
49. Page 6-29 (S6.1.7): Concur that remediation "...would be particularly difficult and
damaging..."
EPA RESPONSE: No changes suggested or required.
SLAUGHTER RESPONSE: OK.
EPA FINAL RESPONSE: No response required.
50. Page 6-30 (S6.2): Even though "We do not assess failures of the natural gas or diesel
pipelines...those pipelines would be equally susceptible to failure as the slurry line.
Concerns with pipelines crossing streams, watercourses and wetlands are similar to those
earlier expressed for the road corridor. Similarly, I suspect that careful inspection would
reveal many more "watercourses," including intermittent and ephemeral streams, than the 70
crossings cited.
EPA RESPONSE: A diesel spill has been added to the assessment, but it was judged that a
gas leak would not pose a potential risk to fish (Chapter 11).
SLAUGHTER RESPONSE: OK.
EPA FINAL RESPONSE: No response required.
The "probability" argument on p. 6-32 is an understandable attempt at quantification, but is
unpersuasive. Given the spill history of TAPS, pipelines in the Prudhoe Bay field, and
recently in Montana (?), suggesting the probability (with what confidence limits?) that there
"should be" only 1.5 stream-contaminating spills in78 years of operation seems wildly
optimistic.
EPA RESPONSE: These probabilities and frequencies are based on a large data set, not
just the TAPS experience (which is an atypical pipeline design and much larger than the
diesel line) or the spill in the Yellowstone River (which is a single event).
SLAUGHTER RESPONSE: The narrative of Section 11.1 is helpful. Many
uncontrolled variables inevitably affect the length/duration/failure analysis; I can
envision an argument that the transportation corridor pipelines will be in a tightly-
controlled (at least in early years) setting and subject to stringent inspection and
maintenance, in contrast to many thousands of miles of pipeline in more urban or
trafficked locales, with much more opportunity for vandalism, ignorance (ignoring the
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"do not dig here" warnings), or accidental damage - so the PLP corridor pipelines
should be more reliable that the historical record might indicate.
Of course, the TAPS line is much larger, insulated, partially above-ground on
thermopiles and partially buried, and atypical in size; it may also be atypical in that at
time of construction, it was designed with state-of-art flow and pressure sensors,
automated control systems, regular aerial patrol inspection, etc - yet still experiences
incidents, as does the network of gathering lines on the North Slope. And of course, the
Yellowstone river spill was a single event - as is every spill ~ so does not of itself provide
frequency analysis.
EPA FINAL RESPONSE: No response required.
Assuming that any spill (over the 78-year project span) would last only two minutes (pp. 6-
32, 6-34), with a consequent minimal volume of spilled material, also seems highly
optimistic. Even highly-automated systems, with redundant sensors and automatic responses,
are susceptible to error or failure, and the Bristol Bay watershed environment is not benign
with regard to mechanical apparatus.
EPA RESPONSE: EPA agrees with this comment and has increased the response time to 5
minutes.
SLAUGHTER RESPONSE: OK - I still think that even 5 minutes is optimistic.
EPA FINAL RESPONSE: The 5-minute duration was judged to be reasonable but, as
noted, it may be optimistic. This is highlighted as an uncertainty in Section 11.3.5.
The authors appear to recognize this with their discussion of the Alumbrera incident.
EPA RESPONSE: No change suggested or required.
SLAUGHTER RESPONSE: OK.
EPA FINAL RESPONSE: No response required.
51. Section 6.4: Potential road/culvert failures are recognized (again, not that ice issues are not
discussed). Extended periods for repair/rebuilding might be anticipated - witness the repeated
problems with the highway to Eagle, AK over the past several years - and that is a State of
Alaska responsibility, not that of a private company.
EPA RESPONSE: We agree with the commenter that extended periods for
repair/rebuilding might be anticipated. Chapter 10 of the revised assessment notes that
long-term fixes to a road that was damaged by erosional failure of a culvert may not be
possible until conditions are suitable to replace a culvert or bridge crossing. Further,
multiple failures, such as might occur during an extreme precipitation event, would likely
require longer to repair.
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SLAUGHTER RESPONSE: Chapter 10 appropriately addresses this.
EPA FINAL RESPONSE: No response required.
Potential for multiple simultaneous or concurrent failures is appropriate. Non-Alaska
examples would be the Pacific Northwest flood events of 1964 and 1996, both major
precipitation events with widespread flooding and road failures, in a region with much more
developed infrastructure and response capacity.
EPA RESPONSE: EPA agrees with the comnienter with respect to the likelihood for
multiple simultaneous or concurrent failures during extreme precipitation events. This is
alluded to in the assessment.
SLAUGHTER RESPONSE: This is mentioned on p. ES-24.
EPA FINAL RESPONSE: No response required.
52. Chapter 7: Recognition of probable additional mining activity, in the wake of a Pebble
project, is appropriate. Assessment is necessarily limited to currently-known potential mining
projects. The cumulative and irreversible consequences of multiple developments, with
associated road, power, housing, communications infrastructure ("secondary development")
should be more heavily emphasized, even though it is not possible to quantify all those
consequences.
EPA RESPONSE: The cumulative impacts of multiple developments, road corridors, and
secondary or induced development have been emphasized through additional discussion in
Chapter 13.
SLAUGHTER RESPONSE: The addition of Chapter 13 with its detailed analysis of
several possible scenarios, is welcome and appropriate.
EPA FINAL RESPONSE: No response required.
53. Chapter 8: Section 8.1.2 - note many potential failure modes not analyzed; the lack of
analysis in this Assessment should not be taken to mean that such failure could not or will not
occur.
EPA RESPONSE: Because the number ofpotential failures is extremely large, it is
necessary to choose a representative set offailure scenarios. The focus of the assessment
was on potential effects to salmon. The revised assessment includes more failure scenarios
(e.g., diesel pipeline failure, quantitative water treatment failure, and refined seepage
scenarios) and explains why these particular failure scenarios were chosen. Section 14.1.2
in the revised assessment explains that the assessment only presents a few failure
scenarios. EPA agrees with the comnienter that lack of analysis should not imply a failure
could or will not occur.
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SLAUGHTER RESPONSE: I did notice your statements on this, and appreciate the
thought given to Chapters 13 and 14.
EPA FINAL RESPONSE: No response required.
54. Table 8-1 (Row 2): The reasoning behind the statement that "Most [product concentrate
pipeline] failures would occur between stream or wetland crossing [sic] and might have little
effect on fish" is hard to understand; stream crossings, whether via elevated utilidors or via
sub-channel borings or utilidors, are locales of angular change, piping connections and
joints, and subject to stresses of hydrologic extreme events - so why would such sites be less
subject to potential pipeline failure?
EPA RESPONSE: Most of the corridor is not at or adjacent to a stream or wetland.
Therefore, failures are most likely to occur between streams or wetlands rather than at
streams or wetlands. The statement is not about probabilities per unit length.
SLAUGHTER RESPONSE: I fail to understand your response that "The statement is
not about probabilities per unit length." If you are saying that failure at stream
crossings or wetlands is not probable, because such crossings are a small proportion of
the total length of pipeline, then you must be referring to "probability per unit length."
My previous comment holds: stream crossings, whether via elevated utilidors or via
sub-channel borings, are locales of angular change, piping connections and joints, and
subject to stresses of hydrologic extreme events (which are not likely to occur between
stream crossings) - so why would such sites be less subject to potential pipeline failure?
EPA FINAL RESPONSE: We assume that the probability offailure is constant per unit
length. Therefore, no site is more or less subject to potential failure. However, the
statement in the assessment is correct because most of the length of the pipeline would
occur between stream or wetland crossings and therefore most failures would occur
between such crossings. The commenter is probably correct in stating that pipelines are
more likely to fail near water crossings, but we found nothing that would allow us to
estimate that additional risk.
55. Page 8-4 (Box 8-1): As noted elsewhere, the probability arguments for TSF dam failure are
not persuasive, and seem designed to imply that a TSF dam failure would not occur within
the next 10,000 years (or 3,000 to 300,000 years with three TSFs operational). This
implication is difficult to square with information on actual past failures presented in Box 4-4
and Table 4-8.
EPA RESPONSE: The discussion of this issue has been expanded to clarify that the
failure rate is a design goal and is not based on empirical evidence.
SLAUGHTER RESPONSE: The revised wording addresses this issue. Section 9.1.2
does clarify your reasoning. Box 9.1 and Table 9.1 demonstrate that failures can and do
occur. I remain uncomfortable with employing the terminologies of "dam year" or
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"mine year" which allow suggesting one failure every 2000 mine years, or every 714 to
1754 mine years. A cursory reading might well allow the impression that this means
2000 or 714 or 1754 years of TSF1 at Pebble, and therefore possible failure is of no
concern to the current or next ten to one hundred generations. See also Table 14.1,
which states that a tailings dam failure has a recurrence frequency of 2500 to 250,000
years - allowing the interpretation a Pebble TSF won't occur for the next 2500 years, so
why worry? Could the text and/or an addendum to the relevant tables and boxes,
explicitly differentiate between your "probabilities" and "recurrence frequencies",
versus "predictions"? A calculated recurrence interval says nothing about an event
actually occurring this year, next year, or 2500 years in the future; I still suspect that
some readers and decision makers may not immediately understand this.
A final note on this: P. 9-7 states that there were 88 observed or reported tailing dam
failures in the period 1960 to 2010; an average 1.7 failures per year, 1987 to 2007; "2 to
5 major tailings am failures annually from 1970 to 2001"; and 49 tailings dam failures
in the U.S (over an unstated period). These actual failures occurred within one human
life span, not within a span of 714 or 1754 or 2000 years. The calculated recurrence
frequencies or probabilities based on "dam years" or "mine years" can appear
reassuring; actual records of failures are not, given the irreversible consequences of
such a failure in the Bristol Bay watershed.
EPA FINAL RESPONSE: Box 9-3 was added to the final assessment to clarify the
meaning of failure probabilities.
56. Chapter 8: The potential risks and impacts are fairly and succinctly stated. Given the
extremely long-term nature of the projected Pebble project, and the irreversible changes
which would be imposed to the region, the risks seem, if anything, understated. I attribute
this to the decision to focus this Assessment on salmon and anadromous fisheries, with some
attention on salmon-mediated impacts - i.e., effects on indigenous culture, on wildlife other
than salmon, etc.
EPA RESPONSE: No change suggested or required.
SLAUGHTER RESPONSE: OK.
EPA FINAL RESPONSE: No response required.
John D. Stednick, Ph.D.
1. Page ES-9: Economics of Ecological Resources - section seems weak.
EPA RESPONSE: Economic data were included as background only. Economic effects of
mining are not assessed
2. Page ES-14: Overall risk to salmon and other fish. Never really separates fish species out in
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other discussions. Dolly varden more sensitive to metals?
EPA RESPONSE: The distributions of the salmonid species can be and are distinguished
by species, but not by their sensitivities to metals. For copper and some other metals, data
are available for rainbow trout that can be applied to other salmonids. Dolly Varden have
not been used as a test species.
3. Page 2-3 (P3): Four climate classes. Why this classification system? Perhaps easier to
identify by watershed maps?
EPA RESPONSE: Climate classes are used as defined from Feddema (2005) to give the
average annual moisture index. The Feddema Index was used as it broadly characterizes a
given landscape location on a spectrum of wetter to drier conditions due to the effects of
precipitation and evapotranspiration. Climate classes are used independent of watershed
boundaries, as this classification system allows one to compare regions that are either alike
or dissimilar across watershed boundaries and highlight that, depending on scale,
watersheds can be quite heterogeneous in their degree of water availability from
headwaters to mouth. The revised assessment now has five classes ranging from semiarid
to very wet as shown in Figure 3-1.
4. Page 2-5: Precipitation values - significant figures?
EPA RESPONSE: Precipitation values as shown in Figure 2-3 (Figure 3-2 in the revised
assessment) are calculated from SNA P data. SNA P data report monthly values of
precipitation to the nearest mm. During calculations, all precipitation values are rounded
to the nearest whole mm.
5. Page 2-23: Monthly values of streamflow. Would be nice to see average or daily streamflows
somewhere.
EPA RESPONSE: The purpose of this figure is to show the general pattern of annual
streamflows in this region. More detailed information (e.g., daily flows) are readily
available for the USGS gages, but those data are not necessary to illustrate general annual
trends.
6. Pages 3-7 to 3-11: Would like to see more discussion of conceptual models. If a picture is
worth a 1000 words
EPA RESPONSE: Conceptual models have been revised and new models developed, and
these models now appear in each of the risk analysis chapters to clarify the pathways
considered in each chapter.
7. Page 4-1 (PI): ... represent current good, but not necessarily best, mining practices. Why not
use the best methods or state of the art methods?
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EPA RESPONSE: With regard to the terminology of "best", "good", or other terms for the
practices used, what was intended to be conveyed in the assessment is that we assumed
modern mining technology and operations. The terms are qualitative when generally
interpreted, or have a regulatory meaning. The term "best management practices" is a
term generally applied to specific measures for managing non-point source runofffrom
storm water (40 CFR Part 130.2(m)). Measures for minimizing and controlling sources of
pollution in other situations are referred to as best practices, state of the practice, good
practice, conventional, or simply mitigation measures. We have added a text box in the
revised Chapter 4 to discuss terms.
8. Page 4-18: Shaded relief. Perhaps contour lines in another figure?
EPA RESPONSE: This figure is showing shaded relief of the landscape in Figure 4-6 and
is consistently used across multiple figures as a common base map for figures in this
assessment. It was decided to use shaded relief as opposed to contour lines to keep the
figure(s) cleaner in appearance, while also showing general topographic features. The
focus of this figure is on significant mineral deposits within the assessment watersheds and
not topography, therefore we have decided to keep the background as currently shown.
9. Page 4-21 (PI): ... most plausible sites given geotechnical, hydrologic, and environmental
considerations. Can this be elaborated?
EPA RESPONSE: This sentence was intended to convey that these locations have similar
geotechnical, hydrologic, and environmental conditions to the site of TSF1. A more
comprehensive overview of the geologic and geomorphic setting of the Nushagak and
Kvichak River watersheds is now provided in Chapter 3.
10. Page 4-21 (P2): The TSF would be unlined other than on the upstream dam face and there
would be no impermeable barrier constructed between tailings and underlying groundwater.
Is this correct? I thought I read the whole TSF would be underlain by liner?
EPA RESPONSE: The assessment states that TSF embankments would have an
engineered liner, but the impoundment is not lined in our scenarios. A full liner is possible,
but with very large TSFs, stability with a liner may become an issue and benefits must be
weighed against other potential adverse outcomes, as well as costs. This is something that
could be considered in a regulatory permitting process. No change required
11. Page 4-24: Leachate Recovered. This refers to only the leachate collected from the dam face?
EPA RESPONSE: No, this box refers to leachate from tailings and waste rock. The text
"leachate recovered" in the formula included in the box refers to the leachate recovered in
testing conducted by the PLP. No change required
12. Page 4-26: Water management. This is confusing. Collect precipitation for processing, yet
divert upstream waters around the mine and not use? Where are the leachate recovery wells,
and are they just a safeguard?
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EPA RESPONSE: Water management measures are now clearly described and discussed
in the revision (Section 6.1.2.5), and in sub-sections for the mine components in the
scenarios. Upstream water sources would be diverted around a mining site to minimize
losses of that water source to the environment, as it could remain uncontaminated The
leachate monitoring wells are to monitor groundwater downstream from the TSFs and
waste rock piles that would experience infiltration of their surfaces by precipitation falling
on them Those wells could be converted to recovery wells, or new recovery wells placed, if
it were found that seepage from these structures had contaminated the groundwater.
Measures are standard and common to existing mine sites.
13. Page 4-28: Significant figures on precipitation estimates? What is the ET and how is it
calculated?
EPA RESPONSE: The water balance is now discussed in detail in Section 6.2.2 and the
water inputs discussed in Section 6.2.2.1. In the revised assessment, we used the three
known USGS gages draining the Pebble deposit site [NK100A (USGS15302250) on the
North Fork Koktuli, SK100B (USGS 15302200) on the South Fork Koktuli, and UT100B
(USGS 15300250) on the Upper Talarik] to calculate monthly mean flows at each gage
over their period of record Monthly mean flows for each gage were summed across the
year and then averaged across the three gauges weighted by their watershed area to
produce an area-weighted average of net (Precipitation —ET) yearly runoff of 860
mm/year for the general deposit area. All data were presented to the nearest whole mm
14. Page 4-31 (P3): ...the mine pit would take approximately 100 to 300 years to fill. From
groundwater inflow only? Why such a large range of the estimate?
EPA RESPONSE: The time for the pit to fill was based on groundwater infiltration and
direct precipitation into the pit and was presented as an approximate range. The lower end
of the range of estimates pertained to the Pebble 2.0 scenario and the higher end pertained
to the Pebble 6.5 scenario. Current estimates are approximately 20 years, 80 years, and 300
years for the Pebble 0.25, Pebble 2.0, and Pebble 6.5 scenarios, respectively.
15. Page 4-50 (P3): This peak flow calculation and discussion is confusing and needs
clarification.
EPA RESPONSE: Presentation of the peak flow calculations and hydrologic modeling of
the TSFfailure scenarios has been revised and clarified This is now presented in Section
9.3.
16. Page 4-52: What is the recurrence interval of the 356 mm?
EPA RESPONSE: The recurrence interval is not reported in the reference cited The PMP
24-hr is greater than the reported 100-yr 24-hr (see Technical Paper No. 4 7).
http://www. nws. noaa.gov/oh/hdsc/studies/pmp. html
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http://www. nws. noaa.gov/oh/hdsc/PMP_documents/TP4 7.pdf
17. Page 4-60 (P4): Why a geometric mean using three values?
EPA RESPONSE: The three values were chosen because they represented subsets of the
available data that better represented the conditions of the proposed pipelines (i.e.,
pipelines less than 20 cm in diameter, pipelines in northern climates, and pipelines run by
small operators). Focusing on these three subsets reduced the range of the estimated
probability of failure. The geometric mean was used because the comparison involved
ratios with potentially significant differences in magnitude in the denominators. Using the
geometric mean typically reduces the bias that a small dataset can introduce into an
arithmetic mean. In this case, the difference between the two means (0.0010 vs. 0.0011) is
immaterial and small with respect to the range of failure probabilities.
18. Page 5-10: Define highest reported index spawner.
EPA RESPONSE: Section 7.1.2 defines this as the highest count of salmon reported in the
EBD for selected index reaches.
19. Page 5-20 (PI): ... salmon abundance related to pool size... .and beaver ponds provide
particularly large pools. Are data available to characterize the stream type? Are beaver
present?
EPA RESPONSE: We now provide a characterization of stream gradient, mean annual
flow, and % flatland to characterize general stream and valley characteristics. Beaver are
present in the area (Chapter 7).
20. Page 5-22 (P2): Assuming that no natural flow or uncontrolled runoff would be generated
from the mine footprint. Is all precipitation is intercepted or does this refer to the subsurface
streamflow generation mechanisms?
EPA RESPONSE: In our scenarios, we assume that all precipitation that falls within the
mine footprint (except the fraction of the TSF and waste rock leachate that bypasses the
groundwater interception and collection systems) is managed by the operator by collection
and routing leading to either storage in a TSF or testing, potential treatment, and release
to the environment. Any water consumed or stored on site would reduce the total
streamflow below baseline conditions, although some stream reaches would receive
increased stream flows due to discharges from the wastewater treatment plant.
Groundwater and streamflows are inextricably interdependent throughout the site, so one
could anticipate that areas with lower streamflows would also have lower groundwater
levels.
21. Page 5-23: It appears that the mean annual unit runoff is calculated incorrectly.
EPA RESPONSE: This has been corrected.
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22. Page 5-24: Table shows flow returned from footprint. Does not fit with page 5-22?
EPA RESPONSE: Water balance descriptions, tables, and figures have been extensively
revised
23. Page 5-29 (P2): Groundwater-surface water connectivity. Are data available to show this
connection throughout the watersheds or does the groundwater only return to the hyporheic
in the low gradient areas? Similarly, where are the temperature data that suggest the lake and
groundwater connection or this reference by incorporation?
EPA RESPONSE: Figure 7-14 is now included to illustrate areas of modeled upwelling
strength. We provide several examples of groundwater-moderated temperatures from the
EBD data. But water temperature data are not generally summarized here and we refer the
reader to the extensive data provided in the EBD.
24. Pages 5-32 to 5-39: The tables and hydrographs illustrating the potential flow changes are
difficult to appreciate or interpret. Another means of presentation?
EPA RESPONSE: We now include figures (7-10 through 7-17) illustrating the locations,
extent and magnitude of flow changes.
25. Page 5-41 (Table 5-13): The value of 0.15 km affected by the maximum mine size is
questioned.
EPA RESPONSE: Stream lengths are now rounded to 1 km
26. Page 5-52 (Table 5-17): Can we see summary statistics on water quality, not just means? Plot
of concentrations vs. streamflow?
EPA RESPONSE: Coefficients of variation have been added to the table (now Table 8-10).
Plots of concentrations versus other variables are available in PLP's Environmental
Baseline Document, Chapter 9.
27. Page 5-55: These effluent specific values are higher than those for background surface water
because of the higher content of mineral ions. This sentence needs clarification.
EPA RESPONSE: The sentence has been rewritten to clarify that it refers to differences in
the BLM-derived criteria.
28. Page 6-6 (Table 6-1): Last line. What is the +/- value after the mean?
EPA RESPONSE: + or- one standard deviation are reported for the basin-wide samples;
this has been clarified in the table.
29. Page 6-13 (P3): ...an intense local storm. Why use the Type la distribution for precipitation
distribution?
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EPA RESPONSE: This has been corrected to Type 1 per SCS guidance for Alaska.
Roy A. Stein, Ph.D.
1. Global (see Table 5-3 as example): Some thought should be given to significant figures for
the numerical values given in the report, especially so for Chapter 5, where much uncertainty
exists regarding stream lengths blocked (for example) by the mine footprint: .. 34.9 km of
first- through third-order streams..." will be eliminated. Rounding in this context makes
sense for we really do not know this impact to the nearest 0.1 km. I would encourage a
thorough review of these values throughout the report.
EPA RESPONSE: Significant figures for calculations and measurements by EPA have
been changed to reflect uncertainty (for example, stream length is reported to the km).
Significant figures from literature are not revised
2. Page 2-17: Salmon populations are closely managed by Alaska Department of Fish and
Game; how closely and what do we know of the populations that are managed regarding
numbers, resilience, variability, etc.? A box summarizing the fishery management practiced
by Alaska Department of Fish and Game would help put biological resources in perspective.
EPA RESPONSE: Box 5-2 has been added in Chapter 5, providing an overview of
commercial fisheries management in Bristol Bay.
3. Page 2-17: The importance of salmonids to marine predators is likely not an issue, given the
very large numbers of salmon stocked in the Pacific.
EPA RESPONSE: No changes suggested or required
4. Page 2-20: Nushagak and Kvichak rivers contain >58,000 km of streams; 13% is anadromous
fish habitat, but this is likely underestimated. How do we know this is an underestimate?
What proportion of this >58,000 km has been surveyed?
EPA RESPONSE: ADF&G estimates that the current listing of Waters Important for the
Spawning, Rearing and Migration of Anadromous Fishes represents "less than 50% of the
streams, rivers and lakes actually used by anadromous species" (ADF&G AWC database,
available at: www.adfg.alaska.gov/sf/SARR/AWC/)). This clarification has been added to
the assessment in Box 7-1.
5. Page 2-25 (bottom of page): I wonder if a bit more couldn't be written about the idea of a
salmon sanctuary, fleshing out the ideas of Rahr and Pinsky here.
EPA RESPONSE: The creation of salmon sanctuaries in the Bristol Bay region is a
management decision, and thus outside the scope of this assessment; therefore, no change
is necessary.
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6. Page 3-2: With all the items in the first full paragraph eliminated from consideration (e.g.,
power generations, worker housing, Cook Inlet Port), might the analysis herein be considered
minimal impact on the Bristol Bay watershed?
EPA RESPONSE: The scope of the assessment has been clarified throughout the
document, particularly in Chapters 1 and 2. It is true that this assessment only considers a
subset of potential impacts from large-scale mining.
7. Pages 3-7 to 3-11: These conceptual models might best be placed in the chapter to which they
refer; in so doing, it is easier for the reader to follow along. In turn, these models did not
seem to be discussed in text to the extent that they drove the impacts generated. Add more
explanatory text.
EPA RESPONSE: In the revised assessment, conceptual models are presented and
discussed in the appropriate chapters.
8. Page 4-5 (bottom of page): Typically, when citing a figure in another chapter, i.e., one not
near the current text, the format should be "see Figure 3-1" to keep the reader on track.
EPA RESPONSE: Comment noted Figure references have been retained in parentheses.
9. Page 4-8: Is there some chance of "block caving" here? Some text clarifying this point here
would be appropriate.
EPA RESPONSE: Additional information on block caving is provided in Chapter 4
(Section 4.2.3.1 and Box 4-4). Block-caving is a possibility for mining deposits that are
deeper. Sources of hazards assessed for risks, however, would be similar, as block-caving
and surface mining both create tailings, waste rock (block-caving does have a smaller
amount of waste rock), and sources of contamination to the water.
10. Chapter 4: Could these data and insights be productively moved to Chapter 5, thus reducing
redundancy? The organization would be 1) a description of the mine features relevant to the
text, then 2) a discussion of salmon and the mining impacts on their habitat. Separating these
into chapters seems artificial.
EPA RESPONSE: Revision of the assessment has included organization of material into
additional chapters and EPA believes this new organization is easier to follow.
11. Page 5-20 (P3): What does the phrase, "free-water area" mean? Ice free, perhaps?
EPA RESPONSE: Removed.
12. Pages 5-20 to 5-21: Paragraphs on these two pages reflect some of the redundancy that I saw
throughout the report. In the 3 rd full paragraph on page 5-20, text begins with
"... groundwater inputs may be critical..." and in turn on page 5-21 in the first full paragraph,
the topic sentence begins "...groundwater-influenced stream flow...likely benefit fish..."
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Both deal with the same topic. Hence, these two paragraphs could easily be combined,
serving to shorten the text, reduce redundancy, and improve readability.
EPA RESPONSE: These paragraphs have been combined.
13. Page 5-22: Similarly, the text on page 5-22 includes citations (at the end of the same
sentences) to both sections and tables and figures in Chapter 4. This suggests to me that the
text is not only overlapping, it is redundant and better overall report organization would serve
its presentation well.
EPA RESPONSE: Chapters have been reorganized, but some cross-chapter referencing
remains necessary. In this case, it is important that the reader be able to refer back to the
mine scenarios and operations chapter if desired, to better understand the complex water
management system and budget that drives the analysis in Chapter 7.
14. Page 5-23 (Table 5-5): Some explanation in the table title would benefit the reader, as to
where these gages are placed in the stream. The labeling is arcane at best UT100D; letters
suggest Upper Talarik Cr., but what is 100D. Now, I figured out from text that the first ones
were high in the watershed and then they proceeded downstream (increasing drainage area
gave me a hint as well). Use better descriptors (such as SKI through SK5 from low to high
stream order) or explain the ones that are being used.
EPA RESPONSE: New figures illustrating gage locations are included. Gage names
remain consistent with the EBD (PLP 2011) usage for consistency.
15. Page 5-26 (Table 5-7): I cannot find any bold in this table that would reflect the pre-mining
condition. Is that the same column as "Pre-Mining" as it is in Table 5-8 on page 5-34 (and the
next few tables as well)?
EPA RESPONSE: Corrected.
16. Page 5-27: Cite Figure 5-8 in text any time the stream gages are mentioned. The reader then
has the ability to easily refer back to stream gage locations.
EPA RESPONSE: Corrected.
17. Pages 5-32 to 5-39: How do these tables and figures differ? Might they be 10% reduction in
flow, 11-20% reduction inflow and >20% reduction in flow, as suggested in text? If so, then
these table and figure titles need to reflect this information and be better described in the
legends of the figures. Finally, do we need both tables and figures?
EPA RESPONSE: Figures have been removed, with exception on one illustration to
clarify process.
18. Page 5-31: The Richter et al. (2011) reference, which underpins this section is incomplete in
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the Literature Cited (Chapter 9), suggesting only March as the publication date. Update in
any revision.
EPA RESPONSE: Citation has been updated.
19. Page 5-31: It should be made clear that the Richter et al. (2011) sets quite specific bounds for
all rivers regarding ecosystem function and does not provide any specific insight into salmon
production (made somewhat clear in the last sentence of the next to the last paragraph on
page 5-43). I think an additional caveat stating this explicitly on page 5-31 would improve
the text.
EPA RESPONSE: Additional clarification has been added
20. Page 5-46: Stream flow losses due to the mine footprint are discussed first as underestimated,
then as overestimated, and then a conclusion that they are underestimated (i.e., because the
mine will need more water than is available from surface run-off). If this is the case, why go
through the other scenarios.. .to seem even-handed? I am not sure all of this text is required.
EPA RESPONSE: Uncertainties and assumptions sections have been revised
21. Page 5-46: Mine start-up will require more water than is available from the footprint of the
mine itself. Hence, water will be captured from other streams than just those associated with
the mine, which will influence stream flow and groundwater supplies. Are there estimates of
the amount beyond the surface water that will be required?
EPA RESPONSE: An extensively-revised water balance description and accounting are
now used Indirect effects of groundwater loss to pumping are incorporated.
22. Pages 5-53 to 5-58:1 am a little confused by this section. The implication throughout is that
copper toxicity will be based on the response of aquatic invertebrates (which would then be
protective of direct effects on salmon). However, near the end of this section, there is a
discussion about zooplankton being most sensitive and a comment about the reliance of
juvenile sockeye rearing in lakes on these zooplankton. Yet, there is no resolution of what
criteria will be used for toxicity values... will it be aquatic invertebrates or the more sensitive
zooplankton? Clarification is required here.
EPA RESPONSE: Zooplankton are aquatic invertebrates. The same criteria apply to both
invertebrates in the benthos and those that drift in the lake.
23. Page 5-59: "Discharge permits for mine in the Bristol Bay watershed should include relevant
whole-effluent toxicity testing and monitoring of biotic communities in receiving streams".
Does this quote solve the problem mentioned in the previous comment? Is this a realistic
expectation for mine operators before permits are issued?
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EPA RESPONSE: The statement reflects the hopes of the assessment authors. They do not
constitute an obligation upon the State of Alaska. This is clarified in the revised
assessment.
24. Page 5-68 (Table 5-22): >10% rather than <10% in the table title.
EPA RESPONSE: The reference was correct in the draft. Table 10-8 now shows streams
with gradients <12% likely to support salmon.
25. Chapter 6: Rivers is lower case when multiple rivers are listed.
EPA RESPONSE: Comment noted.
26. Page 6-1: Why assume that only 20% of the tailings stored would be mobilized with any dam
failure? Is there a justification for this important assumption? Yes, see Appendix I, page 14
for citation to Dalpatram (2011); this should be cited in the main report in Chapter 6.
EPA RESPONSE: Citations of Dalpatram (2011) andAzam and Li (2010) have been
added, drawn from Appendix I.
27. Page 6-4: Add map showing the impact of the failed TSF 1, i.e., distribution of sediments and
impact downstream.
EPA RESPONSE: Because we are not predicting specific sediment depths in this revision,
we have determined that this information was best presented by a description in the text
and tables.
28. Page 6-42: The sentence in mid-paragraph (3rd complete paragraph on this page) "... multiple
failures such as might occur..." My guess is that an example should follow the phrase "such
as."
EPA RESPONSE: Culvert failures are described in the preceding paragraphs (in greater
detail in the revised assessment), so an example is not needed here.
29. Page 7-2: The sentence at the end of the last full paragraph on the page makes little sense:
"The overall consequences are diminished and extinct salmon populations."
EPA RESPONSE: This sentence has been clarified
30. Page 8-6 (last sentence of 2nd complete para): "further" should be "farther"; sorry, I just
couldn't help myself...
EPA RESPONSE: Text revised
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William A. Stubblefield, Ph.D.
None.
STUBBLEFIELD RESPONSE: No additional comments are provided.
EPA FINAL RESPONSE: No response required.
Dirk van Zyl, Ph.D., P.E.
I have indicated a number of specifics in the text above and do not have any others to list.
Phyllis K. Weber Scannell, Ph.D.
1. Page 4-11: The document states "geomembranes are generally estimated by manufactures to
last 20 to 30 years when covered by tailings (North pers. comm...)." Unless North is a P.E.
with experience in geomembranes, the statement needs a stronger reference. For example,
Erickson et al (2008)* discuss the quality issues with geomembranes related to manufacture,
installation and application of a soil-based cover (such as bentonite).
EPA RESPONSE: The reference is appreciated, but others were chosen for use related to
time of life for liners. The discussion of liners has been expanded and moved to Chapter 4
(Section 4.2.3.4) in the revision, and includes additional material and references on
lifetime. The personal communication reference has been removed.
WEBER SCANNELL RESPONSE: Reviewer agrees with this change, provided the
appropriate references were given. North pers. comm. is not an appropriate reference,
unless as stated in the initial comment, North is a PE with recognized experience
pertaining to geomembranes.
The reviewer notes that more appropriate citations were used in revised Section 4.2.3.4.
EPA FINAL RESPONSE: No response required.
2. Page 4-23 (LI): This first sentence is confusing and implies that oxygen has low solubility
because it is in the tailings pond. Suggested change: eliminate the first phrase "In a TSF".
EPA RESPONSE: The change has been made in the revised assessment.
WEBER SCANNELL RESPONSE: Satisfied with change. The revised Assessment has
been corrected.
EPA FINAL RESPONSE: No response required.
3. Page 6-36 (P3): Last sentence states: [water] treatment would continue until institutional
failures ultimately resulted in abandonment of the system, at which time untreated leachate
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discharges would occur. This statement is not supported by any documentation and is not
clear what is being implied. Failure of governments? As stated in my response to questions,
any mine plan must include sufficient bonding and plans for reclamation, including necessary
water treatment.
EPA RESPONSE: Bonding and a perpetual trust could result in treatment for some
period, but it possible that long-term funding will not last to the end of time.
WEBER SCANNELL RESPONSE: Satisfied with recognition that this is a potential
problem. Reviewer notes that the issue of long-term or perpetual treatment is
mentioned in the revised Assessment. The initial comment has been addressed.
EPA FINAL RESPONSE: No response required.
4. Page 6-37 (P4): End of paragraph states "premature closure could leave waste rock piles in
place." Again, there is a need for plans for mine closure, concurrent reclamation and
sufficient bonding.
EPA RESPONSE: The premature closure scenario is intended to address the possibility
that the closure plan is not followed. It highlights the need for adequate bonding and for
plans that include closure by some agency.
WEBER SCANNELL RESPONSE: Satisfied with recognition that this is a potential
problem. Adequate bonding and plans for unexpected (temporary or permanent)
closure are critical. The reviewer is satisfied with the approach used in the revised
Assessment.
EPA FINAL RESPONSE: No response required.
5. App G, Page 5 (PI, last line): Document states: "... other short road segments connect
Dillingham to Aleknagik and Naknek to King (Figure 1)."
Shouldn't King be King Salmon?
EPA RESPONSE: Corrected.
WEBER SCANNELL RESPONSE: Satisfied with correction. The revised Assessment
has been corrected.
EPA FINAL RESPONSE: No response required.
6. App G, Page 5 (P3): Dolly Varden should be capitalized throughout the document. The list of
fish species should contain scientific names or reference a table of common and scientific
names.
EPA RESPONSE: Corrected.
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WEBER SCANNELL RESPONSE: Satisfied with correction. The revised Assessment
has been corrected.
EPA FINAL RESPONSE: No response required.
7. The document states "In the most comprehensive published field inventory, Woody and
O'Neal (2010) reported." Because the authors have not reviewed other documents on field
inventories, the phrase "most comprehensive" should be changed to "a comprehensive"
EPA RESPONSE: Corrected.
WEBER SCANNELL RESPONSE: Satisfied with correction. The revised Assessment
has been corrected.
EPA FINAL RESPONSE: No response required.
Paul Whitney, Ph.D.
A lot of page and paragraph comments are included the above responses to charge questions. I have
no further comment.
3.18 Appendices I and J
Phyllis K. Weber Scannell, Ph.D.
Comments on Revised Appendix I: Conventional Water Quality Mitigation Practices for Mine
Design, Construction, Operation and Closure
Many of the comments I raised in the initial review focused on the need for sufficient planning,
design, construction, management and closure of waste and water containment and for testing
materials for acid rock drainage (ARD) and metals leaching (ML). I stated these concerns in
the context of a need for an in-depth mining plan of operations. Appendix I addresses these
concerns; Page 1, paragraph 2 states: "The most important aspects of mitigation for any
mining site are proper planning, design, construction, operation, management, and closure of
waste and water containment and treatment facilities, and monitoring and maintenance over
all mine-life phases, including following closure." On page 3, the author addresses the issue of
progressive reclamation, an additional issue I raised in my initial comments. The information
contained in this Appendix satisfies many of the concerns I had with the initial Assessment. I
have a few minor comments, as listed below.
Page 5. Section 1.2 Accidents and Failures
The author states "If waste rock piles are designed properly with appropriate
mitigation measures, monitored and maintained, release of contaminants is possible,
but unlikely... " I would like to add "and the waste rock is adequately tested to classify
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as non-acid producing and non-metals leaching." There are examples of mines in
Alaska where supposedly benign waste rock was used to construct berms, etc and later
proved to be both metals leaching and acid producing because the testing to classify the
rock was inadequate to predict long-term chemistry.
EPA FINAL RESPONSE: The portion of the sentence "If waste rock piles are designed
properly with appropriate mitigation measures, monitored and maintained..." implies the
need for adequate characterization of the waste rock in order to choose the "appropriate
mitigation measures". Additionally, the introductory section included the need for
adequate characterization of materials in the sentence: "Planning for design and
construction must consider site-specific factors such as climate, topography, hydrology,
geology, seismicity, and waste material specific factors such as geochemistry, mineralogy,
particle size, and presence ofprocess chemicals." However, to clarify further, a change has
been made to the last sentence of the introductory section, which follows the
aforementioned sentence. The altered sentence now reads: "These factors should be based
upon accurate characterization and conservative estimates of future conditions to minimize
potential for failure over time." Additionally, to include ions (as well as the acidity), the
last paragraph of Section 1.0 has been changed to: "Waste rock is susceptible to acid
generation and leaching of ions due to the open pore..."
Section 2.1.1 Operational Phase, page 8, paragraphs 3 and 4
The author discusses different methods for constructing tailings impoundments and
their relative stabilities and the design criterion to potential earthquakes. This
discussion addresses concerns raised by the review committee in our initial review.
EPA FINAL RESPONSE: No change suggested or required.
Section 2.1.2 Closure and Post-Closure
The author states "Sufficient capital is required to finance inspections, maintenance,
and repairs in post-closure for as long as the tailings exist." This section of Appendix I
recognizes many of my initial comments about treatment into perpetuity and a need for
sufficient bonding. I am pleased that the discussions of closure and post-closure have
been included.
EPA FINAL RESPONSE: No change suggested or required.
Overall Comments
Appendix I contains a well-documented, thorough and informative discussion of
possible mitigation practices for mine design, construction, operation and closure along
with possible sources of failure. The appendix is an important contribution to the
Assessment and addresses many of the comments and concerns I raised in the initial
review.
EPA FINAL RESPONSE: No change suggested or required.
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Comments on New Appendix J: Compensatory Mitigation and Large-Scale Hardrock Mining
in the Bristol Bay Watershed
Appendix J provides the legal framework for compensatory mitigation (Section 1) followed by
a discussion of different approaches. Section 2 relates more directly to the Bristol Bay area.
Section 2 contains a summary of the important ecological functions of the headwater streams
and associated wetlands in this region. These sections (1 and 2) provide background and
authority for compensatory mitigation and are important additions to the revised Assessment.
The Appendix next presents different opportunities for mitigation, most of which would not be
beneficial. The arguments presented in this section are well-documented and clearly describe
the limitations. The author concludes "There are significant challenges regarding the potential
efficacy of compensation measures proposed by commenters for use in the Bristol Bay region,
raising questions as to whether sufficient compensation measures exist that could address
impacts of this type and magnitude.
I found this discussion to be realistic, well-documented and defensible. There are no changes I
would recommend. In fact, it is well-written and provides important supporting information to
the Assessment.
EPA FINAL RESPONSE: No change suggested or required.
3.19 Follow-on Comments outside the Scope of the Original Peer
Review
Courtney Carothers, Ph.D.
As per the terms of my peer review contract and supplemental clarification of the scope of
work, I provide here my summary evaluation of the U.S. EPA's response to: 1) the key
recommendations in the Executive Summary of the Peer Review Report that pertain to my
areas of expertise and 2) the individual comments and suggestions that I provided in the Peer
Review Report. This summary is based upon my review of the following documents:
1. The April 2013 version of the draft Bristol Bay Assessment (referred to as "Revised
Assessment" in this letter). This document is available at:
http://www.epa.gov/ncea/pdfs/bristolbay/bristol_bay_assessment_erd2_2013_voll.pdf.
2. Revised Appendix I (Conventional Water Quality Mitigation Practices for Mine
Design, Construction, Operation and Closure) and new Appendix J (Compensatory
Mitigation and Large-Scale Hardrock Mining in the Bristol Bay Watershed). Other
appendices are not considered part of the evaluation being conducted under this
contract. Appendix I is available at:
http://ofmpub.epa.gov/eims/eimscomm.getfile?p_download_id=513560. Appendix J is
available at: http://ofmpub.epa.gov/eims/eimscomm.getfile?p_download_id=513561.
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3. Final Peer Review Report, External Peer Review of the EPA's Draft Document, An
Assessment of Potential Mining Impacts on Salmon Ecosystems of Bristol Bay, Alaska,
dated September 17, 2012 (referred to as "Peer Review Report" in this letter). This
document is available at: http://www.epa.gov/ncea/pdfs/bristolbay/Final-Peer-Review-
Report-Bristol-Bay.pdf.
4. An Assessment of Potential Mining Impacts on Salmon Ecosystems of Bristol Bay,
Alaska, External Review Draft, dated May 2012. EPA 910-R-12--004a.
5. The draft response to comments document detailing how the EPA responded to
comments provided by the external peer reviewers in the Peer Review Report
(referred to as "EPA Response" in this letter).
EPA FINAL RESPONSE: No response required.
Editorial corrections:
Page vi: Affects to Effects
Page ES-2, ES-25, (and others): Alaska native to Alaska Native (consistent usage throughout
document)
Page ES-9: first full paragraph, first full sentence, rewrite to: "The subsistence way of life in
many Alaska Native villages is augmented with participation in the cash economy."
Pages 1-6,14-13: fisherman to fishermen
Page 5-2: 8watersheds
Page 5-2: "These resources generate significant benefit for..., and provide sustenance for
Alaska Native populations and other rural residents."
Page 12-9: second full paragraph, period missing at end of first sentence, incorrect comma.
EPA FINAL RESPONSE: Editorial changes made in final assessment.
Section 5.2.6 (p 5-27): The last paragraph of this section should add language about the
holistic fishery systems in this region. In addition to the relatively pristine salmon ecosystems
and populations, the region is occupied by indigenous human cultures who continue to
occupy their homelands, speak their languages, and continue to depend upon these intact
fisheries. These features of the Bristol Bay fishery systems also greatly add to the watershed's
global conservation value.
EPA FINAL RESPONSE: Language has been added to the final assessment to acknowledge that
a sustainable, intact salmon-based culture adds to the global value of the fishery.
Table 5.1 (p 5-3): Some subsistence use species described in Box 5.1 are not listed in Table
5.1 as harvested (H) species (e.g., least cisco, round whitefish; and broad whitefish, which
does not appear in Table 5.1).
EPA FINAL RESPONSE: The caption for Table 5-1 clarifies that (H) indicates that those species
are targeted. Least cisco and round whitefish occur in the assessment area, but in our judgment
neither species are not normally targeted (although they harvested incidentally during fisheries
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targeting other species). We have added clarification to Box 5-1 that the species listed are
harvested, both by direct efforts (i.e., targeted species) and incidentally (i.e., non-targeted species).
Although broad whitefish appear in some Bristol Bay subsistence harvest lists, they are not known
to by biologists to occur in Bristol Bay watersheds. Mention of broad whitefish has been deleted
from Box 5-1, as they are not applicable to the assessment area.
Section 12.2.3 and Box 12.1 (p 12-11): The text preceding Box 12-1 states that Bristol Bay
residents have expressed mixed opinions about development and mining. Box 12-1 focuses
only on concerns about potential effects of large-scale mining in the Bristol Bay watershed.
These are effective at conveying some of the testimony received about concerns; however,
missing are excerpts of testimony representative of those who expressed desires for jobs and
development related to large- scale mining. The EPA authors could add in a couple of
additional quotes reflecting the full spectrum of opinions expressed in the testimony received
at public meetings. If the excerpts in Box 12.1 represent the bulk of testimony received, this
point should be made in the box text. I also attach several editorial corrections in an email
correspondence.
EPA FINAL RESPONSE: All the noted editorial corrections have been made in the final
assessment. Statements from residents supporting large-scale mine development have been added
to Box 12-2 (which was previously Box 12-1).
I commend the EPA team for careful and thoughtful revisions of the sections I have
reviewed closely. I appreciate the attention given to the peer review comments throughout
this process of review and revision. Please let me know if I can answer any questions or be of
further assistance.
EPA FINAL RESPONSE: No response required.
Dennis D. Dauble, Ph.D.
This letter report was developed in response to Statement of Work (SOW), Revised Draft
Bristol Bay Assessment Peer Review Follow-On, of June 2013. The general approach as
specified by the SOW was to 1. Review key recommendations in the Executive Summary of the
17 September 2012 Final Peer Review Report, External Peer Review of the EPA's Draft
Document, An Assessment of Potential Mining Impacts on Sainton Ecosystems of Bristol Bay,
Alaska (Draft Assessment), in addition to specific comments and suggestions provided on the
Draft Assessment by myself (Contractor); 2. Review the EPA's response to the Peer Review
Report, Draft of June 12, 2013; and, 3. Review the April 2013 revised Draft Assessment, revised
Appendix I and new Appendix J to evaluate how well these documents incorporated and
responded to comment provided by this Contractor.
EPA FINAL RESPONSE: No response required.
On June 26, 2013,1 received an e-mail from Jenny Thomas, EPA Contracting Officer, that
suggested peer reviewer letter reports be organized in a manner to allow EPA to easily see how
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our evaluation comments correspond to their responses to the Peer Review Report.
Consequently, I used EPA's draft response to comments document as a template for my
evaluation. My evaluation comments follow EPA's bold italicized responses in blue font.
EPA FINAL RESPONSE: No response required.
It should be noted that several of my first-round review comments were responded to by
referring to changes made to appendices to the main report. However, without having these
appendices to examine, it was impossible to assess whether my comments were adequately
resolved in the revision process.
EPA FINAL RESPONSE: Electronic versions of the revised appendices were available to the
reviewers, but their review was not required as part of the follow-on review process.
Additional comments of concern to this reviewer that did not neatly fit into the peer review
response to comment document format are attached as a separate document. These comments
are both editorial and technical in nature and should be considered prior to release of the final
Assessment document.
EPA FINAL RESPONSE: See responses below.
In terms of overall organization, the second draft is much improved. One issue is Section 6.4
(conceptual model) included with descriptions of the mine footprint and operations did not
work for me. I do agree, however, that this section serves as a useful transition from Mine
Scenarios (Chapter 6) to the first risk assessment chapter (Chapter 7). To resolve this
arrangement, I suggest you either (1) Move Section 6.4 to the end of Chapter 5 and expand the
Introduction/Overview to Chapter 7 to include a brief discussion that it is the first of several
risk assessment chapters, or (2) make Section 6.4 a separate chapter (after the current Chapter
6 and before the current Chapter 7).
EPA FINAL RESPONSE: Although we understand the reviewer's concern, we believe that the
current placement of Section 6.4 is the most appropriate, given that, as the reviewer notes, the
section serves as a bridge between the problem formulation and risk analysis sections of the
assessment.
Although the title says "ecosystem", one weakness of the document continues to be the paucity
of ecological information, i.e., the ecosystem does not begin and end with salmon Nutrient
exchange focuses almost entirely on the role of salmon and marine-derived nutrients.
Watershed and terrestrial inputs are rarely discussed, nor is bottom-up energy flow from
algae/periphyton to aquatic invertebrates to fish. I revisit this point several times in my other
comments.
EPA FINAL RESPONSE: The context-dependent variation in the relative importance of
watershed, benthic, terrestrial, and marine energy subsidies to aquatic foodwebs (e.g., as described
in Wipfli and Baxter 2010 and Janetski et al. 2009) is discussed in Sections 5.2.5 and 7.2.3.2.
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Overall, the second external review draft was impressive in terms of detail, supporting graphics
and tables, and depth of discussion. One challenge to having so many complex tables was that
often little or no narrative text was provided, leaving the reader to figure out their meaning
largely on their own. I strongly suggest adding one or two sentences for each table in the text
prior to the "call out" that states key results or example data from that table.
EPA FINAL RESPONSE: We have enhanced the descriptions of tables, where needed,
throughout the text.
One useful addition to the second draft was the summary of evidence tables. Although
somewhat subjective (or qualitative), they helped provide nice summary of effects for each
exposure scenario. I could provide numerous examples of other useful tables and figures but
there were too many to count. Needless to say this document should serve as a model for
completeness. The authors should be collectively proud of their accomplishment.
EPA FINAL RESPONSE: No response required.
The following specific technical and editorial comments are also offered to improve the
Assessment document.
1. p. ES-4, line 4- On what basis would the site be monitored during the post-mining
phase? Would a specific state or federal regulatory requirement be in effect?
EPA FINAL RESPONSE: Requirements put in place by federal and state agencies would
likely require some level of monitoring and reporting during the post-mining phase to
ensure that mine wastes are properly contained and that any on-going water treatment was
taking place as planned.
2. p. ES-28, bullet 4- There should be an additional statement about uncertainty as it
relates to effects on primary and secondary production, hence the salmonid food web.
EPA FINAL RESPONSE: Uncertainty concerning salmonidfood is mentioned in the first
bullet of the following section.
3. p. 5-34, last line of page- The call out for Table 5-1 should come after "non-salmon
fishes."
EPA FINAL RESPONSE: Change made in the final assessment.
4. p. 7-12, section 7.1.2- Please clarify if aerial index counts are estimates of individual fish
or redds.
EPA FINAL RESPONSE: Index counts are of spawning salmon.
5. p. 8-29- Please state if avoidance is considered harmful (i.e., fish are excluded from
preferred habitat) or good (i.e., they are able to detect and move to non-polluted areas).
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EPA FINAL RESPONSE: It is likely to be good for the individual in the short term, but
bad for the population in the long ternt. However, that is a presumption that is not backed
by actual field studies.
6. p. 8-31, line 19- Based on what author's experience?
EPA FINAL RESPONSE: The phrase has been deleted.
7. p. 8-43, Table 8 19- Is something missing here? No data is presented.
EPA FINAL RESPONSE: This comment is unclear. That table and others in the chapter
contain the relevant data.
8. p. 8-48, Table 8 22 and p. 8-49, Table 8 23- What does the dash or hyphen (-) mean in
these tables? No data or no effect?
EPA FINAL RESPONSE: No effects (the estimated concentrations are below the lowest
benchmark value). This has been added to the Notes section of each table.
9. p. 8-62, section 8.3.1.2- Heat transfer between atmosphere and stream bottom will likely
over-ride and mitigate any increases in water temperature than might occur
downstream of the confluence of the source.
EPA FINAL RESPONSE: Heat exchange in downstream reaches is acknowledged as a
critical factor, and will be informed by temperature modeling. No change required.
10. p. 9-19, line 12- The reference to Tables 9-3 and 9-4 provides an opportunity to provide
relevant examples of depth and velocity from each scenario.
EPA FINAL RESPONSE: Relevant examples have been added.
11. p. 10-20, section 10.3.2- Please clarify the last sentences of the 1st paragraph.
EPA FINAL RESPONSE: The sentence has been clarified.
12. p. 11-11, line 11- This sentence implies contaminated groundwater would expose
aquatic organisms to toxic concentrations. Suggest add a caveat, such as "If toxic
concentrations were present in groundwater, areas of upwelling might pose a risk to
aquatic invertebrates and fish eggs/larvae unless sufficient dilution occurred."
EPA FINAL RESPONSE: The caveat has been made explicit.
13. p. 11-17, line 16- "non-trivial" is an odd choice of words. Suggest replace with
significant or large or substantial.
EPA FINAL RESPONSE: We believe that this term expresses the state of knowledge better
than the suggested alternatives. No change required.
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14. p. 12-5, line 3- the dietary maximum for pigs and poultry can be used as a surrogate
benchmark for what? All wildlife? Bears and ducks? Please state.
EPA FINAL RESPONSE: They are surrogates for piscivorous mammals and birds,
respectively.
15. p. 12-8, line 14- It's not obvious there is reliance of subsistence users on water for
transportation in the area of probable impacts due to water-withdrawal. Specific
locations should be identified if possible.
EPA FINAL RESPONSE: We know of no data on the extent of water-based transportation
necessary for subsistence activities that we can compare with the expected extent of water
withdrawal impacts, but we raise this as a potential concern related to water withdrawal.
We state that access is important and a reduction in seasonal water levels could pose
obstacles, and we believe this statement is correct.
16. p. 13-8, line 15- Note that additional mines might also "tier off' the infrastructure
developed for the Pebble 0.25 scenario.
EPA FINAL RESPONSE: We have clarified that any potential mine site would require at
least a mine pit and waste rock disposal area, and that mines affiliated with or close to an
existing mine may make use of that mine's infrastructure. In subsequent analyses, we
calculate areas of the mine components for these mines both with and without tailings
storage facilities included.
17. Chapters 8, 9 and 13 included insufficient discussion of risk to primary and secondary
production. For example, there would be loss of production due to sediment deposition
and scouring (tailings dam failure), due to floe formation from leachate (water
collection, treatment and discharge), and would multiply across projects (cumulative
effects). Further these alterations in the aquatic community would impact focal fish
species through loss of food, and, ultimately, subsistence lifestyles.
EPA FINAL RESPONSE: Chapter 8 has a new subsection on effects of copper on primary
production. The comment on floe formation seems to refer to the formation of aluminum
and iron hydroxide floes in many cases of acid mine drainage. The leaching tests suggest
that phenomenon would not be significant in streams receiving tailings or waste rock
leachates. Chapter 9 discusses effects of sedimentation and scour on invertebrates.
Gordon H. Reeves, Ph.D.
EPA did a good job with the revision. All of the primary issues that I raised appear to have
been considered but there were a few that I did not agree with the response [see comments
throughout document].
EPA FINAL RESPONSE: See responses to these specific issues in previous sections of this
document.
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Specific comments on revised report:
1. p. 3-44-45. You need to talk more explicitly about the potential impacts of warmer
winters.
EPA FINAL RESPONSE: Text and a figure (Figure 3-19) that deal with the sensitive egg
incubation stage and winter temperatures have been added.
2. p. 3-45. Good point about the importance of genetic diversity.
EPA FINAL RESPONSE: No response required.
3. p. 7-16. You should make the point that the percent of stream affected does not
necessarily accurately reflect the potential impact.
EPA FINAL RESPONSE: This point is acknowledged. Text has been added to Section 7.2
highlighting the value of the coarse-scale characterization in 1) providing insight into
differences in stream valley characteristics across spatial scales, and 2) emphasizing
spatial variation in stream characteristics and potential fish habitat quality and quantity.
4. p. 7-32.1 think that it is important not to just list potential mitigation measures but to
also assess the potential for success. I think that you would be hard pressed to find
examples where mitigation has even compensated for a fraction of the impact of given
activities. Particularly present assessments for mining.
EPA FINAL RESPONSE: Appendix J now includes discussion of the challenges
associated with potential mitigation measures, and these are referenced in Chapter 7.
5. p. 10-6. This is a particularly good diagram.
EPA FINAL RESPONSE: No response required.
Charles W. Slaughter, Ph.D.
Attached are my comments in response to the Statement of Work regarding review of the
documents: (1) EPA Response to Peer Review Report, External Peer Review of EPA's Draft
Document An Assessment of Potential Mining Impacts on Sainton Ecosystems of Bristol Bay,
Alaska, and (2) EPA 910-R-12-re004Ba, April 2013, An Assessment of Potential Mining
Impacts on Salmon Ecosystems of Bristol Bay Alaska, Volume 1, Second External Review
Draft.
As you had recommended, my comments are appended to appropriate sections of the first
document.
My "review" of the larger main report was limited to checking specific points, evaluating
degree of incorporation of reviewers' 2012 recommendations into the revision, and gaining an
overall impression of the present state of the draft assessment. The time allotted did not permit
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a truly comprehensive, paragraph-by-paragraph review of that document (nor was such review
requested). Nevertheless, I must compliment the authors for their work. The revised
Assessment is a major (almost "quantum leap) improvement over the 2012 effort,
incorporating much new analysis and discussion. The many conceptual models, flow charts,
maps, figures and tables are very useful. I specifically applaud (1) the decision to add chapters
on the transportation corridor, cumulative impacts, and integrated risk characterization, and
(2) the integration of uncertainty and risk characterization considerations into the topical
chapters.
EPA Final Response: No response required.
p. ES-4, last para: The clarification that "This assessment does not consider all impacts
associated with future large-scale mining in the Bristol Bay watershed" is appreciated. A deep-
water port, electrical generation capabilities (or electricity import via now non-existent
transmission lines from a potential new hydroelectric facility being considered on the Susitna
River), one (or more) airports and associated infrastructure, extended road and ORV
networks, and the gamut "induced development" and support services associated with
increased activity and worker populations (and, later, sport and recreational visitations), will
all have a cumulative and enduring impact on the Bristol Bay watershed and environs and its
present human, wildlife, and fisheries systems, which temporally and spatially will extend far
beyond the posited PLP operation itself.
Thus, the question is left hanging - if this assessment does not or cannot address the full suite
of probable consequences of the PLP project, what agency or entity does have that
responsibility?
EPA FINAL RESPONSE: If the Pebble Limited Partnership decides to move forward with a
proposed mine, it would need to apply for a Clean Water Act Section 404permit from the U.S.
Army Corp of Engineers (among other permits). Any permit decision by the U.S. Army Corp of
Engineers would need to comply with the National Environmental Policy Act, and a project of this
scope would presumably require development of an Environmental Impact Statement, which
would examine the full suite ofpotential impacts.
Maps - the ES maps are clear and are appreciated.
EPA FINAL RESPONSE: No response required.
Figure ES-3 - at least on my print (and computer screen) the subtle shadings of blue or green
associated with regions re difficult to distinguish - but the message of the figure is clear that
Bristol Bay is the major sockeye salmon producer, and the Nushagak and Kvichak rivers
dominate that production.
EPA FINAL RESPONSE: This figure has been revised in the final assessment so that divisions
are clearer.
Table ES-4 ~ (1) The attempted clarification of your use of probability analysis for TSF failure,
provided in the main body of the assessment, is appreciated. However, this reviewer still
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questions the message sent, both in the Executive Summary and in the larger report, that a
TSF failure has a "recurrence frequency of 2500 to 250,000 years." This strongly implies to a
reader of the ES (and most decision-makers will read or skim only the Executive Summary)
that with 2500 years as the shorter time span stated, no one should worry about a possible TSF
failure, despite the report's documentation of actual failure incidents elsewhere. I suggest
eliminating reference to "recurrence interval" in this discussion. (I personally have seen a 100-
year recurrence interval (based on period of record) flood occur twice in one year in one
watershed, belying any suggestion that recurrence interval is related to prediction of event
occurrence.)
EPA FINAL RESPONSE: We agree that the probabilities and frequencies can be difficult to
understand. We have added Box 9-3, which explains how the failure frequencies and probabilities
are derived and how they can be interpreted. A condensed version of this material has been added
to the Executive Sunmuiry.
Table ES-4 - (2) Pipeline spill possibilities - based on the "probability" column, if there is a
95% probability of a product concentrate pipeline failure over 25 years, and the same applies
to the return water and diesel pipelines, then there is 95% probability of three pipeline failures
over 25 years, or nine in the 78-year Pebble 6.5 scenario.
EPA FINAL RESPONSE: We consider a failure of each of the three pipelines as individual
failure scenarios. We do not provide the combined spill frequencies for the pipelines because their
consequences would be quite different. Therefore, we have not added a statement to the effect that
failure of at least one line is virtually certain.
p. ES-26—bottom para ~ The statement that "Although remediation would be considered if
spills contaminated streams, features of the Pebble deposit area would make remediation
difficult" suggests that remediation would be only considered but not required, because
remediation would be infeasible - so what then? The difficulty is acknowledged, but no solution
is suggested - such stream-contaminating spills would simply be accepted as a cost of doing
business, or collateral damage?
The final sentence suggests that unspecified "compensatory mitigation" might be considered,
but the analysis provided in Appendix J suggests that compensatory mitigation is simply not an
alternative in the Bristol Bay watershed system. Suggest revising or eliminating this sentence.
EPA FINAL RESPONSE: This point has been clarified in the Executive Sunmuiry.
Finally, I must compliment the authors on the overall comprehensive coverage of the Executive
Summary. As mentioned above, many users of this document will only go to the ES. My own
preference might be for even more emphasis in the ES on the long-term unavoidable
cumulative effects, but I concede that the text does a good job of summarizing those
consequences in individual sections.
EPA FINAL RESPONSE: No response required.
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William A. Stubblefield, Ph.D.
Based on my review of the second external review draft of the Bristol Bay assessment document
it is my impression that the USEPA has committed substantial time and effort to revising the
original assessment document resulting in a greatly improved report. For the most part, all of
the technical and editorial comments made regarding the original document have been
satisfactorily addressed in the current revision. Substantial improvements in the organization
and content of the document were made including:
• Incorporation of background information regarding the use of a risk assessment-based
approach to addressing the issues,
• Inclusion of an explanation for the inception of the assessment and its ultimate utility
to risk decision-makers,
• Addition of a clear discussion of the uncertainties associated with the assessment and
the potential implications of those uncertainties, and
• Inclusion of an evaluation and application of the "state-of-the-science" regarding the
assessment of metals toxicity in the aquatic environment, inclusion of "new" European
REACH regulation-based data, and the importance of consideration of bioavailability
have been addressed.
Although additional changes and incorporation of additional "new" data and recent scientific
literature would further benefit the document, I think, in its current form, it more fairly
represents the current "state-of-the-science." Therefore, I would commend the USEPA for its
efforts in revising the original assessment report.
EPA FINAL RESPONSE: No response required.
Dirk van Zyl, Ph.D., P.E.
This peer review follow-on of the Revised Draft Bristol Bay Assessment is provided in
fulfillment of an agreement with the US Environmental Protection Agency. It specifically
responds to the following requirement from the Scope of Work for the task:
The contractor shall provide a letter report evaluating how well the revised draft
Bristol Bay Assessment addresses both the key recommendations provided in the
Executive Summary of the peer review report and the specific comments provided by
the Contractor in the peer review report.
While Volume 1 of the Revised Draft Bristol Bay Assessment was completely reviewed, the
evaluation below focuses narrowly on the aspects required by the Scope of Work. The report
provides some overall review comments in the next section followed by two sections providing a
few comments on the Executive Summary and the specific comments provided by this author
in the 2012 peer review report.
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The Scope of Work did not request or propose any specific format for the compilation of this
review. One approach would be to repeat the original comments and the EPA responses before
providing the comments from this review. It is clear that this approach will result in a very
extensive document. The author decided on the following approach to reduce the length of this
document (note that for the first two bullets it is assumed that the page numbers in the final
public version of the EPA Responses will be the same as the Draft available for this review):
• In Section 3 below a specific topic and page number will be referred, the latter as:
"EPA Response, p#".
• In Section 4 below the specific question will be referred to plus the page number as
follows: "EPA Response Q#, p#".
• References to the Second External Review Draft Documents will be to page numbers as
follows: "Second Draft, p#".
EPA FINAL RESPONSE: No response required. Note that page numbers do differ between the
drafts available for review and the final versions, for both the assessment itself and the response to
comments document (as explained in Section 1 of this document).
The restructuring and revisions presented in the Revised Bristol Bay Assessment resulted in a
much improved document that provides better motivation for selection of specific hypothetical
project elements and assumptions. It also provides further detail information, maps and
summaries that improve the logic and approach of the document and associated analyses.
The document also strives to provide transparent information about the use of input data, e.g.
reports by non-governmental organizations. It is stated that the "USEPA subjected some of
these documents to external review before incorporating this information into the assessment"
(Second Draft, p. 2-3). These reports and the reviews are available at
http://cfpub.epa.gov/ncea/bristolbay/recordisplay.cfm?deid=182065. While the reports and
reviews are provided for broad review, the value of the described external review will
undoubtedly be questioned for its independence and credibility. It is also interesting to note
that many reports from other credible sources were provided to the public record in 2012 but
that none of them were apparently considered "useful" to EPA in their preparation of the
Revised Draft. The author questions the objectivity of this process and therefore the overall
scientific value of the review report by EPA.
EPA FINAL RESPONSE: The reviewer does not state what reports and what credible sources he
believes should have been cited or how they should have been incorporated into the assessment.
We cited those reports submitted during the public comment period that contained original data or
analyses that were relevant and otherwise unavailable.
Phyllis K. Weber Scannell, Ph.D.
Attached by email is a document titled FinalCommentsPWS.docx. This comments document
contains the summary evaluation of EPA's response to the September 2012 peer review report
of the revised Bristol Bay Environmental Assessment. This document fulfills tasks 2.1, 2.2 and
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2.3 of the Statement of Work. Note that Task 1 was fulfilled by email on June 14, 2013 and
EPA's acknowledgement of that email on June 17, 2013.
I have structured the referenced document in a way that I believe is most useful to EPA. The
document contains the initial comment to the earlier Assessment, the EPA response, my
response to the comment and my comments on how the revised Assessment satisfied the initial
concerns. Should you have any questions about the information I have provided, please contact
me by email or telephone. Thank you.
EPA FINAL RESPONSE: No response required.
The revised Assessment has been substantially re-organized and includes important additional
information. EPA is to be commended for an excellent job. The revised Assessment is
thoroughly documented, contains better explanations and incorporates the concerns of this
reviewer.
EPA FINAL RESPONSE: No response required.
Paul Whitney, Ph.D.
The revised assessment is responsive to many of the suggestions offered by the peer review
members. As a result the revised assessment is much improved.
EPA FINAL RESPONSE: No response required.
My comments on the EPA Draft Assessment were made before I met the other members of the
peer review group and before I was familiar with their expertise. Once I was able to discuss my
many concerns with other members of the peer review group it became clear that many of my
concerns would be addressed by reviewers with more expertise in a particular area. For
example, I was concerned about the level of detail given to water balance calculations, cone of
depression and water routing. Others with mine engineering and hydrology expertise expressed
similar concerns, outlined specific problems and offered more detailed suggestions for ways to
improve the assessment. In this current review, I mostly defer my responses to EPA responses
to those with more expertise. As a result, for the most part, I limit my responses to issues
related to wildlife. If I do not offer a comment regarding an EPA response, one can assume I
agree with the EPA information offered or have addressed the topic in another place in this
document.
EPA FINAL RESPONSE: No response required.
Needless to say, I do not agree with the EPA decision not to include direct impacts on wildlife
and wildlife functions in their assessment. The decision to only address fish mediated impacts
on wildlife side steps the facts that wildlife are an important component of the salmon
ecosystem and that impacts on wildlife mediate impacts on fish. I doubt if EPA will change
their position/decision based on my lone voice for a true Bristol Bay ecosystem analysis that
includes direct impacts on fish and wildlife and their habitats. None-the-less, I state my
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contrary opinions as I feel so moved based on my scientific training. My contrary opinions are
expressed one time in the following PHW Responses. I save my time and EPA's time by not
repeating the same contrary opinions over and over.
EPA FINAL RESPONSE: We do not state and do not believe that wildlife are not part of the
salmon ecosystem. The assessment addresses salmon-mediated risks to wildlife. Direct effects of
potential mining on wildlife are outside the scope of the assessment, although we acknowledge
that these effects may be significant. Given the economic, ecological, and cultural importance of
the region's key salntonids, and stakeholder and public concern that a mine could affect those
species, the primary focus of the assessment is the abundance, productivity, and diversity of these
fishes. Wildlife and Alaska Native cultures are also considered as endpoints, but only as they are
affected by changes in salmonidfisheries.
3.20 Follow-on Reviews Organized by Chapter
Executive Summary
John D. Stednick, Ph.D.
The Executive Summary order of findings does not parallel the assessment order; i.e. culvert
failure, streamflow modification, TSF failure.
EPA FINAL RESPONSE: Executive summaries are not just condensations of the report. They are
written for a different audience and have a different organization.
ES-2. Pebble 0.25, 2.0, and 6.5 are not 'defined' until page ES-10. As in the abstract a 'better'
defense or justification of these values would be useful.
EPA FINAL RESPONSE: The materials on page ES-2 define the scope of the assessment. The
definition provided there is adequate and appropriate for that purpose. The material on page ES-
10 defines the mining scenario and therefore provides an explanation of the reason for those
particular sizes.
ES-11 PAG and NAG are not defined in this chapter.
EPA FINAL RESPONSE: This comment refers to the use of acronyms in Table ES-1, which are
defined in a footnote to that table.
ES-14. Hard to follow the sentences with the 'respectively' areas or km affected by alternative
plans.
EPA FINAL RESPONSE: The sentence has been rewritten to make it clearer.
ES-15. Where are the data for the copper toxicity? Would be helpful to present these data.
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EPA FINAL RESPONSE: We disagree. This is an executive summary and it would be
inappropriate to include the details of data behind the analyses. Those who are interested may
consult the entire assessment report.
ES-16. Culvert failure rate seems excessive.
EPA FINAL RESPONSE: The culvert failure rate is explained and justified in Chapter 10.
ES-17. The mitigation or prevention of spills is to use impact-resistant containers is an
oversimplification. What about handling and other spill containment facilities?
EPA FINAL RESPONSE: Truck accidents on the road can be mitigated by impact-resistant
containers. However, the material is not handled while being trucked and spill containment
facilities are practical at fixed facilities such as tanks but not for trucks.
ES-17. PLP is never defined in this section.
EPA FINAL RESPONSE: It is now spelled out.
ES-17. Would be helpful to better separate the TSF failures for scenarios Pebble 2.0 and 6.5.
EPA FINAL RESPONSE: We have carefully read that section and do not see how the material
might be made clearer by greater separation of the two failure scenarios.
ES-17. Table suggests that there is no copper toxicity to fish under Pebble 0.25.
EPA FINAL RESPONSE: That is correct. At that size, waste rock leachate is captured in the cone
of depression in our scenario. When the wastewater treatment plant is operating correctly there
should be no copper toxicity in the receiving streams.
ES-18. Wetland loss unquantified or unquantifiable? Low culvert failure, yet failure rate is
47%?
EPA FINAL RESPONSE: Wetland loss due to reduced flow is potentially quantifiable, but was
not quantified in this assessment. The second comment apparently refers to Table ES-4. The low
culvert failure rate is during operation when levels of inspection and maintenance are assumed to
be high. Higher failure rates (e.g., 48%) would occur after operations when the level of inspection
and maintenance would be the same as other roads. That case is described in the next line of the
table.
ES-21. The comparison of the TSF height to national landmarks is anthropocentric. Suggest
that reference be deleted.
EPA FINAL RESPONSE: No change required. This figure is presented to give readers a sense of
the scale of the tailings dam heights. We chose national landmarks because these are most
familiar to readers.
ES-22. Copper toxicity to fish is less clear. Does this refer to the risk assessment or the
literature? Literature is well established, so why the disconnect?
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EPA FINAL RESPONSE: The literature on the toxicity of copper-containing sediment particles to
fish is, in our opinion, not clear. Our summary and analysis of the relevant literature are
presented in Chapter 9.
ES-23. Why would Pebble 2.0 extend further and last longer?
EPA FINAL RESPONSE: More tailings would be spilled in a Pebble 2.0 failure than in a Pebble
0.25 failure.
ES-24. Reference for a diesel spill recovery in 1-3 years in cold environments?
EPA FINAL RESPONSE: The literature is summarized in Chapter 11 and it includes a case from
Alaska, farther north than Bristol Bay.
ES-25. ...effects of a large mine on salmon. The use of the word single in this sentence is
confusing.
EPA FINAL RESPONSE: The sentence has been rewritten without the word "single."
ES-26. The inclusion of a groundwater drawdown in Pebble 0.25 increased the amount of
wetland loss by 84%. Similar results for the other scenarios. State the approximate acreage, the
use of percentages is often misleading.
EPA FINAL RESPONSE: The 84% value refers to the proportional increase in wetland loss at the
Pebble site, which could be used to estimate the increase at other sites. Hence, the percentage
increase in wetland loss at the Pebble site is relevant but the absolute loss is not. This statement
has been updated in the final assessment to reflect that inclusion of the drawdown zone increases
the area of stream and wetland losses by roughly 50% in the Pebble 0.25 scenario.
ES-28. Standard leaching test data are available for test tailings and waste rocks from the
Pebble deposit, but these results are uncertain predictors of the actual composition of leachate
from tailings impoundments, tailings deposited in streams and on their floodplains, and waste
rock piles. This statement is confusing and does little to support any findings of the potential
effects of metals, especially copper being mobile in the aquatic environment. Suggest this be
reworked.
EPA FINAL RESPONSE: The quoted sentence is not about metal toxicity or copper mobility in
the aquatic environment. It is about leachate formation and release and the relevance of leaching
tests. We have rewritten the sentence in the hope of making it clearer.
Roy A. Stein, Ph.D.
Executive Summary (ES). I liked the summary, especially the tone, the emphasis on
quantitative statements (with supporting tables, maps and figures), the ecological services that
the Bristol Bay watershed provides, the multiple scales at which the problem was examined, the
4000-year history of subsistence (and sustainable) fishing by Native Alaskans, the wildlife
resources beyond the salmon and trout (some consideration of their macroinvertebrate food
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supply as well), the three different scenarios re the Pebble Mine, the words and probabilities
that surrounded the discussion of Tailings Storage Facilities (TSF) failures (and other failures,
as documented from the scientific as well as the grey literature), the idea that current
technologies are simply insufficiently developed (page ES-15) to capture a sufficient proportion
of the waste water to prevent salmon impacts, and the expectation that the Pebble Mine will
likely lead to a "mining district". I believe EPA has struck just the right balance with regard to
summarizing the state of the probable mine impacts on the ecological and cultural resources of
the Bristol Bay Watershed. I have provided only a few comments for consideration by the EPA
authors.
EPA FINAL RESPONSE: Introductory statement; no response required.
1. Figure ES-2. My presumption here is that the "blue" streams are ones for which we
simply do not know if we have salmon in them or not...likely yes, but no one has
documented their presence. Is this correct?
EPA FINAL RESPONSE: The blue streams are not identified as containing salmon,
either because they have been sampled and no salmon were found or they have never been
sampled.
2. Figure ES-3. This figure could use some improvement. It should be pointed out that
these are not truly run sizes but rather proportions of run sizes for comparative
purposes. I think spending a bit of text comparing Bristol Bay production to other
areas of the world (Part A of Figure ES-3) would be useful for it emphasizes the unique
nature of the Bristol Bay Watershed.
EPA FINAL RESPONSE: This figure has been revised to make the divisions clearer and
clarify that is shows proportions of run sizes.
3. On page ES -8, you argue that "the Yup'ik and Dena'ina are two of the last intact,
sustainable salmon-based cultures in the world". And what does "last" mean in this
context? How many more are out there? Some context would benefit the reader and the
report.
EPA FINAL RESPONSE: The introduction to Appendix D of the assessment includes
some information about cultures worldwide in which anadrontous salmon are or were a
chief component of subsistence. Based on this information, the authors of Appendix D
conclude that the Yup'ik and Dena'ina cultures in the Bristol Bay region are "among the
few remaining cultures still relying on wild salmon as a chief source of nutrients."
4. On page ES-9, do we have any idea what the proportion of Native Alaskans find this
hard-rock mining approach to be preferable over salmon or other subsistence ways of
life? Do we have good polling numbers that summarize the point of view of Native
Alaskans re this project?
EPA RESPONSE: EPA has not conducted polling on this subject. There is information
about it in Appendix D, but it is limited to Elders who were interviewed in seven villages
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throughout the watershed. That group overwhelmingly expressed the value of a subsistence
way of life, but they were not numerically polled, because the purpose of the interviews was
to gain understanding of the culture. Some outside groups have conducted polling in the
region. However, polling results were judged to be outside the scope of the assessment.
5. Page ES-14 talks about "streams known to provide spawning or rearing habitats". Isn't
this quite a conservative way to go? How does the reader account for reality in these
statements?
EPA RESPONSE: This is a conservative estimate, as it is a known underestimate of true
salmon habitat. These uncertainties are discussed in detail in Chapter 7.
6. "In perpetuity" seems to be danced about a bit here, but I am happy that it is indeed
discussed and emphasized here in the Executive Summary. Of course, I would like to
see more definitive statements re this issue here in the Executive Summary.
EPA RESPONSE: No response required. We have reread the sentences using that phrase
and they seem to be clear.
Abstract
John D. Stednick, Ph.D.
The abstract states the purpose of the document is a risk assessment evaluating the
environmental risk of mining in the area. The first document was criticized because there was
not a specific mine plan. There needs to be a better description of how the three different levels
of mining activity were determined. The mine plan alternatives (Pebble 0.25. 2.0 and 6.5) and
associated quantitative effects are listed as respectively but are hard to follow. Sentence
structure could be improved. Discussion of this range of 'alternatives' needs to be expanded.
EPA FINAL RESPONSE: The Abstract has been deleted in the final assessment, since the
Executive Summary serves as a more thorough summary of the assessment.
Roy A. Stein, Ph.D.
Unfortunately, the Abstract on page 1, given its shorter format and lack of detail, simply misses
the mark. Here the same items mentioned in the Executive Summary should be mentioned in
some form here. Clearly, the 29 pages of the ES allows for space to discuss the most important
issues. Within the abstract, I suggest that the EPA authors abstract the current ES and in so
doing work to capture most of the relevant, even critical, points made therein. Emphasize the
ecological and cultural resources in this watershed, the greatest sockeye population ion the
world, the leakiness of the habitat (with groundwater shared among many streams), meaning
that mine impacts will stray far beyond where toxic wastes might first be generated. I don't
think the authors should concentrate on impacts that are "at a minimum"; rather the abstract
should discuss failures and their impacts. Add something about Iliamna Lake, about the TSF
having to be maintained "in perpetuity", and the many other points made in the ES. I
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recognize that the authors are limited by space considerations within the abstract, which makes
this a difficult section of the report to write. I'm afraid that EPA authors have done what many
of us have done: write the abstract last, after all other sections of the report have been written,
typically having to generate this quite important section under intense time constraints. I urge
the authors to rewrite this section with an eye toward my comments above, thus allowing the
reader to appreciate the high points of this revised draft document.
EPA FINAL RESPONSE: The Abstract has been deleted in the final assessment, since the
Executive Sunmuiry serves as a more thorough sunmuiry of the assessment.
Chapter 1
John D. Stednick, Ph.D.
General comments: Introduction to purpose of document. Identification of risk assessment
endpoints.
EPA FINAL RESPONSE: No response required.
Specific comments:
1. 1-1. High hydrologic diversity is apparently a new term as related to a diverse fish
population. Diverse as well as productive?
EPA FINAL RESPONSE: Diversity of hydraulic habitats can contribute to productivity by
allowing fish the potential to move among different rearing, feeding, and resting
environments to optimize growth and survival (as mentioned in Chapters 3 and 7).
2. 1-2. Is the document for a 404(c) decision or a risk assessment? Confusing still.
EPA FINAL RESPONSE: It is a risk assessment, which may be cited in decisions on
whether to initiate a 404(c) determination.
3. 1-3. Salmon is the endpoint. Wildlife and culture are secondary endpoints. Does this
change the effects of stressors on these endpoints?
EPA FINAL RESPONSE: The choice of endpoints does not change the effects of a
stressor. It changes the analyses that are performed.
4. 1-4. Inform the public of the biologic and mineral resources of Bristol Bay. Only based
on the readily available materials. I doubt that PLP is showing all the mineral deposit
data.
EPA FINAL RESPONSE: No response required.
5. 1-5. This document is not to invoke CWA 404(c), but is a risk assessment. One cannot
equate open pit mine impact as filling of wetlands only.
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EPA FINAL RESPONSE: The assessment is clear in stating that it does not address all
aspects of mining. However, it covers much more than filling of wetlands.
Roy A. Stein, Ph.D.
Page 1-2. I very much like the idea that this document has been defined as an Ecological Risk
Assessment or ERA; hence, those who understand the role of these documents in the review
process re the Clean Water Act can now place this document in its appropriate context (i.e.,
essentially used to inform environmental decision-making). How resources of interest (salmon
and their habitat) are influenced by stressors generated by an activity (namely, copper mining).
In this case, salmon are the primary assessment endpoint and wildlife (owing to marine-derived
nutrients) and Alaska Native cultures (owing to their request to have the EPA enter the fray)
are secondary endpoints—some confusion existed about the choice of these variables in the first
draft. We now have an explicit rationale for these choices, which should then permit a better
understanding by readers of the role of this document in the decision-making process re the
Pebble Mine.
EPA FINAL RESPONSE: No response required.
Chapter 2
John D. Stednick, Ph.D.
General comments: Introduction to assessment, including mine alternatives and data sources.
EPA FINAL RESPONSE: No response required.
Specific comments:
1. 2-2. Some minor data sources were used without peer review? Identify.
EPA FINAL RESPONSE: The use of non-peer reviewed data has been clarified in the
Chapter 2 text.
2. 2-3. Reference to Ghaffari report, please identify where or what data were exclusively
available in said report.
EPA FINAL RESPONSE: The Ghaffari et al. (2011) report is cited where it is used as a
source of data or other information.
3. 2-4. Endpoint based on decision maker needs. Suggest that the outcome is pre-
determined. Change the endpoints, change the conclusion. Similarly on 2-7, stressors
outside the scope could have environmental consequences.
Reference to Challenger event is not needed and suggest it be deleted.
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EPA FINAL RESPONSE: We acknowledge throughout the assessment that both stressors
and sources we considered outside the scope of the assessment could have significant
effects on our endpoints. Reference to the Challenger event is appropriate because it
illustrates that past failure rates are relevant, despite the argument that better, more
technologically advanced design goals make past failure rates obsolete; no change
required.
4. 2-8. Reference to HUC's seems out of place.
EPA FINAL RESPONSE: HUCs were added in response to an earlier review comment
that requested specific information about areas encompassed by each geographic scale; no
change required. However, Box 2-4, which briefly explains the National Hydrography
Dataset and HUCs, has been added to Chapter 2.
Roy A. Stein, Ph.D.
Page 2-2.1 liked the conceptual model diagrams.
EPA FINAL RESPONSE: No response required.
Page 2-2. The emphasis on peer-reviewed publications is appropriate for a science-based
assessment, even given that all of the data herein cannot come from this source, for we know so
little about the Bristol Bay Watershed. I like how EPA characterized under what situations one
could use data from the Fraser River mining operations, or those from Idaho and Montana;
context here is immensely useful, helping to guide the reader through the set-up of the report.
EPA FINAL RESPONSE: No response required.
Page 2-4.1 liked how EPA anticipated the criticism from developers re how risk assessment
from "old" technologies cannot be used to estimate risk for newer technologies and then used
the Challenger accident to show how new, improved technology can fail too. The justification
for using historical failure rates (because new technologies may have new ways to fail) is
compelling. This argument is critical to the readers.
EPA FINAL RESPONSE: No response required.
Page 2-8. I liked the various scales used and the fact that EPA provided a number identified as
percentage of the scale above, for it helped me judge absolute and relative sizes of geographic
areas represented in these scales. Table 2.1 should have a title associated with it and the mine
scenario formats should decline in size per the scales in the table. Just seeing Figure 2.2 does
help me envision the situation. I wondered about the Transportation Corridor in Figure 2.2
inset thinking that indeed it covered the entire watershed of all streams, rivers, and wetlands
influenced by the road from the Pebble site to Cook Inlet. That was eye-opening and reflects
the impact of the road on the watershed, reinforcing some who believe that the road has an
impact far beyond its seemingly narrow footprint. Figures 2.2 through 2.7 are stellar and a
valuable addition to the ERA.
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EPA FINAL RESPONSE: Table 2.1 is titled "Geographic scales considered in the assessment".
The order of mine scenario footprints has been changed as recommended.
Figure 2.6 (page 2-13): How are we to distinguish 'wetlands' from other water-body types in
this figure. The legend doesn't help us much here but I guess I could envision (if I squint)
wetlands as compared to lakes or rivers/streams. Using colors that exhibit more contrast could
aid in interpretation of this figure.
EPA FINAL RESPONSE: We have revised many of the maps in the final assessment to show
streams and rivers from the National Hydrography Dataset and lakes and ponds from the National
Wetlands Inventory in light blue, and wetlands from the National Wetlands Inventory in dark
blue.
Page 2-14. I appreciated the references to National Hydrography Dataset but worry that it
adds detail that I simply do not get. "HUC 12 Level" is what, indeed? Could there be one
additional inset box that might explain to the novice (especially if this document is to inform
the citizenry), serving to define the terminology?
EPA FINAL RESPONSE: Box 2-4, which briefly explains the National Hydrography Dataset and
HUCs, has been added to Chapter 2.
Chapter 3
John D. Stednick, Ph.D.
General comments: Introduction to the study site setting, with a strong emphasis on physical
attributes. A reader unfamiliar with the setting would be hard pressed to understand all the
physical, biological, and cultural resources present. Materials can be gleaned from the
appendices and add to the chapter utility. I would argue for presentation of more data for site
characterization. The surface water -groundwater connection is significant hydrologically and
biologically. Much of the impact assessment is loss or disruption of these hyporheic flows. I
think elaboration on the determination and areal extent of this is important and should be
included in this chapter.
EPA FINAL RESPONSE: Chapter 3 deals largely with the physical environment of the region;
biological and cultural resources are discussed in Chapter 5. We agree that surface water-
groundwater connections are hydrologically and biologically significant in the region. Examples
of locations with high groundwater-surface water interaction, as indicated by temperature
anomalies in summer thermal profiles and ice-free areas during winter fly-overs, are presented in
Chapter 7. Additional quantification of groundwater-surface water exchange was beyond this
scope of this assessment.
Specific comments:
1. Figures 3.1 to 3.7 have useful information and data that are not developed in the text
per se. These should be presented to the reader via text as well as figure.
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EPA FINAL RESPONSE: Figures 3.1 through 3.7 are not explained fully in the text, but
key points from the figures are highlighted throughout the Chapter 3 text; no change
required.
2. 3-12. Based on extensive studies in the Pebble area... I am always uncomfortable with
value judgments of this sort. When or what is extensive? Does this imply that the PLP
data are the sole source, the best etc?
EPA FINAL RESPONSE: The word extensive has been removed from this sentence.
3. 3-13. The hydrologic landscape as related to the physiographic landscape elements?
Hydrologic landscapes defined by calculating the water surplus, which is an obtuse
definition of streamflow. Yet the next section discusses the importance of groundwater
exchange for salmonid habitat. And earlier it was stated that: Permeable shallow
aquifers, upwards hydraulic gradients, and strong local relief indicate that local and
intermediate groundwater flow systems dominate regional groundwater flow systems.
Crosscuttingfaults with high hydraulic conductivities....
EPA FINAL RESPONSE: The objective of the hydrologic classification is to characterize
coarse-scale variation in expected hydrologic characteristics for the region. Variability in
coarse surficial deposits, lakes, and other hydrologic influences will be partly, but not
completely, captured by the combination of physiographic region and climate class used in
our classification. This is why the sections that follow strongly emphasize the role of
groundwater and lake systems in streamflow regimes.
4. Groundwater exchange and flow stability make for more stable habitat? Meaning is
unclear.
EPA FINAL RESPONSE: This statement has been clarified to indicate that higher
proportions of groundwater contribute to more moderated flow regimes with lower peak
flows and higher base flows, thus creating a less temporally-variable hydraulic
environment.
5. Large and small lakes support flows that are more stable than ... other salmon streams.
What is the definition of stable here? What represents a departure from stability?
EPA FINAL RESPONSE: All rivers express a flow regime, and some are more variable
than others. This sentence is simply making a relative comparison, and is followed by the
phrase 'moderated and consistent' to describe lake-influenced streaniflows. By this we
mean a flow regime with lower peak flows and higher base flows, or less temporal
variability.
6. Mixed messages. Need to characterize the system hydrology including groundwater
components with hyporheic exchanges, then relate to salmonid habitat. This section is
the description of the Region, yet few data are presented and the inference of hydrology
to habitat is unclear. Suggest a chapter reorganization to improve overall chapter flow
and logic.
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EPA FINAL RESPONSE: Chapter 3 presents a regional overview. Specific examples of
hyporheic exchanges and relevance to salmon habitat within the study area watersheds are
provided in Chapter 7.
There are considerable data that are available that would could improve this section.
For example the USGS collects streamflow, precipitation, and temperature data. Daily
plots of these data would provide a better site characterization. For example:
^USGS
USGS 15302200 KOKTULI R NRILIAMNA AK
Oct GlWov GIDec GlJan GIFeb Q«ar Glflpr GHay GlJun QUul Glflug GISep GJOct G3
2G12 2G12 2G12 2G13 2G13 2G13 2G13 2G13 2G13 2G13 2G13 2G13 2G13
Provisional Oata Subject to Revision
Discharge • Flow at station affected by ice
When coupled with precipitation data this better illustrates both snowmelt and rainfall
events. The monthly hydrograph time steps do little to illustrate the system dynamics.
EPA FINAL RESPONSE: Daily data do of course provide additional detail, but for
general patterns of annual regimes monthly data meet our objective ofproviding a broad-
scale perspective in Chapter 3.
7. 3-18. Differences in hydrology, geology, and climate across...create the regions diverse
hydrologic landscapes ...ultimately shaping aquatic habitats. These diverse habitats
support a high level of biological complexity, in part supported by enhanced ecosystem
productivity associated with salmon runs, contributing to the environmental integrity
and resilience of the watersheds integrity and resilience on the watershed's ecosystems.
Although I do not disagree with this statement as a summary or concluding statement,
an introductory statement it is unsupported. Although citations are given (out of
order—list by date), I think the development of this statement is lacking in this section.
This is again a value judgment that may not necessarily be repeated by the outside
reader.
EPA FINAL RESPONSE: We disagree. It is common practice to begin with a topic
sentence (or sentences) then support those sentences in the following text.
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Habitat complexity. Abundant and diverse array of aquatic habitats. Change in
terminology. Are these terms precise?
EPA FINAL RESPONSE: Habitat complexity is described in greater detail in Section 3.4,
where we describe complexity in terms of diversity of habitat unit types, hydraulic
conditions, tributary junctions, and off-channel development. These terms may not be of
high precision, but are widely used in the stream geomorphology and ecology literature.
Section needs to be developed in a more logical fashion, so reader can be lead to the
same conclusions.
EPA FINAL RESPONSE: We believe that this section is organized in a logical fashion.
8. 3-18. Streamflows are listed as mean annual flow (m3/sec). Figure 3.10 shows
streamflow as monthly runoff in mm.
EPA FINAL RESPONSE: Figure 3-10 is referenced in the section discussing flow regimes
and lake and groundwater influences. Presenting streamflow as runoff allows comparison
of regimes across streams and rivers with widely different mean annual streamflows. Both
types of data are useful, and both are presented in their respective contexts.
9. 3-18. ..correlated flow paths? How were these four gradient classes determined? How
many are in each class? How do these compare to physiographic landscape elements
and hydrologic landscapes?
EPA FINAL RESPONSE: Gradient classes follow the process-based classification of
Montgomery and Buffington, as described in the text. The distribution of streams (by
length) is illustrated by the cumulative frequency histograms and the table summarizing
stream characteristics. Relating these characteristics to the hydrologic landscapes was
beyond the scope of this assessment.
10. 3-19. Box 3.1. Why start with the statement that the measured gradient of the NHD flow
lines were not accurate compared to the topography defined by the DEM? We have
seen this inconsistency repeatedly with these comparative methods (including streams
that go up and over the watershed ridge). This text box (and others) read more like the
user manual for the GIS operator and I would submit should only be briefly
commented on in the text. The findings could be better presented in the text box, which
is the 'take-home' message.
EPA FINAL RESPONSE: Throughout the assessment, text boxes are used to present
detailed information on analyses that some readers may find too technical and that are not
directly related to the assessment's major findings. Thus, these methods-oriented text boxes
are only briefly mentioned in the text, whereas key findings of the assessment are discussed
more thoroughly in the text.
11. 3-21. ...indicate significant spatial variability in thermal regimes. Why not define and
present this material?
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EPA FINAL RESPONSE: Examples follow in the subsequent sentences in this paragraph.
12. 3-24. Mean annual flow is a metric of stream size. So is peak flow. How the streamflow
classes selected and what were the ranges of the watersheds measured?
EPA FINAL RESPONSE: The streamflow classes were selected to capture the range of
stream/river sizes present in these watersheds, with divisions selected to capture examples
of stream size classes ranging from small streams to large rivers. Values for these classes
and the frequency of occurrence (by length) are presented in the table and figure in the
results section.
13. 3-25. Text box expresses mean annual flow as cubic feet per second—not metric. The
equation makes no sense and uses British units as well.
EPA FINAL RESPONSE: The equation has been corrected. It is from the original source
(as noted), which uses cubic feet per second
14. Below the text box is a paragraph that suggests that the salmonid species propensity for
small streams varies. What is the relation between salmonid habitat and stream size? If
the usage varies, why the exercise in stream classification by MAF? This paragraph
does not flow with the present section organization.
EPA FINAL RESPONSE: Text has been moved to clarify its connection to the discussion
of space limitations in streams.
15. 3-26. Specifically define each scale. What is scale 1? Why are scales 3, 4, and 5 listed but
presented later? Edit section.
EPA FINAL RESPONSE: These scales are defined in Section 2.2.2; this has been
clarified in the text. We have also clarified why scales 3 through 5 are discussed in later
chapters.
16. 3-28. Water quality section is wanting. There has been a large water quality data
acquisition effort done by numerous parties in the study area. A summary table of
mean concentrations for 3 large river systems is an underrepresentation of that effort
and does not provide an adequate water quality characterization for risk analysis.
These data are listed as background concentrations. Are all samples above areas of
mineralization? Changes over time now that the area has been drilled? Groundwater
chemistry values? Concentration relations to streamflow? No nutrient data, but
nutrient return from spawning salmon was presented as significant for system
productivity. Are metals dissolved or total? TDS values cannot be reproduced by
addition of presented analytes. What are the precipitation chemistry inputs? What are
the changes over time (years?). Speculation on climate change influence on water
quality? If significant spatial variability in thermal regimes, would the same be
expected or seen in water quality?
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EPA FINAL RESPONSE: Chapter 3 focuses on the entire Nushagak and Kvichak River
watersheds, for which there is not much detailed water quality information. The April 2013
draft of the assessment included data from mine scenario watersheds in both Chapter 3
and Chapter 8 (e.g., Table 3-4 and Table 8-10 contained much of the same information).
In the final assessment, the mine scenario watershed data have been removed from
Chapter 3 to better reflect the overall structure of the assessment, in that Chapters 3
through 5 consider broader geographic scales (i.e., the Bristol Bay watershed and the
Nushagak and Kvichak River watersheds).
17. 3-28. Seismicity section is out of place.
EPA FINAL RESPONSE: We disagree; no change required.
18. 3-36. Climate change. A generic description of climate change scenarios, but little
linkage to changes in hydrologic processes in the study area. Are such potential changes
addressed later? Scenarios of changes in precipitation and temperature due to climate
change (using SNAP); what is the existing record and variability in temperature and
precipitation? Streamflow records could be used to better illustrate past variability.
Have salmon runs been related to streamflow conditions? How variable is the system
using existing records? I think this section is too qualitative and was disappointed with
the effort.
EPA FINAL RESPONSE: A full evaluation of climate change in the region is outside the
scope of this assessment. However, specific repercussions of climate change on mine-
related impacts are addressed in Box 14-2.
Roy A. Stein, Ph.D.
Pages 3-13 and 3-14.1 liked how the text relates groundwater flow and flow stability and
communication among rivers streams and wetlands to the success of salmonid fishes. This
certainly is a critical feature of these two watersheds. Following this idea through the document
is critical, in my mind, to assessing the impact of the Pebble development on native salmon.
EPA FINAL RESPONSE: No response required.
Page 3-35.1 can see how you came to the conclusion that it difficult to predict how many and
what magnitude earthquakes will play in the Pebble Mine development.
EPA FINAL RESPONSE: No response required.
Page 3-36.1 was extremely pleased to see climate change predictions and just how the
environment might change. You compared your conclusions re change to those generated by
other scientists and all fell within a range that lent credence to your results. Nicely done.
I also liked the idea of doing multiple scenarios re the extent of climate change.
EPA FINAL RESPONSE: No response required.
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Page 3-45. The conclusion generated with regard to the impact of climate change is a relevant
one. Salmon will only persist in the face of climate change by using all of the genetic and life
history diversity that they now have. Reducing this variability (i.e., via the impact of the Pebble
Mine) can only lead to loss of stocks.
EPA FINAL RESPONSE: No response required.
Chapter 4
John D. Stednick, Ph.D.
General comments: Overview of mining processes and terminology.
Specific comments:
1. 4-1. Reference to Table 13-1 and Figure 13-1? Could include in this section or consider
repeating same figures.
EPA FINAL RESPONSE: This information is included in Chapter 13 because it is central
to discussions in that chapter, whereas brief mention of it suffices in Chapter 4; we also
want to avoid the redundancy of repeating figures in multiple places. References to this
information in Chapter 4 have been clarified to make this point.
2. 4-2. Table 4.1 Data source?
EPA FINAL RESPONSE: Data sources are listed in the Notes section of the table.
3. 4-3. Units? T or Mg, metric ton=Mg
EPA FINAL RESPONSE: Units are listed in the Notes section of the table.
4. 4-5. Chemistry and associated risks? Or potential environmental risks?
EPA FINAL RESPONSE: The term "associated risks" is sufficient, as these risks
discussed are associated with the chemistry of the deposits.
Roy A. Stein, Ph.D.
Figure 4.1. While most all of the figures (and especially the maps) are much improved from the
first draft, Figure 4.1 needs some work. Perhaps the way to handle it is to divide it into multiple
figures, such that the reader could actually see the distribution of copper-deposit mining
throughout the world. I applaud the authors for including this deep background and context
for it helps us understand the "need" for a mine such as the Pebble.
EPA FINAL RESPONSE: This figure is meant to provide a very broad overview of where
porphyry copper deposits are located across the globe. Although splitting this figure into multiple
figures would allow the reader to more clearly distinguish individual deposits in specific regions,
this level of detail is not directly relevant to the assessment.
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Box 4.1 clarifies the multiple terms that caused our expert panel some angst. The terms now
seem to reflect a good deal of insight into how various practices will be used within the context
of copper mining at the Pebble facility. This improves the presentation dramatically.
EPA FINAL RESPONSE: No response required.
Page 4-10, Box 4.3. As I read through this box, I worried just a little about the multiple
jurisdictions involved in mine oversight, such as the Bureau of Land Management, the Alaskan
Department of Environmental Conservation, the Bureau of Indian Affairs (and all of the
associated tribal authorities), the State of Alaska, the Alaska Department of Fish and Game,
the Alaska Department of Natural Resources, Federal EPA, etc. I list these organizations here
as only a partial list of those agencies who have a "horse in the race". I worry about how they
will interact, the extent of their historical interactions, and just whether they, collectively, with
all of their different mandates and associated stakeholders, can present a cooperative, united
front in dealing with hard-rock mining in Alaska. Or might there be sufficient "turf' issues
that Pebble Corporation could take advantage of these differences to exploit these resources
without minding all of the regulations from all of these regulatory bodies. Text that might serve
to assure the reader that all is well (if this is the case) in this arena would be helpful. Or
perhaps some text to reflect on how these jurisdictional issues have been successfully handled
in other complex environmental projects.
EPA FINAL RESPONSE: We agree that these are important issues, but an evaluation of how
these multiple groups have or have not worked together effectively in the past is beyond the scope
of the current assessment.
Page 4-16 and beyond. I liked the discussion of TSF's, their construction, their limitations, etc.,
though this would have been the place that I would have liked to have seen some mention of the
groundwater issues in the Bristol Bay watershed and how communication among water bodies
(i.e., streams, rivers, wetlands, ponds, lakes, etc.) can compromise the usefulness of a TSF. Note
point 5a above.
EPA FINAL RESPONSE: Chapter 4 is meant to be more general discussion of mining practices,
and does not deal specifically with mining and potential effects resulting from hydrology in the
Bristol Bay region. These issues are discussed in Chapter 8, which evaluates potential leakage
from the TSF (e.g., see Section 8.1.1.1).
Page 4-17. Certainly, given these on-the-ground parameters, a fully lined TSF (even when there
will be multiple ones) should be required. The size of the first TSF to be built may cause some
to say that lining costs would be prohibitive, but I see no alternative given the hydrology of the
Bristol Bay Watershed. Having said all this, the comments about the length of life of geo-
membranes (for example) is short (perhaps as long as 600 years) compared to the required life
of the TSF before water can be released (30,000 years). Dry stack tailings may be the only
feasible alternative to TSF. Even so, because of the low grade of ore, the immense amount of
tailings, the "wet" nature of the environment, and the acid-producing nature of the tailings, dry
stacking may not be feasible either (and consider the immense area required for storage, see
Response Document. This is real conundrum for the siting of this mine. It might serve the
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reader well to emphasize this central limitation to the siting of this mine in the Bristol Bay
Watershed.
EPA FINAL RESPONSE: No response required.
Page 4-19.1 liked the final discussion on "Timeframes". This sets the reader up for later, more
in-depth, discussion of these issues. Nicely done.
EPA FINAL RESPONSE: No response required.
Chapter 5
John D. Stednick, Ph.D.
General comments:
This chapter presents the assessment endpoints. A broad discussion of salmon and fish
populations, wildlife, and viability of Alaskan Native cultures. Salmon and other fish resources
are the primary endpoint used.
EPA FINAL RESPONSE: No response required.
Specific comments:
1. 5-2. Line 9. 8watersheds. Correct typo.
EPA FINAL RESPONSE: Correction has been nuide in the final assessment.
2. 5-3. Data sources?
EPA FINAL RESPONSE: The table heading references Appendix B, which provides
references for all of the information in the table.
Roy A. Stein, Ph.D.
Pages 5-1 and 5-2. The justification for making salmon the primary endpoint was missing in
the original draft and now is nicely summarized and justified here.
EPA FINAL RESPONSE: No response required.
Table 5-1. The list of fishes present in the Bristol Bay watershed is far more complete and I
believe more accurate than in the first draft. Good work here.
EPA FINAL RESPONSE: No response required.
Figures 5-1 and 5-2 help the reader assess the distribution of salmon relative to the variety of
fisheries that occur in the watershed, though I must say that Figure 5-2 is a bit difficult to
interpret. Revision with attention to colors and symbols used might improve its message.
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Additional detail re one topic or another. This practice should be extended to all references to
appendices in the Main Report.
EPA FINAL RESPONSE: Figure 5-2 has been revised.
Table 5.3, Page 5-11, should include percentages for the numbers coming from each river
system for then the reader could gain some quantitative appreciation for the contribution of
the two river systems that will be impacted by the Pebble Mine.
EPA FINAL RESPONSE: Percentages have been added to the table.
Figures 5-3 to 5-11 nicely summarize what we know about the distribution of "salmonids" in
the Bristol Bay watershed. My only concern here is that given that the Nushagak and Kvichak
rivers provide 50% of the sockeye salmon harvest, can the EPA now say what proportion of
this harvest might be lost due to the construction of the mine? In other words, use these
numbers, percentages, etc., later in the report to provide context as to what will be lost if the
mine is built.
EPA FINAL RESPONSE: Available information does not allow the sort of analysis that the
comment suggests.
Chapter 6
John D. Stednick, Ph.D.
General comments: The mine scenarios are reasonable approximations of site activity. The text
reads in generalities, yet the tables and figures suggest a greater certainty given the numbers,
and significant figures used in tables. The conceptual models (Figure 6.12,13, and 14) are
excellent and need more references made to them.
EPA FINAL RESPONSE: Relevant sections of the conceptual models appear in Chapters 7
through 12.
Specific comments:
1. 6-10. Data source is Ghaffari et al., 2011?
EPA FINAL RESPONSE: Table 6-2 is a compilation of key parameter values that define
the assessment scenarios. Although some parameter values are based on Ghaffari et al.
(2011), most are derived from our scenario development decisions and associated analyses.
2. 6-11. Comparison of TSF height to human-made structures is anthropocentric. Suggest
omit such reference.
EPA FINAL RESPONSE: No change required. This figure is presented to give readers a
sense of the scale of the tailings dam heights. We chose national landmarks because these
are most familiar to readers.
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3. 6-12. Actual water quality in the tailings impoundments may differ significantly from what
is estimated (Appendix H). This may be true, however this is the best available
technology to estimate water quality changes and sentence should be reworded as the
approximation of leachate water quality and potential uncertainty in the test results as
applied to SW Alaska, rather uncertainty in method itself.
EPA FINAL RESPONSE: We disagree. A technique may be the best available, but that
does not mean it lacks uncertainty.
4. 6-13. Water treated to meet effluents. Good opportunity to explain receiving water
quality standards versus effluent discharge limits (permit conditions).
EPA FINAL RESPONSE: The distinction between water quality standards and effluent
discharge limits is not relevant in this section.
5. 6-15. Data sources for Table 6.3?
EPA FINAL RESPONSE: Table 6-3 provides a summary of water balance flows for the
three mine scenarios. Although some parameter values are extracted directly from
Ghaffari et al. (2011), most are derived from information in Ghaffari et al. (2011), our
scenario development decisions, and associated analyses.
Unclear why little change in TSF stored pore water in alternatives 2 and 3?
EPA FINAL RESPONSE: The water balance values in Table 6-3 are annual flows in
million mVyr. The production rates for the Pebble 2.0 and Pebble 6.5 scenarios are
similar; therefore, both the amounts of tailings produced annually and the volumes ofpore
water within those tailings are similar.
Similarly, the changes in total consumptive losses for 2 and 3.
EPA FINAL RESPONSE: The water balance values in Table 6-3 are annual flows in
million mVyr. The production rates for the Pebble 2.0 and Pebble 6.5 scenarios are similar,
therefore annual consumptive losses are similar.
Why the large increase in WWTP return flows between 2 and 3?
EPA FINAL RESPONSE: The Pebble 6.5 scenario captures much more water than the
Pebble 2.0 scenario (see Total Captured row in Table 6-3). Since the production rates for
the two scenarios are similar annual consumptive losses are similar, which leaves a larger
volume of water for treatment and release.
TSF pore water accounts for >90 percent of the mine operations water demand. How
was this conclusion made, I cannot reconstruct that value.
EPA FINAL RESPONSE: Table 6-3 lists all of the major consumptive losses. Comparing
the values for "Stored in TSF as pore water" to the values for "Total Consumptive Losses"
yields 95, 92, and 93% for the three mine size scenarios.
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6. 6-18. Pile Bay road reference? What road standards were applied and what was the
precipitation event? Or is this meant to be geographically significant?
EPA FINAL RESPONSE: This example is meant to be geographically significant; we now
refer to Figure 6-6 in the text.
7. 6-23. 6.2.2. Water balance [via streamflow and precipitation] and out [via surface
add ']' after precipitation
EPA FINAL RESPONSE: Change made in final assessment.
8. 6-24. first paragraph is unclear. How were streamflow values used to estimate net
precipitation? Area weighted average of net runoff of 840mm? Methodology is unclear.
EPA FINAL RESPONSE: Text was added to clarify how these calculations were made.
9. 6-25. Calculations of inflow agree closely to those provided by Ghaffari et al., 2011.
What were those methods and those results?
EPA FINAL RESPONSE: The methods used to calculate mine pit inflow are not described
in Ghaffari et al. (2011); however, we based our comparison on the reported average
annual pit dewatering pumping requirements reported in that document.
10. 6-26. How was the regression line fit to the data?
EPA FINAL RESPONSE: The line in Figure 6-7 is the approximation used in the
assessment. It is not a regression line to the data. The field data are shown to assist the
reader in evaluating the reasonableness of the assumed hydraulic conductivity profile and
to provide the available data should the reader choose to assess impacts using a different
profile. The approximation used in the assessment results in hydraulic conductivities
slightly higher than the mean of the data set, in order to not underestimate the amount of
water flowing into the mine pit.
11. 6-27. 6.2.2.3. Uncontrolled leachate escapes suggests a controlled leachate escape?
EPA FINAL RESPONSE: "Uncontrolled leachate escapes" implies that the escaped
leachate is not captured or controlled farther downgradient. Leachate which escapes into
groundwater and is later captured by collection wells or other means would be a controlled
leachate escape.
12. 6-35. References to premature mine closures? First paragraph under 6.3.5.
EPA FINAL RESPONSE: A citation is provided in this paragraph.
Roy A. Stein, Ph.D.
Page 6-15.1 find it a little hard to imagine that water could be treated and then discharged into
streams. Would the water quality of this discharge even begin to match the extremely high-
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quality water of extant streams prior to mine operation? This seems a little beyond the ability
of an on-site, waste-treatment facility. A bit more detail here to convince the reader this is even
possible would be valuable here.
EPA FINAL RESPONSE: Effluents are not required to match background water quality. They
need only meet the permit requirements, which are based on standards that in turn are based on
potential effects.
Page 6-31. The idea that post-closure TSF water would need to the treated for 100s to 1000s of
years begs the question just a little. Work done suggests that we are talking 10's of thousands
of years rather than these shorter time periods. One could certainly make the argument that
there is no real difference between these two lengths of time, simply because human institutions
do not last this long and the likelihood of TSF failure sometime during even the 100's of years
projected life is nearly inevitable, i.e., because no one is watching. Of course, having
contaminated water flow downstream via streams in the Bristol Bay Watershed will likely
make these streams uninhabitable for salmon for a very long time.
EPA FINAL RESPONSE: No response required.
Page 6-35. What incentives exist for any company to continue to invest in the monitoring and
maintenance of tailings storage facilities (but see Box 4.3 on Financial Assurance, for the nub of
the issue is dollars, isn't it?)? If well fields downstream of the TSF began to demonstrate that
contaminated water is flowing from the TSF, then why would the company work to eliminate
this source of contamination, save for an oversight organization such as a state or federal
regulatory institution? I think I get it, that there is to be financial assurances that will support
ongoing monitoring and appropriate maintenance post-closure. The greater risk seems to
evolve from "...chemical or tailings spills..." (Box 4.3, page 4-10) which these assurances do
not cover; how does one assure the public that these mishaps can be cleaned up?
EPA FINAL RESPONSE: We agree that these are important issues, but they are beyond the scope
of the assessment.
Pages 6-35 to 6-36.1 appreciate the discussion of financial assurances and how they have not
worked particularly well in the past. The commitment to making these sums actually reflect the
costs of remediation is critical to any permitting that might occur via the State of Alaska.
Should this point be made more explicitly?
EPA FINAL RESPONSE: A sentence has been added to the text to clarify this point.
Page 6-36, for example. Each time the authors came to a "what if' scenario, they then provided
the "then" statement, usually followed by an example from the real world. This is nicely
demonstrated on page 6-36 when they discuss a situation when a mine re-opens after being
closed for some time thus leading to a change in mining practices. The authors cite the example
of the Gibraltar Mine in British Columbia in which it was first permitted as a zero discharge
operation and then re-permitted allowing for treated water to be discharged. These real-world
examples lend credence to the "what if' scenarios and help the reader understand just what
might occur with the establishment of a mine such as Pebble.
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EPA FINAL RESPONSE: No response required.
Table 6-9 helped me understand EPA's regulatory role in applying the Clean Water Act to the
establishment of the Pebble Mine.
EPA FINAL RESPONSE: No response required.
The conceptual diagrams (Figures 6-12, 6-13, and 6-14) helped me visualize the interactions
that lead from mining impacts to salmon. They were clear and well put together.
EPA FINAL RESPONSE: No response required.
Chapter 7
John D. Stednick, Ph.D.
General comments: Chapter is mislabeled. This chapter addresses the stream habitat and flow
risks associated with routine operations of the mine.... It considers the unavoidable
environmental effects associated with the footprint of each mine scenario....
Flow should be changed to streamflow to avoid any confusion with energy flow, nutrient flow
or other flows. This chapter like other chapters has considerable quantitative information and
data in tables and figures that are not communicated in the text. Often the text is written in
generalities, yet there are many more specifics in the tables.
EPA FINAL RESPONSE: We have replaced flow with streamflow in all appropriate locations in
Chapter 7.
Specific comments:
1. 7-13. Given the numerous fish inventories for the study area, why are only 4 years of
data presented (2004-2008)? In general the number of counts was highest in 2008 and
thus had the higher inventory counts. Is this to be considered the baseline?
EPA FINAL RESPONSE: PLP's Environmental Baseline Document (PLP 2011) is one of
the foremost sources of baseline data for the mine study area, and it presents data from
2004 to 2008. We have added clarifying text explaining that 'baseline' data on fish
abundances will need to take high interannual variability within individual basins into
account, which will require a larger watershed and population context for any estimates of
salmon 'baseline'populations.
Figure 15.1-2 as cited in PLP 2011 should be repeated here. The significance of the
stream segments as opposed to watershed level inventories is not developed. Were these
differences included in the approximation of the unavoidable effects from routine mine
operations?
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EPA FINAL RESPONSE: Mention of PLP (2011) stream reaches is provided for reader
reference only, and the segmentation used in PLP (2011) was not used in this assessment.
Rather, we segmented streams in the study watersheds by existing streamflow gage sites,
and at tributary confluences if gage sites did not exist at those locations. Effects are
summarized at this scale for this analysis.
2. 7-15. The cumulative frequency plots are befuddling. I would like to see a better
presentation of this information, both in the text and graphically.
EPA FINAL RESPONSE: We have clarified presentation of these plots in the text.
3. 7-16. Separation or evaluation criteria are 5 and 10%, while flow separation criteria are
10 and 20% (7-51). Explain difference and cite appropriate references.
EPA FINAL RESPONSE: Only 10% and 20% criteria are discussed here, citing Richter et
al. (2012).
4. 7-27. Headwater streams. Can these be considered all streams with mean annual flows
<0.15 m3/sec?
EPA FINAL RESPONSE: That is how we are defining them in this assessment.
5. 7-28. Streamflow modification. Streamflows reduced by the loss of the percentage of the
expected area lost to each mien footprint and the water yield efficiency for that basin
(mVsec/km2)?
EPA FINAL RESPONSE: The comment is correct and text has been added to clarify.
6. 7-45. The annual hydrograph figure is monthly time steps. As part of the site
characterization (Chapter 3), daily hydrographs would be more illustrative of
hydrologic responses to precipitation events as snow, rain, or rain on snow.
EPA FINAL RESPONSE: Daily data do of course provide additional detail, but for
general patterns of annual regimes monthly data meet our objective ofproviding a broad-
scale perspective in Chapter 3.
7. 7-55. Maintaining the connectivity of the stream to off-channel habitats is important;
however the suggestion that the WWTP discharge could be used as compensatory
mitigation may not be the best mitigation. WWTP discharge concentrations need to be
evaluated for toxicity of fish species and life stage. WWTP discharges are finite and
cannot be used to address all lost off-channel habitat connectivity.
EPA FINAL RESPONSE: WWTP effluents are assumed to meet Federal water quality
criteria and State standards. As discussed in Chapter 8, there is some uncertainty about
how protective that would be. The statement that WWTPflows would not fully mitigate lost
stream and wetland flows is correct and that point is made in the chapter.
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8. 7-60. Why the detailed comparison between the EPA results and those from Wobus et
al., 2012? Other EPA efforts in earlier chapters were not compared to other scientific
works. The Wobus work cited is an unpublished review draft from a consulting
company.
EPA FINAL RESPONSE: Validation against an independent analysis, particularly on that
used a different modeling approach, is an important practice in risk assessment. However,
references to the Wobus et al.2012 results have been removed from the final assessment.
Roy A. Stein, Ph.D.
In Box 7.1, the authors argue that stream lengths and wetland area reflect a lower bound on
the estimate lost to the footprint of the mine. In turn, the estimates of the number of salmonids
in these same streams are likely underestimated by 50%. Hence, this suggests that the number
of salmonids eliminated by the footprint of the mine is likely 4X what is reported. I agree. To
remedy these underestimates, the authors should revise both the Executive Summery and the
Abstract, pointing out that these are either lower bounds to these estimates or are increased by
some metric to better reflect true abundance. Or, at the very least, point out in these sections
that the numbers reported are substantial underestimates of what likely is out there.
EPA FINAL RESPONSE: That point has been added to the Executive Sunmiaiy.
Because it is small headwater streams that are eliminated by the mine footprints, it would be
appropriate to argue that Coho Salmon and Dolly Varden are differentially affected simply
because they spawn in these smaller streams (page 7-22). Is there any way this can be better
quantified?
EPA FINAL RESPONSE: We have added a text reference to Table 7-8, highlighting that coho
salmon occupy the highest proportion of documented A WC streams in the mine scenario
watersheds. We also acknowledge that the distribution of anadrontous Dolly Varden is not well
known but likely extensive, and habitat analysis suggests much of the mine scenario watershed
streams would be suitable for this species.
In Table 7-5, Dolly Varden are not mentioned; is there a reason for this? Do we simply not
know the distribution of Dolly Varden in these streams (see page 7-26)?
EPA FINAL RESPONSE: See response to previous comment. The distribution of anadrontous
Dolly Varden is poorly documented in the study area.
Pages 7-27 and 7-28. The difference between the first draft of this report and this second draft
is dramatically demonstrated by the number of peer-reviewed references cited on pages 7-27
and 7-28 when the authors are discussing general salmonid ecology relevant to the Bristol Bay
Watershed. The text becomes so much more convincing when most all statements re the
ecology of these species are supported by multiple literature citations.
EPA FINAL RESPONSE: No response required.
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Chapter 8
John D. Stednick, Ph.D.
General Comments: A broad approach to water collection and treatment. Toxicity analysis
based on harness and biological ligand model water quality standards are presents and
discussed. Copper is the primary metal of concern, but other metal toxicities are evaluated,
most often as a toxicity quotient. The tables and figures contain a large amount of quantitative
data, yet the writing, like so many chapters tends to be qualitative. The text could be improved
by incorporating more of the quantitative results.
EPA FINAL RESPONSE: No response required.
Specific comments:
1. 8-1. Suggest better identifying water quality standards as being promulgated, and water
quality criteria as recommendations. Discuss the role of the state government and state-
based standards as compared to federal recommendations of water quality criteria.
Standard exceedance may result in civil or criminal penalties, criteria exceedance do
not.
EPA FINAL RESPONSE: A discussion of the distinction between standards and criteria
and its implications has been added to Section 8.1.
2. 8-11. First paragraph discusses the range of hydraulic conductivities and suggestion of
bedrock fractures for groundwater conveyance. The second paragraph then states that
the risk assessment considered no flow below 100m. Why the inconsistency?
The water volumes should be 106—super position the 6.
EPA FINAL RESPONSE: The exponents have been corrected. The available hydraulic
conductivity data (Ghaffari et al. 2011) show a great deal of scatter, spanning about four
orders of magnitude. Our analysis used a simple geometry bounded at 100 m below the
base of the TSF. Although there may be additional downward and lateral flow below this
boundary, the combination of lower hydraulic conductivity, lower gradients, and longer
flow paths would affect the calculated flow by much, much less than the amount of
variation in the hydraulic conductivity data. Although Chapter 8 says "the presence of
fractured bedrock allows for localized discontinuities in the rate of groundwater movement
that can greatly influence overall groundwater conveyance," the available evidence does
not suggest that any such localized features are prevalent.
3. 8-12. It is unclear where the estimates of 84% of PAG and 84% of waste rock leachate
would be captured by the pit and wells of Pebble 2.0. This represents a significant
volume of water moving into the groundwater system, coupled with the mine waste
chemistry; this represents a significant environmental risk already.
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EPA FINAL RESPONSE: These values are based on the assumed spatial distributions of
the waste rock and the leachate capture efficiencies. The proportions of the waste rock
types within the cone of depression for the pit are based on the layout in the three
scenarios. The example referred to in the comment is based on the Pebble 2.0 scenario.
The assumption that 100% of the leachate within the cone of depression would be captured
is somewhat conservative. It is likely that a little would flow away from the pit due to
features such as cracks that form preferred flow paths relative to the overall gradient
toward the pit. The assumption that 50% of the rock outside the cone of depression would
be captured by wells is a professional judgment. It cannot be estimated with real
confidence because of the lack of specific information on the detailed geology and well
design. The resulting estimate that 84% of PAG leachate and 82% of total waste rock
leachate would be captured by the pit and the wells for the Pebble 2.0 scenario is
reasonable but uncertain.
The estimated pit wall leachate compared to the mean tertiary NAG waste rock as
percentages is confusing. The percentage values suggest that numeric data are
available, thus a tabular comparison of these numbers would be much more
informative.
EPA FINAL RESPONSE: In the final assessment percentages have been changed to
concentrations as suggested and their derivation is explained.
4. 8-18. Table 8.9 Awkward format in presentation of contaminants of concern, i.e.
323/338/590.
EPA FINAL RESPONSE: This table has been revised, so that each scenario is listed in a
separate column.
5. 8-25. Table 8.10. More water quality data! The coefficient of variation is helpful, but I
suggest the standard deviation may be a better measure of central tendency. Would like
to see these data in Chapter 3. Description of region.
EPA FINAL RESPONSE: Both coefficient of variation and standard deviation are
measures of the dispersion, not central tendency. The coefficient of variation normalizes
for the mean so it is better for comparing variables.
Chapter 3 focuses on the entire Nushagak and Kvichak River watersheds, for which there
is not much detailed water quality information. The April 2013 draft of the assessment
included data from mine scenario watersheds in both Chapter 3 and Chapter 8 (e.g., Table
3-4 and Table 8-10 contained much of the same information). In the final assessment, the
water quality section has been removed from Chapter 3 to better reflect the overall
structure of the assessment, in that Chapters 3 through 5 consider broader spatial scales.
6. 8-43. Table 8.18 is empty (at least in my version of the assessment).
EPA FINAL RESPONSE: Table 8-18 does contain data, so this may have been a
temporary printing glitch.
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7. 8-52. Section 8.2.3.7. The analogous mine discussion could be expanded. It appears to be
an extensive data base. Could the mines be separated by geography and mine age, to
glean more information of the efficiency and effectiveness of mine operations on
environmental quality. The assessment takes issue with the comparison of the Pebble
Mine to the Fraser River (Box 8.4), but does not offer a mine alternative.
EPA FINAL RESPONSE: The analogous mines discussion no longer includes the Kuipers
et al. review. The remaining Earthworks review includes only currently operating mines.
The Fraser River was the only potential analogue of a large watershed with both a
significant salmon fishery and modern copper mines.
8. 8-60. These differences of interpretation of data can be an important source of
uncertainty in environmental modeling.
Under the uncertainties section, a discussion is presented comparing the EPA risk
assessment estimate of copper concentrations of waster rock leachate to results obtained
by another study (Wobus et al, 2012) that is a draft report from a consulting company.
Why the comparison? I suspect that there are other reports with other results of waste
rock leachate chemistries. I reviewed the Wobus report earlier. In my estimation there
are 3 major issues in that report: 1) the use of a stable copper release rate is an
oversimplification of the chemical dynamics that occur in the tailings/waste rock. The
physical environment in Bristol Bay will significantly affect the chemical weathering
processes and rates; 2) since the humidity cell test did not follow ASTM procedures, the
leachate concentrations was increased by 1 standard deviation. No justification for this
inflation was provided; 3) The report inseparably links copper concentrations to
streamflow rates by stating that copper was treated as a conservative constituent, which
is incorrect given the water quality in the study area and hence speciation of copper.
Their report stated that the addition of 1 standard deviation to the copper
concentration was to compensate for not following ASTM procedures, not because the
high values and potential episodic exposures would be underrepresented by the mean.
Why does EPA feel that they have to defend their results to this unpublished consulting
report? Same comment as above in Chapter 7.
EPA FINAL RESPONSE: That statement and all other references to Wobus et al. (2012)
have been deleted from the final assessment.
Roy A. Stein, Ph.D.
Page 8-3, Figure 8-1.1 liked this figure and most all that followed in proceeding chapters for
they aided in setting the stage for the discussion to follow.
EPA FINAL RESPONSE: No response required.
Page 8-4. The argument that during mine operations, 10-49 million m3 of treated water would
be discharged per year (Table 6-3). Though there is concern about the quality of the water
overall as well as the quality of this water as influenced by accidents, poorly functioning
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equipment, environmental conditions that exceed the specifications of the various wells, etc.,
there is real concern about the waste leachate and how it might directly influence salmon
populations. I worry that the metals, acid, and sediments in this released water during mine
operations will likely cause major impacts on the extant salmon populations (with the most
extreme being direct mortality on through less extreme impacts on growth, physiology,
migration patterns, distribution throughout the watershed, etc., etc.). Then, the impact of this
waste leachate post-closure will undoubtedly be dramatic if not in the first 50 years, most
certainly in years beyond the time we (as the mine operators, the State of Alaska, the EPA,
Native Alaskans, Commercial Fishers, etc.) are watching, i.e., monitoring, assessing, and
maintaining water-treatment facilities.
EPA FINAL RESPONSE: No response required.
Page 8-11. In the last sentence of the first paragraph, the comment about groundwater
conveyances suggests that toxicants can be transported just about anywhere in the watersheds
of the two affected rivers. This feature of the landscape, mentioned explicitly elsewhere as well,
makes the placement of the mine here in the Bristol Bay Watershed suspect. And, of course, it
is this very groundwater that supports the reproduction of all of the salmonids in the basin.
EPA FINAL RESPONSE: No response required.
Page 8-11. Given our inability to predict where surface water, collected as wastewater, might
flow (third paragraph on this page) via the groundwater makes this an even more intractable
issue when one is trying to protect water quality in the Bristol Bay Watershed.
EPA FINAL RESPONSE: No response required.
Page 8-11. Combine the above two points with the water chemistry of the natural waters of
Bristol Bay Watershed (i.e., extremely high quality but not well-buffered) and one has the
makings of a dramatic negative impact on the salmonids upon siting of this copper mine. I
would like to see an increased emphasis on these aspects of the potential effects of the Pebble
Mine.
EPA FINAL RESPONSE: We believe that Chapter 8 already emphasizes these points sufficiently.
Page 8-20. Has there truly been any thought or consideration given to a reverse osmosis
treatment of wastewater at this site?
EPA FINAL RESPONSE: Yes, it was suggested as a likely technology by an official of the Pebble
Limited Partnership.
Page 8-21. Given that mines continue to be operated even when those responsible for
operations know they are not meeting water quality criteria for wastewater, what assurances
do we have from Pebble Limited that their operators will differ from the past (i.e., in a good
way)?
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EPA FINAL RESPONSE: The Pebble Limited Partnership ownership and management have
stated that they will be responsible operators.
Page 8-31. And even given that standards now in place for the quality of water that is
discharged from the site during operations, these standards appear not to protect
macroinvertebrates, food for young salmon. Disrupting the food supply will indeed
compromise salmonid success.
Table 8.22, for example. As the mine grows larger and into the economies of scale that the
company requires, the impact on water quality and ergo the fish becomes more and more
dramatic (i.e., more fish kills, etc.)...and this is during normal operations without any
infrastructure failures. Can this truly be tolerated and a permit issued? Sadly, the monitoring
of ongoing operations at extant copper mines has not been done (see first partial paragraph on
page 8-53); so then how can we anticipate the ecological effects of the Pebble Mine even under
the best of conditions?
EPA FINAL RESPONSE: The assessment anticipates potential ecological effects as well as
existing information allow.
Page 8-55. More than 500 million salmonids will be affected by the Pebble effluent; doesn't this
tell the story in one sentence. Impacts on resident and anadromous salmonids will be negative,
large, and long-term.
EPA FINAL RESPONSE: No response required.
Page 8-63. Changes in stream temperatures mean a disruption in the various life history
characteristics dependent on temperature, such as growth, survival, migration, movement, etc.
Hence, negative impacts on salmonids will indeed be huge, largely negating the portfolio
characteristics of these species (down to specific life histories within populations) that have
allowed these salmon to be so successful over their history.
EPA FINAL RESPONSE: No response required.
Page 8-65. Actually, we know quite a lot about how temperature influences salmonid success.
For example, quantitative energetic models have been built and tested in the lab and field.
While we may not have specific information on every species in the watershed, the fact remains
that we have a pretty good conceptual framework backed up by solid work to help us
understand the impact of temperature on salmonid success.
EPA FINAL RESPONSE: Text has been added to acknowledge that much is known about
bioenergetics, but that much remains poorly understood with regard to how these species will
respond to changes to thermal regimes, particularly with regard to sublethal effects, behavior,
adaptation, effects of fitness on the population, and other issues.
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Chapter 9
John D. Stednick, Ph.D.
General comments:
Flood simulation using the SCS runoff method. Significant lack of detail in streamflow
generation assumptions and results. Sediment pulse model simplified TSF release of sediment
with HEC-RAS modeling of deposition downstream.
EPA FINAL RESPONSE: Flood simulation using the SCS runoff method is no longer included in
this analysis. We acknowledge that the HEC-RAS application provides a very simplified approach
to sediment deposition.
Specific comments:
1. 9-5. Another excellent conceptual model of potential pathways linking TSF failure to
salmonid risk, but the text does not parallel nor address all pathways.
EPA FINAL RESPONSE: We acknowledge in the text that not all pathways are fully
addressed.
2. 9-13. flooding to create the overtopping is 2.5% of the total peak flow in the Pebble 0.25
failure and 0.1% of the total peak flow in the Pebble 2.0 failure. How were these
numbers generated? What assumptions made? The reader cannot make the same
conclusion based on the materials presented.
EPA FINAL RESPONSE: In the final assessment, flooding to generate overtopping is no
longer simulated.
3. 9-14. Chapter 3 needs more data presentation of meteorological conditions. Maps of
annual precipitation and plots of monthly hydrographs do little to prepare the reader to
understand this chapter for a rain driven storm hydrograph. The probable maximum
precipitation of 356mm (14 inches) is for a 24 hour event of presumably a 100 year
recurrence interval. Checking the cited reference (Miller 1963), such a storm depth was
significantly larger than any found for the study area. Please explain the difference.
How much precipitation data re available from the study site, and can these data be
used for comparative purposes on Technical Paper No. 47 (Miller, 1963) for more
frequent precipitation events. Defend the selection of a Type I precipitation
distribution. When do rain storms occur and are they over wet soils? How does
permafrost and discontinuous frozen soils affect the calculation of curve numbers? We
read later that the example has a watershed area of 14 km2. Where are the other data?
Channel slope, time to concentrate, Manning's n etc. The storm event cannot be
reproduced without these data.
EPA FINAL RESPONSE: See response to previous comment.
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4. Why no comparison to flood events based on regression equations? Estimating the
Magnitude and Frequency of Peak Streamflows for Ungaged Sites on Streams in Alaska
and Conterminous Basins in Canada. Janet H. Curran, David F. Meyer, and Gary D.
Tasker. 2003.
EPA FINAL RESPONSE: See response to previous comment
5. 9-15 .producing a peak flood immediately downstream of the dam of11,637 m3/sec
for the Pebble 0.25...A frightening event, nonetheless how was this peak flow
determined? A comparison of a sediment laden pulse event versus the 'modest' peak
flow event. Watch significant figures.
EPA FINAL RESPONSE: The peak flow event (Omax) is generated for each profile using
the HEC-RAS modeling approach (described in Box 9-4). A probable maximum flood
(PMF) is no longer used as the trigger event. However, the PMF did not contribute
substantially to the flood wave. In the final assessment, we have revised the HEC-RAS
model and use a 2-hour time to full failure instead of a 30-min time to full failure. The 30-
minute failure scenario was within the limits of observed events but at the faster end of the
range. The 2-hour failure falls more in the middle of this range. It also reduces the flood
wave peak from 11,637 mVs to 5,270 mVs for the Pebble 0.25 scenario. The peak flow is
calculated by balancing the energy between upstream and downstream sections in the RAS
model. The energy equations determine the velocity of the flow as is passes through the
cross-section area; discharge is determined based on the calculated water surface,
available conveyance area, and velocity.
A paragraph explaining the use of significant figures has been added to Section 2.1.1.
6. 9-34 to 9-48. This section of the chapter presents important materials, but the quality of
writing needs improvement. I had to reread several sections to understand the point of
each section. The sections do not flow in a logical sequence and the coverage quality is
variable.
EPA FINAL RESPONSE: This section has been edited.
Roy A. Stein, Ph.D.
Page 9-1. Not only would this failure eliminate spawning grounds and rearing habitat forever,
the method for remediation (and even the wisdom of any sort of remediation, given constraints)
is not immediately apparent. Streams may well be too small to float a dredge and because this
whole area is road-less with long winters and innumerable streams, rivers and wetlands,
actually getting equipment to these remote sites may be near impossible. I encourage the
authors to emphasize these points.
EPA FINAL RESPONSE: This issue is addressed in the introductory section (Section 9.1) and at
greater length in Section 9.3.3.
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Page 9-3. A failure of this sort is not simply conjecture for these failures have occurred the
world over. And these failures, while dramatic, long-lasting, and impactful, reflect dams that
are less than half the height of the planned Pebble TSF at its largest footprint. Some emphasis
on this point would be useful.
EPA FINAL RESPONSE: The scale of the proposed TSFs for the Pebble 2.0 and Pebble 6.5
scenarios are large by any standard. Not only would the rockfill dants be among the highest in the
world, the volume of tailings in the TSFs dwarfs the amount held in most other tailings
impoundments. Rico et al. (2008) reports released tailings volume data for 29 tailings dam
failures. The largest release reported is 9 million m3. A release of 20% of the Pebble 0.25 TSF 1
would involve 32 million m3 and a release of 20% of the Pebble 2.0 TSF 1 would involve 235
million m3 of tailings. These points are made throughout the assessment.
Pages 9-3 and 9-4. One piece of good news re the "in perpetuity" nature of minding the TFS is
that these facilities seem to stabilize through time, resulting in fewer failures as compared to
active TSFs. On the other hand, what is the longest period that has been monitored for a dam
post-operation. Likely, this would be less than 100 years and prior to these dams being built,
engineering standards would no longer be applicable. Rather much of a conundrum, wouldn't
you say?
EPA FINAL RESPONSE: The assessment states that waste storage facilities have only been in
existence for roughly 50 years.
Table 9-2, Page 9-8. The classification scheme Alaska uses to determine the amount of
engineering that must be done according to the risk of losing lives seems a bit inappropriate in
this context. The risk here to the livelihood of individuals is paramount and I worry that
Alaska's scheme may not protect the salmonids, the Native Alaskan subsistence way of life, and
the tremendously productive Bristol Bay commercial and sport fisheries.
EPA FINAL RESPONSE: No response required
Page 9-31. TSF failure is postulated to reduce the Chinook Salmon run by 60% and this run is
one that produces a large proportion of the Chinook on the West Coast, and is the one least
influenced (at present) by habitat loss, etc. Protecting this run is paramount for Alaska, the
nation, and the world.
EPA FINAL RESPONSE: No response required
Box 9-6, Page 9-35.1 like this box and many of the others that provided brief synopses re case
histories applicable to the Pebble Mine. I appreciate the comparisons and caveats. In addition,
based on results from other mines sites, it is clear that tailings toxicants, traveling downstream,
not only reside in the stream for decades to hundreds of years, they also have been documented
to move 210 km in one system. Because nearly all of these TSFs are smaller than the Pebble
one, impacts are even likely to exceed these measured effects. Making this point more explicitly
would enhance the message.
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EPA FINAL RESPONSE: We do not agree that effects are necessarily likely to exceed those of
past cases. Although the TSFs were smaller, the tailings often had higher nietal content and spills
were not remediated for decades.
Table 9-11, Page 9-50.1 liked the attempt at weighing the different lines of evidence, then
drawing conclusions based on best scientific judgment. This "weighing of evidence" helps the
reader understand the limitations of the data while simultaneously being able to draw what
valid conclusions one might draw from such an analysis.
EPA FINAL RESPONSE: No response required.
Chapter 10
John D. Stednick, Ph.D.
General comments: A thorough presentation of the risks associated with the development and
use of a transportation corridor as related to road corridor encroachment on wetlands,
streams, and riparian areas road drainage, road runoff, as related to fish habitat and fish
behavior.
EPA FINAL RESPONSE: No response required.
Specific comments: As commented on the first external review draft, the failure rate of culverts
of 47 % seems high and may be the result of using older references. A recent best management
practices audit here showed that culverts and bridge crossings were over 95% effective in
maintaining water quality. The reference to ADOT could be expanded to include more site
specific standards.
EPA FINAL RESPONSE: In addition to maintaining water quality, stream crossings must also
allow fish passage. The culvert frequencies cited in the assessment are from modern roads. The
ADOT reference mentioned by the commenter is the Alaska Highway Drainage Manual, which
contains standard hydraulic design criteria for the State of Alaska. Addressing site-specific
standards is beyond the scope of this assessment.
1. 10-9. Cumulative frequency of stream channel lengths...
I think this figure will leave many readers confused. Even with colored lines, the take
home message is unclear. The text does little to support the figure as well. The mean
annual flow 'breakpoints' need to be presented and clarified earlier. The reach gradient
breakpoints were not identified earlier, and finally the 5% flood plain potential is
arbitrary. Nonetheless, when and where are their significant differences? Not in MAF.
Were stream gradients? The tables present more detailed data, or numeric values that
can be bettered compared, suggest the writing team reevaluate the 'cumulative
frequency figures'.
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EPA FINAL RESPONSE: We have added clarification of these plots in the text. The
breakpoints in this figure were defined in Chapter 3, and we now refer back to this text in
Chapter 10. We believe that the cumulative frequency figures are useful because they
illustrate how stream characteristics in the region vary across geographic scales (i.e.,
across the entire Bristol Bay watershed vs. the scales evaluated in the assessment's risk
analyses). For example, in Chapter 10 this figure graphically supports the statement that
transportation corridor streams tend to be steeper and more floodplain-prone than streams
across the Nushagak and Kvichak River watersheds.
Roy A. Stein, Ph.D.
Figure 10-1, Page 10-3 was a little difficult to interpret, given its scale and the colors (where are
the ponds, for example). So, I much appreciated the next figure (Figure 10-2) that zoomed in on
some critical areas and these maps were far easier to interpret and to gain some perspective on
the impact of this road on the aquatic environment.
EPA FINAL RESPONSE: No response required.
Page 10-8. The work demonstrating divergences in populations in close proximity (Quinn et al.,
2012) suggest that the road indeed will have a major impact if any migratory routes are
compromised, if spills occur that prevent animals from moving via their historical pathways,
etc. Making this point explicit would improve the document.
EPA FINAL RESPONSE: We have added text noting the potential effect of migratory barriers
and stream habitat degradation on genetically diverse sockeye populations in the study area to
Section 10.4.
Figure 10-5, Page 10-11 was a useful one demonstrating the overlap between the road and
Sockeye Salmon. This is a much improved presentation from the first draft.
EPA FINAL RESPONSE: No response required.
Page 10-26. Given the very high failure rate of culverts, would it make sense to install more
bridges or more arch-only culverts to protect salmon populations? It just seems that traditional
culverts are a poor alternative to bridges and arched culverts.
EPA FINAL RESPONSE: Bridges would generally have less impact to salmon than culverts, but
can result in the loss of long riparian side channels if they do not span the entire floodplain. The
actual decision as to what type of structure (bridge vs. culvert) would be constructed at each
crossing would be made by industry engineers in consultation with state permitting staff.
A number of culvert types may be used along the proposed transportation corridor, and it is not in
EPA's purview to suggest which ones should be used However, culvert design approaches
specified in the Memorandum of Agreement between theADF&G and theADOT are described in
Box 10-2 of the assessment.
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General Point. Throughout the text (see first complete paragraph on page 10-37 dealing with
what we might expect with invasive species coming to the environment with the building of the
road, as just one example), both in this chapter and others, the authors have demonstrated a
knowledge of the recent literature which is used throughout to justify their assumptions,
confidence, and risks. This allowed me to appreciate and evaluate with a more discerning eye
the product of this ecological assessment. Nice work.
EPA FINAL RESPONSE: No response required.
Calculations of dust production on pages 10-35 and 10-36 reflect a nice quantitative, with
appropriate caveats, assessment, demonstrating that dust could have a real impact on the
salmonid streams in close proximity to the road.
EPA FINAL RESPONSE: No response required.
Pages 10-40 to 10-42.1 liked the uncertainty section that dealt with the transportation corridor;
issues that I did not anticipate were covered nicely.
EPA FINAL RESPONSE: No response required.
Chapter 11
John D. Stednick, Ph.D.
General comments: A thorough presentation of the estimation of risks from pipeline failure
and associated environmental risks as related to concentrate and diesel in the aquatic
environment.
EPA FINAL RESPONSE: No response required.
Specific comments: None.
EPA FINAL RESPONSE: No response required.
Roy A. Stein, Ph.D.
Pages 11-2 to 11-4. These conceptual figures are useful (throughout the document) to help the
reader envision the majority of the interactions within the context of pipeline failures.
EPA FINAL RESPONSE: No response required.
Page 11-5.1 liked how the authors quantitatively developed their best estimates for the
probability of pipeline failures, based on similar situations with other mines and with other
pipelines. In turn, the authors typically laid out the caveats re the comparative nature of the
data: was the pipeline similar, did it exist in a similar environment, was it designed with Best
Management Practices in mind, were there other issues that might allow estimates of pipeline
failure to be higher or lower than what might be expected at the Pebble Mine? This sort of
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quantitative, transparent analysis gives the reader faith that the EPA has no hidden agenda, no
ax to grind, and no previously decided-upon conclusions. I applaud the authors for these
revisions.
EPA FINAL RESPONSE: No response required.
Page 11-6. The whole idea of human mistakes or accidents is intriguing for this suggests that no
matter how good the infrastructure might be, we still will have human error and it looks to be
quite a prevalent cause of failures in the case histories of mines presented. What I reflected
upon was how one can incorporate this knowledge into current measures of pipeline failures.
The authors did not separate human error from infrastructure failure and that indeed might
be quite a useful exercise. Indeed, how do mining companies work to reduce this source of
failure? Training? A safety-first attitude that includes strong provisions for reinforcing the
idea of doing things "right" in the field, even when time is of utmost importance. And I guess it
would be modification of worker mind-set that would replace "time" as the most important
driver to "infrastructure protection" as the most important one. I would very much like to see
what Northern Dynasty has to say about this issue. Finally, I would have liked to have seen a
discussion of "human error" in all of the sections dealing with failure. Is this as prominent an
issue with regard to the TSF as it is with pipelines?
EPA FINAL RESPONSE: The assessment does include a discussion of an example of failure to
maintain adequate freeboard resulting in overtopping of a tailings dam at the Nixon Fork Mine,
but not a human error that actually caused a dam to fail.
Page 11-15. Though I have seen just a few typos, there is one on page 11-15 that requires
correcting...next to the last paragraph reports 14,00 gallons when it is likely that this number
should be 14,000 gallons. See also a typo in the first paragraph on page 11-26. See page 11-30,
last complete paragraph on the page.
EPA FINAL RESPONSE: Noted typos have been corrected in the final assessment.
Page 11-18. During the course of this chapter, the authors make the point that release of
contaminants into the environment would be more amenable to mitigation at low flows rather
high ones. True, but the authors fail to point out that "dilution" will be more of a factor at high
flows and thereby may reduce or even negate contaminant impacts. Some recognition of this in
the text would improve the presentation.
EPA FINAL RESPONSE: Dilution in high flows is relevant to the aqueous component of the
spill. This dilution is discussed, but that phase would not be recovered or otherwise mitigated. The
solid phase might be recovered, but its toxic effects would occur over the long term and after it has
deposited rather than during the initial transport, so reduced toxicity due to high initial flow
volume is largely irrelevant.
Page 11-19, second bullet point at top of page. Why choose the 5-min spill duration and not the
more common, 11.5 min, as suggested by O'Brien's Response Management publication? It
certainly seems this would be more defensible than arguing as the authors do, that their
estimates may underestimate the impact of spills on the environment.
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EPA FINAL RESPONSE: The 5-minute duration was judged to be reasonable but, as noted, it
may be optimistic. This is highlighted as an uncertainty in Section 11.3.5.
Page 11-20. The whole idea of diesel fuel being so variable relative to its constituents bothered
me some. If this is the case, can no one in a position to review permits judge its composition and
therefore judge its potential impact on the environment? This section was unsatisfying to me re
how a failure of this pipeline might influence nearby wetlands, streams, rivers, ponds, and
lakes.
EPA FINAL RESPONSE: If a mine is developed, the source of diesel could be identified and even
used in toxicity tests; however, this information is not currently available.
Table 11-10, Page 11-3. Though I liked tables of this sort, I became just a little confused by the
nomenclature, what with a "positive" response having negative consequences. I think I did get
it figured out and I may even now understand your usage here, I worry a little about how a lay
audience or even Northern Dynasty will interpret this text. One example of this confusion can
be found on page 11-29, last paragraph. Note the quote from the text, "Overall, the available
lines of evidence for effects of a diesel spill are positive for the occurrence of acute toxic effects
(Table 11-10)." Really? I trust the authors get my concern here.
EPA FINAL RESPONSE: Positive evidence for a hypothesis does not imply a positive outcome for
the environment. The quoted sentence and a similar sentence concerning the copper concentrate
have been edited using the term supportive in place of positive.
General Point. One piece of information that I would like to see added to this draft is some sort
of time period for recovery of the negative impacts of a spill. Most studies (being Masters
theses) typically study these impacts for 1-2 years and by this time, 80% or so of the
macroinvertebrates are back (but maybe not the diversity) and fish have recovered but not
completely. If we think about extrapolating these studies out (certainly there must be one that
goes beyond just a year or two), then when would we expect full recovery? This is an extremely
important point and may provide insight into longer-term impacts of a spill when the effects of
the contaminants are relatively short-lived (i.e., much, much, much shorter than what is
predicted for a TSF breach, for example). Contrasting impacts of pipeline failure with other
infrastructure failures would lend more credence to the work of the EPA authors.
EPA FINAL RESPONSE: The characterization of recovery (Section 11.5.4) has been rewritten to
incorporate this point.
Chapter 12
John D. Stednick, Ph.D.
General comments. The primary discussion is the indirect effects on wildlife and Native
cultures that are fish-mediated. A change in the title to better reflect the chapter purpose?
Another chapter with good conceptual models (Figures 12.1 and 12.2 that are not followed up
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in the text. In my estimation, the figures are excellent, and deserve more coverage in the text
than currently afforded (often none).
EPA FINAL RESPONSE: The Chapter 12 text now includes references to both conceptual
models.
Specific comments:
1. 12-5.1 am certain there are better references to bio-concentration factors in fish than
an unpublished report.
EPA FINAL RESPONSE: EPA performed a lot of high quality research in the early 1980s
to support the derivation of the National Ambient Water Quality Criteria that did not get
published. As explained in the text, the bioconcentration factor was used because it was the
highest value. Using it allowed us to say that, even with that high value, dietary copper
does not appear to pose a risk to wildlife.
Roy A. Stein, Ph.D.
Page 12-1. The title of the chapter seems to me to be incomplete, in other words, I think the title
should be "Fish-mediated effects on Native Alaskan Culture". This better encompasses the
content of the chapter.
EPA FINAL RESPONSE: Chapter 12 also deals with fish-mediated effects on wildlife; no change
required.
Page 12-1.1 would like the authors to add about a page of text to set the stage for Native
Alaskans, e.g., a culture that is 4,000 years old, a sustainable culture dependent on subsistence
harvesting ( different than a one-time exploitation by a mining company), the fact that the jobs
generated will only last for a generation or a generation and one half...far less than 100 years.
This text would then set the stage for the chapter and better provide context for this
examination as well as the purpose of this chapter (as stated on page 12-1).
EPA FINAL RESPONSE: A statement confirming that the salmon resource has supported Alaska
Native cultures for 4,000 years has been added to Chapter 5. Chapter 12 recognizes that jobs
related to large-scale mining are time-limited.
Page 12-6. Throughout this chapter I noted the many "trade-offs" that are inherent in the
establishment of a mine of this type and size. Cash economy versus subsistence, short-term
rewards versus long-term ones, culture-enhanced activities versus culture-negating ones, split-
time activities (i.e., part-time work) versus full-time subsistence activities, etc. Some recognition
of this might improve the message being sent with this chapter.
EPA FINAL RESPONSE: Chapter 12 has been revised to more clearly discuss the trade-offs
between increased opportunities for wage employment and the subsistence way of life.
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Page 12-9. The idea that the mine will come in, extract valuable minerals, and then leave occurs
throughout but I think it is insufficiently emphasized that the physical degradation to the
environment stays...typically in perpetuity. Yes, the text makes this point but it is somewhat
buried, in my view. Can the authors increase its impact and thereby its visibility?
EPA FINAL RESPONSE: We recognize throughout the assessment that nuiny of the
environmental changes would be permanent (e.g., Sections 12.2.1,12.2.3,12.12.5). However, even
environmental changes that are not permanent may result in permanent cultural change. A
statement has been added to Section 12.2.5 to recognize that permanent cultural change can result
from temporary environmental disruption.
Page 12-10, first complete paragraph. The fact that small changes to movement of terrestrial
organisms can have dramatic impacts on the Native Alaskan culture is a good one. Like the
previous point, I would like a bit more explanation as well as more detail, coupled with a
historical example or two. This information would increase the power of this paragraph.
Page 12-11 and 12-12. These are powerful arguments for the whole idea of job enticement for
Native Alaskans, running the gamut from bigotry to compromising subsistence. This is an
impressive argument and takes much away from the argument that this mining operation will
bring a much-needed (in the eyes of the mine operators) cash jobs to a "depressed" region of
the state. Indeed, based on the case history of North Slope, less than 1% of the work force was
made up of Inupiat. These points are made almost too dispassionately in text (even recognizing
that EPA is attempting to maintain a "neutral" voice throughout the report).
EPA FINAL RESPONSE: The text of Chapter 12 cites Alaska Native case studies with regard to
employment in resource extraction industries. We believe that the level of discussion of this issue
is appropriate, considering that the assessment is not an economic cost/benefit analysis. We would
expect that a full evaluation of any future mining permit applications and subsequent National
Environmental Policy Act Environmental Impact Statement would consider the costs and benefits
of employment opportunities related to large-scale mining.
Page 12-17.1 am not sure how we manage to emphasize even more the confounding effects of
mining and climate change on subsistence fisheries by Native Alaskans for I think this is
extremely important and (as alluded to in text) extremely difficult to forecast. Couple these
effects with the "portfolio" features of the salmonid populations, and I think we have real
reason for concern, i.e., while these seven species of salmonids have a full range of life history
strategies and flexibilities evolutionarily adapted to the historical environmental variation in
the Bristol Bay Watershed, nothing in their history (or their portfolio) prepares them for either
the mining or the climate-change impacts on the environment. Consequently, even given their
tremendous life history variation, these salmonids are ill-prepared (evolutionarily speaking) for
these future changes. Life history specialists will be completely lost due to mining and its
complicated interactions with climate change.
EPA FINAL RESPONSE: No response required.
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Chapter 13
John D. Stednick, Ph.D.
General comments. Identification of other potential mineral plays in the study area. Using
statistics from the Pebble mine (NWI, NHD, etc.) impacts of other potential mines were
approximated. Vulnerability of salmon stocks was identified with the need for healthy
watersheds and the 4 H's used in the Pacific Northwest.
EPA FINAL RESPONSE: No response required.
Specific comments: This chapter used Tables 13.2 to 13.8 (11 pages total) to inventory the
waters, fish, and subsistence uses potentially affected by the various mine prospects.
Comparisons between mines are difficult when using tabular formats. I suggest that a GIS
generated map would be more illustrative of areas affects and would allow for easier mine
comparisons. The waters, fish habitats, and subsidence uses could be identified and then the
mine 'footprint' overlaid. Figure 13.3 is such an example.
EPA FINAL RESPONSE: We agree that a map can be more illustrative than a table, especially
for comparison purposes. However, the purpose of the information compiled in Tables 13-2 to 13-
8 is not to compare potential effects among the six mines. These tables simply to inventory
resources to document that there is potential risk throughout the watershed where prospective
mine sites exist. Each of the tables quickly and easily shows that the prospective mine sites are all
near large numbers of significant aquatic resources that support numerous fish species and
numerous target species for subsistence use. We chose to use tables instead of maps because
information on a map suggests more certainty on the development of specific mines than there is,
and because the maps would be very busy and difficult to interpret. Figure 13-3 works because it is
limited to subsistence resources and the use of those resources is well documented.
Table 13.8 is a compilation of the 6 potential mine sites effect on the various resources. If all
water, and all fishes, and all subsistence uses are equal, this is a fair comparison; however that
was not supported.
EPA FINAL RESPONSE: It is true that the quality and functions of the aquatic resources that
could be eliminated at the potential mine sites varies. The table is not meant to compare the
potential impacts at the six sites. It demonstrates the amount of aquatic resources that could be
eliminated by a typical mine. The length of streams or area of wetlands eliminated are one aspect
of the cumulative risk of a mining district, but does not address the quality or ecosystem functions
of lost habitat. Analysis to that level of specificity would suggest more certainty in the development,
size, and location of these potential mines than currently exists.
The cumulative effects of the mine projects (Section 13.2.7) is a simple reiteration of the various
potential processes as affects by mine development; i.e. loss of fish habitat from the mine
footprint, loss of streamflow waters by water withdrawal. There is little evaluation or
discussion of cumulative effects—cumulative results result from individually minor but
collectively significant actions taking place over a period of time (p. 13-2). This current risk
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assessment suggests that cumulative effects would occur with the presence of the Pebble Mine
and additional mine operations would simply add to that impact. If that is the conclusion of the
EPA, then that theme should be consistent. Wording such as leading to increased release of
contaminated waters downstream (p. 13-31); the relatively ephemeral nature of human institutions
(p. 13-31), more susceptible to trespassing, poaching, and illegal dumping (p. 13-32) are in
contradiction to statements such as opportunities for employment at mines or mine-related
services would contribute to growth in nearby communities (p. 13-31). Induced development
following the advent of large scale mining would undoubtedly bring very welcome economic
development to the region (p. 13-32). The cumulative impact analysis sections, lacks a defined
methodology and the chapter lacks objectivity.
EPA FINAL RESPONSE: We disagree that the analysis lacks a defined methodology. In fact, the
commenter described the methodology, that additional mines add to the impacts of the first mine.
This "theme" of simply adding the impacts of the mines was carried consistently through the
chapter. Habitat eliminated was the only assessment end point for which we developed quantitative
estimates for each mine, but the additive nature of the analysis was carried through the analysis
for multiple mines (Section 13.2.7), the potential effects on assessment endpoints (Section 13.4)
and the Summary (Section 13.5). The potential habitat eliminated is a good indicator of the
potential for cumulative impacts and demonstrates how the impacts from relatively minor mines
can collectively result in significant loss of habitat from just the mine footprints.
We also disagree that the apparent contradiction in the wording examples given results in a lack of
objectivity. In fact, it reflects the objectivity in the analysis. It recognizes that while the possibility
for impacts increases with cumulative development, opportunities for employment and economic
development also increase.
The last sentence in this chapter states Even in the coastal population centers of Alaska,
hatcheries are supplementing salmon returns (p. 13-35). How is this related to cumulative
effects? I was disappointed in the quality of this chapter.
EPA FINAL RESPONSE: That sentence was intended to show that the pattern of development
that has led to the near-complete loss of wild salmon in the Pacific Northwest is being repeated in
the population centers of Alaska, which are using hatcheries to supplement decreasing wild
salmon returns. To avoid any confusion, the sentence has been deleted.
Roy A. Stein, Ph.D.
Page 13-2, Table 13-1. Could the authors add approximate sizes of these mines that could be
developed in the future? I appreciate the fact that the total area, at 1,300 km2, is provided on
page 13-7.
EPA FINAL RESPONSE: The 1,300 km2 refers to seven land management units designated for
mining in the Bristol Bay Area Plan for State Lands (ADNR 2005). The potential mines evaluated
in the assessment include mines from some of these management units, as well as others. Table
13-8 shows that the claim block sizes for the six potential mines add up to 2,420 km2. In the
analysis we utilized the Pebble 0.25 mine scenario because it is more typical of the average size of
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porphyry copper mines worldwide. As shown in Table 13.8, the assumed median mine footprints
would range from 3.87 to 10.7 km2 depending on whether the mines utilize TSFfacilities that
would be available at a Pebble mine, resulting in a total footprint of 35.0 to 57.4 km2.
Page 13-5. Once again the conceptual model does a nice job of setting the stage for the sorts of
interactions that would likely occur following the initial establishment of the Pebble Mine in
the Bristol Bay Watershed. After a review of this model, the reader is then prepared for the
text to follow.
EPA FINAL RESPONSE: No response required.
Page 13-7, first paragraph under 13.2. Impossible to predict the future of mine development,
including the order of mines that might come online and their respective impacts. It is,
however, safe to say that additional development of mines will indeed occur if Pebble is
permitted to move forward; this is certainly inevitable. Too many caveats here may provide
fodder for suggesting that the EPA does not know that a mining district will develop. What
would help us here is what has been done in previous chapters, i.e., the documentation of case
histories where initial mining ultimately led to a mining district.
EPA FINAL RESPONSE: It is true that we do not know that multiple mines will follow if a mine
is developed at the Pebble deposit. We have demonstrated that development of additional mines is
reasonably foreseeable, but we recognize that it is not certain. To do otherwise would threaten the
objectivity of the analysis. The development of mining districts is well understood, especially in
Alaska. Objectivity would demand that case studies of initial mining efforts that did not result in a
mining district be described as well, and in truth there appear to be many more examples of one-
mine mining districts than of large multiple-mine districts that grew from a single initial mine.
Page 13-8. Median mine size of 0.25 Pebble is assumed in the context of predicting the impacts
of new mines. Can this assumption be justified a bit more? Do the authors sense that this is a
conservative estimate for new mines, a reasonable one (this is the sense that I get from the tone
of the text), or a liberal estimate?
EPA FINAL RESPONSE: Results of exploration activities at these mine sites have not been
published, so we believe that it is reasonable to use the worldwide median mine size until more
definitive information is available.
Page 13-9, Box 13-1. Breaking out methods in boxes like this has served this document well,
making it easy for the reader to capture the essence of the conclusions without getting bogged
down in too many methodological details.
EPA FINAL RESPONSE: No response required.
Tables 13-2 to 13-8. These tables provide a nice combination of qualitative and quantitative
data to support conclusions generated for cumulative impacts of additional mining
development. Good work with limited information.
EPA FINAL RESPONSE: No response required.
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Page 13-23, Big Chunk North, as just one example. I like the fact that the authors did multiple
scenarios when they were unsure as to whether a future mine would use an already established
TSF or one that the future mine would build on its site. In this fashion, the EPA has bounded
the impact of future development, allowing the reader to see both minimal and maximal effects
of new mines, a technique that could productively be used elsewhere in this chapter.
EPA FINAL RESPONSE: We did use upper and lower bounds whenever possible. For example,
we calculated upper and lower bounds for wetland impacts for prospects with no National
Wetlands Inventory coverage. Where information for bounding was lacking, we used conservative
estimates to avoid introducing bias against mining development. An example of this is that we did
not try to estimate the size of groundwater drawdown zones for the six mines, ensuring that our
analysis of the mine footprints is conservative.
General Point re Chapter 13. On the one hand, the writing here is dispassionate and objective,
as I presume it should be with scientific writing. Even so, I would like the authors to make
some judgment calls re the impacts of these six different mines on the environment. Those that
have high densities of streams, wetlands, and ponds would undoubtedly experience greater
degradation to the salmonids than one that has a far lower density (is this true?). In turn, one
could ask if there are other characteristics of the environment that make one mine worse in
terms of its negative impact than another. Bringing out these comparative statements would
help the reader understand the individual impacts of new mines. As just one other example of
this issue, it is often noted that streams are "strongly meandering"; one additional statement
that would help the reader would argue something along the lines of "making road
development far more difficult and likely to have a greater impact on salmonid populations".
EPA FINAL RESPONSE: In this section we are quantifying the total stream and wetland areas
that could be lost to six potential additional mines in the watersheds, rather than examining
relative impacts across these six mines. No change required.
Page 13-28, third paragraph. I think that the last sentence of this paragraph requires some
modification for it now reads "...diminishing the biological complexity of salmon stocks and
lead to the portfolio effect..." The fact is that because of the diversity of life histories within
species across populations within stocks, salmonids do well even as environmental conditions
change from year to year. Here the authors are arguing in this last sentence that reductions in
biological complexity will "lead to the portfolio effect" but rather this decrease will
compromise the portfolio effect by eliminating stocks with specific life history characteristics.
Cleaning up this text will improve its presentation.
EPA FINAL RESPONSE: This text has been revised.
Page 13-29, Impervious Surface Increase. No citations are provided here. Do we know anything
about 10% being a useful metric for increasing negative impacts on stream flow and flooding?
EPA FINAL RESPONSE: We have added a short discussion of the importance of 10% impervious
surface area.
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Page 13-35. Indeed, we now require salmon hatcheries in some urbanized areas within Alaska.
Is this point worth emphasizing? Are the hatcheries really required because the nearshore
environment has been degraded? A box detailing this example with some hard data might go a
long way toward making the point that development means loss of important locally adapted
salmon stocks.
EPA FINAL RESPONSE: This sentence has been deleted.
General Point re Chapter 13.1 am not sure how to handle this concern. When the authors
discuss the various impacts of different infrastructural features in a cumulative sense, they do
not review all of the issues each contributes. For example, there is no mention of dust or
invasive species when discussing roads. Similarly, when discussing pipelines, nothing is said
about accidents. The authors certainly cannot be expected to review all features of all of these
infrastructural impacts, but some recognition of all of their impacts might be warranted,
perhaps as a sidebar or briefly highlighted in an associated box (as done so successfully in
previous chapters).
EPA FINAL RESPONSE: This is a valid point that we struggled with in development of Chapter
13. It is tempting to launch detailed evaluations of countless interactive stressors that could result
from a number of mines scattered across the watersheds, their roads and infrastructure, and the
resulting induced development. However, none of those possible stressors is certain and there is no
way to predict the course or extent of induced development. Thus, such a complex evaluation
would suggest a certainty in the future of the watersheds that doesn 't exist. Our approach instead
was to identify a reasonably foreseeable future scenario, the development of one to six additional
mines that are currently being explored and a detailed, quantified evaluation of one aspect of that
development, the size of the mine footprints, and the resulting loss of aquatic resources. When
compared to the predicted impacts from the Pebble scenarios evaluated in the assessment, the
analysis provides an index or indicator of the impacts of development of a mining district. This
mining district would more than double the wetland area lost and would increase stream loss by 70
km. As this and other commenters have noted, our analysis of the contribution of the different
infrastructures to cumulative impacts is general, but it is given dimension by this comparison of
the foot print of mines in a potential mining district to the foot print ofpotential mine at the Pebble
deposit.
Chapter 14
John D. Stednick, Ph.D.
General comments:
This chapter summarizes the risk analysis results organized by endpoint, limitations and
uncertainties are identified.
EPA FINAL RESPONSE: No response required.
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Specific comments: It would be useful to have more references to the previous section in the
assessment to more easily direct the reader to earlier sections.
EPA FINAL RESPONSE: More references to earlier sections of the assessment have been added.
1. 14-1.... local habitat loss leading to losses of local unique populations. I do not remember
reading about genetic uniqueness in the assessment earlier.
EPA FINAL RESPONSE: This topic is covered in both Chapter 5 (Section 5.2.4) and
Chapter 7 (Section 7.2.5).
Explain differences between mine footprint loss of 38, 90, and 145 km and habitat loss
of 8, 24, and 35 km.
EPA FINAL RESPONSE: Mine footprint losses of 38-151 km (in the final assessment)
include losses of 8-36 km of documented salmon habitat. Text has been modified to clarify
that the second set of values reflects the portion of total stream length documented to
contain anadrontous salmon.
Explain the threshold exceedance of 20% again and better clarify to show a decrease in
streamflow (mean annual flows).
EPA FINAL RESPONSE: We respectfully disagree. This chapter is a summary of results
and does not include discussions of methods and assumptions.
Altered streamflow would result in an unquantified loss of riparian floodplain wetland
habitat, yet next section quantifies the wetland loss and reduced off-channel salmonid
habitat. Seems inconsistent.
EPA FINAL RESPONSE: The first statement specifically refers to loss of riparian
floodplain wetlands from altered streamflows downstream of the mine footprint. The
quantified losses are direct losses due to excavation, filling, or diversion in the mine
footprint.
Shift in groundwater and surface water balance in streams makes the stream less
suitable for spawning and rearing in winter due to decreased winter flow?
EPA FINAL RESPONSE: The statement is "could reduce winter habitat and make the
streams less suitable for spawning and rearing" which indicates two different effects:
reduced winter habitat and less suitable habitat for spawning and rearing. Spawning does
not occur in the winter. To clarify winter habitat, we have added the parenthetical phrase
"(i.e., unfrozen stream reaches)".
2. 14-3 suggest the need for additional mitigation measures. Suggest stronger wording
such as more aggressive mitigation.
EPA FINAL RESPONSE: We feel the current language is appropriate for the assessment.
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Possible introduction of invasive species? Plants or animals?
EPA FINAL RESPONSE: We added the phrase "particularly plants and fish pathogens."
3. 14-4 the lower bound is purely aspirational. If it is aspirational then it should not be
considered. Realistic bounds should be used always.
EPA FINAL RESPONSE: The comment ignores the following phrase "in that it has no
empirical basis." It is aspirational in that it has no empirical basis, but that does not mean
it is unrealistic. Since this mine would be unprecedented, we must consider the standards
to which the designers would aspire.
Last paragraph in this section should be moved up front as identification of
assumptions in the assessment.
EPA FINAL RESPONSE: Information in this paragraph has been incorporated into
Section 6.1, as well as kept in Chapter 14.
4. 14-7 scouring the valley and depositing tailings. Seems inconsistent as written, you do
not scour by depositing sediment. Needs expansion.
EPA FINAL RESPONSE: The statement uses the conjunction "and" not the preposition
"by." As explained in Chapter 9, the initial flow would scour the valley below the dam and
then, when flow diminished, tailings would deposit in the same area.
5. 14-13. ...an initial outflow beyond the 30km limit of the model. The 30km was the model
boundary used, not the model limitation.
EPA FINAL RESPONSE: The word "implementation " has been added after "model."
Roy A. Stein, Ph.D.
Page 14-3. Conventional mining practices may be sufficient for the smallest footprint for the
Pebble Mine, i.e., 0.25 but beyond this size, conventional mining practices do not protect the
environment to the extent required to protect salmonids. Hence the commercial and sport
fisheries, and specifically the subsistence fisheries by Native Alaskans are threatened. Given
this conclusion, permitting of this mine would be suspect at best.
EPA FINAL RESPONSE: No response required.
Additional Comments
John D. Stednick, Ph.D.
This technical review is on the above referenced document. General comments are presented
here, and chapter-specific comments or critiques are presented below. The document has now
been written as an environmental risk assessment and thus has eliminated the previous
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confusion as a Clean Water Act 404(c) evaluation. The theoretical models (as figures) are
excellent, yet scarcely referenced or used. As pointed out in the review of the first draft, the
appendices provide very useful information and data that are often not fully incorporated or
included in the text. Admittedly the appendices vary in quantitative information, but currently
the reader is directed to the appendix rather than having data or main points presented
directly. Throughout the document, I found a lack of coordination between the written text
and the tables and figures in the main text body. Tables or figures were casually referenced
with no presentation or little discussion of main points. Tables and figures should stand
independently, that is information is presented in such a manner that the reader can make the
same conclusion as the authors. Similarly, the text should be able to 'stand alone' whereby
enough information is presented in the text as summary statistics or other quantitative points
that the reader makes the same conclusion. I found that considerable time was needed to
understand the figure/table point(s) as related to the text. This can be addressed with text
editing and some reorganization.
EPA FINAL RESPONSE: The pathways illustrated in the conceptual models helped to inform the
analyses conducted in the assessment, and relevant sections of the models have been added to risk
analysis chapters.
We agree that the appendices contain valuable information, which is why they have been included
as appendices. However, inclusion of the level of detail provided in the appendices into the main
assessment report would make the document unwieldy and would obscure the main purpose of the
assessment, which is to evaluate potential mining impacts. We have attempted to pull relevant
material from the appendices forward into the main assessment, without overwhelming the reader;
we also acknowledge throughout that more detailed background information is contained in the
appendices.
As to the point about text versus figures and tables, we respectfully disagree. The text should not
reiterate the detailed information contained in the figures and tables, but rather concisely state the
key results or implications of those figures and tables. However, we have attempted to provide
clarification where additional explanation in the text and/or table headings would help describe
what is presented in the tables and figures.
Chapter 15. References
Better inclusion of references suggested in review of the first draft.
EPA FINAL RESPONSE: No response required
Appendices
A casual read of the appendices showed that certain appendices were edited or updated. We
were specifically asked to review Appendix I: Conventional water quality mitigation practices
for mine design, construction, operation and closure and Appendix J: Compensatory
mitigation and large-scale hardrock mining in the Bristol; Bay watershed. Appendix I was a
well -referenced document explaining conventional water quality best management practices
(BMPs). The document was easy to read and covered the subject well. Appendix J identified
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compensatory mitigation from the federal and Alaska state levels. It addresses specific
comments from public hearings on the Pebble Project as related to compensatory mitigation.
EPA FINAL RESPONSE: No response required.
Both of these appendices contain useful information, which needs to be incorporated in the
main text of the assessment, rather than be relegated to an appendix. A concern that I have
frequently expressed.
EPA FINAL RESPONSE: We disagree. The appendices are background information that would
disrupt the assessment if they were incorporated.
Final thoughts
The second review draft is a significant improvement from the first draft, but is still in need of
editing rewriting to address review comments. The second draft addressed several points that
were brought about in the first review, including the effects of atmospheric N inputs from
blasting and global climate change. Conversely EPA decided not to address other points
including the effects of precipitation timing on variably frozen soils on streamflow generation,
and the transport of total and dissolved organic matter on metal transport. Another point to
consider in the next version is the potential for TENORMs—technologically enhanced naturally
occurring radioactive materials being present or causing risk (see EPA report 402-R-99-002).
EPA FINAL RESPONSE: We concluded that TENORMs would be a minor issue with respect to
salmonid fish. The comment about transport of organic matter on metal transport is unclear, but
the effects of organic matter on metal bioavailability are discussed and incorporated into toxicity
modeling for copper.
Process observations
For the second external review, the US Environmental Protection Agency elected to negotiate
and contract with the external reviewers individually. The pay rate and estimated time to
complete the review were significantly less than original estimates. A concern also shared by
other external reviewers. As much as I argued that the interdisciplinary approach experienced
in Anchorage produced a better document review, EPA was not interested in allowing
collaboration or wanting a 'consensus' opinion. The former I support, the later I never did.
The purpose of any collaboration is to better foster interdisciplinary discussions and
appreciation of alternative views, all to make a better environmental risk assessment. In my
estimation, this is an opportunity lost and a lesson to be heeded in future external reviews.
EPA FINAL RESPONSE: The peer reviewers had every opportunity to interact and collaborate in
person at a workshop in Anchorage during the first review and by whatever means they chose
during the second review.
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Roy A. Stein, Ph.D.
Transmittal material
I am submitting my Peer Review Comments on EPA's Draft Document, Second External
Review Draft, EPA 910-R-12-004Ba, April 2013 entitled An Assessment of Potential Mining
Impacts on Sainton Ecosystems of Bristol Bay, Alaska. All of my comments can be found below
with appropriate page numbers and/or table/figure numbers. I did not follow your suggestion
in a recent e-mail to arrange my comments around my initial concerns regarding EPA's First
Draft Document simply because 1) I had already begun my review without following this
advice, 2) I note that the Second Draft has been completely rewritten, reorganized, and revised
and therefore did not neatly follow my initial concerns, and most importantly, 3) the EPA
authors dealt fully and completely with all of my concerns. In fact, I carefully reviewed the
EPA Response to our Peer Review Report, concluding that I am quite satisfied with how the
EPA authors revised the text of this Second Draft in response to my comments. Even so, I still
have additional comments that grew out of my review of the Second External Review Draft.
EPA FINAL RESPONSE: See responses throughout this document.
EPA Response Document
General Point I. Overall, I was impressed with how the team of authors dealt with our reviews.
For each point, there was succinct, explicit, and reasoned response. Not always did our
concerns receive full treatment in the revision. However, if they did not, the EPA response
included an explanation that was well crafted and justified.
EPA FINAL RESPONSE: No response required.
General Point II. Because there are no data on the management of water quality "In
Perpetuity" (i.e., we have no experiences in this area simply because we do not have mines that
have been closed for a sufficiently long period of time (>100 years) to gain this experience), the
EPA cannot write about what might be expected in the "long term". Even so, no one is
optimistic. Without the profit incentive, corporate entities are not likely to monitor, treat, and
maintain these facilities. Indeed, corporations are likely to go out of business in their current
structure and therefore this responsibility will fall to the State of Alaska, whose record is not
the most enviable in this arena. It seems to me that TSFs will fail, given enough changes in
responsibility over time. Impacts on the salmon, the subsistence Native Alaskan culture, the
commercial/sport fisheries, and the entire ecosystem will be large, long-lasting (at least multiple
hundreds of years), and not preventable. With this certain knowledge in hand, I can only
conclude that the Pebble copper mine and Bristol Bay salmon cannot coexist. The mine will
indeed eliminate the salmon runs in the areas affected by a catastrophic failure of the Tailings
Storage Facility. This mine should not be built in the Bristol Bay Watershed for it will have
nearly irreparable impacts on the water quality of this watershed.
EPA FINAL RESPONSE: No response required.
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General Point III. Though we do not have long-term data from any mines post-closure, what do
the short-term data tell us? They tell us that insidious effects of the facilities that remain after
mining compromise water quality to the extent that it influences ecosystem functioning
eliminates the ability of streams affected to support fishes intolerant of poor-quality water. We
have experience that tells us that this has occurred and thus has an extremely high probability
of re-occurrence in the Pebble area.
EPA FINAL RESPONSE: No response required.
General Point IV. Even though we have the experiences noted in items 17a-b, the Bristol Bay
Watershed is even more vulnerable that the other systems studied, in that it is an extremely wet
environment with ground-water operating to communicate among streams (inter-
connectedness). With this inter-connectedness come the increasing widespread effects of mine
pollution and thus an increased impact on the whole of the Bristol Bay Watershed.
EPA FINAL RESPONSE: No response required.
General Point V. The Nushagak and Kvichak rivers are exceptional salmonid streams, even for
the Bristol Bay Watershed. Loss of these populations would likely negatively influence salmon
populations that are available for harvest. That the headwaters of these two rivers lie in the
middle of the Pebble Mine impacts argues for a precautionary approach to the permitting
process.
EPA FINAL RESPONSE: No response required.
Page 13, EPA Response to Peer Review Report. I agree with the team of authors when they
suggest that including the Mount St Helens data re recovery of stream communities makes
sense. At present, they have removed these data; I would like to see them included as they can
help make the case re the impact of a TSF failure on Bristol Bay Watershed streams.
EPA FINAL RESPONSE: The Mount St. Helens data were not reintroduced based on the
majority opinion of the reviewers.
Some inconsistency exists within the "Response Document". On page 7 the team argues that
development of a monitoring program to distinguish between mining and climate change
effects is outside the scope of the assessment". Yet, on page 44, the authors argue that "...
Chapter 3 and Box 14-2 include a discussion of the need for future monitoring to differentiate
climate change effects from large-mining effects". Clearly, Box 14-2 seeks to present the
importance of the monitoring program in light of the comparative effects of mining versus
global climate change. The text of the "Response Document" should be revised to reflect these
goals to maintain consistency.
EPA FINAL RESPONSE: We do not believe that we have been inconsistent. We conclude that
monitoring would be needed, but we do not develop a monitoring program
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Page 63, third full paragraph, Response Document. I am surprised that the answer to this
question does not include the reference to Box 4.1 in the Second Draft that defines all of the
relevant terms. For the sake of completeness, this box should be referenced here.
EPA FINAL RESPONSE: Reference to this box has been added to the final EPA response.
As I read through the Response Document (see top of page 79 as just one example of many), I
am troubled by the ongoing conversation that suggests that we might know too little specific
information about the salmonids in the two river systems affected that the mine proponents can
argue that they will have a minimal impact, thus allowing the mine and its operations to be
permitted by the State of Alaska. I have no solution to this conundrum, but it bothers me that
the burden of proof lies with the EPA and other regulatory bodies to demonstrate negative
impacts on the extant salmonid populations. I do wish the system was reversed, i.e., that the
company proposing this development would be required to demonstrate "no effect" on the
salmonid populations before permitting could occur.
EPA FINAL RESPONSE: No response required.
Page 100, Response Document. I agree that the EPA has substantially strengthened the
arguments associated with "future technology" as being the solution to all of the issues that lay
before Pebble LLC in Chapter 9. These arguments are critically important to the assessment of
whether the mine will indeed compromise water quality and therefore salmonid success. To
allow the company to argue that historical failure rates of various portions of the mine are not
appropriate because newer technology will prevent these failures is simply not right, i.e., in the
context of any evaluation of the environmental impact of a proposed mining facility.
EPA FINAL RESPONSE: No response required.
Page 130, Response Document. Under comments about the transportation corridor, it is
appropriate to note that 70 crossings have been changed in the revised document to a minimum
of 70 crossings. This particularly seems pertinent to these responses to the Expert Panel
concerns as expressed.
EPA FINAL RESPONSE: No response required.
Question 10 dealing with risks to wildlife and human cultures, page 139, Response Document.
To this point, I did think that the responses by EPA were complete and well-thought-out.
Reponses to the critique by the Expert Panel to Question 10 were less well developed without
(typically) references to specific passages in specific chapters. I believe the EPA authors
handled most all of the concerns expressed herein, especially so after sharpening the scope of
their Ecological Assessment. Even so, the EPA failed to explicitly lay out exactly how they
handled each of the concerns expressed by the Expert Panel, which is too bad because I think
that they did deal reasonably well with these issues in their revised draft.
EPA FINAL RESPONSE: The assessment sections regarding Alaska Native cultures and wildlife
underwent significant revisions and expansion from the draft to the revised draft assessment. Most
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important, a separate chapter (Chapter 12) was created to highlight fish-mediated effects on these
endpoints. See below for additional clarification.
Note just a few examples:
1. Page 141, top of page. In the first response, there are no references to the revised text.
EPA FINAL RESPONSE: In response to this comment, the vulnerabilities listed in
Appendix D were brought forward into the assessment text (Section 12.1) and references to
non-Alaska Natives who depend on the commercial, recreational, and subsistence fishery
were added in several places.
2. Page 141, middle of page. In the second and third responses on this page, little detail is
provided; the EPA authors only refer to Chapter 12 when indeed they could have
provided an insightful short paragraph that would explain precisely how they handled
these issues (for they did, as I recall, in the revised text).
EPA FINAL RESPONSE: In response to this comment, information from case studies was
added to Sections 12.2.1 through 12.2.4.
3. Page 151, second response on the page. Here a more complete answer would have
included references to all of the NEW conceptual models that were developed and
discussed in the revised Second Draft.
EPA FINAL RESPONSE: The conceptual model related to wildlife (Figure 12-1) was
added to the revised draft assessment.
4. Given what I have read to this point re responses, I was disappointed in this section re
EPA responses...for they are rather perfunctory rather than explicit and detailed, and
this is especially true for the responses to Dr. Paul Whitney's comments and concerns.
EPA FINAL RESPONSE: No specific examples are cited so no specific clarification can
be provided. All efforts were made to provide accurate, thorough responses to all comments
that required responses. All of the comments from Dr. Whitney suggesting revisions were
responded to, and changes made to the assessment where appropriate.
5. Finally, one can appreciate my concern by simply comparing EPA responses to
concerns expressed by the Expert Panel regarding Question 10 versus Question 11.
EPA FINAL RESPONSE: No specific issues were cited, so no specific clarification can be
provided.
Page 177, Response Document. I appreciate the response the authors have generated relative to
the ideas surrounding uncertainty. Their revised draft considerably improves their
presentation of the topic and the response on the middle of page 177 helps me understand their
point of view with regard to uncertainty (see response comment on page 178 where the EPA
argues that putting forward "reasonable and typical scenarios" to characterize risk and then
the uncertainty surrounding that risk (I agree with this approach).
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EPA FINAL RESPONSE: No response required.
General comment on my comments. All comments were seriously considered by the EPA
authors and were either appropriately dealt with in their revised text or explained that the
concern did not fall under the "scope of the ecological assessment". Thus, I am pleased with the
revision as it relates to my initial concerns about the first draft of the Main Report. Though I
cannot speak for my colleagues as to the adequacy of EPA's response to their concerns, my
reading of the Response Document demonstrates that I found most all of EPA's responses well-
reasoned, consistent across questions and concerns, and overall well done (save for Question
10, see comments above).
EPA FINAL RESPONSE: No response required.
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