&EPA
United States
Environmental Protection
Agency
December 2022
Recommended Determination of the
U.S. Environmental Protection Agency Region 10
Pursuant to Section 404(c) of the Clean Water Act
Pebble Deposit Area, Southwest Alaska
Region 10, Seattle, WA
www.epa.gov/bristolbay
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December 2022
Recommended Determination of the
U.S. Environmental Protection Agency Region 10
Pursuant to Section 404(c) of the Clean Water Act
Pebble Deposit Area, Southwest Alaska
U.S. Environmental Protection Agency
Region 10
Seattle, WA
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Preferred citation: USEPA (U.S. Environmental Protection Agency). 2022. Recommended
Determination of the U.S Environmental Protection Agency Region 10 Pursuant to Section 404(C) of the
Clean Water Act, Pebble Deposit Area. Region 10, Seattle, WA.
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Executive Summary ES-1
Proposed Mine at the Pebble Deposit ES-3
2014 Proposed Determination ES-9
2022 Proposed Determination ES-10
The Recommended Determination ES-11
Overview of Prohibition and Restriction in the Recommended Determination ES-14
Recommended Prohibition ES-14
Recommended Restriction ES-15
When a Proposal is Not Subject to this Determination ES-19
Evaluation of Portions of the CWA Section 404(b)(1) Guidelines ES-19
Information about Other Adverse Effects of Concern on Aquatic Resources ES-19
Authority and Justification for Undertaking a CWA Section 404(c) Review at this Time ES-20
Conclusion ES-21
Section 1. Introduction 1-1
Section 2. Project Description and Background 2-1
2.1 Project Description 2-1
2.1.1 Overview of the Pebble Deposit 2-1
2.1.2 Overview of the 2020 Mine Plan 2-2
2.1.2.1 Mine Site 2-2
2.1.2.2 Evaluation of Location Options for a Mine Site at the Pebble Deposit 2-4
2.2 Background 2-8
2.2.1 Timeline of Key Events Related to the Pebble Deposit (1984-October
2021) 2-8
2.2.2 Re-initiation of Clean Water Act Section 404(c) Review Process
(November 2021-Present) 2-17
2.2.3 Authority and Justification for Undertaking a Section 404(c) Review at
this Time 2-21
Section 3. Importance of the Region's Ecological Resources 3-1
3.1 Physical Setting 3-2
3.2 Aquatic Habitats 3-3
3.2.1 Quantity and Diversity of Aquatic Habitats 3-3
3.2.2 Streams 3-6
3.2.3 Wetlands, Lakes, and Ponds 3-8
3.2.4 Importance of Headwater Stream and Wetland Habitats to Fish 3-11
Recommended Determination
December 2022
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Contents
3.3 Fish Resources 3-14
3.3.1 Species and Life Histories 3-14
3.3.2 Distribution and Abundance 3-21
3.3.2.1 Nushagak and Kvichak River Watersheds 3-21
3.3.2.2 South Fork Koktuli River, North Fork Koktuli River, and Upper
Talarik Creek Watersheds 3-27
3.3.3 Habitat Complexity, Biocomplexity, and the Portfolio Effect 3-40
3.3.3.1 The Relationship between Habitat Complexity and Biocomplexity 3-40
3.3.3.2 The Portfolio Effect 3-45
3.3.4 Salmon and Marine-Derived Nutrients 3-51
3.3.5 Commercial Fisheries 3-53
3.3.6 Subsistence Fisheries 3-55
3.3.6.1 Use of Subsistence Fisheries 3-55
3.3.6.2 Importance of Subsistence Fisheries 3-59
3.3.7 Recreational Fisheries 3-60
3.3.8 Region's Fisheries in the Global Context 3-63
3.4 Summary 3-64
Section 4. Basis for Recommended Determination 4-1
4.1 Section 404(c) Standards 4-1
4.2 Effects on Fishery Areas from Discharges of Dredged or Fill Material from
Developing the Pebble Deposit 4-2
4.2.1 Adverse Effects of Loss of Anadromous Fish Streams 4-6
4.2.1.1 Anadromous Fish Streams That Would Be Permanently Lost at the
Mine Site 4-7
4.2.1.2 Adverse Effects from Permanent Losses of Anadromous Fish Streams
at the Mine Site 4-11
4.2.1.3 Adverse Effects from Permanent Losses of Ecological Subsidies to
Anadromous Fish Streams Downstream of the Mine Site 4-14
4.2.1.4 Impacts on Other Fish Species 4-15
4.2.1.5 Conclusions 4-21
4.2.1.5.1 Adverse Effects of the Loss of Anadromous Fish Streams at
the Mine Site 4-21
4.2.1.5.2 Adverse Effects of the Loss of Anadromous Fish Streams
Elsewhere in the SFK, NFK, and UTC Watersheds 4-21
4.2.2 Adverse Effects of Loss of Additional Streams that Support Anadromous
Fish Streams 4-23
4.2.2.1 Impacts on Other Fish Species 4-27
4.2.2.2 Conclusions 4-27
4.2.2.2.1 Adverse Effects of Loss of Additional Streams atthe Mine Site
that Support Anadromous Fish Streams 4-28
Recommended Determination
ii
December 2022
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Contents
4.2.2.2.2 Adverse Effects of Loss of Additional Streams Elsewhere in
the SFK, NFK, and UTC Watersheds that Support
Anadromous Fish Streams 4-28
4.2.3 Adverse Effects of Loss of Wetlands and Other Waters that Support
Anadromous Fish Streams 4-30
4.2.3.1 Impacts on Other Fish Species 4-34
4.2.3.2 Conclusions 4-34
4.2.3.2.1 Adverse Effects of Loss of Wetlands and Other Waters at the
Mine Site that Support Anadromous Fish Streams 4-34
4.2.3.2.2 Adverse Effects of Loss of Wetlands and Other Waters
Elsewhere in the SFK, NFK, and UTC Watersheds that
Support Anadromous Fish Streams 4-35
4.2.4 Adverse Effects from Changes in Streamflow in Downstream
Anadromous Fish Streams 4-36
4.2.4.1 Methodology for Analyzing Streamflow Changes in Downstream
Anadromous Fish Streams 4-37
4.2.4.2 Overview of Mine Site Operations that Affect Downstream
Streamflow 4-39
4.2.4.3 Extent of Streamflow Changes in Downstream Anadromous Fish
Streams 4-42
4.2.4.4 Downstream Anadromous Fish Habitat Affected by Streamflow
Changes 4-45
4.2.4.5 Adverse Effects of Streamflow Changes in Downstream Anadromous
Fish Streams 4-48
4.2.4.6 Impacts on Other Fish Species 4-51
4.2.4.7 Conclusions 4-54
4.2.4.7.1 Adverse Effects from Discharges of Dredged or Fill Material
at the Mine Site that Result in Streamflow Changes in
Anadromous Fish Streams 4-54
4.2.4.7.2 Adverse Effects from Discharges of Dredged or Fill Material
Elsewhere in the SFK, NFK, and UTC Watersheds that Result
in Streamflow Changes in Anadromous Fish Streams 4-54
4.2.5 Summary of Effects on Fishery Areas from Discharges of Dredged or Fill
Material from Developing the Pebble Deposit 4-56
4.3 Compliance with Relevant Portions of the Section 404(b)(1) Guidelines 4-56
4.3.1 Significant D egradation 4-57
4.3.1.1 Direct and Secondary Effects of the 2020 Mine Plan 4-57
4.3.1.1.1 Adverse Effects of Loss of Anadromous Fish Streams 4-58
4.3.1.1.2 Adverse Effects of Loss of Additional Streams that Support
Anadromous Fish Streams 4-60
4.3.1.1.3 Adverse Effects of Loss of Wetlands and Other Waters that
Support Anadromous Fish Streams 4-61
Recommended Determination ;;; December 2022
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Contents
4.3.1.1.4 Adverse Effects from Changes in Streamflow in Downstream
Anadromous Fish Streams 4-63
4.3.1.1.5 Conclusion 4-64
4.3.1.2 Cumulative Effects of Mine Expansion 4-64
4.3.1.2.1 Cumulative Effects of Loss of Anadromous Fish Streams 4-67
4.3.1.2.2 Cumulative Effects of Loss of Additional Streams that
Support Anadromous Fish Streams 4-70
4.3.1.2.3 Cumulative Effects of Loss of Wetlands and Other Waters
that Support Anadromous Fish Streams 4-76
4.3.1.2.4 Cumulative Effects of Additional Degradation of Streams,
Wetlands, and Other Waters Beyond the Mine Site Footprint 4-76
4.3.1.3 Summary 4-78
4.3.2 Compensatory Mitigation Evaluation 4-79
4.3.2.1 Overview of Compensatory Mitigation Requirements 4-80
4.3.2.2 Review of Compensatory Mitigation Plans Submitted by the Pebble
Limited Partnership 4-81
4.3.2.2.1 January 2020 Compensatory Mitigation Plan 4-81
4.3.2.2.2 November 2020 Compensatory Mitigation Plan 4-83
4.3.2.3 Summary Regarding Compensatory Mitigation Measures 4-87
Section 5. Recommended Determination 5-1
5.1 Recommended Prohibition 5-1
5.1.1 Defined Area for Prohibition 5-2
5.2 Recommended Restriction 5-6
5.2.1 Defined Area for Restriction 5-6
5.2.2 Applicability of the Restriction 5-11
5.3 When a Proposal is Not Subject to this Determination 5-12
Section 6. Other Concerns and Considerations 6-1
6.1 Other Potential CWA Section 404(c) Resources 6-1
6.1.1 Wildlife 6-1
6.1.2 Recreation 6-3
6.1.3 Public Water Supplies 6-6
6.2 Effects of Spills and Failures 6-7
6.2.1 Final Environmental Impact Statement Spill and Release Scenarios 6-7
6.2.1.1 Release of Concentrate Slurry from the Concentrate Pipeline 6-7
6.2.1.2 Tailings Releases 6-8
6.2.1.3 Untreated Contact Water Release 6-12
6.2.2 Tailings D am Failure 6-12
6.3 Other Tribal Concerns 6-15
6.3.1 Subsistence Use and Potential Mining Impacts 6-15
6.3.2 Traditional Ecological Knowledge 6-20
6.3.3 Environmental Justice 6-23
Recommended Determination ¦ December 2022
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Contents
6.4 Consideration of Potential Costs 6-26
Section 7. Conclusion 7-1
Section 8. References 8-1
Appendix A. (Intentionally Left Blank)
Appendix B. Additional Information Related to the Assessment of Aquatic
Habitats and Fishes
Appendix C. Technical Evaluation of Potential Compensatory Mitigation
Measures
Recommended Determination
v
December 2022
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Contents
List of Boxes
BoxES-l Section 404 of The Clean Water Act ES-3
Box 3-1 Similarity of Aquatic Resources within the South Fork Koktuli River, North
Fork Koktuli River, and Upper Talarik Creek Watersheds 3-10
Box 4-1 Secondary Effects and Aquatic Resource Losses 4-4
Box 4-2 Key Definitions 4-5
Box 4-3 Water Resources Mapping at the Mine Site 4-25
Box 5-1 Applicability Data Requirements 5-3
List of Tables
Table 2-1 Bristol Bay Assessment timeline 2-11
Table 3-1 Distribution of stream channel length classified by channel size (based on
mean annual streamflow), channel gradient, and floodplain potential for
streams and rivers in the South Fork Koktuli River, North Fork Koktuli
River, and Upper Talarik Creek watersheds 3-8
Table 3-2 Acreage of wetland habitats in the South Fork Koktuli River, North Fork
Koktuli River, and Upper Talarik Creek watersheds. Number in
parentheses indicates percent of wetland or wetland type relative to total
area in the watershed 3-9
Table 3-3 Fish species reported in the Nushagak and Kvichak River watersheds 3-16
Table 3-4 Life history, habitat characteristics, and total documented stream length
occupied for Bristol Bay's five Pacific salmon species in the Nushagak and
Kvichak River watersheds 3-19
Table 3-5 Documented fish species occurrence in the South Fork Koktuli River,
North Fork Koktuli River, and Upper Talarik Creek watersheds 3-27
Table 3-6 Total documented anadromous fish stream length and stream length
documented to contain different salmonid species in the South Fork
Koktuli River, North Fork Koktuli River, and Upper Talarik Creek
watersheds 3-28
Table 3-7 Highest reported index spawner counts in the South Fork Koktuli River,
North Fork Koktuli River, and Upper Talarik Creek, based on mainstem
aerial surveys 3-36
Table 3-8 Highest reported number of adult salmon in tributaries of the South Fork
Koktuli River, North Fork Koktuli River, and Upper Talarik Creek, based
on aerial surveys 3-37
Table 3-9 Maximum estimated densities and total observed number of juvenile
Pacific salmon in mainstem habitats of the South Fork Koktuli River, North
Fork Koktuli River, and Upper Talarik Creek 3-38
Table 3-10 Relative abundance of salmonids in off-channel habitats ofthe South Fork
Koktuli River, North Fork Koktuli River, and Upper Talarik Creek 3-39
Recommended Determination j December 2022
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Contents
Table 3-11 Maximum estimated densities of resident fishes in mainstem habitats of
the South Fork Koktuli River, North Fork Koktuli River, and Upper Talarik
Creek 3-40
Table 3-12 Mean annual commercial catch (number of fish) by Pacific salmon species
and Bristol Bay fishing district, 2010-2019 3-53
Table 3-13 Estimated ex-vessel value of Bristol Bay's commercial salmon catch by
species, 2000-2019 3-54
Table 3-14 Harvest of subsistence fisheries resources in selected communities of the
Bristol Bay watershed 3-56
Table 3-15 Estimated subsistence salmon harvest in communities of the Bristol Bay
watershed, 2008-2017 3-58
Table 3-16 Estimated replacement value of 2017 Bristol Bay subsistence salmon
harvest 3-59
Table 3-17 Estimated sport harvest by species in the Bristol Bay Sport Fish
Management Area 3-61
Table 3-18 Estimated annual sport harvest and catch of fishes in the Kvichak River
watershed and the Nushagak, Wood, and Togiak River watersheds, 2008-
2017 3-63
Table 4-1 Length of anadromous fish streams permanently lost in tributaries to the
North Fork Koktuli River associated with the 2020 Mine Plan 4-7
Table 4-2 Coho and Chinook salmon stream habitat permanently lost in the North
Fork Koktuli River watershed associated with the 2020 Mine Plan 4-10
Table 4-3 Area of wetlands and other waters lost under the Pebble 2020 Mine Plan 4-31
Table 4-4 Change in the average monthly streamflow between baseline and end-of-
mine with water treatment plant discharge, 2020 Mine Plan 4-40
Table 4-5 Salmon species documented to occur in downstream reaches that would
experience greater than 20 percent streamflow alterations under the
Pebble 2020 Mine Plan 4-44
Table 4-6 Anadromous stream habitat that would be permanently lost in the South
Fork Koktuli River, North Fork Koktuli River, and Upper Talarik Creek
watersheds under the 2020 Mine Plan plus the Expanded Mine Scenario 4-67
Table 6-1 Summary description of Tailings Storage Facilities 6-9
Table 6-2 Harvest of subsistence resources for communities in the Nushagak and
Kvichak River watersheds 6-16
Recommended Determination
vii
December 2022
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Contents
List of Figures
Figure ES-1 The Bristol Bay watershed, composed of the Togiak, Nushagak, Kvichak,
Naknek, Egegik, and Ugashik River watersheds and the North Alaska
Peninsula ES-2
Figure ES-2 Major water bodies within the Nushagak and Kvichak River watersheds ES-4
Figure ES-3 Mine site hydrography ES-6
Figure ES-4 Mine site map ES-7
Figure ES-5 Mine site analysis area for wetlands and other waters ES-8
Figure ES-6 The Defined Area for Prohibition at the 2020 Mine Plan mine site ES-16
Figure ES-7 The Defined Area for Restriction and Defined Area for Prohibition overlain
on wetlands from the National Wetlands Inventory ES-17
Figure ES-8 The Defined Area for Restriction and Defined Area for Prohibition overlain
on streams and waterbodies from the National Hydrography Dataset ES-18
Figure 2-1 Project area map 2-3
Figure 2-2 Optional locations for siting the Bulk Tailing Storage Facility evaluated
within the FEIS 2-6
Figure 2-3 Optional locations for siting the Main Water Management Pond evaluated
within the FEIS 2-7
Figure 3-1 Diversity of Pacific salmon species production in the Nushagak and
Kvichak River watersheds 3-23
Figure 3-2 Anadromous fish distribution in the Nushagak and Kvichak River
watersheds 3-24
Figure 3-3 Rainbow Trout, Dolly Varden, and Arctic Grayling occurrence in the
Nushagak and Kvichak River watersheds 3-25
Figure 3-4 Northern Pike, stickleback, and sculpin occurrence in the Nushagak and
Kvichak River watersheds 3-26
Figure 3-5 Reported Coho Salmon distribution in the South Fork Koktuli River, North
Fork Koktuli River, and Upper Talarik Creek watersheds 3-29
Figure 3-6 Reported Chinook Salmon distribution in the South Fork Koktuli River,
North Fork Koktuli River, and Upper Talarik Creek watersheds 3-30
Figure 3-7 Reported Sockeye Salmon distribution in the South Fork Koktuli River,
North Fork Koktuli River, and Upper Talarik Creek watersheds 3-31
Figure 3-8 Reported Chum Salmon distribution in the South Fork Koktuli River,
North Fork Koktuli River, and Upper Talarik Creek watersheds 3-32
Figure 3-9 Reported Pink Salmon distribution in the South Fork Koktuli River, North
Fork Koktuli River, and Upper Talarik Creek watersheds 3-33
Figure 3-10 Rainbow Trout, Dolly Varden, and Arctic Grayling occurrence in the South
Fork Koktuli River, North Fork Koktuli River, and Upper Talarik Creek
watersheds 3-34
Figure 3-11 Bristol Bay salmon genetic lines of divergence linked to ecotypes 3-42
Figure 3-12 Productive habitats for Chinook and Sockeye salmon across the Nushagak
River watershed shift over time 3-43
Recommended Determination
viii
December 2022
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Contents
Figure 3-13 Kvichak River Sockeye Salmon populations 3-44
Figure 3-14 Seasonal catch plus escapement of Sockeye Salmon for each genetically
distinct stock in Bristol Bay, Alaska, 2012-2021 3-47
Figure 3-15 Reporting group affiliation for 146 Sockeye Salmon populations in Bristol
Bay 3-49
Figure 3-16 Subsistence harvest and harvest-effort areas for salmon and other fishes
in the Nushagak and Kvichak River watersheds 3-57
Figure 3-17 Popular areas for recreational fishing in the Nushagak and Kvichak River
watersheds 3-62
Figure 3-18 Streams, rivers, lakes and documented salmon use in the South Fork
Koktuli River, North Fork Koktuli River, and Upper Talarik Creek
watersheds near the Pebble deposit 3-66
Figure 4-1 Mine site area fish distribution 4-8
Figure 4-2 Streams, rivers, and lakes with documented salmon use overlain with the
Pebble 2020 Mine Plan 4-9
Figure 4-3 Streams, rivers, and lakes with documented salmon use in the South Fork
Koktuli River, North Fork Koktuli River, and Upper Talarik Creek
watersheds, downstream of the Pebble 2020 Mine Plan 4-16
Figure 4-4 Reported occurrence of Arctic Grayling, Rainbow Trout, and Dolly Varden
in the South Fork Koktuli River, North Fork Koktuli River, and Upper
Talarik Creek watersheds, downstream of the Pebble 2020 Mine Plan 4-17
Figure 4-5 Reported occurrence of other resident fish species in the South Fork
Koktuli River, North Fork Koktuli River, and Upper Talarik Creek
watersheds, downstream of the Pebble 2020 Mine Plan 4-18
Figure 4-6 Reported occurrence of Arctic Grayling, Rainbow Trout, and Dolly Varden
overlain with the Pebble 2020 Mine Plan 4-19
Figure 4-7 Reported occurrence of other resident fish species overlain with the
Pebble 2020 Mine Plan 4-20
Figure 4-8 Streams, wetlands, and ponds lost under the Pebble 2020 Mine Plan 4-24
Figure 4-9 Streams and rivers with documented salmon use that would experience
streamflow alterations greater than 20 percent of baseline average
monthly streamflows as a result of the Pebble 2020 Mine Plan 4-43
Figure 4-10 Streams and rivers with occurrence of Arctic Grayling, Rainbow Trout,
and Dolly Varden that would experience streamflow changes as a result of
the Pebble 2020 Mine Plan 4-52
Figure 4-11 Streams and rivers with occurrence of other resident fish species that
would experience streamflow changes as a result of the Pebble 2020 Mine
Plan 4-53
Figure 4-12 Mine site cumulative impacts under the Expanded Mine Scenario 4-66
Figure 4-13 Streams, rivers, and lakes with documented salmon use overlain with the
footprints of the Pebble 2020 Mine Plan and the Expanded Mine Scenario 4-68
Figure 4-14 Streams, rivers, and lakes with documented salmon use in the South Fork
Koktuli River, North Fork Koktuli River, and Upper Talarik Creek
watersheds, downstream of the Pebble 2020 Mine Plan and Expanded
Mine Scenario 4-69
Recommended Determination ¦ December 2022
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Contents
Figure 4-15 Reported Arctic Grayling, Rainbow Trout, and Dolly Varden occurrence
overlain with the footprints of the Pebble 2020 Mine Plan and the
Expanded Mine Scenario 4-72
Figure 4-16 Reported occurrence of other resident fish species overlain with the
footprints of the Pebble 2020 Mine Plan and the Expanded Mine Scenario 4-73
Figure 4-17 Reported Arctic Grayling, Rainbow Trout, and Dolly Varden occurrence in
the South Fork Koktuli River, North Fork Koktuli River, and Upper Talarik
Creek watersheds, downstream of the Pebble 2020 Mine Plan and
Expanded Mine Scenario 4-74
Figure 4-18 Reported occurrence of other resident fish species in the South Fork
Koktuli River, North Fork Koktuli River, and Upper Talarik Creek
watersheds, downstream of the Pebble 2020 Mine Plan and Expanded
Mine Scenario 4-75
Figure 4-19 Proposed Koktuli Conservation Area 4-84
Figure 5-1 The Defined Area for Prohibition at the 2020 Mine Plan mine site 5-4
Figure 5-2 The Defined Area for Restriction and Defined Area for Prohibition overlain
on wetlands from the National Wetlands Inventory 5-9
Figure 5-3 The Defined Area for Restriction and Defined Area for Prohibition overlain
on streams and waterbodies from the National Hydrography Dataset 5-10
Figure 6-1 Modeled extent of elevated metals downstream of pyritic tailings release 6-11
Figure 6-2 Subsistence use intensity for salmon, other fishes, wildlife, and waterfowl
within the Nushagak and Kvichak River watersheds 6-18
Recommended Determination
x
December 2022
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AAC
ADEC
ADF&G
ADNR
AFFI
ANCSA
ANILCA
AS
ASA
AWC
BBA
BBAP
BBMA
CAA
CEQ
CFR
CILEA
CMP
CWA
DEIS
EIS
EPA
FEIS
FMEA
FR
HUC
ITEK
LEDPA
MCO
ML
MDN
MOA
NDM
NEPA
NFK
NHD
NMFS
NPS
NWI
PAG
PLP
RAP
RFI
ROD
Contents
Acronyms and Abbreviations
Alaska Administrative Code
Alaska Department of Environmental Conservation
Alaska Department of Fish and Game
Alaska Department of Natural Resources
Alaska Freshwater Fish Inventory
Alaska Native Claims Settlement Act
Alaska National Interest Lands Conservation Act
Alaska Statute
Alaska Statehood Act
Anadromous Waters Catalog
Bristol Bay Assessment
Bristol Bay Area Plan for State Lands
Bristol Bay Sport Fish Management Area
Clean Air Act
Council on Environmental Quality
Code of Federal Regulations
Cook Inlet Land Exchange Act
Compensatory Mitigation Plan
Clean Water Act
Draft Environmental Impact Statement
Environmental Impact Statement
U.S. Environmental Protection Agency
Final Environmental Impact Statement
Failure Modes Effects Analysis
Federal Register
Hydrologic Unit Code
indigenous traditional ecological knowledge
Least Environmentally Damaging Practicable Alternative
Mineral Closing Order
metal leaching
marine-derived nutrients
Memorandum of Agreement
Northern Dynasty Minerals, Ltd.
National Environmental Policy Act
North Fork Koktuli River
National Hydrography Dataset
National Marine Fisheries Service
National Park Service
National Wetlands Inventory
potentially acid-generating
Pebble Limited Partnership
Riverscape Analysis Project
Request for Information
Record of Decision
Recommended Determination
xi
December 2022
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Contents
SEC
U.S. Securities and Exchange Commission
Secretary
Secretary of the Army
SFK
South Fork Koktuli River
TEK
traditional ecological knowledge
TSF
tailings storage facility
TSS
total suspended solids
US ACE
U.S. Army Corps of Engineers
U.S.C.
United States Code
USFWS
U.S. Fish and Wildlife Service
USGS
U.S. Geological Survey
UTC
Upper Talarik Creek
WMP
water management pond
WQC
water quality criteria
WTP
water treatment plant
Recommended Determination
xii
December 2022
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Contents
Cover Photo Credits
Main photo: Upper Talarik Creek (Joe Ebersole, USEPA)
Thumbnail 1: Fishing boats at Naknek, Alaska (USEPA)
Thumbnail 2: Sockeye salmon in the Wood River (Thomas Quinn, University of Washington)
Thumbnail 3: Salmon drying at Koliganek (Alan Boraas, Kenai Peninsula College)
Thumbnail 4: Age-0 coho salmon in the Chignik watershed (Jonny Armstrong)
Recommended Determination
xiii
December 2022
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The U.S. Environmental Protection Agency (EPA) Region 10 is recommending to prohibit and restrict the
use of certain waters in the Bristol Bay watershed as a disposal site for the discharge of dredged or fill
material associated with mining at the Pebble deposit, a large ore body in southwest Alaska. EPA Region
10 is exercising its authority under Section 404(c) of the Clean Water Act (CWA) (Box ES-1) and its
implementing regulations at 40 Code of Federal Regulations (CFR) Part 231 because of the unacceptable
adverse effects on anadromous1 fishery areas in the Bristol Bay watershed that would be likely to result
from discharges of dredged or fill material associated with such mining. Development of a mine at the
Pebble deposit and such a mine's potential effects on aquatic resources have been the subject of study
for nearly two decades; this recommended determination is based on this extensive record of scientific
and technical information. The scope of this recommended determination applies only to specified
discharges of dredged or fill material associated with mining the Pebble deposit.
Alaska's Bristol Bay watershed (Figure ES-1) is an area of unparalleled ecological value, boasting salmon
diversity and productivity unrivaled anywhere in North America. The Bristol Bay watershed provides
intact, connected habitats—from headwaters to ocean—that support abundant, genetically diverse wild
Pacific salmon populations. These salmon populations, in turn, help to maintain the productivity of the
entire ecosystem, including numerous other fish and wildlife species. The region's salmon resources have
supported Alaska Native cultures for thousands of years and continue to support one of the last intact
salmon-based cultures in the world. Together, the Bristol Bay watershed's undisturbed aquatic habitats
and productive salmon populations create this globally significant ecological and cultural resource.
The streams, wetlands, and other aquatic resources of the Bristol Bay watershed also provide the
foundation for world-class, economically important commercial and sport fisheries for salmon and other
fishes. The Bristol Bay watershed supports the world's largest runs of Sockeye Salmon, producing
approximately half of the world's Sockeye Salmon. These Sockeye Salmon represent the most abundant
and diverse populations of this species remaining in the United States. Bristol Bay's Chinook Salmon
runs are also frequently at or near the world's largest, and the region also supports significant Coho,
Chum, and Pink salmon populations. Because no hatchery fishes are raised or released in the watershed,
Bristol Bay's salmon populations are entirely wild and self-sustaining. Bristol Bay is remarkable as one
of the last places on Earth with such bountiful and sustainable harvests of wild salmon. One of the main
factors leading to the success of this fishery is the fact that its diverse aquatic habitats are largely
untouched and pristine, unlike the waters that support many other salmon fisheries worldwide.
1 Anadromous fishes hatch in freshwater habitats, migrate to sea for a period of relatively rapid growth, and then
return to freshwater habitats to spawn. For the purposes of this recommended determination, "anadromous fishes"
refers only to Coho or Silver salmon (Oncorhynchus kisutch), Chinook or King salmon [0. tshawytscha), Sockeye or
Red salmon [O. nerka), Chum or Dog salmon [O. keta), and Pink or Humpback almon [0. gorbuscha).
Recommended Determination
ES-1
December 2022
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Executive Summary
Figure ES-1. The Bristol Bay watershed, composed of the Togiak, Nushagak, Kvichak, Naknek, Egegik, and Ugashik River watersheds and
the North Alaska Peninsula. Only selected towns and villages are shown on this map.
UNITED
^ STATES
~ Approximate Pebble Deposit Location
* Towns and Villages
~ Watershed Boundary
Parks, Refuges, or Preserves
Lake Clark
National Park
and Preserve.
Wood-Tikchil
State Park
Pedro Bj
NUSHAGAK
lliamna Lake
ingham^
Cook Inlet
lanokol
p.- Katmaf*^5*
'"©/•National Park
and Preserve
IAKNEK
Becharof
National
Wildlife
Refuge/
Bristol Bay
Alaska
Peninsulai
i NWR g
'Aniakchak
r National
Preserve
NORT>mLA:
PENINSULA
Alaska
Maritime
NWR .
Izenbek
NWR
Kilometers
Recommended Determination
ES-2
December 2022
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Executive Summary
Roughly 50 to 70 percent of Bristol Bay's Sockeye and large numbers of its Coho, Chinook, Pink, and
Chum salmon are sustainably harvested in subsistence, commercial, and recreational fisheries before
they can return to their natal lakes and streams to spawn. Thus, these salmon resources have significant
nutritional, cultural, economic, and recreational value within and beyond the Bristol Bay region. The
total economic value of the Bristol Bay watershed's salmon resources, including subsistence uses, was
estimated at more than $2.2 billion in 2019 (McKinley Research Group 2021). The Bristol Bay
commercial salmon fishery generates the most significant component of this economic activity, resulting
in 15,000 jobs and an economic benefit of $2.0 billion in 2019, $990 million of which was in Alaska
(McKinley Research Group 2021). Beyond their economic and environmental value, the diverse fishery
and other aquatic and terrestrial resources of the Bristol Bay watershed, which depend upon the
complex of healthy streams, wetlands, and other waters, are irreplaceable because they are inseparable
from the cultures of the native people they support. Section 3 of this recommended determination
provides an overview of the streams, wetlands, and other aquatic resources of the Bristol Bay watershed
and discusses their role in supporting important subsistence, commercial, and recreational fisheries.
The objective of the Olefin Writer Act iCWAi is to restore nnd m;iint;iin the chemic;il. physicfil. find
biological integrity of the nation's waters. Section 404ici of the CWA authorizes the U.S. Environmental
Protection Agency t EPA) to ill prohibit or withdraw the specification of any defined area in waters of the
United States as a disposal site, and <2) restrict, deny, or withdraw the use of any defined area in
waters of the United States for specification as a disposal site whenever it determines, after notice and
opportunity for public hearing, that the discharge of dredged or fill material into the area will have an
unacceptable adverse effect on municipal water supplies, shellfish beds and fishery areas (including
spawning and breeding areas), wildlife, or recreational areas. EPA has used its Section 404ici authority
judiciously, having completed only 13 Section 404(C) actions in the 50 year history of the CWA.
Proposed Mine at the Pebble Deposit
The Pebble deposit, a large, low-grade deposit containing copper-, gold-, and molybdenum-bearing
minerals, is located at the headwaters of the pristine Bristol Bay watershed. The Pebble deposit
underlies portions of the South Fork Koktuli River (SFK), North Fork Koktuli River (NFK), and Upper
Talarik Creek (UTC) watersheds. The SFK, NFK, and UTC drain to two of the largest rivers in the Bristol
Bay watershed, the Nushagak and Kvichak Rivers (Figure ES-2).
Recommended Determination 2 December 2022
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Executive Summary
Figure ES-2. Major water bodies within the Nushagak and Kvichak River watersheds.
Lake Clark
National Park
and Preserve
Wood-Tikchik
State Park
Port Alsworth
Rive/-
NUSHAGAK
'Nondalton
Creek
Pedro Bai
J
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Executive Summary
Since 2001, Northern Dynasty Minerals Ltd. (NDM) and subsequently the Pebble Limited Partnership
(PLP)2 have been conducting data collection and analysis as part of efforts to pursue the development of
a large-scale mine at the Pebble deposit. Construction and operation of a mine at the Pebble deposit
would necessitate the discharge of dredged or fill material into wetlands, streams, and other waters of
the United States and would, therefore, require a CWA Section 404 permit from the U.S. Army Corps of
Engineers (USACE). In December 2017, PLP submitted a CWA Section 404 permit application to USACE
to develop a mine at the Pebble deposit, which triggered the development of an Environmental Impact
Statement (EIS) pursuant to the National Environmental Policy Act (NEPA). In response to the Section
404 permit review/NEPA review process, PLP submitted a revised permit application in June 2020 (the
2020 Mine Plan) (PLP 2020b).
In the 2020 Mine Plan, PLP proposes to develop the Pebble deposit as a surface mine at which 1.3 billion
tons of ore would be mined over 20 years. The project consists of four primary elements: (1) the mine
site situated in the SFK, NFK, and UTC watersheds (Figure ES-3); (2) the Diamond Point port; (3) the
transportation corridor, including concentrate and water return pipelines; and (4) the natural gas
pipeline and fiber optic cable. The first element, a fully developed mine site, would include an open pit,
bulk tailings storage facility (TSF), pyritic TSF, a 270-megawatt power plant, water management ponds
(WMPs), water treatment plants (WTPs), milling and processing facilities, and supporting infrastructure
(Figure ES-4). Under the 2020 Mine Plan, PLP would progress through four distinct mine phases:
construction, operations (also referred to as production), closure, and post-closure. The construction
period would last approximately four years, followed by 20 years of operation. Closure, including
physical reclamation of the mine site, is projected to take approximately 20 years. Post-closure
activities, including long-term water management and monitoring, would last for centuries (USACE
2020a). The potential direct and indirect impacts from construction and operation of the 2020 Mine
Plan on streams, wetlands, and other waters across the mine site (Figure ES-5) have been evaluated in
detail.
On July 24, 2020, USACE published a Notice of Availability for the Final EIS (FEIS) in the Federal Register
(USACE 2020a), and on November 20, 2020, USACE issued its Record of Decision (ROD) denying PLP's
CWA Section 404 permit application on the basis that the 2020 Mine Plan would not comply with the
CWA Section 404(b)(1) Guidelines and would be contrary to the public interest (USACE 2020b). By
letter dated November 25, 2020, USACE notified PLP that the proposed project failed to comply with the
CWA Section 404(b)(1) Guidelines because, even after consideration of proposed mitigation measures,
"the proposed project would cause unavoidable adverse impacts to aquatic resources which would
result in Significant Degradation to aquatic resources."
On January 19, 2021, PLP filed a request for an appeal of the USACE permit denial with USACE. USACE
accepted the appeal on February 25, 2021, and review of the appeal is ongoing.
2 PLP was created in 2007 by co-owners NDM and Anglo American PLC to design, permit, construct, and operate a
long-life mine at the Pebble deposit (Ghaffari et al. 2011). In 2013, NDM acquired Anglo American's interest in PLP,
and NDM now holds a 100 percent interest in PLP (Kalanchey et al. 2021).
Recommended Determination
ES-5
December 2022
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Executive Summary
Figure ES-3. Mine site hydrography. Figure 2-1 from PLP's June 8, 2020, Clean Water Act Section 404 permit application (PLP 2020b).
Main Water
Management Pond
North Fork Koktuli
Watershed
TSF
Laydown
Upper Talarik Creek
Watershed
Bulk Tailings\
Storage Cell
Pyritic Tailings and
PAG Waste Rock
Storage Facility
MINESITEU ^
ACCESS ROADf
North Fork K°
South Fork Koktuli
Watershed
°*tuli Ri'
lliamna
Airfield
liiamna
Newhalen
PLP_PD_2_1 _Mi neSiteHydrography_Alt3.
FIGURE 2-1
Mine Site Hydrography
Bulk Tailings Storage Cell
Water Managment Pond
TSF Laydown
Pyritic Tailings and PAG Waste Rock Storage
Facility
Open Pit
Overburden Stockpiles
Mill Site Process Plant
Quarry
03 Watershed Boundary
Access Road
Natural Gas & Concentrate Pipelines
Township Boundary
lliamna Lake
Recommended Determination
ES-6
December 2022
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Executive Summary
Figure ES-4. Mine site map. Figure 1-4 from PLP's June 8, 2020, Clean Water Act Section 404 permit application (PLP 2020b).
Sediment
Pond
Growth
Medium
Potable Water
Well Field
Stockpile
Sediment
Pond
Sediment
Pond
Main Water
Management Pond
Mill Camp and
Administration Buildings
-Container Yard
Concentrate Process
PumpHo^e-"— Plant
. Power Plant
Seepage Collection Pond —
Seepage
| Collection
\ System
Landfl
Incin
II and
irator
Concentrate and
Natural Gas Pipelines
Crusher and »
Conveyor ,
Truck Shop Pad
Quarry A-
Mill Site
Laydown Area
TSF Overburden
Stockpile
TSF Laydown
PAG Tailings
and Waste Rock
Storage Facility
Quarry B
Bulk Tailings
Storage Facility
Quarry C
¦mbankment'
Explosive
Storage
Pad
Growth
Medium
Stockpile
QuarryB
Open Pit Water
Management Pond
Sediment
Pond
Open Pit
Overburden-
Stockpile
Sediment
Pond
Sediment
Pond
WTP 1
TSF South
Embankment
Seepage
Collection'
System
Seepage
Recycle
Pond
Sedimenl
Pond
FIGURE 1-4
Mine Site Map
Mine Site Footprint
££ Haul/Service/Access Road
Mine Site Access Road
---¦ Concentrate & Natural Gas Pipelines
50' Contour (Existing)
~ Township Boundary
Section Boundary
T 3S R 35W
o—^^=^^5M"eS
Scale 1:46,000
Alaska State Plane Zone 5 (units feet)
1983 North American Datum
Recommended Determination
ES-7
December 2022
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Executive Summary
Figure ES-5. Mine site analysis area for wetlands and other waters. Figure 4.22-1 from the FEIS (USAGE 2020a: Section 4.22).
US Army Corps
of Engineers
PEBBLE PROJECT EIS
ANALYSIS AREA FOR INDIRECT IMPACTS
OF FRAGMENTATION ON WETLANDS
AND OTHER WATERS
FIGURE 4.22-1
Miles
Fragmented Wetland Area
[J Mine Site Direct Impacts
^ Collection Ditch
^ Diversion Channel
NWI Classes
Aquatic Bed
( ) Herbaceous
Broad Leaved Deciduous Shrubs
Deciduous Forest
Evergreen Shrubs
Ponds
Lakes
Rivers/Streams (Intermittent)
Rivers/Streams (Perennial)
v Wetland/Upland Mosaic
Uplands/Mapped Wetlands Extent
Watershed
* Collection ditch and diversion channel
locations are approximate and based on
the Pebble Mine Site Operations Water
Management Plan (Knight Piesold 2018a)
Sources: PLP 2019-RFI116; PLP 2019 RFI-153
Recommended Determination
ES-8
December 2022
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Executive Summary
The USACE permit denial addresses only PLP's specific permit application for the 2020 Mine Plan; it
does not address other future plans to mine the Pebble deposit that would have adverse effects the same
as, or similar or greater in nature and magnitude to the 2020 Mine Plan. Information regarding the
Pebble deposit and the 2020 Mine Plan can be found in Section 2 of this recommended determination.
2014 Proposed Determination
For more than a decade, Alaska Native communities in the Bristol Bay watershed; subsistence,
commercial, and recreational fishing interests; conservation groups; and others have raised concerns
about the potential impacts a large-scale mine at the Pebble deposit could have on the region's socially,
ecologically, and economically important fishery areas. Starting in May 2010, these groups and others
began requesting that EPA use its CWA Section 404(c) authority to protect the region's fishery areas. In
February 2011, EPA decided to conduct an ecological risk assessment before considering any additional
steps. In January 2014, after three years of study, two rounds of public comment, and independent,
external peer review, EPA released its Assessment of Potential Mining Impacts on Salmon Ecosystems of
Bristol Bay, Alaska3 (Bristol Bay Assessment or BBA) (EPA 2014). In July 2014, after careful
consideration of available information, including the findings of the BBA and consultation with PLP and
the State of Alaska, EPA Region 10 published a proposed determination under Section 404(c) of the CWA
to restrict the use of certain waters in the SFK, NFK, and UTC watersheds as disposal sites for dredged or
fill material associated with mining the Pebble deposit (2014 Proposed Determination) for public
comment.
As a result of litigation brought by PLP, EPA Region 10's CWA Section 404(c) review process was halted
in November 2014 until EPA and PLP resolved the case in a May 2017 settlement agreement. As part of
that settlement agreement, EPA Region 10 proposed to withdraw the 2014 Proposed Determination,
and EPA ultimately withdrew the 2014 Proposed Determination in August 2019. In October 2019, 20
tribal, fishing, environmental, and conservation groups challenged EPA's withdrawal of the 2014
Proposed Determination. The ultimate result of the litigation was an October 29, 2021 decision by the
U.S. District Court for the District of Alaska to vacate EPA's 2019 decision to withdraw the 2014
Proposed Determination and remand the action to the Agency for reconsideration.
The District Court's vacatur of EPA's 2019 decision to withdraw the 2014 Proposed Determination had
the effect of reinstating the 2014 Proposed Determination and reinitiating EPA's CWA Section 404(c)
review process. The next step in the CWA Section 404(c) review process required the Region 10
Regional Administrator to decide whether to withdraw the 2014 Proposed Determination or prepare a
recommended determination within 30 days. On November 23, 2021, EPA Region 10 published in the
Federal Register a notice extending the applicable time requirements through May 31, 2022, to provide
sufficient time to consider available information and determine the appropriate next step in the CWA
3 For more information about EPA's efforts in Bristol Bay or copies of the Bristol Bay Assessment, see
http://www.epa.gov/bristolbay.
Recommended Determination
ES-9
December 2022
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Executive Summary
Section 404(c) review process. In its notice, EPA concluded that it should consider information that had
become available since EPA issued the 2014 Proposed Determination. Information regarding the 2014
Proposed Determination and the history of EPA's work in the Bristol Bay watershed can be found in
Section 2 of this recommended determination.
2022 Proposed Determination
To determine the appropriate next step in this CWA Section 404(c) process, EPA Region 10 considered a
wide array of information that had become available since it issued the 2014 Proposed Determination,
including the following:
• More than 670,000 public comments submitted to EPA Region 10 in response to the 2014 Proposed
Determination.
• PLP's CWA Section 404 permit application, including the 2020 Mine Plan (PLP 2020b).
• USACE's FEIS evaluating the 2020 Mine Plan, including the FEIS appendices, technical support
documents, and references (USACE 2020a).
• EPA's and the U.S. Fish and Wildlife Service's 12-week coordination process with USACE in Spring
2020 to evaluate PLP's proposed project for compliance with the CWA Section 404(b)(1) Guidelines.
• USACE's ROD denying PLP's CWA Section 404 permit application for the 2020 Mine Plan, including
the ROD supporting documents (USACE 2020b).
• NDM's Pebble Project Preliminary Economic Assessment dated September 9, 2021 (Kalanchey et al.
2021).
• Updated data regarding fishery resources in the Bristol Bay watershed.
• New scientific and technical publications.
In January 2022, consistent with its regulatory procedures for proposed determinations at 40 CFR
231.3(a), EPA Region 10 notified USACE, Alaska Department of Natural Resources (ADNR), PLP, Pebble
East Claims Corporation, Pebble West Claims Corporation, and Chuchuna Minerals4 (the Parties) of EPA
Region 10's intention to issue a revised proposed determination because, based on a review of
information available to that date, it continued to believe that the discharge of dredged or fill material
associated with mining the Pebble deposit could result in unacceptable adverse effects on fishery areas.
EPA Region 10 provided the Parties with an opportunity to submit information that demonstrated that
no unacceptable adverse effects would result from discharges associated with mining the Pebble deposit
or that actions could be taken to prevent unacceptable adverse effects on fishery areas.
4 EPA Region 10 notified Chuchuna Minerals because USACE's FEIS for the 2020 Mine Plan indicates that it is
reasonably foreseeable for discharges associated with mining the Pebble deposit to expand in the future into
portions of areas where Chuchuna Minerals holds mining claims.
Recommended Determination
ES-10
December 2022
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Executive Summary
ADNR, PLP, and Chuchuna Minerals submitted information asserting legal, policy, scientific, and
technical issues. This information did not demonstrate to the satisfaction of EPA Region 10 that no
unacceptable adverse effects would occur as a result of the discharge of dredged or fill material
associated with mining the Pebble deposit (Section 2.2.2). Thus, EPA Region 10 decided that the
appropriate next step in this CWA Section 404(c) process was the publication of a revised proposed
determination (the 2022 Proposed Determination).
In May 2022, EPA Region 10 published in the Federal Register a notice of availability for the 2022
Proposed Determination under Section 404(c) of the CWA to prohibit and restrict the use of certain
waters in the SFK, NFK, and UTC watersheds as disposal sites for the discharge of dredged or fill
material associated with mining the Pebble deposit (87 FR 32021, May 26, 2022). The notice started a
public comment period ending on July 5, 2022. On June 16 and 17, 2022, EPA Region 10 held three
public hearings on the 2022 Proposed Determination: two in-person hearings in the Bristol Bay region
(in Dillingham and Iliamna) and one virtual hearing. More than 186 people participated in the three
hearings, 111 of whom provided oral statements.
EPA Region 10 received requests to extend the public comment period, as well as requests not to extend
the public comment period. EPA Region 10 considered each of these requests and found good cause
existed pursuant to 40 CFR 231.8 to extend the public comment period through September 6, 2022 (87
FR 39091, June 30, 2022).
On September 6, 2022, EPA Region 10 published in the Federal Register a notice to extend the period for
the EPA Region 10 Regional Administrator to evaluate public comments. According to the notice, EPA
found good cause existed pursuant to 40 CFR 231.8 to extend the time period provided in 40 CFR
231.5(a) to either withdraw the proposed determination or to prepare a recommended determination
through no later than December 2, 2022, to help ensure full consideration of the extensive
administrative record including all public comments (87 FR 54498, September 6, 2022). In addition to
the testimony taken at the hearings, EPA Region 10 received more than 582,000 written comments
during the public comment period.
The Recommended Determination
EPA Region 10 completed its review of the extensive administrative record, including all public
comments, and has determined that the discharge of dredged or fill material associated with mining at
the Pebble deposit would be likely to result in unacceptable adverse effects on anadromous fishery
areas. Section 4 of this recommended determination provides the basis for EPA Region 10's findings
regarding unacceptable adverse effects on anadromous fishery areas.
As demonstrated in the FEIS and ROD, construction and routine operation of the mine proposed in the
2020 Mine Plan would result in the discharge of dredged or fill material into waters of the United States,
including streams, wetlands, lakes, and ponds overlying the Pebble deposit and within adjacent
watersheds. The direct effects (i.e., resulting from placement of fill in aquatic habitats) and certain
Recommended Determination
ES-11
December 2022
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Executive Summary
secondary effects of such discharges (i.e., associated with a discharge of dredged or fill material, but not
resulting from the actual placement of such material) would result in the total loss of aquatic habitats
important to anadromous fishes. These losses are the result of the construction and routine operation of
the various components of the mine site, including the open pit, bulk TSF, pyritic TSF, power plant,
WMPs, WTPs, milling/processing facilities, and supporting infrastructure. According to the FEIS and
ROD, discharges of dredged or fill material to construct and operate the mine site proposed in the 2020
Mine Plan would result in the total loss of approximately 99.7 miles (160.5 km) of stream habitat,
representing approximately 8.5 miles (13.7 km) of anadromous fish streams and 91 miles (147 km) of
additional streams that support anadromous fish streams. Such discharges of dredged or fill material
also would result in the total loss of approximately 2,108 acres (8.5 km2) of wetlands and other waters
in the SFK and NFK watersheds that support anadromous fish streams.
Additional secondary effects of the proposed discharges of dredged or fill material at the mine site
would degrade anadromous fishery areas downstream of the mine site. Specifically, the stream, wetland,
and other aquatic resource losses from the footprint of the 2020 Mine Plan would reverberate
downstream, depriving downstream anadromous fish habitats of nutrients, groundwater inputs, and
other ecological subsidies from lost upstream aquatic resources. Further, streamflow alterations from
water capture, withdrawal, storage, treatment, or release at the mine site are another secondary effect of
the discharge of dredged or fill material associated with the construction and routine operation of the
2020 Mine Plan. Such streamflow alterations would adversely affect approximately 29 miles (46.7 km)
of anadromous fish streams downstream of the mine site due to greater than 20 percent changes in
average monthly streamflow.5 These streamflow alterations would result in major changes in ecosystem
structure and function and would reduce both the extent and quality of anadromous fish habitat
downstream of the mine. As recognized in the FEIS, all instances of complete loss of aquatic habitat and
most impairment to fish habitat function would be permanent and "no other wild salmon fishery in the
world exists in conjunction with an active mine of this size" (USACE 2020a: Page 4.6-9).
Although Alaska has many streams and wetlands that support salmon, individual streams, stream
reaches, wetlands, lakes, and ponds play a critical role in supporting individual salmon populations and
protecting the genetic diversity of Bristol Bay's wild salmon populations. The diverse array of watershed
features across the region creates and sustains a diversity of aquatic habitats that support multiple
populations of salmon with asynchronous run timings and habitat use patterns (i.e., biocomplexity, after
Hilborn et al. 2003). These population differences are reflected in salmon genetic diversity and
adaptation to local conditions within Bristol Bay's component watersheds (e.g., Quinn et al. 2012) and
provide stability to the overall system (Schindler et al. 2010). Impacts of the 2020 Mine Plan are
concentrated in the SFK and NFK watersheds, which are a part of the Nushagak River watershed. Recent
analysis specific to the Nushagak River watershed underscores the important role that the streams,
5 Streamflow alterations would vary seasonally. Streamflow reductions exceeding 20 percent of average monthly
streamflow would occur in at least one month per year in at least 13.1 miles (21.4 km) of anadromous fish streams
downstream of the mine site, and operation of the 2020 Mine Plan would increase streamflow by more than 20
percent of baseline average monthly streamflow in at least 25.7 miles (41.3 km) of downstream anadromous fish
streams due to WTP discharges.
Recommended Determination
ES-12
December 2022
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Executive Summary
wetlands, lakes, and ponds across the entire Nushagak River watershed, including those that would be
adversely affected by the 2020 Mine Plan, play in stabilizing the Nushagak River's productive Sockeye
and Chinook salmon fisheries (Brennan et al. 2019). Similarly, both the Koktuli River (the SFK and NFK
are tributaries to the Koktuli River) and UTC have been documented to support genetically distinct
populations of Sockeye Salmon (Dann et al. 2012, Shedd et al. 2016, Dann et al. 2018). Loss of salmon
habitats and associated salmon diversity in the SFK, NFK, and UTC watersheds would erode both the
habitat complexity and biocomplexity that help buffer these populations from sudden and extreme
changes in abundance and ultimately maintain their productivity.
In addition to supporting genetically distinct salmon populations, the streams and wetlands draining the
Pebble deposit area provide key habitat for numerous other fish species and supply water,
invertebrates, organic matter, and other resources to downstream waters (Meyer et al. 2007, Colvin et
al. 2019, Koenig et al. 2019). This is particularly true in dendritic stream networks like the SFK, NFK, and
UTC systems, which have a high density of headwater streams. As a result, headwater streams and
wetlands play a vital role in maintaining diverse, abundant anadromous fish populations—both by
providing important fish habitat and supplying the energy and other resources needed to support
anadromous fishes in connected downstream habitats.
EPA Region 10 has determined the discharge of dredged or fill material for the construction and routine
operation of the 2020 Mine Plan would be likely to result in unacceptable adverse effects on
anadromous fishery areas in the SFK and NFK watersheds. In this regard, EPA makes four independent
unacceptability findings, each of which is based on one or more factors, including the large amount of
permanent loss of anadromous fish habitat (including spawning and breeding areas); the particular
importance of the permanently lost habitat for juvenile Coho and Chinook salmon; the degradation of
additional downstream spawning and rearing habitat for Coho, Chinook, and Sockeye salmon due to the
loss of ecological subsidies provided by eliminated streams, wetlands, and other waters; and the
resulting erosion of habitat complexity and biocomplexity within the SFK and NFK watersheds, both of
which are key to the abundance and stability of salmon populations within these watersheds. EPA
Region 10 has also determined that discharges of dredged or fill material associated with the
development of the Pebble deposit anywhere at the mine site that would result in the same or greater
levels of loss or streamflow changes as the 2020 Mine Plan also would be likely to have unacceptable
adverse effects on anadromous fishery areas, because such discharges would involve the same aquatic
resources characterized as part of the evaluation of the 2020 Mine Plan. These conclusions support the
recommended prohibition described in Section 5.1 of this recommended determination.
Further, EPA Region 10 has determined the discharge of dredged or fill material for the construction and
routine operation of a mine at the Pebble deposit anywhere in the SFK, NFK, and UTC watersheds would
be likely to result in unacceptable adverse effects on anadromous fishery areas if the effects of such
discharges are similar or greater in nature and magnitude to the adverse effects of the 2020 Mine Plan.
In this regard, EPA makes four independent unacceptability findings, each of which is based on one or
more factors, including the pristine condition and ecological importance of anadromous habitat
throughout the SFK, NFK, and UTC watersheds; how aquatic habitats across these three watersheds
Recommended Determination
ES-13
December 2022
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Executive Summary
function similarly to support productive anadromous fishery areas; the large amount of permanent loss
of anadromous fish habitat; the degradation of additional downstream spawning and rearing habitat for
Coho, Chinook, and Sockeye salmon due to the loss of ecological subsidies provided by the eliminated
streams, wetlands, and other waters; and the resulting erosion of habitat complexity and biocomplexity
within the SFK, NFK, and UTC watersheds, both of which are key to the abundance and stability of
salmon populations within these watersheds. This conclusion supports the recommended restriction
described in Section 5.2 of this recommended determination.
Based on the foregoing, the EPA Region 10 Regional Administrator determined that the appropriate next
step in this CWA Section 404(c) review process is to transmit this recommended determination, along
with the administrative record, to EPA's Assistant Administrator for Water for review and final action.
Overview of Prohibition and Restriction in the Recommended
Determination
This recommended determination includes two parts: a recommended prohibition and a recommended
restriction, which are described in more detail in Sections 5.1 and 5.2, respectively.
Recommended Prohibition
The EPA Region 10 Regional Administrator has determined that discharges of dredged or fill material
for the construction and routine operation of the mine at the Pebble deposit identified in the 2020 Mine
Plan (PLP 2020b) would be likely to result in unacceptable adverse effects on anadromous fishery areas
in the SFK and NFK watersheds. Based on information in PLP's CWA Section 404 permit application, the
FEIS, and the ROD, such discharges would result in the following aquatic resource losses and streamflow
changes:
• The loss of approximately 8.5 miles (13.7 km) of documented anadromous fish streams (Section
4.2.1).
• The loss of approximately 91 miles (147 km) of additional streams that support anadromous fish
streams (Section 4.2.2).
• The loss of approximately 2,108 acres (8.5 km2) of wetlands and other waters that support
anadromous fish streams (Section 4.2.3).
• Adverse impacts on approximately 29 additional miles (46.7 km) of anadromous fish streams
resulting from greater than 20 percent changes in average monthly streamflow (Section 4.2.4).
EPA Region 10 has also determined that discharges of dredged or fill material associated with the
development of the Pebble deposit anywhere at the mine site that would result in the same or greater
levels of loss or streamflow changes as the 2020 Mine Plan also would be likely to have unacceptable
adverse effects on anadromous fishery areas, because such discharges would involve the same aquatic
resources characterized as part of the evaluation of the 2020 Mine Plan.
Recommended Determination
ES-14
December 2022
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Executive Summary
Sections 4.2.1 through 4.2.4 describe the basis for EPA Region 10's determination that each of the above
impacts independently would be likely to result in unacceptable adverse effects on anadromous fishery
areas (including spawning and breeding areas).
Accordingly, the Regional Administrator recommends that EPA prohibit the specification of waters of
the United States within the Defined Area for Prohibition (Figures ES-6, ES-7, and ES-8), as disposal sites
for the discharge of dredged or fill material for the construction and routine operation of the 2020 Mine
Plan. For purposes of the prohibition, the 2020 Mine Plan is (1) the mine plan described in PLP's June 8,
2020 CWA Section 404 permit application (PLP 2020b) and the FEIS (USACE 2020a); and (2) future
proposals to construct and operate a mine to develop the Pebble deposit with discharges of dredged or
fill material in the Defined Area for Prohibition that would result in the same or greater levels of loss or
streamflow changes as the 2020 Mine Plan. Because each of the losses or streamflow changes described
in Sections 4.2.1 through 4.2.4 independently would be likely to result in unacceptable adverse effects
on anadromous fishery areas, proposals that result in any one of these losses or streamflow changes
would be subject to the prohibition.
Recommended Restriction
The Regional Administrator has determined that discharges of dredged or fill material associated with
future plans to mine the Pebble deposit would be likely to result in unacceptable adverse effects on
anadromous fishery areas (including spawning and breeding areas) anywhere in the SFK, NFK, and UTC
watersheds if the adverse effects of such discharges are similar or greater in nature6 and magnitude7 to
the adverse effects of the 2020 Mine Plan described in Sections 4.2.1 through 4.2.4 of this recommended
determination.
Accordingly, the Regional Administrator recommends restricting the use of waters of the United States
within the Defined Area for Restriction (Figures ES-7 and ES-8) for specification as disposal sites for the
discharge of dredged or fill material associated with future proposals to construct and operate a mine to
develop the Pebble deposit that would either individually or cumulatively result in adverse effects
similar or greater in nature and magnitude to those described in Sections 4.2.1 through 4.2.4 of this
recommended determination. Because each of the losses or streamflow changes described in Sections
4.2.1 through 4.2.4 independently would be likely to result in unacceptable adverse effects on
anadromous fishery areas, proposals that result in any one of these losses or streamflow changes would
be subject to the restriction. To the extent that such future discharges would be subject to the
prohibition, the restriction would not apply.
6 Nature means type or main characteristic (see Cambridge Dictionary available at:
https://dictionary.cambridge.org/us/dictionary/english/nature).
1 Magnitude refers to size or importance (see Cambridge Dictionary available at:
https://dictionary.cambridge.org/us/dictionary/english/magnitude).
Recommended Determination
ES-15
December 2022
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Executive Summary
Figure ES-6. The Defined Area for Prohibition at the 2020 Mine Plan mine site. Figure based on information from PLP (2020b), USGS
(2021a), and USGS (2021b).
Recommended Determination
ES-16
December 2022
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Executive Summary
Figure ES-7. The Defined Area for Restriction and the defined area for prohibition overlain on
wetlands from the National Wetlands Inventory (USFWS 2021).
NUSHAGAK
KVICHAK
Pebble Deposit
Defined Area for
Restriction
Defined Area for
Prohibition
2020 Mine Footprint
NWI Wetlands
Nushagak and Kvichak
Watersheds
South Fork Koktuli, North
Fork Koktuli, and Upper
Talarik Creek Watersheds
N
A
A
0 3
6
j_|
Miles
LO —
o —
10
i_l
Kilometers
Recommended Determination
ES-17
December 2022
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Executive Summary
Figure ES-8. The Defined Area for Restriction and the defined area for prohibition overlain on
streams and waterbodies from the National Hydrography Dataset (USGS 2021b).
NUSHAGAK
KVICHAK
Anadromous Fish Streams
Pebble Deposit
Defined Area for
Restriction
Defined Area for
Prohibition
2020 Mine Footprint
NHD Streams and
Waterbodies
Nushagak and Kvichak
Watersheds
South Fork Koktuli, North
Fork Koktuli, and Upper
Talarik Creek Watersheds
0 3 6
1 i i I—J i i i I
Miles
0 5 10
l—I—1—l—I—l—I—l_l
Kilometers
lliamna Lake
Recommended Determination
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December 2022
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Executive Summary
When a Proposal is Not Subject to this Determination
Proposals to discharge dredged or fill material into waters of the United States associated with mining
the Pebble deposit that are not subject to this determination remain subject to all statutory and
regulatory authorities and requirements under CWA Section 404.
In light of the immense and unique economic, social, cultural, and ecological value of the aquatic
resources in the region, including the fishery areas in the SFK, NFK, and UTC watersheds, and their
susceptibility to degradation, EPA will carefully evaluate all future proposals to discharge dredged or fill
material in the region.
Evaluation of Portions of the CWA Section 404(b)(1) Guidelines
EPA's Section 404(c) regulations provide that consideration should be given to the "relevant portions of
the Section 404(b)(1) Guidelines" in evaluating the "unacceptability" of effects (40 CFR 231.2(e)). EPA
Region 10's consideration of the relevant portions of the Section 404(b)(1) Guidelines further confirm
EPA Region 10's unacceptable adverse effects finding.
Specifically, EPA Region 10 has determined that direct and secondary effects of the discharge of dredged
or fill material for the construction and routine operation of the 2020 Mine Plan, as well as discharges
that would result in adverse effects similar or greater in nature and magnitude to the 2020 Mine Plan,
would result in significant degradation under the Section 404(b)(1) Guidelines. These findings are based
on the significantly adverse effects of the discharge of dredged or fill material on special aquatic sites,
life stages of anadromous fishes, anadromous fish habitat, and aquatic ecosystem diversity, productivity,
and stability under the Section 404(b)(1) Guidelines.
Region 10 evaluated PLP's two compensatory mitigation plans and neither plan adequately mitigates
adverse effects described in this recommended determination to an acceptable level. EPA Region 10 also
evaluated additional potential compensation measures for informational purposes. Available
information demonstrates that known compensation measures are unlikely to adequately mitigate
effects described in this recommended determination to an acceptable level. Information regarding
evaluation of the Section 404(b)(1) Guidelines can be found in Section 4.3 of this recommended
determination.
Information about Other Adverse Effects of Concern on
Aquatic Resources
While not a basis for EPA Region 10's recommended determination, EPA Region 10 has identified
additional potential adverse effects of concern on aquatic resources within the SFK, NFK, and UTC
watersheds associated with discharges of dredged or fill material from mining the Pebble deposit and is
presenting this discussion solely for informational purposes. First, adverse effects could result from
accidents and failures, such as a tailings dam failure. Uncertainty exists as to whether severe accidents
Recommended Determination
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December 2022
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Executive Summary
or failures could be prevented over a management horizon of centuries (or in perpetuity), particularly in
such a geographically remote area. If such events were to occur, they would have profound ecological
ramifications. Second, there are potential adverse impacts associated with the ancillary project
components along the transportation corridor and at the Diamond Point port. Third, there are potential
adverse impacts associated with the reasonably foreseeable expansion of the 2020 Mine Plan evaluated
in the FEIS. The FEIS finds that it is reasonably foreseeable that the 2020 Mine Plan would expand in the
future into a plan that would mine approximately 8.6 billion tons of ore over 78 years. The FEIS
estimates that the discharge of dredged or fill material for the construction and operation of this
expanded mine would result in the total loss of approximately 430 miles (6921 km) of streams at the
expanded mine site, representing approximately 43.5 miles (70 km) of anadromous fish streams and
approximately 386 miles (621 km) of additional streams that support anadromous fish streams.
Further, the FEIS estimates that discharges of dredged or fill material to construct and operate the
expanded mine site would also result in the total loss of more than 10,800 acres (43.7 km2) of wetlands
and other waters that support anadromous fish streams. These would represent extraordinary and
unprecedented levels of anadromous fish habitat loss and degradation, dramatically expanding the
unacceptable adverse effects identified for the 2020 Mine Plan. For example, significant additional
anadromous fish habitat losses and degradation in SFK, NFK, and UTC caused by future expansion of the
mine would threaten genetically distinct Sockeye Salmon populations in both the Koktuli River and UTC.
See Section 6 of this recommended determination for a discussion of other concerns and considerations.
Authority and Justification for Undertaking a CWA Section
404(c) Review at this Time
EPA may act "whenever" it makes the required determination under the statute and regulations. The
Agency may use its CWA Section 404(c) authority "at any time," including before a permit application
has been submitted, at any point during the permitting process, and after a permit has been issued (33
U.S.C. 1344(c); 40 CFR 231.1(a), (c); Mingo Logan Coal Co. v. EPA, 714 F.3d 608, 613 (D.C. Cir. 2013)).
Congress enacted CWA Section 404(c) to provide EPA the ultimate authority, if it chooses on a case-by-
case basis, to make decisions regarding specification of disposal sites for dredged and fill material
discharges under CWA Section 404 (Mingo Logan Coal Co. v. EPA, 714 F.3d 608, 612-13 (D.C. Cir. 2013)).
EPA Region 10 has reviewed the available information, including the permitting record, and the record
supports the findings reported in this recommended determination.
By acting now, EPA clarifies its assessment of the effects of discharges of dredged or fill material
associated with the construction and routine operation of the 2020 Mine Plan in light of the importance
of the anadromous fishery areas at issue8 and, therefore, promotes regulatory certainty for all
8 In this recommended determination, EPA Region 10 has concluded that each of the losses or changes to
streamflow identified in Sections 4.2.1 through 4.2.4 independently would be likely to result in unacceptable
adverse effects. That finding is distinguishable from the USACE permit denial, in which USACE reached its
conclusions based on consideration of total project impacts to aquatic resources.
Recommended Determination
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Executive Summary
stakeholders. If EPA acts now, based on an extensive and carefully considered record, EPA, USACE, and
the regulated community can also avoid unnecessary expenditure of resources. The federal government,
the State of Alaska, federally recognized tribal governments, PLP, and many interested stakeholders
have devoted significant resources over many years of engagement and review. Considering the
extensive record, it is not reasonable or necessary to engage in one or more additional multi-year NEPA
and CWA Section 404 processes for future plans9 that propose to discharge dredged or fill material
associated with mining the Pebble deposit in the SFK, NFK, or UTC watersheds that would be likely to
result in effects that are the same as, or similar or greater in nature and magnitude to the effects of the
2020 Mine Plan. Ultimately, recommending the prohibition and restriction now provides the most
effective, transparent, and predictable protection of valuable anadromous fishery areas in the SFK, NFK,
and UTC watersheds against unacceptable adverse effects.
Conclusion
The EPA Region 10 Regional Administrator completed his review of the extensive administrative record,
including all public comments, and has determined that discharges of dredged or fill material into
waters of the United States for the construction and routine operation of the 2020 Mine Plan would be
likely to result in unacceptable adverse effects on anadromous fishery areas (Sections 4.2.1 through
4.2.4 of this recommended determination). The Regional Administrator also has determined that
discharges of dredged or fill material associated with future plans to develop the Pebble deposit would
be likely to result in unacceptable adverse effects on anadromous fishery areas in the SFK, NFK, and UTC
watersheds if the effects of such discharges are similar or greater in nature and magnitude to those of
the 2020 Mine Plan described in Sections 4.2.1 through 4.2.4 of this recommended determination. Based
on these findings, the Regional Administrator recommends prohibiting and restricting the use of certain
waters in the SFK, NFK, and UTC watersheds as disposal sites for the discharge of dredged or fill
material associated with developing the Pebble deposit (Section 5 of this recommended determination).
Accordingly, the Regional Administrator determined that the appropriate next step in this CWA Section
404(c) review process is to transmit this recommended determination, along with the administrative
record, to EPA's Assistant Administrator for Water at EPA Headquarters for review and final action.
EPA's Assistant Administrator for Water will review this recommended determination and the
administrative record, including written public comments received on the 2022 Proposed
Determination, public hearing transcripts, and other information considered by the Regional
Administrator. After reviewing the recommendations of the Regional Administrator, the administrative
record, and any information provided by ADNR, PLP, Chuchuna Minerals, and USACE about their intent
to take corrective action to prevent unacceptable adverse effects, the Assistant Administrator will issue
a final determination affirming, modifying, or rescinding the Regional Administrator's recommended
determination.
9 USACE's denial of PLP's permit application does not address any other plan to mine the Pebble deposit that would
have adverse effects the same as, or similar or greater in nature and magnitude to the 2020 Mine Plan.
Recommended Determination
ES-21
December 2022
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The Clean Water Act (CWA), 33 U.S. Code (U.S.C.) § 1251 et seq., prohibits the discharge of pollutants,
including dredged or fill material, into waters of the United States (including wetlands) except in
compliance with, among other provisions, Section 404 of the CWA, 33 U.S.C. §1344, 33 U.S.C. § 1311.
Section 404(a) of the CWA authorizes the Secretary of the Army (Secretary), acting through the Chief of
Engineers (U.S. Army Corps of Engineers or USACE), to authorize the discharge of dredged or fill
material at specified disposal sites. This authorization is conducted, in part, through the application of
environmental guidelines developed by the U.S. Environmental Protection Agency (EPA), in conjunction
with the Secretary, under Section 404(b) of the CWA. Section 404(c) of the CWA authorizes EPA to
prohibit the specification (including the withdrawal of specification) of any defined area as a disposal
site and to restrict or deny the use of any defined area for specification (including the withdrawal of
specification) as a disposal site whenever it determines, after notice and opportunity for public hearing,
that the discharge of such materials into such area will have an unacceptable adverse effect on municipal
water supplies, shellfish beds and fishery areas (including spawning and breeding areas), wildlife, or
recreational areas.
The procedures for implementation of CWA Section 404(c) are set forth in Title 40 of the Code of
Federal Regulations (CFR) Part 231 and establish a four-step CWA Section 404(c) review process.
• Step i: Initial Notification, If the EPA Regional Administrator has reason to believe, after evaluating
the information available to him, that an unacceptable adverse effect could result from the
specification or use of a defined area for the disposal of dredged or fill material on one or more of
the statutorily listed resources, the Regional Administrator may initiate the CWA Section 404(c)
review process by notifying USACE,10 the owner(s) of record of the site, and the permit applicant (if
any), that he intends to issue a public notice of a proposed determination to prohibit or withdraw
the specification, or to deny, restrict, or withdraw the use for specification, whichever the case may
be, of any defined area as a disposal site. Each of those parties then has 15 days to demonstrate to
the satisfaction of the Regional Administrator that no unacceptable adverse effects will occur, or that
corrective action to prevent an unacceptable adverse effect will be taken.
• Step 2: Proposed Determination, If USACE, the owner(s) of record of the site, and the applicant (if
any) have not demonstrated to the satisfaction of the Regional Administrator that no unacceptable
adverse effects will occur, or USACE has not notified the Regional Administrator to his satisfaction of
its intent to take corrective action to prevent an unacceptable adverse effect, the Regional
10 The state would be notified here if the site is covered by an EPA-approved state program (CWA Section 404(g))
to issue permits for discharges of dredged or fill material at specified sites in waters of the United States (40 CFR
231.3(a)(1)).
Recommended Determination
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Section 1
Introduction
Administrator shall publish notice of a proposed determination in the Federal Register, soliciting
public comment on the proposed determination and offering an opportunity for public hearing.
• Step 3: Recommended Determination, Following a public hearing and close of the comment period,
the Regional Administrator must decide whether to withdraw the proposed determination or
prepare a recommended determination. If the Regional Administrator prepares a recommended
determination, the Regional Administrator must forward the recommended determination and the
administrative record to the Assistant Administrator for Water at EPA Headquarters.11 If the
Regional Administrator decides to withdraw the proposed determination, he must notify the
Assistant Administrator for Water, who may review the withdrawal at her discretion.12
• Step 4: Final Determination, If the Regional Administrator prepares and forwards a recommended
determination to the Assistant Administrator for Water, the Assistant Administrator for Water will
review the recommended determination of the Regional Administrator and the information in the
administrative record. The Assistant Administrator for Water will also consult with USACE, the
owner(s) of record of the site, and the applicant (if any). Following consultation and consideration of
the record, the Assistant Administrator for Water will make the final determination affirming,
modifying, or rescinding the recommended determination.
EPA Region 10 has developed this recommended determination to prohibit and restrict the use of
certain waters in the Bristol Bay watershed as a disposal site for the discharge of dredged or fill material
associated with mining at the Pebble deposit, a large ore body in southwest Alaska. The EPA Region 10
Regional Administrator is exercising his authority under Section 404(c) of the CWA and its
implementing regulations at 40 CFR Part 231 because of the unacceptable adverse effects on
anadromous13 fishery areas in the Bristol Bay watershed that would be likely to result from discharges
of dredged or fill material associated with such mining.
11 In 1984, the EPA Administrator delegated the authority to make final determinations under Section 404(c) to
EPA's national CWA Section 404 program manager, who is the Assistant Administrator for Water. That delegation
remains in effect With regard to EPA's Section 404(c) action for the Pebble deposit area, on March 22, 2019,
Administrator Wheeler delegated to the General Counsel the authority to perform all functions and responsibilities
retained by the Administrator or previously delegated to the Assistant Administrator for Water related to that
action due to the recusals of then Administrator Wheeler and Assistant Administrator for Water David Ross from
participation in matters related to Pebble Mine, which is associated with the Pebble deposit area. The
Administrator rescinded the March 22, 2019 one-time delegation on May 17, 2022, because neither the current
Administrator nor the current Assistant Administrator for Water have such recusals in place. As a result, the 1984
delegation controls and all functions and responsibilities retained by the Administrator related to the Pebble
deposit are delegated to the Assistant Administrator for Water.
12 If within 10 days of notifying the Assistant Administrator for Water of his decision to withdraw the proposed
determination, the Assistant Administrator for Water does not notify the Regional Administrator of her intent to
review such withdrawal, the Regional Administrator shall give public notice of the withdrawal of the proposed
determination. If the Assistant Administrator for Water does decide to review, the Regional Administrator or his
designee shall forward the administrative record to the Assistant Administrator for Water for a final determination.
13 Anadromous fishes are those that hatch in freshwater habitats, migrate to sea for a period of relatively rapid
growth, and then return to freshwater habitats to spawn. For the purposes of this recommended determination,
"anadromous fishes" refers only to Coho or Silver salmon (Oncorhynchus kisutch), Chinook or King salmon (O.
tshawytscha), Sockeye or Red salmon (O. nerka), Chum or Dog salmon (O. keta), and Pink or Humpback salmon
[O. gorbuscha).
Recommended Determination
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Section 1
Introduction
This recommended determination represents Step 3 in the above process. In this recommended
determination, the EPA Region 10 Regional Administrator is recommending to (1) prohibit the
specification of a defined area as a disposal site, and (2) restrict the use of a defined area for
specification as a disposal site because he has determined that discharges of dredged or fill material into
these areas would be likely to result in unacceptable adverse effects on anadromous fishery areas.
This recommended determination is organized as follows.
• Section 2 provides background information on the Pebble deposit, a large, low-grade, porphyry
copper deposit that underlies portions of the South Fork Koktuli River (SFK), North Fork Koktuli
River (NFK), and Upper Talarik Creek (UTC) watersheds; a description of the mine plan developed
by the Pebble Limited Partnership (PLP) in support of its CWA Section 404 permit application (the
2020 Mine Plan); a timeline of key events related to the Pebble deposit; and a summary of EPA
Region 10's actions taken related to CWA Section 404(c) in this case.
• Section 3 provides an overview of the streams, wetlands, and other aquatic resources of the Bristol
Bay watershed and discusses their role in supporting important subsistence, commercial, and
recreational fisheries. It also describes the streams, wetlands, and other aquatic resources of the
SFK, NFK, and UTC watersheds within the Bristol Bay watershed and discusses how they are integral
to maintaining the productivity, integrity, and sustainability of both salmon and non-salmon fishery
resources. This section also describes how salmon population diversity and dynamics interact to
create a portfolio of biological assets resulting in a sustainable fishery.
• Section 4 describes the basis for EPA Region 10's determination that the direct and secondary
effects of the discharge of dredged or fill material associated with construction and routine
operation of the 2020 Mine Plan into certain streams, wetlands, and other aquatic resources of the
SFK, NFK, and UTC watersheds would be likely to result in unacceptable adverse effects on
anadromous fishery areas under EPA's regulations. These unacceptable adverse effects include the
permanent loss and degradation of streams, wetlands, and other aquatic resources that are
important for supporting anadromous fish habitat.
• Section 5 presents the recommended prohibition and the recommended restriction, which are
designed to prevent unacceptable adverse effects on anadromous fishery areas in the SFK, NFK, and
UTC watersheds that would be likely to result from the discharge of dredged or fill material
associated with development of the Pebble deposit.
• Section 6 identifies other concerns and information that, while not the basis for EPA Region 10's
recommended determination, are related to discharges of dredged or fill material associated with
development of the Pebble deposit. Such concerns include potential impacts on subsistence
resources, environmental justice issues, traditional ecological knowledge, as well as potential spills
and failures associated with mine infrastructure at the Pebble deposit. Section 6 also includes other
concerns and considerations related to the potential for discharges of dredged or fill material
associated with development of the Pebble deposit to result in adverse effects on wildlife,
recreation, or public water supplies.
Recommended Determination
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Section 1 Introduction
• Section 7 provides the conclusion for the recommended determination.
• Section 8 lists references cited in the recommended determination.
Recommended Determination
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December 2022
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2.1 Project Description
2.1.1 Overview of the Pebble Deposit
Several known mineral deposits are located in the Nushagak and Kvichak River watersheds (EPA 2014,
USACE 2020a, Kalanchey et al. 2021). The deposit types occurring or likely to occur in the region include
porphyry copper, intrusion-related gold, and copper and iron skarn. The potential for mining
development within these watersheds appears to be greatest for the Pebble deposit since significant
exploration activity has occurred at this deposit for many years, and a significant amount of information
about this deposit is available.
The Pebble deposit is a large, low-grade deposit containing copper-, gold-, and molybdenum-bearing
minerals that underlies portions of the SFK, NFK, and UTC watersheds. The SFK and NFK watersheds are
part of the Nushagak River watershed, and the UTC watershed is part of the Kvichak River watershed
(Figure ES-2). Extraction at the Pebble deposit would involve the creation of a large open pit and the
production of large amounts of waste rock and mine tailings (USACE 2020a).
The Pebble deposit covers an area of at least 1.9 by 2.8 miles and consists of two contiguous segments,
Pebble West and Pebble East. The approximate center of the deposit is about 9.2 miles north-northeast
of Sharp Mountain and 18.7 miles northwest of Iliamna. It covers portions of sections 14 to 16, 20 to 23,
and 26 to 29, T. 3 S., R. 35 W., Seward Meridian.14 The full extent of the Pebble deposit is not yet defined,
but Kalanchey et al. (2021) indicate that the Pebble mineral resource may approach 11 billion tons of
ore.
PLP holds the largest mine claim block in the Nushagak and Kvichak River watersheds. In 2017, PLP
submitted a CWA Section 404 permit application to USACE to develop a mine at the Pebble deposit,
which triggered USACE's development of a Final Environmental Impact Statement (FEIS) pursuant to
the National Environmental Policy Act (NEPA). As discussed in Section 2.2.1, PLP revised its application
during the NEPA and CWA Section 404 review processes, and the final revision (the 2020 Mine Plan)
was submitted to USACE in June 2020.
14 Mine claims may be located by what is known as aliquot part legal description, which is meridian, township,
range, section, quarter section, and if applicable quarter-quarter section. These claims are known as MTRSC
locations, and they are generally located using global positioning system (GPS) latitude and longitude coordinates.
A quarter section location is typically about 160 acres in size, and a quarter-quarter section location is typically 40
acres in size (ADNR 2022a).
Recommended Determination 2 j_ December 2022
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Section 2
Project Description and Background
2.1.2 Overview of the 2020 Mine Plan
This section describes the 2020 Mine Plan, as presented in PLP's June 8, 2020, CWA Section 404 permit
application to USACE (PLP 2020b).15 The 2020 Mine Plan is evaluated in USACE's FEIS and is identified
in the FEIS as Alternative 3 - North Road Only Alternative, Concentrate Pipeline and Return Pipeline
Variant.
In the 2020 Mine Plan, PLP proposes to develop the Pebble copper-gold-molybdenum porphyry deposit
as a surface mine. The closest communities are the villages of Iliamna, Newhalen, and Nondalton, each of
which is approximately 17 miles from the deposit (USACE 2020b). The project consists of four primary
elements: the mine site; the Diamond Point port; the transportation corridor, including concentrate and
water return pipelines; and the natural gas pipeline and fiber optic cable (Figure 2-1).
For the purposes of this recommended determination, EPA Region 10 evaluated the mine site, which is
described in more detail below (Figure ES-3). EPA did not evaluate the ancillary project components
along the transportation corridor or at the Diamond Point port; therefore, this recommended
determination does not address these components.
The 2020 Mine Plan would progress through four distinct phases: construction, operations (also
referred to as production), closure, and post-closure. The construction period would last approximately
4 years, followed by 20 years of operation. Closure, including physical reclamation of the mine site, is
projected to take approximately 20 years. Post-closure activities, including long-term water
management and monitoring, is expected to last for centuries (USACE 2020a).
2,1,2,1 Mine Site
According to USACE, the 2020 Mine Plan is proposed to be a conventional drill, blast, truck, and shovel
operation with a mining rate of up to 73 million tons of ore per year. Approximately 1,300 million tons
of mineralized rock and 150 million tons of waste rock and overburden would be mined over the
project's life. The mineralized material would be crushed and sent to a coarse ore stockpile to feed the
process plant. The process plant would include grinding and flotation steps, with a processing rate of up
to 66 million tons per year, to produce on average 613,000 tons of copper-gold concentrate and 15,000
tons of molybdenum concentrate annually (USACE 2020b).
The fully developed mine site would include an open pit, bulk tailings storage facility (TSF), pyritic TSF,
a 270-megawatt power plant, water management ponds (WMPs), water treatment plants (WTPs), and
milling/processing facilities, as well as supporting infrastructure. Non-potentially acid generating and
non-metal leaching waste rock would be used in the construction of infrastructure needed to support
the mine. In addition to waste rock, three quarries (material sites) would be needed (USACE 2020b)
(Figure ES-4).
15 Pebble Project Department of the Army Application for Permit POA-2017-00271.
Recommended Determination 2 2 December 2022
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Section 2 Project Description and Background
Figure 2-1. Project area map. Figure 1-2 from PLP's June 8, 2020, Clean Water Act Section 404 permit application (PLP 2020b).
FIGURE 1-2
Project Area
Bulk Tailings Storage Facility
Water Managment Pond
: TSF Laydown
Pyritic TSF/PAG Waste Rock Storage
^41 Open Pit
Overburden Stockpile
Mill Site Process Plant
££ Quarry
Port Site Features
Dredge Material Stockpile
Transportation Corridor
Natural Gas Pipeline
Existing Roads
~ Township Boundary
Recommended Determination
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Section 2
Project Description and Background
Bulk tailings would be placed in the bulk TSF, while pyritic tailings would be placed in the lined pyritic
TSF. Potentially acid generating (PAG) and metal leaching waste rock would be stored in the lined
pyritic TSF until closure, when it would be back-hauled into the open pit. The bulk TSF would have two
embankments: the main embankment, constructed using the centerline construction method; and the
south embankment, constructed using the downstream construction method to facilitate lining of the
upstream face. The pyritic TSF would be fully lined and would have three embankments constructed
using the downstream method (USACE 2020b).
Soils and other overburden would be stored in stockpile areas at various locations throughout the site.
Stockpiled soils and other overburden would be used for reclamation during mine closure. The
proposed mine site is currently undeveloped and is not served by any transportation or utility
infrastructure (USACE 2020b).
According to USACE, PLP would manage water flows through the mine area, while providing a water
supply for operations. PLP would capture runoff water contacting the facilities at the mine site and
water pumped from the open pit, then either reuse the water in the milling process or treat the water
before releasing it to surface waters (USACE 2020b).
The open-pit area would be dewatered through groundwater withdrawal from approximately 30
groundwater wells installed around the open-pit perimeter. As the pit is deepened, dewatering would
continue via in-pit ditches, in-pit wells, and/or perimeter wells. The water level in the open pit would
continue to be managed via pumping of groundwater wells and transfer to the open-pit WMP (USACE
2020b).
As described by USACE, mine facilities would be closed at the end of operations and reclaimed.
Reclamation and closure of the project would fall under the jurisdiction of Alaska Department of Natural
Resources (ADNR) Division of Mining, Land, and Water and the Alaska Department of Environmental
Conservation (ADEC). The Alaska Reclamation Act (Alaska Statute 27.19) is administered by ADNR. It
applies to state, federal, municipal, and private land, as well as water subject to mining operations. PLP
has prepared a Reclamation and Closure Plan providing guidelines for implementing stabilization and
reclamation procedures for various facilities associated with the project (USACE 2020a: Appendix M4.0).
USACE indicates that revisions to PLP's Reclamation and Closure Plan may be necessary to address
changes during preliminary and detailed design work and state permitting (USACE 2020b).
2,1,2,2 Evaluation of Location Options for a Mine Site at the Pebble Deposit
As part of considering alternatives in the Environmental Impact Statement (EIS) and CWA Section 404
processes, USACE evaluated multiple locations throughout the SFK, NFK, and UTC watersheds for siting
various components associated with a mine site at the Pebble deposit (USACE 2020a: Section 2 and
Appendix B). Siting criteria used to select options varied based on the mine component under
consideration but included factors related to potential site capacity, total footprint and catchment area,
distance from other mine site components, and ground/substrate conditions. Screening criteria,
including overall project purpose, practicability, and environmental impacts, were applied to the range
Recommended Determination
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Section 2
Project Description and Background
of options and locations identified during the EIS process to narrow the range of alternatives considered
in the NEPA and CWA Section 404 analyses.
For example, 26 land options were initially evaluated as potential TSF locations and "detailed
information" was provided for each (USACE 2020a: Page B-83). Twenty-three of these options were
located at sites within the SFK, NFK, and UTC watersheds (Figure 2-2). The 26 options were compared to
the TSF locations put forth in PLP's permit application, and all were rejected. Seven of the options were
determined not to be practicable (i.e., not feasible due to inappropriate substrate conditions or
inadequate capacity). The remaining options "would all increase the wetlands and stream miles filled
when compared to the proposed project" and "would pose risks similar to the proposed project in the
event of a tailings dam failure" (USACE 2020a: Page B-84). Similarly, seven alternate locations for the
main WMP were evaluated and detailed information was provided for each. All seven options were
located within the SFK, NFK, and UTC watersheds (USACE 2020a: Appendix B) (Figure 2-3), and all were
rejected because detailed evaluation found them to be "not reasonable or not feasible" (USACE 2020a:
Page B-91).
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Project Description and Background
Figure 2-2. Optional locations for siting the Bulk Tailing Storage Facility evaluated within the FEIS. Figure 1.0 from FLP (2018d: RFI 069).
rr- . - _
—— ' "eJjj
t^bble
PARTNERSHIP
FIGURE 1.0
TSF Options, Mine Area
I Proposed Pit |
ESS 13
TSF Options
3 14
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V7A is
ID 2
VZA16
~ 3
HI 17
mm is
H5
19
2 20
YZAi
[ ] 21
8
~ 22
¦
1 123
10
24
11
¦ 25
V/A 12
m 26
Scale 1:150,000
File: PLP_TSF_A
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Figure 2-3. Optional locations for siting the Main Water Management Pond evaluated within the FEIS. Figure 1 from PLP (2019d: RFI150).
Main Water
Management Pond
Main Water
Management Pond
Alternative 1
Alternative 2
PAG Tailings
"atad Waste Ro k
otWage Facili y
Bulk Tailings
Storage Facility
Quarry B
Open Pit
Quarry C
T 3S|? 35W
T4S
Alternative
FIGURE 1
VV&ter Management Pond Alternatives
Water Managment Pond
Alternatives
Alternative 1
Alternative 2
Alternative 3
Alternative 4
Alternative 5
Alternative 6
££ Alternative 7
££ Ma'n Water Management Pond
Mine Site Footprints
Mine Site Access Road
50'Contour (Existing)
~ Township Boundary
Section Boundary
Map Area
^ I
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2.2 Background
2.2.1 Timeline of Key Events Related to the Pebble Deposit (1984-
October 2021)
In 1984, the State of Alaska adopted the Bristol Bay Area Plan for State Lands (BBAP). The 1984 BBAP
placed fish and wildlife habitat and harvest as a primary use throughout the Bristol Bay study area
(ADNR 1984a). To carry out its goals, the 1984 BBAP included Mineral Closing Order (MCO) 393, along
with 18 other MCOs, which closed the stream channel plus 100 feet on either side of designated
anadromous reaches of 64 streams in the Bristol Bay region to new mineral entry. Implementing MCO
393 was consistent with ADNR's determination that new mineral entry "creates an incompatible surface
use conflict with salmon propagation and production, and jeopardizes the economy of the Bristol Bay
region and the management of the commercial, sport, and subsistence fisheries in the Bristol Bay area"
(ADNR 1984b: Page 2). The BBAP was subsequently amended in 2005 and 2013, but the MCOs
established by the initial 1984 BBAP were not affected by these amendments.16 While the protections
associated with MCO 393 apply to portions of the SFK, NFK, and UTC located downstream of the Pebble
deposit,17 the portions of SFK, NFK, and UTC and their tributaries that overlie the Pebble deposit and
would be directly affected by the 2020 Mine Plan are not covered by MCO 393.
The Pebble deposit was first explored by Cominco Alaska, a division of Cominco Ltd, now Teck, between
1985 and 1997, with exploratory drilling between 1988 and 1997 (Ghaffari et al. 2011). In November
1987, Teck staked claims in the Pebble prospect and added claims to that area in July 1988. In 2001,
Northern Dynasty Minerals Ltd. (NDM) acquired claims related to the Pebble deposit. From 2001 to
2019, NDM, and subsequently PLP,18 conducted significant mineral exploration at the Pebble deposit,
including deposit delineation, and developed environmental, socioeconomic, and engineering studies of
the Pebble deposit (Kalanchey et al. 2021).
Beginning in 2004, NDM engaged with USACE in pre-CWA Section 404 permit application meetings.
Through these meetings, USACE confirmed that NDM/PLP would need a CWA Section 404 permit to
develop a mine at the Pebble deposit and that the permit review process would include a public interest
16 The 2013 BBAP designates land uses in the footprint of the 2020 Mine Plan. The 2013 BBAP specifies that these
lands are to be retained in public ownership and managed for multiple uses—including recreation, timber,
minerals, and fish and wildlife—as well as natural scenic, scientific, and historic values (USACE 2020b). This
specification does not preclude construction of the mine and related facilities, and the State of Alaska has made no
specific determinations whether the 2020 Mine Plan is consistent with the BBAP (USACE 2020b).
17 Specifically, MCO 393 closed the designated anadromous portions of the South Fork Koktuli River (AWC # 325-
30-10100-2202-3080), North Fork Koktuli River (AWC # 325-30-10100-2202-3080-4083), and Upper Talarik
Creek (AWC # 324-10-10150-2183), as well as any state-owned lands 100 feet from ordinary high water (on both
sides of the stream) to new mineral entry (ADNR 1984b).
18 PLP was created in 2007 by co-owners NDM and Anglo American PLC to design, permit, construct, and operate a
long-life mine at the Pebble deposit (Ghaffari et al. 2011). In 2013, NDM acquired Anglo American's interest in PLP,
and NDM now holds a 100 percent interest in PLP (Kalanchey et al. 2021).
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Project Description and Background
review, development of an environmental document in accordance with NEPA, and a review for
compliance with the CWA Section 404(b)(1) Guidelines (Lestochi pers. comm.).
Also in 2004, EPA Region 10 met numerous times with NDM to discuss the potential environmental
impacts associated with developing a mine at the Pebble deposit, including early environmental baseline
study plans and preparation for the review of the mine project pursuant to NEPA and Section 404 of the
CWA. Later that year, NDM established and began coordinating a Baseline Environmental Team of
federal and state agency technical staff, including EPA Region 10, to continue reviewing the draft
environmental baseline study plans. NDM also provided periodic updates on its process to develop a
mine, as well as findings from its environmental baseline studies and findings related to cultural
resources that could be affected.
In 2006, NDM submitted water rights permit applications to ADNR for water rights to use UTC and the
Koktuli River in mining operations (NDM 2006). In total, NDM applied for rights to approximately 35
billion gallons of groundwater and surface water per year (ADNR 2022b).
Between 2007 and 2010, nine state and federal agencies, including Alaska Department of Fish and Game
(ADF&G), ADNR, National Marine Fisheries Service (NMFS), National Park Service (NPS), USACE, U.S.
Fish and Wildlife Service (USFWS), and EPA Region 10 participated in the Pebble Project Technical
Working Group, which was formed by PLP to facilitate coordinated agency review of environmental
studies to support future NEPA and subsequent permitting actions (ADNR 2022b).
On May 2, 2010, former EPA Administrator Lisa P. Jackson and former Region 10 Regional
Administrator Dennis McLerran received a letter from six federally recognized Bristol Bay tribal
governments requesting that EPA initiate a process under Section 404(c) of the CWA to protect waters,
wetlands, fishes, wildlife, fisheries, subsistence, and public uses in the Nushagak and Kvichak River
watersheds and Bristol Bay from metallic sulfide mining, including a potential Pebble mine. Signatories
included Nondalton Tribal Council, New Stuyahok Traditional Council, Levelock Village Council, Ekwok
Village Council, Curyung Tribal Council, and Koliganek Village Council. Subsequently, three additional
federally recognized Bristol Bay tribal governments signed this letter: Native Village of Ekuk, Village of
Clark's Point, and Twin Hills Village Council.
Following the letter from the tribes, EPA and former President Obama received numerous letters from
additional partners and stakeholders expressing their interests and concerns regarding potential EPA
action to protect Bristol Bay fishery resources. Some requests favored immediate action to
comprehensively protect Bristol Bay, including a public process under Section 404(c) of the CWA.
Others favored a targeted CWA Section 404(c) action that would restrict only mining associated with the
Pebble deposit. In addition to other Bristol Bay tribes, EPA received letters from the Bristol Bay Native
Association, the Bristol Bay Native Corporation, other tribal organizations, stakeholder groups
dependent on the fishery (i.e., commercial and recreational fishers, seafood processors and marketers,
chefs and restaurant and supermarket owners, and sport fishing and hunting lodge owners and guides),
sporting goods manufacturers and vendors, a coalition of jewelry companies, conservation
organizations, members of the faith community, and elected officials from Alaska and other states.
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Other requests received during this time urged EPA to refrain from taking action under CWA Section
404(c). These requests included those that asked for more time to understand potential implications of
mine development in the Bristol Bay watershed. Others requested EPA wait until formal mine permit
applications had been submitted and an EIS had been developed. These requestors included four
federally recognized Bristol Bay tribal governments (Newhalen Tribal Council, South Naknek Tribal
Council, King Salmon Traditional Village Council, and Iliamna Village Council), other tribal organizations,
former Governor Parnell of Alaska, and attorneys representing PLP.
In response to requests, EPA met with tribal governments and stakeholders, including those that
supported and those that opposed a mine at the Pebble deposit, to hear their concerns and receive any
information they wished to provide. These meetings occurred in the villages in the Bristol Bay
watershed and in Anchorage, Alaska, Seattle, Washington, and Washington, DC.
Former EPA Administrator Jackson and former Region 10 Regional Administrator McLerran visited
Alaska in August 2010 to learn about the challenges facing rural Alaska towns and Alaska Native
villages. Their itinerary included a meeting with PLP for a briefing on the proposed mining of the Pebble
deposit. They also visited Dillingham, where they participated in two listening sessions, one specifically
for tribal leaders from Bristol Bay and one meeting open to all local and regional entities.
In February 2011, NDM submitted a preliminary assessment for mining the Pebble deposit to the U.S.
Securities and Exchange Commission (SEC) (SEC 2011) entitled Preliminary Assessment of the Pebble
Project, Southwest Alaska (Ghaffari et al. 2011). The preliminary assessment described three stages of
mine development at the Pebble deposit: an initial 2-billion-ton mine consisting of 25 years of open-pit
mining, a 3.8-billion-ton mine consisting of 45 years of open-pit mining, and a 6.5-billion-ton mine
consisting of 78 years of open-pit mining. The preliminary assessment also indicated that the total
Pebble mineral resource might approach 11 billion tons of ore.
Also in February 2011, in response to the competing requests regarding CWA Section 404(c) described
previously, former Region 10 Regional Administrator McLerran announced EPA's intent to conduct a
scientific assessment to evaluate how future large-scale mining projects might affect water quality and
Bristol Bay's salmon fishery. This ecological risk assessment was ultimately entitled Assessment of
Potential Mining Impacts on Salmon Ecosystems of Bristol Bay, Alaska (Bristol Bay Assessment or BBA).19
Concurrent with this announcement, EPA Region 10 notified by letter 31 Bristol Bay tribes, ADEC,
ADF&G, ADNR, the Bureau of Land Management, NMFS, NPS, USACE, USFWS, and the U.S. Geological
Survey (USGS) of its intent to develop the BBA. The same week, EPA Region 10 met with Nuna
Resources, which represents several Alaska Native Claims Settlement Act (ANCSA) Village
Corporations,20 and had meetings with other partners and stakeholders. NFMS, USFWS, and USGS
19 EPA conducted the BBA consistent with its authority under CWA Section 104(a) and (b).
20 Congress created Regional and Village Corporations (Alaska Native Corporations) to manage the lands, funds,
and other assets conveyed to Alaska Natives by ANCSA.
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worked closely with EPA on the development of the BBA, including authoring appendices to the BBA
(see Table 2-1 for a timeline of BBA development).21
In December 2011, PLP provided EPA Region 10 with an advance, embargoed copy of its more than
25,000-page environmental baseline document, which presented the results of baseline studies
conducted from 2004 through 2008 (PLP 2011). The environmental baseline document was designed to
characterize the existing physical, chemical, biological, and social environments in the SFK, NFK, and
UTC watersheds where the Pebble deposit is located, as well as the proposed mine's transportation
corridor that would link the mine site to a proposed port site on Cook Inlet. The extensive
environmental baseline document developed by PLP (PLP 2011) and NDM's preliminary assessment for
mining the Pebble deposit that was submitted to the SEC in February 2011 (Ghaffari et al. 2011) were
key resources used in the development of the BBA.
EPA's purpose in conducting the BBA was to characterize the biological and mineral resources of the
Bristol Bay watershed; increase understanding of the potential impacts of large-scale mining on the
region's fish resources, in terms of both day-to-day operations and potential accidents and failures; and
inform future decisions by government agencies and others related to protecting and maintaining the
chemical, physical, and biological integrity of the watershed. The BBA represents a review and synthesis
of information available at that time to identify and evaluate potential risks of future large-scale mining
development on the Bristol Bay watershed's fish habitats and populations and consequent effects on the
region's wildlife and Alaska Native communities.
Table 2-1. Bristol Bay Assessment timeli
I
2/7/2011
Announced intent to conduct the BBA.
8/2011
Met with Intergovernmental Technical Team to gather information to inform the scope of the
BBA.
2/24/2012
Invited the public to nominate qualified experts to be considered for the external peer review
panel.
3/2012
Distributed internal review draft of the BBA for Agency technical review.
5/18/2012
Released first external review draft of the BBA for public comment and external peer review.
5/31/2012 and 6/4-7/2012
Held public meetings in Dillingham, Naknek, NewStuyahok, Nondalton, Levelock, Igiugig,
Anchorage, and Seattle to communicate the results of the draft BBA and receive public
comments.
6/5/2012
Announced the names of the 12 independent peer reviewers to review the draft BBA and
released the draft charge questions, providing the public the opportunity to comment on the
draft charge questions.
8/7-9/2012
Held external peer review meeting in Anchorage.
11/2012
Released the final peer review report containing the external peer review of the May 2012
draft of the BBA.
4/30/2013
Released second external review draft of the BBA for public comment and follow-on review
by external peer reviewers, to evaluate how well the second external review draft responded
to peer reviewers' comments on the first external review draft.
1/15/2014
Released the final BBA and EPA Response to Peer Review Comments document.
3/21/2014
Released EPA Response to Public Comments documents.
21 For more information about EPA's efforts in Bristol Bay or copies of the Bristol Bay Assessment, see
http://www.epa.gov/bristolbay.
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Project Description and Background
Meaningful engagement with tribal governments, Alaska Native Corporations, and all stakeholders was
essential to ensure that EPA heard and understood the full range of perspectives on both the BBA and
potential effects of mining in the region. EPA released two drafts of the BBA for public comment.
Approximately 233,000 and 890,000 comments were submitted to the EPA docket during the 60-day
public comment periods for the May 2012 and April 2013 drafts, respectively. EPA also held eight public
comment meetings in May and June 2012 in Dillingham, Naknek, New Stuyahok, Nondalton, Levelock,
Igiugig, Anchorage, and Seattle. Approximately 2,000 people attended these meetings. An overview of
these meetings was shared via two webinars in July 2012.
Consistent with Executive Order 13 1 75,22 entitled Consultation and Coordination with Indian Tribal
Governments, and EPA Region 10 Tribal Consultation and Coordination Procedures (EPA 2012), EPA
Region 10 invited all 31 Bristol Bay tribal governments to participate in consultation and coordination
on both drafts of the BBA. Pursuant to Public Law 108-199,118 Stat. 452, as amended by Public Law
108-447,118 Stat. 3267, EPA also invited all 26 Alaska Native Corporations in Bristol Bay to participate
in engagement on both drafts of the BBA. Throughout the development of the BBA, 20 tribal
governments and one tribal consortium participated in the consultation and coordination process, and
17 Alaska Native Corporations participated in the engagement process.
The BBA also underwent external peer review by a panel of 12 independent experts (Table 2-1). The
peer review panel reviewed the May 2012 draft and provided EPA with their comments. A 3-day peer
review meeting was held in Anchorage on August 7 through 9, 2012, during which peer reviewers heard
testimony from approximately 100 members of the public. The peer review panel also reviewed the
April 2013 draft and provided EPA with a second round of comments that evaluated whether the April
2013 draft was responsive to their original comments.
In January 2014, EPA released both the final BBA (EPA 2014) and the final Response to Peer Review
Comments document. In March 2014, EPA released the final Response to Public Comments documents
for both the May 2012 and April 2013 drafts of the BBA.
On February 28, 2014, after careful consideration of available information, including information
collected as part of the BBA, other existing scientific and technical information, and extensive
information provided by stakeholders, EPA Region 10 notified USACE, the State of Alaska, and PLP that it
had decided to proceed under the CWA Section 404(c) regulations, 40 CFR Part 231, to review potential
adverse environmental effects of discharges of dredged or fill material associated with mining the
Pebble deposit. EPA Region 10 stated that it was taking this step because it had reason to believe that
porphyry copper mining of the scale contemplated at the Pebble deposit could result in unacceptable
adverse effects on fishery areas. In accordance with the regulation at 40 CFR 231(a)(1), EPA Region 10
provided USACE, the State of Alaska, and PLP an opportunity to submit information for the record, to
demonstrate to the satisfaction of the EPA Region 10 Regional Administrator that no unacceptable
22 On January 26, 2021, President Biden issued the Presidential Memorandum, Tribal Consultation and
Strengthening Nation-to-Nation Relationships, which charges each federal agency to engage in regular, meaningful,
and robust consultation and to implementthe policies directed in Executive Order 13175.
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Project Description and Background
adverse effects on aquatic resources would result from discharges associated with mining the Pebble
deposit, or that USACE intended to take corrective action to prevent unacceptable adverse effects
satisfactory to the EPA Region 10 Regional Administrator.
Also on February 28, 2014, EPA Region 10 invited all 31 Bristol Bay tribal governments to participate in
tribal consultation, and all 26 Alaska Native Corporations to participate in consultation and engagement
on the 2014 Proposed Determination. In total, 17 tribal governments participated in the consultation
process, and 6 Alaska Native Corporations participated in the consultation and engagement process.
EPA Region 10 held two meetings on March 25, 2014, one with PLP executives and one with the Alaska
Attorney General. On April 29, 2014, PLP and the Alaska Attorney General separately provided
information as part of the initial CWA Section 404(c) consultation period. In these submittals, PLP and
the Alaska Attorney General raised several legal, policy, scientific, and technical issues, including
questions regarding EPA's authority to initiate a Section 404(c) review before PLP had submitted a
Section 404 permit application to USACE, the scientific credibility of the BBA, and whether the BBA
should be used to inform decision-making under Section 404(c). Most of the scientific and technical
issues detailed in these documents had been raised before; EPA had provided responses to these issues
in individual correspondence to PLP and the Alaska Attorney General and, most comprehensively, in the
400-page BBA Response to Peer Review Comments document released in January 2014 and the 1,200-
page BBA Response to Public Comments documents released in March 2014.
After fully considering the April 29, 2014, submittals from PLP and the Alaska Attorney General, the EPA
Region 10 Regional Administrator was not satisfied that no unacceptable adverse effect could occur, or
that adequate corrective action could be taken to prevent an unacceptable adverse effect. Thus, EPA
Region 10 decided to take the next step in the Section 404(c) process, publication of a proposed
determination.
On July 21, 2014, EPA Region 10 published in the Federal Register a Notice of Proposed Determination
under Section 404(c) of the CWA to restrict the use of certain waters in the SFK, NFK, and UTC
watersheds as disposal sites for dredged or fill material associated with mining the Pebble deposit (79
FR 42314, July 21, 2014). The notice started a public comment period that ended on September 19,
2014. EPA Region 10 also held seven hearings during the week of August 11, 2014. These hearings took
place in Anchorage, Nondalton, New Stuyahok, Dillingham, Kokhanok, Iliamna, and Igiugig. More than
830 community members participated in the seven hearings, more than 300 of whom provided oral
statements. In addition to testimony taken at the hearings, EPA Region 10 received more than 670,000
written comments during the public comment period, more than 99 percent of which supported the
2014 Proposed Determination. The public comments and transcripts from the public hearings can be
found in the docket for the 2014 Proposed Determination.23
23 Information regarding the 2014 Proposed Determination can be found in the docket for this effort at
www.regulations.gov, see docket ID No. EPA-R10-OW-2014-0505.
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Project Description and Background
Before EPA could reach the next step in the CWA Section 404(c) review process—to either withdraw the
2014 Proposed Determination or prepare a recommended determination pursuant to 40 CFR 231.5(a)
—PLP filed multiple lawsuits against the Agency. On November 25, 2014, the U.S. District Court for the
District of Alaska (District Court) issued a preliminary injunction against EPA in one of those lawsuits,
which halted EPA Region 10's CWA Section 404(c) review process until the case was resolved (Order
Granting Preliminary Injunction at 1-2, Pebble Limited Partnership v. EPA, No. 3:14-cv-00171 (D. Alaska
Nov. 25, 2014)). On May 11, 2017, EPA and PLP settled that lawsuit, as well as PLP's other outstanding
lawsuits, and the court subsequently dissolved the injunction and dismissed the case with prejudice.
Under the terms of the settlement, EPA agreed to "initiate a process to propose to withdraw the
Proposed Determination" by July 11, 2017. EPA also agreed not to forward a signed recommended
determination to EPA Headquarters until May 11, 2021, or until EPA published a notice of USACE's FEIS
on PLP's CWA Section 404 permit application for the proposed Pebble mine, whichever came first. To
take advantage of this period of forbearance, PLP was required to submit its CWA Section 404 permit
application to USACE within 30 months of execution of the settlement agreement.24
On July 11, 2017, EPA signed a Federal Register notice that initiated the process and proposed to
withdraw the 2014 Proposed Determination. Also on July 11, 2017, EPA invited all 31 Bristol Bay tribal
governments to participate in consultation and coordination, and all 26 Alaska Native Corporations to
participate in consultation on the 2017 proposal to withdraw. In total, 18 tribal governments and 3
Alaska Native Corporations participated in the consultation processes.
On July 19, 2017, in accordance with the terms of the settlement agreement, EPA Region 10 published in
the Federal Register a notice of its proposal to withdraw the 2014 Proposed Determination (82 FR
33123, July 19, 2017). EPA stated that the Agency was proposing to withdraw the 2014 Proposed
Determination because it would (1) provide PLP with additional time to submit a CWA Section 404
permit application to USACE; (2) remove any uncertainty, real or perceived, about PLP's ability to
submit a permit application and have that permit application reviewed; and (3) allow the factual record
regarding any forthcoming permit application to develop. EPA explained that "[i]n light of the basis upon
which EPA is considering withdrawal of the Proposed Determination, EPA is not soliciting comment on
the proposed restrictions or on science or technical information underlying the Proposed
Determination" (82 FR 33124, July 19, 2017).
The July 19, 2017 notice started a public comment period that ended on October 17, 2017. EPA also held
hearings in Dillingham and Iliamna the week of October 9, 2017. EPA received more than one million
public comments regarding its proposal to withdraw the 2014 Proposed Determination. Approximately
99 percent of commenters expressed opposition to the withdrawal of the 2014 Proposed Determination.
The public comments, transcripts from the public hearings, and summaries of the tribal and Alaska
24 For a copy of the settlement agreement, see https://www.epa.gov/bristolbay/2017-settlement-agreement-
between-epa-and-pebble-limited-partnership.
Recommended Determination
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Section 2
Project Description and Background
Native Corporation consultations can be found in the docket for the 2017 proposal to withdraw the
2014 Proposed Determination.25
On December 22, 2017, PLP submitted to USACE a CWA Section 404 permit application for the discharge
of dredged and fill material to waters of the United States to develop a mine at the Pebble deposit, as
well as associated infrastructure (e.g., ports, roads, and pipelines). On January 5, 2018, USACE issued a
public notice that provided PLP's permit application to the public and stated that an EIS would be
required as part of its permit review process, consistent with NEPA. USACE also invited relevant federal,
state, and local agencies, as well as tribal governments, to be cooperating agencies on the development
of this EIS. EPA, the United States Coast Guard, the Bureau of Safety and Environmental Enforcement, the
Advisory Council on Historic Preservation, USFWS, NPS, the Pipeline and Hazardous Materials Safety
Administration, the State of Alaska, the Lake and Peninsula Borough, the Curyung Tribal Council, and the
Nondalton Tribal Council accepted the USACE invitation and became NEPA cooperating agencies.
On January 26, 2018, EPA Region 10 announced a "suspension" of the proceeding to withdraw the 2014
Proposed Determination. This action was published in the Federal Register on February 28, 2018 (83 FR
8668, February 28, 2018).
On March 29, 2018, USACE published in the Federal Register a Notice of Intent to prepare an EIS and a
Notice of Scoping for the Pebble Project (83 FR 13483, March 29, 2018). The EIS scoping public
comment period opened on April 1, 2018, and closed on June 29, 2018. USACE received 174,889 total
submissions during the scoping comment period, which are summarized in the FEIS, Appendix A. On
June 29, 2018, EPA Region 10 submitted a comment letter to USACE, pursuant to the White House
Council on Environmental Quality (CEQ) NEPA regulations and Section 309 of the Clean Air Act (CAA),
that contained recommendations for the EIS in response to the scoping process.
On March 1, 2019, USACE released the Draft EIS (DEIS) for public comment. Also on March 1, 2019,
USACE published a public notice soliciting comment on PLP's CWA Section 404 permit application
(Public Notice POA-2017-00271). The public comment period for both the DEIS and the CWA Section
404 permit application opened on March 1, 2019, and closed July 1, 2019. USACE also held nine public
hearings on the DEIS throughout March and April 2019. USACE received 311,885 public comments on
the DEIS, which are summarized in the FEIS, Appendix D. USACE held public hearings on the DEIS in
Naknek, Kokhanok, Newhalen, Igiugig, New Stuyahok, Nondalton, Dillingham, Homer, and Anchorage,
Alaska.
On July 1, 2019, EPA sent a letter to USACE with its comments and recommendations on the DEIS,
pursuant to EPA's review responsibilities under the CEQ NEPA regulations and CAA Section 309. On July
1, 2019, EPA sent a separate letter to USACE with comments on the CWA Section 404 permit public
notice.
25 Information regarding the proposal to withdraw can be found in the docket for this effort at
www.regulations.gov, see docket ID No. EPA-R10-OW-2017-0369.
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Project Description and Background
On August 30, 2019, after conferring with EPA's General Counsel,26 EPA Region 10 published in the
Federal Register its decision to withdraw the 2014 Proposed Determination, thereby concluding the
withdrawal process that was initiated on July 19, 2017 (84 FR 45749, August 30, 2019). EPA identified
that it was withdrawing the 2014 Proposed Determination because (1) new information had been
generated since 2014, including information and preliminary conclusions in USACE's DEIS, which EPA
would need to consider before any potential future decision-making regarding the matter; (2) the record
would continue to develop throughout the permitting process; and (3) EPA could and then had initiated
the CWA Section 404(q) Memorandum of Agreement dispute resolution process27 and it was
appropriate to use that process to resolve issues before engaging in any potential future decision-
making regarding the matter.
In its August 30, 2019 notice of withdrawal of the 2014 Proposed Determination, EPA stated that "[a]s in
EPA's prior notices, EPA is not basing its decision-making on technical consideration or judgments about
whether the mine proposal will ultimately be found to meet the requirements of the 404(b)(1)
Guidelines or results in 'unacceptable adverse effects' under CWA section 404(c)" (84 FR 45756, August
30,2019).
In October 2019, twenty tribal, fishing, environmental, and conservation groups challenged EPA's
withdrawal of the 2014 Proposed Determination in the District Court. The District Court granted EPA's
motion to dismiss the case.
In February 2020, USACE released the preliminary FEIS to the cooperating agencies for comment. EPA
Region 10 submitted comments and recommendations to the USACE on the preliminary FEIS on March
26,2020.
From March 12, 2020 through May 28, 2020, an interagency team of managers and scientific and
technical staff from USACE, EPA, and USFWS met weekly to evaluate the proposed project for
compliance with the CWA Section 404(b)(1) Guidelines.
Based on its review of the Section 404(b)(1) Guidelines, USACE determined that EIS Alternative 3 (North
Road Only with concentrate and return water pipelines) was the least environmentally damaging
practicable alternative (LEDPA). In June 2020, PLP submitted to USACE a revised permit application (i.e.,
the 2020 Mine Plan) to incorporate changes to the project based on USACE's LEDPA determination
26 See footnote 11 in Section 1.
27 CWA Section 404(q) directs the Secretary of the Army to enter into agreements with various federal agencies,
including EPA "to minimize, to the maximum extent practicable, duplication, needless paperwork, and delays in the
issuance of permits under this section" (33 U.S.C. 1344(q)). EPA and USACE have entered into various agreements
pursuant to Section 404(q). The operative agreement was entered in 1992. Part IV, paragraph 3 of the 1992 EPA
and Army Memorandum of Agreement to implement Section 404(q) (hereinafter referred to as the "404(q) MOA")
sets forth the "exclusive procedures" for elevation of individual permits cases (EPA and DOA 1992).
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Project Description and Background
(USACE 2020b). USACE determined that the changes to the project described in the revised permit
application were not significant enough to warrant development of a Supplemental DEIS.28
On July 24, 2020, USACE published a Notice of Availability for the FEIS in the Federal Register (USACE
2020a).
On November 20, 2020, USACE issued its Record of Decision (ROD) denying PLP's CWA Section 404
permit application on the basis that the proposed project would not comply with the CWA Section
404(b)(1) Guidelines and would be contrary to the public interest (USACE 2020b). The USACE permit
denial addresses only PLP's specific permit application. By letter dated November 25, 2020, USACE
notified PLP that the proposed project failed to comply with the CWA Section 404(b)(1) Guidelines
because "the proposed project would cause unavoidable adverse impacts to aquatic resources which
would result in Significant Degradation to aquatic resources" and that PLP's compensatory mitigation
plan submitted to USACE on November 4, 2020, did not alter that finding.
On January 19, 2021, PLP filed a request for an appeal of the USACE permit denial with USACE, pursuant
to 33 CFR Part 331. USACE accepted the appeal on February 25, 2021. USACE's review of the appeal is
ongoing.
On June 17, 2021, the Ninth Circuit Court of Appeals reversed the District Court's decision to dismiss the
tribal, fishing, environmental, and conservation groups' challenge to EPA's withdrawal of the 2014
Proposed Determination. The Ninth Circuit concluded that under EPA's regulations at 40 CFR 231.5(a),
EPA is authorized to withdraw a proposed determination "only if the discharge of materials would be
unlikely to have an unacceptable adverse effect." Trout Unlimited v. Pirzadeh, 1 F.4th 738, 757 (9th Cir.
2021) (emphasis in original). The Ninth Circuit remanded the case to the District Court for further
proceedings.
On September 28, 2021, EPA filed a motion in the District Court requesting that the court vacate the
Agency's 2019 decision to withdraw the 2014 Proposed Determination and remand the action to the
Agency for reconsideration. The District Court granted EPA's motion on October 29, 2021.
2.2.2 Re-initiation of Clean Water Act Section 404(c) Review Process
(November 2021-Present)
The District Court's vacatur of EPA's 2019 decision to withdraw the 2014 Proposed Determination had
the effect of reinstating the 2014 Proposed Determination and reinitiating EPA's CWA Section 404(c)
review process. Because the next step in the CWA Section 404(c) review process required the EPA
Region 10 Regional Administrator to, within 30 days, decide whether to withdraw the 2014 Proposed
Determination or prepare a recommended determination, EPA Region 10 published in the Federal
Register on November 23, 2021, a notice extending the applicable time requirements through May 31,
2022, to consider available information and determine the appropriate next step in the CWA Section
28 PLP also submitted an updated permit application to USACE in December 2019 and USACE made a similar
finding at that time that a Supplemental DEIS was not warranted.
Recommended Determination
2-17
December 2022
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Project Description and Background
404(c) review process. In its notice, EPA concluded that it should consider information that has become
available since EPA issued the 2014 Proposed Determination.
On January 27, 2022, EPA Region 10 sent letters inviting consultation to 31 tribal governments located
in the Bristol Bay watershed. Separately, it also invited consultation with 5 Alaska Native Corporations
and offered engagement to 21 Alaska Native Corporations with lands in the Bristol Bay watershed. EPA
Region 10 hosted three informational webinars for tribal governments and one informational webinar
for Alaska Native Corporations to review the CWA Section 404(c) process and answer questions. In
addition, EPA Region 10 engaged in multiple consultations with tribal governments and Alaska Native
Corporations from February through October 2022. EPA will continue to provide opportunities for tribal
consultation and coordination and consultation and engagement with Alaska Native Corporations going
forward.
Also on January 27, 2022, EPA Region 10 notified USACE, ADNR, PLP, Pebble East Claims Corporation,
Pebble West Claims Corporation, and Chuchuna Minerals29 (the Parties) of EPA's intention to issue a
revised proposed determination because, based on EPA Region 10's evaluation to date of available
information, it continued to have reason to believe that the discharge of dredged or fill material
associated with mining the Pebble deposit could result in unacceptable adverse effects on fishery areas.
Consistent with EPA's Section 404(c) regulations at 40 CFR 231(a)(1), EPA Region 10 provided the
Parties with the opportunity to submit information for the record to demonstrate to the satisfaction of
the EPA Region 10 Regional Administrator that no unacceptable adverse effects on aquatic resources
would result from discharges associated with mining the Pebble deposit or that USACE intended to take
corrective action to prevent unacceptable adverse effects satisfactory to the EPA Region 10 Regional
Administrator. Consistent with EPA's Section 404(c) regulations, EPA requested that the Parties respond
by February 11, 2022. On January 29, 2022, PLP requested a total of 45 days—through March 28,
2022—to provide its submission. EPA granted this request and provided the same extension to all
Parties.
EPA Region 10 met with Chuchuna Minerals on February 9, 2022, and with PLP on February 18, 2022.
On March 28, 2022, ADNR, PLP, and Chuchuna Minerals separately provided information as part of the
initial Section 404(c) consultation period. In these submittals, ADNR, PLP, and Chuchuna Minerals raised
several legal, policy, scientific, and technical issues, including questions regarding continued reliance on
the 2014 Proposed Determination; EPA's authority and justification for undertaking a Section 404(c)
review at this time; whether the 2020 Mine Plan's potential impacts on fishery areas warrant review
pursuant to Section 404(c); and whether a Section 404(c) action would violate the rights established in
the Alaska Statehood Act (ASA), Cook Inlet Land Exchange Act (CILEA), Alaska National Interest Lands
Conservation Act (ANILCA), ANCSA, and the Federal Land Policy and Management Act (FLPMA).
29 EPA Region 10 included Chuchuna Minerals in this notification step because USACE's FEIS for the 2020 Mine Plan
indicates that discharges associated with mining the Pebble deposit could expand in the future into portions of
areas where Chuchuna Minerals holds mining claims.
Recommended Determination
2-18
December 2022
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Section 2
Project Description and Background
USACE did not request a meeting or provide information as part of this initial Section 404(c)
consultation period.
Below is a brief summary of the issues raised in responses to EPA Region 10's January 27, 2022,
notification letters and a brief summary of EPA's assessment of the information.
• Continued reliance on the 2014 Proposed Determination, PLP referred to the 2014 Proposed
Determination as "obsolete," and PLP and ADNR indicated that it would not be appropriate for EPA
Region 10 to continue to rely on the document. EPA Region 10 recognizes that the scientific and
technical record for the development of a mine at the Pebble deposit has evolved since it issued the
2014 Proposed Determination and, as stated in its November 23, 2021 Federal Register Notice,
agreed that EPA should consider information that had become available since the Agency issued the
2014 Proposed Determination in any CWA Section 404(c) review process for the Pebble deposit
area. Accordingly, the 2014 Proposed Determination was extensively revised based on EPA Region
10's consideration of information that had become available since the issuance of the 2014
Proposed Determination. Further revisions have been made in this recommended determination.
• EPA's authority and justification for undertaking a Section 404(c) review at this time, PLP took the
position that EPA's use of CWA Section 404(c) now is unnecessary because EPA could use it later if
USACE's permit denial is overturned, or if a new permit application is submitted in the future. ADNR
took the position that use of CWA Section 404(c) would be premature because it believes USACE's
permit denial inappropriately terminated the permit review process and that "critical information
on the effects and measures the agencies would employ to avoid and minimize [project] impacts was
not completed or published." EPA Region 10 has fully considered these issues and provides its
rationale for pursuing a CWA Section 404(c) review at this time in Section 2.2.3 of this
recommended determination.
• Whether the 2020 Mine Plan's potential impacts on fishery areas warrant review pursuant to
Section 404(c). ADNR, PLP, and Chuchuna Minerals questioned the basis for EPA Region 10's
concerns that a mine at the Pebble deposit could adversely affect fishery areas. ADNR and PLP
provided quotes from the 2020 Mine Plan's FEIS, which suggest that the 2020 Mine Plan's impacts
on fishes would not be "measurable." As discussed in detail in Sections 3 and 4, as well as in
Appendix B, of this recommended determination, EPA Region 10 believes that information in the
FEIS and other parts of the record indicates that discharges of dredged or fill material associated
with the 2020 Mine Plan would be likely to result in unacceptable adverse effects on fishery areas.
• Whether a Section 404(c) action in this case would violate the rights established in the ASA, C1LEA,
AN1LCA, ANCSA, and FLPMA. ADNR and PLP took the position that any attempt by EPA to preclude
development within this area would violate the statutory compromise established in the ASA, CILEA,
and ANILCA because the State of Alaska selected the lands where the Pebble deposit is located for its
potential mining development and because ANCILA requires federal agencies to cooperate with the
state to balance the national interest in Alaska's natural resources with recognition of Alaska's
interests. For similar reasons, ADNR and PLP also took the position that restricting development of
Recommended Determination
2-19
December 2022
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Section 2
Project Description and Background
the Pebble deposit would run afoul of ANCSA because Alaska Native Corporations are required to
develop and manage their lands to the benefit of their shareholders and a mine at the Pebble deposit
would provide economic opportunity in the area. ADNR also argued that EPA's action would violate
FLPMA by effectively withdrawing greater than 5,000 acres from mineral development without
congressional approval. Nothing in the ASA, CILEA, ANILCA, ANCSA, or FLPMA, nor any other
relevant authority, precludes the application of a duly enacted federal law, including Section 404(c)
of the CWA, nor does any such law serve as a barrier to EPA's use of Section 404(c) of the CWA to
prohibit or restrict discharges of dredged or fill material from mining the Pebble deposit into waters
of the United States.
After fully considering the March 28, 2022 submittals from ADNR, PLP, and Chuchuna Minerals, the EPA
Region 10 Regional Administrator was not satisfied that no unacceptable adverse effect could occur or
that adequate corrective action could be taken to prevent an unacceptable adverse effect. Thus, EPA
Region 10 decided that the appropriate next step in this CWA Section 404(c) process was the
publication of a revised proposed determination.
On May 26, 2022, EPA Region 10 published in the Federal Register a notice of availability for its
proposed determination under Section 404(c) of the CWA to prohibit and restrict the use of certain
waters in the SFK, NFK, and UTC watersheds as disposal sites for the discharge of dredged or fill
material associated with mining the Pebble deposit. The notice announced public hearings on the
proposed determination (87 FR 32021, May 26, 2022) and started a public comment period that was
scheduled to end on July 5, 2022.
On June 16 and 17, 2022, EPA Region 10 held three public hearings (in-person hearings in Dillingham
and Iliamna, and one virtual hearing) on the proposed determination. More than 186 people
participated in the three hearings, 111 of whom provided oral statements.
EPA Region 10 received several communications regarding an extension of the comment period,
including requests to extend the comment period by 60 days and 120 days. EPA Region 10 also received
requests not to extend the public comment period. EPA Region 10 considered each of these requests and
found good cause existed pursuant to 40 CFR 231.8 to extend the public comment period through
September 6, 2022, to provide sufficient time for all parties to meaningfully comment on the proposed
determination and supporting documents. On June 30, 2022, a notice announcing extension of the public
comment period and public hearing comment period was published in the Federal Register (87 FR
39091, June 30, 2022).
On September 6, 2022, EPA Region 10 published in the Federal Register a notice to extend the period for
the EPA Region 10 Regional Administrator to evaluate public comments. EPA's regulations at 40 CFR
231.5(a) require that, within 30 days after the conclusion of public hearings (but not before the end of
the comment period), the Regional Administrator either withdraw the proposed determination or
prepare a recommended determination. Because the date of the last public hearing (June 17, 2022) was
more than 30 days before the close of the public comment period (September 6, 2022), EPA would not
have had time to review any of the public comments before the regulations required it to make its next
Recommended Determination
2-20
December 2022
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Section 2
Project Description and Background
decision. Accordingly, EPA Region 10 found good cause existed pursuant to 40 CFR 231.8 to extend the
time period provided in 40 CFR 231.5(a) to either withdraw the proposed determination or to prepare a
recommended determination through no later than December 2, 2022, to help ensure full consideration
of the extensive administrative record, including all public comments (87 FR 54498, September 6,
2022). In addition to the testimony taken at the hearings, EPA Region 10 received more than 582,000
written comments during the public comment period. Transcripts from the public hearings and public
comments can be found in the docket for the proposed determination.30
EPA Region 10 completed its review of the extensive administrative record, including all public
comments, and the Regional Administrator decided to prepare a recommended determination. This
recommended determination, along with the administrative record, is being transmitted to EPA's
Assistant Administrator for Water for review and final action.
2.2.3 Authority and Justification for Undertaking a Section 404(c)
Review at this Time
Consistent with Congressional intent that EPA have authority to prevent unacceptable adverse effects on
specific aquatic resources, Congress provided broad authority to EPA to decide whether or when to use
its Section 404(c) authority. Section 404(c) authorizes EPA to act "whenever" it makes the required
determinations under the statute. As a result, EPA may use its CWA Section 404(c) authority "at any
time," including before a permit application has been submitted, at any point during the permitting
process, or after a permit has been issued (33 U.S.C. 1344(c); 40 CFR 231.1(a), (c); Mingo Logan Coal Co.
v. EPA, 714 F.3d 608, 613 (DC Cir. 2013)).
Relationship to USACE Permitting Process, Section 404(c) provides EPA with independent authority,
separate and apart from the USACE permitting process, to review and evaluate potential discharges of
dredged or fill material into waters of the United States. While the statutory language in Section 404(b)
expressly makes USACE's authority "subject to subsection (c)," there is no comparable text in Section
404(c) that constrains EPA's authority. The statute and EPA's CWA Section 404(c) implementing
regulations provide USACE with a consultation role when EPA uses its Section 404(c) authority.
Furthermore, EPA's determination of unacceptable adverse effects under Section 404(c) is not
coterminous with the requirements that apply to USACE's permitting decisions.
Nothing in the CWA or EPA's CWA Section 404(c) regulations precludes EPA from exercising its
authority where USACE has denied a permit. Although EPA's 1979 preamble to the Section 404(c)
regulations recognized that EPA may choose not to exercise its authority in instances "where the
Regional Administrator also has reason to believe that [the] permitting authority will deny the permit"
because "a 404(c) proceeding would be unnecessary," that was a statement of policy rather than an
indication of a limitation on EPA's authority (44 FR 58079, October 9,1979). Moreover, in this instance,
PLP filed an administrative appeal of USACE's permit denial on January 19, 2021. USACE's review of this
30 Information regarding the proposed determination can be found in the docket for this effort at
www.regulations.gov, see docket ID No. EPA-R10-OW-2022-0418.
Recommended Determination
2-21
December 2022
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Section 2
Project Description and Background
appeal is ongoing, and USACE has not stated when its review will be completed. EPA's use of its 404(c)
authority is independent from USACE's timing and actions of a permit denial. Furthermore, in this
recommended determination, EPA Region 10 has concluded that each of the impacts on aquatic
resources identified in Sections 4.2.1 through 4.2.4 would be likely to, independently, result in
unacceptable adverse effects. That finding is distinguishable from the USACE permit denial, in which
USACE reached its conclusions based on consideration of total project impacts on aquatic resources.
Relationship between CWA Section 404(c) and CWA Section 404(q) Process. EPA's CWA Section
404(c) regulations authorize the Regional Administrator to initiate the CWA Section 404(c) process
"after evaluating the information available to him, including any record developed under the section 404
referral process" (40 CFR 231.3(a)). EPA's regulations include a comment, which states that "[i]n cases
involving a proposed disposal site for which a permit application is pending, it is anticipated that the
procedures of the section 404 referral process will normally be exhausted prior to any final decision of
whether to initiate a 404(c) proceeding" (see Comment at 40 CFR 231.3(a)(2)). EPA has explained that
the reference to the "404 referral process" in the regulations is now manifested as the coordination
processes EPA and USACE have established under CWA Section 404(q) (84 FR 45749, 45752, August 30,
2019).31
All that is required in EPA's CWA Section 404(c) regulations concerning 404(q) is that EPA consider any
information generated during the Section 404(q) MOA interagency coordination process, if applicable.
The statement is also a statement of policy that in no way constrains EPA's legal authority under CWA
Section 404(c). Nothing in the statute or EPA's regulations restricts EPA to considering information or
concerns raised during the Section 404(q) elevation process, if any. Indeed, the Section 404(q) MOA
itself recognizes that it does not constrain EPA's statutory authority under CWA Section 404(c): "[t]his
agreement does not diminish either Army's authority to decide whether a particular individual permit
should be granted, including determining whether the project is in compliance with the Section
404(b)(1) Guidelines, or the Administrator's authority under Section 404(c) of the Clean Water Act"
(EPA and DOA 1992: Part I, paragraph 5).
EPA Policy and Precedent Regarding Use of Its CWA Section 404(c) Authority. EPA has used its
Section 404(c) authority judiciously, including in instances before a permit application has been
submitted, at various stages during the permitting process, and after permit issuance. In the 50 years
since Congress enacted CWA Section 404(c), EPA has only initiated the process 30 times and only issued
13 final determinations. Each instance where EPA initiated a CWA Section 404(c) process has involved
EPA's case-by-case determination of when and how to exercise its CWA Section 404(c) authority based
on the specific facts of each situation consistent with applicable statutory and regulatory requirements.
EPA's 1979 preamble to the Section 404(c) regulations includes statements describing EPA's general
policy intentions regarding the use of its Section 404(c) authority. It states the following:
31 See footnote 27 in Section 2.
Recommended Determination
2-22
December 2022
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Section 2
Project Description and Background
EPA's announcement of intent to start a 404(c) action will ordinarily be preceded by an objection to the
permit application, and under § 325.8 such objection serves to halt issuance of the permit until the
matter is resolved The promulgation of regulations under 404(c) will not alter EPA's present
obligations to make timely objections to permit applications where appropriate. It is not the Agency's
intention to hold back and then suddenly to spring a veto action at the last minute. The fact that 404(c)
may be regarded as a tool of last resort implies that EPA will first employ its tool of'first resort,' e.g.,
comment and consultation with the permitting authority at all appropriate stages of the permit process
(44 FR 58080, October 9,1979).
The clear intention behind this policy is that EPA voice any concerns it has throughout the process. EPA
has done that here, as summarized below.
EPA's actions throughout the entire Pebble Mine project history, including during the USACE permitting
process, are consistent with the general policy articulated in the 1979 preamble. EPA employed its tools
of first resort, including comment and consultation with USACE during the permitting process. EPA also
initiated the CWA Section 404(q) process by providing USACE a CWA Section 404 "3a" letter on July 1,
2019, out of concern regarding "the extent and magnitude of the substantial proposed impacts to
streams, wetlands, and other aquatic resources that may result, particularly in light of the important role
these resources play in supporting the region's valuable fishery resources" (EPA 2019: Page 3). As part
of the CWA Section 404(q) MOA dispute resolution process, EPA engaged in 12 weeks of coordination
with USACE to evaluate the 2020 Mine Plan for compliance with the Section 404(b)(1) Guidelines, from
March 2020 through May 2020. On May 28, 2020, EPA sent a letter to USACE that had the effect of
discontinuing the formal CWA Section 404(q) MOA dispute resolution process. In its letter, EPA
explained that the "[USACE] has demonstrated its commitment to the spirit of the dispute resolution
process pursuant to the 1992 Memorandum of Agreement between EPA and the Department of the
Army regarding CWA Section 404(q) by the extensive engagement with the EPA over the recent months"
and "recent commitment to continue this coordination into the future, outside of the formal dispute
process." The letter recognized that although there was not a need at that time for a formal dispute
process, substantive discussions among USACE, EPA, and USFWS regarding compliance with the
Guidelines were ongoing and the agencies were continuing to discuss and raise concerns.
Timing of EPA's Action, Congress enacted CWA Section 404(c) to provide EPA the ultimate authority, if
it chooses on a case-by-case basis, to make decisions regarding disposal sites for dredged and fill
material discharges under CWA Section 404 (Mingo Logan Coal Co. v. EPA, 714 F.3d 608, 612-13 (D.C.
Cir. 2013)). EPA Region 10 has reviewed the available information,32 including the relevant portions of
the USACE permitting record, and this information supports the findings reported in this recommended
determination.
By acting now, EPA clarifies its assessment of the effects of discharges of dredged or fill material
associated with the construction and routine operation of the 2020 Mine Plan in light of the importance
32 The available information includes, among other things, pre-CWA Section 404 permit application and advance
NEPA coordination meetings beginning in 2004; NDM's preliminary mine plans submitted to the SEC (Ghaffari et al.
2011, SEC 2011); PLP's initial and supplemental Environmental Baseline Documents (PLP 2011, PLP 2018a); EPA's
BBA (EPA 2014); PLP's CWA Section 404 permit application (PLP 2017, PLP 2020b); and USACE's FEIS and ROD
regarding PLP's permit application (USACE 2020a, USACE 2020b).
Recommended Determination
2-23
December 2022
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Section 2
Project Description and Background
of the anadromous fishery areas at issue and, therefore, promotes regulatory certainty for all
stakeholders. If EPA acts now, based on an extensive and carefully considered record, EPA, USACE, and
the regulated community can also avoid unnecessary expenditure of resources. The federal government,
the State of Alaska, federally recognized tribal governments, PLP, and many interested stakeholders
have devoted significant resources over many years of engagement and review. Considering the
extensive record, it is not reasonable or necessary to engage in one or more additional multi-year NEPA
and CWA Section 404 processes for future plans33 that propose to discharge dredged or fill material
associated with mining the Pebble deposit in the SFK, NFK, or UTC watersheds that would be likely to
result in effects that are the same as, or similar or greater in nature and magnitude to the effects of the
2020 Mine Plan. Ultimately, recommending the prohibition and restriction now provides the most
effective, transparent, and predictable protection of valuable anadromous fishery areas in the SFK, NFK,
and UTC watersheds against unacceptable adverse effects.
33 USACE's denial of PLP's permit application does not address any other plan to mine the Pebble deposit that
would have adverse effects the same as, or similar or greater in nature and magnitude to the 2020 Mine Plan.
Recommended Determination
December 2022
2-24
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The Bristol Bay watershed represents a largely pristine, intact ecosystem with outstanding ecological
resources. It is home to at least 29 fish species, more than 40 terrestrial mammal species, and more than
190 bird species (Woody 2018). This ecological wealth supports a number of sustainable economies that
are of vital importance to the region, including subsistence, commercial, and sport fishing; subsistence
and sport hunting; and non-consumptive recreation. The undisturbed habitats of the Bristol Bay
watershed support one of the last salmon-based cultures in the world (EPA 2014: Appendix D), and the
subsistence way of life in this region is irreplaceable. Between 2013 and 2019, the annual economic
output generated by Bristol Bay's wild salmon resources was estimated at more than $1 billion (Wink
Research and Consulting 2018, McKinley Research Group 2021), with total economic value (including
subsistence uses) estimated at more than $2 billion in 2019 (McKinley Research Group 2021).
The following sections consider the Bristol Bay watershed's ecological resources, with particular focus
on the region's fish habitats and populations and the watershed characteristics that support these
resources. Given the connected and spatially nested structure of watersheds (EPA 2015), the migratory
nature of many of the region's fish populations, and the importance of evaluating fish-habitat
relationships across spatial scales (Bryant and Woodsmith 2009, Jackson and Fahrig 2015, Hale et al.
2019), these ecological resources are considered at multiple geographic scales.
The Pebble deposit is located in the Bristol Bay watershed, in the headwaters of tributaries to both the
Nushagak and Kvichak Rivers. The three tributaries that originate within the Pebble deposit are the SFK,
which drains the western part of the Pebble deposit area and converges with the NFK west of the Pebble
deposit; the NFK, located immediately west of the Pebble deposit; and UTC, which drains the eastern
portion of the Pebble deposit and flows into the Kvichak River via Iliamna Lake.34 The SFK, NFK, and
UTC watersheds are the areas that would be most directly affected by mine development at the Pebble
deposit. Streams and wetlands in each of these watersheds provide habitat for five species of Pacific
salmon and numerous other fish species. Each of these headwater watersheds also supports fish
habitats and populations in larger downstream systems via contributions of water, organisms, organic
matter, and other resources.
34 The SFK comprises two 12-digithydrologic unit codes (HUCs): the Headwaters Koktuli River (190303021101)
and the Upper Koktuli River (109303021102). The NFK comprises two 12-digit HUCs: Groundhog Mountain
(190303021103) and 190303021104 (located immediately west of the Pebble deposit). UTC represents one 10-
digitHUC (1903020607).
Recommended Determination 2 ^ December 2022
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Section 3
Importance of the Region's Ecological Resources
3.1 Physical Setting
Bristol Bay is a large gulf of the eastern Bering Sea in southwestern Alaska. The land area draining to
Bristol Bay consists of six major watersheds—from west to east, the Togiak, Nushagak, Kvichak
(including the Alagnak), Naknek, Egegik, and Ugashik River watersheds—and a series of smaller
watersheds draining northward along the Alaska Peninsula (Figure ES-1). The Pebble deposit is located
in the headwaters of tributaries to both the Nushagak and Kvichak Rivers; together, the watersheds of
the Nushagak and Kvichak Rivers account for approximately half of the land area in the Bristol Bay
watershed (USACE 2020a: Section 3.24).
Detailed information on the Bristol Bay watershed's physical setting, in terms of physiography,
hydrologic landscapes, and seismicity, can be found in Chapter 3 of the BBA (EPA 2014). One component
of the watershed's physical setting, however, is particularly important to note: the watersheds draining
to Bristol Bay provide intact, connected, and free-flowing habitats from headwaters to ocean. Long, free-
flowing rivers are globally rare (Grill et al. 2019). Unlike most other areas supporting Pacific salmon
populations in North America, the Bristol Bay watershed is undisturbed by significant human
development and impacts. It is located in one of the last remaining virtually roadless areas in the United
States (EPA 2014: Chapter 6). Large-scale, human-caused modification of the landscape—a factor
contributing to extinction risk for many native salmonid populations (Nehlsen et al. 1991)—is absent,
and development in the watershed consists of only a small number of towns, villages, and roads. The
Bristol Bay watershed also encompasses Iliamna Lake, the largest lake in Alaska and the largest
undeveloped lake in the United States.
The primary human manipulation of the Bristol Bay ecosystem is the marine harvest of roughly 50 to 70
percent of salmon returning to spawn (Kendall et al. 2009, EPA 2014: Chapter 5). Management of
Alaska's salmon fisheries is geared toward maintenance of a sustainable fishery through protection of its
wild salmon populations, or stocks (5 AAC 39.200, 5 AAC 39.220, 5 AAC 39.222, 5 AAC 39.223). A key
goal of ADF&G's policy for the management of sustainable salmon fisheries is "to ensure conservation of
salmon and salmon's required marine and aquatic habitats" (5 AAC 39.222), highlighting the importance
of maintaining sustainable salmon-based ecosystems. Fishery management in Bristol Bay is unique in
part because no hatchery fishes are reared or released in the watershed, whereas approximately 5
billion hatchery-reared juvenile Pacific salmon are released annually across the North Pacific (Irvine et
al. 2012). This lack of hatchery fishes in the Bristol Bay region is notable, given the economic investment
that rearing and releasing hatchery fishes requires and the fact that its benefits are highly variable and
difficult to quantify (Naish et al. 2008). Hatchery fishes also can have significant adverse effects on wild
fish populations (e.g., Levin et al. 2001, Araki et al. 2009, Rand et al. 2012, Evenson et al. 2018, Tillotson
et al. 2019).
Recommended Determination
3-2
December 2022
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Section 3
Importance of the Region's Ecological Resources
3.2 Aquatic Habitats
The Bristol Bay region encompasses complex combinations of physiography, climate, geology, and
hydrology, which interact to control the amount, distribution, and movement of water through a
landscape shaped by processes such as tectonic uplift, glaciation, and fluvial erosion and deposition.
Ultimately, these factors result in a landscape marked by abundant, diverse freshwater habitats. These
diverse habitats, in conjunction with the enhanced ecosystem productivity associated with anadromous
salmon runs, support a high level of biological complexity (biocomplexity) that contributes to the
environmental integrity and resilience of the Bristol Bay watershed's ecosystems (Section 3.3.3)
(Schindler et al. 2010, Ruff et al. 2011, Lisi et al. 2013, Schindler et al. 2018, Brennan et al. 2019).
This section presents key aspects of the region's aquatic habitats, in terms of characteristics that
contribute to their quality and diversity, the quantity and types of streams and wetlands found in the
region, and their importance in the larger landscape. Together, these spatially and temporally variable
aquatic habitats create the dynamic freshwater ecosystem mosaic (Mushet et al. 2019) critical to
maintaining the region's exceptional salmon populations, as well as other fish and wildlife populations.
According to the Anadromous Waters Catalog (ADF&G 2022c), fish habitat is "any area on which fish
depend, directly or indirectly, during any stage of their life cycle." For salmon, this includes spawning
habitats, where adults deposit and fertilize eggs; rearing habitats, where fertilized eggs incubate and
juveniles feed, grow, and overwinter as they develop into adults; and migratory habitats, through which
juveniles and adults predictably and purposefully move to complete their life cycles (ADF&G 2022c).
Habitat needs vary with season and salmon life stage (Bjornn and Reiser 1991), and events occurring
during one life stage continue to influence both individuals and populations in later life stages (Marra et
al. 2015). As a result, continued productivity of the region's salmon populations depends on diverse,
high-quality, and proximally located aquatic habitats that support all freshwater salmon life stages.
3.2.1 Quantity and Diversity of Aquatic Habitats
In general, conditions in the Bristol Bay watershed are highly favorable for Pacific salmon. The region
encompasses an abundant and diverse array of aquatic habitats (Section 3.2) that in turn support a
diverse salmonid assemblage (Section 3.3). Together, these factors result in high degrees of phenotypic
and genotypic diversity across the region's salmon populations. This biocomplexity produces the
asynchronous dynamics that stabilize the overall portfolio of salmon returns to the region (Section
3.3.3).
In the Nushagak and Kvichak River watersheds, freshwater habitats range from headwater streams to
braided rivers, small ponds to large lakes, and side channels to off-channel alcoves. Overall physical
habitat complexity is higher in the Bristol Bay watershed than in many other systems supporting
Sockeye Salmon populations. Of 1,509 North Pacific Rim watersheds, the Kvichak, Wood, and Nushagak
(exclusive of Wood) Rivers (Figure ES-2) ranked third, fourth, and forty-fourth, respectively, in physical
habitat complexity, based on an index including variables such as lake coverage, stream junction density,
floodplain elevation and density, and human footprint (Luck et al. 2010, RAP 2011).
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Importance of the Region's Ecological Resources
Lakes and associated tributary and outlet streams are key spawning and rearing areas for Sockeye
Salmon. Lakes cover relatively high percentages of watershed area in the Bristol Bay region, with
7.9 percent lake cover for the Bristol Bay watershed and 13.7 percent lake cover for the Kvichak River
watershed within the larger Bristol Bay watershed (RAP 2011). In other North Pacific river systems
supporting Sockeye Salmon populations, from northern Russia to western North America, these values
tend to be much lower (0.2 to 2.9 percent) (RAP 2011). Relatively low watershed elevations and the
absence of artificial barriers to migration (e.g., dams and roads) mean that not only are streams, lakes,
and other aquatic habitats abundant in the Bristol Bay region, but they also tend to be accessible to
anadromous salmonids (EPA 2014: Appendix A).
Gravel is an essential substrate for salmon spawning and egg incubation (Bjornn and Reiser 1991, Quinn
2018). Specific substrate and hydraulic requirements vary slightly by species (EPA 2014: Appendix A),
but stream-spawning salmon generally require relatively clean gravel-sized substrates with interstitial
flow, and sufficient bed stability to allow eggs to incubate in place for months prior to fry emergence
(Quinn 2018). In the Bristol Bay watershed, gravel substrates are abundant (EPA 2014: Chapter 7). The
Pebble deposit area is heavily influenced by past glaciation (PLP 2011: Chapter 3), and unconsolidated
glacial deposits cover most of the area's lower elevations (Detterman and Reed 1973). As a result, the
SFK, NFK, and UTC stream valleys have extensive glacial sand and gravel deposits (PLP 2011:
Chapter 8).
A key aspect of the Bristol Bay watershed's aquatic habitats is the importance of groundwater exchange.
Because salmon rely on clean, cold water flowing over and upwelling and downwelling through porous
gravel for spawning, egg incubation, and rearing (Bjornn and Reiser 1991), areas of groundwater
exchange create high-quality salmon habitat (EPA 2014: Appendix A). For example, densities of
beach-spawning Sockeye Salmon in the Wood River watershed (within the larger Nushagak River
watershed) were highest at sites with strong groundwater upwelling and zero at sites with no upwelling
(Burgner 1991). Significant portions of the Nushagak and Kvichak River watersheds, including the
Pebble deposit area, contain coarse-textured glacial drift with abundant, high-permeability gravels and
extensive connectivity between surface waters and groundwater (EPA 2014: Chapter 3).
Groundwater is the source of baseflow in most streams draining the Pebble deposit area (Rains 2011,
USACE 2020a: Section 3.17). Groundwater contributions to streamflow, along with the influence of
run-of-the-river lakes, support flows in the region's streams and rivers that are more stable than those
typically observed in many other salmon streams (e.g., in the Pacific Northwest or southeastern Alaska).
This results in more moderated streamflow regimes with lower peak flows and higher baseflows,
creating a less temporally variable hydraulic environment (EPA 2014: Figure 3-10). Interactions
between surface waters and groundwater in the SFK, NFK, and UTC watersheds are complex and depend
on factors such as local soil type and land and water table gradients. These watersheds include reaches
that gain water from groundwater and reaches that lose water to groundwater, with hyporheic flows
occurring at very local scales (USACE 2020a: Section 3.17).
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This groundwater-surface water connectivity also has a strong influence on stream thermal regimes in
the Nushagak and Kvichak River watersheds, providing a moderating influence against both summer
heat and winter cold extremes. Average monthly stream water temperatures in the Pebble deposit area
in July or August can range from 6°C to 16°C, and temperatures do not uniformly increase with
decreasing elevation (PLP 2011: Appendix 15.IE, Attachment 1). This spatial variability in temperatures
in the Pebble deposit area is consistent with streams influenced by a variety of thermal modifiers,
including groundwater inputs, upstream lakes, and tributary contributions (Mellina et al. 2002,
Armstrong et al. 2010). Longitudinal temperature profiles from August and October indicate that the
mainstem SFK and NFK reaches just downstream of the tributaries draining the potential mine area
experience significant summer cooling and winter warming compared to adjacent upstream reaches
(PLP 2011: Chapter 9), suggesting significant groundwater contributions. Consistent winter
observations of ice-free conditions in the area's streams also suggest the presence of upwelling
groundwater in strongly gaining reaches of the SFK, NFK, and UTC (PLP 2011: Chapter 7, Woody and
Higman 2011). Areas of groundwater downwelling are also important to fish and aquatic species and
are documented to occur in the SFK, NFK, and UTC watersheds (USACE 2020a: Section 3.17).
These groundwater-surface water interactions and their influence on water temperature are extremely
important for fishes, particularly salmon. Water temperature controls the metabolism and behavior of
salmon and, if temperatures are stressful, fishes can be more vulnerable to disease, competition,
predation, or death (McCullough et al. 2009). The State of Alaska has maximum temperature limits for
salmon migration routes, spawning and rearing areas, and fry incubation areas (ADEC 2020). However,
summer is not the only period of temperature sensitivity for salmon (Poole et al. 2004). For example,
small temperature changes during salmon egg incubation in gravels can alter the timing of emergence
by months (Brannon 1987, Beacham and Murray 1990, Quinn 2018). Groundwater moderates winter
temperatures, which strongly control egg development, egg hatching, and emergence timing (Brannon
1987, Hendry et al. 1998). Groundwater contributions that maintain water temperatures above 0°C are
critical for maintaining winter refugia in streams that might otherwise freeze (Power et al. 1999). Thus,
winter groundwater connectivity may be critical for fishes in such streams (Cunjak 1996, Huusko et al.
2007, Brown et al. 2011).
Since the timing of migration, spawning, and incubation are closely tied to seasonal water temperatures,
groundwater-influenced thermal heterogeneity can also facilitate diversity in run timing and other
salmon life-history traits (Hodgson and Quinn 2002, Rogers and Schindler 2011, Ruff et al. 2011). Any
thermal regime alterations resulting from changes in groundwater-surface water connectivity could
disrupt life-history timing cues and result in mismatches between fishes and their environments that
adversely affect survival (Angilletta et al. 2008).
In terms of water quality, streams draining the Pebble deposit area tend to have near-neutral pH, with
low conductivity, alkalinity, dissolved solids, suspended solids, and dissolved organic carbon (USACE
2020a: Section 3.18). In these respects, they are characteristic of undisturbed streams. However, as
would be expected for a metalliferous site, levels of sulfate and some metals (copper, molybdenum,
nickel, and zinc) are elevated, particularly in the SFK. Copper levels in approximately 40 percent of
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samples from the SFK exceeded Alaska's chronic water quality standard (USACE 2020a: Section 3.18).
However, most exceedances were in or close to the deposit area, and the number and magnitude of
exceedances decreased with distance downstream (USACE 2020a: Appendix K3.18).
In summary, the Bristol Bay watershed in general, and the SFK, NFK, and UTC watersheds specifically,
provide diverse and productive habitat for salmon and other fishes. Suitable substrates for salmon
spawning, egg incubation, and rearing are abundant. Extensive connectivity between groundwater and
surface waters creates and maintains a variety of streamflow and thermal regimes across the region,
resulting in favorable spawning and rearing habitats for salmonids and helping to support diverse fish
assemblages.
3.2.2 Streams
The Nushagak and Kvichak River watersheds contain over 33,000 miles (54,000 km) of streams,
approximately 667 miles (1,085 km) of which are in the SFK, NFK, and UTC watersheds. The stream and
river habitats of the SFK, NFK, and UTC watersheds can be characterized in terms of attributes that
generally represent fundamental aspects of the physical and geomorphic settings in streams. Evaluation
of stream and river habitats within the SFK, NFK, and UTC watersheds based on these attributes
provides important context for how these streams and rivers contribute to fish habitats (Burnett et al.
2007, Shallin Busch et al. 2013). EPA (2014) describes stream and river valley attributes for each of the
52,277 stream and river reaches in the Nushagak and Kvichak River watersheds documented in the
National Hydrography Dataset (NHD) (USGS 20 1 2).35 Three key attributes were estimated for each
reach: mean channel gradient, mean annual streamflow, and percentage of flatland in the contributing
watershed lowland (EPA 2014: Chapters 3 and 7). Stream reaches were then categorized according to
each attribute to evaluate the relative suitability of these reaches as fish habitat.36
Because conditions at salmon spawning sites play a large role in determining the survival of eggs and
rearing alevins, the geomorphic and hydrologic conditions at spawning sites are key determinants of
population success (Beechie et al. 2008, Gibbins et al. 2008). Results of the stream reach classification
show that a high proportion of stream channels in the SFK, NFK, and UTC watersheds possess the broad
geomorphic and hydrologic characteristics that create stream and river habitats highly suitable for
fishes such as Pacific salmon, Rainbow Trout, and Dolly Varden: low stream gradients, mean annual
streamflows greater than or equal to 5.3 ft3/s (0.15 m3/s), and at least 5 percent flatland in lowland (an
indicator of the potential for floodplain development) (EPA 2014: Chapter 7).
35 Analysis is based on the 2012 iteration of the NHD (USGS 2012); total mapped stream length in the SFK, NFK, and
UTC watersheds changed by only 1 percent between the 2012 and 2021 iterations of the NHD.
36 EPA (2014: Chapters 3 and 7) provides a detailed discussion of the importance of each attribute in determining
fish habitat and the method used to categorize each attribute.
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The substrate and hydraulic conditions required by stream-spawning salmon are most often met in
stream channels with gradients less than 3 percent (Montgomery et al. 1999). Pool-riffle channels have
moderate slopes (<1.5 to 2 percent) and are indicative of quality spawning habitat (Miller et al. 2008,
Buffington et al. 2004). At gradients above 3 percent, the size, stability, and frequency of patches of
suitable spawning substrates are substantially reduced (Montgomery and Buffington 1997). In the SFK,
NFK, and UTC watersheds, low-gradient (<3 percent) channels account for 87 percent of the stream
network, highlighting the availability of quality salmon spawning habitat in this region (Table 3-1).
Mean annual streamflow is a metric of stream size. Pacific salmon in the Bristol Bay region use a wide
range of river and stream sizes for migration, spawning, and/or rearing habitat, but low-gradient
streams of medium size (5.3 to 100 ft3/s [0.15 to 2.8 m3/s] mean annual streamflow) or greater likely
provide high-capacity, high-quality habitats for salmonids (EPA 2014: Chapter 7). Such streams and
rivers account for 34 percent of the stream network in the SFK, NFK, and UTC watersheds (Table 3-1).
However, salmonid species differ in their propensities for small streams. Dolly Varden have been
documented using all stream sizes, including some of the smallest channels. Of the Pacific salmon
species, Coho Salmon are most likely to use small streams for spawning and rearing and have been
observed in many of the smaller streams near the Pebble deposit (Woody and O'Neal 2010). Larger-
bodied Chinook Salmon adults are less likely to access smaller streams for spawning (Quinn 2018),
although each year 12 to 21 percent of radio-tagged Chinook Salmon in the Togiak River watershed
(located southwest of the Nushagak River watershed) spawned in smaller order tributaries (Sethi and
Tanner 2014). Juvenile Chinook Salmon also have been observed in small tributaries where spawning
has not been documented (Bradford et al. 2001, Daum and Flannery 2011, Phillis et al. 2018), including
in smaller streams near the Pebble deposit. In the SFK, NFK, and UTC watersheds, small streams account
for 65 percent of the stream network (Table 3-1).
Streams in the larger valleys of the SFK, NFK, and UTC watersheds tend to have extensive flat floodplains
or terraces (Table 3-1). These unconstrained channels generally have higher complexity of channel
habitat types and hydraulic conditions and higher frequencies of off-channel habitats such as side
channels, sloughs, and beaver ponds. Such habitat complexity can be beneficial to salmon by providing
diverse spawning and rearing habitats throughout the year (Stanford et al. 2005). For Coho and Chinook
salmon, as well as river-rearing Sockeye Salmon that may overwinter in streams, such habitats may be
particularly valuable by providing unique thermal, foraging, and growth advantages not available to
juveniles in the main channel (Bradford et al. 2001, Huntsman and Falke 2019). In addition, smaller,
steeper streams in the watersheds provide both seasonal (and some year-round) habitat for other fish
species and important nutrient supply to downstream waters (Section 3.2.4).
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Table 3-1. Distribution of stream channel length classified by channel size (based on mean
streamflow), channel gradient, and floodplain potential for streams and rivers in the South
¦ .rn itiTiii: fiYa* ii' bh i n ani m »cn h in n; ii'MiciiTi ¦ • imMa fi ktti rmwiaa r*vfn ens rnu ewjtsthi a Sfiwwii i
Small headwater streamsc
15%
5%
5%
28%
0%
12%
0%
0%
Medium streamsd
14%
6%
0%
3%
0%
1%
0%
0%
Small rivers e
8%
2%
0%
1%
0%
0%
0%
0%
Large riversf
0%
0%
0%
0%
0%
0%
0%
0%
Notes:
a Analysis is based on 2012 iteration of the NHD (USGS 2012); total mapped stream length in the South Fork Koktuli River, North Fork Koktuli
River, and Upper Talarik Creek watersheds changed by only 1 percent between 2012 and 2021 iterations of the NHD.
b FP = high floodplain potential (greater than or equal to five percent of flatland in lowland); NFP = no or low floodplain potential (less than five
percent of flatland in lowland).
c 0-5.3 ft3/s (0-0.15 m3/s); most tributaries in the mine footprints defined in the BBA (EPA 2014: Chapter 6).
d 5.3-100 ft3/s (0.15-2.8 m3/s); upper reaches and larger tributaries of the South Fork Koktuli River, North Fork Koktuli River, and Upper Talarik
Creek.
e 100-1000 ft3/s (2.8-28 m3/s); middle to lower portions of the South Fork Koktuli River, North Fork Koktuli River, and Upper Talarik Creek,
including mainstem Koktuli River.
f >1000 ft3/s (>28 m3/s); the Mulchatna River below the Koktuli River confluence, the Newhalen River, and other large rivers. Note that there are
no large rivers in the SFK, NFK, and UTC watersheds.
3.2.3 Wetlands, Lakes, and Ponds
A thorough inventory of wetland, lake, and pond habitats within the Bristol Bay watershed, or even the
Nushagak and Kvichak River watersheds, has not been completed. However, the National Wetlands
Inventory (NWI) (USFWS 2021) has data for approximately 96 percent of the area encompassed by the
SFK, NFK, and UTC watersheds (Table 3-2). Wetlands comprise roughly 18 percent of the combined area
of the three watersheds, with similar wetland types and proportions found in each watershed (Table 3-
2; Box 3-1).
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Table 3-2. Acreage of wetland habitats in the South Fork Koktuli River, North Fork Koktuli River, and
Upper Talarik Creek w
¦llllKlCUCKllll
Freshwater
emergent
wetland
Non-tidal wetlands dominated by erect, rooted
herbaceous hydrophytes
3,116
(4)
3,532
(5)
4,580
(5)
11,221
(5)
Freshwater
forested/scrub-
shrub wetland
Non-tidal wetlands dominated by either trees greater
than 20 feet in height (forested) or shrubs and tree
saplings less than 20 feet in height (scrub-shrub)
5,693
(8)
12,220
(18)b
6,194
(7)
24,107
(11)
Freshwater pond
Non-tidal wetlands and shallow water (less than 6.6
feet deep) habitats that are at least 20 acres in size,
have either less than 30 percent vegetative cover or a
plant community dominated by species that principally
grow on or below water surface, and have at least 25
percent of substrates less than 2.75 inches in size
931
(1)
1,397
(2)
1,090
(1)
3,418
(1)
Lake
Wetlands and deep-water (deeper than 6.6 feet)
habitats that are situated in topographic depressions,
have less than 30 percent vegetative cover, and are
greater than 20 acres in size
611
(1)
427
(1)
698
(1)
1,737
(1)
Riverine
Wetlands and deep-water (deeper than 6.6 feet)
habitats in natural or artificial channels that contain
flowing water at least periodically
507
(1)
480
(1)
632
(1)
1,619
(1)
TOTAL WETLAND AREA
10,859
(15)
18,056
(26)
13,194
(15)
42,109
(18)
TOTAL WATERSHED AREA
192
69,612
87,547
228,651
Notes:
a Approximately 96 percent of the area within these watersheds has National Wetlands Inventory (NWI) coverage; the 4 percent of the area without
coverage is located in lower elevation areas of the Upper Talarik Creek watershed. Note that individual percentages may not exactly add to total
percentages within and across watersheds due to rounding.
b The data presented in NWI for the western portion of the NFK watershed are an "interim scalable map product" (USFWS 2022a) that "is
considered preliminary and is a compilation of existing data and limited aerial image interpretation rather than an image-based mapping
process" (USFWS 2022b). These preliminary, interim data appear to overestimate the freshwater forested/scrub-shrub wetlands in portions of
the NFK watershed compared to the adjacent areas completed using image-based mapping processes.
Source: USFWS 2021.
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_
i§»
_
_
_
Throughout most of Section 3, we discuss the SFK, NFK, and UTC watersheds in combination because of the
broad similarity of aquatic resources across the three watersheds. Each watershed is unique, but they share
a roughly similar size, a headwater location, and numerous similarities in terms of the types and distribution
of aquatic habitats, their physical and chemical characteristics, and their use by fish populations. Specific
examples of these similarities are provided below.
Types and distribution of aquatic habitats
• The SFK, NFK, and UTC watersheds have similar lengths of total stream miles (relative to their watershed
areas) and similar percentages of total stream miles documented to support anadromous fishes (29-31
percent in each watershed) (Table 3-6).
• Headwaters of all three watersheds contain dense first-order tributary networks that contribute subsidies
of flow, energy, and organic matter to downstream reaches (USACE 2020a: Page 3.24-3).
• Each watershed contains multiple lakes, ponds, and wetlands that provide fish habitat and support
downstream flows (USACE 2020a: Pages 3.16-8 and 3.24-3); similar amounts and types of wetlands are
found in all three watersheds (Table 3-2).
• Floodplain and off-channel habitats, including beaver ponds, are important habitat components in all
three watersheds (USACE 2020a: Table 3-24-3).
Physical and chemical characteristics of the watersheds and their aquatic habitats
• Headwaters of the SFK, NFK, and UTC watersheds have similar terrain and elevation (USACE 2020a:
Table 3.16-1). All three watersheds transition to lower-gradient streams as one moves from headwaters to
downstream areas, and lower stream reaches are similar in terms of gradient and substrate type (USACE
2020a: Table 3.24-2).
• Water temperature and water chemistry parameters are similar across the SFK, NFK, and UTC watersheds
(USACE 2020a: Tables K3.18-7-K3.18-9).
• The SFK, NFK, and UTC have similar mean annual streamflows (relative to their watershed areas), as well
as similar seasonal discharge patterns, with high streamflow in spring and fall and low streamflow in
winter and mid-summer (USACE 2020a: Page 3.16-8, Table K3.16-3).
• Interactions between surface waters and groundwaters are a key component of the aquatic habitats in all
three watersheds. Groundwater seeps are common in the headwaters of the three watersheds (USACE
2020a: Figure 3-17.2), and groundwater discharge is an important component of streamflow and fish
habitat in all three watersheds (USACE 2020a: Pages 3.16-8 and 3.24-4). Groundwater exchange
between the SFK and UTC watersheds has been well documented (USACE 2020a: Page 3.17-4).
Use of aquatic habitats by fishes
• Mainstem reaches of the SFK, NFK, and UTC have all been documented to support important salmon
spawning aggregations (USACE 2020a: Table 3.24-8; Figures 3.24-6, 3.24-10, and 3.24-13).
• Aquatic habitats within each of the three watersheds provide fishery areas that support reproductively
isolated salmon populations (Section 3.3.3), which in turn, contribute to valuable subsistence,
commercial, and recreational fisheries.
The similarities detailed above do not mean that aquatic resources across the SFK, NFK, and UTC
watersheds are interchangeable. The broad components of these headwater watersheds—in terms of the
types and abundance of aquatic habitats, their general physical and chemical characteristics, and the
organisms that use those habitats—are similar. Within each watershed, however, these component pieces
are put together in unique ways, based on the specific characteristics of individual habitats, how those
individual habitats are arranged and connected, and how individual organisms move amongthem. In each
of the three watersheds, similar components combine in different ways to create unique habitat mosaics,
which over thousands of years have resulted in local adaptation of populations, especially anadromous fish
populations, to site-specific conditions in each watershed. As a result, loss or disruption of aquatic habitats
in any of the three watersheds would be expected to result in similar impacts on ecological function.
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It is important to note that the characterization of aquatic habitat area is limited by resolution of the
available NWI data, which tend to underestimate their extents. For example, multiple sources of high-
resolution remote imaging and ground-truthing were used to map streams and wetlands at the mine site
(USACE 2020a). This high-resolution mapping identifies approximately 400 percent more stream miles
than the NHD and approximately 40 percent more wetland acres than the NWI (USFWS 2021) in this
area (see Box 4-3 for additional information on water resources mapping at the mine site). However,
this high-resolution mapping of aquatic resources is not available for the entire SFK, NFK, and UTC
watersheds. Thus, most of the stream length estimates included in this section are based on the most
recent iteration of the NHD (USGS 2021b).
3.2.4 Importance of Headwater Stream and Wetland Habitats to Fish
Headwater streams and wetlands are the small channels and wetland areas located in the upstream
source areas of river networks. The branched nature of river networks means that watersheds are
dominated by headwater streams, in terms of both stream number and stream length (Hill et al. 2014,
Callahan et al. 2015). Small headwater streams make up approximately 65 percent of assessed stream
length in the SFK, NFK, and UTC watersheds (Table 3-1).37 Thus, headwater streams—and their
associated headwater wetlands—are key habitat features in this region. These headwater systems
provide habitat for numerous fish species, as well as supply water, invertebrates, organic matter, and
other resources to larger downstream waters. Because of their large influence on downstream water
flow, water chemistry, and biota, the importance of headwater systems reverberates throughout entire
watersheds downstream (Freeman et al. 2007, Meyer et al. 2007, Fritz et al. 2018, Schofield et al. 2018).
Headwater streams and spring (headwater) wetland habitats are particularly important in establishing
and maintaining fish diversity (Cummins and Wilzbach 2005, Colvin et al. 2019). They support resident
fish assemblages, as well as provide key habitats for specific life stages of migratory fishes. For example,
headwaters provide spawning and nursery areas for fish species that use larger streams, rivers, and
lakes for most of their freshwater life cycles (e.g., Pacific salmon and Rainbow Trout) (Quinn 2018). The
use of headwater streams and wetlands by a variety of fish species has been observed in many aquatic
ecosystems (see Meyer et al. 2007 for a thorough review). Headwater streams in southeastern Alaska
can be an important source area for downstream Dolly Varden populations (Bryant et al. 2004). Foley et
al. (2018) examined the distribution of juvenile Coho Salmon in three headwater streams of the Little
Susitna River, Alaska; they found that juveniles occurred throughout these headwater streams where
stream gradients were less than 4 to 5 percent. In the Nushagak and Kvichak River watersheds,
96 percent of 108 surveyed headwater streams contained fishes, including rearing Coho and Chinook
salmon, adult Coho and Sockeye salmon, Rainbow Trout, Dolly Varden, Arctic Grayling, Round Whitefish,
Burbot, and Northern Pike (Woody and O'Neal 2010).
37 Based on the 2012 iteration of the NHD (USGS 2012); total mapped stream length in the SFK, NFK, and UTC
watersheds changed by only 1 percent between the 2012 and 2021 iterations of the NHD.
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Summer and early fall can provide opportunities for maximum growth for juvenile salmon rearing in
headwater systems, as both stream temperatures and food availability increase (Quinn 2018). Although
seasonal fish distribution patterns are poorly understood for the region, lower-gradient headwater
streams and associated wetlands may also provide important habitat for stream fishes during other
seasons. Thermally diverse habitats in off-channel wetlands can provide rearing and foraging conditions
that may be unavailable in the mainstream channel, increasing capacity for juvenile salmon rearing
(Brown and Hartman 1988, Nickelson et al. 1992, Cunjak 1996, Collen and Gibson 2001, Sommer et al.
2001, Henning et al. 2006, Lang et al. 2006, PLP 2011). Loss of wetlands in more developed regions has
been associated with reductions in habitat quality and salmon abundance, particularly for Coho Salmon
(Beechie et al. 1994, Pess et al. 2002).
Winter habitat availability for juvenile rearing has been shown to limit salmonid productivity in streams
of the Pacific Northwest (Nickelson et al. 1992, Solazzi et al. 2000, Pollock et al. 2004), and may be
limiting for fishes in the SFK, NFK, and UTC watersheds given the relatively cold temperatures and long
winters in the region (Morrow 1980, Reynolds 1997). Overwintering habitats for stream fishes must
provide suitable instream cover, dissolved oxygen, and protection from freezing (Cunjak 1996). Beaver
ponds and groundwater upwelling areas in headwater streams and wetlands in the SFK, NFK, and UTC
watersheds likely meet these requirements. In winter, beaver ponds typically retain liquid water below
the frozen surface, creating important winter refugia for stream fishes (Cunjak 1996). Beaver ponds
provide excellent habitat for rearing salmon by trapping organic materials and nutrients and creating
structurally complex, large-capacity pool habitats with potentially high macrophyte cover, low
streamflow velocity, and/or moderate temperatures (Nickelson et al. 1992, Collen and Gibson 2001,
Pollock et al. 2004, Lang et al. 2006). Additionally, beaver dams, including ponds at a variety of
successional stages, provide a mosaic of habitats for not just salmon but other fish and wildlife species
(e.g., lamprey).
An October 2005 aerial survey of active beaver dams in the Pebble deposit area mapped 113 active
beaver colonies (PLP 2011: Chapter 16:16.2-8). As detailed in Section 3.2.2, the SFK, NFK, and UTC
watersheds are dominated by low-gradient headwater streams. Beavers preferentially colonize
headwater streams—particularly those with gradients less than 6 percent—because of their shallow
depths and narrow widths (Collen and Gibson 2001, Pollock et al. 2003). Beaver ponds provide
important and abundant habitat within the Pebble deposit area and may be particularly important for
overwinter rearing of species such as Coho Salmon and for providing deeper pool habitats for additional
species during low streamflow conditions (PLP 2011: Appendix 15.ID, USACE 2020a: Section 3.24).
The lateral expansion of floodplain wetland habitats during flooding greatly influences habitat
connectivity by determining whether and how long fishes can reach newly created or existing habitats
(Bunn and Arthington 2002). In the Bristol Bay watershed, field observations have indicated the
presence of salmon in stream sites disconnected from surface-water flows (Woody and O'Neal 2010).
Annual floods during spring and fall likely reconnect these habitats through a network of ephemeral
wetlands and streams. The use of these temporary stream and wetland habitats by fishes is not well
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Importance of the Region's Ecological Resources
understood in the Bristol Bay watershed, but they appear to be important in establishing habitat
connectivity.
Inputs of groundwater-influenced streamflow from headwater tributaries likely benefit fishes by
moderating mainstem temperatures and contributing to thermal diversity in downstream waters
(Cunjak 1996, Power et al. 1999, Huusko et al. 2007, Armstrong et al. 2010, Brown et al. 2011, Ebersole
et al. 2015). Such thermal diversity can be an important attribute of stream systems in the region,
providing localized water temperature patches that may offer differing trade-offs for species
bioenergetics. For example, salmon may select relatively cold-temperature sites—often associated with
groundwater upwelling—for spawning, whereas juvenile salmon rearing in those same streams may
take advantage of warm-temperature patches for optimal food assimilation (Armstrong and Schindler
2013). Headwater streams in the SFK and NFK watersheds may provide a temperature-moderating
effect and serve as sources of thermal heterogeneity, providing cooler temperatures in summer and
warmer temperatures in winter.
It has long been recognized that, in addition to providing habitat for stream fishes, headwater streams
and wetlands serve an important role in the stream network by contributing water, nutrients, organic
material, macroinvertebrates, algae, and bacteria downstream to higher-order streams in the watershed
(Vannote et al. 1980, Meyer et al. 2007, Doretto et al. 2020). This is particularly true in dendritic stream
networks like the SFK, NFK, and UTC systems, which have a high density of headwater streams. For
example, Koenig et al. (2019) found that small streams with relatively low primary productivity can
exert a disproportionate effect on overall gross primary productivity in the river network, due to the
large collective surface area of these small channels. Because of their narrow width, headwater streams
also receive proportionally greater inputs of organic material from the surrounding terrestrial
vegetation than larger stream channels (Vannote et al. 1980, Doretto et al. 2020). This material is either
used locally (Tank et al. 2010) or transported downstream to larger streams in the network (Wipfli et al.
2007).
Headwater streams—including streams with only intermittent or ephemeral flow—are important
suppliers of invertebrates and detritus to downstream areas that support juvenile salmonids and other
fishes (Wipfli and Gregovich 2002, Cummins and Wilzbach 2005, Colvin et al. 2019, Hedden and Giddo
2020). In transporting these materials downstream, headwaters provide an important energy subsidy
for juvenile salmonids (Wipfli and Gregovich 2002). For example, Wipfli and Gregovich (2002) found
that fishless headwater streams in southeastern Alaska were a year-round source of invertebrate prey
for salmonids. They estimated that these streams could provide downstream salmonid-bearing habitat
with enough invertebrate prey and detritus to support up to 2,000 juvenile salmonids per kilometer
(Wipfli and Gregovich 2002). Recent experimental studies have also shown that disturbance and
degradation of small tributaries can affect invertebrate populations in downstream reaches (Chara-
Serna and Richardson 2021, Gonzalez and Elosegi 2021).
The export value of headwater streams can be influenced by the surrounding vegetation. For example,
riparian alder (a nitrogen-fixing shrub) was positively related to aquatic invertebrate densities and the
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export rates of invertebrates and detritus in southeastern Alaska streams (Piccolo and Wipfli 2002,
Wipfli and Musslewhite 2004). Riparian vegetation in the Pebble deposit area is dominated by
deciduous shrubs such as willow and alder (USACE 2020a: Section 3.24); thus, these streams are likely
to provide abundant, high-quality detrital inputs to downstream reaches.
Headwater streams can also have high instream rates of nutrient processing and storage, thereby
influencing downstream water chemistry due to relatively large organic matter inputs, high retention
capacity, high primary productivity, bacteria-induced decomposition, and/or extensive hyporheic zone
interactions (Richardson et al. 2005, Alexander et al. 2007, Meyer et al. 2007). In examining network-
wide patterns in water chemistry of the Kuskokwim River, Alaska, French et al. (2020) found that
watershed attributes of headwaters were the best predictor for almost all streamwater constituents
(e.g., nitrate, phosphate, dissolved organic carbon) across the entire network. They concluded that
headwaters are governing river biogeochemistry in this system (French et al. 2020). Similarly, when the
natural flow regimes of headwater streams are altered, adverse effects on downstream water quality
often occur (Colvin et al. 2019). Accurate assessment of these physical and chemical connections
between headwaters and downstream waters—and perhaps more important, their consequences for
the integrity of those downstream waters—should consider aggregate connections over multiple years
to decades (Fritz et al. 2018).
In summary, headwater streams and wetlands play a vital role in maintaining diverse, abundant fish
populations—both by providing important fish habitat and by supplying the energy and other resources
needed to support fishes in connected downstream habitats (Colvin et al. 2019). Headwater streams and
wetlands are abundant in the Pebble deposit area and play a crucial role in supporting local and
downstream fish populations.
3.3 Fish Resources
Given the abundant, diverse, and high-quality freshwater habitats found in the Nushagak and Kvichak
River watersheds, it is not surprising that this region supports world-class fishery resources. This
section considers the fish species found in the Nushagak and Kvichak River watersheds, with particular
focus on the SFK, NFK, and UTC watersheds; life-history, distribution, and abundance information for
these species; the ecological importance of these fish populations, in terms of both maintaining
biocomplexity and diversity at local and global scales and providing nutrient subsidies to habitats; and
the importance of subsistence, commercial, and recreational fisheries in the region. As this section
illustrates, this region supports a robust, diverse fish assemblage of considerable ecological, economic,
and cultural value, and loss of these fish resources could have significant repercussions.
3.3.1 Species and Life Histories
The Bristol Bay watershed is home to at least 29 fish species, representing at least nine different
families. The 29 species documented to occur in the Nushagak and Kvichak River watersheds, as well as
information on their migratory patterns and general abundance, habitat types, and predator-prey
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relationships, are listed in Table 3-3. At least 20 of these species are known to inhabit the SFK, NFK, and
UTC watersheds (USACE 2020a: Section 3.24). The region is renowned for its fish populations, and it
supports world-class fisheries for multiple species of Pacific salmon and other subsistence and game
fishes (Dye and Borden 2018, Halas and Neufeld 2018). These resources generate significant benefit for
commercial fishers (Section 3.3.5), provide nutritional and cultural sustenance for Alaska Native
populations and other residents (Section 3.3.6), and support valued recreational fisheries (Section
3.3.7).
Five species of Pacific salmon spawn and rear in the Bristol Bay watershed's freshwater habitats: Coho
or Silver salmon, Chinook or King salmon, Sockeye or Red salmon, Chum or Dog salmon, and Pink or
Humpback salmon. Because no hatchery fishes are raised or released in the watershed, the Bristol Bay
region supports entirely wild, naturally sustainable fisheries (Section 3.1).
All five salmon species share life-history traits that contribute to their success and significance in the
Bristol Bay region. First, they are anadromous: they hatch in freshwater habitats, migrate to sea for a
period of relatively rapid growth, and then return to freshwater habitats to spawn. Second, the vast
majority of adults undergo extensive homing migrations to return to their natal freshwater habitats to
spawn. Salmon imprint on the chemical signatures of their natal sites throughout their early
development (Dittman and Quinn 1996, Ueda 2019), and use olfactory and other cues to migrate back to
these locations as adults. This homing behavior fosters reproductive isolation, creating distinct, localized
populations that are uniquely adapted to the specific environmental conditions of their natal habitats
(Blair et al. 1993, Dittman and Quinn 1996, Ramstad et al. 2010, Eliason et al. 2011, Zwollo 2018, Smith
and Zwollo 2020) (Section 3.3.3). Finally, each species is semelparous: adults return to their natal
stream to spawn once and then inevitably die. Because adults only have one opportunity to reproduce,
spawning site selection is a critical determinant of their reproductive fitness. Upon their death, adult
salmon release the nutrients incorporated in their bodies into their spawning habitats; this slow release
of marine-derived nutrients provides critical resources for their offspring and many other organisms
(Section 3.3.4).
The seasonality of spawning and incubation is roughly the same for all five Pacific salmon species,
although the timing can vary somewhat by species, population, and region. For example, Coho Salmon
tend to spawn later in the season and have shorter incubation periods (Spence 1995), whereas Sockeye
and Chinook salmon tend to return and spawn earlier in the season. In general, salmon spawn from
summer through fall, and fry emerge from spawning gravels the following spring to summer.
Freshwater habitats used for spawning and rearing vary across and within species, and include
headwater streams, larger mainstem rivers, side- and off-channel wetlands, spring-fed ponds, and lakes
(Table 3-4; Section 3.3.3). Use of lakes is common among salmonids (Arostegui and Quinn 2019a).
Sockeye Salmon are unique among the Pacific salmon species in that most populations rely on lakes as
the primary freshwater rearing habitat ("lake-type" Sockeye Salmon) (Table 3-4), although there are
populations in the Bristol Bay watershed that rear in small streams and rivers ("river-type" Sockeye
Salmon) (Section 3.3.3).
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i the Nushagak and Kvichak River watersheds. Species in bold have been documented
tuii River. North Fork Koktuli River, and Upper Talarik Creek watersheds. (H) indicates sp
-distributed across the Nushagak and Kvichak River watersheds and are or have been targeted
ni(iliKllj0iiT£lir
Salmonids
(Salmonidae)
Bering Cisco
(Coregonus laurettae)
N and A
Very few specific reports
Humpback Whitefish (H)
(C. pidschian)
N and A
Common in large lakes; locally and seasonally
common in large rivers
Feed primarily on aquatic invertebrates (mollusks,
insect larvae), also salmon eggs and small fry
Eaten by other fishes (Northern Pike, Lake Trout);
eggs eaten by Round Whitefish, Arctic Grayling)
Least Cisco
(C. sardinella)
N and A
Locally common in some lakes (e.g., Lake Clark,
morainal lakes near lliamna Lake); less common in
lliamna Lake and large slow-moving rivers, such as
the Chulitna, Kvichak, and lower Alagnak
Feed on aquatic invertebrates (insect larvae,
copepods)
Eaten by other fishes (Lake Trout, Northern Pike,
Burbot) and fish-eating birds
Pygmy Whitefish
(Prosopium coulter: i)
N
Locally common in a few lakes or adjacent streams
Feed on aquatic invertebrates (insect larvae,
zooplankton, mollusks) and whitefish eggs
Eaten by other fish (Lake Trout, Arctic Char, Dolly
Varden) and fish-eating birds
Round Whitefish
(P. cylindraceum)
N
Abundant/widespread throughout larger streams in
upland drainages; notfound in headwaters or
coastal plain areas
Feed on aquatic invertebrates (insect larvae, snails)
and salmon and whitefish eggs
Eaten by other fishes (Burbot, Lake Trout, Northern
Pike)
Coho Salmon (H)
(Oncorhynchus kisutch)
A
Juveniles abundant/widespread in flowing waters of
Nushagak River watershed and in some Kvichak
River tributaries downstream of lliamna Lake;
present in some lliamna Lake tributaries; not
recorded in the Lake Clark watershed
Juveniles feed primarily on aquatic invertebrates
(insect larvae) and salmon eggs and carcasses
Chinook Salmon (H)
(0. tshawytscha)
A
Juveniles abundant and widespread in upland
flowing waters of Nushagak River watershed and in
Alagnak River; infrequent upstream of lliamna Lake
Juveniles feed primarily on aquatic invertebrates
(insect larvae)
Sockeye Salmon (H)
(0. nerka)
A
Abundant
Juveniles feed primarily on zooplankton
Chum Salmon (H)
(0. keta)
A
Abundant in upland flowing waters of Nushagak
River watershed and in some Kvichak River
tributaries downstream of lliamna Lake; rare
upstream of lliamna Lake
-
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Pink Salmon (H)
(0. gorbuscha)
A
Abundant (in even years), with restricted
distribution, in the Nushagak River watershed and in
some Kvichak River tributaries downstream of
lliamna Lake; rare upstream of lliamna Lake
-
Rainbow Trout (H)
(0. my kiss)
N c
Frequent/common; in summer, closely associated
with spawning salmon
Feed on aquatic invertebrates (insect larvae),
terrestrial invertebrates, sockeye salmon eggs, and
salmon carcasses
Eaten by other fishes; eggs eaten by Slimy Sculpin
Arctic Char (H)
(Salvelinus alpinus)
N
Locally common in upland lakes
Feed on aquatic invertebrates (insect larvae, snails,
mollusks) and fishes (Threespine Stickleback,
sculpin)
Eaten by other fishes (Lake Trout, larger Arctic Char)
Dolly Varden (H)
(S. malma)
N and A
Abundant in upland headwaters and selected lakes
Feed on aquatic invertebrates (insect larvae,
zooplankton), terrestrial invertebrates, juvenile
salmon, and salmon eggs
Eaten by larger Dolly Varden, Lake Trout, and
terrestrial predators (River Otters, fish-eating birds)
Lake Trout (H)
(S. namaycush)
N
Common in larger upland lakes and seasonally
present in lake outlets; absent from the Wood River
lakes
Feed on aquatic invertebrates when small and
fishes (Least Cisco, salmon, Arctic Grayling, many
others) when large
Eaten by other fishes (Burbot, large Lake Trout);
eggs eaten by other fish (Slimy Sculpin, Round
Whitefish, other Lake Trout)
Arctic Grayling sH )
(Thymallus arcticus)
N
Abundant/widespread
Feed on aquatic and terrestrial invertebrates and
salmon eggs
Eaten by Lake Trout and Dolly Varden
Lampreys
(Petromyzontidae)
Arctic Lampreyd
(Lethenteron camtschaticum)
A
Juveniles common/widespread in sluggish flows
Feed on detritus and salmon carcasses
Eaten by rainbow trout, other fish, birds, and
mammals
Alaskan Brook Lampreyd
(L alaskense)
N
where fine sediments accumulate
Pacific Lamprey
(Entosphenus tridentatus)
A
Rare
Suckers
(Catostomidae)
Longnose Sucker
(Catostomus catostomus)
N
Common in slower flows of larger streams
Feed on aquatic invertebrates and plants
Eaten by other fish (Lake Trout, Northern Pike,
Burbot) and River Otters
Pikes
(Esocidae)
Northern Pike (H)
(Esoxlucius)
N
Common/widespread in still or sluggish waters
Feed on aquatic invertebrates when small (insect
larvae, zooplankton) and fishes when large (salmon,
Arctic Char, Lake Trout, many others)
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Mudminnows
(Umbridae)
Alaska Blackfish
(Dallia pectoral is)
N
Locally common/abundant in still or sluggish waters
in flat terrain
Feed on aquatic invertebrates (copepods,
cladocerans, insect larvae, snails) and algae
Eaten by Northern Pike and larger Alaska Blackfish
Smelts
(Osmeridae)
Rainbow Smelt
(Osmerus mordax)
A
Seasonally abundant in streams near the coast
Feed on aquatic invertebrates and fishes (Slimy
Sculpin)
Eaten by fish-eating birds, Rainbow Trout, and River
Otters
Pond Smelt
(Hypomesus olidus)
N
Locally common in coastal lakes and rivers, lliamna
Lake, inlet spawning streams, and the upper
Kvichak River; abundance varies widely
interannually
Feed primarily on zooplankton
Eaten by other fishes (Arctic Char, Lake Trout)
Eulachon
(Thaleichthys pacificus)
A
No or few specific reports; if present, distribution
appears limited and abundance low
-
Cods
(Gadidae)
Burbot
(Lota lota)
N
Infrequent to common in deep, sluggish, or still
waters
Feed on aquatic invertebrates when small (insect
larvae) and fishes when large (Least Cisco, Lake
Trout, sculpin, Round Whitefish)
Eaten by other fishes (larger Burbot)
Sticklebacks
(Gasterosteidae)
Threespine Stickleback
(Gasterosteus aculeatus)
N and A
Locally abundant in still or sluggish waters;
abundant in lliamna Lake
Feed on aquatic invertebrates (cladocerans,
copepods, amphipods)
Eaten by other fishes (Arctic Char, Northern Pike,
Rainbow Trout, others), fish-eating birds, and large
aquatic invertebrates (predatory insect larvae)
Ninespine Stickleback
(Pungitius pungitius)
N
Abundant/widespread in still or sluggish waters
Sculpins
(Cottidae)
Coastrange Sculpin
(Cottus aleuticus)
N
Abundant/widespread e
Feed on aquatic invertebrates (insect larvae) and
salmon eggs, alevins, and fry
Eaten by other fishes (salmon fry, Burbot,
Humpback Whitefish, Northern Pike, others)
Slimy Sculpin
(C. cognatus)
N
Notes:
a A = anadromous (fishes that spawn in freshwaters and migrate to marine waters to feed); N = non-anadromous (fishes that spend their entire life in fresh waters, with possible migrations between
habitats within a watershed). N and A indicates fishes in which some individuals have non-anadromous and some have anadromous migratory patterns.
b For anadromous species, only predator-prey relationships in freshwater habitats are presented. Dash (-) indicates either that the species is rare and detailed information is not available for the region, or
that the species spends limited time in fresh water (i.e., for pink and chum salmon).
c In the Bristol Bay watershed, anadromous individuals (steelhead) are known to spawn and rear only in the North Alaska Peninsula watershed.
d Juveniles of these two species, which are the most commonly encountered life stages in these watersheds, are indistinguishable. Both species are present in the watershed, but it is possible that all
documented occurrences are for one of these species.
e These species are combined here, because they are not reliably distinguished in field conditions, although Slimy Sculpin is thought to be more abundant and widely distributed.
Source: EPA 2014, USACE 2020a: Table 3.24-11; see Appendix B, Table 1 in EPA (2014) for references and additional information on the abundance and life history of each species.
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Table 3-4. Life history, habitat characteristics, and total documented stream length occup
Coho
1-3
Headwater streams to
moderate-sized rivers,
headwater springs, beaver
ponds, side channels, sloughs
1+
Headwater streams to moderate
sized rivers
4,470
Sockeye
0-3
Lakes, rivers
2-3
Beaches of lakes, streams
connected to lakes, larger braided
rivers
3,174
Chinook
1+
Headwater streams to large-
sized mainstem rivers
2-4
Moderate-sized streams to large
rivers
3,108
Chum
0
Limited
2-4
Moderate-sized streams and rivers
2,170
Pink
0
Limited
1+
Moderate-sized streams and rivers
1,334
Source: EPA 2014: Appendix A (life history and habitat characteristics), the Anadromous Waters Catalog (Giefer and Graziano 2022) (stream
lengths).
With some exceptions, preferred spawning habitat consists of gravel-bedded stream reaches of
moderate water depth (12 to 24 in [30 to 60 cm]) and current (12 to 40 in/s [30 to 100 cm/s]) (Quinn
2018). In Alaska, studies have also found groundwater exchange to be of key importance for spawning
salmon site selection (MacLean 2003, Curran et al. 2011, Mouw et al. 2014, McCracken 2021).
Both Chum and Pink salmon migrate to the ocean soon after fry emergence (Heard 1991, Salo 1991).
Because Coho, Chinook, and Sockeye salmon spend a year or more rearing in the Bristol Bay watershed's
streams, rivers, and lakes before their ocean migration (Table 3-4), these species depend more on
upstream freshwater resources than do Chum and Pink salmon.
In addition to the five Pacific salmon species, the Bristol Bay region is home to at least 24 resident fish
species, most of which typically (but not always) remain within the watershed's freshwater habitats
throughout their life cycles. The region contains highly productive waters for such subsistence and sport
fish species as Rainbow Trout,38 Dolly Varden, Arctic Char, Arctic Grayling, Humpback Whitefish,
Northern Pike, and Lake Trout, as well as numerous other species that are not typically harvested
(Table 3-3). These fish species occupy a variety of habitats throughout the watershed, including
headwater streams, rivers, off-channel habitats, wetlands, and lakes.
Given the importance of Rainbow Trout, Dolly Varden, and Northern Pike that rely on salmon
populations to both subsistence and sport fisheries (Sections 3.3.6 and 3.3.7), it is worth considering key
life-history and habitat-use traits of these species. The spawning habitat and behavior of Rainbow Trout
are generally similar to those of the Pacific salmon species, with a few key exceptions. First, Rainbow
Trout are iteroparous, meaning that they can spawn repeatedly. Second, spawning occurs in spring,
38 The species O. mykiss includes both a non-anadromous or resident form (commonly referred to as Rainbow
Trout) and an anadromous form (commonly referred to as Steelhead). In the Bristol Bay watershed, Steelhead
generally are restricted to a few spawning streams near Port Moller, on the Alaska Peninsula.
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versus summer and early fall for salmon. Juveniles emerge from spawning gravels in summer (Johnson
et al. 1994, ADF&G 2022a), and immature fishes may remain in their natal streams for several years
before migrating to other freshwater habitats (Russell 1977).
Rainbow Trout in the Bristol Bay watershed exhibit complex migratory patterns, moving between
spawning, rearing, feeding, and overwintering habitats. For example, many adults in the region spawn in
inlet or outlet streams of large lakes, then migrate shortly after spawning to feeding areas within those
lakes. Some mature fishes may seasonally move distances of 120 miles (200 km) or more (Russell 1977,
Burger and Gwartney 1986, Minard et al. 1992, Meka et al. 2003). Often, these migratory patterns
ensure that Rainbow Trout are in close proximity to the eggs and carcasses of spawning salmon, which
provide an abundant, high-quality food resource (Meka et al. 2003). The variety of habitat types used by
Rainbow Trout is reflected by different life-history types identified in the region, including lake, lake-
river, and river residents (Meka et al. 2003).
Dolly Varden is a highly plastic fish species, with multiple genetically, morphologically, and ecologically
distinct forms that can co-exist in the same water bodies (Ostberg et al. 2009). Both anadromous and non-
anadromous Dolly Varden are found in the Bristol Bay watershed, and both life-history forms can exhibit
complex and extensive migratory behavior (Armstrong and Morrow 1980, Reynolds 2000, Scanlon 2000,
Denton et al. 2009, Hart et al. 2015, Chin et al. 2022). Anadromous individuals usually undertake three to
five ocean migrations before reaching sexual maturity (DeCicco 1992, Lisac and Nelle 2000, Crane et al.
2003). During these migrations, Dolly Varden frequently leave one drainage, travel through marine waters,
and enter a different, distant drainage (DeCicco 1992, DeCicco 1997, Lisac 2009). Non-anadromous
individuals also may move extensively between different habitats (Scanlon 2000).
Dolly Varden spawning occurs in fall, upstream of overwintering habitats (DeCicco 1992). Northern-
form anadromous Dolly Varden (the geographic form of Dolly Varden found north of the Alaska
Peninsula) overwinter primarily in lakes and in lower mainstem rivers where sufficient groundwater
provides suitable volumes of free-flowing water (DeCicco 1997, Lisac 2009). Within the Nushagak and
Kvichak River watersheds, juveniles typically rear in low-order, high-gradient stream channels (ADF&G
2022a). Because Dolly Varden occur in headwater lakes and high-gradient headwater streams (ADF&G
2022a)—farther upstream than many other fish species and above migratory barriers to anadromous
salmon populations—they may be especially vulnerable to habitat degradation in these headwater
areas. Like Rainbow Trout, Dolly Varden rely on salmon-derived food resources such as salmon eggs and
carcasses, as well as invertebrates feeding on those carcasses (Denton et al. 2009, Denton et al. 2010,
Jaecks and Quinn 2014).
Northern Pike primarily spawn in sections of lakes, wetlands, or very low-gradient streams that provide
shallow (<3 feet [1 m]), slow, or still waters with aquatic vegetation and soft substrates (EPA 2014:
Appendix B). Their summer habitat is typically deeper, but still relatively warm water with dense
aquatic vegetation. Northern Pike overwinter in lakes, spring-fed rivers, and larger deep rivers where
water and oxygen are sufficient for survival until spring (EPA 2014: Appendix B). In spring, mature
Northern Pike ascend tributaries, beneath the ice, to reach spawning areas, then move to deeper waters
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to feed. Fry remain near or downstream of spawning areas. Many mature Northern Pike do not travel
far, but some river-system individuals make extensive seasonal migrations—sometimes as far as 180
miles (290 km) per year—between spawning, feeding, and overwintering areas (EPA 2014:
Appendix B).
Table 3-3 provides summary information on the other 21 fish species that have been documented in the
Nushagak and Kvichak River watersheds. It is important to note that none of these species exists in
isolation—rather, they together make up diverse fish assemblages that interact with each other in
numerous ways. For example, sculpins, Dolly Varden, and Rainbow Trout consume salmon eggs and
emergent fry (including lamprey ammoceotes), and Northern Pike can be effective predators of juvenile
salmon and other fish species (Sepulveda et al. 2013, Schoen et al. 2022). Insectivorous and
planktivorous fishes may compete with juvenile salmonids for food (e.g., Hartman and Burgner 1972).
These types of prevalent interactions among species mean that impacts on any one fish species could
affect the entire assemblage.
3.3.2 Distribution and Abundance
As Section 3.3.1 illustrates, the Nushagak and Kvichak River watersheds in general—and the SFK, NFK,
and UTC watersheds in particular—support a robust assemblage of fishes, including several species that
support valuable subsistence, commercial, and recreational fisheries (Sections 3.3.5 through 3.3.7).
These fishes use a diversity of freshwater habitats throughout their life cycles. Fish populations across
the Bristol Bay watershed have not been sampled comprehensively, so estimates of total distribution
and abundance across the region are not available. All fish distribution maps included here represent
the currently documented distributions for each species, based on the AWC (Giefer and Graziano 2022)
and the AFFI (ADF&G 2022a). Note that species absence cannot be inferred from these maps, as areas
without documented occurrence of a species may not have been sampled; however, available data39
provide at least minimum estimates of where key species are found and how many individuals of those
species have been caught.40 More information on the distribution and abundance of key fish species can
be found in Section 3.24 of USACE (2020a) and Appendices A and B of the BBA (EPA 2014).
3,3,2,1 Nushagak and Kvichak River Watersheds
Most (72 percent) of the smaller watersheds within the Nushagak and Kvichak River watersheds are
documented to contain at least one species of spawning or rearing salmon within their boundaries;
19 percent are documented to contain all five species (Figure 3-1). Reported distributions for the five
salmon species in the Nushagak and Kvichak River watersheds are shown in Figure 3-2.
39 Notable sources of data include the AWC (Giefer and Graziano 2022), AFFI (ADF&G 2022a), and fish escapement
and harvest data. The AWC is the State of Alaska's official record of anadromous fish distributions and, if available,
the life stages present (categorized as spawning, rearing, or present but life stage unspecified). The AFFI includes
all fish species found at specific sampling points; some observers also documented life stage (adult or juvenile).
40 See Appendix B of this document for additional information on the interpretation of available fish distribution
data.
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Coho Salmon spawn and rear in many stream reaches throughout the Nushagak and Kvichak River
watersheds. Juveniles distribute widely into headwater streams, where they are often the only salmon
species present (Woody and O'Neal 2010, King et al. 2012). Because Coho Salmon spend 1 to 3 years in
fresh water, rearing habitat in headwater streams can be an especially important factor influencing their
productivity (Nickelson et al. 1992, Solazzi et al. 2000).
Chinook Salmon spawn and rear throughout the Nushagak River watershed and in several tributaries of
the Kvichak River. Although Chinook Salmon is the least common salmon species across the Bristol Bay
region, the Nushagak River watershed supports a large Chinook Salmon fishery: on average, more than
75 percent of Bristol Bay's commercial Chinook Salmon catch comes from the Nushagak fishing district
(Section 3.3.5). Chinook Salmon returns to the Nushagak River are consistently greater than 100,000
fish per year and have exceeded 200,000 fish per year in 11 years between 1966 and 2010, which places
the Nushagak River at or near the size of the world's largest Chinook Salmon runs (EPA 2014: Chapter
5). In recent years, Nushagak River Chinook Salmon have failed to meet their established escapement
goal (i.e., the number of adult salmon that "escape" harvest and return to freshwaters to spawn). In
October 2022, ADF&G recommended that Nushagak River Chinook Salmon be designated a stock of
management concern (ADF&G 2022f), highlighting the importance of the species in this region.
Sockeye Salmon is by far the most abundant salmon species in the Bristol Bay watershed (Tiernan et al.
2021).41 Between 2010 and 2019, the average annual inshore run of Sockeye Salmon was 17.9 million
fish in the Naknek-Kvichak district and 12.9 million fish in the Nushagak district (Tiernan et al. 2021).
Tributaries to Iliamna Lake, Lake Clark, and, in the Nushagak River watershed, the Wood-Tikchik Lakes
are major Sockeye Salmon spawning areas, and juveniles rear in each of these lakes. Iliamna Lake
provides the majority of Sockeye Salmon rearing habitat in the Kvichak River watershed and historically
has produced more Sockeye Salmon than any other lake in the Bristol Bay region (Fair et al. 2012).
Riverine Sockeye Salmon populations spawn and rear throughout the Nushagak River watershed.
Chum Salmon is the second most abundant salmon species in the Nushagak and Kvichak River
watersheds. Both Chum and Pink salmon spawn throughout the Nushagak and Kvichak River
watersheds, but do not have extended freshwater rearing stages.
Extensive sampling for Rainbow Trout, Dolly Varden, Arctic Grayling, Northern Pike, and other fishes
has not been conducted throughout the Bristol Bay region, so total distributions and abundances are
unknown. Reported occurrences of a subset of these resident fishes, which provide a minimum estimate
of their extents throughout the Nushagak and Kvichak River watersheds, are shown in Figures 3-3 and
3-4: Rainbow Trout, Dolly Varden, and Arctic Grayling (Figure 3-3) and Northern Pike, stickleback, and
sculpin (Figure 3-4).
41 Bristol Bay is home to the largest Sockeye Salmon fishery in the world, with 46 percent of the average global
abundance of wild Sockeye Salmon between 1956 and 2005 (Ruggerone et al. 2010, EPA 2014: Figure 5-9A).
Between 2010 and 2019, the average annual inshore run of Sockeye Salmon in Bristol Bay was approximately
45.5 million fish (ranging from a low of 24.4 million in 2013 to a high of 63.0 million in 2018) (Tiernan et al. 2021).
Recommended Determination
3-22
December 2022
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Section 3 Importance of the Region's Ecological Resources
Figure 3-1. Diversity of Pacific salmon species production in the Nushagak and Kvichak River
watersheds. Counts of salmon species (Coho, Chinook, Sockeye, Chum, and Pink) spawning and
rearing, based on the Anadromous Waters Catalog (Giefer and Graziano 2022), are summed by
12-digit hydrologic unit codes.
* Approximate Pebble Number of Species
Deposit Location Documented
• Towns and Villages ~ None
South Fork Koktuli, 1
North Fork Koktuli, and j
'• Upper Talarik Creek
Watersheds 3
Nushagak and Kvichak 4
River Watersheds c
Cook Inlet
0 25 50
1 i > i J i i i I
Miles
0 40 80
L J l J I L l l J
Kilometers
Bristol Bay
Recommended Determination
3-23
December 2022
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Section 3
Importance of the Region's Ecological Resources
Figure 3-2. Anadromous fish distribution in the Nushagak and Kvichak River watersheds.
Documented salmon use indicates that at least one Pacific salmon species (Coho, Chinook,
Sockeye, Chum, or Pink) has been documented at the most upstream point in the channel,
based on the Anadromous Waters Catalog (Giefer and Graziano 2022).
Cook Inlet
Bristol Bay
~
Approximate Pebble
South Fork Koktuli,
Deposit Location
Q
North Fork Koktuli, and
Streams and Rivers with
Upper Talarik Creek
Documented Salmon
Watersheds
Use
IMushagak and Kvichak
¦
Lakes with Documented
Salmon Use
River Watersheds
N
i
0
Lj
A
25
i i I i i
50
j_J
Miles
0
Li
O
80
j_J
Kilometers
Recommended Determination
3-24
December 2022
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Section 3
Importance of the Region's Ecological Resources
Figure 3-3. Rainbow Trout, Dolly Varden, and Arctic Grayling occurrence in the Nushagak and
Kvichak River watersheds. Designation of species presence is based on the Alaska Freshwater
Fish inventory (ADF&G 2022a). Note that points shown on land actually occur in smaller streams
not shown on this map.
^KVICHAK
lliamna Lake
Cook Inlet
Bristol Bay
Approximate Pebble
South Fork Koktuii,
Deposit Location
North Fork Koktuii, and
Upper Talarik Creek
Watersheds
0
Arctic Grayling
o
Dolly Varderi
Nushagak and Kvichak
River Watersheds
A
Rainbow Trout
N
A
0
|_!
A
25
1 I 1 ! i
50
j_J
Miles
0
Lj
_ 4^
O
80
i_l
Kilometers
Recommended Determination
3-25
December 2022
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Section 3 Importance of the Region's Ecological Resources
Figure 3-4. Northern Pike, stickleback, and sculpin occurrence in the Nushagak and Kvichak
River watersheds. Designation of species presence is based on the Alaska Freshwater Fish
inventory (ADF&G 2022a). Note that points shown on land actually occur in smaller streams not
shown on this map.
Cook Inlet
Bristol Bay
» Approximate Pebble
Deposit Location
0 Northern Pike
o Stickleback
O Sculpin
South Fork Koktuli,
North Fork Koktuli, and
Upper Talarik Creek
Watersheds
Nushagak and Kvichak
Watersheds
Aiiwr
0 30 60
1 i i i I i i i I
Miles
0 50 100
1 I I l I I l I I
Kilometers
Recommended Determination
3-26
December 2022
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Section 3
Importance of the Region's Ecological Resources
3,3,2,2 South Fork Koktuli River, North Fork Koktuii River, and Upper Taiarik Creek
Watersheds
This section highlights the abundance and diversity of fish resources found in the SFK, NFK, and UTC
watersheds, particularly in terms of Pacific salmon. The important relationship between the region's
aquatic habitats and its fish populations—and the resulting ecological value of this relationship—is
discussed in greater detail in Section 3.3.3.
Summer fish distributions in the SFK, NFK, and UTC watersheds have been sampled over several years
(PLP 2011: Chapter 15, PLP 2018a: Chapter 15). The catalogued distributions of the five Pacific salmon
species (Coho, Chinook, Sockeye, Chum, and Pink), resident Rainbow Trout, Dolly Varden (both
anadromous and non-anadromous forms are present), and Arctic Grayling in these watersheds are
shown in Figures 3-5 through 3-10. In addition, Arctic-Alaskan Brook Lamprey, Northern Pike,
Humpback Whitefish, Least Cisco, Round Whitefish, Burbot, Threespine Stickleback, Ninespine
Stickleback, and Slimy Sculpin occur in these watersheds (Table 3-5) (ADF&G 2022a). Summary
information about these species is provided in Table 3-3; more detailed information on distributions,
abundances, habitats, life cycles, predator-prey relationships, and harvests is provided in Appendix B of
EPA (2014) and Section 3.6 of USACE (2020a).
Table 3-5. Documented fish species occurrence in the South Fork Koktuli River. North Fork Koktuli
River, and Upper Taiarik Creek watersheds.
Humpback Whitefish
2
Least Cisco
3
Round Whitefish
3
Coho Salmon
525
Chinook Salmon
183
Sockeye Salmon
102
Chum Salmon
7
RainbowTrout
110
Dolly Varden c
682
Arctic Grayling
199
Arctic-Alaskan Brook Lamprey0
4
Northern Pike
74
Burbot
2
Threespine Stickleback
32
Ninespine Stickleback
67
Unspecified stickleback species
27
Slimy Sculpin
533
Unspecified sculpin species
226
Notes:
a This is not a complete list of species found in the South Fork Koktuli River, North Fork Koktuli River, and Upper Taiarik Creek watersheds,
because it is based only on the Alaska Freshwater Fish Inventory (ADF&G 2022a); for example, Pink Salmon are only listed in the Anadromous
Waters Catalog (Giefer and Graziano 2022).
b Number of unique sample sites for each species (i.e., number of sample sites where at least one life stage was found).
c Juveniles of these two species, which are the most commonly encountered life stages in these watersheds, are indistinguishable. Both species
are present in the watersheds, but it is possible that all documented occurrences are for one of these species.
Source: Alaska Freshwater Fish Inventory (ADF&G 2022a).
Recommended Determination
3-27
December 2022
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Section 3
Importance of the Region's Ecological Resources
Of the 667 stream miles (1,073 km) that have been mapped in the SFK, NFK, and UTC watersheds,
201 miles (323 km) or 30 percent have been documented to contain anadromous fishes (Table 3-6; see
Appendix B for discussion of why this likely represents a significant underestimation of actual
anadromous waters). Coho Salmon have the most widespread distribution of the five salmon species in
the three watersheds and make extensive use of mainstem and tributary habitats, including headwater
streams (Figure 3-5). Chinook and Sockeye salmon have been documented throughout mainstem
reaches of the three watersheds, as well as several tributaries (Figures 3-6 and 3-7). The distributions of
Chum and Pink salmon are generally restricted to mainstem reaches where spawning and migration
have been documented. Chum Salmon have been found in all three watersheds, whereas Pink Salmon, at
very low numbers, have been reported only in the lowest section of UTC and in the Koktuli River below
the confluence of the SFK and NFK (Figures 3-8 and 3-9). Rainbow Trout have been collected at many
mainstem and several tributary locations, especially in UTC (Figure 3-10). Dolly Varden are found
throughout the three watersheds, with fish surveys indicating that they are commonly found in the
smallest streams (i.e., first-order tributaries) (Figure 3-10). Arctic Grayling are also found throughout
the three watersheds, particularly in the SFK headwaters (Figure 3-10).
Table 3-6. Total documented anadromous fish stream length and stream length documented t
contain different salmonid species in the South Fork Koktuli River, North Fork Koktuli River, a
Upper Talarik Creek watersheds.
Total mapped streams •
194
209
264
667
Total anadromous fish streams '
60
65
76
201
By species
Chinook Salmon
38
43
39
120
Chum Salmon
23
20
28
71
Coho Salmon
59
64
76
199
PinkSalmon
0
0
4
4
Sockeye Salmon
40
29
49
119
Notes:
a From the National Hydrography Dataset (USGS 2021b).
b From the Anadromous Waters Catalog (Giefer and Graziano 2022).
Recommended Determination 2 2g December 2022
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Section 3
Importance of the Region's Ecological Resources
Figure 3-5. Reported Coho Salmon distribution in the South Fork Koktuli River, North Fork
Koktuli River, and Upper Talarik Creek watersheds. "Present" indicates the species was present
but life-stage use was not determined; "spawning" indicates spawning adults were observed; and
"rearing" indicates juveniles were observed. Present, spawning, and rearing designations are
based on the Anadromous Waters Catalog (Giefer and Graziano 2022).
NUSHAGAK
Upper TalarikCreek
South Fork Koktuli
KVICHAK
Present
Spawning
Rearing
~
Pebbie Deposit
~
South Fork Koktuli,
North Fork Koktuli, and
Upper Talarik Creek
Watersheds
ca
Nushagakand Kvichak
Watersheds
lliamna Lake
N
A
0
|_l
A
3
i i i i
6
U
Miles
0
Lj
5
i i 1 ii
10
l_l
Kilometers
Recommended Determination
3-29
December 2022
-------
Section 3
Importance of the Region s Ecological Resources
Figure 3-6. Reported Chinook Salmon distribution in the South Fork Koktuli River, North Fork
Koktuli River, and Upper Talarik Creek watersheds. "Present" indicates the species was present
but life-stage use was not determined; "spawning" indicates spawning adults were observed; and
"rearing" indicates juveniles were observed. Present, spawning, and rearing designations are
based on the Anadromous Waters Catalog (Giefer and Graziano 2022).
Upper Talarik Creek
South Fork Koktuli
N
A
0 3
6
1 i i i 1 i i
Miles
J 1
0 5
10
1 i i i 1 i i
Kilometers
I 1
Present
Spawning
Rearing
I I Pebble Deposit
South Fork Koktuli,
North Fork Koktuli, and
Upper Talarik Creek
Watersheds
Nushagak and Kvichak
Watersheds
lliamna Lake
NUSHAGAK
KVICHAK
Recommended Determination
3-30
December 2022
-------
Section 3 Importance of the Region's Ecological Resources
Figure 3-7. Reported Sockeye Salmon distribution in the South Fork Koktuli River, North Fork
Koktuli River, and Upper Talarik Creek watersheds. "Present" indicates the species was present
but life-stage use was not determined; "spawning" indicates spawning adults were observed; and
"rearing" indicates juveniles were observed. Present, spawning, and rearing designations are
based on the Anadromous Waters Catalog (Giefer and Graziano 2022).
North Fork Koktuli
Upper Talarik Creek
South Fork Koktuli
NUSHAGAK
KVICHAK
Present
Spawning
Rearing
Pebble Deposit
South Fork Koktuli,
North Fork Koktuli, and
Upper Talarik Creek
Watersheds
Nushagak and Kvichak
Watersheds
lliamna Lake
Miles
0 5 10
1 1 1 I I ! 1 I i
Kilometers
Recommended Determination
3-31
December 2022
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Section 3 Importance of the Region's Ecological Resources
Figure 3-8. Reported Chum Salmon distribution in the South Fork Koktuli River, North Fork
Koktuli River, and Upper Talarik Creek watersheds. "Present" indicates the species was present
but life-stage use was not determined; "spawning" indicates spawning adults were observed; and
"rearing" indicates juveniles were observed. Present, spawning, and rearing designations are
based on the Anadromous Waters Catalog (Giefer and Graziano 2022).
North Fork Koktuli
Upper Talarik Creek
South Fork Koktuli
NUSHAGAK
KVICHAK
Present
Spawning
Rearing
Pebble Deposit
South Fork Koktuli,
North Fork Koktuli, and
Upper Talarik Creek
Watersheds
Nushagak and Kvichak
Watersheds
lliamna Lake
A
0 3 6
Ll—I I I l_i_l_J
Miles
0 5 10
1 i i i I _L-1—l_l
Kilometers
Recommended Determination
3-32
December 2022
-------
Section 3 Importance of the Region's Ecological Resources
Figure 3-9. Reported Pink Salmon distribution in the South Fork Koktuli River, North Fork
Koktuli River, and Upper Talarik Creek watersheds. "Present" indicates the species was present
but life-stage use was not determined; "spawning" indicates spawning adults were observed; and
"rearing" indicates juveniles were observed. Present, spawning, and rearing designations are
based on the Anadromous Waters Catalog (Giefer and Graziano 2022).
Upper Talarik Creek
South Fork Koktuli
River
NUSHAGAK \North Fork Koktuli
\ -m. MM .
KVICHAK
Present
Spawning
Rearing
Pebble Deposit
South Fork Koktuli,
North Fork Koktuli, and
Upper Talarik Creek
Watersheds
Nushagak and Kvichak
Watersheds
lliamna Lake
N
A
0 3 6
1 i > ) : > i i i
Miles
0 5 10
Kilometers
Recommended Determination
3-33
December 2022
-------
Section 3
Importance of the Region's Ecological Resources
Figure 3-10. Rainbow Trout, Doliy Varden, and Arctic Grayling occurrence in the South Fork
Koktuli River, North Fork Koktuli River, and Upper Taiarik Creek watersheds. Designation of
species presence is based on the Alaska Freshwater Fish Inventory (ADF&G 2022a).
0 Arctic Grayling
O Dolly Varden
A Rainbow Trout
Pebble Deposit
South Fork Koktuli,
r North Fork Koktuli, and
Upper Taiarik Creek
Watersheds
Nushagakand Kvichak
River Watersheds
NUSHAGAK
KVICHAK
lliamna Lake
Recommended Determination
3-34
December 2022
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Section 3
Importance of the Region's Ecological Resources
Index estimates of relative spawning salmon abundance in the SFK, NFK, and UTC watersheds are
available for Sockeye, Coho, Chinook, and Chum salmon. Both ADF&G and PLP have conducted aerial
index counts of spawning salmon at different points in time. This type of survey is used primarily to
track variation in run size over time. Survey values tend to underestimate true abundance: for example,
USACE (2020a: Section 3.24) states that aerial surveys capture only an average of 18 percent of total
abundance. This underestimation occurs for several reasons. An observer in an aircraft is not able to
count all fishes in dense aggregations or those concealed under overhanging vegetation or undercut
banks, and only a fraction of the fishes that spawn at a given site are present at any one time (Bue et al.
1998, Jones et al. 2007). Weather, water clarity, and other factors that influence fish visibility can also
contribute to underestimates. In addition, surveys intended to capture peak abundance may not always
do so. For example, aerial surveys counted, on average, only 44 percent of the Pink Salmon counted by
surveyors walking the same Prince William Sound spawning streams (Bue et al. 1998). Peak aerial
counts of Pink Salmon in southeastern Alaska are routinely multiplied by 2.5 to represent more
accurately the number of fishes present at the survey time (Jones et al. 2007). Helicopter surveys of
Chinook Salmon on the Kenai Peninsula's Anchor River over 5 years counted only 5 to 10 percent of the
fishes documented by a concurrent sonar/weir counting station (Szarzi et al. 2007).
ADF&G conducts aerial index counts that target peak Sockeye Salmon spawning periods on UTC and
peak Chinook Salmon spawning periods on the Koktuli River system. Sockeye Salmon counts have been
conducted in most years since 1955 (Morstad 2003), and Chinook Salmon counts in most years since
1967 (Dye and Schwanke 2009). Between 1955 and 2011, Sockeye Salmon counts in UTC ranged from 0
to 70,600, with an average of 7,021 over 49 count periods (Morstad pers. comm.). Between 1967 and
2009, Chinook Salmon counts in the Koktuli River system ranged from 240 to 10,620, with an average of
3,828 over 29 count periods (Dye and Schwanke 2009). The mean aerial count of Chinook Salmon in the
Koktuli River represents nearly one-quarter of the mean total for the entire Nushagak-Mulchatna
watershed (Dye and Schwanke 2009). Thus, the Nushagak River is the largest producer of Chinook
Salmon in the Bristol Bay watershed, and the Koktuli River is the largest producer of Chinook Salmon in
the Nushagak River watershed.
PLP (2018a) provides aerial index counts for Chinook, Chum, Coho, and Sockeye salmon adults in the
SFK, NFK, and UTC mainstem segments and select tributaries from 2004 to 2008. Surveys on the SFK
and NFK began at their confluence and extended upward to the intermittent reach or Frying Pan Lake on
the SFK and upward to Big Wiggly Lake or river kilometer 56 on the NFK. Surveys on UTC ran from the
mouth and extended upstream to Tributary 1.350 (just east of Koktuli Mountain) or to the headwaters.
Multiple counts were usually made for each stream and species in a given year.
Table 3-7 reports the minimum and maximum values for highest index spawner count in the SFK, NFK,
and UTC mainstems, from 2004 through 2008 (SFK and NFK) or 2009 (UTC) (PLP 2018a: Chapter 15,
Tables 15-14 through 15-17). Peak index counts capture only a portion of total spawning run
abundance, because only a portion of the spawning population is present on the spawning grounds on
any given day. Individual spawners are visible on their spawning grounds for days to weeks (e.g., Bue et
al. 1998), but the spawning season can extend for weeks to months in the SFK, NFK, and UTC watersheds
Recommended Determination
3-35
December 2022
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Section 3 Importance of the Region's Ecological Resources
(PLP 2018a). The highest peak index counts for Coho and Sockeye salmon were in UTC, whereas the
highest counts for Chinook and Chum salmon were in the SFK and NFK (Table 3-7). The overall highest
count was for Sockeye Salmon in UTC in 2008, when approximately 50,317 fish were estimated
(Table 3-7).
South Fork Koktuli
River
2004-2008
Chinook
3-9
327 (2006)
2,780 (2004)
Chum b
4-11
189 (2007)
917 (2008)
Coho
2-21
270 (2004)
1,955 (2008)
Sockeye
3-14
1,730 (2004)
6,133 (2008)
North Fork Koktuli
River
2004-2008
Chinook
3-8
434 (2008)
2,889 (2005)
Chum
1-9
350 (2005)
1,432 (2008)
Coho
1-17
114 (2007)
1,704 (2008)
Sockeye
2-11
563 (2004)
2,188 (2007)
Upper Talarik Creek
2004-2009
Chinook
2-9
80 (2009)
272 (2004)
Chum b
1-8
3 (2005)
44 (2008)
Coho
2-21
1,041 (2005)
7,542 (2009)
Sockeye
2-20
10,557 (2007)
50,317 (2008)
Notes:
a Values likely underestimate true spawner abundance (see Appendix B of this document for additional information).
b Chum were not counted in the North Fork Koktuli or Upper Talarik Creek in 2004.
Source: PLP 2018a: Chapter 15, Tables 15-14 through 15-17.
Aerial counts of adult salmon were also conducted in tributaries of the SFK, NFK, and UTC between 2004
and 2009 (Table 3-8). Adult Coho and Chum salmon were counted in SFK tributaries; adult Coho and
Sockeye salmon were counted in NFK tributaries; and adult Coho, Chinook, Chum, and Sockeye salmon
were counted in UTC tributaries. The highest number of adults reported in tributaries of each watershed
were 50 Coho Salmon (SFK 1.190), 111 Sockeye Salmon (NFK 1.240), and 31,922 Sockeye Salmon
(UTC 1.160) (Table 3-8).
Recommended Determination
3-36
December 2022
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Section 3
Importance of the Region's Ecological Resources
Table 3-8. Highest reported number of adult salmon in tributaries of the South Fork Koktuli River,
SFK 1.130
2004-2008
26 (0-24)
Chum
6
South Fork Koktuli
River
Coho
48
SFK 1.190
2004-2008
42 (0-24)
Chum
28
Coho
50
SFK 1.240
2004-2008
26 (0-14)
Coho
5
NFK 1.190 c
2004-2008
39 (0-21)
Coho
27
NFK 1.240 c
2004-2008
26 (1-17)
Coho
12
North Fork Koktuli
Sockeye
111
River
NFK 1.260
2004-2008
11 (0-10)
Coho
4
NFK 1.270
2004-2008
6 (0-5)
Coho
23
NFK 1.280
2006-2008
2 (0-1)
Coho
2
UTC 1.160
2008-2009
42 (18-24)
Coho
1,079
Sockeye
31,922
UTC 1.190
2004-2009
53 (0-22)
Sockeye
49
Chum
3
UTC 1.350 c
2004-2009
52 (1-25)
Coho
571
Sockeye
57
Upper Talarik Creek
UTC 1.390 c
2007-2009
(1-27)
Coho
29
Sockeye
115
UTC 1.410
2004-2009
34 (0-19)
Chinook
2
Chum
21
Coho
43
Sockeye
30
UTC 1.460
2004-2005
3(1-2)
Coho
7
Notes:
a In all but one case, the maximum number of surveys occurred in 2008.
b Only tributaries and salmon species with at least one survey count greater than one are listed.
c NFK 1.190 also includes NFK 1.190.10; NFK 1.240 also includes NFK 1.240P1,1.240P1 Big Wiggly Lake, and 1.240.20.P1; UTC 1.350 also
includes 1.350.20,1.350.20P1,1.350.20P2, and 1.350.20P3; UTC 1.390 also includes 1.390.20P2.
Source: PLP 2018a: Chapter 15, Appendix 15B2.
Mainstem and off-channel habitats of the SFK, NFK, and UTC also provide abundant habitat for juvenile
salmonids. Table 3-9 presents maximum estimated densities and total numbers observed for juvenile
Pacific salmon species in mainstem SFK, NFK, and UTC reaches (PLP 2018a: Chapter 15, USACE 2020a).
Reported fish densities summarized over the 5-year period vary widely by stream and reach, which is
typical for fishes in heterogeneous stream environments. The highest maximum estimated density for
juvenile salmon was approximately 124 juvenile Coho Salmon in UTC Reach F (Table 3-9). Habitat-
specific densities were much higher, however: for example, a density of approximately 1,600 Coho
Salmon (of which roughly 90 percent were juveniles) per 100 m2 of pool habitat was estimated in UTC
Reach D (PLP 2011: Figure 15.1-82).
Recommended Determination
3-37
December 2022
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Section 3
Importance of the Region's Ecological Resources
Table 3-9. Maximum estimated densities and total observed number of juvenile Pacific salmo
I
South Fork Koktuli River
SFK-A (0.0-24.9)
24.86
37.40
1.77
1,246
762
29
SFK-B (24.9-34.3)
0.21
20.21
0.57
4
292
8
SFK-C (34.3-51.7)
0.12
19.77
0.35
4
101
-
SFK-D (51.7-54.7)
1.39
2.52
0.00
-
-
-
SFK-E (54.7-64.2)
0.00
1.18
0.00
-
1
-
North Fork Koktuli River
NFK-A (0.0-13.7)
18.84
17.67
0.15
802
415
7
NFK-B (13.7-21.1)
30.68
34.52
1.18
95
190
-
NFK-C (21.1-36.6)
8.24
28.07
1.89
213
624
42
NFK-D (36.6-48.4)
0.38
2.73
0.12
-
23
1
NFK-E (48.4-52.5)
0.00
0.00
0.00
-
-
-
Upper Talarik Creek
UTC-A (0.0-5.9)
0.38
1.25
0.00
10
33
-
UTC-B (5.9-16.8)
17.62
46.24
0.14
61
931
-
UTC-C (16.8-24.8)
11.31
67.24
2.28
101
422
1
UTC-D (24.8-36.3)
4.64
48.99
0.29
6
868
-
UTC-E (36.3-45.1)
4.77
115.42
4.12
5
1,240
5
UTC-F (45.1-59.1)
1.53
123.78
0.67
-
992
1
UTC-G (59.1-62.4)
0.00
21.53
0.00
-
2
-
Notes:
a Maximum estimated juvenile density across values reported for 2004-2007, 2008, and 2009.
b Total number of juveniles observed across index sites within given reach in 2009, surveyed by beach seine and snorkel methods. South Fork
Koktuli River sites were sampled 7/24 to 8/28; North Fork Koktuli River sites were sampled 7/25 to 8/21; Upper Talarik Creek sites were
sampled 7/26 to 8/28. Dash (-) indicates that no counts for the given species were reported within that reach.
Source: USACE 2020a: Table 3.24-9, PLP 2018a: Chapter 15, Table 15-11.
Abundant and diverse off-channel habitats are also found in the SFK, NFK, and UTC watersheds (Section
3.2.2). Aerial imagery shows that roughly 70 percent of the mainstem SFK and UTC and roughly 90
percent of the mainstem NFK are bordered by some form of off-channel habitat (USACE 2020a: Section
3.24), most commonly beaver complexes (Section 3.2.2) (USACE 2020a: Section 3.24). Off-channel
habitats provide important rearing habitat for many fish species but may be especially important as
rearing and overwintering habitats for juvenile salmonids (Huntsman and Falke 2019, USACE 2020a:
Section 3.24). Table 3-10 highlights the diversity of both off-channel habitats and the fish species that
rely on them in the SFK, NFK, and UTC watersheds. Relative abundance in these habitats is highest for
Coho Salmon, with an estimate of more than 1,300 fish per 100 meters.
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Section 3
Table 3-10. Relative abundance of sa
Alcove
South Fork Koktuli
River3
Beaver pond
36
2.94
30.38
10.84
7.37
4.29
0
Beaver pond outlet
channel
-
-
-
-
-
-
-
Isolated pool
2
0
8.22
2.35
0
0
0
Percolation
channel
2
0
11.43
0
0
0
0
Side channel
3
10.34
66.41
5.17
0.52
0
0.52
North Fork Koktuli
Riverb
Alcove
1
2.06
1,334.02
24.74
0
12.37
0
Beaver pond
9
0.18
78.19
0.53
0
1.07
0
Beaver pond outlet
channel
1
0
0
0
0
0
0
Isolated pool
2
0
0
0
0
0
0
Percolation
channel
16
2.49
51.60
0.62
0
8.70
0
Side channel
8
0
568.13
0
0
69.21
0
Upper Talarik Creekc
Alcove
1
0
87.10
0
0
0
0
Beaver pond
24
1.38
317.41
0.42
0.26
1.38
0.42
Beaver pond outlet
channel
3
0
42.38
0
0
1.32
1.32
Isolated pool
4
0
15.09
0
0
0
0
Percolation
channel
10
0.63
144.38
3.92
12.54
0.16
0.78
Side channel
3
0.75
270.33
1.51
0
0.75
0
Notes:
a Off-channel sites in the South Fork Koktuli River were sampled in September 2005, June and August 2006, and July 2007; it is not clear if or
how data from sampling dates were combined to arrive at table values.
b Off-channel sites in the North Fork Koktuli River were sampled between late July to mid-August 2008; it is not clear if or how data from sampling
dates were combined to arrive at table values.
c Off-channel sites in Upper Talarik Creek were sampled in July and October 2007; it is not clear how data from these sampling dates were
combined to arrive at table values.
Source: PLP 2011: Chapter 15, Appendix 15.1D, Table 6.
As Table 3-3 illustrates, the SFK, NFK, and UTC watersheds are home to several fish species in addition
to Pacific salmon. Maximum estimated densities for a subset of these other fishes in the SFK, NFK, and
UTC mainstem reaches are shown in Table 3-11. Estimated densities are highest for Artie Grayling,
particularly in upstream reaches of all three watersheds.
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Importance of the Region's Ecological Resources
Watershed/Reach
(River Kilometers)
South Fork Koktuli River
Rainbow
Trout
Dolly warden
Maximum Estimated Density (# p
| ___ |
Grayling
Northern Pike
Sculpin spp.
Sticklel
spp
SFK-A (0.0-24.9)
0.03
3.44
0.67
0.00
2.52
0.00
SFK-B (24.9-34.3)
0.29
0.64
2.47
0.00
1.29
0.00
SFK-C (34.3-51.7)
0.00
0.82
35.31
0.47
4.94
0.21
SFK-D (51.7-54.7)
0.00
5.55
45.02
1.26
19.78
0.00
SFK-E (54.7-64.2)
0.00
0.00
15.90
2.36
9.29
0.15
North Fork Koktuli River
NFK-A (0.0-13.7)
0.23
0.74
2.44
0.00
1.52
0.00
NFK-B (13.7-21.1)
0.00
0.24
0.21
0.00
2.01
0.00
NFK-C (21.1-36.6)
0.00
1.76
6.68
0.00
1.76
0.00
NFK-D (36.6-48.4)b
0.00
1.05
6.01
0.10
6.77
0.19
NFK-E (48.4-52.5)b
0.00
0.00
0.00
0.00
10.00
0.00
Upper Talarik Creek
UTC-A (0.0-5.9)b
0.11
0.00
0.04
0.00
0.66
14.55
UTC-B (5.9-16.8)b
10.64
0.20
0.61
0.00
1.96
0.00
UTC-C (16.8-24.8)
11.03
0.47
32.10
0.00
13.31
0.54
UTC-D (24.8-36.3)
0.45
1.22
1.19
0.00
3.70
0.44
UTC-E (36.3-45.1)
0.32
0.44
0.70
0.00
7.53
0.04
UTC-F (45.1-59.1)
0.87
3.35
0.43
0.00
28.65
0.17
UTC-G (59.1-62.4)
0.00
7.46
0.00
0.00
16.58
0.00
Notes:
a Maximum estimated adult and juvenile density across values reported for 2004-2007, 2008, and 2009.
b Reach was not sampled from 2004-2007.
Source: USACE 2020a: Table 3.24-9.
3.3.3 Habitat Complexity, Biocomplexity. and the Portfolio Effect
The world-class salmon fisheries in Bristol Bay result from numerous, interrelated factors. Closely tied
to the Bristol Bay region's physical habitat complexity (Section 3.2) is its biocomplexity, which greatly
increases the region's ecological productivity and stability. This biocomplexity operates at multiple
scales and across multiple species, but it is especially evident in the watershed's Pacific salmon
populations (Shedd et al. 2016). As a result, the loss of even a small, discrete population within the
Bristol Bay watershed's overall salmon populations may have more significant effects than expected,
due to associated decreases in biocomplexity.
3.3.3.1 The Relationship between Habitat Complexity and Biocomplexity
The five Pacific salmon species found in the Bristol Bay watershed vary in life-history characteristics
(Table 3-4). Even within a single species, life histories can vary significantly. For example, Sockeye
Salmon may spend anywhere from 0 to 3 years rearing in freshwater habitats, then 2 to 3 years feeding
at sea, before returning to the Bristol Bay watershed anytime within a 4-month window (Table 3-4).
Coho Salmon similarly may spend anywhere from 1 to 3 years rearing in freshwater habitats
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Section 3
Importance of the Region's Ecological Resources
(Table 3-4). This staggered and overlapping age structure reduces variation in recruitment because it
reduces the probability that all individuals in a cohort of siblings will encounter unfavorable
environmental conditions over the course of their life cycles.
Pacific salmon exhibit homing behavior, meaning that they return to their natal streams to spawn. This
homing behavior reduces gene flow between breeding groups and allows natural selection and genetic
drift to produce discrete populations within each species that are adapted to their own specific
spawning and rearing habitats and are distinguishable using various genetic tools (Hilborn et al. 2003,
Ramstad et al. 2010, Schindler et al. 2010, Larson et al. 2019). As research tools have improved, it is
increasingly clear that population differentiation can occur at very fine spatial scales (Quinn et al. 2012),
enabled by the remarkable homing abilities of Pacific salmon species (Quinn et al. 2006) and driven by
differences in environmental characteristics such as thermal regime and water chemistry (Ruff et al.
2011, Keefer and Caudill 2014).
Both geography and ecology influence this genetic divergence within salmon species (Gomez-Uchida et
al. 2011). Spawning populations return at different times and to different locations, creating and
maintaining a degree of reproductive isolation due to reduced genetic exchange and allowing
development of genetically distinct populations (Varnavskaya et al. 1994, Hilborn et al. 2003, McGlauflin
et al. 2011). Within discrete spawning areas, natural selection may favor traits differently based on the
unique environmental characteristics of spawning or rearing areas. For example, phenotypic variation in
Sockeye Salmon body size and shape in the Bristol Bay region has been related to gravel size and
spawning habitat (Quinn et al. 1995, Quinn et al. 2001, Larson et al. 2017, Schindler et al. 2018),
illustrating the apparent adaptive significance of this variation.
These life history characteristics allow Pacific salmon species to fully exploit the range of habitats
available throughout the Bristol Bay watershed, where many populations of each of these species are
arrayed across a diverse landscape. Hydrologically diverse riverine and wetland landscapes across the
region provide a variety of large river, small stream, floodplain, pond, and lake habitats for salmon
spawning and rearing. Environmental conditions can differ among habitats in close proximity, and
variations in temperature and streamflow associated with seasonality and groundwater-surface water
interactions create a habitat mosaic that supports a range of spawning times across the watersheds
(Lisi et al. 2013, Schindler et al. 2018).
Bristol Bay is home to the largest Sockeye Salmon fishery in the world (Section 3.3.5). Sockeye Salmon
from Bristol Bay produce relatively consistent returns due to the high degree of population diversity
found within both the species and the region (Hilborn et al. 2003, Wood et al. 2008, Schindler et al. 2010,
Schindler et al. 2015, Moore et al. 2021). A major component of this population diversity is associated
with the diversity of habitats used for spawning, which has resulted in the formation of distinct
spawning ecotypes (Figure 3-11) (Quinn et al. 1995, Lin et al. 2008a, Dann et al. 2012, Larson et al. 2017,
Schindler et al. 2018).
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Importance of the Region s Ecological Resources
Figure 3-11. Bristol Bay salmon genetic lines of divergence linked to ecotypes. Genotypic and
phenotypic diversity are linked in Sockeye Salmon from the Wood River system in Bristol Bay,
providing an example of phenotypic variation due to selective adaptive pressures from the diversity
of habitats (beaches, rivers, and streams) across the landscape. From Larson et al. (2017); reprinted
with permission.
(a)
N
A
Lake NerKa
• , ®Anvil Beach
Little Togiak River
uxe Nerfca 0
Teal Creek
® Agubwak River
Lake Ateknaglk
® Hansen Creek
®Yako Beach
Pacific Ocean •
0 5 10 km
1 i i
r
159 WW 15r4Q'Q"W
(b)
For both Chinook and Sockeye salmon, biocomplexity—operating across a continuum of integrated,
nested spatial and temporal scales—stabilizes salmon production and fisheries in the Nushagak River
watershed (Brennan et al. 2019], Productivity of Sockeye and Chinook salmon shifts within the
Nushagak River watershed from year to year (Figure 3-12). Because the productivity of individual
habitats and sub-watersheds in the Nushagak River watershed varies with environmental conditions,
maintaining habitat diversity across the landscape is critical for maintaining the sustainability and
productivity of the watershed's salmon populations. The phenotypic, genotypic, and behavioral diversity
of these salmon populations depends on the diversity of aquatic habitats in space and time (Davis et al.
2017, Schindler et al. 2018, Brennan et al. 2019).
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Importance of the Region s Ecological Resources
Figure 3-12. Productive habitats for Chinook and Sockeye salmon across the Nushagak River
watershed shift over time. From Brennan et al. (2019); reprinted with permission.
Nushagak
Upper WT;
Tikchik
Lakes
Mulchatna
Relative
Production
Lower
River
Bering
Sea
Nushagak River
Bristol
Bay
Gulf of Alaska
Alaska, U.S.A.
[0,0.1)
[0.1,0.2)
[0.2,0.3)
[0.3,0.4)
[0.4,0.5)
[0.5,0.6)
[0.6,0.7)
[0.7,0.8)
[0.8,0.9)
[0.9,1]
100 Km
2014
Although this genetic differentiation and associated phenotypic differences tend to increase with
distance between the populations, even populations in relatively close proximity can exhibit high
degrees of differentiation (May et al. 2020). As a result, these discrete populations can occur at localized
spatial scales. For example, Sockeye Salmon that use spring-fed ponds and streams approximately 1 km
apart exhibit differences in spawn timing, productivity, and other traits that are consistent with discrete
populations (Quinn et al. 2012). Multiple beach-spawning populations of Sockeye Salmon are found in
Iliamna Lake (Figures 3-11 and 3-13) (Stewart et al. 2003, Larson et al. 2017). Genetically distinct river-
type and lake-type populations can co-occur within watersheds (Dann et al. 2013, Shedd et al. 2016,
Larson et al. 2017), and inlet and outlet spawners with distinct migration patterns can occur within the
same lake (Burger et al. 1997). Iliamna Lake supports genetically unique populations within tributary,
island, and lake shoreline ecotones, with UTC identified as the location of one of the 22 populations
(Figure 3-13). Genetic diversity of Sockeye Salmon in Bristol Bay has been found to be distributed
hierarchically between ecotypes, among drainages within ecotypes, and among populations within
drainages (Figure 3-11) (Dann et al. 2013, Larson et al. 2017, Schindler et al. 2018, Larson et al. 2019).
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Section 3
Importance of the Region s Ecological Resources
Figure 3-13. Kvichak River Sockeye Salmon populations. 22 populations of Sockeye Salmon (color-
coded by reporting group) have been identified in the Kvichak River. From Dann et al. (2018);
reprinted with permission.
Reporting Group
> Lake Clark
* Northeast Iliamna
Iliamna Islands
Iliamna Tributaries
-------
Section 3
Importance of the Region's Ecological Resources
Sockeye Salmon that spawn in small streams tend to be smaller than beach or river spawners, as
shallow stream depths and size-selective predation by bears favor survival of smaller spawning adults
(Figure 3-11) (Quinn et al. 2001, Larson et al. 2017). These different spawning environments also vary
in other characteristics, such as temperature, gravel size, and spawning density, resulting in differences
in egg size (Quinn et al. 1995, Hendry et al. 2000), timing of spawning (Schindler et al. 2010) and
pathogen susceptibility (hypothesized in Larson et al. 2014). Local adaptation to these diverse habitats
is key to creating and preserving salmon genetic diversity.
The river-type form of Sockeye Salmon, with juveniles that rear in rivers and tributaries for one or more
years before migrating to the ocean, is relatively rare in Bristol Bay; the lake-type form, with juveniles
that rear in lakes for one or more years before migrating, is more common (Wood et al. 2008). However,
river-type Sockeye Salmon are found in the Nushagak River watershed, including in the Koktuli River
(Dann et al. 2012). River-type Sockeye Salmon represent an important form of genetic diversity, as these
populations typically exhibit greater diversity within and less diversity among populations than the
more abundant lake-type sockeye salmon (Larson et al. 2019). It has been hypothesized that river-type
Sockeye Salmon have a greater tendency than lake-type Sockeye Salmon to stray from natal areas and,
thus, may be the colonizers of the species (Wood 1995, Wood et al. 2008). In this manner, life history
and genetic diversity can help "seed" new freshwater habitats that become available (e.g., as glaciers
recede due to climate change [Pitman et al. 2020]).
3,3,3,2 The Portfolio Effect
The life-history complexity of Bristol Bay's Pacific salmon species is superimposed on localized
adaptations, resulting in a high degree of biocomplexity organized into discrete, locally distinct fish
populations. For example, the Bristol Bay watershed includes a complex of different Sockeye Salmon
populations—that is, a combination of hundreds of genetically distinct, wild populations, each adapted
to specific, localized environmental conditions (Hilborn et al. 2003, Schindler et al. 2010, Schindler et al.
2018). As genetic tools and techniques develop, the science continues to advance our understanding of
the prevalence and importance of individual populations.
Management of Alaska's salmon fisheries is geared toward protection of these wild salmon populations,
or stocks (5 AAC 39.222, 5 AAC 39.220, 5 AAC 39.223, 5 AAC 39.200). The ADF&G Genetic Policy
provides the fundamental document for guiding decisions made to protect the genetic integrity of
significant and unique wild stocks (Evenson et al. 2018), and the mission of the ADF&G Gene
Conservation Laboratory includes the protection of these genetic resources. The foundational premise
behind the Genetic Policy guidelines is that salmonid populations have adapted to their native habitats
over long periods of time and, thus, have maximized their fitness. These adaptations among populations
provide increased resilience to variation in environmental conditions (Figge 2004, Schindler et al.
2010); disruption of these adaptations reduces the long-term fitness of populations.
This complex structure of genetically distinct populations can be likened to a financial portfolio in which
assets are divided among diverse investments to increase financial stability. Essentially, it creates a
biological portfolio effect (Lindley et al. 2009, Schindler et al. 2010, Schindler et al. 2015): under any
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Section 3
Importance of the Region's Ecological Resources
given set of conditions, some assets (e.g., discrete Sockeye Salmon populations) will perform well while
others perform less well, but maintenance of the diversified portfolio stabilizes returns over time
because fluctuations of these discrete populations are asynchronous.
The portfolio concept is based on three key principles: (1) diversity provides stabilization; (2) habitat
diversity creates genetic and phenotypic diversity in space and time; and (3) genetic and phenotypic
diversity dampen ecological risk through asynchrony of population dynamics (i.e., spawning, rearing,
migration) across the landscape (Schindler et al. 2010). Across the entire watershed, overall salmon
productivity is stabilized as the relative contributions of Sockeye Salmon that differ in genetic structure
and life-history characteristics and that inhabit different regions of the Bristol Bay watershed change
over time, in response to changing environmental conditions (Hilborn et al. 2003).
Asynchrony in the productivity of different populations within the complex has been demonstrated at
both local and regional scales—that is, across individual tributaries and across the Bristol Bay
watershed's major river systems (Rogers and Schindler 2008, Schindler et al. 2010, Griffiths et al. 2014,
Raborn and Link 2022). This asynchrony among populations is an important characteristic of stable
ecosystems (Rogers and Schindler 2008, Quinn et al. 2012). At the local scale, for example, salmon
populations that spawn in small streams may be negatively affected by low-streamflow conditions,
whereas populations that spawn in lakes may not be affected (Hilborn et al. 2003). At the regional scale,
the relative productivity of Bristol Bay's major rivers has changed over time during different climatic
regimes (Hilborn et al. 2003, Raborn and Link 2022). For example, small Sockeye Salmon runs in the
Egegik River were offset by large runs in the Kvichak River prior to 1977, whereas declining runs in the
Kvichak River were offset by large runs in the Egegik River in the 2000s (EPA 2014: Appendix A, Figure
9). Figure 3-14 illustrates how the proportion of Sockeye Salmon catch from each of Bristol Bay's major
rivers varies both within and across years.
Asynchrony of population dynamics across a diverse set of habitats has enabled the Bristol Bay salmon
fishery to be less variable and more reliable and sustainable than would otherwise be the case (Davis
and Schindler 2021). The high level of system-wide biocomplexity inherent in the overall population
complex structure reduces year-to-year variability in salmon run sizes. Without the portfolio effect,
annual variability in the size of Bristol Bay's Sockeye Salmon runs would be expected to more than
double, and fishery closures would be expected to become more frequent due to a weakening of the
portfolio (Schindler et al. 2010, Griffiths et al. 2014). Simulations have shown that loss of headwater
salmon populations can reverberate throughout the river network, resulting in reduced catch stability
and increased fishery variability at the most downstream locations (Moore 2015). In other watersheds
with previously robust salmon fisheries, such as the Sacramento River's Chinook Salmon fishery, losses
of biocomplexity have contributed to overall salmon population declines (Lindley et al. 2009). Loss of
accessible floodplain and headwater habitats also can be a significant driver of these declines, as
illustrated in Canada's Lower Fraser River (Finn et al. 2021).
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Section 3
Importance of the Region s Ecological Resources
Figure 3-14. Seasonal catch plus escapement of Sockeye Salmon for each genetically distinct
stock in Bristol Bay, Alaska, 2012-2021. Escapement refers to the number of adult salmon that
"escape" harvest and return to freshwaters to spawn, Black vertical lines denote July 4, to facilitate
run timing comparison across years. From Raborn and Link (2022); reprinted with permission.
2012
2017
tf>
c
o
5-
I
4-
3"
c
o
2-
E
1 -
CD
o-
CO
Q.
5 -
TO
O
4-
if)
3-
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Section 3
Importance of the Region's Ecological Resources
ADF&G has identified 11 genetic reporting groups (stocks), corresponding to nine major watersheds of
Bristol Bay42 and the two flanking regions (North Peninsula to the south and Kuskokwim to the north)
(Figure 3-15). In Bristol Bay, a "stock" has been defined as a composite of all populations of a given
species within each of those 11 watersheds (Dann et al. 2009). Each river stock contains tens to
hundreds of wild, locally adapted populations distributed among tributaries and lake habitats. In Bristol
Bay, the ADF&G Sockeye Salmon genetic baseline, which is assembled by sampling spawning
populations contributing to the commercial fishery (Section 3.3.5), has recently increased from 96
populations to 146 distinct populations that range from the Kuskokwim River (to the north) to the
Aleutian Islands (to the south) (Dann et al. 2013). Even this higher value likely underestimates the
actual number of distinct breeding groups. Prior to the development of genetic tools and the current
genetic baseline, Demory et al. (1964) catalogued Sockeye Salmon spawning sites of the Kvichak River
system, including UTC. This catalog represents historical recognition of nearly 100 distinct stream and
beach Sockeye Salmon spawning groups in the Kvichak River system alone. Given technological
advances in genetic methods and the fact that this region has remained largely undeveloped and
undisturbed since this initial estimate, it seems likely that additional genetic diversity will continue to be
identified as further sampling of spawning groups and analysis of genetic structuring occur.
The genetic population structure of Bristol Bay Sockeye Salmon indicates that upper Mulchatna River
fish are distinct from lower Mulchatna River fish, and that both of these populations are genetically
distinct from the upper Nushagak River fish. Sockeye Salmon spawning in the Koktuli River are part of
the Lower Mulchatna River and have recently been determined to be genetically distinct (Dann et al.
2012, Shedd et al. 2016). This incredible local diversity of Sockeye Salmon—which translates to the
robustness of the region's Sockeye Salmon portfolio—reflects the species' ability to exploit a wide range
of habitat conditions, the reproductive isolation of populations created by precise homing to natal
spawning sites and, thus, the species' capacity for microevolution.
42 Figure ES-1 shows six major watersheds draining to Bristol Bay, whereas Dann et al. (2009) refer to nine major
watersheds. This difference results from consideration of the Igushik and Wood River watersheds as distinct from
the Nushagak River watershed and the Alagnak River watershed as distinct from the Kvichak River watershed in
Dann et al. (2009).
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Section 3
Importance of the Region s Ecological Resources
Figure 3-15. Reporting group affiliation for 146 Sockeye Salmon populations in Bristol Bay. These
populations are used to estimate stock composition of catch samples from the Port Moller Test
Fishery and district harvests. SNP = single nucleotide polymorphism, a common type of genetic
marker. From Dann et al. 2013; reprinted with permission.
Stock
District
•
Kuskokwim
Togiak
•
Togiak
Nushagak
•
Igushik
WMA Naknek-Kvichak
O
Wood
Egegik
•
Nushagak
Zl Ugashik
Q
Kvichak
O
Alagnak
Q,'
Naknek
:«Q
Egegik
* •
*"o
Ugashik
•
North Peninsula
Baseline Summary
22,286 Individuals
233 Collections
146 Populations
11 Stocks
96 SNPs
*
The close management of mixed-stock fisheries allows for the capitalization of genotypic and phenotypic
diversity of Bristol Bay Sockeye Salmon while spreading the risk to any one stock across the stock
portfolio (Veale and Russello 2017). The buffering effect of the salmon portfolio is reflected in the 2022
Bristol Bay Sockeye Salmon Forecast (ADF&G 2021a), which reports that individual river forecasts have
greater uncertainty compared to the Bristol Bay-wide forecast. ADF&G (2021a) notes that since 2001,
the forecast has, on average, underestimated returns to the Alagnak (-33 percent), Togiak (-14 percent),
Kvichak (-21 percent), Wood (-20 percent), Nushagak (-25 percent), Ugashik (-5 percent), and Naknek
(-15 percent) Rivers, and overestimated returns to the Igushik (11 percent) and Egegik Rivers
(13 percent). Over-forecasting returns to some rivers while under-forecasting returns to other rivers
means that the overall Bristol Bay forecast is often more accurate than the forecast to any individual
river. This illustrates the power of a diverse stock portfolio to provide sustained resiliency to Bristol
Bay's Sockeye Salmon fishery, by buffering risk to any one stock temporally and spatially across multiple
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Section 3
Importance of the Region's Ecological Resources
stocks: certain rivers may have lower than expected returns in a given year due to environmental
conditions and other factors, but these losses can be offset by higher than expected returns in other
rivers (Figure 3-14).
Baseline genetic research suggests that other Bristol Bay fisheries, in addition to Sockeye Salmon, may
also be stabilized by the portfolio effect; in fact, the basic biology of these species makes such
stabilization virtually inevitable. However, other Pacific salmon species have been less intensively
studied in general, and their genetic baselines are not currently as advanced as they are for Sockeye
Salmon. Coho Salmon in western Alaska tend to occur in smaller, more isolated populations (Olsen et al.
2003). Thus, Coho Salmon may have higher rates of genetic differentiation than nearby populations of
other salmon species (e.g., Chum Salmon) in this region, and the loss of Coho Salmon populations may be
more likely to translate to loss of significant amounts of overall genetic variability (Olsen et al. 2003,
Schindler et al. 2018). Chinook Salmon populations also tend to be relatively small (Healey 1991) and
exhibit diverse life history traits (e.g., variations in size and age at migration, duration of freshwater and
estuarine residency, time of ocean entry) (Lindley et al. 2009). Chinook populations in the Togiak River
differ in spawning habitats (mainstem versus tributary) and migration timing, which translate to a clear
stock structure (Sethi and Tanner 2014, Clark et al. 2015). Radio telemetry, tagging, phenotypic
variation, and genetic studies also indicate that multiple Rainbow Trout populations are found in the
Bristol Bay watershed (Burger and Gwartney 1986, Minard et al. 1992, Krueger et al. 1999, Meka et al.
2003, Dye and Borden 2018, Arostegui and Quinn 2019b, Arostegui et al. 2019).
The potential for fine-scale population structuring of salmon fisheries, particularly in terms of Sockeye
and Coho salmon, exists throughout the entire Bristol Bay watershed. Finer-scale habitats can sustain
unique, genetically distinct populations, each of which helps to maintain the integrity of overall salmon
stocks across the Bristol Bay watershed and contributes to the overall resilience of these stocks to
perturbation. For example, Sockeye Salmon populations in proximity to each other show phenotypic
differences related to differences in spawning habitats (Lin et al. 2008b, Ramstad et al. 2010), and
Sockeye Salmon that use spring-fed ponds and streams as close as approximately 0.6 mile (1 km) apart
exhibit differences in traits (e.g., spawn timing and productivity) that suggest they may comprise
discrete populations (Quinn et al. 2012). Genetic population structure also occurs at a fine geographic
scale for Coho Salmon, with many populations found in small first- and second-order headwater streams
(Olsen et al. 2003). The ability of Bristol Bay to sustain diverse salmon populations therefore depends
on sustaining the viability of the vast network of unique habitats at small spatial scales across the
landscape. This suggests that even the loss of a small population within the Bristol Bay watershed's
overall salmon populations may have more significant effects than expected, due to the associated loss
of genetic and phenotypic diversity of a discrete population (Schindler et al. 2010, Moore et al. 2014,
Waples and Lindley 2018).
In summary, a substantial body of research supports the conclusion that a diversity of habitats is
necessary for maintaining locally adapted populations that create a stock portfolio of individual species.
The multiple, genetically distinct populations of Sockeye Salmon that have been documented in the SFK,
NFK, and UTC watersheds contribute to the region's wild salmon portfolio. It is clear from the evolving
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Importance of the Region's Ecological Resources
understanding of the stabilizing effects of the salmon portfolio that the conservation of habitat diversity
and connectivity, which leads to locally adapted population diversity across the landscape, is critical to
achieve and maintain the sustainability of Bristol Bay's salmon populations.
3.3.4 Salmon and Marine-Derived Nutrients
Salmon play a crucial role in maintaining and supporting the overall productivity of the Bristol Bay
watershed. Salmon are a cornerstone species in the Bristol Bay region in that they comprise a significant
portion of the resource base upon which both aquatic and terrestrial ecosystems in the region depend
(Willson et al. 1998). Approximately 95 to 99 percent of the carbon, nitrogen, and phosphorus in an
adult salmon's body is derived from the marine environment during their ocean feeding period (Larkin
and Slaney 1997, Schindler et al. 2005). Adult salmon returning to their natal freshwater habitats to
spawn import these marine-derived nutrients (MDN) back into these freshwater habitats, spatially and
temporally across the watershed (Cederholm et al. 1999, Gende et al. 2002). MDN from salmon account
for a significant portion of nutrient budgets in the Bristol Bay watershed (Kline et al. 1993). For
example, Sockeye Salmon were estimated to import approximately 14 tons (12.7 metric tons) of
phosphorus and 11 tons (10.1 metric tons) of nitrogen into the Wood River system, and 55 tons (50.2
metric tons) of phosphorus and 438 tons (397 metric tons) of nitrogen into the Kvichak River system,
annually (Moore and Schindler 2004). These nutrients provide the foundation for aquatic and terrestrial
foodwebs via two main pathways: direct consumption of salmon in any of its forms (spawning adults,
eggs, carcasses, and/or juveniles) and nutrient recycling (Gende et al. 2002).
Given that aquatic systems in the Bristol Bay watershed tend to be nutrient-poor, MDN contributions
play a significant role in the Bristol Bay region's productivity. However, the distribution and relative
importance of the trophic subsidies provided by MDN within salmon-bearing watersheds are not
expected to be spatially or temporally uniform (Janetski et al. 2009). MDN concentrations will be highest
in areas of high spawning density and where carcasses accumulate. Adult salmon are found in
headwater streams of the SFK, NFK, and UTC watersheds, sometimes in extremely high numbers
(Table 3-8); thus, MDN are likely contributing to the biological productivity of these headwaters and
downstream habitats.
Where salmon are abundant, productivity of the Bristol Bay region's fish and wildlife species is highly
dependent on this influx of MDN into the region's freshwater habitats (EPA 2014: Box 5-3). When and
where available, salmon-derived resources—in the form of eggs, carcasses, and invertebrates that feed
upon carcasses—are important dietary components for many fishes (e.g., juvenile Pacific salmon,
Rainbow Trout, Dolly Varden, Arctic Grayling). Numerous studies have shown that the availability of
MDN benefits stream-dwelling fishes via enhanced growth rate (Bilby et al. 1996, Wipfli et al. 2003,
Giannico and Hinch 2007), body condition (Bilby et al. 1998), energy storage (Heintz et al. 2004), and
ultimately increased chance of survival to reproductive age and adulthood (Gardiner and Geddes 1980,
Wipfli et al. 2003, Heintz et al. 2004).
Eggs from spawning salmon are a major food source for Bristol Bay Rainbow Trout and are likely
responsible for much of the growth attained by these fish and the abundance of trophy-sized Rainbow
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Importance of the Region's Ecological Resources
Trout in the Bristol Bay system. Scheuerell et al. (2007) reported that upon arrival of spawning salmon
in the Wood River basin, Rainbow Trout shifted from consuming aquatic insects to primarily salmon
eggs, resulting in a five-fold increase in ration and energy intake. With this rate of intake, a bioenergetics
model predicted a 3.5-ounce (100-g) trout would gain 2.9 ounces (83 g) in 76 days; without the
salmon-derived subsidy, the same fish was predicted to lose 0.2 ounce (5 g) (Scheuerell et al. 2007).
Rainbow Trout in Lower Talarik Creek, a stream immediately west of UTC, were significantly fatter (i.e.,
had a higher condition factor) in years with high salmon spawner abundance than in years with low
abundance (Russell 1977).
Rainbow Trout are not the only fish species to benefit from these MDN subsidies. Research in Iliamna
Lake suggests that between 29 percent and 71 percent of the nitrogen in juvenile Sockeye Salmon, and
even higher proportions in other aquatic taxa, comes from MDN, and that the degree of MDN influence
increases with escapement (Kline et al. 1993). In the Kvichak River, Dolly Varden move into ponds
where Sockeye Salmon are spawning and experience three-fold higher growth rates when salmon eggs
are available as a food source (Denton et al. 2009); Dolly Varden in the Iliamna River similarly rely
heavily on MDN subsidies in the form of salmon eggs, carcasses, and associated invertebrates (Jaecks
and Quinn 2014).
By dying in the habitats in which they spawn, adult salmon add their nutrients to the ecosystem that will
feed their young and, thus, subsidize the next generation. In lakes and streams, MDN help to fuel the
production of algae, bacteria, fungi, and other microorganisms that make up aquatic biofilms. These
biofilms, in turn, provide food for aquatic invertebrates. MDN inputs are associated with increased
standing stocks of macroinvertebrates (Claeson et al. 2006, Lessard and Merritt 2006, Walter et al.
2006), a primary food resource for juvenile salmon and other stream-dwelling fishes.
The importance of MDN to fish populations is perhaps most clearly demonstrated in cases where MDN
supplies are disrupted by depletion of salmon populations. For example, prolonged depression of
salmon stocks in the Columbia River basin in Oregon has resulted in a chronic nutrient deficiency that
hinders the recovery of endangered and threatened Pacific salmon stocks (Gresh et al. 2000, Petrosky et
al. 2001, Achord et al. 2003, Peery et al. 2003, Scheuerell et al. 2005, Zabel et al. 2006) and diminishes
the potential of expensive habitat improvement projects (Gresh et al. 2000). Density-dependent
mortality has been documented among juvenile Chinook Salmon, despite the fact that populations have
been reduced to a fraction of historical levels, suggesting that nutrient deficits have reduced the carrying
capacity of spawning streams in the Columbia River basin (Achord et al. 2003, Scheuerell et al. 2005).
Thus, diminished salmon runs can create a negative feedback loop, in which the decline in spawner
abundance reduces the capacity of streams to produce new spawners (Levy 1997).
It is not just aquatic systems that benefit from these salmon-based MDN subsidies. Terrestrial mammals
(e.g., Brown Bears, wolves, foxes, minks) and birds (e.g., Bald Eagles, waterfowl) also benefit from these
subsidies (Brna and Verbrugge 2013, EPA 2014: Chapter 5; Armstrong et al. 2016). Alaskan Brown
Bears aggregate and exhibit fidelity in their foraging of salmon in small streams in the Bristol Bay
watershed (Wirsing et al. 2018). Availability and consumption of salmon-derived resources can have
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Importance of the Region's Ecological Resources
significant benefits for these species, including increased growth rate, energy storage, litter size, nesting
success, and population density (Brna and Verbrugge 2013). In response to temporally shifting
distributions of spawning Sockeye Salmon, species such as Brown Bears and gulls change their spatial
distributions within the Bristol Bay watershed over the course of the summer (Schindler et al. 2013).
Bears, wolves, and other wildlife also transport carcasses and excrete wastes throughout their ranges
(Darimont et al. 2003, Helfield and Naiman 2006), thereby providing food and nutrients for other
terrestrial species.
3.3.5 Commercial Fisheries
All five species of Pacific salmon are commercially harvested in Bristol Bay, across five fishing districts
identified by specific rivers draining to the bay (Table 3-12). Sockeye Salmon dominate the region's
salmon runs and harvest by a large margin (Table 3-12). Management of the Sockeye Salmon fishery in
Bristol Bay is focused on discrete stocks (Section 3.3.3.2) (Tiernan et al. 2021), and the fishery's success
depends on the conservation of biodiversity and sound, conservative management based on sustainable
yields (ADF&G 2022d). Bristol Bay is home to the largest Sockeye Salmon fishery in the world, with
46 percent of the average global abundance of wild Sockeye Salmon between 1956 and 2005
(Ruggerone et al. 2010); between 2015 and 2019, Bristol Bay contributed 53 percent of global Sockeye
Salmon production (McKinley Research Group 2021). Annual commercial harvest of Sockeye Salmon
averaged 31.5 million fish between 2010 and 2019 (Table 3-12) (Tiernan et al. 2021). The 2021
commercial harvest of 40.4 million Sockeye Salmon was 44 percent higher than the recent 20-year
average of 28.0 million for all districts (ADF&G 2021b). In 2021, 66.1 million Sockeye Salmon returned
to Bristol Bay (ADF&G 2021b); this number increased by almost 20 percent in 2022, to 79.0 million—
the largest inshore Sockeye Salmon run ever recorded in the region (ADF&G 2022e). More than half of
the Bristol Bay watershed's Sockeye Salmon harvest comes from the Nushagak and Kvichak River
watersheds (Table 3-12) (EPA 2014: Figure 5-9B).
bockeye
10 737,106 (34)
7,595,433 (24)
3,439,233 (11)
9,059,705 (29)
636,660 (2)
31,468,532
Chinook
2,168 (7)
930 (3)
753 (2)
25,111 (76)
3,983 (12)
32,945
Coho
2,316 (2)
8,012 (6)
630 (2)
91,263 (72)
25,215 (18)
127,436
Chum
233,281 (22)
72,472 (7)
50,366 (5)
540,280 (51)
163,062 (15)
1,059,464
Pink b
12,362 (1)
1,972 (<1)
539 (<1)
802,849 (88)
94,282 (10)
912,004
Notes:
a Naknek-Kvichak district includes the Alagnak River; Nushagak district includes the Wood and Igushik Rivers.
b Pink Salmon data are from even-numbered years only; harvest is negligible during odd-year runs.
Source: Tiernan et al. 2021.
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The Nushagak River watershed supported 72 percent of commercial Coho Salmon catch in the region
between 2010 and 2019 (Table 3-12). Although Chinook Salmon is the least common salmon species
across the Bristol Bay region, the Nushagak River watershed also supports a large Chinook Salmon
fishery, and its commercial harvests are greater than those of all other Bristol Bay river systems
combined (Table 3-12). Between 2010 and 2019, on average 76 percent of Bristol Bay's commercial
Chinook Salmon catch came from the Nushagak fishing district (Table 3-12). Chinook Salmon returns to
the Nushagak River are consistently greater than 100,000 fish per year and have exceeded 200,000 fish
per year in 11 years between 1966 and 2010. This frequently places the Nushagak River at or near the
size of the world's largest Chinook Salmon runs, which is notable given the Nushagak River's small
watershed area compared to other Chinook-producing rivers (EPA 2014: Chapter 5).
Given the productivity of Pacific salmon, the commercial salmon fishery currently provides the Bristol
Bay region's greatest source of economic activity, creating thousands of jobs and generating $1 billion or
more in economic output value through commercial fishing, processing, and support activities (Knapp et
al. 2013, Wink Research and Consulting 2018, USACE 2020a, McKinley Research Group 2021). The
McKinley Research Group (2021) estimates that in 2019, Bristol Bay's commercial fishery and related
activities resulted in 15,000 jobs and an economic impact of $2.0 billion, $990 million of which was in
Alaska. From 2000 through 2019, annual commercial salmon harvest in Bristol Bay averaged more than
27 million fishes across all five species (Tiernan et al. 2021). The annual ex-vessel commercial value43 of
this catch averaged $147.9 million, $146.4 million of which resulted from the Sockeye Salmon fishery
(Table 3-13). In 2019, approximately 23 percent of Bristol Bay salmon permit holders were residents of
the Bristol Bay watershed, and an additional 29 percent were residents of other areas in Alaska
(McKinley Research Group 2021). This ex-vessel value translates to even higher wholesale values: for
example, the 2010 Bristol Bay Sockeye Salmon harvest was worth $165 million in direct harvest value
and $390 million in first wholesale value after processing (Knapp et al. 2013).
Sockeye
146.372
31.962 (2002)
344.253 (2018)
Chinook
420
135 (2001)
1,240 (2006)
Coho
409
18 (2002)
1,990 (2014)
Chum
1,392
228 (2000)
2,891 (2018)
Pinka
436
0 (2002)
1,567 (2010)
TOTAL
147,874
32,544 (2002)
348,579 (2018)
Notes:
a Pink Salmon data are from even-numbered years only; harvest is negligible during odd-year runs.
Source: Tiernan et al. 2021: Appendix A24.
43 Ex-vessel commercial value is the value paid to the fisher or permit holder upon delivery.
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Importance of the Region's Ecological Resources
3.3.6 Subsistence Fisheries
In the Bristol Bay region, the subsistence way of life is irreplaceable. Subsistence resources provide
high-quality foods, foster a healthy lifestyle, and form the basis for social relations. Alaska Natives are
the majority population in the Bristol Bay region, and salmon has been central to their health, welfare,
and culture for thousands of years. In fact, Alaska Native cultures in the region represent one of the last
intact salmon-based cultures in the world (EPA 2014: Appendix D). Much of the region's population—
including both Alaska Natives and non-Alaska Natives—practices subsistence, with salmon making up a
large proportion of subsistence diets. Thus, residents in this region are particularly vulnerable to
potential changes in salmon resources (see Section 6.3 for discussion of tribal considerations, including
environmental justice concerns).
There are 31 Alaska Native villages in the wider Bristol Bay region, 25 of which are located in the Bristol
Bay watershed. Fourteen of these communities are within the Nushagak and Kvichak River watersheds,
with a total population of 4,197 in 2020 (U.S. Census Bureau 2022). Dillingham (population 2,249) is the
largest community; other communities range in size from four (year-round) residents (Portage Creek)
to 512 residents (New Stuyahok). In some communities the population increases during the subsistence
fishing season. Thirteen of these 14 villages—all but Port Alsworth—have federally recognized tribal
governments and had an Alaska Native population majority in 2020. No towns, villages, or roads are
currently located in the SFK, NFK, and UTC watersheds. However, this area has been noted as important
to the health and abundance of subsistence resources by traditional knowledge experts from
communities in the area.
This following sub-sections discuss the use of subsistence fisheries in the region and its nutritional,
cultural, and spiritual importance. Subsistence related to foods other than fish is discussed in Section 6.3.1.
3,3,6,1 Use of Subsistence Fisheries
Alaska Native populations of the Bristol Bay watershed, as well as non-Alaska Native residents, have
continual access to a range of subsistence foods. As described by Fall et al. (2009), these subsistence
resources are the most consistent and reliable component of local economies in the Bristol Bay
watershed, even given the world-renowned commercial fisheries and other recreational opportunities
the region supports.
Virtually every household in the Nushagak and Kvichak River watersheds uses subsistence resources
(EPA 2014: Appendix D, Table 12). No watershed-wide data are available for the proportion of
residents' diets made up of subsistence foods, as most studies focus on harvest data and are not dietary
surveys. However, data from 2014 indicate that the overall composition of wild food harvest in the
Bristol Bay area is composed of 58 percent salmon, 20 percent land mammals (mostly moose and
caribou), 9 percent other fishes, and 13 percent other sources (marine mammals, birds, eggs, marine
invertebrates and wild plants) (Halas and Neufeld 2018). In 2004 and 2005, annual subsistence
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Importance of the Region's Ecological Resources
consumption rates in the Nushagak and Kvichak River watersheds were over 300 pounds per person in
many villages and reached as high as 900 pounds per person (EPA 2014: Appendix D, Table 12).44
Subsistence use varies throughout the Bristol Bay watershed, as villages differ in the per capita amount
of subsistence harvest and the variety of subsistence resources used (Table 3-14). Salmon and other
fishes are harvested throughout the Nushagak and Kvichak River watersheds (Figure 3-16) and provide
the largest portion of subsistence harvests of Bristol Bay communities. On average, about 50 percent of
the subsistence harvest by local community residents (measured in pounds usable weight) is Pacific
salmon, and about 10 percent is other fishes (Fall et al. 2009). The percentage of salmon harvest in
relation to all subsistence resources ranges from 29 percent to 82 percent in the villages (EPA 2014:
Appendix D, Table 11); see Section 6.3.1 for further discussion of non-fish subsistence resources.
Aleknagik
2008
51.738
143
40
72
26
100
59
59
Dillingham
2010
486,533
131
46
55
7
91
57
56
Ekwok
1987
77,268
456
160
180
68
93
48
52
Igiugig
2005
22,310
205
168
5
59
100
83
83
lliamna
2004
34,160
370
370
0
34
100
31
39
Kokhanok
2005
107,644
513
480
3
36
97
63
60
Koliganek
2005
134,779
565
688
194
90
100
61
54
Levelock
2005
17,871
152
86
43
40
93
36
79
New Stuyahok
2005
163,927
188
36
113
28
90
55
63
Newhalen
2004
86,607
502
488
10
32
100
64
32
Nondalton
2004
58,686
219
219
0
34
92
55
63
Pedro Bay
2004
21,026
250
250
0
15
100
72
78
Port Alsworth
2004
14,489
89
88
1
12
100
46
55
Notes:
a Total harvest values represent usable weight and include fishes, land mammals, freshwater seals, beluga, other marine mammals, plant-based
foods, birds or eggs, and marine invertebrates. See Section 6.3.1 for additional information on non-fish subsistence resources.
Source: Schichnes and Chythlook 1991 (Ekwok), Fall et al. 2006 (lliamna, Newhalen, Nondalton, Pedro Bay, and Port Alsworth); Krieg et al. 2009
(Igiugig, Kokhanok, Koliganek, Levelock, New Stuyahok); Holen et al. 2012 (Aleknagik); Evans et al. 2013 (Dillingham).
44 For comparison, an average American consumes roughly 2,000 pounds of food per year.
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Section 3
Importance of the Region's Ecological Resources
Figure 3-16. Subsistence harvest and harvest-effort areas for salmon and other fishes in the
Nushagak and Kvichak River watersheds. Other fishes are those classified as Arctic Char, Dolly
Varden, Humpback Whitefish, Lake Trout, Least Cisco, Rainbow Trout, Round Whitefish, Steelhead
(anadromous Rainbow Trout), trout, and whitefish in relevant subsistence use reports (Fall et al.
2006, Krieg et al. 2009, Holen and Lemons 2010, Holen et al. 2011, Holen et al. 2012).
KVICHAK
Alsworth
NUSHAGAK
Rive*
lewhalen'
Ilia mmi Lake
Stuyahok
(Jeknagik
ikwok
Clark's Point
Naknek
King Salmon
~
Approximate Pebble Deposit Location
0
Nonsurveyed Towns and Villages
•
Surveyed Towns and Villages
Other Fish Harvest Areas
Salmon Harvest Areas
~
Nushagak and Kvichak
River Watersheds
Existing Roads
N
A
0
1 1
A
25
i i II i i
50
j 1
Miles
0
1 1
4^
O
80
i_I
Kilometers
Bristol Bay
Cook Inlet
South Naknek
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Between 2008 and 2017, average annual subsistence salmon harvest in the Nushagak district was
49,024 fishes and in the Naknek-Kvichak district was 66,174 fishes (Halas and Neufeld 2018). There are
differences in the relative importance of different subsistence fisheries between the two watersheds,
however. Sockeye Salmon comprised 97 percent of this harvest in the Naknek-Kvichak district but only
53 percent in the Nushagak district, where Chinook Salmon (25 percent) and Coho Salmon (11 percent)
were larger subsistence resources (Halas and Neufeld 2018). Villages along the Nushagak River (e.g.,
Ekwok, New Stuyahok) are particularly dependent on Chinook Salmon as a subsistence resource
(Table 3-14), in part because Chinook Salmon are the first spawners to return each spring (EPA 2014:
Appendix D). Between 2008 and 2017, average annual subsistence harvest of Sockeye Salmon ranged
from 740 fish in Levelock to 27,755 fish in Dillingham (Table 3-15).
I
Aleknagik
2,623
1,570 (2010)
3,560 (2014)
Dillingham
27,755
22,037 (2012)
33,220 (2016)
Ekwok
1,849
1,253 (2012)
2,700 (2014)
Igiugig
1,346
345 (2013)
2,901 (2010)
Iliamna/Newhalen
10,564
6,403 (2017)
15,433 (2011)
Kokhanok
11,136
5,430 (2017)
16,530 (2012)
Koliganek
3,573
2,085 (2015)
7,290 (2013)
Levelock
740
30 (2008)
1,265 (2016)
New Stuyahok
6,727
5,062 (2012)
11,104 (2013)
Nondalton
7,215
2,320 (2016)
10,550 (2013)
Pedro Bay
3,742
1,678 (2017)
7,802 (2009)
Port Alsworth
4,024
3,155 (2009)
6,588 (2015)
Notes:
a For communities in the Kvichak River watershed, number represents Sockeye Salmon harvest; for communities in the Nushagak River
watershed, number represents all salmon species.
Source: Halas and Neufeld 2018.
All communities in the Nushagak and Kvichak River watersheds also rely on non-salmon fishes,
including Northern Pike, various whitefish species, Dolly Varden, Arctic Char, and Arctic Grayling, but to
a lesser extent than salmon. These fishes are taken throughout the year by a variety of harvest methods
and fill an important seasonal component of subsistence cycles (Halas and Neufeld 2018). Non-salmon
fishes are particularly important subsistence resources in spring and fall, when salmon and other
resources are less available (Hazell et al. 2015). For example, in the mid-2000s, annual subsistence
harvests for 10 communities in the Nushagak and Kvichak River watersheds were estimated at
3,450 Dolly Varden/Arctic Char (Alaska's fisheries statistics do not distinguish between the two
species); 4,385 Northern Pike; and 7,790 Arctic Grayling (Fall et al. 2006, Krieg et al. 2009). Northern
Pike were the most important non-salmon fishes in four of those villages during that time (Fall et al.
2006, Krieg et al. 2009). From the mid-1970s to the mid-2000s, Dolly Varden/Arctic Char, Northern
Pike, and Arctic Grayling were estimated to represent roughly 16 to 27 percent, 10 to 14 percent, and 7
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Importance of the Region's Ecological Resources
to 10 percent of the total weight of the Kvichak River watershed's non-salmon freshwater fish
subsistence harvest, respectively (Krieg et al. 2005).
Although subsistence is a non-market economic activity that is not officially measured, the effort put
into subsistence activities is estimated to be the same as or greater than full-time equivalent jobs in the
cash sector (EPA 2014: Appendix E). There is a strong and complex relationship between subsistence
and the market economy (largely commercial fishing and recreation) in the area (Wolfe and Walker
1987, Krieg et al. 2007). For example, income from the market economy funds household purchases of
goods and services that are then used for subsistence activities (e.g., boats, rifles, nets, snowmobiles, and
fuel). When Alaskan households spend money on subsistence-related supplies, the subsistence harvest
of fishes generates regional economic benefits. In total, individuals in Bristol Bay communities harvest
about 2.6 million pounds of subsistence foods per year (EPA 2014: Chapter 5). In 2010, the U.S. Census
Bureau reported an estimated 1,873 Alaska Native and 666 non-Alaska Native households in the Bristol
Bay region. Goldsmith et al. (1998) estimated that Alaska Native households spend an average of $3,054
on subsistence harvest supplies, whereas non-Alaska Native households spend an estimated $796 on
supplies (values updated to 2009 price levels). Based on these estimates, subsistence harvest activities
resulted in expenditures of approximately $6.3 million (EPA 2014: Table 5-4).
The estimates above reflect only the annual economic activity generated by subsistence activities and
not the value of the subsistence resources harvested. A study by the McKinley Research Group (2021)
estimated that the replacement value of the 2017 Bristol Bay subsistence salmon harvest—that is, the
cost of replacing subsistence salmon protein with store-bought substitutes—was between $5 million
and $10 million (Table 3-16).
Pounds of usable fish
98,199
22,907
39,776
1,441
341,567
503,890
Species-specific % of total usable fish
19
5
8
0
68
100
Replacement value at $10 per pound
$981,992
$229,066
$397,762
$14,411
$3,415,673
$5,038,904
Replacement value at $20 per pound
$1,963,980
$458,140
$795,524
$28,820
$6,831,346
$10,077,800
Source: McKinley Research Group 2021.
3,3,6,2 Importance of Subsistence Fisheries
The salmon-dependent diet of Alaska Natives benefits their physical and mental well-being in multiple
ways, in addition to encouraging high levels of fitness based on subsistence activities. Salmon and other
traditional wild foods make up a large part of people's daily diets throughout their lives, beginning as
soon as they are old enough to eat solid food (EPA 2014: Appendix D). Disproportionately high amounts
of total diet protein and some nutrients come from subsistence foods. For example, a 2009 study of two
rural Alaska regions found that 46 percent of protein, 83 percent of vitamin D, 37 percent of iron,
35 percent of zinc, 34 percent of polyunsaturated fat, 90 percent of eicosapentaenoic acid, and
93 percent of docosahexaenoic acid came from subsistence foods consumed by Alaska Natives (Johnson
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et al. 2009). These foods have demonstrated nutritional benefits, including lower cumulative risk of
nutritionally mediated health problems such as diabetes, obesity, high blood pressure, and heart disease
(Murphy et al. 1995, Dewailly et al. 2001, Dewailly et al. 2002, Din et al. 2004, Hall et al. 2005, Chan et al.
2006, Ebbesson et al. 2007) and provision of essential micronutrients and omega-3 fatty acids (Murphy
et al. 1995, Nobmann et al. 2005, Bersamin et al. 2007, Ebbesson et al. 2007). In addition, the cost of
replacing subsistence salmon in diets, even with lower-quality protein sources, is likely to be significant
(Table 3-16).
However, for Alaska Natives, subsistence is much more than the harvesting, processing, sharing, and
trading of foods. Subsistence holistically subsumes the cultural, social, and spiritual values that are the
essence of Alaska Native cultures (USACE 2020a: Section 3.9). Traditional and more modern spiritual
practices place salmon in a position of respect and importance, as exemplified by the First Salmon
Ceremony and the Great Blessing of the Waters (EPA 2014: Appendix D). The salmon harvest provides a
basis for many important cultural and social practices and values, including the sharing of resources,
fish camp, gender and age roles, and the perception of wealth. Tribal Elders and culture bearers
continue to instruct young people, particularly at fish camps where cultural values, as well as fishing and
fish processing techniques, are shared. The social system that forms the backbone of the culture, by
nurturing the young, supporting the producers, and caring for the tribal Elders, is based on the virtue of
sharing wild foods harvested from the land and waters.
The importance of salmon as a subsistence food source is inseparable from it being the basis for Alaska
Native cultures. The characteristics of the subsistence-based salmon cultures in the Bristol Bay region
have been widely documented (EPA 2014: Appendix D). The cultures have a strong connection to the
landscape and its resources, and in the Bristol Bay watershed this connection has been maintained for
centuries by the uniquely pristine condition of the region's landscape and resources. In turn, the respect
and importance given salmon and other wildlife, along with Alaska Natives' traditional knowledge of the
environment, have produced a sustainable, subsistence-based economy (EPA 2014: Appendix D). This
subsistence-based way of life is a key element of Alaska Native identity and serves a wide range of
economic, social, and cultural functions (USACE 2020a: Section 3.9).
3.3.7 Recreational Fisheries
In addition to commercial and subsistence fisheries, the Bristol Bay region also supports world-class
recreational or sport fisheries. The Bristol Bay watershed (as reflected by the Bristol Bay Sport Fish
Management Area, or BBMA) has been acclaimed for its sport fisheries, for fishes such as Pacific salmon,
Rainbow Trout, Arctic Grayling, Arctic Char, and Dolly Varden, since the 1930s (Dye and Borden 2018).
The uncrowded, pristine wilderness setting of the Bristol Bay watershed attracts recreational fishers,
and aesthetic qualities are rated by Bristol Bay anglers as most important in selecting fishing locations
(Duffield et al. 2007).
The importance of recreational fisheries can be estimated in several ways, including their economic
value, the effort expended by recreational fishers, the number of fishes harvested, and the number of
fishes caught (i.e., those harvested in addition to those caught and released).
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Sport fishing in the Bristol Bay watershed accounts for approximately $66.58 million expenditures,
expressed in 2020 dollars (USACE 2020a: Section 3.6). In 2009, approximately 29,000 sport-fishing trips
were taken to the Bristol Bay region (12,000 trips by people living outside of Alaska, 4,000 trips by
Alaskans living outside the Bristol Bay area, and 13,000 trips by Bristol Bay residents). These sport-
fishing activities directly employ over 800 full- and part-time workers. In 2010, 72 businesses and 319
guides were operating in the Nushagak and Kvichak River watersheds alone, down from a peak of 92
businesses and 426 guides in 2008 (Rinella et al. 2018).
Between 2007 and 2017, angler-days of effort within the BBMA ranged from 74,560 to 102,844
annually, with total annual sport harvest for the same period ranging from 42,082 to 58,658 fishes (Dye
and Borden 2018). Guided sport-fishing effort between 2007 and 2016 averaged 32,821 angler-days
across the BBMA, of which approximately 7,059 and 1,704 angler-days were spent in the Nushagak
River and Kvichak River watersheds, respectively (Dye and Borden 2018).
The majority of sport fishes harvested in the BBMA are Sockeye, Chinook, and Coho salmon, although
Rainbow Trout, Dolly Varden, Arctic Char, and other species are also harvested throughout the BBMA
(Table 3-17) (Dye and Borden 2018). The Nushagak and Kvichak River watersheds support several
popular recreational fisheries, particularly for Sockeye and Chinook salmon (Figure 3-17), as well as
Rainbow Trout. The Nushagak River watershed accounted for more than 50 percent of the annual
average sport harvest (2004-2017) of Chinook Salmon in the BBMA, with an estimated harvest of 6,467
out of a total estimated harvest of 10,937 fish (Dye and Borden 2018); estimated recreational Chinook
Salmon catches are much higher (Table 3-18). In the Kvichak River, recreational harvests are dominated
by Sockeye Salmon, whereas recreational catches are dominated by Rainbow Trout.
Table 3-17. Estimated sport harvest by species in the Bristol Bay Sport Fish Management Are
¦
Sockeye Salmon
15,876
11,925 [2005]-23,842 [2017]
Chinook Salmon
10,836
6,224 [2010]-13,821 [2007]
Coho Salmon
15,682
12,380 [2013]-20,699 [2014]
Chum Salmon
1,627
501 [2007]-2,946 [2013]
Pink Salmon
805
47 [2009]-3,138 [2004]
Rainbow Trout
1,117
323 [2013]-2,411 [2007]
Dolly Varden/Arctic Char
2,498
1,040 [2013]-6,365 [2004]
Arctic Grayling
1,179
361 [2016]-3,010 [2004]
Lake Trout
759
188 [2012]-1,370 [2011]
Northern Pike
931
216 [2016]-1,751 [2004]
Source: Dye and Borden 2018.
BBMA = Bristol Bay Sport Fish Management Area
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Section 3 Importance of the Region's Ecological Resources
Figure 3-17. Popular areas for recreational fishing in the Nushagak and Kvichak River
watersheds. Areas were digitized from previously published maps (Dye et al. 2006). Areas for
recreational Rainbow Trout fishing are also distributed throughout the watersheds.
KVICHAK
Port Alsworth
NUSHAGAK
'Nondalton
Creek
Pedro Bt
Rfvej
liamna
Newhalen
Iliam na Lake
New Stuyahok
Kokhanok
Portage
Bristol Bay
• Towns arid Villages
ZZA Chinook Salmon
Sockeye Salmon
Pebble Deposit
IMushagak and Kvichak
Watersheds
Bull"/
"A[oska
0 30 60
1 I I I I I I I I
Miles
0 50 100
L i i i I i i I I
Kilometers
Cook Inlet
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Table 3-18. Estimated annual sport harvest and catch of fishes in the Kvichak River watershed and
the Nushagak, Wood, and Togiak River watersheds, 2008-2017. Estimated annual sport harvest is
Kvichak River
Pacific salmon a
7,199-14,731
56,492
Sockeye
5,383-13,025
30,349
Chinook
206-1,427
4,424
Coho
342-676
9,138
Chum
26-898
11,950
Pink
10-625
631
RainbowTrout
48-996
114,431
Dolly Varden/Arctic Char
46-605
16,239
Arctic Grayling
84-757
18,695
Lake Trout
124-856
2,224
Northern Pike
11-547
1,938
Whitefish
0-449
179
Nushagak, Wood,
Pacific salmon a
10,252-15,435
85,719
and Togiak River
Sockeye
1,598-5,504
12,514
Chinook
4,514-9,283
31,631
Coho
839-1,924
30,034
Chum
561-2,560
9,216
Pink
0-664
2,324
RainbowTrout
52-450
30,282
Dolly Varden/Arctic Char
740-2,051
25,222
Arctic Grayling
54-725
20,833
Lake Trout
10-206
1,196
Northern Pike
78-1,064
1,654
Whitefish
0-514
602
Notes:
a Total for all five Pacific salmon species (Coho, Chinook, Sockeye, Chum, Pink).
Source: Romberg et al. 2021.
3.3.8 Region's Fisheries in the Global Context
The Bristol Bay region is a unique environment supporting world-class fisheries, particularly in terms of
Pacific salmon populations. Recent Sockeye Salmon returns to Bristol Bay highlight the region's
productivity relative to other watersheds in the United States: the number of Sockeye Salmon that
returned to Bristol Bay in 2022 (79.0 million)—more than 60 percent of which returned to the
Nushagak and Naknek-Kvichak River watersheds—is roughly 20 million more than the number of
individuals of all Pacific salmon species that historically returned to Washington, Oregon, and California
before these rivers were dammed (Gresh et al. 2000, ADF&G 2022e). The region takes on even greater
significance when one considers the status and condition of Pacific salmon populations throughout their
native geographic distributions. These declines are discussed briefly below; for additional information
on threatened and endangered salmon stocks, see Appendix A of the BBA (EPA 2014).
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Importance of the Region's Ecological Resources
Although it is difficult to quantify the true number of extinct Pacific salmon populations around the
North Pacific, estimates for the western United States (California, Oregon, Washington, and Idaho) range
from 106 to 406 populations (Nehlsen et al. 1991, Augerot 2005, Gustafson et al. 2007). Pacific salmon
are no longer found in 40 percent of their historical breeding ranges in the western United States, and
populations tend to be significantly reduced or dominated by hatchery fishes where they do remain
(NRC 1996). In contrast, Bristol Bay's salmon fisheries are robust and entirely wild, with no contribution
from hatchery fishes in the watershed (Section 3.1).
For example, 214 salmon and steelhead (anadromous Rainbow Trout) stocks were identified as facing
risk of extinction in the western United States; 76 of those stocks were from the Columbia River basin
alone (Nehlsen et al. 1991). In general, these losses have resulted from cumulative effects of habitat loss,
water quality degradation, climate change, overfishing, dams, and other factors (NRC 1996, Schindler et
al. 2010). Many watersheds that have historically supported large salmon runs, such as the Fraser River
in Canada, are affected by multiple types of urban and industrial development, resulting in habitat loss
and degradation and declines in salmon runs (O'Neal and Woody 2011, EPA 2014: Box 8-4). Species
with extended freshwater rearing periods—species such as Coho, Chinook, and Sockeye salmon—are
more likely to be extinct, endangered, or threatened than species that spend less time in freshwater
habitats (NRC 1996, Gustafson et al. 2007). No Pacific salmon populations from Alaska are known to
have gone extinct, although many show signs of population declines.
The status of Pacific salmon throughout the United States highlights the value of the Bristol Bay
watershed as a salmon sanctuary or refuge (Rahr et al. 1998, Pinsky et al. 2009). This value is likely to
increase under changing climate conditions, which pose a key challenge for Pacific salmon conservation
(Shanley and Albert 2014, Ebersole et al. 2020). Climate-associated changes in water temperature and
streamflow, resulting changes in spawning and rearing habitats, responses of salmon populations, and
the inherent uncertainties involved in predicting these relationships highlight the increasing importance
of maintaining and protecting areas currently supporting diverse and robust salmon habitats and
populations (Schindler et al. 2008, Anderson et al. 2015, Ebersole et al. 2020, Vynne et al. 2021).
The Bristol Bay watershed contains intact, connected, and heterogeneous habitats that extend from
headwaters to ocean with minimal influence of human development. These characteristics, combined
with the region's high Pacific salmon abundance and life-history diversity, make the Bristol Bay
watershed a significant resource of global conservation value (Pinsky et al. 2009).
3.4 Summary
Because of its climate, geology, hydrology, pristine environment, and other characteristics, the Bristol
Bay watershed is home to abundant, diverse, high-quality aquatic habitats. These streams, rivers,
wetlands, lakes, and ponds support world-class subsistence, commercial, and recreational fisheries for
multiple species of Pacific salmon, as well as numerous other fish species valued as subsistence and
recreational resources. Because the region's salmon resources have supported Alaska Native cultures in
the region for thousands of years and continue to support one of the last intact wild salmon-based
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Importance of the Region's Ecological Resources
cultures in the world (EPA 2014: Appendix D, Nesbitt and Moore 2016, USACE 2020a: Section 3.7), the
watershed also has global cultural significance.
The productivity and diversity of the watershed's aquatic habitats are closely tied to the productivity
and diversity of its wild fisheries, and waters of the SFK, NFK, and UTC watersheds are critical for
maintaining the integrity, productivity, and sustainability of the region's salmon and non-salmon fishery
resources. Aquatic habitats in the three watersheds are ideal for maintaining high levels of fish
production with clean, cold water, gravel substrates, and abundant areas of groundwater exchange
(upwelling and downwelling). These conditions create preferred salmon spawning habitat and provide
favorable conditions for egg incubation and survival and juvenile rearing, and Pacific salmon species and
life stages have been documented to occur, often in high numbers, throughout the three watersheds
(Figure 3-18). They also provide high-quality habitat for fishes, such as Rainbow Trout, Dolly Varden,
Arctic Grayling, and Northern Pike. Wetlands and other off-channel areas provide essential habitats that
protect young Coho Salmon and other resident and anadromous fish species, as well as provide
spawning areas for Northern Pike. All of these species move throughout the region's freshwater habitats
during their life cycles, and all are fished—commercially, for subsistence use, and recreationally—in
downstream waters. Thus, the intact headwater-to-larger river systems found in the SFK, NFK, and UTC
watersheds, with their associated wetlands, lakes, and ponds, help sustain the overall productivity of
these fishery areas.
Not only do the aquatic habitats of the SFK, NFK, and UTC watersheds directly provide habitat for
salmon and other fishes, they also provide critical support for downstream habitats. By contributing
water, organic matter, and macroinvertebrates to downstream systems, these headwater areas help
maintain downstream habitats and fuel their fish productivity. Together, these functions—direct
provision of high-quality habitat and indirect provision of other resources to downstream habitats—
help support the valuable fisheries of the Bristol Bay watershed.
This support is particularly important in terms of Coho, Chinook, and Sockeye salmon fisheries. Chinook
Salmon are the rarest of the North American Pacific salmon species and are a critical subsistence
resource, particularly along the Nushagak River. The SFK, NFK, and UTC watersheds are known to
support small, discrete populations of Sockeye Salmon that are genetically programmed to return to
specific, localized reaches or habitats to spawn. The current state of understanding surrounding Pacific
salmon genetic baselines in the region indicates that the watersheds also support small, discrete
populations of Coho Salmon and Chinook Salmon. This portfolio of multiple small populations, which
exists as a result of the region's habitat complexity, is essential for maintaining the genetic diversity, and
thus the stability and productivity, of the region's overall wild salmon stocks.
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Figure 3-18. Streams, rivers, lakes and documented salmon use in the South Fork Koktuli
River, North Fork Koktuli River, and Upper Talarik Creek watersheds near the Pebble deposit.
Species distributions are based on the Anadromous Waters Catalog (Giefer and Graziano 2022).
N
A
0
l_l
A
3
i 1 1 i 1
6
U
Miles
0
L_i
5
i i 1 i i
10
u
Kilometers
KVICHAK
lliamna Lake
NUSHAGAK
Chinook
Sockeye
Churn
NHD Streams and
Waterbodies
Pebble Deposit
South Fork Koktuli,
North Fork Koktuli, and
Upper Talarik Creek
Watersheds
Nushagak and Kvichak
Watersheds
Coho
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1
ECTION 4. BASIS FOR RECOMMENDED DETERMINATION
This section synthesizes the information EPA Region 10 considered in its evaluation of the 2020 Mine
Plan to determine if the proposed discharge of dredged or fill material would be likely to result in
unacceptable adverse effects on anadromous fishery areas (including spawning and breeding areas).
Section 4.1 presents a brief review of the Section 404(c) Standards. Section 4.2 provides the
unacceptability findings that support the recommended prohibition and recommended restriction
described in Section 5. Section 4.3 provides an overview of EPA Region 10's evaluation of the effects of
discharges associated with the 2020 Mine Plan under the relevant portions of the CWA Section
404(b)(1) Guidelines (40 CFR Part 230).
4.1 Section 404(c) Standards
The purpose of the CWA is to "restore and maintain the chemical, physical, and biological integrity of the
Nation's waters" (33 U.S.C. 1251(a)). The CWA sets several goals, including attainment and preservation
of "water quality which provides for the protection and propagation of fish, shellfish and wildlife" (33
U.S.C. 1251(a)(2)).
To this end, CWA Section 404(c) specifically authorizes EPA to exercise its discretion to act "whenever"
it determines that the discharge of dredged or fill material will have an unacceptable adverse effect on
specific aquatic resources. Section 404(c) provides the following:
The Administrator is authorized to prohibit the specification (including the withdrawal of
specification) of any defined area as a disposal site, and he is authorized to deny or restrict
the use of any defined area for specification (including the withdrawal of specification) as a
disposal site, whenever he determines, after notice and opportunity for public hearings, that
the discharge of such materials into such area will have an unacceptable adverse
effect on municipal water supplies, shellfish beds and fishery areas fincluding
spawning and breeding areas!. wildlife, or recreational areas. Before making such
determination, the Administrator shall consult with the Secretary. The Administrator shall
set forth in writing and make public his findings and his reasons for making any
determination under this subsection, [emphasis added]
Importantly, Section 404(c) specifically directs EPA to consider adverse effects from the discharge of
dredged or fill material to fishery areas, including spawning and breeding areas. As a scientific matter,
evaluating adverse effects to fishery areas involves consideration of numerous factors, including adverse
effects that discharges of dredged or fill material can directly have on aquatic areas where fish
occurrence has been documented, as well as the adverse effects such discharges can have on aquatic
areas that provide ecosystem functions and values that support fishery areas. Therefore, this section
includes discussion of these considerations.
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Section 404(c) does not define the term "unacceptable adverse effect." EPA's regulations at 40 CFR
231.2(e) define "unacceptable adverse effect" as follows:
[IJmpact on an aquatic or wetland ecosystem which is likely to result in significant
degradation of municipal water supplies (including surface or ground water) or significant
loss of or damage to fisheries, shellfishing, or wildlife habitat or recreation areas. In
evaluating the unacceptability of such impacts, consideration should be given to the relevant
portions of the Section 404(b)(1) Guidelines (40 CFR Part 230).45
The preamble to EPA's final rule promulgating 40 CFR Part 231 further explained that "[t]he term
'unacceptable' in EPA's view refers to the significance of the adverse effect" (44 FR 58076, 58078). EPA
also discussed that, for example, an unacceptable adverse effect "is a large impact" and "one that the
aquatic and wetland ecosystem cannot afford" (44 FR 58078).
EPA's determination of an "unacceptable adverse effect" necessarily involves a case-by-case
determination based on many factors, including the unique characteristics of the aquatic resource that
would be affected by discharges of dredged or fill material. EPA's preamble to the Section 404(c)
regulations explained that "[b]ecause 404(c) determinations are by their nature based on predictions of
future impacts, what is required is a reasonable likelihood that unacceptable adverse effects will occur -
not absolute certainty but more than mere guesswork" (44 FR 58078). As discussed in Section 3, the
Bristol Bay watershed is an outstanding global resource, providing pristine, intact, connected aquatic
habitats from headwaters to ocean. These aquatic habitats provide extensive spawning and rearing
areas for and support genetically diverse populations of wild salmon. Like the larger Bristol Bay
watershed, the SFK, NFK, and UTC watersheds also contain pristine, intact aquatic habitats that provide
extensive spawning and rearing areas for and support genetically diverse populations of wild salmon.
The EPA Region 10 Regional Administrator has prepared this recommended determination because he
has determined that unacceptable adverse effects on fishery areas would be likely to result from the
discharge of dredged or fill material into waters of the United States for the construction and routine
operation of the 2020 Mine Plan. These effects are described in detail in Section 4.2.
4.2 Effects on Fishery Areas from Discharges of Dredged or
Fill Material from Developing the Pebble Deposit
Development of the 2020 Mine Plan would require the discharge of dredged or fill material into waters
of the United States at the mine site (PLP 2020b, USACE 2020a, USACE 2020b). As discussed in the FEIS
for the 2020 Mine Plan, "no other wild salmon fishery in the world exists in conjunction with an active
mine of this size" (USACE 2020a: Page 4.6-9). This section considers both the direct and secondary
effects of such discharges on fishery areas. Direct effects are impacts on aquatic resources associated
45 The language referring to "municipal water supplies, shellfish beds and fishery areas (including spawning and
breeding areas), wildlife, or recreational areas" in Section 404(c) of the CWA is synonymous with the references in
40 CFR 231.2 to "municipal water supplies (including surface or ground water)" and "fisheries, shellfishing, or
wildlife habitat or recreation areas."
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Section 4
Basis for Recommended Determination
with the discharge (actual placement) of dredged or fill material into waters of the United States. Direct
adverse effects of the 2020 Mine Plan would include elimination of streams and other aquatic resources
within the footprints of the mine site components (e.g., TSFs, WMPs, stockpiles, and the open pit).
Secondary effects are associated with the discharge of dredged or fill material, but do not result from
actual placement of this material (40 CFR 230.11(h)(1)). Secondary effects "are an important
consideration in evaluating the acceptability of a discharge site" under the Section 404(b)(1) Guidelines
(45 FR 85343).
Direct and secondary (indirect) effects evaluated in the FEIS include the following (USACE 2020a:
Section 4.22.3):
• Direct effects from:
o Clearing and removal of vegetation
o Excavation or removal of soil and vegetation
o Placement of fill materials
o Dredging and discharges of dredged materials
o Alteration and removal of stream channels
• Secondary effects from:
o Fragmentation of aquatic resources
o Fugitive dust
o Downstream habitat degradation
o Dewatering
The direct and secondary effects of the discharge of dredged or fill material for the construction and
routine operation of the 2020 Mine Plan include both the permanent loss of certain aquatic resources
and the degradation of additional aquatic resources. For the purposes of this recommended
determination, aquatic resource losses can result from elimination, dewatering, and fragmentation (Box
4-1 and Box 4-2).
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M
Secondary effects are associated with the discharge of dredged or fill material, but do not result from actual
placement of this material (40 CFR 230.11(h)(1)). Severity of these secondary effects depends on factors
such as the type of aquatic resource being impacted, the type of impact, and the duration of the impact.
When sufficiently severe, these secondary effects of the discharge of dredged or fill material can result in
the loss of aquatic resources. For example, in certain circumstances, secondary effects such as habitat
fragmentation and dewateringcan result in aquatic resource losses.
Fragmentation of streams, wetlands, and other waters results when development divides a formerly
continuous aquatic resource into smaller, more isolated remnants. Effects of fragmentation on streams,
wetlands, and other waters are wide-ranging and depend on several factors, including the nature of the
development; the size, shape, and complexity of the remnants; the hydrogeomorphology and community
composition of the affected habitat; and the needs and mobility of fish and wildlife species that depend on
the affected habitats. Decreased connectivity of aquatic ecosystems could preclude the completion of
aquatic organisms' life cycles; for example, fragmentation could prevent anadromous fishes from reaching
spawning grounds or accessing off-channel habitat (USACE 2020a: Section 4.22). For anadromous fishes,
the most severe form of fragmentation occurs when discontinuities are created that either separate an
aquatic habitat (stream, wetland, lake, pond) or complex of aquatic habitats from the tributary network in
such a way that precludes use (e.g., spawning, rearing, feeding, migration, overwintering) by anadromous
fish species and life stages documented to occur in the habitat or eliminate the movement of water or
dissolved or suspended materials to downstream anadromous fish streams. This type of fragmentation
represents a loss for anadromous fishes when it persists for 5 or more years, because such a time period
reflects the typical life cycle of the anadromous fishes discussed in this recommended determination (Brazil
and West 2016).
Dewatering of streams, wetlands, and other aquatic resources causes the alteration or loss of hydrology and
may result in the conversion of habitat to more mesic types. Under the 2020 Mine Plan, groundwater
drawdown can extend beyond half of a mile in some areas, but is expected primarily around the open pit
from dewatering activities, as well as around quarries, TSFs, and WMPs from diversions and
drainage/underdrain systems. Altered saturated surface flow and shallow interflow resulting from a
depression of the groundwater table are expected to permanently affect area wetlands, surface waters, and
vegetation. The severity of impact will depend on a number of factors, including aquatic resource type,
hydrogeomorphology, and community composition (USACE 2020a: Section 4.22). For anadromous fishes,
the most severe effects of dewatering for each aquatic resource type are as follows.
• For documented anadromous waters, removing sufficient flow to eliminate access to or use of habitat for
the species and life stages documented to occur in the reach in question,
• For additional streams, removing sufficient flow to eliminate the downstream movement of water or
dissolved or suspended materials,
• For ponds or lakes, reducing the spatial extent of the pond or lake, and
• For wetlands, changing the hydrologic regime such that the wetland no longer exhibits wetland hydrology,
as defined in the Corps of Engineers Wetland Delineation Manual (USACE 1987).
These effects of dewatering represent a loss for anadromous fishes when they persist for 5 or more years,
because such a time period reflects the typical life cycle of the anadromous fishes discussed in this
recommended determination (Brazil and West 2016).
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Section 4
Basis for Recommended Determination
The following definitions are provided to clarify key terms in this recommended determination.
4iV:uJroinc>!s rbhes hatch in freshwater habitats, migrate to sea for a period of relatively rapid growth, and
then return to freshwater habitats to spawn. For the purposes of this recommended determination,
"anadromous fishes" refers to Coho or Silver salmon (Oncorhynchus kisutch), Chinook or King salmon (0.
tshawytscha), Sockeye or Red salmon (0. nerka), Chum or Dog salmon (0. keta), and Pink or Humpback
salmon (0. gorbuscha). For these five species of Pacific salmon, the majority of surviving adults return to
their natal freshwater habitats to spawn. This homing behavior fosters reproductive isolation, thereby
enabling populations to adapt to the specific environmental conditions of their natal habitats (Section
3.3.3). Each of these species is semelparous: adults die after spawning a single time (representing a single
opportunity to pass on their genes), thereby depositing the nutrients incorporated in their body mass into
their spawning and rearing habitats (Section 3.3.4).
Poeum
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Section 4
Basis for Recommended Determination
Section 4.2 considers the following impacts from the discharge of dredged or fill material for the
construction and routine operation of the 2020 Mine Plan:
• The loss of approximately 8.5 miles (13.7 km) of documented anadromous fish streams46 (Section
4.2.1).
• The loss of approximately 91 miles (147 km) of additional streams that support anadromous fish
streams (Section 4.2.2).47
• The loss of approximately 2,108 acres (8.5 km2) of wetlands and other waters that support
anadromous fish streams (Section 4.2.3).48
• Adverse impacts on approximately 29 additional miles (46.7 km) of documented anadromous fish
streams resulting from greater than 20 percent changes in average monthly streamflow (Section
4.2.4).
Sections 4.2.1 through 4.2.4 describe the basis for EPA Region 10's determination that each of these
losses or streamflow changes would be likely to, independently, result in unacceptable adverse effects
on anadromous fishery areas (including spawning and breeding areas) in the SFK and NFK watersheds.
Because the 2020 Mine Plan represents only one configuration of a potential mine to develop the Pebble
deposit,49 Sections 4.2.1 through 4.2.4 also evaluate the adverse effects of these levels of loss and
streamflow changes anywhere in the SFK, NFK, and UTC watersheds. These watersheds share several
similarities in characteristics and aquatic resources, including similarities in the types and abundance of
aquatic habitats, their general physical and chemical characteristics, and the organisms that use those
habitats (Box 3-1). As discussed in Sections 4.2.1 through 4.2.4, these similarities provide support for
EPA Region 10's determination that these levels of loss and streamflow changes anywhere in the SFK,
NFK, and UTC watersheds also would be likely to result in unacceptable adverse effects on anadromous
fishery areas in these watersheds.
4.2.1 Adverse Effects of Loss of Anadromous Fish Streams
EPA Region 10 has determined that the discharge of dredged or fill material for the construction and
routine operation of the 2020 Mine Plan, resulting in the loss of approximately 8.5 miles (13.7 km) of
anadromous fish streams, would be likely to have unacceptable adverse effects on anadromous fishery
areas in the NFK watershed. As discussed in Section 4.2.1, this conclusion is based on the permanent loss
46 For the purposes of this recommended determination, anadromous fishery areas include anadromous fish
streams.
47 This value has been rounded in this recommended determination to address differences in rounding of stream
length information in different parts of the FEIS.
48 This value changed from the proposed determination to reflect losses of wetlands and other waters in only the
SFK and NFK watersheds, which are the focus of Section 4.2.3.
49 Given current mining technology and the high density of water resources in the area, the discharge of dredged or
fill material is expected to be necessary to develop the Pebble deposit.
Recommended Determination
4-6
December 2022
-------
Section 4
Basis for Recommended Determination
of anadromous fish streams50 and the permanent loss of ecological subsidies these anadromous fish
streams provide to downstream waters.
4,2.1,1 Anadromous Fish Streams That Would Be Permanently Lost at the Mine Site
The streams at the mine site for the 2020 Mine Plan were evaluated in detail and several were found to
provide habitat for anadromous fishes (Figure 4-1). Discharges of dredged or fill material associated
with the 2020 Mine Plan would result in the permanent loss of approximately 8.5 miles (13.7 km) of
streams with documented anadromous fish occurrence, specifically occurrence of Coho and Chinook
salmon (Table 4-1, Figure 4-2) (PLP 2020b, USACE 2020a: Section 4.24, Giefer and Graziano 2022). The
loss of all 8.5 miles (13.7 km) would be confined to the NFK watershed, specifically to Tributary NFK
1.190, Tributary NFK 1.200, and their sub-tributaries (Figure 4-2). The loss of 8.5 miles (13.7 km) of
anadromous fish streams represents approximately 13 percent of the anadromous fish streams in the
NFK watershed (USACE 2020a: Section 4.24, Giefer and Graziano 2022). The FEIS indicates additional
anadromous fish streams at the mine site (Figure 4-1) would be impacted by construction and operation
activities, but permanent losses were only expected in 8.5 miles of these anadromous fish streams
(USACE 2020a: Section 4.24).
NFK 1.190
325-30-10100-2202-3080-4083-5215
4.2
NFK 1.190.10
325-30-10100-2202-3080-4083-5215-6001
1.7
NFK 1.190.10.03
325-30-10100-2202-3080-4083-5215-6001-7012
0.05
NFK 1.190.30
325-30-10100-2202-3080-4083-5215-6006
0.5
NFK 1.190.40
325-30-10100-2202-3080-4083-5215-6007
0.9
NFK 1.200
325-30-10100-2202-3080-4083-5217
1.1
TOTAL
8.5
Sources:
a = Giefer and Graziano 2022.
b = USACE 2022.
50 These permanent losses are the result of streams filled or otherwise eliminated for the construction of various
mine components and from streams that would no longer be accessible to fish due to mine site infrastructure (i.e.,
fragmentation).
Recommended Determination
December 2022
4-7
-------
Section 4
Basis for Recommended Determination
Figure 4-1. Mine site area fish distribution. Figure 4.24-1 from the FEIS (USAGE 2020a: Section 4.24).
Sources:PLP 2019-RFI153; USGS;
ADF&G AWC & AFFI; PLP (R2 et al. 2011)
US Army Corps
of Engineers
Fish Distribution Alternative 1a
Anadromous Salmonids Monitoring Wells
Resident (non-anadromous) Salmonids — — Natural Gas Pipeline
Non-Salmonid Fish Only Mine Site Footprint
No Fish Observed
¦ Stream Crossing
Other Features
Perennial/Intermittent Streams
Lake/Pond
*** Watershed
100' Contour (Existing)
MINE SITE AREA
FISH DISTRIBUTION
PEBBLE PROJECT EIS
FIGURE 4.24-1
Recommended Determination
4-8
December 2022
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North
Frying Pa„ Lake
Section 4
Basis for Recommended Determination
Figure 4-2. Streams, rivers, and lakes with documented salmon use overlain with the Pebble
2020 Mine Plan. Anadromous streams lost are the streams identified as lost in the FEIS and are
listed in Table 4-1 (USACE 2022). Species distributions are based on the Anadromous Waters
Catalog (Giefer and Graziano 2022).
— Coho
— Chinook
• Sockeye
* Chum
Anadromous Streams
Lost
NHD Streams and
Waterbodies
2020 Mine Footprint
South Fork Koktuii,
I North Fork Koktuii, and
Upper Taiarik Creek
Watersheds
N
A
0
1 1
1
i i i i i
2
i 1
Miles
0
11 1
1.5
i i I ii i
3
i 1
Kilometers
Recommended Determination
4-9
December 2022
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Section 4
Basis for Recommended Determination
The discharge of dredged or fill material from the 2020 Mine Plan would permanently eliminate at least
7.1 miles (11.4 km) of Coho Salmon habitat and 3.7 miles (6.0 km) of Chinook Salmon habitat
(Table 4-2) (Giefer and Graziano 2022).51 Most of these losses would occur where the bulk TSF would be
built (Figure 4-1) (USACE 2020a: Section 4.24). Construction of the bulk TSF alone would permanently
eliminate 5.6 miles (9.1 km) of anadromous fish streams in Tributaries NFK 1.190, NFK 1.190.30, and
NFK 1.190.40 (USACE 2022). These three anadromous fish streams provide at least 4.8 miles (7.7 km) of
rearing habitat and 3.7 miles (6.0 km) of spawning habitat for Coho Salmon and at least 1.4 miles
(3.4 km) of rearing habitat and 0.8 mile of migrating habitat for Chinook Salmon (Giefer and Graziano
2022). Construction of other mine site components, including the main WMP (Figure 4-1), would result
in the remaining documented anadromous fish stream losses in Tributaries NFK 1.190.10, NFK
1.190.10.03, and NFK 1.200 (Figure 4-2).
Length of Anadromous Habitat (mites)
Species Rearing Spawning Present I TOTAL *
. .... . _. ._ . . _ . .... .. — _ _.
Coho Salmon
7.1
3.7
-
7.1
Chinook Salmon
2.3
-
1.4
3.7
Notes:
a Coho and Chinook salmon habitat overlap, and rearing and spawning habitat overlap, so individual values cannot be added together. The totals
represent the total extent of habitat to be lost for each species of Coho and Chinook salmon.
Tributary NFK 1.190 and its sub-tributaries have been documented to provide Coho Salmon spawning
habitat, and rearing juvenile salmon have been observed in Tributaries NFK 1.190 and NFK 1.200
(USACE 2020a: Section 4.24). Rearing juvenile Chinook Salmon have been documented to occur in
Tributary NFK 1.200 (USACE 2020a: Section 4.24). Chinook Salmon rear in the third-order
beaver-modified stream that the baulk TSF would eliminate (i.e., Tributary NFK 1.190), along with
0.5 mile (0.8 km) of Tributary NFK 1.190.30 (Figure 4-2) (Giefer and Graziano 2022).52
Other anadromous fish streams at the mine site (see Figure 4-1) are a part of the same hydrologically
connected network of headwater streams as the 8.5 miles of anadromous fish streams that would be
eliminated by the 2020 Mine Plan footprint (Section 3.2; EPA 2015; USACE 2020a: Sections 3.16, 3.17, and
3.22); support the same anadromous fish species and life stages (Section 3.3; USACE 2020a: Section 3.24);
and are a part of the same headwater stream network characterized in the evaluation of the 2020 Mine
Plan (Figures ES-5, 4-1, 4-2, and 4-8).
51 Coho Salmon are documented to occur in 7.1 miles (11.4 km) of the 8.5 miles (13.7 km) of lost anadromous fish
streams and Chinook Salmon are documented to occur in 3.7 miles (6.0 km) of the 8.5 miles (13.7 km) of lost
anadromous fish streams (Table 4.2).
52 Fish surveys have documented juvenile Coho Salmon in a short (260-foot) reach at the downstream end of this
tributary, NFK 1.190.30 (Giefer and Graziano 2022).
Recommended Determination
4-10
December 2022
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Section 4
Basis for Recommended Determination
4,2.1,2 Adverse Effects from Permanent Losses of Anadromous Fish Streams at the
Mine Site
The 8.5 miles (13.7 km) of permanent anadromous stream losses would result in fish displacement,
injury, and mortality. In addition to the permanent removal of streamflow and subsequent effects on fish
migration, "fisheries, invertebrate, and riparian habitat and productivity would be permanently
removed" from lost streams (USACE 2020a: Pages 4.24-3 and 4.24-4).
The permanent loss of 8.5 miles (13.7 km) of anadromous fish streams from a single project is
unprecedented in the context of the CWA Section 404 regulatory program in Alaska. These streams
would be completely eliminated and, thus, would permanently lose the ability to support salmon. Coho
Salmon would lose at least 7.1 miles (11.4 km) of habitat as a direct result of discharges of dredged or fill
material associated with the 2020 Mine Plan, which amounts to more than 11 percent of documented
Coho Salmon habitat in the NFK watershed (Table 3-6). Habitat losses for Chinook Salmon would be 8.7
percent of documented habitat in the NFK watershed. As discussed below, the loss of 8.5 miles (13.7 km)
of anadromous fish streams would be likely to result in long-term adverse effects on salmon populations
in the NFK watershed.
The anadromous fish streams that the discharge of dredged or fill material associated with the 2020
Mine Plan would permanently eliminate are ecologically valuable, particularly for juvenile salmon
(Section 3.2.4). Tributary NFK 1.190 is interconnected with ponds and seasonally to permanently
inundated wetlands that result from beaver activity (USFWS 2 0 21).53 These features provide excellent
rearing habitat and important overwintering and flow velocity refugia for salmonids (Section 3.2.4)
(Nickelson et al. 1992, Cunjak 1996, Collen and Gibson 2001, Lang et al. 2006). The permanent loss of
anadromous fish streams resulting from the discharges of dredged or fill material associated with the
2020 Mine Plan would also result in the loss of salmon spawning habitat, which would, in turn, result in
the loss of marine-derived nutrients those fish would have contributed upon death. Given the naturally
low nutrient concentrations in these streams, the inputs of marine-derived nutrients may be especially
important in supporting biological production and, thus, food for juvenile salmonids in these and
downstream habitats (Section 3.3.4). These streams also support biological production via inputs of leaf
litter from deciduous shrubs and grasses in riparian areas (Meyer et al. 2007, Dekar et al. 2012), which
help fuel the production of macroinvertebrates, a key food for salmonids (Table 3-3). Thus, the
anadromous fish streams that the 2020 Mine Plan would eliminate, as well as similar habitats in the SFK,
NFK, and UTC watersheds, play an essential role in the successful completion of the life cycle of salmon.
These anadromous fish stream losses alone would be significant, but the effects of these losses would be
compounded by the fact that such losses would affect Coho and Chinook salmon populations that are
uniquely adapted to the physical and chemical environmental conditions of their natal streams (i.e.,
stream of birth, see Section 3.3.1). Adaptation to local environmental conditions results in discrete,
genetically distinct salmonid populations. This biocomplexity—operating across a continuum of
53 Connection to such floodplain wetland and pond habitats can greatly enhance the carrying capacity and
productive potential of anadromous fish streams (Section 3).
Recommended Determination
4-11
December 2022
-------
Section 4
Basis for Recommended Determination
integrated, nested spatial and temporal scales—depends on the abundance and diversity of aquatic
habitats in the area and acts to stabilize overall salmon production and fishery resources (Section 3.3.3)
(Schindler et al. 2010, Schindler et al. 2018, Brennan et al. 2019). As discussed below, the substantial
spatial and temporal extent of anadromous fish stream losses resulting from the discharge of dredged or
fill material associated with the 2020 Mine Plan suggest that these losses would reduce the overall
reproductive capacity and productivity of Coho and Chinook salmon in the entire NFK watershed.
Pacific salmon exhibit high fidelity to their natal spawning and rearing environments resulting in genetic
variation among discrete populations (Quinn 2018). The existence of discrete, genetically distinct
salmon populations has been well-documented in the Bristol Bay watershed (Olsen et al. 2003, Ramstad
et al. 2010, Quinn et al. 2012, Dann et al. 2012, Shedd et al. 2016, Brennan et al. 2019, Raborn and Link
2022). Both the Koktuli River (including the SFK and NFK) and UTC are known to support genetically
distinct populations of Sockeye Salmon (Dann et al. 2012, Shedd et al. 2016, Dann et al. 2018). Research
has shown that these distinct populations can occur at very fine geographic scales (Section 3.3.3). For
example, Sockeye Salmon populations in close proximity to each other show phenotypic variations
related to differences in spawning habitats (ecotypes) (Ramstad et al. 2010), and Sockeye Salmon that
use spring-fed ponds and streams as close as approximately 0.6 mile (1 km) apart exhibit differences in
traits (e.g., spawn timing and productivity) that suggest they may comprise discrete populations (Quinn
et al. 2012).
Research on the presence of genetically distinct populations of Coho and Chinook salmon in Alaska is
ongoing. Existing evidence suggests that local adaptation and fine-scale population structure likely exist
for these species as well (Olsen et al. 2003, Sethi and Tanner 2014, Clark et al. 20 1 5).54 Similar patterns
of genetic variation among species (across a landscape) emphasize the vital importance that landscape
heterogeneity (i.e., habitat complexity across the intact ecosystem) plays in determining genetic
structure (Ackerman et al. 2013).
Coho and Chinook salmon are the two rarest of North America's five species of Pacific salmon (Healey
1991, Woody 2018) and are particularly vulnerable to losses of small, discrete populations. As a result,
these species may be especially vulnerable to habitat losses resulting from the 2020 Mine Plan. Coho and
Chinook salmon have the greatest number of population extinctions among the five species of Pacific
salmon (Nehlsen et al. 1991, Augerot 2005). Many of the patterns of population extinction relate to
longer periods of their life history spent rearing in freshwater, making them more vulnerable to
freshwater habitat loss and degradation. For example, Chinook Salmon populations that rear for 1 or
more years in freshwater—the dominant type in the Bristol Bay watershed (Healey 1991)—have a
higher rate of extinction than populations that migrate to sea within their first year of life (Gustafson et
al. 2007).
54 Advances in genomics and other techniques are allowing detection of genetic structure at increasingly fine
scales; as methods to evaluate these genetic differences improve, researchers are uncovering more fine-scaled
population structure in many salmon species (Meek etal. 2020).
Recommended Determination
4-12
December 2022
-------
Section 4
Basis for Recommended Determination
Alaska Coho Salmon populations are generally small, isolated, and likely exhibit local adaptation to
different spawning and freshwater rearing habitats (Olsen et al. 2003). They occupy a wide array of
freshwater habitat types, with many populations occupying small first- and second-order headwater
streams with limited spawning and juvenile rearing habitat (Sandercock 1991, McCracken 2021). Small
genetically diverse populations of Coho Salmon represent reproductively isolated populations innately
adapted to their spawning and rearing habitats (Dittman and Quinn 1996, Olsen et al. 2003, Peterson et
al. 2014, Bett and Hinch 2016, McCracken 2021). The loss of these habitats would threaten the long-
term fitness of these locally adapted populations (Olsen et al. 2003, Mobley et al. 2019). ADF&G has
developed a genetic baseline for Coho Salmon for Cook Inlet, but genetic baselines have not been
completed elsewhere in Alaska due to a lack of representative samples. In the Cook Inlet watersheds, the
most genetically divergent populations are generally those farthest upstream and those from the most
southern portion of Cook Inlet (Barclay and Habicht 2019).
Olsen et al. (2003) summarize the implications of Coho Salmon population structuring at fine geographic
scales for conservation of the species:
Fishery management and conservation actions affecting coho salmon in Alaska must
recognize that the genetic population structure of coho salmon occurs on a fine geographic
scale. Activities or conditions that cause declines in population abundance are more likely to
have strong negative impacts for coho than for species in which genetic variation is
distributed over a broader geographic scale (e.g., chum salmon). Coho salmon are probably
more susceptible to extirpation, less likely to be augmented or "rescued" by other
populations through straying (gene flow), and the loss of populations means loss of
significant amounts of overall genetic variability. These risks underscore the
importance of single populations to the long term viability of coho salmon in Alaska
and justify managing and conserving coho salmon at a fine geographic scale. (Page
568) [emphasis added]
Chinook Salmon populations also tend to be relatively small (Healey 1991) and exhibit a diversity of life
history traits (e.g., variations in size and age at migration, duration of freshwater and estuarine
residency, time of ocean entry) (Lindley et al. 2009). Chinook Salmon populations in the Togiak River
exhibit differences in spawning habitats (mainstem versus tributary) and migration timing, which
translate to a clear stock structure (Sethi and Tanner 2014, Clark et al. 2015). Patterns of genetic
differentiation between upstream and downstream populations along the same river network have also
been found for other salmonids (Olsen et al. 2011, Ackerman et al. 2013, Barclay and Habicht 2019,
Miettinen et al. 2021). Chinook Salmon populations in western Alaska similarly show fine-scale
population differences across the four major regions (Norton Sound, the Yukon River, the Kuskokwim
River, and Bristol Bay). This finding supports the contention that discrete Chinook Salmon populations
likely exist in this region, which includes the Koktuli River (Larson et al. 2014, McKinney et al. 2020).
Brennan et al. (2019) provide further support for this contention, demonstrating that the relative
productivity of different portions of the Nushagak River varies over relatively short (1- to 4-year) time
frames for both Chinook and Sockeye salmon.
Because Coho and Chinook salmon spend longer periods of time rearing in the freshwater streams that
would be permanently eliminated by the discharge of dredged or fill material associated with the 2020
Recommended Determination
4-13
December 2022
-------
Section 4
Basis for Recommended Determination
Mine Plan, these species are more susceptible to losses of what are likely small, discrete populations.
The importance of maintaining the diversity among populations (e.g., in terms of migration timing, other
life history traits, and genetic composition) for long-term population persistence and sustainability has
been well-documented (Moore et al. 2014, Schindler et al. 2010, Brennan et al. 2019, Davis and
Schindler 2021). Loss of any genetically distinct populations in the SFK and NFK watersheds would
constitute a measurable adverse effect, in addition to any effects these losses may have at the scale of the
entire Bristol Bay watershed via the portfolio effect (Section 3.3.3).
Thus, the permanent loss of 8.5 miles (13.7 km) of anadromous fish streams represents a significant loss of
habitat itself and would reduce both habitat complexity and biocomplexity in the NFK watershed, thereby
contributing to the unacceptable adverse effects resulting from the loss of anadromous fish streams. In
addition, biocomplexity at relatively localized geographic scales contributes to the resilience and
persistence of downstream populations. Biocomplexity, operating across a continuum of nested spatial
and temporal scales, acts to buffer salmon populations from sudden and extreme changes in abundance,
thereby maintaining overall salmon productivity (Section 3.3.3). Brennan et al. (2019: Page 785)
underscore the critical role that streams and other aquatic habitats across the entire Nushagak River
watershed, including those that would be adversely affected by the 2020 Mine Plan, play in stabilizing the
Nushagak River's productive Sockeye and Chinook salmon fisheries, concluding that "[ultimately, entire
landscapes are involved in stabilizing biological production."
4,2.1,3 Adverse Effects from Permanent Losses of Ecological Subsidies to
Anadromous Fish Streams Downstream of the Mine Site
The permanent destruction of 8.5 miles of anadromous fish streams would also adversely affect
downstream habitat for salmon. The following downstream secondary effects would result from the loss
of these anadromous fish streams: reduced primary production, reduced nutrient cycling, reduced or
lost gravel recruitment, reduced terrestrial inputs, and altered water chemistry (USACE 2020a:
Section 4.24). These impacts "would be certain to occur if the project is permitted and constructed"
(USACE 2020a: Page 4.24-9).
Coho, Chinook, and Sockeye salmon spawn and Coho and Chinook salmon rear in stream reaches
immediately downstream of the 8.5 miles (13.7 km) of anadromous fish streams that would be
permanently lost under the 2020 Mine Plan (Figures 3-5 through 3-7). These downstream spawning and
rearing areas would be deprived of the ecological subsidies provided by the 8.5 miles (13.7 km) of
anadromous fish streams that would be destroyed.
Because of their crucial influence on downstream water flow, chemistry, and biota, impacts on
headwaters reverberate throughout entire watersheds (Freeman et al. 2007, Meyer et al. 2007, Colvin et
al. 2019, Koenig et al. 2019, French et al. 2020). As described in Section 3.2.4, headwater streams such as
the 8.5 miles (13.7 km) of anadromous fish streams that would be permanently lost are important
sources of water, nutrients, organic material, macroinvertebrates, and algae for habitats lower in the
watersheds, and thereby provide important year-round subsidies for juvenile salmonids in those lower
watershed habitats (Figures 4-3 and 4-4) (Vannote et al. 1980, Wipfli and Gregovich 2002, Meyer et al.
2007, Wipfli et al. 2007, Colvin et al. 2019). For example, Alexander et al. (2007) found that perennial
Recommended Determination
4-14
December 2022
-------
Section 4
Basis for Recommended Determination
headwaters have a significant influence on downstream water quality and quantity, contributing
roughly 55 percent of mean annual water volume and 40 percent of nitrogen flux in fourth and higher-
order streams and rivers. This example highlights the critical role that headwaters play in determining
the structure and function of larger downstream areas (Section 3.2.4). Where they provide salmon
spawning areas, the anadromous fish streams that would be permanently lost are also a source of
marine-derived nutrients for downstream waters (Section 3.3.4). Thus, elimination of these spawning
areas would reduce the downstream transport of these marine-derived energy subsidies.
Permanent loss of approximately 8.5 miles (13.7 km) of anadromous fish streams due to discharges of
dredged or fill material associated with the 2020 Mine Plan would also fundamentally alter surface
water and groundwater hydrology and, in turn, the flow regimes of receiving—or formerly receiving—
streams. Such alterations would reduce the extent and frequency of stream connectivity to off-channel
habitats, as well as reduce groundwater inputs and their modifying influence on the thermal regimes of
downstream habitats, including spawning, rearing and overwintering areas (Section 4.2.4). Lost streams
also would no longer support or export macroinvertebrates, which are a critical food source for juvenile
salmon, resident salmonids, and other organisms associated with the riparian zone.
This degradation of downstream salmon habitats in the NFK watershed and the resulting effects on
salmon populations that rely on those habitats would erode both the habitat complexity and
biocomplexity that help buffer these populations from sudden and extreme changes in abundance and
ultimately maintains their productivity (Section 4.2.1.2).
4,2.1,4 Impacts on Other Fish Species
Although this recommended determination is based solely on adverse effects on anadromous fishery
areas, EPA Region 10 notes that the 8.5 miles (13.7 km) of anadromous fish streams that would be lost
under the 2020 Mine Plan also provide habitat for non-anadromous fish species. The assemblage of
non-anadromous fishes found in and supported by these anadromous fish streams is an important
component of these habitats and further underscores the biological integrity and ecological value of
these pristine, intact headwater networks.
Based on currently available fish survey data (ADF&G 2022a), the anadromous fish streams that would
be permanently eliminated support three non-anadromous salmonid species (Rainbow Trout, Dolly
Varden, and Arctic Grayling) and one other resident fish species (Slimy Sculpin) (Figures 4-4 through
4-7). Rainbow Trout, Dolly Varden, and Arctic Grayling are targets of downstream subsistence and
recreational fisheries. Slimy Sculpin support those fisheries as forage fish (Section 3.3.1). The three
non-anadromous salmonid species likely migrate substantial distances (120 miles [200 km] to 200 miles
[320 km]) within their freshwater habitats (Section 3.3.1), suggesting that individuals move between
headwaters and downstream areas. Most of the individuals observed in fish surveys in the 2020 Mine
Plan footprint area were juvenile or sub-adults (ADF&G 2022a), further supporting that fishes rearing in
headwater tributaries may contribute to downstream harvests.
Recommended Determination
4-15
December 2022
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Section 4
Basis for Recommended Determination
Figure 4-3. Streams, rivers, and lakes with documented salmon use in the South Fork Koktuli
River, North Fork Koktuli River, and Upper Talarik Creek watersheds, downstream of the
Pebble 2020 Mine Plan. Species distributions are based on the Anadromous Waters Catalog
(Giefer and Graziano 2022).
Coho
Chinook
Sockeye
Chum
Pink
¦
2020 Mine Footprint
~
South Fork Koktuli,
North Fork Koktuli, and
Upper Talarik Creek
Watersheds
¦=>
Nushagak and Kvichak
Watersheds
N
A
0
|_J
3
i i 1 ii n
6
_|
Miles
0
l_i
5
i i II « i
10
i_l
Kilometers
KVICHAK
Hiarnna Lake
NUSHAGAK
Recommended Determination
4-16
December 2022
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Section 4
Basis for Recommended Determination
Figure 4-4. Reported occurrence of Arctic Grayling, Rainbow Trout, and Dolly Varden in the
South Fork Koktuli River, North Fork Koktuli River, and Upper Talarik Creek watersheds, down-
stream of the Pebble 2020 Mine Plan. Species distributions are based on the Alaska Freshwater
Fish Inventory (ADF&G 2022a).
NUSHAGAK
ler la&rik ^eek
South Fork Koktuli
KVICHAK
0
A
O
~
Arctic Grayling
Rainbow Trout
Dolly Varden
2020 Mine Footprint
South Fork Koktuli,
North Fork Koktuli, and
Upper Talarik Creek
Watersheds
Nushagakand Kvichak
River Watersheds
lliamna Lake
| Nushagak W-]
/ 6
A f Kvichak
N
A
0
u
3
i i. 1 i ii
6
U
Miles
0
1
5
n ii 1 i i
10
l_l
Kilometers
Recommended Determination
4-17
December 2022
-------
Section 4
Basis for Recommended Determination
Figure 4-5. Reported occurrence of other resident fish species in the South Fork Koktuli River,
North Fork Koktuli River, and Upper Talarik Creek watersheds, downstream of the Pebble 2020
Mine Plan, Species distributions are based on the Alaska Freshwater Fish Inventory (ADF&G
2022a).
Nctfth Fork Koktbli
Upper Talarik^reek
South Fork Koktuli
0
Northern Pike
0
Stickleback
o
Sculpin
2020 Mine Footprint
South Fork Koktuli,
i i
North Fork Koktuli, and
i i
Upper Talarik Creek
Watersheds
P-,
Nushagak and Kvichak
Watersheds
N
~
0
i_i
A
3
0 1 1 1 1
6
_|
Miles
0
1_]
5
i i l ii
10
i_!
Kilometers
NUSHAGAK
KVICHAK
Uiamna Lake
Recommended Determination
4-18
December 2022
-------
Section 4
Basis for Recommended Determination
Figure 4-6. Reported occurrence of Arctic Grayling, Rainbow Trout, and Dolly Varden overlain
with the Pebble 2020 Mine Plan, Species distributions are based on the Alaska Freshwater Fish
inventory (ADF&G 2022a).
0 Arctic Grayling
A Rainbow Trout
O Dolly Varden
NHD Streams and
Waterbodies
2020 Mine Footprint
South Fork Koktuli,
North Fork Koktuli, and
Upper Talarik Creek
Watersheds
Nushagak and Kvichak
River Watersheds
'
I I I i I I I I I
Miles
l i i 1 i
Kilometers
Recommended Determination
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Section 4
Basis for Recommended Determination
Figure 4-7. Reported occurrence of other resident fish species overlain with the Pebble 2020
Mine Plan. Species distributions are based on the Alaska Freshwater Fish Inventory (ADF&G
2022a).
0 Northern Pike
° Stickleback
o Sculpin
NHD Streams and
Waterbodies
2020 Mine Footprint
South Fork Koktuli,
1 North Fork Koktuli, and
Upper Talarik Creek
Watersheds
Nushagak and Kvichak
Watersheds
0 1 2
Li—J a I i i I
Miles
0 2 4
1 f 1 1 1 l I I !
Kilometers
•$> Q ~ '
Recommended Determination
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Section 4
Basis for Recommended Determination
4,2.1,5 Conclusions
EPA Region 10 has considered and evaluated the information available regarding how the loss of
approximately 8.5 miles (13.7 km) of anadromous fish streams from the discharge of dredged or fill
material associated with mining the Pebble deposit would affect anadromous fishery areas in the SFK,
NFK, and UTC watersheds. As described below, the loss of approximately 8.5 miles (13.7 km) of
anadromous fish streams from such discharges would be likely to result in unacceptable adverse effects
on anadromous fishery areas if the losses are located at the mine site or elsewhere in the SFK, NFK, and
UTC watersheds. The following conclusions and rationale directly support the recommended prohibition
described in Section 5.1 and the recommended restriction described in Section 5.2.
4.2.1.5.1 Adverse Effects of the Loss of Anadromous Fish Streams at the Mine Site
EPA Region 10 has determined that the discharge of dredged or fill material for the construction and
routine operation of the 2020 Mine Plan, resulting in the loss of approximately 8.5 miles (13.7 km) of
anadromous fish streams, would be likely to have unacceptable adverse effects on anadromous fishery
areas in the NFK watershed. This conclusion is based on the following factors: the large amount of
permanent loss of anadromous fish habitat (including spawning and breeding areas); the particular
importance of the permanently lost habitat for juvenile Coho and Chinook salmon; the degradation of
additional downstream spawning and rearing habitat for Coho, Chinook, and Sockeye salmon due to the
loss of ecological subsidies provided by the eliminated anadromous fish streams; and the resulting erosion
of habitat complexity and biocomplexity within the NFK watershed, both of which are key to the
abundance and stability of salmon populations within this watershed. Other anadromous fish streams at
the mine site are a part of the same hydrologically connected network of headwater streams as the 8.5
miles of anadromous fish streams that would be eliminated by the 2020 Mine Plan footprint (Section 3.2;
EPA 2015; USACE 2020a: Sections 3.16, 3.17, and 3.22); support the same anadromous fish species and life
stages (Section 3.3; USACE 2020a: Section 3.24); and are a part of the same headwater stream network
characterized in the evaluation of the 2020 Mine Plan (Figures ES-5, 4-1, 4-2, and 4-8). Thus, the same or
greater levels of loss of these anadromous fish streams from discharges of dredged or fill material
associated with developing the Pebble deposit anywhere at the mine site also would be likely to have
unacceptable adverse effects on anadromous fishery areas. These conclusions support the recommended
prohibition described in Section 5.1.
4.2.1.5.2 Adverse Effects of the Loss of Anadromous Fish Streams Elsewhere in
the SFK, NFK, and UTC Watersheds
The 2020 Mine Plan represents only one configuration of a potential mine at the Pebble deposit. Mine
infrastructure could also be placed at other locations in the SFK, NFK, and UTC watersheds. The FEIS
considers the environmental impacts of discharges of dredged or fill material to construct components
associated with mining the Pebble deposit (e.g., TSFs) at other locations in these three watersheds
(Section 2.1.2.2). For example, the FEIS indicates that placement of a bulk TSF with the necessary
capacity in other locations in the SFK, NFK, or UTC watersheds would result in similar or greater losses
of documented anadromous fish streams than the bulk TSF location proposed in the 2020 Mine Plan
Recommended Determination
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Basis for Recommended Determination
(PLP 2018e: RFI 098). Coho, Chinook, Sockeye, and Chum salmon have been documented to rely on
habitat throughout the SFK, NFK, and UTC watersheds (Section 3.3.2.2). Because anadromous fish
streams directly support critical life history stages (e.g., spawning, rearing, migration) of at least one
anadromous fish species, relocating losses of anadromous fish streams from the NFK watershed to the
SFK or UTC watersheds would result in similar adverse effects on anadromous fishery areas. Thus, this
recommended determination also considers the loss of approximately 8.5 miles of anadromous fish
streams in the context of the SFK, NFK, and UTC watersheds.
The SFK, NFK, and UTC watersheds share several similarities in characteristics and aquatic resources.
The three watersheds are of similar size and share a headwater location. The broad components of these
watersheds are similar in terms of the types and abundance of aquatic habitats, their general physical
and chemical characteristics, and the organisms that use those habitats (Box 3-1). Additionally, in each
of the three watersheds, these components combine in different ways to create unique habitat mosaics,
which over thousands of years have resulted in local adaptation of anadromous fish populations to site-
specific conditions in each watershed. As a result, loss or degradation of anadromous fish streams in any
of the three watersheds would result in similar effects on anadromous fishery areas (e.g., elimination of
spawning and rearing habitat, elimination of downstream ecological subsidies, erosion of habitat
complexity and biocomplexity).
Given the similarity of the aquatic resources across the three watersheds and the expected impacts of
discharges of dredged or fill material associated with developing the Pebble deposit, EPA Region 10 has
determined that the discharge of dredged or fill material associated with mining the Pebble deposit
anywhere in the SFK, NFK, and UTC watersheds, resulting in the loss of approximately 8.5 miles (13.7
km) of anadromous fish streams, would be likely to have unacceptable adverse effects on anadromous
fishery areas in these watersheds. This conclusion is based on the same record and analysis used to
evaluate the effects of the 2020 Mine Plan and the following factors: the presence of anadromous fish
streams throughout the SFK, NFK, and UTC watersheds, which directly support critical life history stages
(e.g., spawning, rearing, migration) of at least one anadromous fish species (Section 3.3); anadromous
fish streams throughout these watersheds that are currently among the least developed and least
disturbed (i.e., closest to pristine) habitat of this type in North America (Section 3.1); that these three
watersheds have similar amounts of total anadromous fish streams, as well as similar amounts of
anadromous fish streams for each of the five Pacific salmon species (Table 3-6, Figure 3-18); that
anadromous fish streams across these three watersheds function similarly to support multiple species
and life stages of anadromous fishes that are adapted to the unique set of environmental conditions each
stream provides (Section 3.3); the large amount of permanent loss of anadromous fish habitat; the
degradation of additional downstream anadromous fish habitat due to the loss of ecological subsidies
provided by the eliminated anadromous fish streams; and the resulting erosion of habitat complexity
and biocomplexity within the SFK, NFK, and UTC watersheds, both of which are key to the abundance
and stability of salmon populations within these watersheds. This conclusion supports the
recommended restriction described in Section 5.2.
Recommended Determination
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Section 4
Basis for Recommended Determination
4.2.2 Adverse Effects of Loss of Additional Streams that Support
Anadromous Fish Streams
In addition to the permanent loss of approximately 8.5 miles (13.7 km) of documented anadromous fish
streams, discharges of dredged or fill material at the mine site under the 2020 Mine Plan would result in
the permanent loss of an additional approximately 91 miles (147 km)55 of streams that support
anadromous fish streams56 in the SFK and NFK watersheds (USACE 2020a: Section 4.24) (Figure 4-8,
Box 4-3). EPA Region 10 has determined that the permanent loss of these additional streams would be
likely to have unacceptable adverse effects on anadromous fishery areas in the SFK and NFK
watersheds. As discussed in this section, this conclusion is based on the extensive permanent loss of
additional streams that support anadromous fish streams and the corresponding permanent loss of
ecological subsidies these additional streams provide to downstream anadromous fish streams.
The streams at the mine site (Figures 4-8 and ES-5) were analyzed in detail to identify "all aquatic
habitats potentially directly or indirectly affected by permitted mine site activities" (USACE 2020a: Page
4.24-1). The FEIS identifies 99.7 miles of streambed habitat at the mine site that would be lost under the
2020 Mine Plan, which includes the 8.5 miles of anadromous fish stream losses discussed in Section
4.2.1 (USACE 2020a: Section 4.24). Most of these losses would be located in the NFK watershed, where
72.4 miles (116.5 km) of additional streams would be permanently lost in addition to the entire 8.5
miles [13.7 km] of anadromous fish stream losses. Permanent additional stream losses in the SFK and
UTC watersheds would be 18.8 miles (30.3 km) and 0.02 mile (0.02 km), respectively (PLP 2020b). The
FEIS indicates the combined 99.7 miles (160.5 km) of anadromous fish stream and additional stream
losses would represent "about 20 percent of available [stream] habitat in the Headwaters Koktuli River
[watershed]" (i.e., the SFK, NFK, and Middle Koktuli River HUC-12 watersheds) and "12 percent of
available [stream] habitat in the larger Koktuli River [watershed]" (USACE 2020a: Page 4.24-8).57
This permanent loss of additional streams from discharges of dredged or fill material for the
construction and routine operation of the 2020 Mine Plan would result in reduced stream productivity
in downstream anadromous fishery areas of the SFK and NFK due to the loss of physical and biological
inputs that would no longer be provided to downstream fishery areas that support Coho, Chinook,
Sockeye, and Chum salmon. These impacts would be permanent and certain to occur (USACE 2020a:
Section 4.24).
55 According to the FEIS, "[a] total of 80 miles of stream habitat would be eliminated in the NFK drainage, including
8.5 miles of anadromous Pacific salmon habitat" and "a total of 19 miles of stream habitat would be
eliminated in the SFK drainage" (USACE 2020a: Page 4.24-9). According to PLP's June 2020 CWA Section 404
permit application, additional stream losses in the UTC would be less than 0.02 mile (PLP 2020b).
56 Streams that support anadromous fish streams refers to streams that do not currently have documented
anadromous fish occurrence. As explained in this section, such streams support downstream anadromous fish
streams. Although there is not currently documented anadromous fish occurrence in these streams, they may
nonetheless be used by anadromous fish; however, the potential for such use is not a basis for this recommended
determination (see Box 4-2 and Appendix B).
57 EPA Region 10 acknowledges that water resources have not been consistently mapped across these watersheds
(USACE 2020a: Page 4.24-8). Nonetheless, the 2020 Mine Plan would result in the permanent loss of nearly 100
miles of headwater streams, which is the focus of Sections 4.2.1 and 4.2.2.
Recommended Determination
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Section 4
Basis for Recommended Determination
Figure 4-8. Streams, wetlands, and ponds lost under the Pebble 2020 Mine Plan. Streams, wetlands, and ponds at the
mine site are based on PLP's June 2020 Permit Application (PLP 2020b).
Wetlands Lost (PLP)
Ponds Lost (PLP)
2020 Mine Footprint
South Fork Koktuli,
North Fork Koktuli, and
Upper Talarik Creek
Watersheds
Intermittent Streams
(PLP)
Perennial Streams (PLP)
Anadromous Streams
Lost
Waterbody (NHD)
A
0 1 2
1 s 1 1 1 1 1 1 1
Miles
0 1.5 3
II—i—J 1—I—i I I I
Kilometers
Recommended Determination
4-24
December 2022
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Section 4
Basis for Recommended Determination
I
_
As shown in Figure 4-8, PLP completed field-verified mapping of wetlands and other waters at the mine site.
This type of higher resolution stream and wetland mapping would be necessary to accurately predict
impacts on water resources from the discharge of dredged or fill material for the purposes of any final
determination in this case. Project-specific map layers provide more detail and include more water courses
than publicly available stream and wetland databases. A brief review of these datasets is provided to
demonstrate how the water resource impacts described in the FEIS and this recommended determination
differ from the typical stream and wetland mapping available for the rest of the SFK, NFK, and UTC
watersheds.
National stream and wetland datasets are readily accessible for these watersheds, but these data come
with limitations. The U.S. Geological Survey provides a nationwide database of streams, waterbodies, and
watersheds as part of the National Hydrography Dataset (NHD). The NHD is a feature-based database that
identifies stream segments or reaches that make up the nation's surface water drainage system. These data
are mapped at 1:63,360 scale or larger in Alaska (USGS 2022). Similarly, the U.S. Fish and Wildlife Service
maintains the National Wetlands Inventory (NWI) to provide information on the status, extent,
characteristics, and functions of the nation's wetlands, riparian, and deepwater habitats (USFWS 2022a).
The NWI mapping available for the SFK, NFK, and UTC watersheds is derived from 1:65,000 scale aerial
photography (USFWS 2021). While NWI is not available nationwide, it is currently available for approximately
96 percent of the SFK, NFK, and UTC watersheds.
The stream and wetland mapping generated by PLP was developed using more site-specific information
than is typically used in the development of NHD or NWI. For approximately 44 percent of the SFK, NFK, and
UTC watershed areas, PLP developed high resolution vegetation and stream mapping layers using a
combination of field data collection and aerial photography interpretation. Wetland boundaries were
digitized on aerial photography at a scale between 1:1,200 and 1:1,500. Waterbodies were digitized based
on aerial photography scaled at 1:400 using an average minimum mapping unit of 0.05 acre (USACE
2020a: Section 3.22). This mapping addressed some data gaps that otherwise exist when using non-
project-specific stream and wetland mapping layers like NHD or NWI.
A comparison of these stream and wetland mapping sources helps demonstrate how impacts on water
resources can appear to vary due solely to changes in map resolution. EPA Region 10 understands the area
under the 2020 Mine Plan footprint was subject to more review by USACE during the CWA Section 404
permit review process. Therefore, this area is assumed to provide the most accurate comparison area of
national datasets to higher resolution water resources maps. While the NHD only shows approximately 25.8
miles (41.5 km) of streams under the 2020 Mine Plan footprint (USGS 2021b), PLP identified 99.7 miles
(160.5 km) of stream habitat that would be impacted in this same area, includingthe 8.5 miles (13.7 km) of
stream documented to contain anadromous fish (USACE 2020a: Section 4.24). These values indicate there
may be almost four times as many streams in these headwater areas than are mapped in the NHD. As
indicated in the FEIS, PLP's identification of additional small-scale watercourses resulted in an increase in
stream miles expected to receive direct and indirect impacts in the mine site analysis areas than had been
disclosed in the DEIS (USACE 2020a: Section 4.22).
Similarly, while PLP's CWA Section 404 application identified 2,113 acres (8.6 km2) of wetlands and other
waters that would be permanently lost due to the discharge of dredged or fill material at the mine site, NWI
identified only 1,492 acres (6.0 km2) of wetlands and deepwater habitats in this same area. These values
indicate that there may be over 40 percent more wetlands and other deepwater habitats in the vicinity of the
Pebble deposit compared to NWI.
Recommended Determination
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December 2022
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Section 4
Basis for Recommended Determination
The majority of the additional streams that would be permanently lost are small headwater streams. An
extensive body of scientific evidence demonstrates that headwater streams are important aquatic
habitats and play a critical role in the structure and function of downstream reaches (Section 3.2.4). The
small size and large collective surface area of headwater streams result in a disproportionate effect on
larger downstream habitats (Vannote et al. 1980, Alexander et al. 2007, Koenig et al. 2019, Colvin et al.
2019). Thus, loss of these headwater streams and their important ecological subsidies (e.g., food
resources, nutrients, surface water flows, groundwater exchange) can have larger than expected impacts
on downstream reaches. Headwater streams that the 2020 Mine Plan would eliminate contribute
spawning gravels, invertebrate drift, organic matter, nutrients, surface water flows, groundwater flows,
and woody debris to downstream channels (USACE 2020a: Section 4.24). The loss of the temperature
moderation via groundwater-influenced flows to downstream anadromous fish streams would
exacerbate the potentially substantial changes in stream temperature caused by WTP discharges
(USACE 2020a: Section 4.24). Headwater streams also can serve as refugia for fishes that may seasonally
or periodically use these habitats (USACE 2020a: Section 3.24). For example, headwater streams can
provide refuge from predators (Sepulveda et al. 2013), floods (Brown and Hartman 1988), or otherwise
temporarily inhospitable conditions in downstream waters. Indeed, the capacity and tendency of
juvenile salmonids to move extensively within the stream system, including upstream movements of
kilometers, is becoming increasingly apparent (e.g., Coho Salmon: Kahler et al. 2001; Anderson et al.
2013; Armstrong and Schindler 2013; reviewed by Shrimpton et al. 2014).
The 91 miles (147 km) of additional streams that would be permanently lost in the SFK and NFK
watersheds under the 2020 Mine Plan provide important provisioning functions (via ecological
subsidies) and habitat functions (via refugia) that are beneficial for downstream anadromous fishery
areas. As a result, headwater streams such as those that would be permanently lost at the mine site play
a vital role in maintaining diverse, abundant anadromous fish populations (Section 3.2.4). Losses of this
magnitude would degrade downstream anadromous fishery areas that provide spawning and rearing
habitat for Coho, Chinook, Sockeye, and Chum salmon in the SFK and NFK watersheds (Figures 3-5
through 3-8, Figures 4-2 and 4-3). These losses would adversely affect genetically distinct populations of
Sockeye Salmon in the Koktuli River (including the SFK and NFK), as well as Coho and Chinook salmon
populations that may be uniquely adapted to the spatial and temporal conditions of their natal streams
(Section 3.3.1).
As explained for the loss of 8.5 miles (13.7 km) of anadromous fish streams, the loss and degradation of
downstream anadromous fishery areas in the SFK and NFK watersheds that would result from
elimination of 91 miles (147 km) of additional streams would further erode habitat complexity and
biocomplexity within these watersheds. This diversity of salmon habitats and associated salmon
population diversity helps buffer these salmon populations from sudden and extreme changes in
abundance and ultimately maintain their stability and productivity. By itself, without contemplation of
any other certain losses, the permanent destruction of approximately 91 miles (147 km) of additional
streams from a single project would be unprecedented for the CWA Section 404 regulatory program in
the Bristol Bay watershed. Such losses are unprecedented for good reason: the effects of these additional
Recommended Determination
4-26
December 2022
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Section 4
Basis for Recommended Determination
stream losses would propagate to downstream habitats and adversely affect species such as Coho,
Chinook, Sockeye, and Chum salmon in the SFK and NFK watersheds, all of which support important
subsistence, commercial, and recreational fisheries.
Other streams at the mine site are a part of the same hydrologically connected network of headwater
streams as the 91 miles of additional streams that would be eliminated by the 2020 Mine Plan footprint
(Section 3.2; EPA 2015; USACE 2020a: Sections 3.16, 3.17, and 3.22); support the same anadromous fish
species and life stages (Section 3.3; USACE 2020a: Section 3.24); and are a part of the same headwater
stream network characterized in the evaluation of the 2020 Mine Plan (Figures ES-5, 4-1, 4-2, and 4-8).
4.2.2.1 Impacts on Other Fish Species
Although this recommended determination is based solely on adverse effects on anadromous fishery
areas, EPA Region 10 notes that the 91 miles (147 km) of additional streams that support anadromous
fishery areas in the SFK and NFK watersheds and would be lost under the 2020 Mine Plan also provide
habitat for non-anadromous fish species. The assemblage of non-anadromous fishes found in and
supported by these additional streams is an important component of these habitats and further
underscores the biological integrity and ecological value of these pristine, intact headwater networks.
The permanent loss of approximately 91 miles (147 km) of additional streams from the discharge of
dredged or fill material under the 2020 Mine Plan would adversely affect non-anadromous fish species
and assemblages. Available data indicate that approximately 14.1 miles (22.7 km) of these 91 miles (147
km) of additional streams support non-anadromous fish species such as Rainbow Trout, Dolly Varden,
Arctic Grayling, Ninespine Stickleback, and Slimy Sculpin (Figures 4-6 and 4-7). Approximately 1.4 miles
(2.3 km) of streams in the SFK watershed that would be lost at the mine footprint (Figure 4-8; USACE
2020a: Section 4.24) provide habitat for Arctic Grayling, Northern Pike, Slimy Sculpin, and Ninespine
Stickleback. The remaining 12.7 miles (20.4 km) that would be permanently lost are located in the NFK
watershed (USACE 2020a: Section 4.24) and provide habitat for Dolly Varden, Rainbow Trout, and Slimy
Sculpin (ADF&G 2022a). As described in Section 4.2.1, Rainbow Trout, Dolly Varden, and Arctic Grayling
are targets of downstream subsistence and recreational fisheries. Stickleback and Slimy Sculpin support
those fisheries as forage fishes (Table 3-3).
As discussed previously in this section, waters downstream of the mine site would be degraded as a
result of the elimination of 91 miles (147 km) of additional streams at the mine site. In addition to the
four Pacific salmon species already discussed, these waters support Rainbow Trout, Dolly Varden, Arctic
Grayling, Northern Pike, Ninespine Stickleback, and Slimly Sculpin. Thus, the ecological value of the
approximately 91 miles (147 km) of additional streams that would be eliminated is further highlighted
by the fact that they provide both habitat and habitat support functions for six non-anadromous fish
species important to subsistence and recreational fisheries and aquatic food webs (Section 3.3.1).
4.2.2.2 Conclusions
EPA Region 10 has considered and evaluated the information available regarding how the loss of
approximately 91 miles (147 km) of additional streams that support anadromous fish streams from the
Recommended Determination
4-27
December 2022
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Section 4
Basis for Recommended Determination
discharge of dredged or fill material associated with mining the Pebble deposit would affect anadromous
fishery areas in the SFK, NFK, and UTC watersheds. As described below, the loss of approximately 91
miles (147 km) of additional streams that support anadromous fish streams from such discharges would
be likely to result in unacceptable adverse effects on anadromous fishery areas if they are located at the
mine site or elsewhere in the SFK, NFK, and UTC watersheds. The following conclusions and rationale
directly support the recommended prohibition described in Section 5.1 and the recommended restriction
described in Section 5.2.
4.2.2.2.1 Adverse Effects of Loss of Additional Streams at the Mine Site that
Support Anadromous Fish Streams
EPA Region 10 has determined that the discharge of dredged or fill material for the construction and
routine operation of the 2020 Mine Plan, resulting in the loss of approximately 91 miles (147 km) of
additional streams, would be likely to have unacceptable adverse effects on anadromous fishery areas in
the SFK and NFK watersheds. This conclusion is based on the following factors: the large amount of
permanent loss of additional streams and the crucial role that these headwater streams play in
providing ecological subsidies to downstream anadromous fish streams; the degradation of downstream
anadromous fish streams, including spawning and rearing habitat for Coho, Chinook, Sockeye, and Chum
salmon, due to the loss of ecological subsidies provided by the eliminated headwater streams; and the
resulting erosion of habitat complexity and biocomplexity within the SFK and NFK watersheds, both of
which are key to the abundance and stability of salmon populations within these watersheds. Other
streams at the mine site are a part of the same hydrologically connected network of headwater streams
as the 91 miles of additional streams that would be eliminated by the 2020 Mine Plan footprint (Section
3.2; EPA 2015; USACE 2020a: Sections 3.16, 3.17, and 3.22); support the same anadromous fish species
and life stages (Section 3.3; USACE 2020a: Section 3.24); and are a part of the same headwater stream
network characterized in the evaluation of the 2020 Mine Plan (Figures ES-5, 4-1, 4-2, and 4-8). Thus,
the same or greater levels of loss of these additional streams from discharges of dredged or fill material
associated with developing the Pebble deposit anywhere at the mine site also would be likely to have
unacceptable adverse effects on anadromous fishery areas. These conclusions support the
recommended prohibition described in Section 5.1.
4.2.2.2.2 Adverse Effects of Loss of Additional Streams Elsewhere in the SFK, NFK,
and UTC Watersheds that Support Anadromous Fish Streams
The 2020 Mine Plan represents only one configuration of a potential mine at the Pebble deposit. Mine
infrastructure could also be placed at other locations in the SFK, NFK, and UTC watersheds. The FEIS
considers the environmental impacts of discharges of dredged or fill material to construct components
associated with mining the Pebble deposit (e.g., TSFs) at other locations in these three watersheds
(Section 2.1.2.2). For example, the FEIS indicates that placement of a bulk TSF with the necessary
capacity in other locations in the SFK, NFK, or UTC watersheds would result in similar or greater losses
of documented anadromous fish streams than the bulk TSF location proposed in the 2020 Mine Plan
(PLP 2018e: RFI 098). Coho, Chinook, Sockeye, and Chum salmon have been documented to rely on
habitat throughout the SFK, NFK, and UTC watersheds (Section 3.3.2.2). Because headwater streams—
Recommended Determination
4-28
December 2022
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Section 4
Basis for Recommended Determination
like the 91 miles of additional streams that would be lost as a result of the discharges associated with
the 2020 Mine Plan—directly support downstream anadromous fish streams (e.g., by providing habitat
and ecological subsidies, including spawning gravels, invertebrate drift, organic matter, nutrients,
surface water flows, groundwater flows, and woody debris), relocating losses of additional streams from
the NFK watershed to the SFK or UTC watersheds would result in similar adverse effects on anadromous
fishery areas. Thus, this recommended determination also considers the loss of approximately 91 miles
of additional streams that support anadromous fish streams in the context of the SFK, NFK, and UTC
watersheds.
The SFK, NFK, and UTC watersheds share several similarities in characteristics and aquatic resources.
The three watersheds are of similar size and share a headwater location. The broad components of these
watersheds are similar in terms of the types and abundance of aquatic habitats, their general physical
and chemical characteristics, and the organisms that use those habitats (Box 3-1). Additionally, in each
of the three watersheds, these components combine in different ways to create unique habitat mosaics,
which over thousands of years have resulted in local adaptation of anadromous fish populations to site-
specific conditions within each watershed. As a result, loss or degradation of additional streams that
support anadromous fish streams in any of the three watersheds would result in similar effects on
anadromous fishery areas (e.g., elimination of habitat, degradation of additional habitat downstream
due to elimination of ecological subsidies, erosion of habitat complexity and biocomplexity).
Given the similarity of the aquatic resources across the three watersheds and the expected impacts of
discharges of dredged or fill material associated with developing the Pebble deposit, EPA Region 10 has
determined that the discharge of dredged or fill material associated with mining the Pebble deposit
anywhere in the SFK, NFK, and UTC watersheds, resulting in the loss of approximately 91 miles (147
km) of additional streams, would be likely to have unacceptable adverse effects on anadromous fishery
areas in these watersheds. This conclusion is based on the same record and analysis used to evaluate the
effects of the 2020 Mine Plan and the following factors: headwater streams throughout the SFK, NFK,
and UTC watersheds that are currently among the least developed and least disturbed (i.e., closest to
pristine) habitat of this type in North America (Section 3.1) and play an important role in supporting
Pacific salmon populations (Section 3.2); that these three watersheds have similar amounts of total
stream miles (relative to their watershed areas) (Table 3-6); that headwater streams across these three
watersheds function similarly to support productive fishery areas for anadromous fishes (Section 3.3);
the large amount of outright loss of stream habitat and the crucial role that these headwater streams
play in providing ecological subsidies to downstream anadromous fish streams; the degradation of
downstream anadromous fish streams from the loss of ecological subsidies provided by the lost
headwater streams; and the resulting erosion of habitat complexity and biocomplexity within the SFK,
NFK, and UTC watersheds, both of which are key to the abundance and stability of salmon populations
within these watersheds. This conclusion supports the recommended restriction described in Section
5.2.
Recommended Determination
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December 2022
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Section 4
Basis for Recommended Determination
4.2.3 Adverse Effects of Loss of Wetlands and Other Waters that
Support Anadromous Fish Streams
In addition to the losses of anadromous fish streams and additional streams that support anadromous
fish streams, the discharge of dredged or fill material for the construction and routine operation of the
2020 Mine Plan would also result in the permanent loss of approximately 2,113 acres (8.6 km2) of
wetlands and other waters at the mine site; approximately 2,108 acres (8.5 km2) of these losses would
occur in the SFK and NFK watersheds (Figure 4-8, Table 4-3, see also Box 4-3) (USACE 2020a, USACE
2020b). EPA Region 10 has determined that these permanent losses of wetlands and other waters would
be likely to have unacceptable adverse effects on anadromous fishery areas in the SFK and NFK
watersheds. As discussed in this section, this conclusion is based on the extensive permanent loss of
wetlands and other waters and the corresponding permanent loss of ecological subsidies these wetlands
provide to downstream anadromous fish streams.
The FEIS evaluates the "potential direct and indirect impacts from construction and operations" of the
2020 Mine Plan on wetlands and other waters across the mine site (Figure ES-5) (USACE 2020a: Page
4.22-1). Wetlands and other waters that would be permanently lost play a critically important role in
the life cycles of anadromous fishes in the SFK and NFK watersheds (Section 3.2.3) (PLP 2011: Appendix
15.1.D), given that "...all wetlands are important to the greater function and value of ecosystems and
subsistence cultures they support" (USACE 2020a: Page 3.22-8). In addition, the wetlands and other
waters affected by the 2020 Mine Plan "possess unique ecological characteristics of productivity, habitat,
wildlife protection, and other important and easily disrupted values" (USACE 2020a: Page 3.22-1). The
specific wetlands and other waters that would be permanently lost are also relatively free from human-
induced alteration and provide extensive and heterogeneous habitats (Table 4-3) (USACE 2020a:
Section 3.22), and a diverse portfolio of pristine aquatic habitats is crucial to supporting the productivity
and stability of salmon populations in these watersheds (Section 3.3.3).
The permanent removal of wetlands and other waters would destroy habitat, result in mortality of
aquatic organisms, and reduce the collective functional capacity and value of wetlands and other waters
across multiple watersheds, as well as cause the displacement, injury, and/or mortality of species that
rely on these aquatic environments for all or part of their life cycles (USACE 2020a: Section 4.22). The
permanent "loss of wetlands from development of the mine site represent about 6 percent of mapped
wetlands in the Headwaters Koktuli River watershed" (USACE 2020a: Page 4.22-13)58 (i.e., the SFK, NFK,
and Middle Koktuli River HUC-12 watersheds) and 4 percent of mapped wetlands in the Headwaters
Koktuli River and UTC watersheds (Table 4-3, Box 4-3) (USACE 2020a: Section 4.22).
58 In its comments on the proposed determination, PLP indicated that following publication of the FEIS it provided
information to USACE that this value is 4.8 percent based on updated mapping results.
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Total Wetlands
1,909
4
1,913
Wetlands
Herbaceous
547
1
547
Deciduous Shrubs
1,352
3
1,355
SLOPE
Evergreen Shrubs
11
-
11
Total Other Waters
16
16
Other
Waters
Aquatic Bed
2
—
2
Ponds
13
-
13
TOTAL SLOPE
1,925
4
1,929
Total Wetlands
12
<1
12
Wetlands
Herbaceous
5
<1
5
DEPRESSIONAL
Deciduous Shrubs
7
-
7
Other
Total Other Waters
38
<1
39
Waters
Ponds
38
<1
39
TOTAL DEPRESSIONAL
50
<1
50
Total Wetlands
8
8
FLAT
Wetlands
Herbaceous
3
-
3
Deciduous Shrubs
6
-
6
TOTAL FLAT
8
8
LACUSTRINE
FRINGE
Wetlands
Total Wetlands
<1
<1
Herbaceous
<1
-
<1
TOTAL LACUSTRINE FRINGE
<1
<1
Total Wetlands
118
118
Wetlands
Herbaceous
42
-
42
RIVERINE
Deciduous Shrubs
76
-
76
Other
Total Other Waters
7
7
Waters
Ponds
7
-
7
TOTAL RIVERINE
125
125
Total Impacts to Wetlands (acres)
2,047
4
2,051
Total Impacts to Other Waters (acres)
610
<1
61°
Total Impacts to Wetlands and Other Waters (acres)
2,108 c
4
2,113e
Total Area of NWI Wetlands and Other Waters (acres)
36,458
13,193
49,651
Percent Total of NWI Wetlands and Other Waters
6
<1
4
Notes:
a 100 percent of the Headwaters Koktuli River watershed has been mapped in NWI.
b 91 percent of the Upper Talarik Creek watershed has been mapped in NWI.
c To be consistent with the USACE's ROD (USACE 2020b), stream area was removed from values presented in FEIS Table 4.22-3 such that the Other
Waters acres values only include the following NWI group types: aquatic bed and ponds (USACE 2022).
Source: Adapted from FEIS Table 4.22-3 (USACE 2020a).
The discharge of dredged or fill material into the wetlands and other waters described previously is
expected to reduce the biological productivity of wetland ecosystems by smothering, dewatering,
permanently flooding, or altering substrate elevation or the periodicity of water movement. The
decreased productivity and/or alteration of water current patterns and velocities could eliminate or
reduce the cycling of nutrients and compounds, and disruption of wetland hydrology can interfere with
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the filtration, aquifer recharge, and storm and floodwater modification functions of wetlands (USACE
2020a: Section 4.22). Many of the affected wetlands at the mine site, especially slope wetlands, are
considered headwater wetlands from a watershed perspective, meaning they are the primary source of
intermittent and upper perennial streams. Impacts to these wetlands could alter groundwater discharge
that maintains hydrology and water quality and buffers water temperatures in these streams; this
alteration of hydrologic function is likely to extend to wetlands and other waters immediately
downgradient from the affected wetlands (USACE 2020a: Section 4.22).
Changes in flow in the SFK, NFK, and UTC due to modification of upgradient wetlands and mine
operations have the potential to change the hydrologic connectivity of off-channel habitats and
associated wetlands (USACE 2020a: Section 4.22). Off-channel habitats, including fringing riparian
wetlands, provide cover important to juvenile salmon rearing (Section 3.2) (USACE 2020a: Section 4.22).
Changes to flow and loss of connectivity between wetlands and other waters and stream channels also
can affect nutrient availability, the downstream transport of invertebrates, and available habitat for
benthic macroinvertebrate production, thereby adversely affecting overall productivity of downgradient
anadromous fish streams and streams that support anadromous fish streams (USACE 2020a:
Section 4.22).
As described in Section 4.2.1, the wetlands and other waters that would be permanently removed due to
discharges of dredged or fill material associated with the 2020 Mine Plan include beaver ponds and
wetlands inundated as a result of beaver activity (USFWS 2021). Coho and Chinook salmon rear in many
of the beaver-modified waters or the streams they abut (Table 3-10). Beaver-modified waters provide
excellent rearing habitat and important overwintering and flow-velocity refugia for anadromous fishes
(Section 3.2.4) and may be especially important in maintaining salmon productivity (Nickelson et al.
1992, Solazzi et al. 2000, Pollock et al. 2004).
Wetlands that are contiguous with and adjacent to anadromous fish streams likely provide additional
anadromous fish habitat. Such areas often provide habitat to juveniles of species such as Coho Salmon
(Henning et al. 2006, EPA 2014: Appendix B). The lower gradient of lakes, ponds, and inundated
wetlands connected to anadromous fish streams also can provide beneficial rearing and foraging
conditions that may be unavailable in the main stream channel (Sommer et al. 2001, Henning et al.
2006), thereby increasing capacity for juvenile salmon growth and rearing (Nickelson et al. 1992,
Sommer et al. 2001).
Wetlands also indirectly support anadromous fish streams by providing cover; moderating stream
temperatures and flows; maintaining baseflows; serving as groundwater recharge zones; and supplying
nutrients, organic material, macroinvertebrates, algae, and other materials to abutting streams and
streams lower in the watershed. These inputs serve as important subsidies for juvenile salmonids
(Vannote et al. 1980, Wipfli and Gregovich 2002, Meyer et al. 2007, Dekar et al. 2012, Doretto et al.
2020). Abundant wetlands and small ponds, for example, have been documented to contribute
disproportionately to groundwater recharge in this region (Rains 2011). Given the importance of
groundwater-surface water exchange in the SFK, NFK, and UTC watersheds, groundwater inputs are
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likely a significant determinant of surface water quantity and quality. Moreover, leaf litter from
deciduous shrubs and herbaceous vegetation is an important source of food for stream food webs and
helps fuel the production of macroinvertebrates, a key food for juvenile salmonids (Table 3-3) (Meyer et
al. 2007, Dekar et al. 2012). Riparian wetlands with deciduous shrubs and grasses are prevalent in the
SFK, NFK, and UTC watersheds and likely provide this energy source to downgradient waters.
The permanent loss of approximately 2,108 acres (8.5 km2) of wetlands and other waters under the
2020 Mine Plan in the SFK and NFK watersheds would result in loss of habitat and the provision of key
ecological subsidies to both abutting and downstream waters (Section 3.2.4). These headwater wetlands
play a vital role in maintaining diverse, abundant anadromous fish populations, via the downgradient
transport of surface and groundwater inputs and food sources critical to the survival, growth, and
spawning success of downstream anadromous fishes (Section 3.2.4). The loss of such waters would
eliminate structurally complex and thermally and hydraulically diverse habitats—including crucial
overwintering areas—that are essential to rearing salmonids.
Downstream waters that would be degraded by the elimination of wetlands and other waters at the
mine site are ecologically important and provide rearing and spawning habitat for Coho, Chinook,
Sockeye, and Chum salmon in the SFK and NFK watersheds (Figures 3-5 through 3-8). In addition,
degradation of downstream anadromous fish streams would adversely affect genetically distinct
populations of Sockeye Salmon in the Koktuli River (including SFK and NFK) and Coho and Chinook
salmon populations that may be uniquely adapted to the spatial and temporal conditions of their natal
streams (Section 3.3.1).
As explained for the loss of 8.5 miles (13.7 km) of anadromous fish streams, the loss and degradation of
downstream anadromous fishery areas in the SFK and NFK watersheds that would result from
elimination of approximately 2,108 acres (8.5 km2) of wetlands and other waters would further erode
both habitat complexity and biocomplexity within the SFK and NFK watersheds. The diversity of salmon
habitats and associated salmon population diversity helps buffer these salmon populations from sudden
and extreme changes in abundance and ultimately maintain their stability and productivity. By itself,
without contemplation of any other certain losses, the permanent destruction of approximately 2,108
acres (8.5 km2) of wetlands and other waters from a single project would be unprecedented for the CWA
Section 404 regulatory program in the Bristol Bay watershed. Such losses are unprecedented for good
reason: the effects of these losses would propagate to downstream habitats and adversely affect species
such as Coho, Chinook, Sockeye, and Chum salmon in the SFK and NFK watersheds, all of which support
important subsistence, commercial, and recreational fisheries.
Additional wetlands and other waters at the mine site are hydrologically and ecologically connected to,
and in some cases abut, the 2,108 acres of wetlands and other waters that would be eliminated by the
2020 Mine Plan footprint (Section 3.2; EPA 2015; USACE 2020a: Sections 3.16, 3.17, and 3.22). These
wetland and other aquatic habitats support the same anadromous fish species and life stages (Section 3.3;
USACE 2020a: Section 3.24) and are a part of the same headwater wetland complex characterized in the
evaluation of the 2020 Mine Plan (Figure ES-5). Furthermore, the FEIS indicates wetlands and other
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waters adjacent to the mine site would also be degraded by construction and operation of the 2020 Mine
Plan. For example, fugitive dust was expected to be deposited up to 330 feet from mine site
infrastructure (USACE 2020a: Section 4.24), fragmentation would occur between mine site
infrastructure (Figure ES-5) (USACE 2020a: Section 4.22), and groundwater drawdown could
potentially dewater wetlands located more than half a mile from mine infrastructure (USACE 2020a:
Figure 4.22-3). Such indirect impacts also contribute adverse effects to anadromous fish streams due to
the impacts on water quality, loss of connections to habitat, and loss of ecological subsidies due to
vegetation changes. If these indirect impacts continue throughout the life of the mine, they also could
result in permanent losses of these types of water resources (Box 4-1).
4.2.3.1 Impacts on Other Fish Species
Although this recommended determination is based solely on adverse effects on anadromous fishery
areas, EPA Region 10 notes that the 2,108 acres (8.5 km2) of wetlands and other waters at the mine site
that would be lost in the SFK and NFK watersheds under the 2020 Mine Plan also provide habitat for
non-anadromous fish species. The assemblage of non-anadromous fishes found in and supported by
these wetlands and other waters is an important component of these habitats and further underscores
the biological integrity and ecological value of these pristine, intact headwater networks. Dolly Varden
and sculpin rear in many of the same beaver-modified habitats as Coho and Chinook salmon, and
Ninespine Stickleback and sculpin rear in headwater ponds of the SFK watershed (Figures 4-6 and 4-7).
Furthermore, waters downstream of the mine site that would be degraded by elimination of wetlands
and other waters at the mine site support Rainbow Trout, Dolly Varden, Arctic Grayling, Northern Pike,
Ninespine Stickleback, and sculpin—species that support regional biodiversity (Meyer et al. 2007) and
are important to subsistence and recreational fisheries and aquatic food webs (Section 3.3.1).
4.2.3.2 Conclusions
EPA Region 10 has considered and evaluated the information available regarding how the loss of
approximately 2,108 acres of wetlands and other waters from the discharge of dredged or fill material
associated with mining the Pebble deposit would affect anadromous fishery areas in the SFK, NFK, and
UTC watersheds. As described below, the loss of approximately 2,108 acres of wetlands and other waters
from such discharges would be likely to result in unacceptable adverse effects on anadromous fishery
areas if they are located at the mine site or elsewhere in the SFK, NFK, and UTC watersheds. The
following conclusions and rationale directly support the recommended prohibition described in Section
5.1 and the recommended restriction described in Section 5.2.
4,2,3,2,1 Adverse Effects of Loss of Wetlands and Other Waters at the Mine Site
that Support Anadromous Fish Streams
EPA Region 10 has determined that the discharge of dredged or fill material for the construction and
routine operation of the 2020 Mine Plan, resulting in the loss of approximately 2,108 acres (8.5 km2) of
wetlands and other waters, would be likely to have unacceptable adverse effects on anadromous fishery
areas in the SFK and NFK watersheds. This conclusion is based on the following factors: the large
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amount of outright loss of wetlands and other waters; the importance of wetlands and other waters to
salmon populations, both as habitat and as sources of groundwater inputs, nutrients, and other
subsidies important to salmon productivity in downstream waters; the degradation of downstream
anadromous fish streams, including spawning and rearing habitat for Coho, Chinook, Sockeye, and Chum
salmon, from the loss of ecological subsidies provided by the lost headwater wetlands and other waters;
and the resulting erosion of habitat complexity and biocomplexity within the SFK and NFK watersheds,
both of which are key to the abundance and stability of salmon populations within these watersheds.
Additional wetlands and other waters at the mine site are hydrologically and ecologically connected to,
and in some cases abut, the 2,108 acres of wetlands and other waters that would be eliminated by the
2020 Mine Plan footprint (Section 3.2; EPA 2015; USACE 2020a: Sections 3.16, 3.17, and 3.22). These
wetland and other aquatic habitats support the same anadromous fish species and life stages (Section 3.3;
USACE 2020a: Section 3.24) and are a part of the same headwater wetland complex characterized in the
evaluation of the 2020 Mine Plan (Figure ES-5). Thus, the same or greater levels of loss of these additional
wetlands and other waters from discharges of dredged or fill material associated with developing the
Pebble deposit anywhere at the mine site also would be likely to have unacceptable adverse effects on
anadromous fishery areas. These conclusions support the recommended prohibition described in Section
5.1.
4,2,3,2,2 Adverse Effects of Loss of Wetlands and Other Waters Elsewhere in the
SFK, NFK, and UTC Watersheds that Support Anadromous Fish Streams
The 2020 Mine Plan represents only one configuration of a potential mine at the Pebble deposit. Mine
infrastructure could also be placed at other locations in the SFK, NFK, and UTC watersheds. The FEIS
considers the environmental impacts of discharges of dredged or fill material to construct components
associated with mining the Pebble deposit (e.g., TSFs) at other locations in these three watersheds
(Section 2.1.2.2). For example, the FEIS indicates that placement of a bulk TSF with the necessary
capacity in other locations in the SFK, NFK, or UTC watersheds would result in similar or greater losses
of documented anadromous fish streams than the bulk TSF location proposed in the 2020 Mine Plan
(PLP 2018e: RFI 098). Coho, Chinook, Sockeye, and Chum salmon have been documented to rely on
habitat throughout the SFK, NFK, and UTC watersheds (Section 3.3.2.2). Because headwater wetlands,
like those that would be lost as a result of the discharges associated with the 2020 Mine Plan, directly
support downstream anadromous fish streams (e.g., by providing habitat; moderating stream
temperatures and flows; maintaining baseflows; serving as groundwater recharge zones; and supplying
ecological subsidies such as nutrients, organic material, macroinvertebrates, algae, and other materials
to abutting streams and streams lower in the watershed) relocating losses of wetlands and other waters
from the NFK watershed to the SFK or UTC watersheds would result in similar adverse effects on
anadromous fishery areas. Thus, this recommended determination also considers the loss of
approximately 2,108 acres of wetlands and other waters that support anadromous fish streams in the
context of the SFK, NFK, and UTC watersheds.
The SFK, NFK, and UTC watersheds share several similarities in characteristics and aquatic resources.
The three watersheds are of similar size and share a headwater location. The broad components of these
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watersheds are similar in terms of the types and abundance of aquatic habitats, their general physical
and chemical characteristics, and the organisms that use those habitats (Box 3-1). Additionally, in each
of the three watersheds, these components combine in different ways to create unique habitat mosaics,
which over thousands of years have resulted in local adaptation of anadromous fish populations to site-
specific conditions in each watershed. As a result, loss or degradation of wetlands and other waters that
support anadromous fish streams in any of the three watersheds would result in similar effects on
anadromous fishery areas (e.g., elimination of habitat, degradation of additional habitat downstream
due to elimination of ecological subsidies, erosion of habitat complexity and biocomplexity).
Given the similarity of the aquatic resources across the three watersheds and the expected impacts of
discharges of dredged or fill material associated with developing the Pebble deposit, EPA Region 10 has
determined that the discharge of dredged or fill material associated with mining the Pebble deposit
anywhere in the SFK, NFK, and UTC watersheds, resulting in the loss of approximately 2,108 acres (8.5
km2) of wetlands and other waters, would be likely to have unacceptable adverse effects on anadromous
fishery areas in these watersheds. This conclusion is based on the same record and analysis used to
evaluate the effects of the 2020 Mine Plan and the following factors: headwater wetlands and other
waters throughout the SFK, NFK, and UTC watersheds that are currently among the least developed and
least disturbed (i.e., closest to pristine) habitat of this type in North America (Section 3.1) and play an
important role in supporting Pacific salmon populations (Section 3.2); that these three watersheds have
similar amounts and types of wetlands (Table 3-2); that headwater wetlands and other waters across
these three watersheds function similarly to support productive fishery areas for anadromous fishes
(Section 3.3); the large amount of outright loss of wetlands and other waters; the importance of
wetlands and other waters to salmon populations, both as habitat and as sources of groundwater inputs,
nutrients, and other subsidies important to salmon productivity in downstream waters; the degradation
of downstream anadromous fish streams from the loss of ecological subsidies provided by the lost
headwater wetlands and other waters; and the resulting erosion of habitat complexity and
biocomplexity within the SFK, NFK, and UTC watersheds, both of which are key to the abundance and
stability of salmon populations within these watersheds. This conclusion supports the recommended
restriction described in Section 5.2.
4.2.4 Adverse Effects from Changes in Streamflow in Downstream
Anadromous Fish Streams
EPA Region 10 has determined that the discharge of dredged or fill material associated with the
construction and routine operation of the 2020 Mine Plan, resulting in streamflow alterations greater
than 20 percent of average monthly streamflow in at least 29 miles (46.7 km) of anadromous fish
streams, would be likely to have unacceptable adverse effects on anadromous fishery areas in the SFK
and NFK watersheds. This conclusion is based on the extent and magnitude of changes to streamflow in
anadromous fish streams downstream of the mine site and associated adverse effects on the extent and
quality of anadromous fish habitat, including spawning and rearing habitat.
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This section first describes the methodology used for identifying anadromous fish stream reaches that
would experience unacceptable adverse effects (Section 4.2.4.1). It then summarizes the specific
anadromous fish streams where excessive streamflow changes are expected (Section 4.2.4.2), the
downstream anadromous habitat that would be affected (Section 4.2.4.3), and the unacceptable adverse
effects on anadromous habitat that would result from the predicted streamflow alterations
(Section 4.2.4.4).
4,2.4,1 Methodology for Analyzing Streamflow Changes in Downstream Anadromous
Fish Streams
The natural flow regime, defined as the characteristic pattern of streamflow magnitude, timing,
duration, frequency, and rate of change (Poff et al. 1997), plays a critical role in supporting and
maintaining both the ecological integrity of streams and rivers and the services they provide. Every
stream and river has a characteristic flow regime and a biotic community adapted to it, reflecting the
importance of flow regime in creating and maintaining instream habitat and shaping the evolution of
both ecological processes and aquatic biota (Bunn and Arthington 2002, Naiman et al. 2002, Annear et
al. 2004). Human-induced alteration of the natural flow regime can degrade the physical, chemical, and
biological properties of a water body, leading to loss of aquatic life and reduced aquatic biodiversity
(e.g., Poff et al. 1997, Bunn and Arthington 2002, Naiman et al. 2002, Annear et al. 2004, Poff and
Zimmerman 2010). Maintenance of natural flows and the patterns of longitudinal and lateral
connectivity that result from these flows is essential to the viability of many riverine species (Bunn and
Arthington 2002). Because flow regime directly or indirectly affects all other functions, flow regime is
often considered the most significant stream function (Lytle and Poff 2004, Fischenich 2006, Sofi et al.
2020).
Aquatic ecologists have long recognized that a much fuller spectrum of flow conditions (e.g., base flows,
high flows, flood flows) is needed to sustain native species than is provided by instream flow models,
such as the Physical Habitat Simulation System (PHABSIM) model used to evaluate streamflow in the
FEIS (Postel and Richter 2003). For example, Pahl-Wostl et al. (2013: Page 342) were critical of habitat-
based approaches, stating "[e]arly static approaches aimed to define either minimum or average flows to
support key fish species or maintain instream habitat (sometimes revealingly termed 'compensation
flows'); but these are now viewed as too simplistic to support complex flow-dependent ecosystem
functions." Such approaches predict benefits to fish based on consideration of limited flow metrics such
as water depth and velocity (Postel and Richter 2003) and do not account for other ecologically relevant
fish habitat parameters, such as groundwater exchange, substrate, water temperature, water chemistry,
cover, and habitat complexity (e.g., wetlands and other off-channel habitats) (Appendix B: Section
B.4.2.1).
Protecting ecosystem integrity requires maintaining multiple components of the natural flow regime
within their typical ranges of variability (Pahl-Wostl et al. 2013). This perspective requires an
understanding of both natural flow regimes over space and time and the many ways in which aquatic
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habitats, species, and life stages respond to varied flow conditions (Warren et al. 2015, Novak et al.
2016, Flitcroft et al. 2016, Flitcroft et al. 2019).
For streams in the Bristol Bay region, natural temporal streamflow variability results from fall storm
events, winter low flows under ice cover, spring snowmelt peak flows, and subsequent recession of
streamflow into summer (EPA 2014: Chapters 3 and 7, USACE 2020a: Section 3.16). These seasonal flow
regimes affect channel development and maintenance; connectivity between active channels and off-
channel habitats; transport of sediment and nutrients; timing and success of fish migration and
spawning; and survival of fish eggs and juveniles (EPA 2014: Chapter 7).
Recognizing the importance of natural flow regimes to habitat-forming processes and the biotic integrity of
salmon ecosystems in the SFK, NFK, and UTC watersheds (EPA 2014: Chapter 7), EPA Region 10 has
evaluated the 2020 Mine Plan using projected streamflow changes from natural conditions in terms of
percent change from natural flows. Such an approach targets functional hydrogeomorphic processes in an
entire aquatic ecosystem, rather than focusing on a specific species or set of species (e.g., salmon) that may
have different habitat requirements than other biota in the natural system.
Based on case studies from around the world and literature on ecological flows dating back to the 1970s,
Richter et al. (2012) found that regardless of geographic location, daily streamflow alterations of greater
than 20 percent can cause major changes in the structure and function of streams. Streamflow alterations
between 11 and 20 percent can also result in changes in ecosystem structure and function, but to a lesser
extent. Although Richter et al. (2012) note that limiting daily flow alterations to 20 percent or less may be
protective in some circumstances, they also caution that it may be insufficient to fully protect ecological
values in certain rivers. Because Pacific salmon are locally adapted to environmental cues such as small
differences or changes in water temperature, chemical composition, and the natural flow regime of natal
waters (Vannote et al. 1980, Poff et al. 1997, Fausch et al. 2002), it is likely that a lower threshold of
streamflow modification would be necessary to adequately protect these species. While predicted flow
changes of less than 20 percent can also affect fishes and diminish stream functional capacity, EPA
Region 10 has not made a determination of how such smaller changes to average monthly streamflow
(i.e., less than 20 percent) resulting from the 2020 Mine Plan would translate to effects on anadromous
fishery areas. Flow modeling conducted for the 2020 Mine Plan, as presented in the FEIS and outlined in
Section 4.2.4.2, describes streamflow alteration in terms of percent changes to average monthly
streamflows rather than percent changes to daily streamflows. EPA Region 10 recognizes that daily
flows would be more variable than monthly averages (e.g., Appendix B: Figure B-l); however, EPA
Region 10 believes that average monthly flows are a useful hydrologic metric (Eng et al. 2017, George et
al. 2021), particularly for relative comparison between alternatives, and that the extent of impacts
identified on a monthly time scale provides a reasonable minimum approximation of the extent of
impacts from the 2020 Mine Plan, given the amount of error that can be associated with estimations of
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daily flows generated by models.59 In addition, the streamflow impact information provided in the FEIS
has been subject to public review. EPA Region 10 recognizes using average monthly streamflows to
identify the extent of impacts may under-represent and under-predict the true extent of unacceptable
adverse effects, because relying on average monthly streamflow does not reflect streamflow changes
that anadromous fishes and their habitats would experience on a daily or sub-daily basis (Appendix B:
Sections B.2.1 and B.3.2). As a result, use of average monthly flows provides a generalized indicator of
streamflow change that captures only dramatic changes from natural conditions, particularly when
coupled with the narrowed focus on changes in excess of 20 percent.
As such, the following evaluation of average monthly streamflow alteration identifies the specific
anadromous fish streams where streamflow changes would be expected to vary more than 20 percent
from baseline average monthly streamflows (Section 4.2.4.2), the anadromous habitat that would be
affected (Section 4.2.4.3), and the unacceptable adverse effects that would result from these streamflow
alterations (Section 4.2.4.4).
4,2.4,2 Overview of Mine Site Operations that Affect Downstream Streamflow
The FEIS describes how the 2020 Mine Plan would change the volume, distribution, and flowpath of
surface water and groundwater flows in and beyond the mine footprint (USACE 2020a: Sections 4.16 and
4.17). It describes how construction and routine operation of the 2020 Mine Plan would affect surface
water quantity and distribution in the SFK, NFK, UTC, and several tributaries. Operational impacts of
mining on streamflow were estimated based on the conditions expected at the end of operations (i.e., end-
of-mine) rather than at periodic time steps during operations (USACE 2020a: Section 4.16). Table 4-4
provides estimated percent changes in average monthly streamflows, by river reach, between baseline and
end-of-mine.60 Dewatering of the pit area would be necessary during construction and operation,
beginning approximately 2 years before the start of ore processing. The groundwater drawdown
associated with dewatering the open pit would be responsible for much of the predicted streamflow
reduction, along with the collection and rerouting of surface water runoff from the mine site footprint.
59 USACE did not present or analyze daily flow information in the FEIS. Impacts of predicted changes to fish habitat
were run on a daily time step (PLP 2019c: RFI149), but the daily discharges used in that analysis were estimated
from the monthly flows. RFI 161 provides daily streamflow estimates that could be used to evaluate project
impacts on daily flows (PLP 2020d: RFI 161), but this information was not subject to public review prior to its
release. Questions remain regarding the methods, assumptions, and limitations of the daily streamflow estimates
provided in RFI 161 (PLP 2020d: RFI 161).
60 River reaches are lettered in order of in the upstream direction (i.e., Reach A is the most downstream reach,
located just above the confluence of the SFK and NFK; Reach B is the reach upstream of Reach A; and so forth).
Recommended Determination
4-39
December 2022
-------
Section 4
Basis for Recommended Determination
RMfc.
aclilKwffawiwiBiM
¦
¦
¦IB
¦II
rom Baselim
IHiMl
I Annual Mean
Location
Jan
Feb
__—.
Mar
Apr
_____
May
Jun
Jul
r-Tm
Aug Sept
1
Oct
Nov
Dec
iV'fsiivliiy
Change
NFK, Reach A
+2.2
+ 10.6
+ 19.1
+23.5
-6.2
-12.1
-8.7
-9.2
-8.0
-7.2
-3.5
-3.3
-0.2
NFK Reach B
+2.9
+11.6
+21.5
+29.0
-9.0
-13.5
-9.5
-10.2
-9.1
-8.1
-3.2
-3.4
-0.1
NFK Reach C
+8.2
+29.0
+68.1
+ 110.2
-13.3
-20.4
-15.6
-16.4
-13.9
-13.4
-6.3
-5.4
+9.2
NFK Reach D
+ 101.2
+ 127.9
+157.6
+170.0
+26.9
+23.1
+44.2
+46.1
+36.1
+34.3
+44.4
+73.2
+73.7
NFK Trib 1.19
-100.0
-100.0
-100.0
-100.0
-100.0
-100.0
-100.0
-100.0
-100.0
-100.0
-100.0
-100.0
-100.0
SFK, Reach A
-2.7
-2.7
-2.1
-0.8
-1.4
-1.6
-2.8
-2.4
-2.3
-2.5
-2.3
-2.7
-2.2
SFK, Reach B
-2.2
-1.7
-0.5
+ 1.3
-2.4
-2.6
-3.3
-3.0
-3.2
-2.7
-2.5
-2.4
-2.1
SFK Reach C
+3.8
0.0
0.0
0.0
-2.5
-2.8
-4.5
-3.9
-4.6
-3.1
-1.5
-1.2
-1.7
SFK Reach D
+ 14.6
+27.5
+50.9
+ 109.0
-13.5
-15.0
-12.9
-11.9
-12.5
-10.2
+3.7
+9.3
+ 11.6
SFK Reach E
-50.7
-51.5
-53.0
-52.2
-32.1
-33.1
-34.6
-37.4
-35.6
-38.8
-44.9
-49.4
-42.8
SFK Trib 1.19
-13.4
-15.2
-17.1
-19.0
-3.7
-4.8
-7.2
-6.6
-5.3
-8.1
-10.6
-12.6
-10.3
SFK Trib 1.24
+ 18.4
+97.9
0.0
+2.2
+2.7
+7.7
+ 11.0
+5.8
+4.8
+4.0
+7.0
+7.3
+ 14.1
UTC, Reach A
+0.4
+0.5
+0.7
+0.8
0.0
-0.1
-0.2
0.0
0.0
-0.1
0.0
+0.2
+0.2
UTC, Reach B
+0.4
+0.5
+0.6
+0.7
0.0
-0.1
-0.2
0.0
0.0
-0.1
0.0
+0.2
+0.2
UTC, Reach C
+0.5
+0.7
+0.8
+0.9
+0.1
-0.1
-0.2
0.0
0.0
-0.1
0.0
+0.3
+0.2
UTC, Reach D
+0.8
+ 1.1
+ 1.3
+ 1.7
+0.1
-0.2
-0.3
0.0
0.0
-0.2
+0.1
+0.4
+0.4
UTC, Reach E
+ 1.2
+ 1.9
+2.5
+3.2
+0.1
-0.2
-0.4
-0.1
-0.1
-0.2
+0.1
+0.6
+0.7
UTC, Reach F
+3.8
+5.5
+6.8
+8.6
+0.4
-0.8
-1.3
-0.2
-0.2
-0.7
+0.3
+ 1.9
+2.0
UTC, Trib 1.19
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
Recommended Determination
4-40
December 2022
-------
Section 4
Basis for Recommended Determination
During operation, two WTPs would treat water collected within the mine site footprint prior to its release
to the environment (Figure 4-1). WTP #1 would treat surplus groundwater and surface water runoff
collected in the open pit and the surrounding areas. WTP #2 would collect and treat water from the main
WMP, which would receive water from the TSFs and the TSF main embankment seepage. Treated water
from the WTPs would be routed to three outfall locations and then discharged into the SFK, NFK, and
UTC.61 In an average year, mean monthly discharges to the SFK, NFK, and UTC would vary between 1.3 to
10 cubic feet per second (cfs), 17 to 27 cfs, and 0.2 to 1.4 cfs, respectively (Knight Piesold 2019a: Table 2).
Although operations would change the availability of surface flows to area streams, surplus-treated
water would be released from the mine site to benefit priority fish species and life stages (USACE 2020a:
Section 4.24). Monthly habitat flow needs were identified for each month of the year in the SFK, NFK,
and UTC based on priority species and life stages. In the SFK and NFK, the priority species used to
determine habitat flow needs were Chinook Salmon, Coho Salmon, Rainbow Trout, and Arctic Grayling;
these same species were used to determine habitat flow needs in UTC, except Sockeye Salmon replaced
Chinook Salmon. In terms of life stage priorities for flow optimization, the spawning life stage was given
a higher priority than juvenile rearing (PLP 2018b: RFI 048).
The FEIS indicates water from both WTPs would be strategically discharged, based on modeling and
monitoring during discharge. However, the only monitoring proposed by PLP appears to be quarterly
streamflow and fish presence surveys (PLP 2019b: RFI 135).62 WTP discharges, thus, would be
preplanned based on modeling and a set of assumptions. Monthly WTP discharges would be the amount
needed to "optimize" downstream habitat assuming the historic monthly average streamflow (i.e., given
an "average climatic year," or 50 percent exceedance probability) was to occur at the representative
downstream gage location.63
EPA Region 10 has concerns with the methods used to establish the ecosystem flow requirements and
predict impacts on downstream anadromous fish habitat as presented in the FEIS (Appendix B: Sections
B.3 and B.4). However, as described previously, the streamflow impact information provided in the FEIS
provides a reasonable minimum approximation of impacts and the best available information for this
project.
61 These locations are shown in FEIS Figure 4.18-1 (Knight Piesold 2019b, USACE 2020a: Section 4.18).
62 The Monitoring Summary provided by PLP states that monitoring of surface water flow and quality is proposed
to be conducted downstream of water discharge points on a quarterly basis and will focus on streamflow and fish
presence surveys (PLP 2019b: RFI 135).
63 Wet, average, and dry years were determined for each target species and life stage between 1942 and 2017 at
Gage NK100A (USGS Gage 15302250) for WTP#1 and Gage SK100B (USGS Gage 1530220) for WTP#2. (PLP 2018b:
RFI 048).
Recommended Determination
4-41
December 2022
-------
Section 4
Basis for Recommended Determination
4,2.4,3 Extent of Streamflow Changes in Downstream Anadromous Fish Streams
The FEIS predicts changes in streamflow down to the confluence of the SFK and NFK, with and without
the addition of treated water.64 These estimates indicate that reaches of the SFK and NFK closest to the
mine site would experience greater changes in average monthly streamflow than reaches farther from
the mine site (USACE 2020a: Section 4.16). The FEIS states:
The geographic extent of the impact on the NFK and the SFK rivers may extend just below
the confluence of the two rivers. After the flows combine at the confluence of the NFK and
SFK rivers, discernable changes in flow would be unlikely and are expected to be within
historic and seasonal variation in the Koktuli River (USACE 2020a: Page 4.16-2).
The NFK flows approximately 23 miles downstream from the mine site before reaching the SFK
confluence, and the SFK extends approximately 38 miles from the mine site in the headwaters
before reaching the NFK confluence. Thus, the FEIS indicates up to 61 miles of these two rivers
combined would be impacted beyond the historic and seasonal variation that naturally occurs.65
Based on information presented in the FEIS, EPA Region 10 has estimated that operation of the 2020
Mine Plan, with the addition of treated water, would alter (i.e., either increase or decrease) streamflows
by more than 20 percent of baseline average monthly flow in at least 29 miles (46.7 km) of anadromous
fish streams downstream of the mine site (Figure 4-9, Table 4-5).66 These streamflow alterations are
derived from Table 4-4 (USACE 2020a: Table 4.16-3), which presents changes in average monthly
streamflow, relative to natural streamflow conditions, that would result after water captured at the
mine site is discharged as treated water from the WTPs. These streamflow changes would affect 18.7
miles (30.1 km) or 29 percent of anadromous fish streams in the NFK watershed and approximately
10.4 miles (16.7 km) or 17 percent of anadromous fish streams in the SFK watershed (Giefer and
Graziano 2022) (Figure 4-9).
In the majority of the SFK and NFK river reaches, streamflow alterations would vary seasonally. Reaches
that would experience streamflow reductions between the spring and the winter would also experience
streamflow increases between the winter and spring. In total, streamflow reductions exceeding 20
percent of average monthly streamflow would occur in at least one month per year in at least 13.1 miles
(21.4 km) of anadromous fish streams downstream of the mine site, specifically in NFK Reach C,
Tributaries NFK 1.190 and 1.200, and SFK above Frying Pan Lake (i.e., upstream of SK100G) (Table 4-5).
64 EPA Region 10's review only evaluated changes to streamflow with the addition of treated water. If WTPs were
unable to discharge treated water for any period, streamflow reductions experienced in downstream anadromous
fish streams would be greater than are discussed herein (USACE 2020a: Section 4.16).
65 The FEIS indicates streamflow in the UTC and the Koktuli River below the confluence of the NFK and SFK would
notbe negatively impacted by the project (USACE 2020a: Section 4.24).
66 The streamflow alteration values presented in FEIS Table 4.16-3 (Table 4-4 here) were estimated using data
from specific PLP stream gages or by averaging two gages in the reach (PLP 2019a: RFI 109f). To provide
conservative estimates of impacts (i.e., to ensure not to overestimate impacts), streamflow estimates described
herein for the mainstem rivers were assigned to the river location of gages identified in RFI 109f (PLP 2019a: RFI
109f), rather than for extended reach lengths downstream. Streamflow alteration estimates were assumed to
extend upstream from the source gage to at least the next gage, major confluence point, the mine footprint, or the
end anadromous habitat As a result, streamflow impacts may extend further downstream than stated herein.
Recommended Determination
4-42
December 2022
-------
Section 4
Basis for Recommended Determination
Figure 4-9. Streams and rivers with documented salmon use that would experience streamflow alterations greater than 20
percent of baseline average monthly streamflows as a result of the Pebble 2020 Mine Plan. Species distributions are based on
the Anadromous Waters Catalog (Giefer and Graziano 2022). Streamflow alteration is assigned at a gage and extends upstream
(see Footnote 66 in Section 4.2.4.3 for a discussion of methodology).
NK100B
[SK100G
'NK100B
NK100C
UT100E
NK119A]
SK100G,
SK100F]
UT100C1
SK124A
.SK119A
[SK1P0LI=4
tSKIOOGi
[SK100B
Nushagak
Kvichak
NK119B \1
Frying
Pan Lake
SK100F
UT100C2
UT100C
— Coho
Chinook
• Sockeye
Chum
© PLP/USGS Gages
Streamflow Alteration >
20%
NHD Stream or River
2020 Mine Footprint
South Fork Koktuli,
r 1, North Fork Koktuli, and
Upper Talarik Creek
Watersheds
0 2 4
1 i i i I i i i I
Miles
0 3 6
1 ' i ' I ' i i I
Kilometers
Recommended Determination
4-43
December 2022
-------
SFK
mainstem
upstream of
SK100G
2.1
SFK,
Reach E
-53.0%
Rearing
- g
- g
- g
SK100G to
inlet of Frying
Pan Lake
0.7
Rearing
- g
Rearing11
- g
Frying Pan
Lake to
SK100F
1.4
SFK,
Reach D
109.0%
Rearing
- g
Rearing
-g
SFK
tributary
SFK 1.240
6.2d
SFK, Trib
1.24
97.9%
Rearing,
present
Present
Rearing
- g
NFK
tributaries
NFK 1.190
0.27®
NFK, Trib
1.19
-100.0%
Spawning,
rearing
Rearing
- g
- g
NFK 1.200
0.36®
NFK, Trib
1.20
_f
Rearing,
present
Rearing
-g
-g
NFK
mainstem
NFK below
Tributary 1.200
and above
Tributary 1.190
1.2
NFK,
Reach D
170.0%
Spawning,
rearing
Rearing
Spawning
- g
NFK below
Tributary 1.190
to FRS-4
9.6
NFK,
Reach C
110.2%
Spawning,
rearing
Spawning,
rearing
Spawning,
rearing
Spawning,
rearing
4.6
NFK,
Reach B
29.0%
Spawning,
rearing
Spawning,
rearing
Spawning,
rearing
Spawning
27
NFK,
Reach A
23.5%
Spawning,
rearing
Spawning,
rearing
Spawning,
rearing
Spawning
Notes:
a Reaches defined by stream gages, as shown in Figure 4-9.
b Affected lengths were determined by EPA Region 10 based on information in the FEIS and typically extend upstream from the source gage to at
least the end of the FEIS reach, the next upstream gage, major confluence point, the mine footprint, or the end of documented anadromous fish
streams.
c From the Anadromous Waters Catalog (Giefer and Graziano 2022).
d This length includes the entirety of Tributary SFK 1.240 down to its confluence with Tributary SFK 1.260.
eThis length is the extent that is assumed would still be accessible to anadromous fishes below the sediment pond.
f No streamflow information was provided for this reach in FEIS Table 4.16-3 (Table 4-4).
s Blanks indicate that the species has not been documented to occur in that reach in the Anadromous Waters Catalog (Giefer and Graziano 2022).
h Sockeye Salmon rearing habitat only extends approximately 0.6 mile upstream of Frying Pan Lake and not all the way up to SK100G (Giefer and
Graziano 2022).
Additionally, WTP discharges associated with the 2020 Mine Plan would increase streamflow by more
than 20 percent of baseline average monthly streamflow in at least 25.7 miles (41.3 km) of downstream
anadromous fish streams (Table 4-5). Most streamflow increases would occur in the mainstem NFK,
where at least 18.1 miles (29.1 km) would experience seasonal streamflow increases of more than
20 percent of baseline average monthly flow. The remaining 7.6 miles (12.2 km) of anadromous fish
streams that would experience streamflow increases of more than 20 percent from baseline average
monthly flows are in the SFK watershed, in the mainstem at Frying Pan Lake and in Tributary SFK 1.240.
Recommended Determination
4-44
December 2022
-------
Section 4
Basis for Recommended Determination
4,2.4,4 Downstream Anadromous Fish Habitat Affected by Streamfiow Changes
Changes in surface water and groundwater contributions to streams associated with the discharge of
dredged and fill material for the construction and routine operation of the 2020 Mine Plan would reduce
both the extent and quality of anadromous fish habitats downstream of the mine site. As described in
Section 4.2.1, little or no spawning or rearing habitat for Coho and Chinook salmon would remain in
Tributary NFK 1.190 due to placement of mine site features just upstream of its confluence with the
mainstem NFK; most of Tributary NFK 1.200 also would be eliminated by the main WMP (Figure 4-9).
The FEIS states that the expected loss of headwater aquatic habitats, including 125 acres (0.5 km2) of
riverine wetlands, would affect downstream surface water flows and groundwater exchange, resulting
in impacts to aquatic resources in approximately 66 miles (106.2 km) of streams. The duration of flow
changes would be permanent, beginning at project construction, continuing through mine operations,
and remaining post-closure (USACE 2020a: Section 4.24).
The most notable streamfiow reductions downstream of the mine site would occur in the 2.8-mile
(3.4-km) reach of anadromous fish habitat in the SFK mainstem leading to Frying Pan Lake, immediately
below the open pit drawdown zone, in which average monthly streamfiow would be reduced by
between 32 and 53 percent from the baseline average monthly streamfiow in every month of the year
(Tables 4-4 and 4-5). These affected reaches provide juvenile rearing habitat for Coho Salmon, and the
lowermost 0.6 mile above the lake provides juvenile rearing habitat for Sockeye Salmon (Giefer and
Graziano 2022).
As a result of dewatering at the open pit, streamfiow reductions in the SFK would reduce natural inflows
to Frying Pan Lake, a 150-acre (0.6 km2) shallow lake located on the SFK, 2.5 miles (4.0 km)
downstream of the open pit (Figure 4-1). Frying Pan Lake provides rearing habitat for juvenile Coho and
Sockeye salmon, as well as other resident fishes (ADF&G 2022a). As previously discussed, WTP
discharges would be used to mitigate these streamfiow reductions. Even with such WTP discharges,
there would still be net reductions in streamfiow between May and October, when streamfiow at gage
SK100F is estimated to be reduced between 10.2 to 15 percent below the baseline average monthly flow.
During the winter and spring, WTP discharges would go beyond offsetting streamfiow reductions and
result in significant streamfiow increases: average monthly streamfiow would increase 27.5 percent
over the baseline average monthly streamfiow in February, 50.9 percent over baseline in March, and
109 percent over baseline in April (Figure 4-9, Table 4-4). Sustaining such increases above the natural
flow regime for months at a time could have a dramatic effect on aquatic resources associated with this
reach of the SFK.
These impacts to streamfiow in the SFK would continue some distance downstream of gage SK100F, but
it is unclear how far due to a lack of detail in the FEIS (USACE 2020a: Section 4.16). The next
downstream location for which streamfiow data are presented in Table 4-4 (FEIS Table 4.16-3) is SFK
Reach C, based on streamfiow at gage SK100C (PLP 2019a: RFI 109f), 11.7 river miles (18.9 km)
downstream of SK100F (PLP 2020d: RFI 161). At this point, impacts to streamfiow resulting from
Recommended Determination
4-45
December 2022
-------
Section 4
Basis for Recommended Determination
operations at the mine would be less than 5 percent below baseline average monthly flow, assuming
streamflow and WTP discharges occurred as modeled during the average climatic year.
Reductions in streamflow would also affect 5.1 miles (8.2 km) of anadromous fish spawning and rearing
habitat in Tributary SFK 1.190 (USACE 2020a: Section 4.24), due to water captured in the south seepage
recycle pond and returned to the bulk TSF main seepage pond (Figure 4-1; USACE 2020a: Section 4.16).
Tributary SFK 1.190 would experience streamflow reductions every winter and spring ranging between
approximately 12.6 percent (in December) to the maximum reduction of 19 percent (in April) below the
baseline average monthly streamflow (Table 4-4).
The streamflow estimates for this tributary were generated based on streamflow gage SK119A
(PLP 2019a: RFI 109f), approximately 3 miles (4.8 km) downstream of mine footprint components
associated with the south embankment of the bulk TSF, including a seepage collection system and
sediment pond. The upper reaches of Tributary SFK 1.190 closest to the mine are expected to experience
even greater reductions in streamflow compared to those estimated at streamflow gage SK119A. The
upper extent of anadromous fish habitat is Chinook Salmon rearing habitat, located within
approximately 600 feet (182.9 m) of the mine footprint. Coho Salmon also use this tributary for rearing
beginning approximately 1.3 miles (2.1 km) downstream of the mine footprint, and Chum Salmon are
present approximately 1.8 miles (2.9 km) downstream of the mine footprint (Giefer and Graziano 2022).
The FEIS indicates Sockeye Salmon are also present in this reach. Although streamflow reductions in
Tributary SFK 1.190 are estimated to reach only 19 percent below baseline average monthly
streamflow, the FEIS predicts these reductions would nonetheless result in losses of spawning habitat
area in Tributary SFK 1.190. These losses would eliminate 18.1,13, 5.9, and 8.6 percent of spawning
habitat for Chinook, Coho, Chum, and Sockeye salmon, respectively, in Tributary SFK 1.190 during an
average climatic year (USACE 2020a: Table K4.24-1).67
Streamflow reductions would also be expected in mainstem reaches of the SFK and NFK during spring,
summer, and fall. In total, approximately 21.4 miles (34.4 km) of the SFK and NFK would experience
some degree of streamflow reduction from baseline conditions between May through late fall or winter
due to loss of headwater and groundwater contributions. These reaches would also experience seasonal
increases from baseline average monthly streamflow between January and April due to discharges of
surplus water. For example, average monthly streamflow in the mainstem NFK below the mine site (i.e.,
NFK Reach C) would vary from 110.2 percent more flow in April to 20.4 percent less in June relative to
baseline average monthly streamflows (Table 4-4).
Streamflow reductions in the NFK would extend 16.9 miles (27.2 km) downstream of the mine site.
These reductions would begin in NFK Reach C below the confluence with Tributary NFK 1.190
(Figure 4-9), where streamflow would be reduced by more than 20 percent from the baseline average
monthly flow. Streamflow reductions would continue downstream to at least stream gage FRS-4, where
streamflow is estimated to be reduced by 12 to 13 percent from the baseline average monthly flow
67 EPA Region 10 believes the habitat losses described in the FEIS under-represent impacts on downstream
anadromous fish streams (Appendix B: Sections B.3 and B.4).
Recommended Determination
4-46
December 2022
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Section 4
Basis for Recommended Determination
(Tables 4-4 and 4-5, Figure 4-9). These NFK reaches provide spawning and rearing habitat for Chinook,
Coho, Sockeye, and Chum salmon (Table 4-5, Figure 4-9) and these streamflow reductions would affect
at least 26 percent of the documented anadromous fish streams in the NFK watershed (Giefer and
Graziano 2022). The FEIS predicts a loss of Chinook spawning habitat area in all NFK reaches
downstream of the mine site: 9.9 percent in NFK Reach C, 3.3 percent in NFK Reach B, and 1.8 percent in
NFK Reach A (USACE 2020a: Table K4.24-1).68
Across the SFK and NFK watersheds, although treated water discharges were included, streamflow would
still be reduced by more than 20 percent from the baseline average monthly flow in at least one month of
the year in approximately 13.1 miles of anadromous fish streams, specifically in NFK Reach C, Tributaries
NFK 1.190 and 1.200, and SFK above Frying Pan Lake (i.e., upstream of SK100G) (Table 4-5, Figure 4-9).
Operation of the 2020 Mine Plan would also increase streamflow by more than 20 percent of baseline
average monthly streamflow in at least 25.7 miles (41.3 km) of anadromous fish streams due to WTP
discharges (Table 4-5). Most streamflow increases would occur in the mainstem NFK, where at least
18.1 miles (29.1 km) would seasonally experience streamflow increases of more than 20 percent of
baseline average monthly flow. These 18.1 miles (29.1 km) include the 16.9 miles (27.2 km) of the
mainstem NFK (i.e., down to gage FRS-4) that would also experience some degree of streamflow
reduction between May and December, and the remaining 1.2 miles (1.9 km) of the NFK between the
confluence of Tributaries NFK 1.200 and 1.190, where WTP discharges would result in increases to flow
year-round.
The remaining 7.6 miles (12.2 km) of anadromous fish streams that would experience streamflow
increases of more than 20 percent from baseline average monthly flow are the SFK between SK100G and
SK100F and Tributary SFK 1.240 (Table 4-5, Figure 4-9). Increases in the SFK would result from WTP
discharges to Frying Pan Lake, and Tributary SFK 1.240 would receive discharges from a diversion
channel of non-contact water collected around the project's infrastructure (Knight Piesold 2019b).
To optimize fish habitat farther downstream, reaches closest to the WTP discharge points would
experience more dramatic increases in streamflow velocities that could impede salmon migration,
particularly for juveniles. For example, NFK Reach D, immediately downstream of the WTP discharge
point, would experience streamflow increases of 101 to 170 percent from baseline average monthly flow
every month between January and April (Table 4-4). This reach provides spawning habitat for Coho and
Sockeye salmon, and rearing habitat for juvenile Coho and Chinook salmon (Giefer and Graziano 2022).
Habitat quality for juvenile salmon rearing and benthic macroinvertebrates could be degraded due to
increased scour and mobilization of sediments and increased turbidity. Streamflow increases would be
expected to dissipate farther downstream from the mine site, but even the most downstream NFK point
evaluated (i.e., PLP's project-specific stream gage FRS-4, which was used to estimate streamflow in NFK
Reach A) would vary from 23.5 percent more to 12.1 percent less than the baseline average monthly
68 EPA Region 10 believes the habitat losses described in the FEIS under-represent impacts on downstream
anadromous habitat area (Appendix B: Sections B.3 and B.4).
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streamflow (Table 4-4). Based on information in the FEIS, these streamflow increases would likely
extend down to the confluence of the SFK and NFK (USACE 2020a: Section 4.16).
4,2.4,5 Adverse Effects of Streamflow Changes in Downstream Anadromous Fish
Streams
Streamflow reductions of the extent and duration predicted by analysis of streamflow data associated
with the 2020 Mine Plan would reduce instream habitat availability, particularly during periods of
natural low flows; fragment stream habitats; and preclude normal seasonal movements by anadromous
and migratory resident fishes (West et al. 1992, Cunjak 1996, EPA 2014: Chapter 7). Diminished
streamflows would also likely reduce the frequency and duration of connectivity to off-channel habitats
such as side channels, riparian wetlands, and beaver ponds, reducing the spatial extent of such habitats
or eliminating them altogether. At present, some off-channel habitats likely connect to the main
channels at least during annual spring and fall floods (Section 3.2.4). The loss of access to off-channel
areas, particularly those with groundwater connectivity, would remove critical rearing habitats for
several species of juvenile salmonids (Table 3-10) (Quinn 2018, Huntsman and Falke 2019).
Groundwater drawdown associated with dewatering the open pit would be responsible for much of the
predicted streamflow reductions. The loss of groundwater inputs in affected reaches would not only
reduce streamflow volumes, but would also have profound adverse impacts on stream thermal regimes
(EPA 2014: Chapter 7). The FEIS predicts temperature changes from -1.6 to +2.8 °C in the SFK, NFK, and
UTC drainages from about 0.5 to 2.75 miles downstream of WTP discharges (USACE 2020a: Section 4.18).
Warmer summer water temperatures could limit summer habitat for salmon, whereas colder winter water
temperatures could adversely affect egg development, hatching, and emergence timing (Brannon 1987,
Beacham and Murray 1990, Hendry et al. 1998, Quinn 2018). The threshold between completely frozen
and partially frozen streams can be a narrow one (Irons et al. 1989), especially for small streams with low
winter groundwater discharge such as many of the headwater streams in the SFK, NFK, and UTC
watersheds. Predicted reductions in flow and associated changes in thermal regimes could substantially
alter fish habitat, particularly the extent of critical unfrozen overwintering habitat (Huusko et al. 2007,
Brown et al. 2011).
Warmer summer and colder winter temperatures resulting from the loss of groundwater inputs also
would likely change the species composition and richness of macroinvertebrates, a key food for juvenile
salmonids, and alter overall macroinvertebrate abundance and productivity in the affected reaches (e.g.,
Campbell et al. 2020). In addition to changes in species composition and richness of macroinvertebrates,
reduced hydrologic connectivity between streams and riparian wetlands would also likely reduce or
eliminate the export of detritus, macroinvertebrates, and other ecological subsidies from wetlands and
off-channel habitats to streams.
Reduced streamflows would also likely change sediment transport dynamics, resulting in the deposition
of more or finer sediment that could smother eggs or render stream substrates less suitable for
spawning. Streambed aggradation from increased sedimentation could lead to further hydrologic
modification, loss of habitat complexity, simplification of pools important for rearing salmon, and
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outright loss or fragmentation of habitat. Lower streamflows could also result in reduced dissolved
oxygen levels. Taken together, streamflow changes could alter channel geometry and destabilize channel
structure, with effects propagating downstream.
At the other extreme, streamflow increases greater than 20 percent likely would degrade habitat
suitability for salmon (EPA 2014: Chapter 7). Brekkan et al. (2022: Page 8) conclude that the stream
type at the mainstem SFK, NFK, and UTC immediately downstream of the mine site is "very susceptible
to scour and erosion and can be significantly altered and rapidly de-stabilized by channel or landscape
disturbances and changes in the flow or sediment regimes of the contributing watershed." As result,
increases in streamflow could increase mobilization of sediments, leading to altered spawning gravel
quality, reduced survival of salmon eggs that could be scoured or buried (Buffington et al. 2004), or
reduced foraging efficiency of juvenile salmon (Bjornn and Reiser 1991). Increased streamflows could
also eliminate off-channel habitat through the erosion of streambanks, and could reduce invertebrate
populations as a result of streambed scour and erosion.
Moreover, WTP discharges have the potential to change stream temperatures (EPA 2014: Chapter 8),
particularly when combined with reductions in groundwater and tributary inputs that contribute to
river thermodynamics.69 Because the timing of salmon migration, spawning, and incubation is closely
tied to seasonal water temperatures, any change in the thermal regime could disrupt life history timing
cues and result in mismatches between fishes and their environments that adversely affect survival
(Angilletta et al. 2008). Thus, streamflow reductions resulting from the loss of temperature-moderating
groundwater inputs or streamflow increases resulting from temperature-altering WTP discharges could
reduce diversity of run timing and other salmon life history traits (Hodgson and Quinn 2002, Rogers and
Schindler 2011, Ruff et al. 2011), which play an important role in creating and maintaining
biocomplexity (Section 3.3.3). Although fish populations maybe adapted to periodic disturbances
associated with natural flow variability (Poff et al. 1997, Matthews and Marsh-Matthews 2003), changes
that disrupt life history timing cues can adversely affect survival; prolonged changes in streamflow
regimes could have longer-term impacts on fish populations (Jensen and Johnsen 1999, Lytle and Poff
2004).
Overall, the adverse effects of flow alteration on stream and off-channel habitats could substantially reduce
spawning success for Coho Salmon, survival of overwintering Coho, Chinook, and Sockeye salmon, and
ultimately Coho, Chinook, and Sockeye salmon productivity in the SFK and NFK watersheds. Many of the
effects of substantially altered streamflows would reverberate downstream beyond the directly affected
waters, due to reduced quantity and diversity of available food sources such as macroinvertebrates and
reduced success of upstream salmon spawning and rearing. Streamflow changes associated with the 2020
Mine Plan also would affect many other factors that determine high-quality salmon habitat (e.g., water
depth and velocity, substrate size, groundwater exchange, water temperature, food availability), although
effects of streamflow on these other factors are not evaluated in the FEIS (see Appendix B).
69 The extent and duration of temperature changes would depend on the temperature, quantity, and timing of WTP
discharges, as well as the influence of other inputs such as groundwater and tributary inflows.
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As with the habitat losses and degradation described in Sections 4.2.1 through 4.2.3, adverse impacts of
streamflow modification would adversely affect downstream habitat for salmon (Sections 3.2.4 and
4.2.1, Figures 4-3 through 4-5). These downstream waters are ecologically important and provide
spawning and rearing habitat for Coho, Chinook, Sockeye, and Chum salmon in the SFK and NFK
watersheds (Figures 4-2 and 4-3). The magnitude and extent of streamflow changes expected would
degrade downstream anadromous fish streams and adversely affect genetically distinct populations of
Sockeye Salmon in the Koktuli River (including the SFK and NFK) and Coho and Chinook salmon
populations that may be uniquely adapted to the spatial and temporal conditions of their natal streams
(Section 3.3.1). As explained for the loss of 8.5 miles (13.7 km) of anadromous fish streams, the loss and
degradation of downstream anadromous fishery areas in the SFK and NFK watersheds that would result
from elimination of approximately 2,108 acres (8.5 km2) of wetlands and other waters would further
erode habitat complexity and biocomplexity within these watersheds. The diversity of salmon habitats
and associated salmon population diversity helps buffer these salmon populations from sudden and
extreme changes in abundance and ultimately maintain their stability and productivity.
After mining stopped, potentially acid generating waste rock and pyritic tailings would be backfilled into
the open pit and water would continue to be pumped from the open pit during backfilling. After
backfilling is complete (approximately 16 years after mine closure), the open pit would gradually refill
with water, which would begin to restore groundwater inputs to downstream flows (Knight Piesold
2019b). Refilling of the pit during the closure phase is estimated to take approximately 8 years, (Knight
Piesold 2019b). Although groundwater contributions to the SFK would eventually return to pre-mine
conditions, the time periods required for this return far exceed the 2- to 5-year life spans of Coho,
Chinook, and Sockeye salmon. Thus, long-term severe degradation of spawning and rearing habitat for
these species would likely be sustained for several generations.
As previously discussed, proposed water management under the 2020 Mine Plan uses treated
discharges to offset some of the streamflow reductions and address stream habitat losses. According to
the FEIS, treated water releases would be discharged on a monthly basis in direct proportion to the
water captured from each of the three watersheds in the mine footprint area, and discharges would be
managed to optimize downstream priority fish species and life stages. However, the complexity inherent
in surface water-groundwater interactions in the SFK, NFK, and UTC watersheds makes prediction,
regulation, and control of such interactions during large-scale landscape development very difficult
(Hancock 2002). Adequately protecting the critical services that groundwater provides to fishes, via its
influence on surface waters, is complicated by the fact that groundwater flow paths vary at multiple
scales and connections between distant recharge areas and local groundwater discharge areas are
difficult to predict (Power et al. 1999).
Discharges of dredged or fill material anywhere at the mine site for the construction and routine
operation of a mine at the Pebble deposit would result in downstream flow changes in the same
anadromous fish streams that were characterized in the evaluation of the 2020 Mine Plan (Figure 4-3;
Figure 4-9; Table 4-4). The anadromous fish streams in the SFK, NFK, and UTC watersheds support the
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same anadromous fish species and life stages as those that would be affected by the 2020 Mine Plan
(Section 3.3; USACE 2020a: Section 3.24).
4,2.4,6 Impacts on Other Fish Species
Although this recommended determination is based solely on adverse effects on anadromous fishery
areas, EPA Region 10 notes that anadromous fish streams that would be degraded by these alterations
in streamflow also provide habitat for non-anadromous fish species (Figures 4-10 and 4-11). The
assemblage of non-anadromous fishes found in and supported by these streams is an important
component of these habitats and further underscores the biological integrity and ecological value of
these pristine, intact stream networks. The SFK mainstem that would be subject to streamflow
alterations downstream from the mine provides habitat for Arctic Grayling, Northern Pike, sculpin, and
stickleback. Streamflow alterations in Tributary SFK 1.190 would affect habitat for Arctic Grayling, Dolly
Varden, sculpin, and stickleback. Streamflow alterations in Tributary SFK 1.240 would affect habitat for
these same species plus Northern Pike (ADF&G 2022a).
In the NFK watershed, secondary effects of downstream flow alteration would affect mainstem NFK
habitats for Arctic Grayling, Dolly Varden, Rainbow Trout, Round Whitefish, and sculpin. Dolly Varden,
Northern Pike, and Arctic Grayling are harvested in downstream subsistence and recreational fisheries
(Section 4.2.1). Thus, in addition to providing salmon habitat, streams that would be affected by
streamflow alterations also provide habitat for other non-anadromous fish species important to
subsistence and recreational fisheries.
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Figure 4-10. Streams and rivers with occurrence of Arctic Grayling, Rainbow Trout, and Dolly Varden that would
experience streamflow changes as a result of the Pebble 2020 IVIine Plan. Species distributions are based on the
Alaska Freshwater Fish Inventory (ADF&G 2022a). Streamflow alteration is assigned at a gage and extends upstream
(see Footnote 66 in Section 4.2.4.3 for a discussion of methodology).
NK100B
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Streamflow Alteration >
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2020 Mine Footprint
South Fork Koktuli,
i North Fork Koktuli, and
Upper Talarik Creek
Watersheds
0 2 4
l_J I !—J I I J J
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3
¦ ¦ I ¦
Kilometers
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Figure 4-11. Streams and rivers with occurrence of other resident fish species that would experience streamflow changes as a
result of the Pebble 2020 Mine Plan. Species distributions are based on the Alaska Freshwater Fish Inventory (ADF&G 2022a).
Streamflow alteration is assigned at a gage and extends upstream (see Footnote 66 in Section 4.2.4.3 for a discussion of
methodology).
NK100B
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4,2.4,7 Conclusions
EPA Region 10 has considered and evaluated the information available regarding how streamflow
alterations greater than 20 percent of average monthly streamflow in approximately 29 miles (46.7 km)
of anadromous fish streams from the discharge of dredged or fill material associated with mining the
Pebble deposit would affect anadromous fishery areas in the SFK, NFK, and UTC watersheds. As
described below, such streamflow changes would be likely to result in unacceptable adverse effects on
anadromous fishery areas if the discharges of dredged or fill material are located at the mine site or
elsewhere in the SFK, NFK, and UTC watersheds. The following conclusions and rationale directly support
the recommended prohibition described in Section 5.1 and the recommended restriction described in
Section 5.2.
4.2.4.7.1 Adverse Effects from Discharges of Dredged or Fill Material at the Mine
Site that Result in Streamflow Changes in Anadromous Fish Streams
EPA Region 10 has determined that the discharge of dredged or fill material for the construction and
routine operation of the 2020 Mine Plan, resulting in streamflow alterations greater than 20 percent of
average monthly streamflow in approximately 29 miles (46.7 km) of anadromous fish streams, would be
likely to have unacceptable adverse effects on anadromous fishery areas in the SFK and NFK
watersheds. This conclusion is based on the following factors: the large extent and magnitude of
streamflow changes in anadromous fish streams; the corresponding degradation of anadromous fish
streams, including spawning and rearing habitat for Coho, Chinook, Sockeye, and Chum salmon,
resulting from these streamflow changes; and the resulting erosion of both habitat complexity and
biocomplexity within the SFK and NFK watersheds, which are key to the abundance and stability of
salmon populations within these watersheds. Discharges of dredged or fill material anywhere at the
mine site for the construction and routine operation of a mine at the Pebble deposit would result in
downstream flow changes in the same anadromous fish streams that were characterized in the
evaluation of the 2020 Mine Plan (Figures 4-3 and 4-9; Table 4-4). These anadromous fish streams
support the same anadromous fish species and life stages as those that would be affected by the 2020 Mine
Plan (Section 3.3; USACE 2020a: Section 3.24). Thus, the same or greater levels of streamflow changes in
anadromous fish streams downstream of the mine site resulting from discharges of dredged or fill
material associated with developing the Pebble deposit also would be likely to have unacceptable
adverse effects on anadromous fishery areas. These conclusions support the recommended prohibition
described in Section 5.1.
4.2.4.7.2 Adverse Effects from Discharges of Dredged or Fill Material Elsewhere in
the SFK, NFK, and UTC Watersheds that Result in Streamflow Changes in
Anadromous Fish Streams
The 2020 Mine Plan represents only one configuration of a potential mine at the Pebble deposit. Mine
infrastructure could also be placed at other locations in the SFK, NFK, and UTC watersheds. The FEIS
considers the environmental impacts of discharges of dredged or fill material to construct components
associated with mining the Pebble deposit (e.g., TSFs) at other locations in these three watersheds
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(Section 2.1.2.2). For example, the FEIS indicates that placement of a bulk TSF with the necessary
capacity in other locations in the SFK, NFK, or UTC watersheds would result in similar or greater losses
of documented anadromous fish streams than the bulk TSF location proposed in the 2020 Mine Plan
(PLP 2018e: RFI 098). Coho, Chinook, Sockeye, and Chum salmon have been documented to rely on
habitat throughout the SFK, NFK, and UTC watersheds (Section 3.3.2.2). Because anadromous fish
streams directly support critical life history stages (e.g., spawning, rearing, migration) of at least one
anadromous fish species, shifting flow alterations from the NFK and SFK watersheds to the UTC
watershed would result in similar adverse effects on anadromous fishery areas. Thus, this
recommended determination also considers the significance of such streamflow alterations in
anadromous fish streams in the context of the SFK, NFK, and UTC watersheds.
The SFK, NFK, and UTC watersheds share several similarities in characteristics and aquatic resources.
The three watersheds are of similar size and share a headwater location. The broad components of these
watersheds are similar in terms of the types and abundance of aquatic habitats, their general physical
and chemical characteristics, and the organisms that use those habitats (Box 3-1). Additionally, in each
of the three watersheds, these components combine in different ways to create unique habitat mosaics,
which over thousands of years have resulted in local adaptation of anadromous fish populations to site-
specific conditions in each watershed. As a result, loss or degradation of anadromous fish streams in any
of the three watersheds would result in similar effects on anadromous fishery areas (e.g., degradation of
spawning and rearing habitat, erosion of habitat complexity and biocomplexity).
Given the similarity of the aquatic resources across the three watersheds and the expected impacts of
discharges of dredged or fill material associated with developing the Pebble deposit, EPA Region 10 has
determined that the discharge of dredged or fill material associated with mining the Pebble deposit
anywhere in the SFK, NFK, and UTC watersheds, resulting in streamflow alterations greater than 20
percent of average monthly streamflow in approximately 29 miles (46.7 km) of anadromous fish
streams, would be likely to have unacceptable adverse effects on anadromous fishery areas in these
watersheds. This conclusion is based on the same record and analysis used to evaluate the effects of the
2020 Mine Plan and the following factors: the presence of anadromous fish streams throughout the SFK,
NFK, and UTC watersheds, which directly support critical life history stages (e.g., spawning, rearing,
migration) of at least one anadromous fish species (Section 3.3); anadromous fish streams throughout
these watersheds that are currently among the least developed and least disturbed (i.e., closest to
pristine) habitat of this type in North America (Section 3.1); that these three watersheds have similar
amounts of total anadromous fish streams, as well as similar amounts of anadromous fish streams for
each of the five Pacific salmon species (Table 3-6, Figure 3-18); that anadromous fish streams across
these three watersheds function similarly to support multiple species and life stages of anadromous
fishes that are adapted to the unique set of environmental conditions each stream provides (Section
3.3); the large extent and magnitude of streamflow changes in anadromous fish streams; the
corresponding degradation of anadromous fish streams, including spawning and rearing habitat,
resulting from these streamflow changes (Section 4.2.4.5); and the resulting erosion of habitat
complexity and biocomplexity within the SFK, NFK, and UTC watersheds, both of which are key to the
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abundance and stability of salmon populations within these watersheds. This conclusion supports the
recommended restriction described in Section 5.2.
4.2.5 Summary of Effects on Fishery Areas from Discharges of Dredged
or Fill Material from Developing the Pebble Deposit
In summary, EPA Region 10 has determined that discharges of dredged or fill material into waters of the
United States for the construction and routine operation of the 2020 Mine Plan would be likely to result
in unacceptable adverse effects on anadromous fishery areas (Sections 4.2.1 through 4.2.4). EPA Region
10 has also determined that discharges of dredged or fill material associated with the development of
the Pebble deposit anywhere at the mine site that would result in the same or greater levels of loss or
streamflow changes as the 2020 Mine Plan also would be likely to have unacceptable adverse effects on
anadromous fishery areas, because such discharges would involve the same aquatic resources
characterized as part of the evaluation of the 2020 Mine Plan. Further, EPA Region 10 has determined
that discharges of dredged or fill material associated with future plans to mine the Pebble deposit would
be likely to result in unacceptable adverse effects on anadromous fishery areas in the SFK, NFK, and UTC
watersheds if the effects of such discharges are similar or greater in nature and magnitude to those
described in Sections 4.2.1 through 4.2.4.
4.3 Compliance with Relevant Portions of the Section
404(b)fl) Guidelines
EPA has broad discretion under CWA Section 404(c) to evaluate and determine whether a discharge
would result in an "unacceptable adverse effect" on fishery areas, including breeding and spawning
areas. EPA Region 10 has determined that discharges of dredged or fill material for the construction and
routine operation of the 2020 Mine Plan would be likely to have unacceptable adverse effects on
anadromous fishery areas, as described in Section 4.2.
EPA's Section 404(c) regulations at 40 CFR 231.2(e) provide that in evaluating the "unacceptability" of
effects, consideration should be given to the "relevant portions of the Section 404(b)(1) Guidelines." As
detailed in this section, evaluation of compliance with relevant portions of the Guidelines supports and
confirms EPA Region 10's determination that discharges of dredged or fill material for the construction
and routine operation of the 2020 Mine Plan would be likely to result in unacceptable adverse effects on
anadromous fishery areas.
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For the purposes of evaluating the unacceptability of effects from discharges of dredged or fill material
associated with the 2020 Mine Plan, EPA Region 10 evaluated the following portions of the Section
404(b)(1) Guidelines in the manner discussed in this section:
• Significant degradation of waters of the United States (40 CFR 230.10(c))
o Cumulative effects (40 CFR 230.11(g))
o Secondary effects (40 CFR 230.11(h))
• Minimization of adverse impacts on aquatic ecosystems (40 CFR 230.10(d))
4.3.1 Significant Degradation
The Section 404(b)(1) Guidelines direct that no discharge of dredged or fill material shall be permitted if
the discharge will cause or contribute to significant degradation of waters of the United States (40 CFR
230.10(c)). Of particular relevance, the Guidelines state that effects contributing to significant
degradation, considered individually or collectively, include the following:
1. Significantly adverse effects of the discharge of pollutants on human health or welfare,
including but not limited to effects on municipal water supplies, plankton, fish, shellfish,
wildlife, and special aquatic sites;
2. Significantly adverse effects of the discharge of pollutants on life stages of aquatic life and
other wildlife dependent on aquatic ecosystems, including the transfer, concentration, and
spread of pollutants or their byproducts outside of the disposal site through biological,
physical, and chemical processes;
3. Significantly adverse effects of the discharge of pollutants on aquatic ecosystem diversity,
productivity, and stability. Such effects may include, but are not limited to, loss of fish and
wildlife habitat or loss of the capacity of a wetland to assimilate nutrients, purify water, or
reduce wave energy; and
4. Significantly adverse effects of discharge of pollutants on recreational, aesthetic, and
economic values.
Findings of significant degradation related to proposed discharges must be based on appropriate factual
determinations, evaluations, and tests, as described in 40 CFR 230.11, with special emphasis on the
persistence and permanence of the effects evaluated.
EPA's regulations at 40 CFR 230.5 identify the stepwise process to assess the potential for significant
degradation. The assessment of impacts pursuant to subparts C through F (40 CFR 230.20-230.54)
informs the required factual determinations found in 40 CFR 230.11. The factual determinations, in turn,
inform the significant degradation finding and the finding of compliance or non-compliance with the
Guidelines. The Guidelines require the consideration of potential losses of environmental characteristics
or values resulting from direct, secondary, and cumulative impacts.
4,3,1,1 Direct and Secondary Effects of the 2020 Mine Plan
USACE provided its evaluation of the anticipated impacts from the discharge of dredged or fill material
associated with the 2020 Mine Plan under the 404(b)(1) Guidelines (40 CFR Part 230) in its Section 404
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ROD (USACE 2020b). USACE concluded the 2020 Mine Plan did not comply with the Section 404(b)(1)
Guidelines because impacts to waters of the United States "from discharges of dredged or fill material at
the mine site have been determined to cause significant degradation to the aquatic ecosystem"
(USACE 2020b: Page B2-2). USACE (2020b) concluded that the discharge of dredged or fill material
associated with the 2020 Mine Plan would result in significant adverse effects in all four effects
categories in 40 CFR 230.10(c):
• Human health or welfare (40 CFR 230.10 (c)(1)).
• Life stages of aquatic life and other wildlife dependent on aquatic ecosystems (40 CFR 230.10
(c)(2)).
• Aquatic ecosystem diversity, productivity, and stability (40 CFR 230.10 (c)(3)).
• Recreational, aesthetic, and economic values (40 CFR 230.10 (c)(4)).
USACE also concluded that "[t]he proposed avoidance, minimization, or compensatory mitigation
measures would not reduce the impacts to aquatic resources from the proposed project to below a level
of significant degradation" (USACE 2020b: Page B2-6).
EPA Region 10 also considered relevant portions of the Section 404(b)(1) Guidelines when evaluating
the unacceptability of the potential direct and secondary effects of the discharge of dredged or fill
material for the construction and routine operation of the 2020 Mine Plan, pursuant to EPA's Section
404(c) regulations at 40 CFR 231.2(e). The following discussion provides an overview of EPA Region
10's evaluation.
4,3,1,1,1 Adverse Effects of Loss of Anadromous Fish Streams
As discussed in Section 4.2.1, the discharge of dredged or fill material for the construction and routine
operation of the 2020 Mine Plan would result in the permanent loss of approximately 8.5 miles
(13.7 km) of anadromous fish streams. This loss represents approximately 13 percent of the
anadromous waters in the NFK watershed.
The anadromous fish streams that the discharge of dredged or fill material associated with the 2020
Mine Plan would permanently eliminate are ecologically valuable, particularly for juvenile salmon
(Section 3.2.4). Tributary NFK 1.190 is hydrologically connected with ponds and seasonally to
permanently inundated wetlands that result from beaver activity (USFWS 2 0 21).70 These features
provide excellent rearing habitat and important overwintering and flow velocity refugia for salmonids
(Section 3.2.4) (Nickelson et al. 1992, Cunjak 1996, Collen and Gibson 2001, Lang et al. 2006). The
permanent loss of anadromous fish streams resulting from discharges of dredged or fill material
associated with the 2020 Mine Plan would also result in the loss of salmon spawning habitat, which
would, in turn, result in the loss of marine-derived nutrients transported upstream by those fishes.
70 Connection to such floodplain wetland and pond habitats can greatly enhance the carrying capacity and
productive potential of anadromous fish streams (Section 3).
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Given the naturally low nutrient concentrations in these streams, these inputs of marine-derived
nutrients may be especially important in supporting biological production and, thus, food for juvenile
salmonids in these and downstream habitats (Section 3.3.4). These streams also support biological
production via inputs of leaf litter from deciduous shrubs and grasses in riparian areas (Meyer et al.
2007, Dekar et al. 2012), which help fuel the production of macroinvertebrates, a key food for salmonids
(Table 3-3). Thus, the anadromous fish streams that the 2020 Mine Plan would eliminate, as well as
similar habitats in the SFK, NFK, and UTC watersheds, play an important role in the life cycle of salmon.
These anadromous fish stream losses would adversely affect Coho and Chinook salmon populations
uniquely adapted to the spatial and temporal conditions of their natal streams (Section 3.3.1). Such
adaptation to local environmental conditions results in discrete, genetically distinct populations. This
biocomplexity—operating across a continuum of integrated, nested spatial and temporal scales—
depends on the abundance and diversity of aquatic habitats in the area and acts to stabilize overall
salmon production and fishery resources (Section 3.3.3) (Schindler et al. 2010, Schindler et al. 2018,
Brennan et al. 2019). The substantial spatial and temporal extent of stream habitat losses resulting from
the discharge of dredged or fill material associated with the 2020 Mine Plan suggest that these losses
would reduce the overall capacity and productivity of Coho and Chinook salmon in the entire NFK
watershed.
The 8.5 miles (13.7 km) of anadromous fish streams that would be lost are mapped as upper perennial
streams (PLP 2020b) and considered special aquatic sites with riffle/pool complexes (USACE 2020b).
Under Subpart E of the Guidelines (40 CFR 230.41 and 230.45), special aquatic sites "are generally
recognized as significantly influencing or positively contributing to the general overall environmental
health or vitality of the entire ecosystem of a region" (40 CFR 230.3 (m)). Loss of these 8.5 miles (13.7
km) of anadromous fish streams is significant due to the effects on fishery areas. These special aquatic
sites act as fish habitat and as sources of groundwater inputs, nutrients, and other subsidies important
for salmon productivity (Section 3.2.4). Their loss would result in significant adverse effects on fish
(40 CFR 230.10(c)(1)), life stages of anadromous fish (40 CFR 230.10(c)(2)), anadromous fish habitat,
and aquatic ecosystem diversity, productivity, and stability (40 CFR 230.10(c)(3)).
Further, based on the record, EPA Region 10 has determined that eliminating approximately 8.5 miles
(13.7 km) of anadromous fish streams anywhere in the SFK, NFK, and UTC watersheds, due to the
discharge of dredged or fill material associated with mining the Pebble deposit, would result in similar
significantly adverse effects on anadromous fish habitats and populations. This conclusion is based on
the following factors: the presence of anadromous fish streams throughout the SFK, NFK, and UTC
watersheds, which directly support critical life history stages (e.g., spawning, rearing, migration) of at
least one anadromous fish species (Section 3.3); anadromous fish streams throughout these watersheds
that are currently among the least developed and least disturbed (i.e., closest to pristine) habitat of this
type in North America (Section 3.1); that these three watersheds have similar amounts of total
anadromous fish streams, as well as similar amounts of anadromous fish streams for each of the five
Pacific salmon species (Table 3-6, Figure 3-18); that anadromous fish streams across these three
watersheds function similarly to support multiple species and life stages of anadromous fishes that are
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Basis for Recommended Determination
adapted to the unique set of environmental conditions each stream provides (Section 3.3); the large
amount of permanent loss of anadromous fish habitat; the degradation of additional downstream
anadromous fish habitat due to the loss of ecological subsidies provided by the eliminated anadromous
fish streams; and the resulting erosion of habitat complexity and biocomplexity within the SFK, NFK, and
UTC watersheds, both of which are key to the abundance and stability of salmon populations in these
watersheds.
4,3,1,1,2 Adverse Effects of Loss of Additional Streams that Support Anadromous
Fish Streams
As discussed in Section 4.2.2, the discharge of dredged or fill material for the construction and routine
operation of the 2020 Mine Plan would result in the permanent loss of an additional 91 miles (147 km)
of streams that support anadromous fish streams, in the SFK and NFK watersheds. The permanent loss
of additional streams would result in reduced stream productivity in downstream reaches of the SFK
and NFK due to the loss of physical, chemical, and biological inputs that would no longer be provided to
downstream channels. Most of these permanently lost streams (77.0 miles [124 km]) are mapped as
upper perennial streams (PLP 2020b) and considered special aquatic sites (USACE 2020b). The loss of
upper perennial streams is likely to reduce water-holding capacity of the watershed by eliminating
stream pools and meanders, thereby degrading downstream anadromous fish habitat through the
reduced capacity for aeration and filtration (USACE 2020b).
The permanent loss of additional streams would adversely affect downstream habitat for salmon and
other fish species (Section 3.2.4, Figures 4-3 through 4-5). These downstream waters are ecologically
important and provide spawning and rearing habitat for Coho, Chinook, Sockeye, and Chum salmon in
the SFK and NFK watersheds (Figures 4-3 and 3-5 through 3-8). Permanent loss of these habitats would
adversely affect genetically distinct populations of Sockeye Salmon in the Koktuli River (including the
SFK and NFK), as well as Coho and Chinook salmon populations that may be uniquely adapted to the
spatial and temporal conditions of their natal streams (Section 3.3.1). As explained for the loss of
8.5 miles (13.7 km) of anadromous fish streams, the loss and degradation of downstream anadromous
fishery areas in the SFK and NFK watersheds that would result from elimination of 91 miles (147 km) of
additional streams would further erode habitat complexity and biocomplexity within these watersheds.
The diversity of salmon habitats and associated salmon population diversity helps buffer these salmon
populations from sudden and extreme changes in abundance and ultimately maintain their stability and
productivity.
These losses would result in significant adverse effects on fish and special aquatic sites (40 CFR
230.10(c)(1)), life stages of anadromous fish (40 CFR 230.10(c)(2)), anadromous fish habitat, and
aquatic ecosystem diversity, productivity, and stability (40 CFR 230.10(c)(3)). These impacts are
significant due to the effects on downstream anadromous fishery areas (Section 4.2.2) and the extensive
loss of special aquatic sites, which are important sources of groundwater inputs, nutrients, and other
subsidies crucial to salmon productivity (Section 3.2.4).
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Further, based on the same record, EPA Region 10 has determined that eliminating approximately 91
miles (147 km) of streams that support anadromous fish streams anywhere in the SFK, NFK, and UTC
watersheds, due to the discharge of dredged or fill material associated with mining the Pebble deposit,
would result in similar significantly adverse effects on anadromous fish habitats and populations. This
conclusion is based on the following factors: headwater streams throughout the SFK, NFK, and UTC
watersheds that are currently among the least developed and least disturbed (i.e., closest to pristine)
habitat of this type in North America (Section 3.1) and play an important role in supporting Pacific
salmon populations (Section 3.2); that these three watersheds have similar amounts of total stream
miles (relative to their watershed areas) (Table 3-6); that headwater streams across these three
watersheds function similarly to support productive fishery areas for anadromous fishes (Section 3.3);
the large amount of outright loss of stream habitat and the crucial role that these headwater streams
play in providing ecological subsidies to downstream anadromous fish streams; the degradation of
downstream anadromous fish streams from the loss of ecological subsidies provided by the lost
headwater streams; and the resulting erosion of habitat complexity and biocomplexity in the SFK, NFK,
and UTC watersheds, both of which are key to the abundance and stability of salmon populations within
these watersheds.
4,3,1,1,3 Adverse Effects of Loss of Wetlands and Other Waters that Support
Anadromous Fish Streams
As discussed in Section 4.2.3, the discharge of dredged or fill material for the construction and routine
operation of the 2020 Mine Plan would result in the permanent loss of approximately 2,108 acres
(8.5 km2) of wetlands and other waters, in the SFK and NFK watersheds.
Approximately 2,047 acres (8.3 km2) of this permanently lost habitat are wetlands, a special aquatic site
under the Guidelines. Wetlands and other waters that would be permanently lost play a critically
important role in the life cycles of anadromous fishes in the SFK and NFK watersheds (Section 3.2.3)
(PLP 2011: Appendix 15.1.D), given that "...all wetlands are important to the greater function and value
of ecosystems and subsistence cultures they support" (USACE 2020a: Page 3.22-8). Moreover, wetlands
and other waters affected by the 2020 Mine Plan "possess unique ecological characteristics of
productivity, habitat, wildlife protection, and other important and easily disrupted values" (USACE
2020a: Page 3.22-1). The permanent removal of wetlands and other waters would destroy habitat, cause
mortality of aquatic organisms, and reduce the collective functional capacity and value of wetlands and
other waters across multiple watersheds. These permanent losses also would cause the displacement,
injury, and/or mortality of species that rely on these aquatic environments for all or part of their life
cycles (USACE 2020a: Section 4.22).
The discharge of dredged or fill material to these aquatic resources would be expected to reduce the
biological productivity of wetland ecosystems by smothering, dewatering, permanently flooding, or
altering substrate elevation or the periodicity of water movement (USACE 2020a: Section 4.22). The loss
of such waters would eliminate structurally complex and thermally and hydraulically diverse habitats,
including crucial overwintering areas, that are essential to rearing salmonids.
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In addition to the direct loss of habitat, loss of these wetlands and other waters would result in a total
loss of their functions that support fish habitat, such as supplying nutrients and organic material and
maintaining baseflows, in both abutting and downstream waters (Section 3.2.4). Downstream waters
that would be degraded by the elimination of wetlands and other waters at the mine site are ecologically
important and provide rearing and spawning habitat for Coho, Chinook, Sockeye, and Chum salmon in
the SFK and NFK watersheds (Figures 3-5 through 3-8). This degradation of downstream anadromous
fish streams would adversely affect genetically distinct populations of Sockeye Salmon in the Koktuli
River (including the SFK and NFK) and Coho and Chinook salmon populations that may be uniquely
adapted to the spatial and temporal conditions of their natal streams (Section 3.3.1). As explained for
the loss of 8.5 miles (13.7 km) of anadromous fish streams, the loss and degradation of downstream
anadromous fishery areas in the SFK and NFK watersheds that would result from elimination of
2,108 acres (8.5 km2) of wetlands and other waters would further erode both habitat complexity and
biocomplexity within these watersheds. This diversity of salmon habitats and associated salmon
population diversity helps buffer these salmon populations from sudden and extreme changes in
abundance and ultimately maintain their stability and productivity.
These losses would result in significant adverse effects on fishes and special aquatic sites (40 CFR
230.10(c)(1)), life stages of anadromous fishes (40 CFR 230.10(c)(2)), anadromous fish habitat, and
aquatic ecosystem diversity, productivity, and stability (40 CFR 230.10(c)(3)). These losses are
significant due to their effects on downstream anadromous fishery areas and the extensive loss of
special aquatic sites, which are key sources of groundwater inputs, nutrients, and other subsidies
important for salmon productivity (Section 3.2).
Further, based on the same record, EPA Region 10 has determined that eliminating approximately 2,108
acres (8.5 km2) of wetlands and other waters anywhere in the SFK, NFK, and UTC watersheds, due to the
discharge of dredged or fill material associated with mining the Pebble deposit, would result in similar
significantly adverse effects on anadromous fish habitats and populations. This conclusion is based on
the following factors: headwater wetlands and other waters throughout the SFK, NFK, and UTC
watersheds that are currently among the least developed and least disturbed (i.e., closest to pristine)
habitat of this type in North America (Section 3.1) and play an important role in supporting Pacific
salmon populations (Section 3.2); that these three watersheds have similar amounts and types of
wetlands (Table 3-2); that headwater wetlands and other waters across these three watersheds function
similarly to support productive fishery areas for anadromous fishes (Section 3.3); the large amount of
outright loss of wetlands and other waters; the importance of wetlands and other waters to salmon
populations, both as habitat and as sources of groundwater inputs, nutrients, and other subsidies
important to salmon productivity in downstream waters; the degradation of downstream anadromous
fish streams from the loss of ecological subsidies provided by the lost headwater wetlands and other
waters; and the resulting erosion of habitat complexity and biocomplexity in the SFK, NFK, and UTC
watersheds, both of which are key to the abundance and stability of salmon populations in these
watersheds.
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Basis for Recommended Determination
4,3,1,1,4 Adverse Effects from Changes in Streamflow in Downstream
Anadromous Fish Streams
As discussed in Section 4.2.4, the discharge of dredged or fill material for the construction and routine
operation of the 2020 Mine Plan would result in streamflow alterations greater than 20 percent of
average monthly streamflow from natural conditions in approximately 29 miles (46.7 km) of
documented anadromous fish streams in the SFK and NFK watersheds. These changes in streamflow
would alter the natural flow regimes of these systems (Poff et al. 1997) and could result in major
changes in ecosystem structure and function (Richter et al. 2012), which could significantly reduce the
extent and quality of anadromous fish habitats downstream of the mine site. Streamflow reductions
would reduce habitat availability for salmon and other fishes, particularly during low-streamflow
periods (West et al. 1992, Cunjak 1996); reduce macroinvertebrate production (Chadwick and Huryn
2007); and increase stream habitat fragmentation due to increased frequency and duration of stream
drying. Increases in streamflow above baseline levels could result in increased scour and transport of
gravels, affecting important salmon spawning areas (Brekken et al. 2022). Increased streamflows could
also adversely affect distributions of water velocities favorable for various fish life stages (Piccolo et al.
2008, Donofrio et al. 2018).
As with the habitat losses and degradation described previously (Section 4.3.1.1) and in Sections 4.2.1
through 4.2.3, streamflow alterations would adversely affect downstream habitats for salmon and other
fish species (Section 3.2.4, Figures 4-3 through 4-5). These downstream waters are ecologically
important and provide spawning and rearing habitat for Coho, Chinook, Sockeye, and Chum salmon in
the SFK and NFK watersheds (Figures 4-3 and 3-5 through 3-8).
These streamflow changes would result in significant adverse effects on fishes and special aquatic sites
(40 CFR 230.10(c)(1)), on life stages of anadromous fishes (40 CFR 230.10(c)(2)), anadromous fish
habitat, and aquatic ecosystem diversity, productivity, and stability (40 CFR 230.10(c)(3)). These
streamflow changes would degrade downstream anadromous fish streams, adversely affecting
genetically distinct populations of Sockeye Salmon in the Koktuli River (including the SFK and NFK) and
Coho and Chinook salmon populations that may be uniquely adapted to the spatial and temporal
conditions of their natal streams (Section 3.3.1). As explained for the loss of 8.5 miles (13.7 km) of
anadromous fish streams, the loss and degradation of downstream anadromous fishery areas in the SFK
and NFK watersheds that would result from streamflow alterations greater than 20 percent of average
monthly streamflow from natural conditions in approximately 29 miles (46.7 km) of anadromous fish
streams would further erode both habitat complexity and biocomplexity within these watersheds. The
diversity of salmon habitats and associated salmon population diversity helps buffer these salmon
populations from sudden and extreme changes in abundance and ultimately maintain their stability and
productivity.
Further, based on the same record, EPA Region 10 has determined that streamflow alterations greater
than 20 percent of average monthly streamflow in approximately 29 miles (46.7 km) of anadromous fish
streams anywhere in the SFK, NFK, and UTC watersheds, due to the discharge of dredged or fill material
associated with mining the Pebble deposit, would result in similar significantly adverse effects on
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Basis for Recommended Determination
anadromous fish habitats and populations. This conclusion is based on the following factors: the
presence of anadromous fish streams throughout the SFK, NFK, and UTC watersheds, which directly
support critical life history stages (e.g., spawning, rearing, migration) of at least one anadromous fish
species (Section 3.3); anadromous fish streams throughout these watersheds that are currently among
the least developed and least disturbed (i.e., closest to pristine) habitat of this type in North America
(Section 3.1); that these three watersheds have similar amounts of total anadromous fish streams, as
well as similar amounts of anadromous fish streams for each of the five Pacific salmon species (Table 3-
6, Figure 3-18); that anadromous fish streams across these three watersheds function similarly to
support multiple species and life stages of anadromous fishes that are adapted to the unique set of
environmental conditions each stream provides (Section 3.3); the large extent and magnitude of
streamflow changes in anadromous fish streams; the corresponding degradation of anadromous fish
streams, including spawning and rearing habitat, resulting from these streamflow changes (Section
4.2.4.5); and the resulting erosion of habitat complexity and biocomplexity in the SFK, NFK, and UTC
watersheds, both of which are key to the abundance and stability of salmon populations in these
watersheds.
4,3,1,1,5 Conclusion
EPA Region 10 has determined that direct and secondary impacts of the discharge of dredged or fill
material for the construction and routine operation of the 2020 Mine Plan, as well as discharges that
would result in effects similar or greater in nature and magnitude to the 2020 Mine Plan, would result in
significant degradation under the Section 404(b)(1) Guidelines. These findings are based on the
significantly adverse effects of the discharge of dredged or fill material on special aquatic sites; life
stages of anadromous fishes; anadromous fish habitat; and aquatic ecosystem diversity, productivity,
and stability under the Section 404(b)(1) Guidelines.
4,3,1,2 Cumulative Effects of Mine Expansion
EPA Region 10 recognizes that losses and degradation of these aquatic resources could be even more
pronounced when the extensive cumulative impacts on the aquatic ecosystem expected to occur with
successive stages of mine expansion are considered. The Guidelines describe as "fundamental" 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" (40 CFR 230.1(c)). The Guidelines require consideration of cumulative impacts in determining
whether a project complies with the significant degradation prohibition of 40 CFR 230.10(c). The
Guidelines state that "cumulative effects attributable to the discharge of dredged or fill material...should
be predicted to the extent reasonable and practical." 40 CFR 230.11(g)(2). The Guidelines describe
"cumulative effects" as follows:
The changes in an aquatic ecosystem that are attributable to the collective effect of a number
of individual discharges of dredged or fill material. Although the impact of a particular
discharge may constitute a minor change in itself, the cumulative effect of numerous such
piecemeal changes can result in a major impairment of the water resources and interfere
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Basis for Recommended Determination
with the productivity and water quality of existing aquatic ecosystems (40 CFR
230.11(g)(1)).
USACE considered expansion of the 2020 Mine Plan (hereafter the Expanded Mine Scenario) a
reasonably foreseeable future action and, therefore, evaluated the Expanded Mine Scenario for
cumulative effects during its CWA Section 404 permitting process (Figure 4-12) (USACE 2020a: Section
4.1).71 PLP's 2021 Preliminary Economic Assessment evaluated mine expansion as part of its projected
production economics, indicating that mine expansion continues to be reasonably foreseeable
(Kalanchey et al. 2021). The Expanded Mine Scenario is not part of the 2020 Mine Plan, has not
otherwise been proposed, and would require additional and separate permitting (USACE 2020a:
Section 4.1, PLP 2018c: RFI 062). Therefore, it is not a basis for this recommended determination.
EPA Region 10 has concluded that the direct and secondary impacts of the discharge of dredged or fill
material for the construction and routine operation of the 2020 Mine Plan, as well as discharges that
would result in effects similar or greater in nature and magnitude to the 2020 Mine Plan, would result in
significant degradation under the Section 404(b)(1) Guidelines. However, the Guidelines also require
EPA Region 10 to evaluate cumulative effects.
Under the Expanded Mine Scenario, approximately 8.6 billion tons of ore would be mined (Kalanchey et
al. 2021) over 58 years, with additional milling occurring over another 20 to 40 years, for a total of 78 to
98 years of additional activity at the mine site (USACE 2020a: Table 4.1-2). The Expanded Mine Scenario
would use infrastructure included in the 2020 Mine Plan, such as the transportation facilities, power
plant, and natural gas pipeline facilities, but would include a larger open pit; development of additional
tailings storage, water storage, and waste rock storage facilities; and a concentrate pipeline and
deepwater loading facility (USACE 2020a: Section 4.1).
The following subsections evaluate the cumulative effects on fishery areas associated with the mine site
of the 2020 Mine Plan and the Expanded Mine Scenario. The following analysis does not consider
associated facilities and transportation corridors.
71 For the purposes of the FEIS, "cumulative effects are interactive, synergistic, or additive effects that would result
from the incremental impact of the proposed action when added to other past, present, and reasonably foreseeable
future actions (RFFAs) regardless of what agency (federal or non-federal) or person undertakes those other actions
(40 CFR Part 1508.7)" (USACE 2020a: Page 4.1-3).
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Basis for Recommended Determination
Figure 4-12. Mine site cumulative impacts under the Expanded Mine Scenario. Figure 4.22-5 from the FEIS (USAGE
2020a: Section 4.22)
Sources: PLP 2019-RFI116; PLP 2019 RFI-153;
PLP 2020-RFI082C
US Army Corps
of Engineers
$
Indirect Impact NWI Classes
( ] Drawdown (High) Bryophyte
Drawdown (Moderate) Aquatic Bed
Fragmented I ) Herbaceous
Fugitive Dust I ] Broad Leaved Deciduous Shrubs
'... J Deciduous Forest
Evergreen Shrubs
Evergreen Forest
Ponds
Lakes
Rivers/Streams (Intermittent)
Rivers/Streams (Perennial)
Wetland/Upland Mosaic
Uplands/Mapped Wetlands Extent
•V-T". Watershed
Cj-I Alternative 1a
Expanded Mine Scenario
MINE SITE CUMULATIVE IMPACTS
UNDER AN EXPANDED MINE SCENARIO
PEBBLE PROJECT EIS
FIGURE 4.22-5
Recommended Determination
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Basis for Recommended Determination
4,3,1,2,1 Cumulative Effects of Loss of Anadromous Fish Streams
As discussed in Section 4.2.1, the 2020 Mine Plan would result in the permanent loss of approximately
8.5 miles (13.7 km) of streams in the NFK watershed with documented occurrence of anadromous
fishes, specifically Coho and Chinook salmon. The Expanded Mine Scenario would eliminate an
additional 35 miles (56.3 km) of streams in the SFK and UTC watersheds with documented occurrence
of anadromous fishes (Figures 4-13 and 4-14) (USACE 2020a: Section 4.24). These additional stream
losses represent 25.7 percent of anadromous fish streams across the SFK and UTC watersheds
combined.72 The Expanded Mine Scenario would also result in the complete loss of 544 acres (2.2 km2)
of lakes and ponds with documented anadromous fish use (Giefer and Graziano 2022), including the
150-acre (0.6-km2) Frying Pan Lake in the SFK watershed. Frying Pan Lake, which would be inundated
by the south collection pond, provides rearing habitat for Sockeye Salmon, Arctic Grayling, Northern
Pike, whitefish, stickleback, and sculpin. Across the SFK, NFK, and UTC watersheds, the Expanded Mine
Scenario would cause losses to documented Sockeye, Coho, Chinook, and Chum salmon habitat
(Table 4-6) (USACE 2020a: Section 4.24).
Table 4-6. Anadromous stream habitat that would be permanently lost in the South Fork Koktuli
River, North Fork Koktuli River, and Upper Talarik Creek watersheds under the 2020 Mine Plan plus
Spawning
0.4
3.7
9.2
13.4
Coho Salmon
Rearing
8.0
7.1
16.9
32.0
Present
1.3
-
0.4
1.7
Total Lost Habitat
8.0
7.1
17.8
32.8
Spawning
-
-
3.6
3.6
Chinook Salmon
Rearing
2.7
2.3
6.6
12.4
Present
-
1.4
2.7
3.3
Total Lost Habitat
2.7
3.7
7.3
13.7
Spawning
-
-
4.8
4.8
Sockeye Salmon
Rearing
1.6
-
3.7
5.3
Present
-
-
1.1
1.1
Total Lost Habitat
1.6
-
6.2
7.8
Spawning
-
-
0.5
0.5
Chum Salmon
Present
1.2
-
-
1.2
Total Lost Habitat
1.2
-
0.5
1.6
Notes:
a From the Anadromous Waters Catalog (Giefer and Graziano 2022).
b Salmon habitat types overlap and may be coincident, so these numbers cannot be added together.
72 The SFK watershed contains 60.0 miles of anadromous waters and the UTC watershed contains 76.2 miles of
anadromous waters, based on AWC and PLP stream layers (USACE 2020a: Section 3.24).
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Basis for Recommended Determination
Figure 4-13. Streams, rivers, and lakes with documented salmon use overlain with the
footprints of the Pebble 2020 Mine Plan and the Expanded Mine Scenario. Species
distributions are based on the Anadromous Waters Catalog (Giefer and Graziano 2022).
NHD Streams and
Waterbodies
2020 Mine Footprint
Expanded Mine
Footprint
South Fork Koktuli,
j North Fork Koktuli, and
¦ Upper Talarik Creek
Watersheds
Nushagak and Kvichak
Watersheds
X
0 2 4
1 1 i r I i i i 1
Miles
0 3 6
1 I I I I I I I I
Kilometers
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Basis for Recommended Determination
Figure 4-14. Streams, rivers, and lakes with documented salmon use in the South Fork Koktuli
River, North Fork Koktuli River, and Upper Talarik Creek watersheds, downstream of the
Pebble 2020 Mine Plan and Expanded Mine Scenario. Species distributions are based on the
Anadromous Waters Catalog (Giefer and Graziano 2022).
Coho
Chinook
Sockeye
Chum
Pink
2020 Mine Footprint
Expanded Mine
Footprint
South Fork Koktuli,
i—i
North Fork Koktuli, and
I i
Upper Talarik Creek
Watersheds
Nushagak and Kvichak
Watersheds
N
~
0
l_l
3
i i 1 i i
6
l_|
Miles
0
1
5
i i 1 i i
10
i_!
Kilometers
KVICHAK
lliamna Lake
NUSHAGAK
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Basis for Recommended Determination
The 2020 Mine Plan and the Expanded Mine Scenario would cumulatively eliminate nearly 33 miles
(53.1 km) of documented Coho Salmon habitat, 13.7 miles (22 km) of documented Chinook Salmon
habitat, and 7.8 miles (12.6 km) of documented Sockeye Salmon habitat across the SFK, NFK, and UTC
watersheds. Each species would lose both spawning and rearing habitat (Table 4-6). The 2020 Mine Plan
and the Expanded Mine Scenario would also cumulatively eliminate 1.6 miles (2.6 km) of Chum Salmon
habitat across the three watersheds.
Eliminated and dewatered habitat likely would permanently lose the ability to support salmon. As
discussed for the NFK watershed in Section 4.2.1, the substantial spatial and temporal extent of stream
habitat losses under the Expanded Mine Scenario would also reduce the overall capacity and
productivity of Coho, Chinook, and Sockeye salmon in the SFK and UTC watersheds. The genetic
structure of these populations varies across fine spatial scales, and such extensive habitat losses within
three watersheds would adversely affect genetically distinct populations of Sockeye Salmon in the
Koktuli River (including the SFK and NFK) and the UTC, as well as Coho and Chinook salmon populations
in these watersheds that may be uniquely adapted to the spatial and temporal conditions of their natal
streams (Section 3.3.1). Coho Salmon may be particularly susceptible to extirpation through the loss of
such populations (Olsen et al. 2003). Losses of small Chinook Salmon populations with diverse life
histories have been reported in other regions (Lindley et al. 2009), with resulting impacts on overall
population resilience (Healey 1991). Because Coho and Chinook salmon are the rarest of the Pacific
salmon species, losses that eliminate unique local populations could result in the loss of significant
amounts of overall genetic variability. The extensive habitat losses associated with the Expanded Mine
Scenario would likely put such populations at risk.
The loss of 8.5 miles (13.7 km) of documented anadromous fish streams associated with the 2020 Mine
Plan would already represent an unprecedented loss of documented anadromous fish streams in the
context of the CWA Section 404 regulatory program in Alaska (Section 4.2.1). The loss of an additional
35 miles (56.3 km) of documented anadromous fish streams associated with the Expanded Mine
Scenario would represent an extraordinary loss of anadromous fish habitat, which would be
compounded by the complete loss of 544 acres (2.2 km2) of lakes and ponds with documented
anadromous fish use, including the destruction of the 150-acre (0.6-km2) Frying Pan Lake.
4,3,1,2,2 Cumulative Effects of Loss of Additional Streams that Support
Anadromous Fish Streams
As discussed in Sections 4.2.1 and 4.2.2, the discharge of dredged or fill material for the construction and
routine operation of the 2020 Mine Plan would eliminate 8.5 miles (13.7 km) of anadromous fish
streams and 91 miles (147 km) of additional streams that support anadromous fish streams. The
discharge of dredged or fill material for the Expanded Mine Scenario would eliminate 35 additional
miles (56.3 km) of anadromous fish streams and result in the permanent loss of an additional
295.5 miles (475.6 km) of streams that support downstream anadromous fish streams across the SFK
and UTC watersheds, most of which would be perennial streams (USACE 2020a: Table 4.22-40). These
permanent losses would substantially increase adverse impacts on anadromous fishes in the SFK and
UTC watersheds (USACE 2020a: Section 4.22). Many of the eliminated streams likely contain
Recommended Determination
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Section 4
Basis for Recommended Determination
anadromous fish habitat that has not yet been documented (Sections 3.2.4 and 4.2.1) but may be
particularly valuable for juvenile salmonids. The unprecedented habitat losses in the SFK and UTC
watersheds that would result from the Expanded Mine Scenario would exacerbate any unacceptable
adverse effects on salmon and other fish populations caused by the 2020 Mine Plan.
Rainbow Trout, Dolly Varden, Arctic Grayling, Northern Pike, Ninespine Stickleback, and Slimy Sculpin also
would lose additional habitat under the Expanded Mine Scenario (Figures 4-15 through 4-18). The
Expanded Mine Scenario would eliminate Rainbow Trout habitat beyond the NFK watershed and include
losses in the UTC watershed (Figures 4-15 and 4-17). The Expanded Mine Scenario would eliminate Dolly
Varden habitat beyond the NFK watershed and include losses in the SFK and UTC watersheds (Figures
4-15 and 4-17). The Expanded Mine Scenario would increase habitat losses for Arctic Grayling, Northern
Pike, Ninespine Stickleback, and Slimy Sculpin in the SFK watershed. The Expanded Mine Scenario would
also eliminate habitat for Arctic Grayling, Ninespine Stickleback, and Slimy Sculpin in the UTC watershed
(Figures 4-15 through 4-18). In addition to direct habitat losses, increased loss of stream habitat under the
Expanded Mine Scenario would substantially alter streamflows and other ecological subsidies provided to
downstream fish habitats in the SFK and UTC watersheds (Figures 4-14 and 4-18). Associated reductions
in streamflow to downstream fishery areas would likely reduce the extent and frequency of stream
connectivity to off-channel habitats, as well as alter the thermal regimes of downstream habitats (Section
4.2.4). These habitats also would no longer support or export macroinvertebrates, an important food
source for juvenile salmon and other fish species.
Recommended Determination
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Basis for Recommended Determination
Figure 4-15. Reported Arctic Grayling, Rainbow Trout, and Dolly Varden occurrence overlain
with the footprints of the Pebble 2020 Mine Plan and the Expanded Mine Scenario. Species
distributions are based on the Alaska Freshwater Fish Inventory (ADF&G 2022a).
0
A
O
Arctic Grayling
Rainbow Trout
Dolly Varden
NHD Streams and
Waterbodies
2020 Mine Footprint
Expanded Mine
Footprint
South Fork Koktuli,
North Fork Koktuli, and
Upper Talarik Creek
Watersheds
Nushagakand Kvichak
River Watersheds
t ¦ >
I j i ' I i l i J
Miles
0 3 6
1 i i i I j i l
Kilometers
Recommended Determination
December 2022
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Section 4
Basis for Recommended Determination
Figure 4-16. Reported occurrence of other resident fish species overlain with the footprints of
the Pebble 2020 Mine Plan and the Expanded Mine Scenario. Species distributions are based
on the Alaska Freshwater Fish inventory (ADF&G 2022a).
0
Northern Pike
o
Stickleback
o
Sculpin
NHD Streams and
*
Waterbodies
2020 Mine Footprint
Expanded Mine
Footprint
South Fork Koktuli,
i i
North Fork Koktuli, and
i i
Upper Talarik Creek
Watersheds
pi
Nushagak and Kvichak
Watersheds
Kilometers
^ 1 V. *
Recommended Determination
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Section 4
Basis for Recommended Determination
Figure 4-17. Reported Arctic Grayling, Rainbow Trout, and Dolly Varden occurrence in the
South Fork Koktuli River, North Fork Koktuli River, and Upper Talarik Creek watersheds,
downstream of the Pebble 2020 Mine Plan and Expanded Mine Scenario. Species distributions
are based on the Alaska Freshwater Fish Inventory (ADF&G 2022a).
NUSHAGAK
KVICHAK
lliamna Lake
A
O
Rainbow Trout
Dolly Varden
nn
2020 Mine Footprint
Expanded Mine
Footprint
South Fork Koktuli,
North Fork Koktuli, and
Upper Talarik Creek
Watersheds
Nushagakand Kvichak
River Watersheds
N
A
0
u
3
i i 1 i i
6
U
Miles
0
Li
5
i i i i i
10
«]
Kilometers
Recommended Determination
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Section 4
Basis for Recommended Determination
Figure 4-18. Reported occurrence of other non-salmon fish species in the South Fork Koktuli
River, North Fork Koktuli River, and Upper Talarik Creek watersheds, downstream of the
Pebble 2020 Mine Plan and Expanded Mine Scenario. Species distributions are based on the
Alaska Freshwater Fish Inventory (ADF&G 2022a).
0
Northern Pike
0
Stickleback
o
Sculpin
2020 Mine Footprint
Expanded Mine
Footprint
South Fork Koktuli,
i—i
North Fork Koktuli, and
i i
Upper Talarik Creek
Watersheds
Nushagak and Kvichak
Watersheds
N
A
0
Lj
A
3
1 > 1 1 1
6
_)
Miles
0
l_l
5
iili
10
i_l
Kilometers
KVICHAK
lliamna Lake
NUSHAGAK
Recommended Determination
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Section 4
Basis for Recommended Determination
4.3.1.2.3 Cumulative Effects of Loss of Wetlands and Other Waters that Support
Anadromous Fish Streams
In addition to the 2,108 acres (8.5 km2) of wetlands and other waters that would be permanently lost
under the 2020 Mine Plan, the Expanded Mine Scenario would result in the permanent loss of an
additional 8,756 acres (35.4 km2) of wetlands and other waters in the SFK and UTC watersheds,
primarily affecting broad-leaved deciduous shrub and herbaceous type wetlands (Figure 4-12)
(USACE 2020a: Table 4.22-40). The greatest losses of wetlands and other waters under the Expanded
Mine Scenario would occur in the Headwaters Koktuli River (i.e., the SFK, NFK, and Middle Koktuli River
HUC-12 watersheds) and UTC watersheds, with losses of wetlands and other waters in these watersheds
increasing from 6 percent73 under the 2020 Mine Plan to 23 percent (USACE 2020a: Section 4.22). The
unprecedented loss of thousands of acres of wetlands under the Expanded Mine Scenario would
eliminate nutrient-rich, structurally complex, and thermally and hydraulically diverse habitats—
including crucial overwintering areas—that are essential to rearing salmonids (EPA 2014: Chapter 7).
Coho, Chinook, Sockeye, and Chum salmon would be adversely affected under the Expanded Mine
Scenario (Figures 4-13 and 4-14). The Expanded Mine Scenario would also result in a loss or reduction
of water, nutrient, detritus, and macroinvertebrate exports to downstream areas, the losses of which
would affect downstream food webs. These losses, of an even greater scope and scale than losses
anticipated from the 2020 Mine Plan, would reduce the overall capacity and productivity of Coho,
Chinook, Sockeye, and Chum salmon across the SFK, NFK, and UTC watersheds.
In addition to salmon, Rainbow Trout, Arctic Grayling, and Northern Pike rear in these wetland areas;
Northern Pike also spawn in these habitats (Figures 4-15 and 4-16). These species support both
subsistence and recreational fisheries in downstream areas. Because these species can move significant
distances across diverse freshwater habitats throughout their life cycles, large losses of wetland rearing
habitat could adversely affect these downstream fisheries.
4.3.1.2.4 Cumulative Effects of Additional Degradation of Streams, Wetlands, and
Other Waters Beyond the Mine Site Footprint
The 2020 Mine Plan would be expected to degrade additional wetlands, streams, and other waters
beyond the mine site footprint due to dewatering, fragmentation, and fugitive dust. These secondary
effects of the discharge of dredged or fill material from construction and routine operation of the 2020
Mine Plan would result in adverse impacts to approximately 845 additional acres of wetlands and other
waters (3.4 km2) and 29.9 miles (48.1 km) of streams at the mine site (PLP 2020b, USACE 2020b).
Impacts from dewatering, fragmentation, and fugitive dust would increase under the Expanded Mine
Scenario and further reduce the quality and extent of fish habitats in the SFK and UTC watersheds
(USACE 2020a: Section 4.22).
Under the Expanded Mine Scenario, aquatic resources could experience multiple secondary impacts,
resulting in overlap in the area or miles affected when accounting for the effects of dewatering, habitat
73 In its comments on the proposed determination, PLP indicated that following publication of the FEIS it provided
information to USACE that this value is 4.8 percent based on updated mapping results.
Recommended Determination
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Section 4
Basis for Recommended Determination
fragmentation, and fugitive dust deposition individually. After correcting for this overlap, the Expanded
Mine Scenario would adversely affect an additional 1,829 acres of wetlands and other waters (7.4 km2)
and 17 miles (27.4 km) of streams at the mine site from dewatering, habitat fragmentation, and fugitive
dust. The following discussion considers these secondary impacts individually, without adjusting for
overlap (USACE 2020a: Table 4.22-40).
Dewatering associated with the Expanded Mine Scenario would impact 338 acres (1.4 km2) of wetlands
and other waters and 3.2 miles (5.1 km) of streams (USACE 2020a: Table 4.22-40). Dewatering of
wetlands and other waters causes the alteration or loss of wetland hydrology and may result in the
conversion of habitats to more mesic types. Drawdown of groundwater is expected primarily around the
open pit due to dewatering activities, but would also occur around quarries, TSFs, and WMPs due to
diversions and drainage/underdrain systems. Altered saturated surface flow and shallow interflow
resulting from a depression of the groundwater table is expected to adversely affect wetlands, surface
waters, and vegetation in the drawdown area (USACE 2020a: Section 4.22). Dewatering impacts to slope
wetlands (which constitute the majority of wetland acres impacted at the mine site) would be severe
and "[d]ue to the groundwater storage and organic matter production and nutrient cycling capacity of
slope wetlands, their loss would likely reduce the functional capacity of the watershed to maintain
downstream baseflows, as well as reducing the subsidy of organic matter and nutrients to downstream
aquatic ecosystems and organisms" (USACE 2020a: Page 4.22-30). Dewatering represents a secondary
but permanent impact to wetlands, streams, and other waters (USACE 2020a: Section 4.22).
Fragmentation associated with the Expanded Mine Scenario would affect 1,538 acres (6.2 km2) of
wetlands and other waters and 8.4 miles (13.5 km) of streams (USACE 2020a: Table 4.22-40). This
represents a nearly 600 percent increase in fragmentation impacts on wetlands and other waters and a
91 percent increase in fragmentation impacts on streams when compared to the 2020 Mine Plan.
Fragmentation of wetlands and other waters results when development divides a formerly continuous
aquatic resource into smaller, more isolated remnants. Habitat fragmentation represents a secondary
but permanent impact on wetlands, streams, and other waters (USACE 2020a: Section 4.22). Decreased
connectivity of aquatic ecosystems could preclude the completion of aquatic organisms' life cycles; for
example, anadromous fish may be unable to reach spawning grounds or access off-channel habitat
(USACE 2020a: Section 4.22). For anadromous fishes, the most severe form of fragmentation occurs
when discontinuities are created that either separate an aquatic habitat (stream, wetland, lake, pond) or
complex of aquatic habitats from the tributary network in such a way that precludes use (e.g., spawning,
rearing, feeding, migration, overwintering) by anadromous fish species and life stages documented to
occur in the habitat or eliminate the movement of water or dissolved or suspended materials to
downstream anadromous fish streams (Box 4-1).
Recommended Determination
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Basis for Recommended Determination
Fragmentation of stream channels and adjacent wetlands without hydrologic surface connections are
expected to result in a complete loss of function; partial loss of function would be expected for other
types of wetlands, such as slope and depressional wetlands, which would likely become drier due to the
diversion of shallow groundwater and surface water and the reduction of catchment areas (USACE
2020a: Section 4.22). Habitat fragmentation would likely reduce the functional capacity of the
watershed to maintain downstream baseflows, as well as reduce the subsidy of organic matter and
nutrients to downstream aquatic ecosystems and organisms (USACE 2020a: Section 4.22).
Fugitive dust associated with the Expanded Mine Scenario would affect 1,093 acres (4.4 km2) of
wetlands and other waters and 15 miles (24.1 km) of streams (USACE 2020a: Table 4.22-40). Fugitive
dust would be produced from ground-disturbing actions during construction, operations, and closure,
and from wind or vehicle dispersal of exposed soil in the post-closure period (USACE 2020a: Section
4.22). Fugitive dust has the potential to collect on wetland vegetation and accumulate in waters, with
adverse consequences for plant physiology, water quality, biotic community composition, and the
overall functions and values of wetlands, streams, and other waters (USACE 2020a: Section 4.22). The
majority of the potentially affected wetlands at the mine site are particularly susceptible to the adverse
effects of dust deposition because of their vegetation type and structure (USACE 2020a: Section 4.22).
4,3,1,3 Summary
EPA Region 10 has determined that direct and secondary impacts of the discharge of dredged or fill
material from construction and routine operation of the 2020 Mine Plan and discharges that would
result in effects similar or greater in nature and magnitude to the 2020 Mine Plan would result in
significant degradation under the Section 404(b)(1) Guidelines (40 CFR 230.10(c), Section 4.3.1.1).
These findings are based on the significantly adverse effects that the discharge of dredged or fill material
would have on special aquatic sites, life stages of anadromous fishes, anadromous fish habitat, and
aquatic ecosystem diversity, productivity, and stability under the Section 404(b)(1) Guidelines.
The Expanded Mine Scenario represents a reasonably foreseeable expansion of mine size over time,
from 1.3 billion tons up to 8.6 billion tons. This expansion would dramatically increase the amount of
destruction and degradation of anadromous fishery areas in the SFK, NFK, and UTC watersheds,
including a more than 400 percent increase in the length of anadromous fish streams permanently lost.
There are no examples of other projects resulting in this level of permanent loss of anadromous fish
streams in the CWA Section 404 regulatory program in Alaska, thus, there are no analogous Section 404
permitting cases with which to make any meaningful comparisons.
In addition to the losses estimated for the 2020 Mine Plan, estimated impacts of the Expanded Mine
Scenario include the permanent loss of an additional 35 miles (56.3 km) of documented anadromous
fish streams, an additional 295.5 miles (475.6 km) of streams that support anadromous fish streams,
and an additional 8,756 acres (35.4 km2) of wetlands and other waters across the SFK and UTC
watersheds (USACE 2020a: Table 4.22-40). These losses would represent extraordinary and
unprecedented levels of anadromous fish habitat loss and degradation, significantly expanding the
unacceptable adverse effects identified for the 2020 Mine Plan.
Recommended Determination
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Basis for Recommended Determination
Secondary effects of the discharge of dredged or fill material from construction and routine operation of
the 2020 Mine Plan would result in adverse impacts to approximately 845 acres of wetlands and other
waters (3.4 km2) and 29.9 miles (48.1 km) of streams at the mine site from dewatering, habitat
fragmentation, and fugitive dust (PLP 2020b, USACE 2020b). The FEIS estimates that these secondary
effects of the discharge of dredged or fill material from the construction and routine operation of the
Expanded Mine Scenario would adversely affect an additional approximately 1,829 acres of wetlands
and other waters (7.4 km2) and 17 miles (27.4 km) of streams at the mine site (USACE 2020a: Table
4.22-40) and would further reduce the quality and extent of anadromous fish habitat in the SFK and UTC
watersheds.
The losses of and impacts on salmon habitat could cause the extirpation of unique local populations of
Coho, Sockeye, and Chinook salmon that would affect the overall genetic diversity of each species. This
reduction in genetic diversity could adversely affect the stability and sustainability of valuable
subsistence, commercial, and recreational salmon fisheries. Subsistence harvests and recreational
fishing of non-salmon species could also suffer. For example, Rainbow Trout, Dolly Varden, and
Northern Pike are found in the affected waters, and would experience habitat losses as a result of mine
expansion.
Species with extended freshwater rearing periods, such as Coho, Chinook, and Sockeye salmon, are more
likely to be extinct, endangered, or threatened than species that spend less time in freshwater habitats
(NRC 1996, Gustafson et al. 2007). Therefore, the losses and degradation of discrete, productive
freshwater habitats for salmon estimated under the Expanded Mine Scenario could threaten multiple
distinct populations of species such as Coho, Chinook, and Sockeye salmon. Losses of these populations
would degrade the overall stability of fisheries within the SFK, NFK, and UTC watersheds. Ultimately,
cumulative effects on streams, wetlands, and other aquatic resources from the discharge of dredged or
fill material associated with the Expanded Mine Scenario would likely impair the health of the SFK, NFK,
and UTC watersheds and cause or contribute to significant degradation (40 CFR 230.10(c)) of the
watersheds' fishery areas.
4.3.2 Compensatory Mitigation Evaluation
EPA Region 10 has determined that discharges of dredged or fill material into waters of the United
States for the construction and routine operation of the 2020 Mine Plan would be likely to result in
unacceptable adverse effects on anadromous fishery areas (Sections 4.2.1 through 4.2.4). EPA Region 10
also has determined that discharges of dredged or fill material associated with future plans to mine the
Pebble deposit would be likely to result in unacceptable adverse effects on anadromous fishery areas in
the SFK, NFK, and UTC watersheds if the effects of such discharges are similar or greater in nature and
magnitude to those described in Sections 4.2.1 through 4.2.4.
The Section 404(b)(1) Guidelines direct that no discharge of dredged or fill material shall be permitted
unless all appropriate and practicable steps have been taken to minimize and compensate for the
project's adverse impacts on the aquatic ecosystem (40 CFR 230.10(d)). Discharges of dredged or fill
material for the construction and routine operation of the 2020 Mine Plan would have extensive
Recommended Determination
4-79
December 2022
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Section 4
Basis for Recommended Determination
unavoidable adverse impacts to aquatic resources that would require compensatory mitigation
(USACE 2020b).
Under Section 404(c) of the CWA, EPA has discretionary authority to deny or restrict the use of any
defined area as a disposal site "whenever" it determines that the discharge of dredged or fill material
will have an unacceptable adverse effect on statutorily enumerated aquatic resources. The statutory
standard does not direct EPA to consider mitigation when determining what constitutes an
unacceptable adverse effect nor restrict EPA to exercising its authority unless and until EPA has before it
a USACE permit identifying required mitigation. EPA's regulations provide that "[i]n evaluating the
unacceptability of such impacts, consideration should be given to the relevant portions of the section
404(b)(1) guidelines" (40 CFR 231.2). EPA does not view the mitigation provisions to be a relevant
portion of the Guidelines that should be considered in determining unacceptability in this circumstance
because there is no permit requiring mitigation and, in fact, USACE expressly rejected PLP's proposed
mitigation.
Nonetheless, although not required, EPA Region 10 evaluated the two compensatory mitigation plans
(CMPs) PLP submitted to USACE in 2020. As described in Section 4.3.2.2, both plans fail to adequately
mitigate the adverse effects that are the subject of this recommended determination to an acceptable
level.
In addition to the two CMPs PLP proposed to USACE in 2020, during development and finalization of the
2014 BBA, PLP and other commenters suggested an array of measures as having the potential to
compensate for the nature and magnitude of adverse impacts on wetlands, streams, and fishes from the
discharge of dredged or fill material associated with mining the Pebble deposit. EPA Region 10
evaluated the numerous additional measures that PLP and others proposed prior to issuing the 2014
Proposed Determination. During the public comment period for the 2014 Proposed Determination,
several commenters, including PLP, suggested additional measures as having the potential to
compensate for the nature and magnitude of adverse impacts on wetlands, streams, and fishes from the
discharge of dredged or fill material associated with mining the Pebble deposit.
PLP did not propose such measures to USACE during the Section 404 permit review process. EPA Region
10 provides, for informational purposes, an updated evaluation of the measures in Appendix C. Available
information demonstrates that known compensation measures are unlikely to adequately mitigate
effects described in this recommended determination to an acceptable level.
4,3,2,1 Overview of Compensatory Mitigation Requirements
Compensatory mitigation refers to the restoration, establishment, enhancement, and/or in certain
circumstances preservation of wetlands, streams, or other aquatic resources. Compensatory mitigation
regulations jointly promulgated by EPA and USACE state that "the fundamental objective of
compensatory mitigation is to offset environmental losses resulting from unavoidable impacts to waters
of the United States authorized by [Clean Water Act Section 404 permits issued by the USACE]" (40 CFR
230.93(a)(1)). Compensatory mitigation enters the analysis only after a proposed project design has
Recommended Determination
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December 2022
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Section 4
Basis for Recommended Determination
incorporated all appropriate and practicable means to avoid and minimize adverse impacts on aquatic
resources (40 CFR 230.91(c)).
4,3,2,2 Review of Compensatory Mitigation Plans Submitted by the Pebble Limited
Partnership
During the permit review process, PLP submitted two CMPs in an effort to address the project's
unavoidable aquatic resource impacts, the first in January 2020 (PLP 2020a) and the second in
November 2020 (PLP 2020c). Provided in this section is a discussion of both CMPs and why they failed
to adequately address the unacceptable adverse effects that are the subject of this recommended
determination.
Consistent with the Section 404(b)(1) Guidelines, in developing its CMPs, PLP first evaluated whether its
project impacts fell within the service area(s)74 of an approved mitigation bank or in-lieu fee program
with appropriate credits available. Because mitigation bank and in-lieu fee program options were not
available, both of PLP's CMPs involved permittee-responsible compensatory mitigation proposals.75
4,3,2,2,1 January 2020 Compensatory Mitigation Plan
PLP's January 2020 CMP included the following three components (PLP 2020a):
1. Improvements to wastewater collection and treatment systems in three villages in the
Kvichak River watershed.
2. Rehabilitation of 8.5 miles (13.7 km) of salmon habitat through replacement or removal of
some number of unidentified culverts.
3. One-time clean-up of 7.4 miles (11.9 km) of coastal habitat on Kamishak Bay (Cook Inlet).
In an August 20, 2020 letter to PLP, USACE stated "that discharges at the mine site would cause
unavoidable adverse impacts to aquatic resources and, preliminarily, that those adverse impacts would
result in significant degradation to those aquatic resources." Because of its concerns that adverse
impacts at the mine site would not be adequately mitigated by the January 2020 CMP, USACE
"determined that in-kind compensatory mitigation within the Koktuli River watershed will be required
to compensate for all direct and indirect [secondary] impacts caused by discharges into aquatic
resources at the mine site." In its letter, USACE requested that PLP submit a new CMP that would 1)
comply with all requirements of the compensatory mitigation regulations, 2) be "sufficient to offset the
unavoidable adverse impacts to aquatic resources," and 3) "overcome significant degradation at the
mine site."
74 The service area is the watershed, ecoregion, physiographic province, and/or other geographic area within
which the mitigation bank or in-lieu fee program is authorized to provide compensatory mitigation (40 CFR
230.98(d)(6)(ii)(A)).
75 Permittee-responsible mitigation means an aquatic resource restoration, establishment, enhancement, and/or
preservation activity undertaken by the permittee to provide compensatory mitigation for which the permittee
retains full responsibility (40 CFR 230.92).
Recommended Determination December 2022
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Basis for Recommended Determination
EPA Region 10 shares USACE's concerns regarding the nature and magnitude of the adverse effects on
aquatic resources in the Koktuli River watershed that would result from discharges of dredged or fill
material at the mine site. Like USACE, EPA Region 10 also identified deficiencies in the January 2020
CMP. As discussed here, EPA Region 10 also does not believe that the January 2020 CMP adequately
mitigates the adverse effects of the 2020 Mine Plan that are the subject of this recommended
determination to an acceptable level.
• Improvements to wastewater collection and treatment systems in three villages in the Kvichak River
watershed. Ninety-four percent of the 2020 Mine Plan's impacts on wetlands, streams, and other
aquatic resources occur in the Koktuli River watershed. However, all of these infrastructure projects
would occur in other watersheds, and none would address the substantial impacts in the Koktuli
River watershed that are the subject of this recommended determination.76 Further, such
wastewater infrastructure projects would not qualify as acceptable compensatory mitigation under
the regulations.77
• Rehabilitation of 8,5 miles (13,7 km) of salmon habitat through replacement or removal of some
number of unidentified culverts. The Koktuli River watershed is an almost entirely roadless area
and, thus, offers few, if any, viable culvert replacement or removal opportunities (none are identified
in the January 2020 CMP). Therefore, to the extent that such a component would provide any
environmental benefits, those benefits would not approach the level necessary to reduce the
adverse effects from the discharges of dredged or fill material associated with the 2020 Mine Plan
that are the subject of this recommended determination to an acceptable level.78
• One-time clean-up of 7,4 miles (11.9 km) of coastal habitat on Kamishak Bay (Cook Inlet), Like the
proposed wastewater infrastructure projects in component 1, this component does nothing to
address the substantial impacts in the Koktuli River watershed that are the subject of this
recommended determination. This component is not even located in the larger Bristol Bay
watershed. Further, to the extent that this component provides an environmental benefit, it would
be temporary and would not address the nature and magnitude of the permanent aquatic resource
losses at the mine site from construction and routine operation of the 2020 Mine Plan.79
76 None of these infrastructure projects would occur in the UTC watershed either and thus would not address any
substantial impacts in that watershed as well.
77 Such infrastructure construction projects do not meet the definition of compensatory mitigation, which can only
occur through four methods: aquatic resource restoration, establishment, enhancement, or in certain
circumstances, preservation (40 CFR 230.93(a)(2)).
78 The UTC watershed is also an almost entirely roadless area, thus this compensation measure would suffer from
the same deficiencies if it were applied to address impacts in the UTC watershed.
79 Similarly, this compensation measure would fail to address impacts in the UTC watershed for the same
reasons—it is not located in the Bristol Bay watershed and to the extent that this component provides an
environmental benefit, it would be temporary and would not address the nature and magnitude of the permanent
aquatic resource losses at the mine site from construction and routine operation of the 2020 Mine Plan.
Recommended Determination
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Basis for Recommended Determination
4,3,2,2,2 November 2020 Compensatory Mitigation Plan
In response to USACE's August 20, 2020 letter, PLP submitted a new CMP in November 2020 that
superseded the January 2020 CMP. When evaluating what compensation measures could reduce the
severity of the adverse effects estimated for the Koktuli River watershed, PLP ruled out all other
potential measures aside from preservation stating that"[Restoration, establishment, or enhancement
projects within the identified watershed are not plentiful enough in size or scale to mitigate for the
identified acreage of direct and indirect impacts to be mitigated; therefore, preservation is the only
available compensatory mitigation option" (PLP 2020c: Page 6). The November 2020 CMP includes a
single component-proposed preservation of 112,445 acres (455.0 km2) of state-owned land within the
Koktuli River watershed downstream from the mine site (Figure 4-19). The November 2020 CMP
proposed to do this by recording a deed restriction that would limit future uses of the land. The
proposed "Koktuli Conservation Area" may contain approximately 31,026 acres (125.6 km2) of
wetlands, lakes, and ponds, and 814 miles (1310 km) of streams (PLP 2020c).
Recommended Determination
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Section 4
Basis for Recommended Determination
Figure 4-19. Proposed Koktuli Conservation Area. Figure 1-1 from PLP's November 2020 Compensatory Mitigation Plan (PLP 2020c).
Nondaltpn
Pedro Bay
lliamna
Newhalen
liamsport
j^bble
PARTNERSHIP
FIGURE 1-1
Project Overview
Project Features
Transportation Corridor
Natural Gas Pipeline
Local Roads
Township Boundary
HUC 4 Watershed
Koktuli River HUC 10 Watersheds
Koktuli Conservation Area
General Land Status
State Patented, Tentatively Approved or
Other State Acquired Lands
ANCSA Patented or Interim Conveyed
Overlapping State and ANCSA
Bureau of Land Management Public
Lands
National Park System
Municipal or Other Private Parcels
~
C3
C3
Southwest
f
'OINT-sjC
PORT /
lliamna Lake (
AiasKa
Bristol Bay)
HUC 1903
NATURAL
GAS PIPELINE
Southcentral
Alaska
(Cook Inlet)
HUC 1902
Scale 1:533,560
Recommended Determination ^ December 2022
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Section 4
Basis for Recommended Determination
In its ROD, USACE determined that the November 2020 CMP did not overcome significant degradation at
the mine site, and that it failed to comply with all of the requirements of the compensatory mitigation
regulations (USACE 2020b). Specifically, the ROD found the following regulatory compliance deficiencies
with the November 2020 CMP and provided the following explanation (Attachment B6):
Lacks Sufficient Detail-Not Compliant: The level of detail of the mitigation plan is not
commensurate with the scale and scope of the impacts. [33 CFR 332.4(c)(1)]
Preservation Waiver-Not Compliant: Preservation shall be done in conjunction with
aquatic resource restoration, establishment, and/or enhancement activities. This
requirement may be waived by the district engineer where preservation has been identified
as a high priority using a watershed approach. No restoration, establishment, and/or
enhancement were proposed and justification identifying the proposed preservation as a
high priority using a watershed approach was not submitted. [33 CFR 332.3(h)(2)]
Amount of Compensatory Mitigation-Not Compliant: No compensatory mitigation was
proposed by the applicant to offset impacts from the port site. [33 CFR 332.3(f)]
Site Protection-Not Compliant: Deed restrictions proposed for 99 years. The goal of 33 CFR
332 is to ensure permanent protection of all compensatory mitigation project sites.
Justification not provided as to why a perpetual conservation easement with third-party
holder is not practicable. A site protection instrument was not provided; therefore, could not
be evaluated. The Final Plan did provide partial deed restriction language; however, the site
protection information was not complete, e.g. the Final Plan did not provide the required 60-
day advance notification language. No supporting real estate information was submitted;
therefore, could not review title insurance, reserved rights, rights-of-way, etc. Baseline
information was also not submitted; therefore, could not determine existing disturbances
such as roads, culverts, trails, fill pads, etc. USACE cannot enforce the deed restrictions since
third-party enforcement rights were not given to USACE. [33 CFR 332.7(a)]
Maintenance Plan-Not Compliant: No maintenance plan was submitted. [33 CFR
332.4(c)(8)]
Performance Standards-Not Compliant: No ecological performance standards were
submitted. Submitted performance standards are administrative in nature, such as the act of
monitoring, the act of enforcement, and the act of documentation of the deed restriction
requirements. [33 CFR 332.4(c)(9) and 33 CFR 332.5]
Monitoring-Not Compliant: One monitoring event is proposed. One event is not sufficient
to demonstrate that the compensatory mitigation project has met and maintained
performance standards. [33 CFR 332.6]
Long-Term Management-Not Compliant: No long-term endowment mechanism was
submitted. No supporting information was submitted for cost estimate. Cost estimate did not
include items such as capitalization rate, inflationary adjustments, legal defense costs, etc.;
therefore, could not determine sufficiency. Long-term manager unclear and unsupported.
[33 CFR 332.4(c)(ll) and 33 CFR 332.7(d)]
Financial Assurances-Not Compliant: No financial assurances were provided. [33 CFR
332.4(c)(13) and 33 CFR 332.3(n)]
Recommended Determination
4-85
December 2022
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Section 4
Basis for Recommended Determination
Based on its review of the November 2020 CMP, EPA Region 10 finds that it would not adequately
mitigate the adverse effects of the 2020 Mine Plan that are the subject of this recommended
determination to an acceptable level. Additional deficiencies identified by EPA Region 10 are as follows:
• The November 2020 CMP does not qualify as compensatory mitigation under the regulations.
Compensatory mitigation is defined as "the restoration (re-establishment or rehabilitation),
establishment (creation), enhancement, and/or in certain circumstances preservation of aquatic
resources for the purposes of offsetting unavoidable adverse impacts which remain after all
appropriate and practicable avoidance and minimization has been achieved" (40 CFR 230.92). The
November 2020 CMP "proposes permittee-responsible mitigation in the form of preservation" (Page
1). For the proposal to qualify as preservation it must meet the regulatory definition and
requirements for preservation.
Preservation is defined at 40 CFR 230.92 as "the removal of a threat to, or preventing the decline of,
aquatic resources by an action in or near those aquatic resources." Preservation is only allowed
when the resources to be preserved "are under threat of destruction or adverse modification"
(40 CFR 230.93(h)(l)(iv)). Though PLP would give up mining claims within the proposed
Conservation Area, development of those claims was not included in the FEIS, the CWA Section
404(b)(1) evaluation, or the Public Interest Review for the 2020 Mine Plan, and it was not
considered for development under the Expanded Mine Scenario. Further, the State of Alaska's MCO
393, issued in 1984, already precludes mining in the Koktuli River and 100 feet of its banks within
the proposed Koktuli Conservation Area (Section 2.2.1). The primary "threat of destruction or
adverse modification" for the proposed Conservation Area comes from the destruction and
degradation of streams, wetlands, lakes, and ponds upstream of the Conservation Area at the
proposed mine site for PLP's 2020 Mine Plan.
As discussed in Sections 4.2 and 4.3, discharges at the mine site for the 2020 Mine Plan would result
in a number of significant secondary effects that would degrade aquatic resources downstream of
the mine site, including the aquatic resources proposed for preservation in the Conservation Area.
For example, Sections 4.2 and 4.3.1 describe how aquatic resource losses at the mine site would
result in the loss or reduction of water, nutrient, detritus, and macroinvertebrate exports to
downstream areas, the losses of which would adversely affect downstream food webs and
anadromous fish spawning and rearing habitat.
The November 2020 CMP would not qualify as preservation because it does not involve "the
removal of a threat to, or preventing the decline of, aquatic resources by an action in or near" (40
CFR 230.92) the proposed Conservation Area. Indeed, PLP is seeking credit for "preserving" aquatic
resources that the record shows would be permanently degraded by its own mine plan.
• The November 2020 CMP does not reduce the severity of the impacts that are the subject of this
recommended determination. As discussed in Sections 4.2 and 4.3.1, discharges from the 2020 Mine
Plan would result in significant aquatic resource losses and degradation. This preservation proposal
would not adequately mitigate the adverse effects of the significant losses and degradation to an
Recommended Determination
4-86
December 2022
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Section 4
Basis for Recommended Determination
acceptable level because unlike the other forms of compensatory mitigation, preservation does not
replace lost ecological functions or area (40 CFR 230.92). Moreover, as discussed previously,
impacts at the mine site would lead to degradation of the aquatic resources proposed for
preservation.80
• The November 2020 CMP does not meet the higher bar for "permanent protection" of preservation
sites under the regulations. The general provisions for site protection in the regulations provide that
the "overall compensatory mitigation project must be provided long-term protection through real
estate instruments or other available mechanisms" (40 CFR 230.97(a)(1)). However, preservation
can only be used in "certain circumstances," including when the resources to be preserved would be
"permanently protected through an appropriate real estate or other legal instrument" (emphasis
added) (40 CFR 230.93(h)(l)(iv)). The November 2020 CMP proposes to protect the site by
recording a 99-year deed restriction on state lands. This arrangement is not permanent, and PLP
failed to identify a mechanism that would allow it to record a deed restriction over state-owned
lands. PLP cannot restrict the uses of state lands and PLP provided no evidence that the State has
agreed to do so.
4,3,2,3 Summary Regarding Compensatory Mitigation Measures
As described in Section 4.2, EPA Region 10 finds that discharges of dredged or fill material for the
construction and routine operation of the 2020 Mine Plan would be likely to result in unacceptable
adverse effects on anadromous fishery areas. Region 10 evaluated PLP's two compensatory mitigation
plans and neither plan adequately mitigates adverse effects described in this recommended
determination to an acceptable level. EPA Region 10 also evaluated additional potential compensation
measures for informational purposes. Available information demonstrates that known compensation
measures are unlikely to adequately mitigate effects described in this recommended determination to
an acceptable level.
80 This proposed preservation in the Koktuli River watershed would also fail to address any impacts that would
occur in the UTC watershed, since those impacts would be in an entirely different river basin (i.e., the Kvichak
River).
Recommended Determination
December 2022
4-87
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. RECOMMENDED DETERMINATION
Section 404(c) of the CWA authorizes EPA to (1) prohibit or withdraw the specification of any defined
area as a disposal site and (2) restrict, deny, or withdraw the use of any defined area for specification as
a disposal site whenever it determines that the discharge of dredged or fill material into such area will
have an unacceptable adverse effect on municipal water supplies, shellfish beds and fishery areas
(including spawning and breeding areas), wildlife, or recreational areas (33 USC 1344(c)).
The following recommended determination includes two parts. First, EPA Region 10 recommends
prohibiting the specification of a defined area as a disposal site (Section 5.1). Second, EPA Region 10
recommends restricting the use of a defined area for specification as a disposal site (Section 5.2). EPA
Region 10 is recommending the prohibition and restriction because it has determined that certain
discharges of dredged or fill material into waters of the United States within these areas would be likely
to result in unacceptable adverse effects on fishery areas (including spawning and breeding areas).
The prohibition and restriction presented below reference the Pebble deposit. For the purposes of the
prohibition and restriction, EPA Region 10 describes the "Pebble deposit" by its surficial boundary,
which is a rectangular area measuring 2.5 miles north-south by 3.5 miles east-west. As illustrated in
Figures 5-1, 5-2, and 5-3, this area covers:
The southeast quarter of Section 17, Township 3 South, Range 35 West, Seward Meridian
(S003S035W17); the south half of S003S035W14, S003S035W15, and S003S035W16; the east half of
S003S035W20; the entirety of S003S035W21, S003S035W22, S003S035W23, S003S035W26,
S003S035W27, and S003S035W28; and the east half of S003S035W29, with corners at approximately
latitude 59.917 degrees north (59.917 N) and longitude 155.233 degrees west (155.233 W), latitude
59.917 N and longitude 155.333 W, latitude 59.881 N and longitude 155.333 W, and latitude 59.881 N
and longitude 155.233 W.
5.1 Recommended Prohibition
The EPA Region 10 Regional Administrator has determined that discharges of dredged or fill material
for the construction and routine operation of the mine at the Pebble deposit identified in the 2020 Mine
Plan (PLP 2020b) would be likely to result in unacceptable adverse effects on anadromous fishery areas
in the SFK and NFK watersheds.81 Based on information in PLP's CWA Section 404 permit application,
the FEIS, and the ROD, such discharges would result in the following aquatic resource losses and
streamflow changes:
81 Anadromous fishes hatch in freshwater habitats, migrate to sea for a period of relatively rapid growth, and then
return to freshwater habitats to spawn. For the purposes of this recommended determination, "anadromous fishes"
refers only to Coho or Silver salmon (Oncorhynchus kisutch), Chinook or King salmon [O. tshawytscha), Sockeye or
Red salmon [O. nerka), Chum or Dog salmon [O. keta), and Pink or Humpback salmon [O. gorbuscha).
Recommended Determination c 4 December 2022
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Section 5
Recommended Determination
1. The loss of approximately 8.5 miles (13.7 km) of documented anadromous fish streams (Section 4.2.1).
2. The loss of approximately 91 miles (147 km) of additional streams that support anadromous fish
streams (Section 4.2.2).
3. The loss of approximately 2,108 acres (8.5 km2) of wetlands and other waters that support
anadromous fish streams (Section 4.2.3).
4. Adverse impacts on approximately 29 additional miles (46.7 km) of anadromous fish streams
resulting from greater than 20 percent changes in average monthly streamflow (Section 4.2.4).
EPA Region 10 has also determined that discharges of dredged or fill material associated with the
development of the Pebble deposit anywhere at the mine site that would result in the same or greater
levels of loss or streamflow changes as the 2020 Mine Plan also would be likely to have unacceptable
adverse effects on anadromous fishery areas, because such discharges would involve the same aquatic
resources characterized as part of the evaluation of the 2020 Mine Plan.
Sections 4.2.1 through 4.2.4 describe the basis for EPA Region 10's determination that each of the above
impacts independently would be likely to result in unacceptable adverse effects on anadromous fishery
areas (including spawning and breeding areas).
Accordingly, the Regional Administrator recommends that EPA prohibit the specification of waters of
the United States within the Defined Area for Prohibition, as identified in Section 5.1.1, as disposal sites
for the discharge of dredged or fill material for the construction and routine operation of the 2020 Mine
Plan. For purposes of the prohibition, the "2020 Mine Plan" is (1) the mine plan described in PLP's June
8, 2020 CWA Section 404 permit application (PLP 2020b) and the FEIS (USACE 2020a); and (2) future
proposals to construct and operate a mine to develop the Pebble deposit with discharges of dredged or
fill material in the Defined Area for Prohibition that would result in the same or greater levels of loss or
streamflow changes as the 2020 Mine Plan (i.e., the aquatic resource losses and streamflow changes
identified in #1-4 above). Because each of the losses or streamflow changes described in Sections 4.2.1
through 4.2.4 independently would be likely to result in unacceptable adverse effects on anadromous
fishery areas, proposals that result in any one of these losses or streamflow changes would be subject to
the prohibition. Dredged or fill material need not originate within the boundary of the Pebble deposit
defined above to be associated with mining the Pebble deposit and, thus, potentially subject to the
prohibition. For additional information regarding applicability of the prohibition, see Box 5-1.
5.1.1 Defined Area for Prohibition
The Defined Area for Prohibition identifies the geographic boundary within which the prohibition
applies to waters of the United States. EPA Region 10 identified the Defined Area for Prohibition
(Figure 5-1) by outlining a contiguous area around the portions of the 2020 Mine Plan's mine site
footprint located within the SFK and NFK watersheds. In this recommended determination, the Defined
Area for Prohibition encompasses approximately 24.7 square miles (63.9 km2) and is delineated by the
entirety of the Public Land Survey System (PLSS) quarter sections where mine site discharges were
Recommended Determination
5-2
December 2022
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Section 5
Recommended Determination
proposed in the 2020 Mine Plan within the headwaters of the SFK and NFK watersheds (ADNR 2022d).
Use of the PLSS quarter section boundaries in addition to watershed boundaries to outline the boundary
of the Defined Area for Prohibition provides clarity and administrative convenience by using publicly
available and commonly understood property and watershed boundaries, enabling EPA, USACE, and the
public to easily identify the locations of water resources that are subject to the prohibition.
I ¦MJIIttliyMlll'liilWI——I
EPA must have sufficient information to assess applicability of the determination to proposed discharges.
Proponents who seek an applicability assessment from EPA must provide to the Agency detailed information
about the proposed discharges of dredged or fill material, including, but not limited to, location(s) and
characteristics of potentially affected waters. At a minimum, proponents must provide geographic and
quantified impact information, including:
• Losses of documented anadromous waters (miles),
• Losses of additional streams (miles),
• Losses of wetlands and other waters (acres), and
• Anadromous fish streams (miles) that would experience changes (percent) to average monthly
streamflow.
Estimates must be based on field-verified, project-specific aquatic resource mapping. See Box 4-3 for an
example of project-specific stream and wetland mapping information. EPA may request additional
information to support the proponent's estimates.
! as in loss of streams, wetlands, or other waters, can be caused either directly by the discharge of
dredged or fill material for the construction and routine operation of a mine at the Pebble deposit, or
indirectly by the secondary effects of such discharges and is expected to result in the following effects for 5
years or more (Box 4-1):
• Elimination of streams, wetlands, or other waters within the footprints of mine components (e.g.,
TSFs, WMPs, stockpiles, roads, and the open pit);
• Dewatering(see definition below); or
• Fragmentation, meaning creation of discontinuities that separate an aquatic habitat (stream,
wetland, lake, pond) or complex of aquatic habitats from the tributary network in such a way that
either precludes use (e.g., spawning, rearing, feeding, migration, overwintering) by anadromous fish
species and life stages documented to occur in the habitat or eliminates the downstream
movement of water or dissolved or suspended materials.
D"¥ruier»ii;» includes:
• For documented anadromous waters, removing sufficient flow to eliminate access to or use of
habitat for the species and life stages documented to occur in the reach in question,
• For additional streams, removing sufficient flow to eliminate the downstream movement of water or
dissolved or suspended materials,
• For ponds or lakes, reducing the spatial extent of the pond or lake, and
• For wetlands, changing the hydrologic regime such that the wetland no longer exhibits wetland
hydrology, as defined in the Corps of Engineers Wetland Delineation Manual (USACE 1987).
Recommended Determination
5-3
December 2022
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Section 5
Recommended Determination
Figure 5-1. The Defined Area for Prohibition at the 2020 Mine Plan mine site. Figure based on Information from PLP (2020b), USGS
(2021a), and USGS (2021b).
Recommended Determination
5-4
December 2022
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Section 5
Recommended Determination
The description of the Defined Area for Prohibition (Figure 5-1) is as follows:
Beginning in the northeast corner at the intersection of the north-south half-section line and the
northern boundary of Section 9, Township 3 South, Range 35 West, Seward Meridian
(S003S035W09], at approximately latitude 59.938 north (59.938 N) and longitude 155.305 degrees
west (155.305 W), it extends 3 miles westward, along the northern boundary of S003S035W09, the
entire northern boundaries of S003S035W08 and S003S035W07 to the north-south half-section line
of S003S036W12; then south approximately 0.5 mile along the north-south half-section line of
S003S036W12 to the east-west half-section line of S003S036W12; then west approximately 1.0 mile
along the east-west half-section lines of S003S036W12 and S003S036W11 to the north-south half-
section line of S003S036W11; then south approximately 1.0 mile along the north-south half-section
line of S003S036W11 and S003S036W14 to the east-west half-section line of S003S036W14; then
west approximately 1.5 miles along the east-west half-section lines of S003S036W14 and
S003S036W15 to the western boundary of S003S036W15; then south along the western boundary of
S003S036W15 to the northern boundary of S003S036W21; then west approximately 1.0 mil along
the northern boundary of S003S036W21 to the western boundary of S003S036W21; then south
approximately 0.5 mile along the western boundary of S003S036W21 to the east-west half section
line of S003S036W20; then west approximately 0.5 mile along the east-west half-section line of
S003S036W20 to the north-south half-section line of S003S036W20; then south approximately 1.0
mile along the north-south half-section line of S003S036W20 and S003S036W29 to the east-west
half-section line of S003S036W29; then east approximately 1.0 mile along the east-west half-section
line of S003S036W29 and S003S036W28 to the north-south half-section line of S003S036W28; then
south approximately 1.5 miles along the north-south half-section line of S003S036W28 and
S003S036W33 to the northern boundary of S004S036W04; then east approximately 0.5 mile along
the northern boundary of S004S036W04 to the eastern boundary of S004S036W04; then south
approximately 0.5 mile along the eastern boundary of S004S036W04 to the east-west half-section
line of S004S036W03; then east approximately 0.5 mile along the east-west half-section boundary of
S004S036W03 to the north-south half-section line of S004S036W03; then north approximately 1.0
mile along the north-south half-section line of S004S036W03 and S003S036W34 to the east-west
half-section line of S003S036W34; then east approximately 0.5 mile along the east-west half-section
line of S003S036W34 to the eastern boundary of S003S036W34; then north approximately 0.5 mile
along the eastern boundary of S003S036W34 to the southern boundary of S003S036W26; then east
approximately 3.5 miles along the southern boundaries of S003S036W26, S003S036W25,
S003S035W30, and S003S035W29 to the north-south half-section line of S003S035W32; then south
approximately 0.5 mile along the north-south half-section line of S003S035W32 to the east-west
half-section line of S003S035W32; then east approximately 1.0 mile along the east-west half-section
line of S003S035W32 and S003S035W33 to the north-south half-section line of S003S035W33; then
south approximately 0.5 mile along the north-south half-section line of S003S035W33 to the
southern boundary of S003S035W33; then east approximately 0.5 mile along the southern boundary
of S003S035W33 to the eastern boundary of S003S035W33; then north approximately 1.5 miles
along the eastern boundary of S003S035W33 and S003S035W28 to the east-west half-section line of
S003S035W27; then east approximately 0.84 mile along the east-west half-section line of
S003S035W27 to the intersection with the border between the Nushagak and Kvichak watersheds at
approximately latitude 59.888 N and longitude 155.266 W; then generally northwest approximately
3.60 miles along the boundary between the Nushagak and Kvichak watersheds to the northernmost
intersection of the watershed boundary with the eastern boundary of S003S035W17 at
approximately latitude 59.922 N and longitude 155.319 W; then north approximately 0.64 mile along
the eastern boundary of S003S035W17 and S003S035W08 to the east-west half-section line of
S003S035W09; then east approximately 0.5 mile along the east-west half-section line of
S003S035W09 to the north-south half-section line of S003S035W09; then north approximately 0.5
mile along the north-south half-section line of S003S035W09 to the northern boundary of
S003S035W09, the initial starting point.
Recommended Determination
5-5
December 2022
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Section 5
Recommended Determination
5.2 Recommended Restriction
The Regional Administrator has determined that discharges of dredged or fill material associated with
future plans to mine the Pebble deposit would be likely to result in unacceptable adverse effects on
anadromous fishery areas (including spawning and breeding areas) anywhere in the SFK, NFK, and UTC
watersheds if the adverse effects of such discharges are similar or greater in nature82 and magnitude83
to the adverse effects of the 2020 Mine Plan described in Sections 4.2.1 through 4.2.4.
Accordingly, the Regional Administrator recommends restricting the use of waters of the United States
within the Defined Area for Restriction, as identified in Section 5.2.1, for specification as disposal sites
for the discharge of dredged or fill material associated with future proposals to construct and operate a
mine to develop the Pebble deposit that would either individually or cumulatively result in adverse
effects similar or greater in nature and magnitude to those described in Sections 4.2.1 through 4.2.4.
Because each of the losses or streamflow changes described in Sections 4.2.1 through 4.2.4
independently would be likely to result in unacceptable adverse effects on anadromous fishery areas,
proposals that result in any one of these losses or streamflow changes would be subject to the
restriction. To the extent that such future discharges would be subject to the prohibition, the restriction
would not apply. Dredged or fill material need not originate within the boundary of the Pebble deposit
defined above to be associated with mining the Pebble deposit and, thus, potentially subject to the
restriction. For additional information regarding applicability of the restriction, see Box 5-1 and Section
5.2.2.
5.2.1 Defined Area for Restriction
EPA Region 10 has determined that the discharge of dredged or fill material associated with mining the
Pebble deposit would be likely to result in unacceptable adverse effects on anadromous fishery areas
anywhere within the SFK, NFK, and UTC watersheds (Section 4). EPA Region 10 has identified the
Defined Area for Restriction by including those areas within the boundaries of the SFK, NFK and UTC
watersheds with potential to be a disposal site for the discharge of dredged or fill material associated
with mining the Pebble deposit.
The Pebble deposit is wholly located within the SFK, NFK, and UTC watersheds. To identify such areas
within the boundaries of the three watersheds with potential to be a disposal site for the discharge of
dredged or fill material associated with mining the Pebble deposit, EPA Region 10 identified the location
of mine claims in and around the Pebble deposit within the three watersheds. Alaska State law
specifically recognizes the opportunity for mineral claims to be converted to leases to use the state's
surface land for mining activity, including for a mill site, tailings disposal, or another use necessary for
82 Nature means type or main characteristic (see Cambridge Dictionary available at:
https://dictionary.cambridge.org/us/dictionary/english/nature).
83 Magnitude refers to size or importance (see Cambridge Dictionary available at:
https://dictionary.cambridge.org/us/dictionary/english/magnitude).
Recommended Determination
5-6
December 2022
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Section 5
Recommended Determination
mineral development, making the surface lands above mineral claims areas with potential to be a
disposal site for the discharge of dredged or fill material associated with mining.84 Accordingly, the
areas within the boundaries of the three watersheds where mine claims are currently held and areas
where mine claims are available (ADNR 2022c) represent locations where there is a potential to be a
disposal site for the discharge of dredged or fill material associated with mining the Pebble deposit. Use
of mine claims (the boundaries of which are defined by the PLSS), in addition to watershed boundaries,
to outline the boundary of the Defined Area for Restriction provides clarity and administrative
convenience by using publicly available and commonly understood property and watershed boundaries,
enabling EPA, USACE, and the public to easily identify the locations of water resources that are subject to
the restriction.
The Defined Area for Restriction encompasses certain headwaters of the SFK, NFK, and UTC watersheds.
The size of the Defined Area for Restriction is approximately 309 square miles (800 km2). The
description of the Defined Area for Restriction (Figures 5-2 and 5-3) is as follows:
Beginning in the northeast at the intersection between the Upper Talarik Creek, Newhalen River, and
Chulitna River watersheds, at approximately latitude 59.955 degrees north (59.955 N) and longitude
154.994 degrees west (154.994 W), it extends generally westward, along the boundary between the
Upper Talarik Creek and Chulitna River watersheds to the intersection between the Upper Talarik Creek,
Chulitna River, and Koktuli River watersheds, at approximately latitude 59.972 N and longitude 155.193
W; then generally west along the boundary between the Koktuli River and Chulitna River watersheds to
approximately latitude 59.979 N and longitude 155.583 W; then generally southward along the boundary
between the North Fork Koktuli River and mainstem Koktuli River watersheds, to the south boundary of
Section 11, Township 4 South, Range 38 West, Seward Meridian (S004S038W11), at approximately
latitude 59.837 N and longitude 155.774 W; then east along the south section line approximately 0.38
mile to the north-south half-section line at approximately latitude 59.837 N and longitude 155.763 W;
then south, approximately 1.5 mile, along the north-south half-section line to the center of S004S038W23
at approximately latitude 59.816 N and longitude 155.763 W; then west along the east-west half-section
line, approximately 1.09 mile, to the boundary between the Upper Koktuli River and Middle Koktuli River
subwatersheds at approximately latitude 59.816 N and longitude 155.794 W; then generally southwest,
approximately 0.46 mile, along the boundary between the Upper Koktuli River and Middle Koktuli River
subwatersheds to the west boundary of S004S038W22at approximately latitude 59.812 N and longitude
155.806 W; then south along the section line, approximately 0.26 mile, to the south boundary of
S004S038W22, at approximately latitude 59.808 N and longitude 155.806 W; then east along the south
section line, approximately 1.0 mile to the east boundary of S004S038W27 at approximately latitude
59.808 N and longitude 155.777 W; then south along the east section line of S004S038W27 and
S004S038W34, approximately 2.0 miles, until the south boundary of S004S038W34 at approximately
latitude 59.780 N and longitude 155.777 W; then west along the south section line, approximately 0.04
mile, until the boundary between the Koktuli River and Stuyahok River watersheds at approximately
latitude 59.780 N and longitude 155.778 W; then generally southeast, approximately 0.59 mile, along the
watershed boundary between the Koktuli River and Stuyahok River watersheds until the intersection
between the Koktuli River, Stuyahok River, and Kaskanak Creek watersheds at approximately latitude
59.775 N and longitude 155.764 W; then generally east along the boundary between the Koktuli River
and Kaskanak Creek watersheds, approximately 4.14 miles, to the north boundary of S005S037W06 at
approximately latitude 59.780 N and longitude 155.645 W; then east, approximately 0.09 mile, along the
north section line to approximately latitude 59.780 N and longitude 155.642 W; then south along the
north-south half-section line, approximately 0.07 mile, to the boundary between the Koktuli River and
Kaskanak Creek watersheds at approximately latitude 59.778 N and longitude 155.642 W; then generally
84 11 Alaska Administrative Code 86.600.
Recommended Determination g y December 2022
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Section 5
Recommended Determination
eastward, along the watershed boundary until the intersection between the Koktuli River, Kaskanak
Creek, and Lower Talarik Creek watersheds at approximately latitude 59.767 N and longitude 155.541 W;
then generally eastward, along the boundary between the Koktuli River and Lower Talarik Creek
watersheds to the intersection of the Koktuli River, Lower Talarik Creek, and Upper Talarik Creek
watersheds at approximately latitude 59.762 N and longitude 155.363 W; then generally southeastward,
along the boundary between the Upper Talarik Creek and Lower Talarik Creek watersheds, to the south
boundary of S005S036W24, at approximately latitude 59.722 N and longitude 155.329 W; then east
along the south section line approximately 0.52 mile to the east section line, at approximately latitude
59.722 N and longitude 155.314 W; then north along the section line 1.0 mile to the south boundary of
S005S035W18, at approximately latitude 59.736 N and longitude 155.314 W; then east along the south
section line 2.0 miles to the east boundary of S005S035W17, at approximately latitude 59.736 N and
longitude 155.259 W; then north along the east section line 1.0 mile to the south boundary of
S005S035W09, at approximately latitude 59.751 N and longitude 155.259 W; then east along the south
section line 1.0 mile to the east section line, at approximately latitude 59.751 N and longitude 155.230 W;
then north along the east section line 1.0 mile to the south boundary of S005S035W03, at approximately
latitude 59.765 N and longitude 155.230 W; then east along the south section line 1.0 mile to the east
section line, at approximately latitude 59.765 N and longitude 155.202 W; then north along the east
section line 1.0 mile to the south boundary of S004ST034W31, at approximately latitude 59.780 N and
longitude 155.202 W; then west along the south section line 0.09 mile to the west section line, at
approximately latitude 59.780 N and longitude 155.204 W; then north along the west section line 2.0
miles, to the south boundary of S004S034W19, at approximately latitude 59.808 N and longitude 155.204
W; then east along the south section line 1.0 mile to the east section line, at approximately latitude 59.808
N and longitude 155.176 W; then north along the east section line 1.0 mile to the south boundary of
section S004S034W17, at approximately latitude 59.823 N and longitude 155.176 W; then east along the
south section line 3.0 miles to the east boundary of S004S034W15, at approximately latitude 59.823 N
and longitude 155.090 W; then north along the east section line 2.0 miles to the south boundary of
S004S034W02, at approximately latitude 59.852 N and longitude 155.090 W; then east along the south
section line, approximately 2.64 miles, to the boundary between the Upper Talarik Creek and Newhalen
River watersheds, at approximately latitude 59.852 N and longitude 155.014 W; then generally north
along the watershed boundary until the east boundary of S003S034W12 at approximately latitude
59.936 N and longitude 155.032 W; then north 1.15 mile along the section line to the south boundary of
S002S033W31 at approximately latitude 59.953 N and longitude 155.032 W; then east along the section
line 1.23 mile to the boundary between the Upper Talarik Creek and Newhalen River watersheds, at
approximately latitude 59.953 N and longitude 154.997 W; then generally north, approximately 0.17
mile, along the watershed boundary to the starting point, at the intersection between the Upper Talarik
Creek, Newhalen River, and Chulitna River watersheds (coordinates above).
Recommended Determination
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Recommended Determination
Figure 5-2. The Defined Area of Restriction and the defined area for prohibition overlain on
wetlands from the National Wetlands Inventory (USGS 2021b).
NUSHAGAK
KVICHAK
Pebble Deposit
Defined Area for
Restriction
Defined Area for
Prohibition
2020 Mine Footprint
NWI Wetlands
Nushagak and Kvichak
Watersheds
South Fork Koktuli, North
Fork Koktuli, and Upper
Talarik Creek Watersheds
N
A
A
0 3
6
j_|
Miles
LO —
o —
10
i_l
Kilometers
Recommended Determination
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Section 5
Recommended Determination
Figure 5-3. The Defined Area for Restriction and the defined area for prohibition overlain on
streams and waterbodies from the National Hydrography Dataset (USGS 2021b).
NUSHAGAK
KVICHAK
Anadromous Fish Streams
Pebble Deposit
Defined Area for
Restriction
Defined Area for
Prohibition
2020 Mine Footprint
NHD Streams and
Waterbodies
Nushagak and Kvichak
Watersheds
South Fork Koktuli, North
Fork Koktuli, and Upper
Talarik Creek Watersheds
0 3 6
1 i i I—J i i i I
Miles
0 5 10
l—I—1—l—I—l—I—l_l
Kilometers
lliamna Lake
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Recommended Determination
5.2.2 Applicability of the Restriction
The restriction applies to proposed discharges of dredged or fill material into waters of the United States
associated with mining the Pebble deposit within the Defined Area for Restriction if such discharges
would result in adverse effects similar in nature and magnitude to the adverse effects of the discharges
described in Sections 4.2.1 through 4.2.4. The restriction also applies to proposed discharges if such
discharges would result in adverse effects greater in nature and magnitude than the adverse effects of
the discharges described in Sections 4.2.1 through 4.2.4.
Discharges of dredged or fill material within the Defined Area for Restriction associated with mining the
Pebble deposit would individually be subject to the restriction if such discharges, from a single proposal,
would result in any one of the losses or streamflow changes found in Sections 4.2.1 through 4.2.4.
Discharges of dredged or fill material within the Defined Area for Restriction associated with mining the
Pebble deposit would cumulatively be subject to the restriction if the effects of such discharges together
with other discharges within the Defined Area for Restriction associated with mining the Pebble deposit
combine to result in any one of the losses or streamflow changes described in Sections 4.2.1 through
4.2.4 in the SFK, NFK, and UTC watersheds. In evaluating whether the restriction would apply on a
cumulative basis, EPA will consider losses and streamflow changes associated with mining the Pebble
deposit that have occurred or that are authorized to occur. The restriction would apply to discharges of
dredged or fill material associated with mining the Pebble deposit cumulatively whether multiple
proposals are submitted by the same entity, such as when discharges are proposed over multiple phases
of the same project, or by different entities.
To evaluate whether a future proposal involves discharges that "would either individually or
cumulatively result in adverse effects" such that it would be subject to the restriction, EPA will verify
and then compare the estimates of losses of anadromous fish streams; losses of additional streams,
wetlands, and other waters that support anadromous fish streams; and changes to streamflow of
anadromous fish streams to assess whether the estimated losses and streamflow changes are similar to
or greater than the losses or changes identified in Section 4.2, specifically:
• The loss of approximately 8.5 miles of documented anadromous fish streams (Section 4.2.1),
• The loss of approximately 91 miles of additional streams that support anadromous fish streams
(Section 4.2.2),
• The loss of approximately 2,108 or more acres of wetlands and other waters that support
anadromous fish streams (Section 4.2.3), or
• Adverse impacts to approximately 29 miles of anadromous fish streams resulting from greater than
20 percent changes in average monthly streamflow (Section 4.2.4).
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Specifically, EPA will review:
• The location(s) of the proposed discharges and waters that will be impacted, including whether the
location is within the SFK, NFK, and UTC watersheds;
• The type(s) of waters that will be impacted (e.g., streams, lakes, ponds, wetlands) and whether such
waters are documented anadromous fish streams or support anadromous fish streams; and
• The type(s) of water resource impact(s) (e.g., habitat losses caused by elimination, dewatering, and
fragmentation; degradation of downstream habitat caused by streamflow changes) and the duration
ofimpact(s) (Box 4-1).
The restriction will apply if any one of the estimated losses or streamflow changes from the proposed
discharges are similar or greater to those described in Section 4.2. The restriction is based on the
determinations in Section 4.2 that these losses and streamflow changes would be likely to result in
unacceptable adverse effects.
5.3 When a Proposal is Not Subject to this Determination
Proposals to discharge dredged or fill material into waters of the United States associated with mining
the Pebble deposit that are not subject to this determination remain subject to all statutory and
regulatory authorities and requirements under CWA Section 404.
In light of the immense and unique economic, social, cultural, and ecological value of the aquatic
resources in the region, including the fishery areas in the SFK, NFK, and UTC watersheds, and their
susceptibility to degradation, EPA will carefully evaluate all future proposals to discharge dredged or fill
material in the region.
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The basis for EPA Region 10's recommended determination is the unacceptable adverse effects on
fishery areas from discharges of dredged or fill material associated with proposed mining at the Pebble
deposit, which is discussed in detail in Section 4. This section describes additional concerns and
information that, while not the basis for EPA Region 10's recommended determination, are related to
discharges of dredged or fill material associated with proposed mining at the Pebble deposit.85
6.1 Other Potential CWA Section 404(c) Resources
CWA Section 404(c) authorizes EPA to exercise its discretion to act whenever it determines that the
discharge of dredged or fill material will have an unacceptable adverse effect on specific aquatic
resources. CWA Section 404(c) provides the following:
The Administrator is authorized to prohibit the specification (including the withdrawal of specification)
of any defined area as a disposal site, and he is authorized to deny or restrict the use of any defined area
for specification (including the withdrawal of specification) as a disposal site, whenever he determines,
after notice and opportunity for public hearings, that the discharge of such materials into such area
will have an unacceptable adverse effect on municipal water supplies, shellfish beds and fishery
areas fincluding spawning and breeding areas!. wildlife, or recreational areas. Before making such
determination, the Administrator shall consult with the Secretary. The Administrator shall set forth in
writing and make public his findings and his reasons for making any determination under this
subsection, [emphasis added]
Section 4 of this recommended determination considers the adverse effects from the discharge of
dredged or fill material on fishery areas. Section 6.1 evaluates the potential for adverse effects on
wildlife, recreation, and water supplies.
6.1.1 Wildlife
Unlike most terrestrial ecosystems, the Bristol Bay watershed has undergone little development and
remains largely intact. Thus, it still supports its historical complement of species, including large
carnivores, such as brown bears, bald eagles, and gray wolves; ungulates such as moose and caribou;
and numerous bird species. For example, more than 40 mammal species are thought to regularly occur
in the Nushagak and Kvichak River watersheds (Brna and Verbrugge 2013). At least 13 of these species
are known, or have the potential based on the presence of suitable habitat, to occur in the SFK, NFK, and
85 Section 6.4 references EPA Region 10's consideration of potential costs. In prior CWA Section 404(c) actions, EPA
has made its "unacceptability" finding based solely on adverse effects on aquatic resources and did not consider
non-environmental costs, such as the forgone economic activity associated with the project, in making that finding.
See 44 Fed. Reg. 58,076, 58,078 (October 9,1979). In the event such information is required to be considered under
Section 404(c), EPA Region 10 has documented its consideration of such information in a document referenced in
Section 6.4.
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Other Concerns and Considerations
UTC watersheds: brown bear, moose, caribou, gray wolf, red fox, river otter, wolverine, arctic ground
squirrel, red squirrel, beaver, northern red-backed vole, tundra vole, and snowshoe hare (PLP 2011:
Chapter 16). One of two freshwater harbor seal populations in North America is found in Iliamna Lake
(Smith et al. 1996).
As many as 134 species of birds occur in the Nushagak and Kvichak River watersheds (Brna and
Verbrugge 2013), and at least 37 waterfowl species have been observed in the SFK, NFK, and UTC
watersheds, 21 of which have been confirmed as breeders (PLP 2011: Chapter 16). The region's aquatic
habitats support migratory and wintering waterfowl. These habitats include an important staging area
for many species, including emperor geese, Pacific brant, and ducks, during spring and fall migrations.
Twenty-eight landbird and 14 shorebird species have also been documented in the SFK, NFK, and UTC
watersheds (PLP 2011: Chapter 16). The Bristol Bay watershed supports millions of marine birds
throughout the year and is one of the world's most productive areas for marine birds (Warnock and
Smith 2018). Two areas in the region, Kvichak Bay and Nushagak Bay, are designated as Western
Hemisphere Shorebird Reserve Network sites (WHSRN 2022a, 2022b). The FEIS identifies bird species
protected under the Migratory Bird Treaty Act of 1918, the Bald and Golden Eagle Protection Act, and
bird species of concern within its mine site analysis area (USACE 2020a: Section 4.23).
Species found in the Nushagak and Kvichak River watersheds may have home ranges or migration
patterns that extend beyond the watersheds as well (e.g., brown bears, caribou, and migratory birds).
Several bird species found within the watersheds are considered species of special concern and are
already experiencing population declines due to climate change effects on their preferred foraging fish
(USACE 2020b). Within the Nushagak and Kvichak River watersheds, there are no known breeding or
otherwise significant occurrences of any species listed as threatened or endangered under the
Endangered Species Act, nor is there any designated critical habitat.
Wildlife present in the SFK, NFK, and UTC watersheds—several of which are essential subsistence
species (Section 6.3.1)—would likely be adversely affected by large-scale mining at the Pebble deposit.
Direct impacts of mining on resident and migratory wildlife species would include, but are not limited
to, loss of terrestrial and aquatic habitat, reduced habitat effectiveness (e.g., in otherwise suitable
habitats adjacent to the mine area), habitat fragmentation, increased stress and avoidance due to noise
pollution, and increased conditioning on human food (EPA 2014: Chapter 12). Direct habitat loss and
secondary habitat avoidance would affect the Mulchatna Caribou Herd (USACE 2020b), an important
subsistence resource and prey species for wolves and brown bears (EPA 2014: Chapter 12). Brown
bears, which are an important recreation species in the region, would experience direct loss of foraging
and denning habitat. Impacts on wildlife habitat and consequential wildlife displacement would likely
result in a cascading effect, as species compete for new feeding, breeding, and nesting habitats (USACE
2020b). Direct copper toxicity to wildlife resulting from mine operations is less of a concern than
indirect effects from copper-related reductions in aquatic communities (EPA 2014: Chapter 12).
In addition to direct mine-related effects, wildlife species would also likely be affected indirectly via any
reductions in salmon populations. Marine-derived nutrients imported into freshwater systems by
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Section 6
Other Concerns and Considerations
spawning salmon provide the foundation for the region's aquatic and terrestrial foodwebs, via direct
consumption of salmon in any of its forms (spawning adults, eggs, carcasses, or juveniles) and nutrient
recycling (e.g., transport and distribution of marine derived nutrients from aquatic to terrestrial
environmental by wildlife) (Section 3.3.4). Availability and consumption of these salmon-derived
resources can have significant benefits for terrestrial mammals and birds, including increases in growth
rates, litter sizes, nesting success, and population densities (Brna and Verbrugge 2013). Waterfowl prey
on salmon eggs, parr, and smolts and scavenge salmon carcasses. Carcasses are an important food
source for bald eagles, water birds, other land birds, other freshwater fishes, and terrestrial mammals.
Aquatic invertebrate larvae also benefit from carcasses and are an important food source for water birds
and land birds. Decomposing salmon acts as an organic input to streambed substrate (Cederholm et al.
1999). It is likely that the species identified above would be adversely affected by any mine-related
reductions in salmon production.
The FEIS identifies direct and indirect impacts to wildlife that could result at the proposed mine site,
including behavioral disturbances, injury and mortality, and habitat changes. Noise and the presence of
humans, vehicles, aircraft, and other equipment could result in avoidance of the mine site by wildlife
throughout construction, operations, and closure. Mortality of, and injury to, wildlife at the proposed
mine site could occur due to vegetation clearing; collisions with vehicles, equipment, and structures;
defense of life and property; altered predator and prey relationships; changes in water quality; nest
abandonment and/or disturbance; exposure to contaminants; and possible spills. The FEIS estimates the
direct loss of 8,390 acres of habitat and the indirect loss of additional habitat surrounding the mine site
due to avoidance, which would occur throughout the life of the project and longer in areas that are not
restored. Wildlife habitat may also see long-term changes due to the introduction or spread of invasive
species, changes in water quality and air quality, and potential spills (USACE 2020a: Section 4.32).
The Expanded Mine Scenario would contribute to cumulative effects of wildlife habitat loss, disturbance,
injury, and mortality. The FEIS estimates that 31,541 acres of habitat would be lost at the expanded
mine site, as well as additional habitat surrounding the expanded mine site due to avoidance (USACE
2020a: Section 4.23).
The FEIS provides more detailed information not summarized in this recommended determination
regarding other potential direct, indirect, and cumulative impacts that may result from the 2020 Mine
Plan and the Expanded Mine Scenario, including species-specific information in some cases.
6.1.2 Recreation
Next to commercial salmon fishing and processing, recreation is the largest private economic sector in
the Bristol Bay region (EPA 2014: Appendix E) due mainly to the watershed's remote, pristine
wilderness setting and abundant natural resources. Key recreational uses include sport fishing, sport
hunting, and other tourism/wildlife viewing recreational trips—all of which are directly or indirectly
dependent on the intact, salmon-based ecosystems of the region. Direct regional expenditures on these
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Section 6
Other Concerns and Considerations
recreational uses, expressed in terms of 2021 dollars,86 are estimated at more than $210 million (EPA
2014: Table 5-4). Much of these expenditures are by non-residents, highlighting the fact that the
recreational value of Bristol Bay watershed is recognized even by people that live a significant distance
from the region. Total visitors to the Bristol Bay region are estimated at 40,00 to 50,000 people annually
(McKinley Research Group 2021). In 2019, tourism spending in the Bristol Bay region generated $155
million in total economic output and 2,300 jobs in Alaska. Recreation in the region diversifies the
region's economy through the use of sustainable resources (McKinley Research Group 2021).
In particular, the abundance of large game fishes makes the region a world-class destination for
recreational anglers. The 2005 Bristol Bay Angler Survey confirmed that the freshwater rivers, streams,
and lakes of the region are a recreational resource equal or superior in quality to other world-renowned
sport fisheries (EPA 2014: Appendix E). In 2009, sport anglers took approximately 29,000 sport-fishing
trips to the Bristol Bay region (12,000 trips by people living outside of Alaska, 4,000 trips by Alaskans
living outside of the Bristol Bay area, and 13,000 trips by Bristol Bay residents) (EPA 2014: Chapter 5).
These sport-fishing activities directly employed over 800 full- and part-time workers. At peak times, 92
businesses and 426 guides have operated in the Nushagak and Kvichak River watersheds alone (EPA
2014: Chapter 5). More than 90 lodges and camps operate in the Bristol Bay region, primarily focusing
on sport fishing and bear viewing. Lodge and camp guests spent an estimated $77 million in 2019
(McKinley Research Group 2021).
Much of the sport fishery in the region is relatively low-impact catch-and-release, although there is some
recreational harvest. Sockeye, Chinook, and Coho salmon are the predominant fishes harvested,
although Rainbow Trout, Dolly Varden, Arctic Char, Arctic Grayling, Northern Pike, Chum Salmon, Lake
Trout, and whitefish are also important recreational species (Dye and Borden 2018). From 2007 to
2017, the total annual recreational harvest in the Bristol Bay Management Area ranged from roughly
42,000 to 59,000 fish (Dye and Borden 2018). In 2017, an estimated 30,282 Rainbow Trout were caught
and 241 Rainbow Trout were harvested in the Nushagak, Wood, and Togiak River watershed. The same
year, an estimated 114,431 Rainbow Trout were caught and 66 Rainbow Trout were harvested in the
Kvichak River watershed (Table 3-12) (Romberg et al. 2021).
Sport fishing in the Bristol Bay region is a large and well-recognized share of recreational use and
associated visitor expenditures (Section 3.3.5). In addition, thousands of trips to the region each year are
made for sport hunting and wildlife viewing. For example, Lake Clark and Katmai National Parks are
nationally significant protected lands and are important visitor destinations. Between 2012 and 2021,
Katmai National Park and Preserve attracted an average of 41,139 visitors annually, and Lake Clark
National Park and Preserve averaged 15,728 visitors annually (NPS 2022). Rivers within Katmai
National Park provide the best locations in North America to view wild brown bears (EPA 2014:
Appendix E). A 2019 study found that activities related to bear viewing resulted in approximately $34.5
million in sales and $10 million in direct wages and benefits based on surveys of Lake Clark National
Park, Katmai National Park, and McNeil River State Game Sanctuary, which are located in the Bristol Bay
86 Values adjusted using Anchorage Consumer Price Index.
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Section 6
Other Concerns and Considerations
watershed (Young and Little 2019). The region is also used for recreational water activities, hiking,
backpacking, biking, flightseeing, and other activities, especially in Katmai National Park and Preserve
and Lake Clark National Park and Preserve (USACE 2020a: Section 4.5).
Sport hunting for caribou, moose, brown bear, and other species also plays a role in the local economy of
the Bristol Bay region. In recent years, approximately 1,323 non-residents and 1,319 non-local residents
of Alaska traveled to the region to hunt, spending approximately $6,395 (non-residents) and $1,631
(non-local residents) per trip (expressed in 2021 dollars87), respectively (EPA 2014: Chapter 5). These
hunting activities result in an estimated $10 million per year in direct hunting-related expenditures
(values expressed in 2021 dollars88) and directly employ over 100 full- and part-time workers (EPA
2014: Chapter 5).
The 2020 Mine Plan would result in the permanent alteration and loss of 8,391 acres of land at the mine
site that are currently available for recreation, including the loss of 2,113 acres of wetlands and other
waters that support fish and wildlife and attract recreational anglers and hunters (USACE 2020a:
Section 4.5). As described in Section 4.2.1.1, the 2020 Mine Plan would permanently remove 8.5 miles
(13.7 km) of streams with documented occurrence of Coho and Chinook salmon, disrupting the
spawning cycle and displacing spawners. The substantial spatial and temporal extents of stream habitat
losses under the 2020 Mine Plan suggest that these losses would reduce the overall capacity and
productivity of Chinook and, particularly, Coho salmon in the NFK watershed. The Nushagak River—to
which the SFK and NFK flow—supports the largest Chinook Salmon sport fishery in the United States
and, in turn, a network of private and commercial sport-fishing camps overseen by Choggiung, Ltd., the
Alaska Native village Corporation for Dillingham, Ekuk, and Portage Creek (NMWC 2007, Choggiung, Ltd.
2014, Dye and Borden 2018). The loss of habitat at the mine site would affect downstream trout habitat,
possibly displacing trout and, therefore, anglers (USACE 2020a: Section 4.6). The FEIS acknowledges the
potential for economic impacts borne by recreational anglers and affiliated guides and lodges, stating
that "affected operators could substitute fishing on different streams, albeit at potentially higher costs to
themselves and their consumers" (USACE 2020a: Page 4.6-12).
The FEIS indicates that the mine site itself does not support much recreational use, though construction,
operations, and closure of the mine site would affect recreational activities on surrounding lands,
including Lake Clark National Park and Katmai National Park (USACE 2020a, 2020b). Noise and the
presence of humans, vehicles, aircraft, and other equipment is likely to result in avoidance of the mine
site by wildlife that support recreational uses. Changes to the landscape due to visibility of the mine and
night sky light pollution would alter the recreational experience for visitors and potentially displace
recreation visitors and activities to other areas. These impacts together would reduce the opportunities
for solitude (USACE 2020a: Section 4.6). Further, there exists the possibility of a loss in recreational
visitors and activity in areas not impacted by the 2020 Mine Plan resulting from the perceived loss of
87 Values adjusted using Anchorage Consumer Price Index.
88 Values adjusted using Anchorage Consumer Price Index.
Recommended Determination
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Section 6
Other Concerns and Considerations
habitat or fishery quality due to the construction and operations of the mine (Glasgow and Train 2018,
English et al. 2019, Glasgow and Train 2019).
The Expanded Mine Scenario, which would extend impacts in the SFK and UTC watersheds, would
contribute to cumulative effects similar in nature to those described above but over a larger area. The
larger mine footprint would further displace wildlife and increase the amount of disturbance in the NFK
and SFK watersheds, reducing opportunities for hunting, fishing, and wildlife viewing (USACE 2020a:
Section 4.6).
6.1.3 Public Water Supplies
Alaska Native residents of the Nushagak and Kvichak River watersheds consistently stress the
importance of clean water to their way of life, not only in terms of providing habitat for salmon and
other fishes, but also in terms of providing high-quality drinking water (EPA 2014: Appendix D).
Drinking water sources in the region include municipal treated water, piped but untreated water,
individual wells, and water hauled directly from rivers and lakes (EPA 2014: Appendix D, Table 3).
At this time, it is difficult to determine what level of effects routine operations of a mine at the Pebble
deposit could have on public water supplies in the Nushagak and Kvichak River watersheds. Private
wells are a primary drinking water source for many residents of the Nushagak and Kvichak River
watersheds, and communities also rely on groundwater for their public water supply. The extent that
surface water influences the quality or quantity of the groundwater source for these wells is unknown.
However, there are also communities in the area that rely on surface water sources, which may be more
susceptible to mine-related contamination. Although no communities are currently located in the SFK,
NFK, or UTC watersheds (Figure ES-2), residents of nearby communities use these areas for subsistence
hunting and fishing and other activities and may drink from surface waters and springs in these
watersheds.
Development of a large-scale mine at the Pebble deposit would require a work force of more than 1,700
people during construction and more than 850 people during mine operation (USACE 2020a: Chapter 2).
Thus, the mine site would rival Dillingham as the largest population center in the Bristol Bay watershed
during construction and would remain the second-largest population center during operation. This
population would require sufficient water supplies in the Pebble deposit region, and these supplies
would be vulnerable to contamination or degradation resulting from mine development and operation.
The 2020 Mine Plan includes installation of groundwater wells on the northern side of the mine site to
supply potable water (USACE 2020a: Section 3.18).
Other public water supplies (e.g., at Iliamna, Newhalen, and Pedro Bay) could be affected by
construction of and transport along a roadway and/or pipelines connecting the Pebble deposit region to
Cook Inlet. The Safe Drinking Water Act requires states and utilities to assess the source water for public
water systems, and there are CWA provisions designed for protecting source waters from
contamination. The ADEC Drinking Water Program has delineated drinking water source protection
areas for all public water system sources and includes areas along the proposed transportation corridor,
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Section 6
Other Concerns and Considerations
the region surrounding Iliamna Lake, and the adjacent communities. Currently, there are no designated
drinking water protection areas for private wells in Newhalen, Iliamna, and other villages along the
transportation corridor, nor at the mine site (USACE 2020a: Section 3.18).
6.2 Effects of Spills and Failures
This recommended determination does not consider impacts from potential spills, accidents, and
failures as a basis for its findings; however, as discussed in this section there is a likelihood that some
spills would occur over the life of the mining operation. A recent report documenting spills that have
occurred at Alaska mining operations found that more spills, particularly transportation-related spills,
occurred than were predicted in the EISs for these mining operations (Lubetkin 2022). The report did
not document the cleanup actions that occurred for these spills, or the resulting environmental impacts.
Failure of major infrastructure (e.g., concentrate and tailings pipelines, water treatment plants, or TSF
dams), while less likely, could result in severe impacts on aquatic resources in the SFK, NFK, and UTC
watersheds.
The FEIS and the BBA evaluated potential impacts of an array of possible accidents and failures that
could result in releases and spills of concentrate, tailings, and contaminated water, including their
potential effects on fishery areas (EPA 2014, USACE 2020a). This section summarizes the potential
impacts of mine area spill scenarios on aquatic resources that were evaluated in the FEIS and also
summarizes the potential impacts of a tailings dam failure.
6.2.1 Final Environmental Impact Statement Spill and Release
Scenarios
The FEIS evaluates the spill risk associated with the 2020 Mine Plan, including spills and releases of
diesel fuel, natural gas, chemical reagents, copper-gold flotation concentrate, tailings, and untreated
contact water (USACE 2020a: Section 4.27). The FEIS includes a detailed analysis of seven hypothetical
spill scenarios that would generally have a low probability of occurring, but with potential
environmental consequences that could be high. Some of the scenarios considered in the FEIS are
vehicle and marine transportation-related and are not mentioned here since this recommended
determination focuses on the mine site impacts. The spill scenarios analyzed in the FEIS applicable to
the mine site include a spill of concentrate slurry, a bulk tailings release from the tailings delivery
pipeline, and a partial breach of the pyritic tailings impoundment that results in a pyritic tailings release.
The FEIS evaluates potential environmental impacts of these spill scenarios and uncertainties. A
summary of the potential environmental impacts of these scenarios on aquatic resources is provided
below.
6.2.1.1 Release of Concentrate Slurry from the Concentrate Pipeline
The copper-gold flotation concentrate that would be produced under the 2020 Mine Plan would be
composed of a slurry containing finely ground rock and mineral particles that have been processed from
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Section 6
Other Concerns and Considerations
the mined ore to concentrate the economic minerals containing copper and gold. The concentrate
particles in the slurry would be potentially acid generating and capable of metal leaching over time,
depending on conditions. The concentrate slurry would also contain approximately 45 percent mine
contact water, which would have elevated concentrations of metals, including copper, and residual
amounts of chemical reagents. Under the 2020 Mine Plan, the concentrate would be transported from
the mine site to the port site by a pipeline. The FEIS evaluates the potential impacts due to a release of
concentrate slurry from the pipeline. The concentrate slurry release scenario was based on historic spill
data and a statistical evaluation of probabilities. The FEIS estimates a concentrate pipeline failure rate of
0.013, which equates to a probability of one or more pipeline failures of 1.3 percent in any given year; 23
percent in 20 years; or 64 percent in 78 years.
The analysis in the FEIS determines that a concentrate slurry spill into flowing waters could have the
following impacts on water quality, aquatic resources, and subsistence, commercial, and recreational
fisheries users (extent and magnitude of impacts would depend on the size of the spill and spill response
actions):
• If a concentrate spill occurs to flowing water, the concentrate would be difficult to recover and
would be transported downstream. The distance downstream would depend on the amount and
location of the release but could extend into Iliamna Lake.
• Concentrate solids would cause a temporary increase in total suspended solids (TSS) and
sedimentation to downstream waters.
• Potential impacts to fish from increased TSS and sedimentation include decreased success of
incubating salmon eggs; reduced food sources for rearing juvenile salmon; modified habitat; and in
extreme cases, mortality to eggs and rearing fish in the immediate area of the spill.
• Contact water contained in the concentrate slurry would result in exceedances of water quality
criteria for copper and other metals.
• Sulfide minerals in the concentrate slurry would slowly dissolve in the subaqueous environment
over years to decades and result in metal leaching. The dissolved metals in the aqueous phase of the
concentrate slurry could have acute impacts to the aquatic environment that would likely be
temporary and localized, but would depend on the size of the release.
• A concentrate spill into flowing water could temporarily displace recreational angling efforts in the
vicinity of the spill if the event or cleanup occurred during the open water fishing season.
• A concentrate release would likely cause concerns over contamination for local subsistence users.
6,2.1,2 Tailings Releases
Tailings are the leftover mixture of ground ore and process water following separation of the copper-
gold concentrate and molybdenum concentrate. Processing associated with the 2020 Mine Plan would
result in the production of two separate tailings waste streams, bulk tailings, and pyritic tailings.
Recommended Determination
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Section 6
Other Concerns and Considerations
Approximately 88 percent of the tailings would be bulk tailings and approximately 12 percent would be
pyritic tailings. The bulk tailings would consist of tailings that are primarily non-acid generating. The
pyritic tailings would have a high level of potentially acid generating minerals.
The bulk tailings would be transported by pipeline to a bulk TSF. The pyritic tailings would be
transported by a pipeline to a pyritic TSF. Table 6-1 lists some of the key features of the TSFs.
-
Bulk TSF
• 1.1 billion tons of tailings would be disposed in the bulk TSF.
• Tailings would be thickened before disposal in the TSF.
• TSF would have a minimal supernatant pool (pond) during operations.
• TSF would have two embankments (dams). The main dam would be 13,700 ft long and 545 ft high. The
south dam would be 4,900 ft long and 300 ft high.
• The main dam would be a flow-through design and would be constructed using the centerline method.
• The south dam would be constructed using downstream method and would be lined on the upstream face.
• At closure, the TSF would be covered and allowed to dewater with the goal of becoming a stable landform.
Pyritic TSF
• 155 million tons of pyritic tailings and up to 93 million tons of PAG waste rock would be stored in the pyritic
TSF.
• TSF would have a full water cover during operations.
• TSF would have three dams. The south dam would be 4,500 ft long and 215 ft high. The north dam would
be 335 ft high and the east dam 225 ft high with combined length of 2,500 ft.
• These dams that would be constructed using the downstream method.
• Impoundment would be fully lined.
• At closure, the pyritic tailings and waste rock would be backfilled into the open pit.
Source: USACE 2020a.
The FEIS evaluates the potential environmental impacts associated with two hypothetical tailings release
scenarios, including a release of 1.56 million cubic feet of bulk tailings associated with shearing of the
tailings delivery pipelines and a partial breach of the pyritic tailings facility embankment that would result
in a release of 185 million cubic feet of tailings and pond water. These scenarios were based on an EIS-
Phase Failure Modes Effects Analysis (FMEA) risk assessment that was conducted by USACE. The FEIS
determines that tailings releases under these scenarios could result in the following impacts:
• Under both tailings release scenarios, most of the fine tailings particles would be transported
downstream, causing elevated TSS in exceedance of water quality criteria (WQC) for approximately
230 miles downstream as far as the Nushagak River Estuary, where the river feeds into Nushagak
Bay. Additional TSS would be generated due to ongoing erosion and sedimentation from potential
stream destabilization during the release floods and could persist for months to years, depending on
the speed and effectiveness of stream reclamation efforts that would control streambed erosion.
• Tailings fluids (contact water used to mix the bulk tailings slurry and pyritic supernatant fluid)
would contain concentrations of some metals that exceed WQC. The dissolved metals would be
transported downstream and diluted to various degrees, depending on stream flow. Metals with the
highest concentrations would continue to exceed WQC for tens of miles downstream. The estimated
extent of impacts for the specific scenarios modeled in the FEIS are as follow:
Recommended Determination
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December 2022
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Section 6
Other Concerns and Considerations
o Bulk tailings release: Copper concentrations would exceed the most stringent WQC to the
Koktuli River below the NFK and SFK confluence, about 23 miles downstream from the mine
site. Molybdenum, zinc, lead, and manganese concentrations would exceed the most stringent
WQC until the Mulchatna River below the Koktuli River confluence, about 62 miles downstream.
Cadmium concentrations would exceed the most stringent WQC until the Mulchatna River below
the Stuyahok River confluence, about 78 miles downstream from the mine site.
o Pyritic tailings release: Copper would remain at levels exceeding the most stringent WQC until
the Mulchatna River below the Koktuli River confluence, about 80 miles downstream of the
mine site. Zinc, lead, and manganese would remain at levels exceeding the most stringent WQC
until the Nushagak River below the Mulchatna River confluence, about 122 miles downstream of
the mine site. Cadmium and molybdenum would remain at levels exceeding the most stringent
WQC as far downstream as the Nushagak River Estuary, about 230 miles downstream from the
mine site. The modeled extent of elevated metals for this scenario is shown in Figure 6-1.
• Fish and other aquatic organisms would be simultaneously affected by the elevated TSS and metals
concentrations in the water, leading to physical injury, loss of habitat and food, and lethal metals
toxicity. In the short term, and immediately downstream of the spill, lethal acute metal toxicity may
occur in fish species and other sensitive aquatic species. Over days to weeks in downstream
locations, sub-lethal effects, such as impairment of olfaction, behavior, and chemo/mechanosensory
responses, may also occur in these receptors, specifically due to copper. Impacts from elevated
metals could last for 5 to 6 weeks after the pyritic release scenario, while TSS impacts could last for
months to years, depending on the effectiveness of stream restoration efforts.
• Although predicted mercury concentrations in tailings are low, even very low amounts of total
mercury could result in bioaccumulation and biomagnification in fishes.
• Commercial fishing could be affected, depending on impacts to fish in the affected drainages.
Recreational anglers fishing these waters could experience a temporary reduction in harvest rates
or catch per unit effort rates if the sub-lethal effects reduced target species' ability or desire to feed
or strike at anglers' lures.
• Tailings spills could cause psychosocial stress resulting from community anxiety over a tailings
release, particularly in areas of valued subsistence and fishing activities. There could be exposures
to potentially hazardous materials, including metals, particularly in the pyritic tailings release.
Subsistence users may choose to avoid the area and alter their harvest patterns, due to actual and
potential perceptions of subsistence food contamination that extend throughout the area.
In the event of a tailings release, efforts would be made to recover tailings. A small release near the mine
site could be recoverable. However, once tailings are actively transported downstream full recovery
efforts may not be practicable or possible. This issue is discussed further in Section 6.2.2.
Recommended Determination
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December 2022
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Section 6
Other Concerns and Considerations
Figure 6-1. Modeled extent of elevated metals downstream of pyritic tailings release. Figure 4.27-4 from the FEIS
(USAGE 2020a: Section 4.27)
9*'
.of
?.fe
foi
,1*
South P"rk
Iliamna
Newhalen
KOKTULI RIVER BELOW NFK
AND SFK CONFLUENCE
DILUTION RATIO ACHIEVED FOR COPPER
Iliamna
Lake
Syi<*al
tliRwer
DillirigliHivt/
•
% '"<3*
I
Clark's Point
Ekuk
~ South Naknek
Sources: KP 2018o; PLP 2019-RFI153
US Army Corps
of Engineers
$
10 0 10 20
~
Location of Release
O Dilution Ratio Achieved
Modeled Rivers
Mine Site
MODELED EXTENT OF ELEVATED METALS
DOWNSTREAM OF BULK TAILINGS RELEASE
PEBBLE PROJECT EIS
FIGURE 4.27-4
Recommended Determination
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Section 6
Other Concerns and Considerations
6,2.1,3 Untreated Contact Water Release
Untreated contact water is surface water or groundwater that has been in contact with mining
infrastructure or mining wastes. Under the 2020 Mine Plan, contact water would be stored in several
facilities, including the main WMP, the open pit WMP, and six seepage collection ponds downstream of
the TSFs. The main WMP is the largest water storage facility and would include a 750- to 825-acre
reservoir contained by a 150-ft-high embankment. According to the FEIS, the main WMP would be
among the largest lined water storage reservoirs in the world. The FEIS predicts that contact water
would contain elevated levels of several metals in exceedance of WQC. The FEIS evaluates a scenario of a
slow release of untreated contact water from the main WMP over a month for a total release of 5.3
million cubic feet into the NFK. The scenario was developed by USACE based on the ElS-Phase FMEA.
The FEIS determines that the release could result in the following impacts:
• Untreated contact water released into the downstream drainages would contain elevated levels of
aluminum, arsenic, beryllium, cadmium, copper, lead, manganese, mercury, molybdenum, nickel,
selenium, silver, and zinc in exceedance of the most stringent aquatic life WQC. The released
untreated contact water would be diluted by stream water as it flows downstream, yet some metal
concentrations could remain elevated above WQC for up to 45 miles downstream of the mine site;
exceedances would last through the duration of the release.
• Impacts to fish from the release of untreated contact water would be similar to those described for
elevated metal impacts from the pyritic tailings release scenario. Acute toxicity due to metals would
not likely occur; however, prolonged exposure to metal concentrations in slight exceedance of WQC
may result in sub-lethal effects.
• Commercial fishing could be affected, depending on impacts to fish in the affected drainages.
Recreational anglers fishing these waters could experience a temporary reduction in harvest rates
or catch-per-unit effort rates if the sub-lethal effects reduced target species' ability or desire to feed
or strike at anglers' lures.
• Subsistence users may choose to avoid the area and alter their harvest patterns. Spills of untreated
contact water could cause psychosocial stress, particularly in areas of valued subsistence and fishing
activities.
6.2.2 Tailings Dam Failure
While the FEIS assesses impacts of a partial breach of the pyritic TSF, as discussed above, it does not
quantify or model the extent of impacts that could be caused by a catastrophic failure of the pyritic or
bulk TSF dams. USACE determined that a full breach analysis was not necessary because it determined
that the probability that a full breach could occur is very remote based on the tailings management plans
and TSF designs.
However, EPA believes there could be uncertainty with this conclusion due to the conceptual nature of
the TSF designs, potential future changes to the TSF water balances due to climate change, the
Recommended Determination
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December 2022
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Section 6
Other Concerns and Considerations
possibility that design or operational changes could occur during implementation, and the very long
time frames over which the bulk TSF dams would need to be maintained. In addition, the FEIS identifies
that there is uncertainty associated with the ability of the bulk tailings to drain sufficiently, which would
result in the majority of the tailings remaining in a saturated condition and a higher phreatic surface
than assumed in the main dam drainage design. The FEIS identifies that this could be monitored during
operations and corrected by changes to designs of future dam raises. The FEIS acknowledges that the
common factor in all major TSF failures has been human error, including errors in design, construction,
operations, maintenance, and regulatory oversight. Even well-designed dams can fail due to human
errors during construction or operations. FEIS Appendix K4.27 includes a review of recent tailings dam
failures including Mount Polley (Canada, 2014), Fundao (Brazil, 2015), Cadia (Australia, 2018), and
Feijao (Brazil, 2019). Some of these failures have caused severe environmental damage and fatalities. It
is possible that the 2020 Mine Plan TSF failure probabilities are very low as described in the FEIS
(USACE 2020a: Section 4.27). However, due to the uncertainties described above and in the FEIS, the
public interest in this issue, and the likely severe environmental consequences of a failure, EPA believes
that it is appropriate to describe potential impacts of a failure scenario.
EPA evaluated potential dam failure scenarios in the BBA. The quantitative aspects of the BBA scenarios
are not applicable to the 2020 Mine Plan due to differences in the TSF designs and assumptions.
However, some of the general conclusions regarding the potential for severe impacts on aquatic
resources if such an event were to occur are still applicable. In addition, the FEIS contains a general
discussion of the fate and behavior of released tailings from which a potential range of impacts can be
discerned.
Failure of the bulk TSF main dam would result in the release of a thickened tailings slurry into the NFK.
The FEIS estimates that a release from the bulk TSF main dam would travel only about 2.2 miles
downstream due to the thickened nature of the tailings. However, as noted above, it is possible that the
tailings could remain saturated, which would result in more fluidized conditions and would travel
further. In addition, the FEIS notes that slumping can occur and that upon entering a flowing stream,
tailings particles would become entrained in the water and be carried further downstream. Failure of
any of the fluid-filled pyritic TSF dams would result in a flood of water and tailings slurry, which could
move far downstream.
Tailings slurry releases can result in the following effects:
• Spilled tailings would bury habitat and streamflow would transport some of the spilled tailings
downstream, where further deposition would occur, burying stream substrate and altering habitat.
• Tailings entrained in water would create turbid water conditions and sedimentation downstream.
Upstream erosion would also contribute to ongoing downstream turbidity and sedimentation.
• Downstream sedimentation and elevated TSS and turbidity would continue until spilled tailings are
recovered, naturally flushed out of the drainage, or incorporated into the bedload. Complete
recovery of spilled tailings is not possible, because tailings spilled in flowing water would be widely
Recommended Determination
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December 2022
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Section 6
Other Concerns and Considerations
dispersed. If no tailings were recovered or if the volume of release was extremely high, decades to
centuries may be required to naturally flush tailings out of the drainages.
• Metals could leach from unrecovered tailings on a timescale of years to decades. Metals that
accumulate in streambed sediments could adversely affect water quality on a timescale of decades.
• The bulk tailings fluid contains antimony, arsenic, beryllium, cadmium, copper, lead, manganese,
mercury, molybdenum, selenium, zinc, total dissolved solids, hardness, and sulfate in exceedance of
WQC. Water quality characteristics of the pyritic TSF fluids are discussed in Section 6.2.1. Elevated
metals and other constituents contained in released tailings process fluids would affect water
quality downstream. Released fluids would be diluted by stream water, but streams could fail to
meet WQC for many miles downstream. Depending on the volume and the rate of release, the
downstream water quality would be in exceedance of WQC for an unknown length of time and an
unknown distance before the released fluid is sufficiently diluted below WQC.
• Deposited tailings would severely degrade habitat quality for fishes and the invertebrates they eat
due to extensive smothering effects. In addition, based largely on their copper content, deposited
tailings would be toxic to benthic macroinvertebrates; existing data concerning toxicity to fishes are
less clear.
• The affected streams would provide low-quality spawning and rearing habitat for decades.
• Recovery of suitable substrates via mobilization and transport of tailings would take years to
decades and would affect much of the watershed downstream of the failed dam.
• For some years, periods of high streamflow would be expected to suspend sufficient concentrations
of tailings to cause avoidance, reduced growth and fecundity, and even death of fishes.
• Loss of NFK fishes downstream of the TSF and additional fish losses in the mainstem Koktuli,
Nushagak, and Mulchatna Rivers would be expected to result from these habitat losses.
The extent of water quality changes and habitat and fisheries losses due to failure of any of the TSF dams
would depend on many factors, including when the breach occurs during the operational life of the
facility, the amount of tailings released, the water content of the tailings, the speed and duration of
release, seasonality (winter vs spring/summer conditions), and failure mode. However, the extent of
impacts would go much further beyond the extent of the bulk TSF pipeline release and pyritic TSF
partial breach described in the FEIS and summarized in Section 6.2.1, and the duration of impacts would
be much longer. The USACE ROD acknowledges that although the probability of a full dam breach is low,
the consequences would be high and catastrophic failure could have severe and irreversible impacts to
subsistence, commercial, and recreational fisheries. USACE states "In the event of human error and/or a
catastrophic event, the commercial and/or subsistence resources would be irrevocably harmed, and
there is no historical scientific information from other catastrophic events to support restoration of the
fishery to its pre-impacted state" (USACE 2020b: Page B3-27).
Recommended Determination
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Section 6
Other Concerns and Considerations
6.3 Other Tribal Concerns
EPA's policy is to consult on a government-to-government basis with federally recognized tribal
governments whenever EPA actions and decisions may affect tribal interests, consistent with Executive
Order 13175, Consultation and Coordination with Indian Tribal Governments.89 Consultation is a process
of meaningful communication and coordination between EPA and tribal officials. Separately, pursuant to
Public Law 108-199,118 Stat. 452, as amended by Public Law 108-447,118 Stat. 3267, EPA is required
to consult and engage with Alaska Native Corporations on the same basis as tribes under Executive
Order 13175.90
Throughout development of the BBA (EPA 2014: Chapter 1), the 2014 Proposed Determination, and the
2017 proposal to withdraw the 2014 Proposed Determination, EPA Region 10 provided opportunities
for consultation and coordination with federally recognized tribal governments, as well as consultation
and engagement with Alaska Native Corporations. On all actions, EPA invited all 31 Bristol Bay tribal
governments and all 26 Alaska Native Corporations in Bristol Bay to participate.
On January 27, 2022, EPA Region 10 sent letters inviting consultation to all 31 tribal governments
located in the Bristol Bay watershed. Separately, it also invited consultation with 5 Alaska Native
Corporations and offered engagement to 21 Alaska Native Corporations with lands in the Bristol Bay
watershed. EPA Region 10 hosted three informational webinars for tribal governments and one
informational webinar for Alaska Native Corporations to review the CWA Section 404(c) process and
answer questions. In addition, EPA Region 10 engaged in multiple consultations with tribal governments
and Alaska Native Corporations between February and October 2022. EPA will continue to provide
opportunities for tribal consultation and coordination and consultation and engagement with Alaska
Native Corporations going forward.
This section describes additional concerns and information that may affect tribal interests regarding
potential effects of discharges of dredged or fill material associated with mining of the Pebble deposit on
subsistence use, traditional ecological knowledge (TEK), and environmental justice.
6.3.1 Subsistence Use and Potential Mining Impacts
The use and importance of subsistence fisheries in the Nushagak and Kvichak River watersheds and the
SFK, NFK, and UTC watersheds are discussed in detail in Section 3.3.6. Although salmon and other fish
provide the largest portion of subsistence harvests for Bristol Bay communities, non-fish resources
89 In May 2011, EPA issued the EPA Policy on Consultation and Coordination with Indian Tribes, which established
national guidelines and institutional controls for consultation. In October 2012, EPA Region 10 issued the EPA
Region 10 Tribal Consultation and Coordination Procedures, which established regional procedures for the
consultation process. On January 26, 2021, President Biden issued the Presidential Memorandum, Tribal
Consultation and Strengthening Nation-to-Nation Relationships, which charges each federal agency to engage in
regular, meaningful, and robust consultation and to implementthe policies directed in Executive Order 13175.
90 As described in EPA's Guiding Principles for Consulting with Alaska Native Claims Settlement Act Corporations
(EPA 2021), it is EPA's practice to consult with Alaska Native Corporations on a regulatory action that has a
substantial direct effect on an Alaska Native Corporation and imposes substantial direct compliance costs and to
notify Alaska Native Corporations of impending agency actions that may be outside of the scope of consultation.
Recommended Determination
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Section 6
Other Concerns and Considerations
make up a significant portion of subsistence use (Table 6-2). On average, non-fish resources, such as
moose, caribou, waterfowl, plants, and other organisms represent just over 30 percent of subsistence
harvests by local communities (Table 6-2). The relative importance of non-fish subsistence resources
varies throughout the Bristol Bay watershed, and per capita subsistence harvest of non-fish resources
exceeds fish harvests in two communities (Table 6-2).
Table 6-2.
Aleknagik
2008
51,738
296
169
127
Dillingham
2010
486,533
212
138
74
Ekwok
1987
77,268
793
524
269
Igiugig
2005
22,310
541
264
277
lliamna
2004
34,160
469
404
65
Kokhanok
2005
107,644
680
549
131
Koliganek
2005
134,779
898
655
243
Levelock
2005
17,871
527
192
335
New Stuyahok
2005
163,927
389
216
173
Newhalen
2004
86,607
692
534
158
Nondalton
2004
58,686
357
253
104
Pedro Bay
2004
21,026
305
265
40
Port Alsworth
2004
14,489
133
101
32
Notes:
a Total harvest values represent usable weight and include fishes, land mammals, freshwater seals, beluga, other marine mammals, plant-based
foods, birds or eggs, and marine invertebrates.
Sources: Schichnes and Chythlook 1991 (Ekwok), Fall et al. 2006 (lliamna, Newhalen, Nondalton, Pedro Bay, and Port Alsworth); Krieg et al. 2009
(Igiugig, Kokhanok, Koliganek, Levelock, New Stuyahok); Holen et al. 2012 (Aleknagik); Evans et al. 2013 (Dillingham).
Numerous studies on TEK have been completed for the Nushagak and Kvichak River watersheds.91
These studies provide extensive information from villages in the watersheds, including primary and
secondary subsistence species, subsistence use areas and critical habitat, subsistence practices, and
observed changes in abundance and timings for subsistence species (Boraas and Knott 2013). For
example, the Nushagak River Watershed Traditional Use Area Conservation Plan identifies that the
species most integral to subsistence were all five species of Pacific salmon, whitefish, winter freshwater
fish, moose, caribou, waterfowl, and edible and medicinal plants. The plan also identified probable
threats to the watershed and identified as one of its strategic actions "preventing] habitat damage that
could result from mining" (NMWC 2007: Page 3). Section 6.3.2 provides more information about the role
of TEK in the Bristol Bay watershed.
91 Boraas and Knott (2013) summarized additional studies in Appendix D of the BBA (EPA 2014).
Recommended Determination g ^g December 2022
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Section 6
Other Concerns and Considerations
Figure 6-2 highlights areas of subsistence use for fish, wildlife, and waterfowl in the Nushagak and
Kvichak River watersheds as identified in the FEIS (USACE 2020a: Table 3.9-1). Subsistence use patterns
do not follow watershed boundaries, and communities outside the Nushagak and Kvichak River
watersheds also rely on these areas for subsistence resources. For example, Clark's Point subsistence
use areas for caribou and moose overlap with the Nushagak and Kvichak River watersheds; South
Naknek, Naknek, and King Salmon subsistence use areas for waterfowl, moose, and berry picking, as
well as caribou search areas, overlap both watersheds, particularly the Kvichak (Holen et al. 2011).
Subsistence data are coarse and incomplete, and it is likely that subsistence activities occur outside the
areas identified in Figure 6-2. In addition, Figure 6-2 indicates only use, not abundance or harvest.
In Section 4, EPA Region 10 considers potential effects of discharges of dredged or fill material
associated with mining of the Pebble deposit at the levels derived from the 2020 Mine Plan on the
region's fishery resources. All subsistence resources could be directly affected by discharges associated
with the identified mining activities, for example, via habitat destruction or modification of habitat use
by different subsistence species. In addition, non-salmon subsistence resources could be indirectly
affected by any adverse effects on salmon fisheries that result from discharges associated with the mine;
as explained in Section 3.3.6.1, the loss or reduction of salmon populations would have repercussions on
the productivity of the region's ecosystems.
Any effects on fish—particularly salmon—and other subsistence resources that result from discharges
associated with the mine could have significant adverse effects on the Bristol Bay communities that rely
on these subsistence foods (EPA 2014: Chapter 12). Given the nutritional and cultural importance of
salmon and other subsistence foods to Alaska Native populations, these communities would be
especially vulnerable to impacts to subsistence resources; however, non-Alaska Native populations in
the region also rely heavily on subsistence resources.
As discussed in EPA (2014) and Section 4 above, routine development and operation of a large-scale
mine at the Pebble deposit would likely affect salmon and other important fish resources in the
Nushagak and Kvichak River watersheds. The FEIS confirms that the 2020 Mine Plan would result in
adverse impacts to the availability of and access to subsistence resources (USACE 2020a: Section 4.9).
Although no subsistence salmon fisheries are documented directly in the 2020 proposed mine site,
subsistence use of the mine area is high and centers on hunting caribou and moose and trapping small
mammals (PLP 2011: Chapter 23). Tribal Elders have expressed concerns about ongoing mine
exploration activities directly affecting wildlife resources, especially the caribou herd range (EPA 2014:
Appendix D). Tribal members and subsistence hunters have anecdotally reported to EPA that noise
during the exploration phase of the Pebble deposit has already disturbed moose populations and altered
caribou migration patterns (EPA 2018).
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Section 6
Other Concerns and Considerations
Figure 6-2. Subsistence use intensity for salmon, other fishes, wildlife, and waterfowl within the Nushagak and
Kvichak River watersheds. Figure 3.9-1 from the FEIS (USAGE 2020a: Section 3.9).
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Section 6
Other Concerns and Considerations
Negative impacts to downstream fisheries from headwater disturbance (Section 4) could affect
subsistence fish resources beyond the mine footprint. Those residents using the upper reaches of the
SFK, NFK, and UTC rivers downstream of the mine footprint for subsistence harvests would be most
affected. Access to subsistence resources is also important. A reduction in downstream seasonal water
levels caused by mine-related withdrawals during and after mine operation could pose obstacles for
subsistence users who depend on water for transportation to fishing, hunting, gathering, or other
culturally important areas.
Changes in subsistence resources may affect the health, welfare, and cultural stability of Alaska Native
populations in several ways (EPA 2014: Appendix D):
• The traditional diet is heavily dependent on wild foods. If fewer subsistence resources were
available, diets would move from highly nutritious wild foods to increased reliance on purchased
processed foods.
• Social networks are highly dependent on procuring and sharing wild food resources, so the current
social support system would be degraded.
• The transmission of cultural values, language learning, and family cohesion would be affected
because meaningful family-based work takes place in fish camps and similar settings for traditional
ways of life.
• Values and belief systems are represented by interaction with the natural world through salmon
practices, clean water practices, and symbolic rituals. Thus, core beliefs would be challenged by a
loss of salmon resources, potentially resulting in a breakdown of cultural values, mental health
degradation, and behavioral disorders.
• The region exhibits a high degree of cultural uniformity tied to shared traditional and customary
practices, so significant change could provoke increased tension and discord both between villages
and among village residents.
Dietary transition away from subsistence foods in rural Alaska carries a high risk of increased
consumption of processed simple carbohydrates and saturated fats, which has occurred in urban
communities that have low availability and high cost of fresh produce, fruits, and whole grains (Kuhnlein
et al. 2001, Bersamin et al. 2006). Available alternative food sources may not be economically obtainable
and are not as healthful. Section 3 describes the replacement value of subsistence salmon. Compounding
the detrimental shift to a less healthful diet, the physical benefits of engaging in a subsistence lifestyle
also would be reduced (EPA 2014: Appendix D).
The magnitude of human health and cultural effects related to potential decreases in resources would
depend on the magnitude of these reductions. A small reduction in salmon quality or quantity may not
have significant impacts on subsistence food resources, human health, or cultural and social
organization. However, a significant reduction in salmon quality or quantity would significantly
negatively affect these salmon-based cultures. Ultimately, the magnitude of overall impacts would
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Section 6
Other Concerns and Considerations
depend on many factors, including the location and temporal scale of effects, cultural resilience, the
degree and consequences of cultural adaptation, and the availability of alternative subsistence
resources.
However, even a negligible reduction in salmon quantity or quality related to mining activities could
decrease use of salmon resources, based on the perception of subtle changes in the salmon resource.
Interviews with tribal Elders and culture bearers indicate that perceptions of subtle changes to salmon
quality are essential to subsistence users, even if there are no measurable changes in the quality and
quantity of salmon (EPA 2014: Appendix D). In addition to actual exposure to environmental
contamination, the perception of exposure to contamination is linked to known health consequences,
including stress and anxiety about the safety of subsistence foods and avoidance of subsistence food
sources (Joyce 2008, CEAA 2010, Loring et al. 2010, USACE 2020a: Section 4.9).
The 2020 Mine Plan would likely adversely affect access to subsistence harvest areas, as well as the
availability, abundance, and quality of subsistence resources, due to impacts on fishery areas
(Section 4.2) and wildlife (Section 6.1.1). These impacts would endure long beyond mine closure, though
with diminishing intensity following closure, unless there are any impoundment failures creating mine
waste releases. The FEIS confirms reduced availability of subsistence resources due to habitat loss,
disturbance, displacement, and contamination from fugitive dust deposition. The FEIS also states that
the reduction of available harvest areas would result in increased costs and time for traveling to
alternative harvest areas (USACE 2020a: Section 4.9). However, this assumes that subsistence users
would adapt to changes in harvest areas. EPA recognizes that subsistence users may not adapt to these
changes due to the ability, capacity, or cultural willingness to access alternate areas and make dietary
substitutions across all sectors of the population. Increased economic opportunity and income could
enable subsistence users to afford necessary subsistence technologies, but could also reduce time
available for subsistence practices, thereby decreasing harvest yields and subsistence sharing in
communities (USACE 2020a: Section 4.9).
Further, the FEIS confirms that long-term sociocultural impacts to subsistence users and communities
could occur due to the adverse impacts to resource abundance, availability, quality, and access due to
the 2020 Mine Plan. These sociocultural impacts could result in adverse effects on community health
and well-being, cultural identity and continuity, traditional knowledge transfer, language, spirituality,
and social relations (USACE 2020a: Section 4.9).
6.3.2 Traditional Ecological Knowledge
In November 2021, the White House issued a memo, Indigenous Traditional Ecological Knowledge and
Federal Decision Making, regarding the federal government's commitment to incorporate indigenous
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Other Concerns and Considerations
traditional ecological knowledge92 (ITEK) into its decision-making and scientific inquiry where
appropriate. As defined by the White House memo:
ITEK is a body of observations, oral and written knowledge, practices, and beliefs that promote
environmental sustainability and the responsible stewardship of natural resources through relationships
between humans and environmental systems. It is applied to phenomena across biological, physical,
cultural and spiritual systems. ITEK has evolved over millennia, continues to evolve, and includes insights
based on evidence acquired through direct contact with the environment and long-term experiences, as
well as extensive observations, lessons, and skills passed from generation to generation. ITEK is owned
by Indigenous people—including, but not limited to, Tribal Nations, Native Americans, Alaska Natives,
and Native Hawaiians.
In the Nushagak and Kvichak watersheds, home primarily to the Yup'ik and Dena'ina, indigenous
peoples have been harvesting wild resources for at least 12,000 years and harvesting salmon for at least
4,000 years. Salmon and other subsistence resources continue to make up the large majority of the diet
in the Nushagak and Kvichak River watersheds. For millennia, the Yup'ik and Dena'ina peoples and their
predecessors have depended on the ecosystems that support salmon and other wild resources, and for
millennia these ecosystems have remained relatively pristine (Section 3). Traditional subsistence
management practices have proven to be sustainable in the Bristol Bay watershed (Boraas and Knott
2013).
The Yup'ik and Dena'ina cultures are inseparably connected to wild salmon and subsistence resources,
with one Bristol Bay resident stating that salmon "defines who we are" (Boraas and Knott 2013: Page 1).
Parents, grandparents, and Elders transfer knowledge about fish-harvesting practices and the
environment to younger generations through demonstration and supervision (Boraas and Knott 2013,
USACE 2020a: Section 4.9). The transmission of cultural values, language learning, and family cohesion
often takes place in fish camps and similar settings for traditional ways of life (Boraas and Knott 2013).
Social mechanisms, such as rituals, folklore, and language, all serve to encode and transmit TEK (Berkes
et al. 2000). For instance, the Dena'ina words to indicate direction are based on the concept of upstream
or downstream rather than cardinal direction (Boraas and Knott 2013).
Subsistence users in the Bristol Bay watershed are uniquely positioned to track important subsistence
metrics, including primary and secondary subsistence species, subsistence use areas and critical habitat,
subsistence practices, and observed changes in abundance and timings for subsistence species (Boraas
and Knott 2013). Historically, TEK was primarily used in western science to compare and confirm the
presence of species documented by indigenous peoples against those documented by western scientists
(Knott 1998). More recently, western scientists have begun to include the larger body of TEK into their
research, including to inform land and species management plans (Boraas and Knott 2013). The Alaska
Department of Fish and Game, for instance, has begun to incorporate some TEK into subsistence reports
and databases for the Bristol Bay and Alaska Peninsula region, identifying information, such as
92 There are many terms and definitions used to refer to the concept of traditional ecological knowledge, such as
"cultural knowledge," "indigenous knowledge," and "native science." The White House memo refers to this concept
as "indigenous traditional ecological knowledge" or "ITEK." The FEIS refers to this concept as "traditional
knowledge." This recommended determination uses the term "traditional ecological knowledge" or "TEK"
consistent with the BBA.
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Other Concerns and Considerations
taxonomy, subsistence use, harvest areas, and changes to local salmon stocks (Kenner 2003,
ADF&G 2020).
Traditional management of wild resources, especially salmon, incorporates a deep recognition of the
connection between communities and ecosystems (Boraas and Knott 2013, Berkes et al. 2000).
Incorporating TEK into fisheries management can promote more equitable fishing opportunities for
communities (Atlas et al. 2021). This is apparent in interviews with Alaska Native Bristol Bay residents,
with one resident stating "when the fish first come up here we don't put our nets out here before a
bunch of them go by for the people who live at the end of the river up in Nondalton and all those guys...
We just kind of watch the salmon go by for the people who live upstream from us" (Boraas and
Knott 2013: Page 100).
TEK is incorporated more substantially in watershed- and community-level reports in the region. The
Nushagak-Mulchatna Watershed Conservation Plan (NMWC 2007) conducted interviews with
watershed Elders, residents, and others to develop maps of critical subsistence resources and habitats,
identify traditional use areas, and document subsistence species. These data were used to inform a
conservation plan for the watershed, which included identification of probable threats and strategic
actions. The K'ezghlegh: Nondalton Traditional Ecological Knowledge of Freshwater Fish study (Stickman
et al. 2003) documented TEK regarding subsistence salmon and other freshwater fish harvest through
interviews with Nondalton residents. Residents provided observed changes in salmon run strength and
timing, salmon appearance, environment, and the impacts of human activities on salmon and other
freshwater fishes. TEK can enhance understanding of the spatial patterns of subsistence species,
facilitate planning for long-term monitoring, improve management practices, track climate and
environmental change, and contribute to local-capacity building for research (Berkes et al. 2000, USFWS
2011, Woll et al. 2013, Atlas et al. 2021).
TEK is inherently connected to the millennia-long subsistence way of life in Bristol Bay. The subsistence
lifestyle enables Alaska Native Bristol Bay residents to continue to develop, evolve, and pass down their
knowledge of the ecosystems supporting subsistence resources. As described in Section 6.3.1 and the
FEIS, the 2020 Mine Plan could adversely affect participation in subsistence activities due to impacts to
subsistence resource availability, abundance, and quality; changes in the perception of subsistence
resource quality; personal comfort harvesting near mining facilities; and time available due to
alternative, cash-paying employment. As described in the FEIS, changes such as these could have a
"compounding effect on the subsistence way of life" by decreasing the transmission of TEK to younger
generations (USACE 2020a: Page 4.9-12). Further, retention of TEK for traditional subsistence harvest
areas and resources could be lost as subsistence users adapt to alternative areas and resources (USACE
2020a: Section 4.9).
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Other Concerns and Considerations
6.3.3 Environmental Justice
In discussing environmental justice issues, it is useful to consider the following terms, as defined by EPA:
• Environmental justice is defined as the fair treatment and meaningful involvement of all people,
regardless of race, color, national origin, or income, with respect to the development,
implementation, and enforcement of environmental laws, regulations, and policies.
• Fair treatment means that no group of people should bear a disproportionate burden of
environmental harms and risks, including those resulting from negative environmental
consequences of industrial, governmental, and commercial operations or programs and policies.
• Meaningful involvement means that potentially affected community members have an appropriate
opportunity to participate in decisions about a proposed activity that will affect their environment
and/or health; the public's contribution can influence EPA's decisions; the concerns of all
participants involved will be considered in the decision-making process; and the decision-makers
seek out and facilitate the involvement of those potentially affected.
Executive Order 12898, titled Federal Actions to Address Environmental Justice in Minority Populations
and Low-Income Populations, and its accompanying presidential memorandum establish executive
branch policy on environmental justice. To the greatest extent practicable and permitted by law,
Section 1-101 of the Executive Order directs each federal agency, as defined in the Executive Order, to
make environmental justice part of its mission by identifying and addressing, as appropriate,
disproportionately high and adverse human health or environmental effects of its programs, policies,
and activities on minority and low-income populations.
Furthermore, Section 4-401 of the Executive Order states the following about subsistence consumption
of fish and wildlife:
In order to assist in identifying the need for ensuring protection of populations with differential patterns
of subsistence consumption of fish and wildlife, Federal agencies, whenever practicable and appropriate,
shall collect, maintain, and analyze information on the consumption patterns of populations who
principally rely on fish and/or wildlife for subsistence. Federal agencies shall communicate to the public
the risks of those consumption patterns.
In implementing the Executive Order, EPA considers whether there would be "disproportionately high
and adverse human health or environmental effects" from its regulatory action and ensures meaningful
involvement of potentially affected minority or low-income communities. The scope of the inquiry for
any environmental justice analysis by EPA is directly tied to the scope of EPA's potential regulatory
action. Because a CWA Section 404(c) action has the potential to affect human health and the
environment of minority or low-income populations, including tribal populations, EPA evaluates
environmental justice concerns when undertaking an action pursuant to its authorities under CWA
Section 404(c).
Though not addressed in Executive Order 12898, the issues and concerns shared with EPA by federally
recognized tribal governments during consultation meetings will be considered in the environmental
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Other Concerns and Considerations
justice analysis because of related issues and concerns among Alaska Native communities regarding
safety of subsistence foods and cultural impacts, including the sustainability of the subsistence way of
life. Consultation is discussed further in Section 6.3.4.
The Bristol Bay communities of the Nushagak and Kvichak River watersheds are predominantly Alaska
Native, primarily Yup'ik and Dena'ina (EPA 2014: Chapter 5). Although there are other Bristol Bay
communities that are concerned with potential impacts to fishery resources and, consequently, their
way of life, EPA Region 10 focused on communities who practice subsistence within the SFK, NFK, and
UTC watersheds for this environmental justice analysis.
As described in Section 2, EPA has conducted extensive community outreach throughout its engagement
in the Bristol Bay watershed. Public hearings or meetings were held in May and June 2012, August 2012,
August 2014, October 2017, and June 2022, in which community members expressed concerns about
the potential impacts of large-scale mining on Alaska Natives' subsistence way of life. Community
members expressed concern about adverse environmental and cultural aspects of the project. They also
expressed concerns about job loss, the sustainability of villages (e.g., schools closing because enrollment
drops as parents make tough choices to go where jobs are available), potential tax revenue, Alaska
Native Corporation economic opportunities, and the State of Alaska's concerns regarding economic
opportunities for the citizens of Alaska.
Traditional and more modern spiritual practices place salmon in a position of respect and importance,
as exemplified by the First Salmon Ceremony and the Great Blessing of the Waters, which symbolically
purifies the water in preparation for return of the salmon. The salmon harvest provides a basis for many
important cultural and social practices and values, including sharing resources, fish camp, gender and
age roles, and the perception of wealth. Although a small minority of tribal Elders and culture bearers
interviewed expressed a desire to increase market economy opportunities (including large-scale
mining), most equated wealth with stored and shared subsistence foods. In interviews conducted for the
BBA (Appendix D), the Yup'ik and Dena'ina communities of the Nushagak and Kvichak River watersheds
consistently define a "wealthy person" as one with food in the freezer, a large extended family, and the
freedom to pursue a subsistence way of life in the manner of their ancestors, Further, interviews of
residents in the Nushagak and Kvichak River watersheds described subsistence as a year-round, full-
time occupation. However, subsistence is not captured in labor statistics because it is not based on
wages or a salary (EPA 2014: Appendix D).
The Alaska Native community also depends in part on the regional economy, which is primarily driven
by commercial salmon fishing and tourism. The commercial fishing and recreation-based market
economies provide seasonal employment for many residents, giving them both the income to purchase
goods and services needed for subsistence and the time to participate year-round in subsistence
activities. The fishing industry provides half of all jobs in the region, followed by government (32
percent), recreation (15 percent), and mineral exploration (3 percent) (EPA 2014: Appendix E). It is
estimated that local Bristol Bay residents held one-third of all jobs and earned almost $78 million (28
Recommended Determination
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Section 6
Other Concerns and Considerations
percent) of the total income traceable to the Bristol Bay watershed's salmon ecosystems in 2009 (EPA
2014: Appendix E).
The Bristol Bay Regional Vision Project convened over 50 meetings in 26 communities in 2011 to create
a guidance document for communities, regional organizations, and all entities that have an interest in
the Bristol Bay region. Their final report stated that the residents of the Bristol Bay watershed want
"excellent schools, safe and healthy families, local jobs, access to subsistence resources, and a strong
voice in determining the future direction of the region" (Bristol Bay Vision 2011: Page 1).
Several common themes emerged during this process, which were similar to themes reflected in public
comments EPA received during development of the BBA:
• Family, connection to the land and water, and subsistence activities are the most important parts of
people's lives, today and in the future.
• Maintaining a subsistence focus by teaching children how to engage in subsistence activities and
encouraging good stewardship practices is important.
• People welcome sustainable economic development that is based largely on renewable resources.
Any large development must not threaten land or waters.
• True economic development will require a regionally coordinated approach to reduce energy costs,
provide business training, and ensure long-term fish stock protection.
• There should be joint planning meetings among tribes, local governments, and Corporations to
create community-wide agreement on initiatives or projects.
Development of the Pebble Mine would result in employment opportunities in the region, primarily for
those communities nearest the mine site (Nondalton, Iliamna, and Newhalen), leading to increased
revenues and year-round job opportunities throughout the lifespan of the mine, though these jobs could
vary based on economic conditions and business decisions. Increased revenue in the region may lead to
investments in infrastructure and services, and provide revenue needed for subsistence hunters and
anglers to purchase subsistence-related technology and equipment (USACE 2020a: Section 4.9).
As discussed in Sections 3.3.6 and 6.3.1, subsistence foods make up a substantial proportion of the
human diet in the Nushagak and Kvichak River watersheds, and likely contribute a disproportionately
high amount of protein and certain nutrients.93 EPA acknowledges that human health within the
communities near the Pebble deposit is directly related to the subsistence way of life practiced by many
residents of these communities. Additionally, EPA recognizes that subsistence use areas and related
subsistence activities provide not only food but also support important cultural and social connections
within the region's communities. Social networks in the Bristol Bay region are highly dependent on
93 The BBA did not evaluate threats to human health due to physical exposure to discharged pollutants or
consumption of exposed organisms, because these effects were outside the scope of the assessment (EPA 2014:
Chapter 2).
Recommended Determination
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Other Concerns and Considerations
procuring and sharing wild food resources, especially for cash-poor households in which members are
unable to fish or hunt, such as Elders, single parents, or people with disabilities (ADF&G 2018). If a
significant adverse impact on the Nushagak and Kvichak River watersheds were to occur, the Alaska
Native community reliant on these areas for food supply and cultural and social connections could
experience disproportionately high and adverse effects.
6.4 Consideration of Potential Costs
EPA's consideration of these issues can be found in the revised draft document titled Consideration of
Potential Costs Regarding the Clean Water Act Section 404(c) Recommended Determination for the Pebble
Deposit Area, Southwest Alaska (EPA 2022).
Recommended Determination
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The EPA Region 10 Regional Administrator completed his review of the extensive administrative record,
including all public comments, and has determined that discharges of dredged or fill material into
waters of the United States for the construction and routine operation of the 2020 Mine Plan would be
likely to result in unacceptable adverse effects on anadromous fishery areas (Sections 4.2.1 through
4.2.4 of this recommended determination]. The Regional Administrator also has determined that
discharges of dredged or fill material associated with future plans to develop the Pebble deposit would
be likely to result in unacceptable adverse effects on anadromous fishery areas in the SFK, NFK, and UTC
watersheds if the effects of such discharges are similar or greater in nature and magnitude to those of
the 2020 Mine Plan described in Sections 4.2.1 through 4.2.4 of this recommended determination. Based
on these findings, the Regional Administrator recommends prohibiting and restricting the use of certain
waters in the SFK, NFK, and UTC watersheds as disposal sites for the discharge of dredged or fill
material associated with developing the Pebble deposit (Section 5 of this recommended determination].
Accordingly, the Regional Administrator determined that the appropriate next step in this CWA Section
404(c] review process is to transmit this recommended determination, along with the administrative
record, to EPA's Assistant Administrator for Water at EPA Headquarters for review and final action.
EPA's Assistant Administrator for Water will review this recommended determination and the
administrative record, including written public comments received on the 2022 Proposed
Determination, public hearing transcripts, and other information considered by the Regional
Administrator. After reviewing the recommendations of the Regional Administrator, the administrative
record, and any information provided by ADNR, PLP, Chuchuna Minerals, and USACE about their intent
to take corrective action to prevent unacceptable adverse effects, the Assistant Administrator will issue
a final determination affirming, modifying, or rescinding the Regional Administrator's recommended
determination.
12/1/2022
CASEY
SIXKILLER
Digitally signed by
CASEY SIXKILLER
Dated:
Date: 2022.12.01
12:10:26 -08'00'
Casey Sixkiller
Regional Administrator
EPA Region 10
Recommended Determination
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Achord, S., P. S. Levin, and R. W. Zabel. 2003. Density-dependent mortality in Pacific salmon: the ghost of
impacts past? Ecology Letters 6:335-342.
Ackerman, M. W., W. D. Templin, J. E. Seeb, and L. W. Seeb. 2013. Landscape heterogeneity and local
adaptation define the spatial genetic structure of Pacific salmon in a pristine environment.
Conservation Genetics 14:483-498.
ADEC (Alaska Department of Environmental Conservation). 2020.18AAC 70 Water Quality Standards,
Amended as of March 5, 2020.
ADF&G (Alaska Department of Fish and Game). 2018. Subsistence in Alaska: A Year 2017 Update.
Anchorage, AK: Alaska Department of Fish and Game, Division of Subsistence.
ADF&G. 2020. Subsistence Salmon Networks in Select Bristol Bay and Alaska Peninsula Communities, 2016.
Technical Paper No. 459. Anchorage, AK: Alaska Department of Fish and Game, Division of
Subsistence.
ADF&G. 2021a. 2022 Bristol Bay Sockeye Salmon Forecast. Anchorage, AK: Alaska Department of Fish and
Game, Division of Commercial Fisheries.
ADF&G. 2021b. 2021 Bristol Bay Salmon Season Summary. Anchorage, AK: Alaska Department of Fish
and Game, Division of Commercial Fisheries.
ADF&G. 2022a. Alaska Freshwater Fish Inventory (AFFI) database. Anchorage, AK: Alaska Department of
Fish and Game, Division of Sport Fish. Available:
http://www.adfg.alaska.gov/index.cfm?adfg=ffinventory.main. Accessed: February 22, 2022.
ADF&G. 2022b. Anadromous Waters Catalog: Overview. Alaska Department of Fish and Game. Anchorage,
AK. Available: https://www.adfg.alaska.gov/sf/SARR/AWC/index.cfm?ADFG=main.home. Accessed:
May 16, 2022.
ADF&G. 2022c. Anadromous Waters Catalog: Definitions. Alaska Department of Fish and Game.
Anchorage, AK. Available:
https://www.adfg.alaska.gov/sf/SARR/AWC/index.cfm?ADFG=defs.definitions. Accessed: October
17,2022.
ADF&G. 2022d. Gene Conservation Laboratory, Bristol Bay Sockeye Salmon Mixed Stock Analysis -
Application & Analysis. Anchorage, AK: Alaska Department of Fish and Game. Available:
https://www.adfg.alaska.gov/index.cfm?adfg=fishinggeneconservationlab.bbaysockeye_application.
Accessed: May 2, 2022.
Recommended Determination
8-1
December 2022
-------
Section 8
References
ADF&G. 2022e. 2022 Bristol Bay Salmon Season Summary. Anchorage, AK: Alaska Department of Fish and
Game, Division of Commercial Fisheries.
ADF&G. 2022f. Memorandum: Bristol Bay Management Area Stock of Concern Recommendations. Juneau,
AK: Alaska Department of Fish and Game, Divisions of Sport Fish and Commercial Fisheries. October
7.
ADNR (Alaska Department of Natural Resources). 1984a. Bristol Bay Area Plan for State Lands,
September 1984. Alaska Department of Natural Resources, Alaska Department of Fish and Game, and
Alaska Department of Environmental Conservation.
ADNR. 1984b. Mineral Closing Order No. 393 State of Alaska Department of Natural Resources Bristol Bay
Area Plan, September 1984.
ADNR. 2022a. Mineral Property Management. Alaska Department of Natural Resources. Available:
https://dnr.alaska.gov/mlw/mining/mpm/. Accessed: May 16, 2022.
ADNR. 2022b. Pebble Project. Available: http://dnr.alaska.gov/mlw/mining/largemine/pebble/.
Accessed: November 28, 2022.
ADNR. 2022c. Web feature service depicting active, pending, and closed state mining claims. Available:
https://arcgis.dnr.alaska.gov/arcgis/rest/services/OpenData/NaturalResource_StateMiningClaim/
MapServer. Accessed: May 9, 2022.
ADNR. 2022d. PLSS Protracted Section Aliquot Part Points, Seward Meridian Quarter Quarter Section
Points. Available: https://data-soa-dnr.opendata.arcgis.com/search?q=PLSS. Accessed: November 2,
2022.
Alexander, R. B., E. W. Boyer, R. A. Smith, G. E. Schwarz, and R. B. Moore. 2007. The role of headwater
streams in downstream water quality. Journal of the American Water Resources Association 43:41-
59.
Anderson, J. H., G. R. Pess, P. M. Kiffney, T. R. Bennett, P. L. Faulds, W. I. Atlas, and T. P. Quinn. 2013.
Dispersal and tributary immigration by juvenile coho salmon contribute to spatial expansion during
colonization. Ecology of Freshwater Fish 22:30-42.
Anderson, S. C., J. W. Moore, M. M. McClure, N. K. Dulvy, and A. B. Cooper. 2015. Portfolio conservation of
metapopulations under climate change. Ecological Applications 25:559-572.
Angilletta, M. J., E. A. Steel, K. K. Bartz, J. G. Kingsolver, M. D. Scheuerell, B. R. Beckman, and L. G. Crozier.
2008. Big dams and salmon evolution: changes in thermal regimes and their potential evolutionary
consequences. Evolutionary Applications 1:286-299.
Annear, T., I. Chisholm, H. Beecher, A. Locke, P. Aarrestad, C. Coomer, C. Estes, J. Hunt, R. Jacobson, G.
Jobsis, J. Kauffman, J. Marshall, K. Mayes, G. Smith, R. Wentworth, and C. Stalnaker. 2004. Instream
Flows for Riverine Resource Stewardship, Revised Edition. Cheyenne, WY: Instream Flow Council.
Recommended Determination
8-2
December 2022
-------
Section 8
References
Araki, H., B. Cooper, and M. S. Blouin. 2009. Carry-over effect of captive breeding reduces reproductive
fitness of wild-born descendants in the wild. Biology Letters 5:621-624.
Armstrong, J. B., and D. E. Schindler. 2013. Going with the flow: spatial distributions of juvenile coho
salmon track an annually shifting mosaic of water temperature. Ecosystems 16:1429-1441.
Armstrong, J. B., D. E. Schindler, K. L. Omori, C. P. Ruff, and T. P. Quinn. 2010. Thermal heterogeneity
mediates the effects of pulsed subsidies across a landscape. Ecology 91:1445-1454.
Armstrong, J. B., G. Takimoto, D. E. Schindler, M. M. Hayes, and M. J. Kauffman. 2016. Resource waves:
phenological diversity enhances foraging opportunities for mobile consumers. Ecology 97:1099-
1112.
Armstrong, R. H., and E. Morrow. 1980. The Dolly Varden charr, Salvelinus malma. Pages 99-140 in E. K.
Balon (ed.). Charrs: Salmonid Fishes of the Genus Salvelinus. The Hague, The Netherlands: Springer.
Arostegui, M. C., and T. P. Quinn. 2019a. Reliance on lakes by salmon, trout and charr (Oncorhynchus,
Salmo and Salvelinus): An evaluation of spawning habitats, rearing strategies and trophic
polymorphisms. Fish and Fisheries 20:775-794.
Arostegui, M. C., and T. P. Quinn. 2019b. Ontogenetic and ecotypic variation in the coloration and
morphology of rainbow trout (Oncorhynchus mykiss) in a stream-lake system. Biological Journal of
the Linnean Society 129:681-699.
Arostegui, M. C., T P. Quinn, L. W. Seeb, J. E. Seeb, and G. J. McKinney. 2019. Retention of chromosomal
inversion from an anadromous ancestor provides the genetic basis for alternative freshwater
ecotypes in rainbow trout. Molecular Ecology 28:1412-1427.
Atlas, W. I., N. C. Ban, J. W. Moore, A. M. Tuohy, S. Greening, A. J. Reid, N. Morven, E. White, W. G. Housty, J.
A. Housty, C. N. Service, L. Greba, S. Harrison, C. Sharpe, K. I. R. Butts, W. M. Shepert, E. Sweeney-
Bergen, D. Macintyre, M. R. Sloat, and K. Connors. 2021. Indigenous systems of management for
culturally and ecologically resilient Pacific salmon (Oncorhynchus spp.) fisheries. Bioscience 71:186-
204.
Augerot, X. 2005. Atlas of Pacific Salmon: The First Map-Based Status Assessment of Salmon in the North
Pacific. Portland, OR: University of California Press.
Barclay, A. W., and C. Habicht. 2019. Genetic Baseline for Cook Inlet Coho Salmon and Evaluations for
Mixed Stock Analysis. Fishery Data Series No. 19-19. Anchorage, AK: Alaska Department of Fish and
Game, Divisions of Sport Fish and Commercial Fisheries.
Beacham, T. D., and C. B. Murray. 1990. Temperature, egg size, and development of embryos and alevins
of 5 species of Pacific salmon - a comparative analysis. Transactions of the American Fisheries Society
119:927-945.
Recommended Determination
8-3
December 2022
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Section 8
References
Beechie, T. J., E. Beamer, and L. Wasserman. 1994. Estimating coho salmon rearing habitat and smolt
production losses in a large river basin, and implications for habitat restoration. North American
Journal of Fisheries Management 14:797-811.
Beechie, T., H. Moir, and G. Pess. 2008. Hierarchical physical controls on salmonid spawning location and
timing. American Fisheries Society Symposium 65:83-101.
Berkes, F., J. Colding, and C. Folke. 2000. Rediscovery of traditional ecological knowledge as adaptive
management. Ecological Applications 10:1251-1262.
Bersamin, A., B. Luick, E. Ruppert, J. Stern, and S. Zidenberg-Cherr. 2006. Diet quality among Yup'ik
Eskimos living in rural communities is low: the center for Alaska native health research pilot study.
Journal of the American Dietetic Association 106:1055-1063.
Bersamin, A., S. Zidenberg-Cherr, J. S. Stern, and B. R. Luick. 2007. Nutrient intakes are associated with
adherence to a traditional diet among Yup'ik Eskimos living in remote Alaska Native communities:
The Canhr study. International Journal of Circumpolar Health 66:62-70.
Bett, N. N., and S. G. Hinch. 2016. Olfactory navigation during spawning migrations: a review and
introduction of the Hierarchical Navigation Hypothesis. Biological Reviews 91:728-759.
Bilby, R. E., B. R. Fransen, and P. A. Bisson. 1996. Incorporation of nitrogen and carbon from spawning
coho salmon into the trophic system of small streams: Evidence from stable isotopes. Canadian
Journal of Fisheries and Aquatic Sciences 53:164-173.
Bilby, R. E., B. R. Fransen, P. A. Bisson, and J. K. Walter. 1998. Response of juvenile coho salmon
(iOncorhynchus kisutch) and steelhead [Oncorhynchus mykiss) to the addition of salmon carcasses to
two streams in southwestern Washington, USA. Canadian Journal of Fisheries and Aquatic Sciences
55:1909-1918.
Bjornn, T. C., and D. W. Reiser. 1991. Habitat requirements of salmonids in streams. Pages 83-138 in W.
R. Meehan (ed.), Influences of Forest and Rangeland Management on Salmonid Fishes and their
Habitats. Bethesda, MD: American Fisheries Society.
Blair, G. R., D. E. Rogers, and T. P. Quinn. 1993. Variation in life history characteristics and morphology of
sockeye salmon in the Kvichak River system, Bristol Bay, Alaska. Transactions of the American
Fisheries Society 122:550-559.
Boraas, A. S., and C. H. Knott. 2013. Traditional ecological knowledge and characterization of the
Indigenous cultures of the Nushagak and Kvichak watersheds, Alaska. Appendix D in An Assessment
of Potential Mining Impacts on Salmon Ecosystems of Bristol Bay, Alaska. Final Report. EPA 910-R-14-
001. Washington, DC.
Bradford, M. J., J. A. Grout, and S. Moodie. 2001. Ecology of juvenile chinook salmon in a small non-natal
stream of the Yukon River drainage and the role of ice conditions on their distribution and survival.
Canadian Journal of Zoology 79:2043-2054.
Recommended Determination
8-4
December 2022
-------
Section 8
References
Brannon, E. 1987. Mechanisms stabilizing salmonid fry emergence timing. Canadian Special Publication
of Fisheries and Aquatic Sciences 96:120-124.
Brazil, C. E., and F. W. West. 2016. Abundance, Age, Sex, and Size Statistics for Pacific Salmon in Bristol
Bay, 2006-2008. Fishery Data Series No. 16-51. Anchorage, AK: Alaska Department of Fish and Game,
Divisions of Sport Fish and Commercial Fisheries.
Brekken, J. M., K. J. Harper, J. M. Alas, and R. C. Benkert. 2022. Aquatic Biomonitoring at the Pebble
Prospect, 2010-2013. Technical Report No. 22-09. Anchorage, AK: Alaska Department of Fish and
Game, Habitat Section.
Brennan, S. R., D. E. Schindler, T. J. Cline, T. E. Walsworth, G. Buck, and D. P. Fernandez. 2019. Shifting
habitat mosaics and fish production across river basins. Science 364:783-786.
Bristol Bay Vision. 2011. Bristol Bay Regional Vision, Final Report. November. Available:
http://www.bristolbayvision.org/wp-content/uploads/BBRV-Final-Report-Nov-ll-WEB.pdf.
Brna, P. J., and L. A. Verbrugge (eds.). 2013. Wildlife Resources of the Nushagak and Kvichak River
Watersheds, Alaska (Final Report). Anchorage, AK: U.S. Fish and Wildlife Service, Anchorage Fish and
Wildlife Field Office.
Brown, R. S., W. A. Hubert, and S. F. Daly. 2011. A primer on winter, ice, and fish: What fisheries
biologists should know about winter ice processes and stream-dwelling fish. Fisheries 36:8-26.
Brown, T. G., and G. F. Hartman. 1988. Contribution of seasonally flooded lands and minor tributaries to
the production of coho salmon in Carnation Creek, British Columbia. Transactions of the American
Fisheries Society 117:546-551.
Bryant, M. D., and R. D. Woodsmith. 2009. The response of salmon populations to geomorphic
measurements at three scales. North American Journal of Fisheries Management 29:549-559.
Bryant, M. D., N. D. Zymonas, and B. E. Wright. 2004. Salmonids on the fringe: Abundance, species
composition, and habitat use of salmonids in high-gradient headwater streams, southeast Alaska.
Transactions of the American Fisheries Society 133:1529-1538.
Bue, B. G., S. M. Fried, S. Sharr, D. G. Sharp, J. A. Wilcock, and H. J. Geiger. 1998. Estimating salmon
escapement using area-under-the-curve, aerial observer efficiency, and stream-life estimates: the
Prince William Sound pink salmon example. North Pacific Anadromous Fish Commission Bulletin
1:240-250.
Buffington, J. M., D. R. Montgomery, and H. M. Greenberg. 2004. Basin-scale availability of salmonid
spawning gravel as influenced by channel type and hydraulic roughness in mountain catchments.
Canadian Journal of Fisheries and Aquatic Sciences 61:2085-2096.
Bunn, S. E., and A. H. Arthington. 2002. Basic principles and ecological consequences of altered flow
regimes for aquatic biodiversity. Environmental Management 30:492-507.
Recommended Determination
8-5
December 2022
-------
Section 8
References
Burger, C. V., and L. A. Gwartney. 1986. A Radio Tagging Study of Naknek Drainage Rainbow Trout.
Anchorage, AK: U.S. National Park Service, Alaska Regional Office.
Burger, C. V., W. J. Spearman, and M. A. Cronin. 1997. Genetic differentiation of sockeye salmon
subpopulations from a geologically young Alaskan lake system. Transactions of the American
Fisheries Society 126:926-938.
Burgner, R. L. 1991. Life history of sockeye salmon (Oncorhynchus nerka). Pages 1-118 in C. Groot and L.
Margolis (eds.), Pacific Salmon Life Histories. Vancouver, BC: UBC Press.
Burnett, K. M., G. H. Reeves, D. J. Miller, S. Clarke, K. Vance-Borland, and K. Christiansen. 2007.
Distribution of salmon-habitat potential relative to landscape characteristics and implications for
conservation. Ecological Applications 17:66-80.
Callahan, M. K., M. C. Rains, J. C. Bellino, C. M. Walker, S. J. Baird, D. F. Whigham, and R. S. King. 2015.
Controls on temperature in salmonid-bearing headwater streams in two common hydrogeologic
settings, Kenai Peninsula, Alaska. Journal of the American Water Resources Association 51:84-98.
Campbell, E. Y., J. B. Dunham, and G. H. Reeves. 2020. Linkages between temperature,
macroinvertebrates, and young-of-year Coho Salmon growth in surface-water and groundwater
streams. Freshwater Science 39:447-460.
CEAA (Canadian Environmental Assessment Agency). 2010. Report of the Federal Review Panel
Established by the Minister of the Environment: Taseko Mines Limited's Prosperity Gold-Copper Mine
Project. Available: http://publications.gc.ca/site/eng/371768/publication.html. Accessed: May 4,
2011.
Cederholm, C. J., M. D. Kunze, T. Murota, and A. Sibatani. 1999. Pacific salmon carcasses: Essential
contributions of nutrients and energy for aquatic and terrestrial ecosystems. Fisheries 24:6-15.
Chadwick, M. A., and A. D. Huryn. 2007. Role of habitat in determining macroinvertebrate production in
an intermittent-stream system. Freshwater Biology 52:240-251.
Chan, H. M., K. Fediuk, S. Hamilton, L. Rostas, A. Caughey, H. Kuhnlein, G. Egeland, and E. Loring. 2006.
Food security in Nunavut, Canada: Barriers and recommendations. International Journal of
CircumpolarHealth 65:416-431.
Chara-Serna, A. M., and J. S. Richardson. 2021. Multiple-stressor interactions in tributaries alter
downstream ecosystems in stream mesocosm networks. Water 13:1194.
Chin, A. T., M. H. Bond, and T. P Quinn. 2022. Life history differences between 2 anadromous populations
of the northern form of the Dolly Varden (Salvelinus malma malma) in Bristol Bay in southwestern
Alaska. Fishery Bulletin 120:234-239.
Choggiung, Ltd. 2014. Nushagak River Land Use Program Website. Available: http://choggiung.com/land-
dept/nushagak-river-land-use-program/. Accessed: June 29, 2014
Recommended Determination
8-6
December 2022
-------
Section 8
References
Claeson, S. M., J. L. Li, J. E. Compton, and P. A. Bisson. 2006. Response of nutrients, biofilm, and benthic
insects to salmon carcass addition. Canadian Journal of Fisheries and Aquatic Sciences 63:1230-1241.
Clark, S. C., T. L. Tanner, S. A. Sethi, K. T. Bentley, and D. E. Schindler. 2015. Migration timing of adult
Chinook Salmon into the Togiak River, Alaska, watershed: Is there evidence for stock structure?
Transactions of the American Fisheries Society 144:829-836.
Collen, P., and R. J. Gibson. 2001. The general ecology of beavers (Castor spp.), as related to their
influence on stream ecosystems and riparian habitats, and the subsequent effects on fish - a review.
Reviews in Fish Biology and Fisheries 10:439-461.
Colvin, S. A. R., S. M. P. Sullivan, P. D. Shirey, R. W. Colvin, K. 0. Winemiller, R. M. Hughes, K. D. Fausch, D.
M. Infante, J. D. Olden, K. R. Bestgen, R. J. Danehy, and L. Eby. 2019. Headwater streams and wetlands
are critical for sustaining fish, fisheries, and ecosystem services. Fisheries 44:73-91.
Crane, P., M. Lisac, B. Spearman, E. Kretschmer, C. Lewis, S. Miller, and J. Wenburg. 2003. Development
and Application of Microsatellites to Population Structure and Mixed-Stock Analyses of Dolly Varden
from the Togiak River Drainage, Final Report. Anchorage, AK: U.S. Fish and Wildlife Service,
Conservation Genetics Laboratory.
Cummins, K. W., and M. A. Wilzbach. 2005. The inadequacy of the fish-bearing criterion for stream
management. Aquatic Sciences 67:486-491.
Cunjak, R. A. 1996. Winter habitat of selected stream fishes and potential impacts from land-use activity.
Canadian Journal of Fisheries and Aquatic Sciences 53:267-282.
Curran, J., M. L. McTeague, S. E. Burril, and C. E. Zimmerman. 2011. Distribution, persistence, and
hydrologic characteristics of salmon spawning habitats in clearwater side channels of the Matanuska
River, southcentral Alaska. Scientific Investigations Report 2011-5102. Reston, VA: U.S. Geological
Survey.
Dann, T. H., C. Habicht, J. R. Jasper, H. A. Hoyt, A. W. Barclay, W. D. Templin, T. T. Baker, F. W. West, and L.
F. Fair. 2009. Genetic Stock Composition for the Commercial Harvest ofSockeye Salmon in Bristol Bay,
Alaska, 2006-2008. Fishery Manuscript Series 09-06. Anchorage, AK: Alaska Department of Fish and
Game, Divisions of Sport Fish and Commercial Fisheries.
Dann, T. H., C. Habicht, J. R. Jasper, E. K. C. Fox, H. A. Hoyt, H. L. Liller, E. S. Lardizabal, P. A. Kuriscak, Z. D.
Grauvogel, and W. D. Templin. 2012. Sockeye Salmon Baseline for the Western Alaska Salmon Stock
Identification Project. Special Publication No. 12-12. Anchorage, AK: Alaska Department of Fish and
Game, Divisions of Sport Fish and Commercial Fisheries.
Dann, T. H., C. Habicht, T. T. Baker, and J. E. Seeb. 2013. Exploiting genetic diversity to balance
conservation and harvest of migratory salmon. Canadian Journal of Fisheries and Aquatic Sciences
70:785-793.
Recommended Determination
8-7
December 2022
-------
Section 8
References
Dann, T. H., G. Buck, and B. Jones. 2018. Stock composition of subsistence harvests and total return of
sockeye salmon from the Kvichak River. ADF&G Alaska Sustainable Salmon Grant Proposal
Presentation, 148th Annual Meeting of the American Fisheries Society.
Darimont, C. T., T. E. Reimchen, and P. C. Paquet. 2003. Foraging behaviour by gray wolves on salmon
streams in coastal British Columbia. Canadian Journal of Zoology 81:349-353.
Daum, D. W., and B. G. Flannery. 2011. Canadian-origin Chinook salmon rearing in nonnatal U.S.
tributary streams of the Yukon River, Alaska. Transactions of the American Fisheries Society
140:207-220.
Davis, B. M., and D. E. Schindler. 2021. Effects of variability and synchrony in assessing contributions of
individual streams to habitat portfolios of river basins. Ecological Indicators 124: 107427.
Davis, C., J. Garza, and M. Banks. 2017. Identification of multiple genetically distinct populations of
Chinook salmon (Oncorhynchus tshawytscha) in a small coastal watershed. Environmental Biology of
Fishes 100:923-933.
DeCicco, A. L. 1992. Long-distance movements of anadromous Dolly Varden between Alaska and the
USSR. Arctic 45:120-123.
DeCicco, A. L. 1997. Movements of postsmolt anadromous Dolly Varden in northwestern Alaska.
American Fisheries Symposium 19:175-183.
Dekar, M. P., R. S. King, J. A. Back, D. F. Whigham, and C. M. Walker. 2012. Allochthonous inputs from
grass-dominated wetlands support juvenile salmonids in headwater streams: evidence from stable
isotopes of carbon, hydrogen, and nitrogen. Freshwater Science 31:121-132.
Demory, R. L., R. F. Orrell, and D. R. Heinle. 1964. Spawning Ground Catalog of the Kvichak River System,
Bristol Bay, Alaska. Special Scientific Report - Fisheries No. 488. Washington, DC: U.S. Fish and
Wildlife Service.
Denton, K. P., H. B. Rich, and T. P. Quinn. 2009. Diet, movement, and growth of Dolly Varden in response
to sockeye salmon subsidies. Transactions of the American Fisheries Society 138:1207-1219.
Denton, K. P., H. B. Rich Jr., J. W. Moore, and T. P. Quinn. 2010. The utilization of a Pacific salmon
Oncorhynchus nerka subsidy by three populations of charr Salvelinus spp. Journal of Fish Biology
77:1006-1023.
Detterman, R. L., and B. L. Reed. 1973. Surficial Deposits of the Iliamna Quadrangle, Alaska. Geological
Survey Bulletin 1368-A. Washington, DC: U.S. Geological Survey. Available:
https://dggs.alaska.gOv/webpubs/usgs/b/text/bl368a.pdf.Accessed: May 16, 2022.
Dewailly, E., C. Blanchet, S. Gingras, S. Lemieux, and B. J. Holub. 2002. Cardiovascular disease risk factors
and n-3 fatty acid status in the adult population of James Bay Cree. American Journal of Clinical
Nutrition 76:85-92.
Recommended Determination
8-8
December 2022
-------
Section 8
References
Dewailly, E., C. Blanchet, S. Lemieux, L. Sauve, S. Gingras, P. Ayotte, and B. J. Holub. 2001. n-3 Fatty acids
and cardiovascular disease risk factors among the Inuit of Nunavik. American Journal of Clinical
Nutrition 74:464-473.
Din, J. N., D. E. Newby, and A. D. Flapan. 2004. Science, medicine, and the future - Omega 3 fatty acids and
cardiovascular disease - fishing for a natural treatment. British Medical Journal 328:30-35.
Dittman, A. H., and T. P. Quinn. 1996. Homing in Pacific salmon: Mechanisms and ecological basis. Journal
of Experimental Biology 199:83-91.
Donofrio, E., T. Simon, J. R. Neuswanger, and G. D. Grossman. 2018. Velocity and dominance affect prey
capture and microhabitat selection in juvenile Chinook (Oncorhynchus tshawytscha). Environmental
Biology of Fishes 101:609-622.
Doretto, A., E. Piano, and C. E. Larson. 2020. The River Continuum Concept: lessons from the past and
perspectives for the future. Canadian Journal of Fisheries and Aquatic Sciences 77:1853-1864.
Duffield, J., D. Patterson, and C. Neher. 2007. Economics of Wild Salmon Watersheds: Bristol Bay, Alaska
(Revised Final Report). Missoula, MT.
Dye, J. E., and L. K. Borden. 2018. Sport Fisheries in the Bristol Bay Management Area, 2016-2018. Fishery
Management Report No. 18-27. Anchorage, AK: Alaska Department of Fish and Game, Divisions of
Sport Fish and Commercial Fisheries.
Dye, J. E., and C. J. Schwanke. 2009. Report to the Alaska Board of Fisheries for the Recreational Fisheries of
Bristol Bay, 2007,2008, and 2009. Special Publication No. 09-14. Anchorage, AK: Alaska Department
of Fish and Game, Division of Sport Fish, Research and Technical Services.
Dye, J. E., C. J. Schwanke, and T. A. Jaecks. 2006. Report to the Alaska Board of Fisheries for the
Recreational Fisheries of Bristol Bay, 2004,2005, and 2006. Special Publication No. 06-29. Anchorage,
AK: Alaska Department of Fish and Game, Divisions of Sport Fish and Commercial Fisheries.
Ebbesson, S. 0. E., M. E. Tejero, E. D. Nobmann, J. C. Lopez-Alvarenga, L. Ebbesson, T. Romenesko, E. A.
Carter, H. E. Resnick, R. B. Devereux, J. W. MacCluer, B. Dyke, S. L. Laston, C. R. Wenger, R. R. Fabsitz,
A. G. Comuzzie, and B. V. Howard. 2007. Fatty acid consumption and metabolic syndrome
components: the GOCADAN study. The Journal of Cardiometabolic Syndrome 2:244-249.
Ebersole, J. L., R. M. Quinones, S. Clements, and B. H. Letcher. 2020. Managing climate refugia for
freshwater fishes under an expanding human footprint. Frontiers in Ecology and the Environment
18:271-280.
Ebersole, J. L., P. J. Wigington, S. G. Leibowitz, R. L. Comeleo, and J. Van Sickle. 2015. Predicting the
occurrence of cold-water patches at intermittent and ephemeral tributary confluences with warm
rivers. Freshwater Science 34:111-124.
Recommended Determination
8-9
December 2022
-------
Section 8
References
Eliason, E. J., T. D. Clark, M. J. Hague, L. M. Hanson, Z. S. Gallagher, K. M. Jeffries, M. K. Gale, D. A. Patterson,
S. G. Hinch, and A. P. Farrell. 2011. Differences in thermal tolerance among sockeye salmon
populations. Science 332:109-112.
Eng, K., T. E. Grantham, D. M. Carlisle, and D. M. Wolock. 2017. Predictability and selection of hydrologic
metrics in riverine ecohydrology. Freshwater Science 36:915-926.
English, E., Tourangeau, R., and Horsch, E. 2019. Lost use-value from environmental injury when
visitation drops at undamaged sites: Comment. Land Economics 95:146-151.
EPA (U.S. Environmental Protection Agency). 2012. EPA Region 10 Tribal Consultation and Coordination
Procedures. EPA 910-K-12-002. Seattle, WA.
EPA. 2014. An Assessment of Potential Mining Impacts on Salmon Ecosystems of Bristol Bay, Alaska. Final
Report. EPA 910-R-14-001. Washington, DC.
EPA. 2015. Connectivity of Streams and Wetlands to Downstream Waters: A Review and Synthesis of the
Scientific Evidence (Final Report). EPA/600/R-14/475F. Washington, DC: Office of Research and
Development.
EPA. 2018. Summary of Tribal Consultation for the Proposal to Withdraw the Proposed Determination to
Restrict Use of Area as Disposal Site: Pebble Deposit Area, Southwest Alaska. Docket EPA-R10-OW-
2017-0369-12483. Seattle, WA.
EPA. 2019. EPA Comments on Public Notice POA-2017-00271 (Letter from Chris Hladick, EPA Region 10
Regional Administrator, to Col. Phillip Borders, Alaska District Engineer, U.S. Army Corps of Engineers).
July 1.
EPA. 2021. Environmental Protection Agency's Guiding Principles for Consulting with Alaska Native Claims
Settlement Act Corporations.
EPA. 2022. Consideration of Potential Costs Regarding the Clean Water Act Section 404(c) Recommended
Determination for the Pebble Deposit Area, Southwest Alaska [Draft]. Seattle, WA: U.S. Environmental
Protection Agency, Region 10. Available: http://www.regulations.gov, Docket EPA-R10-OW-2022-
0418.
EPA and DOA (Department of the Army). 1992. Clean Water Act Section 404(b)(1) Guidelines(q)
Memorandum of Agreement between the Environmental Protection Agency and the Department of the
Army. Available: https://www.epa.gov/cwa-404/cwa-section-404q-memorandum-agreement-
between-epa-and-department-army-text. Accessed: May 10, 2022.
Evans, S., M. Kukkonen, D. L. Holen, and D. S. Koster. 2013. Harvests of Uses of Wild Resources in
Dillingham, Alaska, 2010. Technical Paper No. 375. Anchorage, AK: Alaska Department of Fish and
Game, Division of Subsistence.
Recommended Determination
8-10
December 2022
-------
Section 8
References
Evenson, D. F., C. Habicht, M. Stopha, A. R. Munro, T. R. Meyers, and W. D. Templin. 2018. Salmon
Hatcheries in Alaska - A Review of the Implementation of Plans, Permits, and Policies Designed to
Provide Protection for Wild Stocks. Special Publication No. 18-12. Anchorage, AK: Alaska Department
of Fish and Game, Divisions of Sport Fish and Commercial Fisheries.
Fair, L. F., C. E. Brazil, X. Zhang, R. A. Clark, and J. W. Erickson. 2012. Review of Salmon Escapement Goals
in Bristol Bay, Alaska, 2012. Fishery Manuscript Series No. 12-0. Anchorage, AK: Alaska Department
of Fish and Game.
Fall, J. A., D. L. Holen, B. Davis, T. Krieg, and D. Koster. 2006. Subsistence Harvests and Uses of Wild
Resources in Iliamna, Newhalen, Nondalton, Pedro Bay, and Port Alsworth, Alaska 2004. Technical
Paper No. 302. Juneau, AK: Alaska Department of Fish and Game, Division of Subsistence.
Fall, J. A., T. M. Krieg, and D. Holen. 2009. Overview of the Subsistence Fishery of the Bristol Bay
Management Area. Special Publication No. BOF 2009-07. Anchorage, AK: Alaska Department of Fish
and Game, Division of Subsistence.
Fausch, K. D., C. E. Torgersen, C. V. Baxter, and H. W. Li. 2002. Landscapes to riverscapes: Bridging the
gap between research and conservation of stream fishes. Bioscience 52:483-498.
Figge, F. 2004. Bio-folio: applying portfolio theory to biodiversity. Biodiversity and Conservation 13:827-
849.
Finn, R. J. R., L. Chalifour, S. E. Gergel, S. G. Hinch, D. C. Scott, and T. G. Martin. 2021. Quantifying lost and
inaccessible habitat for Pacific salmon in Canada's Lower Fraser River. Ecosphere 12:e03646.
Fischenich, J. C. 2006. Functional Objectives for Stream Restoration. U.S. Army Corps of Engineers,
Ecosystem Management and Restoration Research Program, ERDC TN-EMRRP SR-52.
Flitcroft, R. L., S. L. Lewis, I. Arismendi, R. LovellFord, M. V. Santelmann, M. Safeeq, and G. Grant. 2016.
Linking hydroclimate to fish phenology and habitat use with ichthyographs. PLoS ONE ll:e0168831.
Flitcroft, R. L., I. Arismendi, and M. V. Santelmann. 2019. A review of habitat connectivity research for
Pacific salmon in marine, estuary, and freshwater environments. Journal of the American Water
Resources Association 55:430-441.
Foley, K. M., A. Rosenberger, and F. J. Mueter. 2018. Longitudinal patterns of juvenile coho salmon
distribution and densities in headwater streams of the Little Susitna River, Alaska. Transactions of
the American Fisheries Society 147:247-264.
Freeman, M. C., C. M. Pringle, and C. R. Jackson. 2007. Hydrologic connectivity and the contribution of
stream headwaters to ecological integrity at regional scales. Journal of the American Water Resources
Association 43:5-14.
Recommended Determination
8-11
December 2022
-------
Section 8
References
French, D. W., D. E. Schindler, S. R. Brennan, and D. Whited. 2020. Headwater catchments govern
biogeochemistry in America's largest free-flowing river network. Journal of Geophysical Research-
Biogeosciences 125.
Fritz, K. M., K. A. Schofield, L. C. Alexander, M. G. McManus, H. E. Golden, C. R. Lane, W. G. Kepner, S. D.
LeDuc, J. E. DeMeester, and A. I. Pollard. 2018. Physical and chemical connectivity of streams and
riparian wetlands to downstream waters: a synthesis. Journal of the American Water Resources
Association 54:323-345.
Gardiner, W. R., and P. Geddes. 1980. The influence of body composition on the survival of juvenile
salmon. Hydrobiologia 69:67-72.
Gende, S. M., R. T. Edwards, M. F. Willson, and M. S. Wipfli. 2002. Pacific salmon in aquatic and terrestrial
ecosystems. Bioscience 52:917-928.
Ghaffari, H., R. S. Morrison, M. A., deRuijeter, A. Zivkovic, T. Hantelmann, D. Ramsey, and S. Cowie. 2011.
Preliminary Assessment of the Pebble Project, Southwest Alaska. Document 1056140100-REP-R0001-
00. February 15. Prepared for NDML by WARDROP (a Tetra Tech Company), Vancouver, BC.
Giannico, G. R., and S. G. Hinch. 2007. Juvenile coho salmon (Oncorhynchus kisutch) responses to salmon
carcasses and in-stream wood manipulations during winter and spring. Canadian Journal of Fisheries
and Aquatic Sciences 64:324-335.
Gibbins, C., J. Shellberg, H. Moir, and C. Soulsby. 2008. Hydrological influences on adult salmonid
migration, spawning, and embryo survival. American Fisheries Symposium 65:195-223.
Giefer, J., and B. Blossom. 2021. Catalog of Waters Important for Spawning, Rearing, or Migration of
Anadromous Fishes—Southwestern Region, Effective June 1, 2021. Special Publication No. 21-05.
Anchorage, AK: Alaska Department of Fish and Game. Available:
https://www.adfg.alaska.gov/sf/SARR/AWC/index.cfm?ADFG=main.home. Accessed: January 20,
2022.
Giefer, J., and S. Graziano. 2022. Catalog of Waters Important for Spawning, Rearing, or Migration of
Anadromous Fishes—Southwestern Region, Effective June 15, 2022. Special Publication No. 22-05.
Anchorage, AK: Alaska Department of Fish and Game. Available:
https://www.adfg.alaska.gov/sf/SARR/AWC/index.cfm?ADFG=main.home. Accessed: September
29,2022.
Glasgow, G., and Train, K. 2018. Lost use-value from environmental injury when visitation drops at
undamaged sites. Land Economics 94:87-96.
Glasgow, G., and Train, K. 2019. Lost use-value from environmental injury when visitation drops at
undamaged sites: Reply. Land Economics 95:152-156.
Recommended Determination
8-12
December 2022
-------
Section 8
References
Goldsmith, 0. S., A. Hill, T. Hull, M. Markowski, and R. Unswort. 1998. Economic Assessment of Bristol Bay
Area National Wildlife Refuges: Alaska Peninsula, Becherof Izembek, Togiak. Anchorage, AK: U.S. Fish
and Wildlife Service, Division of Economics.
Gomez-Uchida, D., J. E. Seeb, M. J. Smith, C. Habicht, T. P. Quinn, and L.W. Seeb. 2011. Single nucleotide
polymorphisms unravel hierarchical divergence and signatures of selection among Alaskan sockeye
salmon (Oncorhynchus nerka) populations. BMC Evolutionary Biology 11:1-17.
Gonzalez, J. M., and A. Elosegi. 2021. Water abstraction reduces taxonomic and functional diversity of
stream invertebrate assemblages. Freshwater Science 40:524-536.
Gresh, T., J. Lichatowich, and P. Schoonmaker. 2000. An estimation of historic and current levels of
salmon production in the Northeast Pacific ecosystem: Evidence of a nutrient deficit in the
freshwater systems of the Pacific Northwest. Fisheries 25:15-21.
Griffiths, J. R., D. E. Schindler, J. B. Armstrong, M. D. Scheuerell, D. C. Whited, R. A. Clark, R. Hilborn, C. A.
Holt, S. T. Lindley, J. A. Stanford, and E. C. Volk. 2014. Performance of salmon fishery portfolios
across western North America. Journal of Applied Ecology 51:1554-1563.
Grill, G., B. Lehner, M. Thieme, B. Gennen, D. Tickner, F. Antonelli, S. Babu, P. Borrelli, L. Cheng, H.
Crochetiere, H. Ehalt Macedo, R. Filgueiras, M. Goichot, J. Higgins, Z. Hogan, B. Lip, M. E. McClain, J.
Meng, M. Mulligan, C. Nilsson, J. D. Olden, J. J. Opperman, P. Petry, C. Reidy Liermann, L. Saenz, S.
Salinas-Rodriguez, P. Schelle, R. J. P. Schmitt, J. Snider, F. Tan, K. Tockner, P. H. Valdujo, A. van
Soesbergen, and C. Zarfl. 2019. Mapping the world's free-flowing rivers. Nature 569:215-221.
Gustafson, R. G., R. S. Waples, J. M. Myers, L. A. Weitkamp, G. J. Bryant, 0. W. Johnson, and J. J. Hard. 2007.
Pacific salmon extinctions: Quantifying lost and remaining diversity. Conservation Biology 21:1009-
1020.
Halas, G., and G. Neufeld. 2018. An Overview of the Subsistence Fisheries of the Bristol Bay Management
Area, Alaska. Special Publication No. BOF 2018-04. Anchorage, AK: Alaska Department of Fish and
Game, Division of Subsistence.
Hale, R., M. A. Colton, P. Peng, and S. E. Swearer. 2019. Do spatial scale and life history affect fish-habitat
relationships? Journal of Animal Ecology 88:439-449.
Hall, L. D., B. Stillwater, G. Stolz, and C. J. Utermohle. 2005. The Prevalence of Diabetes Among Adult
Alaskans, 2002-2004. Epidemiology Bulletins 1-8. Anchorage, AK: Alaska Department of Health and
Social Services, Division of Public Health.
Hancock, P. J. 2002. Human impacts on the stream-groundwater exchange zone. Environmental
Management 29:763-781.
Recommended Determination
8-13
December 2022
-------
Section 8
References
Hart, L. M., M. H. Bond, S. L. May-McNally, J. A. Miller, and T. P. Quinn. 2015. Use of otolith
microchemistry and stable isotopes to investigate the ecology and anadromous migrations of
Northern Dolly Varden from the Egegik River, Bristol Bay, Alaska. Environmental Biology of Fishes
98:1633-1643.
Hartman, W. L., and R. L. Burgner. 1972. Limnology and fish ecology of sockeye salmon nursery lakes of
the world. Journal of the Fisheries Research Board of Canada 29:699-715.
Hazell, S. M., C. Welch, J. T. Ream, S. S. Evans, T. M. Krieg, H. Z. Johnson, G. Zimpelman, and C. Carty. 2015.
Whitefish and Other Nonsalmon Fish Trends in Lake Clark and Iliamna Lake, Alaska, 2012 and 2013.
Technical Paper No. 411. Anchorage, AK: Alaska Department of Fish and Game, Division of
Subsistence.
Healey, M. C. 1991. Life history of Chinook salmon (Oncorhynchus tshawytscha). Pages 311-393 in C.
Groot and L. Margolis (eds.), Pacific Salmon Life Histories. Vancouver, BC: UBC Press.
Heard, W. R. 1991. Life history of pink salmon (Oncorhynchus gorbuscha). Pages 119-230 in C. Groot and
L. Margolis (eds.), Pacific Salmon Life Histories. Vancouver, BC: UBC Press.
Hedden, S. C., and K. B. Gido. 2020. Dispersal drives changes in fish community abundance in
intermittent stream networks. River Research and Applications 36:797-806.
Heintz, R. A., B. D. Nelson, J. Hudson, M. Larsen, L. Holland, and M. Wipfli. 2004. Marine subsidies in
freshwater: Effects of salmon carcasses on lipid class and fatty acid composition of juvenile coho
salmon. Transactions of the American Fisheries Society 133:559-567.
Helfield, J. M., and R. J. Naiman. 2006. Keystone interactions: Salmon and bear in riparian forests of
Alaska. Ecosystems 9:167-180.
Hendry, A. P., J. E. Hensleigh, and R. R. Reisenbichler. 1998. Incubation temperature, developmental
biology, and the divergence of sockeye salmon (Oncorhynchus nerka) within Lake Washington.
Canadian Journal of Fisheries and Aquatic Sciences 55:1387-1394.
Hendry, A. P., J. K. Wenburg, P. Bentzen, E. C. Volk, and T. P. Quinn. 2000. Rapid evolution of reproductive
isolation in the wild: Evidence from introduced salmon. Science 290:516-518.
Henning, J. A., R. E. Gresswell, and I. A. Fleming. 2006. Juvenile salmonid use of freshwater emergent
wetlands in the floodplain and its implications for conservation management. North American
Journal of Fisheries Management 26:367-376.
Hilborn, R., T. P. Quinn, D. E. Schindler, and D. E. Rogers. 2003. Biocomplexity and fisheries sustainability.
Proceedings of the National Academy of Sciences of the United States of America 100:6564-6568.
Hill, B. H., R. K. Kolka, F. H. McCormick, and M. A. Starry. 2014. A synoptic survey of ecosystem services
from headwater catchments in the United States. Ecosystem Services 7:106-115.
Recommended Determination
8-14
December 2022
-------
Section 8
References
Hodgson, S., and T. P. Quinn. 2002. The timing of adult sockeye salmon migration into fresh water:
adaptations by populations to prevailing thermal regimes. Canadian Journal of Zoology 80:542-555.
Holen, D., and T. Lemons. 2010. Subsistence Harvests and Uses of Wild Resources in Lime Village, Alaska,
2007. Technical Paper No. 355. Anchorage, AK: Alaska Department of Fish and Game, Division of
Subsistence.
Holen, D., T. M. Krieg, and T. Lemons. 2011. Subsistence Harvests and Uses of Wild Resources in King
Salmon, Naknek, and South Naknek, Alaska, 2007. Technical Paper No. 360. Anchorage, AK: Alaska
Department of Fish and Game, Division of Subsistence.
Holen, D., J. Stariwat, T. M. Krieg, and T. Lemons. 2012. Subsistence Harvest and Uses of Wild Resources in
Aleknagik, Clark's Point, and Manokotak, Alaska, 2008. Technical Paper No. 368. Anchorage, AK:
Alaska Department of Fish and Game, Division of Subsistence.
Huntsman, B. M., and J. A. Falke. 2019. Main stem and off-channel habitat use by juvenile Chinook salmon
in a sub-Arctic riverscape. Freshwater Biology 64:433-446.
Huusko, A., L. Greenberg, M. Stickler, T. Linnansaari, M. Nykanen, T. Vehanen, S. Koljonen, P. Louhi, and
K. Alfredsen. 2007. Life in the ice lane: The winter ecology of stream salmonids. River Research and
Applications 23:469-491.
Irons J. G., Ill, S. R. Ray, L. K. Miller, and M. W. Oswood. 1989. Spatial and seasonal patterns of streambed
water temperatures in an Alaskan subarctic stream. Pages 381-390 in Proceedings of the Symposium
on Headwaters Hydrology. Bethesda, MD: American Water Resources Association.
Irvine, J. R., A. Tompkins, T. Saito, K. B. Seong, J. K. Kim, N. Klovach, H. Bartlett, and E. Volk. 2012. Pacific
Salmon Status and Abundance Trends - 2012 Update. NPAFC Doc. 1422. Rev. 2. North Pacific
Anadromous Fish Commission.
Jackson, H. B., and L. Fahrig. 2015. Are ecologists conducting research at the optimal scale? Global
Ecology and Biogeography 24:52-63.
Jaecks, T., and T. P. Quinn. 2014. Ontogenetic shift to dependence on salmon-derived nutrients in Dolly
Varden char from the Iliamna River, Alaska. Environmental Biology of Fishes 97:1323-1333.
Janetski, D. J., D. T. Chaloner, S. D. Tiegs, and G. A. Lamberti. 2009. Pacific salmon effects on stream
ecosystems: a quantitative synthesis. Oecologia 159:583-595.
Jensen, A. J., and B. 0. Johnsen. 1999. The functional relationship between peak spring floods and
survival and growth of juvenile Atlantic Salmon (Salmo salar) and Brown Trout (Salmo trutta).
Functional Ecology 13:778-785.
Johnson, J. S., E. D. Nobmann, E. Asay, and A. P. Lanier. 2009. Dietary intake of Alaska Native people in
two regions and implications for health: the Alaska Native Dietary and Subsistence Food Assessment
Project. International Journal of Circumpolar Health 68:109-122.
Recommended Determination
8-15
December 2022
-------
Section 8
References
Johnson, S. W., J. F. Thedinga, and A. S. Feldhausen. 1994. Juvenile salmonid densities and habitat use in
the main-stem Situk River, Alaska, and potential effects of glacial flooding. Northwest Science
68:284-293.
Jones, E. L., Ill, S. Heinl, and K. Pahlke. 2007. Aerial counts. Pages 399-410 in D. H. Johnson, B. M. Shrier, J.
S. O'Neal, J. A. Knutzen, X. Augerot, T. A. O'Neil, and T. N. Pearsons (eds.), Salmonid Field Protocols
Handbook: Techniques for Assessing Status and Trends in Salmon and Trout Populations. Bethesda,
MD: American Fisheries Society.
Joyce, A. 2008. Risk and Opportunity in British Columbia Shellfisheries: The Role of Limited Property Rights
in Aquaculture Development. PhD thesis. University of British Columbia, Vancouver, BC.
Kahler, T. H., P. Roni, and T. P. Quinn. 2001. Summer movement and growth of juvenile anadromous
salmonids in small Western Washington streams. Canadian Journal of Fisheries and Aquatic Sciences
58:1947-1956.
Kalanchey, R., H. Ghaffari, S. Abdel, L. Galbraith, J. D. Gaunt, E. Titley, S. Hodgson, and J. Lang. 2021. Pebble
Project Preliminary Economic Assessment. NI 43-101 Technical Report. Prepared for Northern
Dynasty Minerals Ltd.
Keefer, M. L. and C. C. Caudill. 2014. Homing and straying by anadromous salmonids: a review of
mechanisms and rates. Reviews in Fish Biology and Fisheries 24:333-368.
Kendall, N. W., J. J. Hard, and T. P. Quinn. 2009. Quantifying six decades of fishery selection for size and
age at maturity in sockeye salmon. Evolutionary Applications 2:523-536.
Kenner, P. C. 2003. From Neqa to Tepa: A Database with Traditional Knowledge about the Fish of Bristol
Bay and the Northern Alaska Peninsula. Compact Disk Version 2.0. Final Report No. FIS 01-109.
Anchorage, AK: U.S. Fish and Wildlife Service, Office of Subsistence Management, Fisheries Resource
Monitoring Program.
King, R. S., C. M. Walker, D. F. Whigham, S. J. Baird, and J. A. Back. 2012. Catchment topography and
wetland geomorphology drive macroinvertebrate community structure and juvenile salmonid
distributions in south-central Alaska headwater streams. Freshwater Science 31:341-364.
Kline, T. C., J. J. Goering, 0. A. Mathisen, P. H. Poe, P. L. Parker, and R. S. Scalan. 1993. Recycling of
elements transported upstream by runs of Pacific salmon. 2. Delta N-15 and delta C-13 evidence in
the Kvichak River watershed, Bristol Bay, southwestern Alaska. Canadian Journal of Fisheries and
Aquatic Sciences 50:2350-2365.
Knapp, G., M. Guettabi, and 0. S. Goldsmith. 2013. The Economic Importance of the Bristol Bay Salmon
Industry. Anchorage, AK: University of Alaska Anchorage, Institute of Social and Economic Research.
Knight Piesold. 2019a. Treated Water Flow Release Schedules. Prepared by Knight Piesold Ltd. for Pebble
Limited Partnership. VA101-176/60-A.01. October 10.
Recommended Determination
8-16
December 2022
-------
Section 8
References
Knight Piesold. 2019b. Pebble Project Water Balance and Water Quality Model Report. Prepared by
Knight Piesold Ltd. for Pebble Limited Partnership. VA101-176/60-3. December 18.
Knott, C. H. 1998. Living with the Adirondack Forest: Local Perspectives on Land Use Conflicts. Ithaca, NY:
Cornell University Press.
Koenig, L. E., A. M. Helton, P. Savoy, E. Bertuzzo, J. B. Heffernan, R. 0. Hall, and E. S. Bernhardt. 2019.
Emergent productivity regimes of river networks. Limnology and Oceanography Letters 4:173-181.
Krieg, T., M. Chythlook, P. Coiley-Kenner, D. Holen, K. Kamletz, and H. Nicholson. 2005. Freshwater Fish
Harvest and Use in Communities of the Kvichak watershed, 2003. Technical Data Report No. 297.
Juneau AK: Alaska Department of Fish and Game, Division of Subsistence.
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. Technical Paper No. 326. Juneau,
AK: Alaska Department of Fish and Game, Division of Subsistence.
Krieg, T. M., D. L. Holen, and D. Koster. 2009. Subsistence Harvests and Uses of Wild Resources in Igiugig,
Kokhanok, Koliganek, Levelock, and New Stuyahok, Alaska 2005. Technical Paper No. 322. Dillingham,
AK: Alaska Department of Fish and Game, Division of Subsistence.
Krueger, C. C., M. J. Lisac, S. J. Miller, and W. H. Spearman. 1999. Genetic Differentiation of Rainbow Trout
fOncorhynchus mykissj in the Togiak National Wildlife Refuge, Alaska. Alaska Fisheries Technical
Report No. 55. Anchorage, AK: U.S. Fish and Wildlife Service, Fish Genetics Laboratory.
Kuhnlein, H., 0. Receveur, and H. Chan. 2001. Traditional food systems research with Canadian
indigenous peoples. International Journal of Circumpolar Health 60:112-122.
Lang, D. W., G. H. Reeves, J. D. Hall, and M. S. Wipfli. 2006. The influence of fall-spawning coho salmon
(iOncorhynchus kisutch) on growth and production of juvenile coho salmon rearing in beaver ponds
on the Copper River Delta, Alaska. Canadian Journal of Fisheries and Aquatic Sciences 63:917-930.
Larkin, G. A., and P. A. Slaney. 1997. Implications of trends in marine-derived nutrient influx to south
coastal British Columbia salmonid production. Fisheries 22:16-24.
Larson, W. A., J. E. Seeb, T. H. Dann, D. E. Schindler, and L. W. Seeb. 2014. Signals of heterogeneous
selection at an MHC locus in geographically proximate ecotypes of sockeye salmon. Molecular
Ecology 23:5448-5461.
Larson, W. A., M. T. Limborg, G. J. McKinney, D. E. Schindler, J. E. Seeb, and L. W. Seeb. 2017. Genomic
islands of divergence linked to ecotypic variation in sockeye salmon. Molecular Ecology 26:554-570.
Larson, W. A., M. T. Limborg, G. J. McKinney, J. E. Seeb, L. W. Seeb, and T. H. Dann. 2019. Parallel
signatures of selection at genomic islands of divergence and the major histocompatibility complex in
ecotypes of sockeye salmon across Alaska. Molecular Ecology 28:2254-2271.
Recommended Determination
8-17
December 2022
-------
Section 8
References
Lessard, J. L., and R. W. Merritt. 2006. Influence of marine-derived nutrients from spawning salmon on
aquatic insect communities in southeast Alaskan streams. Oikos 113:334-343.
Levin, P. S., R. W. Zabel, and J. G. Williams. 2001. The road to extinction is paved with good intentions:
negative association of fish hatcheries with threatened salmon. Proceedings of the Royal Society B-
Biological Sciences 268:1153-1158.
Levy, S. 1997. Pacific salmon bring it all back home. Bioscience 47:657-660.
Lin, J., T. P. Quinn, R. Hilborn, and L. Hauser. 2008a. Fine-scale differentiation between sockeye salmon
ecotypes and the effect of phenotype on straying. Heredity 101:341-350.
Lin, J., E. Ziegler, T. P. Quinn, and L. Hauser. 2008b. Contrasting patterns of morphological and neutral
genetic divergence among geographically proximate populations of sockeye salmon Oncorhynchus
nerka in Lake Aleknagik, Alaska. Journal of Fish Biology 73:1993-2004.
Lindley, S. T., C. B. Grimes, M. S. Mohr, W. Peterson. J. Stein, J. T. Anderson, L. W. Botsford, D. L. Bottom, C.
A. Busack, T. K. Collier, J. Ferguson, J. C. Garza, A. M. Grover, D. G. Hankin, R. G. Kope, P. W. Lawson, A.
Low, R. B. MacFarlane, K. Moore, M. Palmer-Zwahlen, F. B. Schwing, J. Smith, C. Tracy, R. Webb, B. K.
Wells, and T. H. Williams. 2009. What Caused the Sacramento River Fall Chinook Stock Collapse?
NOAA-TM-NMFS-SWFSC-447. National Oceanic and Atmospheric Administration, National Marine
Fisheries Service, Southwest Fisheries Science Center.
Lisac, M. J. 2009. Seasonal Distribution and Biological Characteristics of Dolly Varden in the Goodnews
River, Togiak National Wildlife Refuge, Alaska, 2005-2006. Alaska Fisheries Technical Report No. 103.
Dillingham, AK: U.S. Fish and Wildlife Service, Togiak National Wildlife Refuge.
Lisac, M. J., and R. D. Nelle. 2000. Migratory Behavior and Seasonal Distribution of Dolly Varden Salvelinus
malma in the Togiak River Watershed, Togiak National Wildlife Refuge. Dillingham, AK: U.S. Fish and
Wildlife Service.
Lisi, P. J., D. E. Schindler, K. T. Bentley, and G. R. Pess. 2013. Association between geomorphic attributes
of watersheds, water temperature, and salmon spawn timing in Alaskan streams. Geomorphology
185:78-86.
Loring, P. A., L. K. Duffy, and M. S. Murray. 2010. A risk-benefit analysis of wild fish consumption for
various species in Alaska reveals shortcomings in data and monitoring needs. Science of the Total
Environment 408:4532-4541.
Lubetkin, S. 2022. Alaska Mining Spills: A comparison of the predicted impacts described in permitting
documents and spill records from five major operational hardrock mines. Report prepared for Brooks
Range Council, Earthworks, National Parks Conservation Association, Norton Bay Intertribal
Watershed Council, and Tanana Chiefs Conference.
Recommended Determination
8-18
December 2022
-------
Section 8
References
Luck, M., N. Maumenee, D. Whited, J. Lucotch, S. Chilcote, M. Lorang, D. Goodman, K. McDonald, J. Kimball,
and J. Stanford. 2010. Remote sensing analysis of physical complexity of North Pacific Rim rivers to
assist wild salmon conservation. Earth Surface Processes and Landforms 35:1330-1343.
Lytle, D. A., and N. L. Poff. 2004. Adaptation to natural flow regimes. Trends in Ecology & Evolution
19:94-100.
MacLean, S. 2003. Influences ofhydrological processes on the spatial and temporal variation in spawning
habitat quality of two Chum Salmon stocks in Interior Alaska. M.S. Thesis, Department of Fisheries,
University of Alaska Fairbanks.
Marra, P. P., E. B. Cohen, S. R. Loss, J. E. Rutter, and C. M. Tonra. 2015. A call for full annual cycle research
in animal ecology. Biology Letters 11:20150552.
Matthews, W. J., and E. Marsh-Matthews. 2003. Effects of drought on fish across axes of space, time and
ecological complexity. Freshwater Biology 48:1232-1253.
May, S. A., G. J. McKinney, R. Hilborn, L. Hauser, and K. A. Naish. 2020. Power of a dual-use SNP panel for
pedigree reconstruction and population assignment. Ecology and Evolution 10:9522-9531.
McCracken, B. W. 2021. Spawning Site Selection ofCoho Salmon Oncorhynchus kisutch in Susitna River
Tributaries, Alaska. M.S. Thesis, Department of Fisheries, University of Alaska Fairbanks.
McCullough, D. A., J. M. Bartholow, H. I. Jager, R. L. Beschta, E. F. Cheslak, M. L. Deas, J. L. Ebersole, J. S.
Foott, S. L. Johnson, K. R. Marine, M. G. Mesa, J. H. Petersen, Y. Souchon, K. F. Tiffan, and W. A.
Wurtsbaugh. 2009. Research in thermal biology: Burning questions for coldwater stream fishes.
Reviews in Fisheries Science 17:90-115.
McGlauflin, M. T., D. E. Schindler, L. W. Seeb, C. T. Smith, C. Habicht, and J. E. Seeb. 2011. Spawning habitat
and geography influence population structure and juvenile migration timing of sockeye salmon in
the Wood River lakes, Alaska. Transactions of the American Fisheries Society 140:763-782.
McKinley Research Group. 2021. The Economic Benefits of Bristol Bay Salmon. Prepared for the Bristol
Bay Defense Fund. Anchorage, AK.
McKinney, G. J., C. E. Pascal, W. D. Templin, S. E. Gilk-Baumer, T. H. Dann, L. W. Seeb, and J. E. Seeb. 2020.
Dense SNP panels resolve closely related Chinook salmon populations. Canadian Journal of Fisheries
and Aquatic Sciences 77:451-461.
Meek, M. H., M. R. Stephens, A. Goodbla, B. May, and M. R. Baerwald. 2020. Identifying hidden
biocomplexity and genomic diversity in Chinook salmon, an imperiled species with a history of
anthropogenic influence. Canadian Journal of Fisheries and Aquatic Sciences 77:534-547.
Meka, J. M., E. E. Knudsen, D. C. Douglas, and R. B. Benter. 2003. Variable migratory patterns of different
adult rainbow trout life history types in a southwest Alaska watershed. Transactions of the American
Fisheries Society 132:717-732.
Recommended Determination
8-19
December 2022
-------
Section 8
References
Mellina, E., R. D. Moore, S. G. Hinch, J. S. Macdonald, and G. Pearson. 2002. Stream temperature responses
to clearcut logging in British Columbia: the moderating influences of groundwater and headwater
lakes. Canadian Journal of Fisheries and Aquatic Sciences 59:1886-1900.
Meyer, J. L., D. L. Strayer, J. B. Wallace, S. L. Eggert, G. S. Helfman, and N. E. Leonard. 2007. The
contribution of headwater streams to biodiversity in river networks. Journal of the American Water
Resources Association 43:86-103.
Miettinen, A., S. Palm, J. Dannewitz, E. Lind, C. R. Primmer, A. Romakkaniemi, J. Ostergren, and V. L.
Pritchard. 2021. A large wild salmon stock shows genetic and life history differentiation within, but
not between, rivers. Conservation Genetics 22:35-51.
Miller, D. J., K. Burnett, and L. Benda. 2008. Factors controlling availability of spawning habitat for
salmonids atthe basin scale. American Fisheries Society Symposium 65:103-120.
Minard, R. E., M. Alexandersdottir, and S. Sonnichsen. 1992. Estimation of Abundance, Seasonal
Distribution, and Size and Age Composition of Rainbow Trout in the Kvichak River, Alaska, 1986-1991.
Fishery Data Series No. 92-51. Anchorage, AK: Alaska Department of Fish and Game, Division of
Sport Fish.
Mobley, K. B., H. Granroth-Wilding, M. Ellmen, J. P. Vaha, T. Aykanat, S. E. Johnston, P. Orell, J. Erkinaro,
and C. R. Primmer. 2019. Home ground advantage: Local Atlantic salmon have higher reproductive
fitness than dispersers in the wild. Science Advances 5:eaavll2.
Montgomery, D. R., E. M. Beamer, G. R. Pess, and T. P. Quinn. 1999. Channel type and salmonid spawning
distribution and abundance. Canadian Journal of Fisheries and Aquatic Sciences 56:377-387.
Montgomery, D. R., and J. M. Buffington. 1997. Channel-reach morphology in mountain drainage basins.
Geological Society of America Bulletin 109:596-611.
Moore, J. W. 2015. Bidirectional connectivity in rivers and implications for watershed stability and
management. Canadian Journal of Fisheries and Aquatic Sciences 72:785-795.
Moore, J. W., B. M. Connors, and E. E. Hodgson. 2021. Conservation risks and portfolio effects in mixed-
stock fisheries. Fish and Fisheries 22:1024-1040.
Moore, J. W., and D. E. Schindler. 2004. Nutrient export from freshwater ecosystems by anadromous
sockeye salmon [Oncorhynchus nerka). Canadian Journal of Fisheries and Aquatic Sciences 61:1582-
1589.
Moore, J. W., J. D. Yeakel, D. Peard, J. Lough, and M. Beere. 2014. Life-history diversity and its importance
to population stability and persistence of a migratory fish: steelhead in two large North American
watersheds. Journal of Animal Ecology 83:1035-1046.
Morrow, J. E. 1980. The Freshwater Fishes of Alaska. Alaska Northwest Publishing Co.
Recommended Determination
8-20
December 2022
-------
Section 8
References
Morstad, S. 2003. Kvichak River Sockeye Salmon Spawning Ground Surveys, 1955-2002. Regional
Information Number 2A02-32. Anchorage, AK: Alaska Department of Fish and Game.
Mouw, J. E. B., T. H. Tappenbeck, and J. A. Stanford. 2014. Spawning tactics of summer Chum Salmon
Oncorhynchus keta in relation to channel complexity and hyporheic exchange. Environmental Biology
of Fishes. 97:1095-1107.
Murphy, N. J., C. D. Schraer, M. C. Thiele, E. J. Boyko, L. R. Bulkow, B. J. Doty, and A. P. Lanier. 1995.
Dietary change and obesity associated with glucose intolerance in Alaska Natives. Journal of the
American Dietetic Association 95:676-682.
Mushet, D. M., L. C. Alexander, M. Bennett, K. Schofield, J. R. Christensen, G. Ali, A. Pollard, K. Fritz, and M.
W. Lang. 2019. Differing modes of biotic connectivity within freshwater ecosystem mosaics. Journal
of the American Water Resources Association 55:307-317.
Naiman, R. J., R. E. Bilby, D. E. Schindler, and J. M. Helfield. 2002. Pacific salmon, nutrients, and the
dynamics of freshwater and riparian ecosystems. Ecosystems 5:399-417.
Naish, K. A., J. E. Taylor III, P. S. Levin, T. P. Quinn, J. R. Winton, D. Huppert, and R. Hilborn. 2008. An
evaluation of the effects of conservation and fishery enhancement hatcheries on wild populations of
salmon. Advances in Marine Biology 53:61-194.
NDM (Northern Dynasty Minerals Ltd.). 2006. Pebble Project—Water Right Applications Submitted to the
Alaska Department of Natural Resources. Available:
http://dnr.alaska.gov/mlw/mining/largemine/pebble/water-right-apps/index.cfm. Accessed:
October 12, 2012.
Nehlsen, W., J. E. Williams, and J. A. Lichatowich. 1991. Pacific salmon at the crossroads: stocks at risk
from California, Oregon, Idaho, and Washington. Fisheries 16:4-21.
Nesbitt, H. K., and J. W. Moore. 2016. Species and population diversity in Pacific salmon fisheries
underpin indigenous food security. Journal of Applied Ecology 53:1489-1499.
Nickelson, T. E., J. D. Rodgers, S. L. Johnson, and M. F. Solazzi. 1992. Seasonal changes in habitat use by
juvenile coho salmon (Oncorhynchus kisutch) in Oregon coastal streams. Canadian Journal of
Fisheries and Aquatic Sciences 49:783-789.
NMWC (Nushagak-Mulchatna Watershed Council). 2007. NushagakRiver Watershed Traditional Use
Area Conservation Plan. Dillingham and Anchorage: Bristol Bay Native Association, Curyung Tribal
Council, and The Nature Conservancy. November.
Nobmann, E. D., R. Ponce, C. Mattil, R. Devereux, B. Dyke, S. 0. E. Ebbesson, S. Laston, J. MacCluer, D.
Robbins, T. Romenesko, G. Ruotolo, C. R. Wenger, and B. V. Howard. 2005. Dietary intakes vary with
age among Eskimo adults of northwest Alaska in the GOCADAN study, 2000-2003. Journal of
Nutrition 135:856-862.
Recommended Determination
8-21
December 2022
-------
Section 8
References
Novak, R., J. G. Kennen, R. W. Abele, C. F. Baschon, D. M. Carlisle, L. Dlugolecki, D. M. Eignor, J. E.
Flotemersch, P. Ford, J. Fowler, R. Galer, L. P. Gorgon, S. E. Hansen, B. Herbold, T. E. Johnson, J. M.
Johnston, C. P. Konrad, B. Leamond, and P. W. Seelbach. 2016. Final EPA-USGS Technical Report:
Protecting Aquatic Life from Effects of Hydrological Alteration. Washington, DC: U.S. Environmental
Protection Agency and U.S. Geological Survey.
NPS (National Park Service). 2022. Annual Park Recreation Visitation (1982-2021), Lake Clark National
Park and Preserve and Katmai National Park. Available:
https://irmadev.nps.gov/Stats/SSRSReports/Park%20Specific%20Reports/Annual%20Park%20Re
creation%20Visitation%20(1904%20-%20Last%20Calendar%20Year. Accessed: March 23, 2022.
NRC (National Research Council). 1996. Upstream: Salmon and Society in the Pacific Northwest. National
Academy Press, Washington, DC.
Olsen, J. B., S. J. Miller, W. J. Spearman, and J. K. Wenburg. 2003. Patterns of intra- and inter-population
genetic diversity in Alaskan coho salmon: Implications for conservation. Conservation Genetics
4:557-569.
Olsen, J. B., P. A. Crane, B. G. Flannery, K. Dunmall, W. D. Templin, and J. K. Wenburg. 2011. Comparative
landscape genetic analysis of three Pacific salmon species from subarctic North America.
Conservation Genetics 12:223-241.
O'Neal, S., and C. A. Woody. 2011. Canada's Fraser River: Reasons for sockeye salmon declines with a
comparison to Bristol Bay. Anchorage, AK: Fisheries Research and Consulting.
Ostberg, C. 0., S. D. Pavlov, and L. Hauser. 2009. Evolutionary relationships among sympatric life history
forms of Dolly Varden inhabiting the landlocked Kronotsky Lake, Kamchatka, and a neighboring
anadromous population. Transactions of the American Fisheries Society 138:1-14.
Pahl-Wostl, C., A. Arthington, J. Bogardi, S. E. Bunn, H. Hoff, L. Lebel, E. Nikitina, M. Palmer, N. L. Poff, K.
Richards, M. Schluter, R. Schulze, A. St-Hilare, R. Tharme, K. Tockner, and D. Tsegai. Environmental
flows and water governance: managing sustainable water uses. Current Opinion in Environmental
Sustainability 5:341-351.
Peery, C. A., K. L. Kavanagh, and J. M. Scott. 2003. Pacific salmon: Setting ecologically defensible recovery
goals. Bioscience 53:622-623.
Pess, G. R., D. R. Montgomery, E. A. Steel, R. E. Bilby, B. E. Feist, and H. M. Greenberg. 2002. Landscape
characteristics, land use, and coho salmon (Oncorhynchus kisutch) abundance, Snohomish River,
Wash., USA. Canadian Journal of Fisheries and Aquatic Sciences 59:613-623.
Peterson, D. A., R. Hilborn, and L. Hauser. 2014. Local adaptation limits lifetime reproductive success of
dispersers in a wild salmon metapopulation. Nature Communications 5:3696.
Recommended Determination
8-22
December 2022
-------
Section 8
References
Petrosky, C. E., H. A. Schaller, and P. Budy. 2001. Productivity and survival rate trends in the freshwater
spawning and rearing stage of Snake River chinook salmon (Oncorhyrtchus tshawytscha). Canadian
Journal of Fisheries and Aquatic Sciences 58:1196-1207.
Phillis, C. C., A. M. Sturrock, R. C. Johnson, and P. K. Weber. 2018. Endangered winter-run Chinook
salmon rely on diverse rearing habitats in a highly altered landscape. Biological Conservation
217:358-362.
Piccolo, J. J., and M. S. Wipfli. 2002. Does red alder (Alnus rubra) in upland riparian forests elevate
macroinvertebrate and detritus export from headwater streams to downstream habitats in
southeastern Alaska? Canadian Journal of Fisheries and Aquatic Sciences 59:503-513.
Piccolo, J. J., N. F. Hughes, and M. D. Bryant. 2008. Water velocity influences prey detection and capture
by drift-feeding juvenile coho salmon (Oncorhynchus kisutch) and steelhead [Oncorhynchus mykiss
irideus). Canadian Journal of Fisheries and Aquatic Sciences 65:266-275.
Pinsky, M. L., D. B. Springmeyer, M. N. Goslin, and X. Augerot. 2009. Range-wide selection of catchments
for Pacific salmon conservation. Conservation Biology 23:680-691.
Pitman, K. J., J. W. Moore, M. R. Sloat, A. H. Beaudreau, A. Bidlack, R. E. Brenner, E. W. Hood, G. R. Pess, N.
J. Mantua, A. M. Milner, V. Radic, G. H. Reeves, D. E. Schindler, and D. C. Whited. 2020. Glacier retreat
and Pacific salmon. Bioscience 70:220-236.
PLP (Pebble Limited Partnership). 2011. Pebble Project Environmental Baseline Document, 2004 through
2008. Anchorage, AK. Available: https://www.arlis.org/docs/vol2/Pebble/2004-2008EBDIndex.pdf.
PLP. 2017. Pebble Project Department of the Army Application for Permit POA-2017-00271 (dated
December 22, 2017). Anchorage, AK.
PLP. 2018a. Pebble Project Supplemental Environmental Baseline Data Report, 2004-2012. Anchorage,
AK.
PLP. 2018b. RFI048: Revised Habitat Time Series Analysis. AECOM Request for Information to Pebble
Limited Partnership, September 28.
PLP. 2018c. RFI 062: Scenario for Expanded Development of Pebble. AECOM Request for Information to
Pebble Limited Partnership, September 6.
PLP. 2018d. RFI 069: Tailings Disposal Options. AECOM Request for Information to Pebble Limited
Partnership, September 10.
PLP. 2018e. RFI 098: TSF Options, Mine Area. AECOM Request for Information, Pebble Limited
Partnership, November 3.
PLP. 2019a. RFI 109f: Streamflow Estimates from New Groundwater Model. AECOM Request for
Information to Pebble Limited Partnership, October 11.
Recommended Determination
8-23
December 2022
-------
Section 8
References
PLP. 2019b. RFI135: Monitoring and Adaptive Management Plan. AECOM Request for Information,
Pebble Limited Partnership, December 23.
PLP. 2019c. RFI 149: Fish Habitat Modeling Results for Adult Resident Salmonids by Stream Reach. AECOM
Request for Information to Pebble Limited Partnership, November 21.
PLP. 2019d. RFI 150: Siting Criteria for Main Water Management Pond. AECOM Request for Information
to Pebble Limited Partnership, October 21.
PLP. 2020a. Pebble Project Draft Compensatory Mitigation Plan for Department of the Army Application
for Permit POA-2017-00271 (January 2020 Draft).
PLP. 2020b. Pebble Project Department of the Army Application for Permit POA-2017-00271 (dated
June 8, 2020). Anchorage, AK.
PLP. 2020c. Pebble Project Compensatory Mitigation Plan for Department of the Army Application for
Permit POA-2017-00271. November 4.
PLP. 2020d. RFI 161: Watershed Model and Streamflow Change. AECOM Request for Information to
Pebble Limited Partnership, February 20.
Poff, N. L., and J. K. H. Zimmerman. 2010. Ecological responses to altered flow regimes: a literature
review to inform the science and management of environmental flows. Freshwater Biology 55:194-
205.
Poff, N. L., J. D. Allan, M. B. Bain, J. R. Karr, K. L. Prestegaard, B. D. Richter, R. E. Sparks, and J. C.
Stromberg. 1997. The natural flow regime: a paradigm for river conservation and restoration.
Bioscience 47:769-784.
Pollock, M. M., M. Heim, and D. Werner. 2003. Hydrologic and geomorphic effects of beaver dams and
their influence on fishes. The Ecology and Management of Wood in World Rivers 37:213-233.
Pollock, M. M., G. R. Pess, T. J. Beechie, and D. R. Montgomery. 2004. The importance of beaver ponds to
coho salmon production in the Stillaguamish River basin, Washington, USA. North American Journal
of Fisheries Management 24:749-760.
Poole, G. C., J. B. Dunham, D. M. Keenan, S. T. Sauter, D. A. McCullough, C. Mebane, J. C. Lockwood, D. A.
Essig, M. P. Hicks, D. J. Sturdevant, E. J. Materna, S. A. Spalding, J. Risley, and M. Deppman. 2004. The
case for regime-based water quality standards. Bioscience 54:155-161.
Postel, S., and B. Richter. 2003. Rivers for Life: Managing Water for People and Nature. Washington, DC:
Island Press.
Power, G., R. S. Brown, and J. G. Imhof. 1999. Groundwater and fish - insights from northern North
America. Hydrological Processes 13:401-422.
Recommended Determination
8-24
December 2022
-------
Section 8
References
Quinn, T. P. 2018. The Behavior and Ecology of Pacific Salmon and Trout, 2nd Edition. Seattle, WA:
University of Washington Press.
Quinn, T. P., A. P. Hendry, and L. A. Wetzel. 1995. The influence of life history trade-offs and the size of
incubation gravels on egg size variation in sockeye salmon (Oncorhynchus nerka). Oikos 74:425-438.
Quinn, T. P., I. J. Stewart, and C. P. Boatright. 2006. Experimental evidence of homing to site of incubation
by mature sockeye salmon (Oncorhynchus nerka). Animal Behaviour 72:941-949.
Quinn, T. P., A. P. Hendry, and G. B. Buck. 2001. Balancing natural and sexual selection in sockeye
salmon: interactions between body size, reproductive opportunity and vulnerability to predation by
bears. Evolutionary Ecology Research 3:917-937.
Quinn, T. P., H. B. Rich, D. Gosse, and N. Schtickzelle. 2012. Population dynamics and asynchrony at fine
spatial scales: a case history of sockeye salmon (Oncorhynchus nerka) population structure in Alaska,
USA. Canadian Journal of Fisheries and Aquatic Sciences 69:297-306.
Raborn, S. W., and M. R. Link. 2022. Annual Report for the 2021 PortMoller Test Fishery. Prepared for
Bristol Bay Science and Research Institute, Bristol Bay Fisheries Collaborative, and Bristol Bay
Regional Seafood Development Association.
Rahr, G. R., J. A. Lichatowich, R. Hubley, and S. M. Whidden. 1998. Sanctuaries for native salmon: A
conservation strategy for the 21st century. Fisheries 23:6-36.
Rains, M. C. 2011. Water sources and hydrodynamics of closed-basin depressions, Cook Inlet Region,
Alaska. Wetlands 31:377-387.
Ramstad, K. M., C. A. Woody, and F. W. Allendorf. 2010. Recent local adaptation of sockeye salmon to
glacial spawning habitats. Evolutionary Ecology 24:391-411.
Rand, P. S., B. A. Berejikian, A. Bidlack, D. Bottom, J. Gardner, M. Kaeriyama, R. Lincoln, M. Nagata, T. N.
Pearsons, M. Schmidt, W. W. Smoker, L. A. Weitkamp, and L. A. Zhivotovsky. 2012. Ecological
interactions between wild and hatchery salmonids and key recommendations for research and
management actions in selected regions of the North Pacific. Environmental Biology of Fishes
94:343-358.
RAP (Riverscape Analysis Project). 2011. The Riverscape Analysis Project. Available:
http://rap.ntsg.umt.edu. Accessed: December 2011.
Reynolds, J. B. 1997. Ecology of overwintering fishes in Alaskan freshwaters. Pages 281-302 in A. M.
Milner and M. W. Oswood (eds.), Freshwaters of Alaska. Ecological Studies, Vol. 119. New York, NY:
Springer.
Reynolds, J. B. 2000. Life History Analysis ofTogiak River Char through Otolith Microchemistry. Fairbanks,
AK: Alaska Cooperative Fish and Wildlife Research Unit, University of Alaska Fairbanks.
Recommended Determination
8-25
December 2022
-------
Section 8
References
Richardson, J. S., R. J. Naiman, F. J. Swanson, and D. E. Hibbs. 2005. Riparian communities associated with
Pacific Northwest headwater streams: Assemblages, processes, and uniqueness. Journal of the
American Water Resources Association 41:935-947.
Richter, B. D., M. M. Davis, C. Apse, and C. Konrad. 2012. A presumptive standard for environmental flow
protection. River Research and Applications 28:1312-1321.
Rinella, D. J., R. Shaftel, and D. Athons. 2018. Salmon Resources and Fisheries. Pages 357-392 in C. A.
Woody (ed.), Bristol Bay Alaska: Natural Resources of the Aquatic and Terrestrial Ecosystems.
Plantation, FL: J. Ross Publishing.
Rogers, L. A., and D. E. Schindler. 2008. Asynchrony in population dynamics of sockeye salmon in
southwest Alaska. Oikos 117:1578-1586.
Rogers, L. A., and D. E. Schindler. 2011. Scale and the detection of climatic influences on the productivity
of salmon populations. Global Change Biology 17:2546-2558.
Romberg, W. J., K. Sundet, M. Martz, and I. Rafferty. 2021. Estimates of Participation, Catch, and Harvest in
Alaska Sport Fisheries During 2017. Fishery Data Series No. 21-03. Anchorage, AK: Alaska
Department of Fish and Game, Divisions of Sport Fish and Commercial Fisheries.
Ruff, C. P., D. E. Schindler, J. B. Armstrong, K. T. Bentley, G. T. Brooks, G. W. Holtgrieve, M. T. McGlauflin, C.
E. Torgersen, and J. E. Seeb. 2011. Temperature-associated population diversity in salmon confers
benefits to mobile consumers. Ecology 92:2073-2084.
Ruggerone, G. T., R. M. Peterman, B. Dorner, and K. W. Myers. 2010. Magnitude and trends in abundance
of hatchery and wild pink salmon, chum salmon, and sockeye salmon in the North Pacific Ocean.
Marine and Coastal Fisheries 2:306-328.
Russell, R. 1977. Rainbow Trout Life History Studies in Lower Talarik Creek—Kvichak Drainage.
Anchorage, AK: Alaska Department of Fish and Game.
Salo, E. 0.1991. Life history of chum salmon (Oncorhynchus keta). Pages 231-310 in C. Groot and L.
Margolis (eds.), Pacific Salmon Life Histories. Vancouver BC: UBC Press.
Sandercock, F. K. 1991. Life history of coho salmon (Oncorhynchus kisutch). Pages 397-445 in C. Groot
and L. Margolis (eds.), Pacific Salmon Life Histories. Vancouver, BC: UBC Press.
Scanlon, B. 2000. The Ecology of Arctic Char and the Dolly Varden in the BecharofLake Drainage, Alaska.
Fairbanks, AK: University of Alaska.
Scheuerell, M. D., P. S. Levin, R. W. Zabel, J. G. Williams, and B. L. Sanderson. 2005. A new perspective on
the importance of marine-derived nutrients to threatened stocks of Pacific salmon (Oncorhynchus
spp.). Canadian Journal of Fisheries and Aquatic Sciences 62:961-964.
Recommended Determination
8-26
December 2022
-------
Section 8
References
Scheuerell, M. D., J. W. Moore, D. E. Schindler, and C. J. Harvey. 2007. Varying effects of anadromous
sockeye salmon on the trophic ecology of two species of resident salmonids in southwest Alaska.
Freshwater Biology 52:1944-1956.
Schichnes, J., and M. Chythlook. 1991. Contemporary Use of Fish and Wildlife in Ekwok, Koliganek, and
New Stuyahok, Alaska. Technical Paper No. 185. Juneau, AK: Alaska Department of Fish and Game.
Schindler, D. E., X. Augerot, E. Fleishman, N. J. Mantua, B. Riddell, M. Ruckelshaus, J. Seeb, and M.
Webster. 2008. Climate change, ecosystem impacts, and management for Pacific salmon. Fisheries
33:502-506.
Schindler, D. E., R. Hilborn, B. Chasco, C. P. Boatright, T. P. Quinn, L. A. Rogers, and M. S. Webster. 2010.
Population diversity and the portfolio effect in an exploited species. Nature 465:609-612.
Schindler, D. E., J. B. Armstrong, K. T. Bentley, K. Jankowski, P. J. Lisi, and L. X. Payne. 2013. Riding the
crimson tide: mobile terrestrial consumers track phenological variation in spawning of an
anadromous fish. Biology Letters 9:20130048.
Schindler, D. E., J. B. Armstrong, and T. E. Reed. 2015. The portfolio concept in ecology and evolution.
Frontiers in Ecology and the Environment 13:257-263.
Schindler, D. E., P. R. Leavitt, C. S. Brock, S. P. Johnson, and P. D. Quay. 2005. Marine-derived nutrients,
commercial fisheries, and production of salmon and lake algae in Alaska. Ecology 86:3225-3231.
Schindler, D. E., L. W. Seeb, and J. E. Seeb. 2018. Diversity in Bristol Bay Sockeye Salmon and their
habitat: Implications for fisheries and wildlife. Pages 477-491 in C. A. Woody (ed.), Bristol Bay
Alaska: Natural Resources of the Aquatic and Terrestrial Ecosystems. Plantation, FL: J. Ross
Publishing.
Schoen, E. R., K. W. Sellmer, M. S. Wipfli, J. A. Lopez, R. Ivanoff, and B. E. Meyer. 2022. Piscine predation
on juvenile salmon in sub-arctic Alaskan rivers: Associations with season, habitat, predator size and
streamflow. Ecology of Freshwater Fish 31:243-259.
Schofield, K. A., L. C. Alexander, C. E. Ridley, M. K. Vanderhoof, K. M. Fritz, B. C. Autrey, J. E. DeMeester, W.
G. Kepner, C. R. Lane, S. G. Leibowitz, and A. I. Pollard. 2018. Biota connect aquatic habitats
throughout freshwater ecosystem mosaics. Journal of the American Water Resources Association
54:372-399.
SEC (Securities and Exchange Commission). 2011. Northern Dynasty Minerals Ltd. February 24,2011
Filing. Available:
http://www.sec.gOv/Archives/edgar/data/1164771/000106299311000722/0001062993-ll-
000722-index.htm. Accessed: April 23, 2022.
Sepulveda, A. J., D. S. Rutz, S. S. Ivey, K. J. Dunker, and J. A. Gross. 2013. Introduced northern pike
predation on salmonids in southcentral Alaska. Ecology of Freshwater Fish 22:268-279.
Recommended Determination
8-27
December 2022
-------
Section 8
References
Sethi, S. A., and T. Tanner. 2014. Spawning distribution and abundance of a northern Chinook salmon
population. Fisheries Management and Ecology 21:427-438.
Shallin Busch, D., M. Sheer, K. Burnett, P. McElhany, and T. Cooney. 2013. Landscape-level model to
predict spawning habitat for lower Columbia River fall Chinook salmon (Oncorhynchus tshawytscha).
River Research and Applications 29:297-312.
Shanley, C. S., and D. M. Albert. 2014. Climate change sensitivity index for Pacific salmon habitat in
southeast Alaska. PLoS One 9:ell2926.
Shedd, K. R., T. H. Dann, H. A. Hoyt, M. B. Foster, and C. Habicht. 2016. Genetic Baseline of North American
Sockeye Salmon for Mixed Stock Analyses ofKodiak Management Area Commercial Fisheries, 2014-
2016. Fishery Manuscript Series No. 16-03. Anchorage, AK: Alaska Department of Fish and Game,
Divisions of Sport Fish and Commercial Fisheries.
Shrimpton, J. M., K. D. Warren, N. L. Todd, C. J. McRae, G. J. Glova, K. H. Telmer, and A. D. Clarke. 2014.
Freshwater movement patterns by juvenile Pacific salmon Oncorhynchus spp. before they migrate to
the ocean: Oh the places you'll go! Journal of Fish Biology 85:987-1004.
Smith, R. J., K. A. Hobson, H. N. Koopman, and D. M. Lavigne. 1996. Distinguishing between populations of
freshwater and saltwater harbor seals (Phoca vitulina) using stable isotope ratios and fatty acid
profiles. Canadian Journal of Fisheries and Aquatic Sciences 53:272-279.
Smith, M. K., and P. Zwollo. 2020. Transient increase in abundance of B lineage but not myeloid-lineage
cells in anterior kidney of sockeye salmon during return migration to the natal grounds. Fish and
Shellfish Immunology 107:395-402.
Solazzi, M. F., T. E. Nickelson, S. L. Johnson, and J. D. Rodgers. 2000. Effects of increasing winter rearing
habitat on abundance of salmonids in two coastal Oregon streams. Canadian Journal of Fisheries and
Aquatic Sciences 57:906-914.
Sommer, T. R., M. L. Nobriga, W. C. Harrell, W. Batham, and W. J. Kimmerer. 2001. Floodplain rearing of
juvenile chinook salmon: evidence of enhanced growth and survival. Canadian Journal of Fisheries
and Aquatic Sciences 58:325-333.
Spence, B. C. 1995. Geographic variation in timing of fry emergence and smolt migration ofCoho Salmon
(Oncorhynchus kisutch). Ph.D. thesis, Department of Fisheries and Wildlife, Oregon State University.
Stanford, J. A., M. S. Lorang, and F. R. Hauer. 2005. The shifting habitat mosaic of river ecosystems.
Internationale Vereinigung fur theoretische und angewandte Limnologie: Verhandlungen 29:123-136.
Stewart, I. J., T. P. Quinn, and P. Bentzen. 2003. Evidence for fine-scale natal homing among island beach
spawning sockeye salmon, Oncorhynchus nerka. Environmental Biology of Fishes 67:77-85.
Recommended Determination
8-28
December 2022
-------
Section 8
References
Stickman, K., Balluta, A., McBurney, M. and Young, D. 2003. K'ezghlegh: Nondalton traditional ecological
knowledge of freshwater fish. U.S. Fish and Wildlife Service, Office of Subsistence Management,
Fisheries Resource Monitoring Program, Final Report (Study No. 01-075), Nondalton Tribal Council,
AK.
Szarzi, N. J, S. J. Fleischman, R. A. Clark, and C. M. Kerkvliet. 2007. Stock Status and Recommended
Escapement Goal for Anchor River Chinook Salmon. Fisheries Manuscript No. 07-05. Anchorage, AK:
Alaska Department of Fish and Game, Divisions of Sport Fish and Commercial Fisheries.
Tank, J. L., E. J. Rosi-Marshall, N. A. Griffiths, S. A. Entrekin, and M. L. Stephen. 2010. A review of
allochthonous organic matter dynamics and metabolism in streams. Journal of the North American
BenthologicalSociety 29:118-146.
Tiernan, A., T. Elison, T. Sands, J. Head, S. Vega, and G. Neufeld. 2021.2020 Bristol Bay Area Annual
Management Report. Fishery Management Report No. 21-16. Anchorage, AK: Alaska Department of
Fish and Game, Divisions of Sport Fish and Commercial Fisheries.
Tillotson, M. D., H. K. Barnett, M. Bhuthimethee, M. E. Koehler, and T. P. Quinn. 2019. Artificial selection
on reproductive timing in hatchery salmon drives a phenological shift and potential maladaptation
to climate change. Evolutionary Applications 12:1344-1359.
Ueda, H. 2019. Sensory mechanisms of natal stream imprinting and homing on Oncorhynchus spp.
Journal of Fish Biology 95:293-303.
USACE (U.S. Army Corps of Engineers). 1987. Corps of Engineers Wetlands Delineation Manual. Technical
Report Y-87-1. Vicksburg, MS: Wetlands Research Program.
USACE. 2020a. Pebble Project EIS: Final Environmental Impact Statement. Department of the Army
Permit #POA-2017-00271.
USACE. 2020b. Record of Decision for Application Submitted by Pebble Limited Partnership to USACE
(Department of the Army Permit #POA-2017-00271).
USACE. 2022. [Unpublished data associated with the Pebble Project FEIS administrative record,
provided to Amy Jensen, Regional Wetland Coordinator, EPA Region 10 by Alaska District.] March
24.
U.S. Census Bureau. 2022.2020 Census Results. Available: https://www.census.gov/programs-
surveys/decennial-census/decade/2020/2020-census-results.html. Accessed: May 22, 2022.
USFWS (U.S. Fish and Wildlife Service). 2011. Traditional Ecological Knowledge for Application by Service
Scientists. Traditional Ecological Knowledge Fact Sheet. U.S. Fish and Wildlife Service, Native
American Program. Available: https://www.fws.gov/media/traditional-ecological-knowledge-fact-
sheet. Accessed: May 17, 2022.
Recommended Determination
8-29
December 2022
-------
Section 8
References
USFWS. 2021. National Wetlands Inventory. Available: http://www.fws.gov/wetlands/Wetlands-
Mapper.html. Accessed: January 27, 2022.
USFWS. 2022a. National Wetlands Inventory, Wetlands Mapper. Available:
https://www.fws.gov/program/national-wetlands-inventory/wetlands-mapper. Accessed: April 5,
2022.
USFWS. 2022b. USFWS Scalable Mapping for the National Wetlands Inventory - Overview. Madison, WI:
U.S. Fish and Wildlife Service, Branch of Geospatial Mapping and Technical Support.
USGS (U.S. Geological Survey). 2012. National Hydrography Dataset, High Resolution, Alaska. Accessed:
October 16, 2012.
USGS. 2021a. National Boundary Dataset (NBD) in Alaska State or Territory (published 20211211)
FileGDB. Available: http://viewer.nationalmap.gov/-Accessed: January 14, 2022.
USGS. 2021b. National Hydrography Dataset Best Resolution (NHD) for Hydrological Unit (HU) 4 -1903.
Available: http://viewer.nationalmap.gov/. Accessed: January 14, 2022.
USGS. 2022. National Hydrography Dataset. Available: https://www.usgs.gov/national-
hydrography/national-hydrography-dataset. Accessed: April 5, 2022.
Vannote, R. L., G. W. Minshall, K. W. Cummins, J. R. Sedell, and C. E. Cushing. 1980. The river continuum
concept. Canadian Journal of Fisheries and Aquatic Sciences 37:130-137.
Varnavskaya, N. V., C. C. Wood, R. J. Everett, R. L. Wilmot, V. S. Varnavsky, V. V. Midanaya, and T. P. Quinn.
1994. Genetic differentiation of subpopulations of sockeye salmon (Oncorhynchus nerka) within
lakes of Alaska, British Columbia, and Kamchatka, Russia. Canadian Journal of Fisheries and Aquatic
Sciences 51:147-157.
Veale, A. J., and M. A. Russello. 2017. An ancient selective sweep linked to reproductive life history
evolution in sockeye salmon. Scientific Reports 7:1747.
Vynne, C., E. Dovichin, N. Fresco, N. Dawson, A. Joshi, B. E. Law, K. Lertzman, S. Rupp, F. Schmiegelow,
and E. J. Trammell. 2021. The importance of Alaska for climate stabilization, resilience, and
biodiversity conservation. Frontiers in Forests and Global Change 04:701277.
Walter, J. K., R. E. Bilby, and B. R. Fransen. 2006. Effects of Pacific salmon spawning and carcass
availability on the caddisfly Ecclisomyia conspersa (Trichoptera: Limnephilidae). Freshwater Biology
51:1211-1218.
Waples, R. S., and S. T. Lindley. 2018. Genomics and conservation units: The genetic basis of adult
migration timing in Pacific salmonids. Evolutionary Applications 11:1518-1526.
Warnock, N., and M. Smith. 2018. The Importance of Bristol Bay to Marine Birds of the World. Pages
263-288 in C. A. Woody (ed.), Bristol Bay Alaska: Natural Resources of the Aquatic and Terrestrial
Ecosystems. Plantation, FL: J. Ross Publishing.
Recommended Determination
8-30
December 2022
-------
Section 8
References
Warren, M., M.J. Dunbar, and C. Smith. 2015. River flow as a determinant of salmonid distribution and
abundance: a review. Environmental Biology of Fishes 98:1695-1717.
West, R. L., M. W. Smith, W. E. Barber, J. B. Reynolds, and H. Hop. 1992. Autumn migration and
overwintering of Arctic grayling in coastal streams of the Arctic National Wildlife Refuge, Alaska
Transactions of the American Fisheries Society 121:709-715.
WHSRN (Western Hemisphere Shorebird Research Network). 2022a. Kvichak Bay. Available:
https://whsrn.org/whsrn_sites/kvichak-bay/. Accessed: November 9, 2022.
WHSRN. 2022b. Nushagak Bay. Available: https://whsrn.org/whsrn_sites/nushagak-bay/. Accessed:
November 9, 2022.
Willson, M. F., S. M. Gende, and B. H. Marston. 1998. Fishes and the forest. Bioscience 48:455-462.
Wink Research & Consulting. 2018. Economic Benefits of the Bristol Bay Salmon Industry. Prepared for
the Bristol Bay Regional Seafood Development Corporation, Bristol Bay Economic Development
Corporation, and Bristol Bay Native Corporation.
Wipfli, M. S., and D. P. Gregovich. 2002. Export of invertebrates and detritus from fishless headwater
streams in southeastern Alaska: implications for downstream salmonid production. Freshwater
Biology 47:957-969.
Wipfli, M. S., J. P. Hudson, J. P. Caouette, and D. T. Chaloner. 2003. Marine subsidies in freshwater
ecosystems: Salmon carcasses increase the growth rates of stream-resident salmonids. Transactions
of the American Fisheries Society 132:371-381.
Wipfli, M. S., and J. Musslewhite. 2004. Density of red alder (Alnus rubra) in headwaters influences
invertebrate and detritus subsidies to downstream fish habitats in Alaska. Hydrobiologia 520:153-
163.
Wipfli, M. S., J. S. Richardson, and R. J. Naiman. 2007. Ecological linkages between headwaters and
downstream ecosystems: Transport of organic matter, invertebrates, and wood down headwater
channels. Journal of the American Water Resources Association 43:72-85.
Wirsing, A. J., T. P. Quinn, C. J. Cunningham, J. R. Adams, A. D. Craig, and L. P. Waits. 2018. Alaskan brown
bears (Ursus arctos) aggregate and display fidelity to foraging neighborhoods while preying on
Pacific salmon along small streams. Ecology and Evolution 8:9048-9061.
Wolfe, R. J., and R. J. Walker. 1987. Subsistence economies in Alaska: productivity, geography, and
development impacts. Arctic Anthropology 24:56-81.
Woll, C., Albert, D., and Whited, D. 2013. A Preliminary Classification and Mapping of Salmon Ecological
Systems in the Nushagak and Kvichak Watersheds, Alaska. The Nature Conservancy.
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Section 8
References
Wood, C. C. 1995. Life history variation and population structure in sockeye salmon. Pages 195-216 in J.
L. Nielsen and D. A. Powers (eds.), Evolution and the Aquatic Ecosystem: Defining Unique Units in
Population Conservation. Bethesda, MD: American Fisheries Society.
Wood, C. C., J. W. Bickham, R. J. Nelson, C. J. Foote, and J. C. Patton. 2008. Recurrent evolution of life
history ecotypes in sockeye salmon: implications for conservation and future evolution. Evolutionary
Applications 1:207-221.
Woody, C. A. 2018. Bristol Bay Alaska: Natural Resources of the Aquatic and Terrestrial Ecosystems.
Plantation, FL: J. Ross Publishing.
Woody, C. A., and S. L. O'Neal. 2010. Fish Surveys in Headwater Streams of the Nushagak and Kvichak
River Drainages, Bristol Bay, Alaska, 2008-2010. Anchorage, AK: Fisheries Research and Consulting.
Woody, C. A., and B. Higman. 2011. Groundwater as Essential Salmon Habitat in Nushagak and Kvichak
River Headwaters: Issues Relative to Mining. Report prepared for Center for Science in Public
Participation.
Young, T. B, and J. M. Little. 2019. The Economic Contribution of Bear Viewing in Southcentral Alaska.
Report prepared for the Cook Inletkeeper. Fairbanks, AK: University of Alaska Fairbanks School of
Management.
Zabel, R. W., M. D. Scheuerell, M. M. McClure, and J. G. Williams. 2006. The interplay between climate
variability and density dependence in the population viability of Chinook salmon. Conservation
Biology 20:190-200.
Zwollo, P. 2018. The humoral immune system of anadromous fish. Developmental and Comparative
Immunology 80:24-33.
Personal Communications
Lestochi, Christopher D., Colonel. USACE Alaska District. March 14, 2014—Letter to Dennis McLerran,
Regional Administrator, EPA Region 10.
Morstad, S. Fishery Biologist III, ADF&G. September 2011—Email of unpublished data to Rebecca
Shaftel.
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Appendix A
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Appendix B
Additional Information Related to the Assessment
of Aquatic Habitats and Fishes
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SR»jm
B. ADDITIONAL INFORMATION RELATED T
S^la^i ail afif i] I r>« i rtf: M u i r>i il a LS
Appendix B provides additional supporting information related to aquatic habitats within and
downstream of the mine site in the South Fork Koktuli River (SFK), North Fork Koktuli River (NFK), and
Upper Talarik Creek (UTC) watersheds and their role in supporting fish populations. As discussed in
detail in Section 4, the impacts on aquatic resources that are predicted to occur from the 2020 Mine
Plan, based on the available data (e.g., PLP 2011, PLP 2018a) and analyses reported in the Final
Environmental Impact Statement (FEIS) (USACE 2020), would likely result in significant loss of or
damage to fishery areas in the SFK and NFK watersheds. This appendix addresses additional issues
related to two key points: (1) in many cases, the FEIS states that impacts would not result in significant
adverse effects on aquatic resources, conclusions that often are not supported by the evidence provided
in the FEIS; and (2) the impacts reported in the FEIS likely underestimate or underpredict the actual
impacts that the 2020 Mine Plan would have on aquatic resources in the SFK, NFK, and UTC watersheds.
B.l Quality, Importance, and Productivity of Lost Habitats for
Fish Life Stages, Species, and Communities
As detailed in Sections 3 and 4 of this recommended determination, the evidence presented in the FEIS
supports the U.S. Environmental Protection Agency's (EPA's) conclusion that aquatic habitats lost or
degraded by the 2020 Mine Plan are of high quality, importance, and value as fishery areas. This section
provides an overview of EPA's approach and assumptions for assessing habitat quality and fish use
when determining the "quality" of the stream habitats degraded by the 2020 Mine Plan and the
"importance" or "value" of that lost habitat and altered functions for fish populations.
B.l.l Assessing Stream Habitat Quality
The FEIS concludes that loss of stream habitats under the 2020 Mine Plan would be inconsequential for
fish populations (USACE 2020: Section 4.24). This conclusion appears to be based on an assumption that
the relative quality of these habitats is low and they have minimal influence on downstream waters.
These assumptions and conclusions are not supported by the available information about these habitats
(including information provided in the FEIS), or the current science surrounding the importance of
headwater systems (Section 3.2.4, USACE 2020: Sections 4.16 and 4.24), their contributions to the
spatial and temporal availability of aquatic resources (Section 3.3.3, USACE 2020: Sections 4.16 and
4.24), and the spatial and temporal scales at which those aquatic resources vary.
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B, 1.1.1 Quality of Lost Stream Habitats
The headwater streams draining the mine site were found to have low nutrient and dissolved organic
carbon (DOC) concentrations (PLP 2018a: Appendix 9.1A), but these values do not suggest a low
capacity to support biological productivity. Nutrient and DOC concentrations in downstream reaches
and the mainstem Koktuli River generally are similar to those at the mine site (PLP 2018a: Appendix
9.1A). These mainstem habitats are productive salmon habitat, which highlights that nutrient and DOC
concentrations are not the only or even most relevant indicators of biological productivity in this region.
According to the FEIS, streams that would be lost to the 2020 Mine Plan "...tend to have higher
gradients, fewer off-channel and overwintering habitats, lower proportions of spawning gravels, and
less woody debris..." (USACE 2020: Page 3.24-5) than downstream channels. In general, channels with
gradients less than 3 percent most frequently meet the substrate and hydraulic conditions required by
stream-spawning salmon (Montgomery and Buffington 1997, Montgomery et al. 1999). Many streams
draining the mine site, particularly the smallest ones, do have gradients exceeding 3 percent (USACE
2020: Table 3.24-2); however, the anadromous fish stream losses under the 2020 Mine Plan (Table 4-1)
are dominated by reaches with gradients less than 3 percent (USACE 2020: Table 3.24-2). Furthermore,
the largest stream lengths affected, NFK tributaries 1.190 and 1.200, are documented in the FEIS as
having gradients less than 3 percent and suitable spawning substrates (USACE 2020: Table 3.24-2). No
data on off-channel habitats, woody debris, or overwintering habitats are reported for these tributaries,
although off-channel habitats were quantified at mainstem sites (USACE 2020: Section 3.24, Table 3-10).
As a result, FEIS conclusions about the quality of streams that would be lost under the 2020 Mine Plan,
relative to downstream mainstem habitats, are not supported by evidence presented in the FEIS. This
comparison between mainstem and tributary habitats also misrepresents the relationship between
these habitats. Mainstems and tributaries perform overlapping, but not duplicative, roles—mainstem
spawning habitats are productive because the headwaters that support them are currently undeveloped
and undisturbed.
B.1.1.2 Downstream Effects of Lost Stream Habitats
Losses of stream habitats under the 2020 Mine Plan also will affect downstream waters, due to reduced
inputs from lost upstream reaches. According to the FEIS,
Based on project baseline surveys, the streams directly impacted in the mine site are not considered
major contributors of marine-derived nutrients (MDN) from spawning salmon relative to downstream
portions of the river network, making terrestrial nutrient sources relatively more important. This can be
attributed to the comparatively small numbers of spawning fish, high flushing flows in the fall after
spawning has occurred, and the lack of large woody debris or pool habitats for carcass retention (USACE
2020: Page 4.24-21).
As discussed in greater detail below (Sections B.1.2 and B.2.2), the project baseline surveys looked at
highly variable spawning densities over only four or five spawning seasons (PLP 2018a: Chapter 15,
Tables 15-14 through 15-17). For this reason, these surveys provide a poor estimate of the temporal
variation in spawning densities that has been observed in the region and may be expected over the time
scales capturing the life of the mine and its attendant impacts (Rogers et al. 2013). In addition, the
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methods used to assess spawner abundance provide minimum estimates (Section B.1.2) of the
abundance of spawners within—and thus the amount of marine-derived nutrients (MDN) they
contribute to—a given reach.
The FEIS concludes, "There are abundant small headwater streams in the Koktuli River drainage that
would be unaffected by mine site development, and would continue to provide downstream inputs
important for stream productivity" (USACE 2020: Page 4.24-21). Although it is true that there are
headwater streams that would remain unaffected and continue to provide downstream inputs, there
would still be a loss of inputs from 91 miles of streams that support downstream anadromous habitats.
The FEIS indicates that approximately 20 percent of available stream habitat in the Headwaters Koktuli
watershed (i.e., the SFK and NFK watersheds) and 12 percent of available stream habitat in the larger
Koktuli River watershed would be lost to the 2020 Mine Plan (USACE 2020: Section 4.24).1 At both
spatial scales, these impacts represent a considerable and unacceptable loss of upstream habitats that
would necessarily affect downstream transport of energy and nutrients. Although the effects of these
losses would be increasingly dampened as one moves farther downstream in the river network, reaches
immediately downstream of the lost habitats would experience a complete loss of inputs from upstream
habitats, which would necessarily affect their downstream transport of energy and nutrients. Thus,
impacts to a specific downstream reach result not only from direct loss of headwater habitats under the
2020 Mine Plan, but also from how those direct losses cascade downstream through intervening reaches
that are also affected by those direct losses.
B.1.2 Assessing Fish Distribution and Abundance
The SFK, NFK, and UTC are relatively well-sampled streams, compared with other streams in the region,
due to Pebble Limited Partnership's (PLP's) efforts to collect environmental baseline data in areas
draining the Pebble deposit area (PLP 2011, 2018a). However, accurately and comprehensively
assessing fish distribution and abundance in stream and wetland habitats in the larger SFK, NFK, and
UTC watersheds, as well as at the mine site area, is difficult. Because the region is inaccessible by road
and subject to a challenging and variable climate, sampling occurs on intermittent site visits only during
periods when the region and its aquatic habitats are accessible and effective fish sampling is possible.
For example, fish sampling efforts were not conducted during the winter, resulting in a lack of fish
distribution and abundance information in overwintering areas. Given these logistical challenges, the
currently available data provide an incomplete description of the full seasonal distribution and
abundance of fish species and life-history stages across the region's high diversity and density of aquatic
habitats. Because habitat use by fishes is highly variable in space and time, and because all habitats in
the region have not been sampled for all species and life stages, in all seasons, over multiple years, it is
reasonable to conclude that the data provide an underestimate of the distribution and abundance of fish
species and life stages within these habitats.
1 EPA acknowledges that water resources have not been consistently mapped throughout these watersheds
(USACE 2020a: Page 4.24-8), which affects these percentage estimates. Nonetheless, the 2020 Mine Plan would
result in the permanent loss of nearly 100 miles of headwater streams.
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This likely underestimation of fish distributions is true not only of the data reported by PLP (2011,
2018a), but also of the Anadromous Waters Catalog (AWC) (Giefer and Graziano 2022) and the Alaska
Freshwater Fish Inventory (AFFI) (ADF&G 2022a). These databases do not characterize all potential
fish-bearing streams due to the large number of and lack of access to streams in Alaska. The AWC and
the AFFI are not comprehensive, meaning that not all streams have been sampled and those that have
not been sampled cannot be assumed to be non-fish bearing streams. The AWC website acknowledges
this limitation, stating that the database "...lists almost 20,000 streams, rivers, or lakes around the state
which have been specified as being important for the spawning, rearing or migration of anadromous
fish. However, based upon thorough surveys of a few drainages it is believed that this number
represents a fraction of the streams, river, and lakes actually used by anadromous species" (ADF&G
2022b). Even within the footprint of the 2020 Mine Plan, the FEIS indicates that the majority of mapped
streams have not been sampled for fish (USACE 2020: Section 4.24, Figure 4.24-1). Similarly, life stage-
specific designations in the AWC likely represent underestimates, given the challenges inherent in
surveying all streams that may support life-stage use throughout the year. These same challenges—and
thus likely underestimation of habitat use—also pertain to other aquatic habitat types (e.g., wetlands
and other off-channel habitats).
Moreover, the methods used to assess fish distribution and abundance have included several sampling
techniques, including snorkeling, electrofishing, seining, angling, and visual observation (aerial and on-
the-ground). All of these methods have limitations. Aerial surveys of spawning salmon only account for a
portion of the spawning populations, and estimates based on these surveys should be considered
minimum counts (Jones et al. 2007, Morstad et al. 2009). Many of these methods, as applied, appear to
lack quantitative estimates of capture efficiency: for example, PLP (2011) acknowledges that many of
the methods used "were not conducive to estimate catch-per-unit-effort (CPUE)" (PLP 2011: Chapter
15). As a result, estimates of abundance or density with confidence bounds cannot be derived, these
methods are most useful for estimating presence of species and life-history stages, and any estimates of
distribution and abundance derived from such methods are necessarily minimums because fish species
may use certain habitats at times of the year other than when sampling has been conducted to date.
B.1.3 Assessing Habitat Importance or Value
The importance of individual streams and wetlands is not fully captured by fish presence. Stream and
river fishes depend on the interconnected suite of watershed processes that shape physical habitat,
structure the flow of energy through the system, provide the trophic basis for growth, and regulate the
chemical, physical, and biological conditions experienced by fishes and other aquatic life. As discussed in
Section 3.2.4, headwater streams and wetlands and their associated functions are crucial contributors to
the quality of downstream waters inhabited by fishes, even if those habitats do not themselves contain
fish (Cummins and Wilzbach 2005).
Where fishes are observed in headwater streams and wetlands, density is not always a reliable indicator
of habitat quality or productive potential. PLP has undertaken a significant effort to assess fish
populations in the SFK, NFK, and UTC watersheds (PLP 2011, 2018a), and the resulting data provide
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useful baseline information. However, these data are insufficient to conclude that aquatic habitats with
no or low fish densities are unimportant for supporting and maintaining fishery resources over the
lifespan of potential impacts under the 2020 Mine Plan.
Productivity for Pacific salmon, sometimes defined as the ratio of recruits or offspring per spawner,
varies over space and time (Rogers and Schindler 2008). Based on evidence that the component
watersheds and associated marine waters yield large quantities of salmon biomass annually, the Bristol
Bay watershed—including the SFK, NFK, and UTC watersheds—is highly productive. Watersheds with a
high capacity to support salmon production will not always contain high densities of fish at all given
times and locations, for numerous reasons (Warren 1971, Van Home 1983). This may be particularly
true for anadromous salmonids and other fish species (e.g., Northern Pike) that use an array of habitats
to complete their life cycles. For these species, local abundances may be influenced by population
dynamics that occurred elsewhere, during an earlier life stage.
Salmon populations may cycle at decadal to centennial scales (Rogers et al. 2013), and locations of high
salmon productivity in the region shift in time and space (Brennan et al. 2019). Some aquatic habitats
are seasonally important: salmon may be present in high abundances at certain times of the year, and
absent at other times. Some aquatic habitats may have no or low abundances of salmon in some years,
but high abundances in other years, reflecting how populations respond to changing environmental
conditions across habitats (Section 3.3.3). This variability is illustrated by annual differences in aerial
counts of salmon spawners in the SFK, NFK, and UTC mainstems between 2004 and 2008 (PLP 2018a:
Table 3-7). Highest index spawner counts differed substantially across species and years, with no
consistent pattern across sites: for example, the maximum highest index spawner count for Chinook
Salmon occurred in 2004 in the SFK but in 2005 in the NFK (Table 3-7). These data show how variable
counts are over a 5-year period. Over longer time scales, this variability is even greater. Available data
for total inshore Sockeye Salmon runs in Bristol Bay illustrate this point. Between 2004 and 2008, the
period during which most of the fish abundance and distribution data reported in the FEIS were
collected, Bristol Bay's total inshore run of Sockeye Salmon ranged from 39.4 million to 44.8 million fish
(Tiernan et al. 2021). In 2022, the total inshore run of Sockeye Salmon was 79.0 million fish (ADF&G
2022c)—a roughly 100 percent increase from 2004 through 2008 values. This significant increase in
Bristol Bay's Sockeye Salmon runs over the past decade is not captured in the fish abundance and
distribution data used to estimate impacts in the FEIS.
These same patterns of spatial and temporal variability also apply to other fish species,
macroinvertebrates, and other components of the food web essential for ecosystem function. Given
these considerations and the spatial and temporal limitations of the available data, it is impossible to
conclude with any certainty that the aquatic habitats lost to the 2020 Mine Plan are not and would not
be important to Pacific salmon over the life of the mine and beyond.
B.1.4 Summary
PLP (2011, 2018a) presents results of the most extensive fish-sampling regime that currently has been
conducted in the SFK, NFK, and UTC watersheds. These data show that streams in these watersheds,
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including those that will be lost under the 2020 Mine Plan, provide spawning and rearing habitat for
multiple Pacific salmon species. However, limitations of the sampling regime mean that these data
provide an incomplete description of—and likely underestimate—actual seasonal fish distributions and
abundances in the region. Aquatic habitats at the mine site and in downstream mainstem reaches,
including lateral floodplain habitats, vary in importance across species and life stages, both seasonally
and annually (see Section B.2.2). Given these factors, EPA cautions against making conclusions that
certain habitats are not important based solely on the numbers of fish observed under PLP's sampling
regime. The quality of a given aquatic habitat as a fishery area does not depend solely on fish abundance
within that habitat, particularly when fish abundance is assessed infrequently and over limited time
scales. Many other factors, including the contributions that habitat makes to the quality and
maintenance of downstream reaches, determine the importance of aquatic habitat as fishery areas. It is
not valid to conclude that aquatic habitats with no or low observed fish abundances under the sampling
regime conducted to date are somehow unimportant as, or unimportant in maintaining, fishery areas.
The measure of value, importance, or significance of a given habitat includes not just the fish found there
at a specific point in time, but also the fish that have used those habitats in the past, those that will use
those habitats in the future, and the larger watershed functions to which that habitat contributes. The
headwater streams and wetlands that would be impacted by the 2020 Mine Plan are, in fact, very
important for Pacific salmon and other fishes, both directly by providing fish habitat at particular times
(i.e., in specific years or seasons, or for specific life stages) and indirectly by provisioning and regulating
downstream fish habitats (Section 3.2.4). As a result, these habitats are integral parts of their immensely
productive watersheds.
B.2 Spatial and Temporal Scales and Variability
This section examines the importance of (1) considering the spatial and temporal scales at which
potential effects of the 2020 Mine Plan on aquatic resources are evaluated, and (2) sufficiently capturing
and considering spatial and temporal variability in environmental parameters and aquatic resources
when evaluating those effects.
B.2.1 Spatial and Temporal Scales Used in Assessment of the 2020
Mine Plan
When conducting an assessment, defining and selecting appropriate spatial and temporal scales for the
analysis are essential. Assessments and models evaluate the system of inquiry at specific spatial and
temporal scales, which may be explicitly or implicitly determined. The selection of scales of inquiry is
critical, as they must be appropriate to capture biologically and ecologically meaningful patterns and
processes (Levin 1992). In evaluating potential effects of the 2020 Mine Plan on fish populations, an
appropriate spatial scale would capture the extents of adult spawning, juvenile rearing and seasonal
movement, and migration as potentially affected by changes in chemical, physical, or biological
conditions or processes at and downstream of the mine site. For mine site development and operations,
this spatial scale would include all waters under the mine footprint and extend downstream as far as
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effects could be measured or reasonably expected to have ecological consequences. For example, the
spatial scale might be determined by the downstream extent that key constituents were altered for
chemical changes and that fluvial geomorphic processes were altered for physical changes. Pacific
salmon, due to their mobile and migratory nature, use habitats across these spatial scales over the
course of their life cycles.
This selection of appropriate scale is important because assessment of whether "measurable impacts"
occur is scale dependent. For example, if an assessment considers a large-enough spatial scale, relative
to the assessed area, when evaluating impacts, the relative magnitude of those impacts will diminish as a
function of increasing scale (although the absolute magnitude of those impacts remains unchanged). If
an assessment considers a short enough temporal scale, relative to the life histories of the species
affected and the time frames over which habitat use by species and life stages vary, when evaluating
impacts, it may fail to detect what over longer time periods becomes irreparable harm to those habitats
and populations (Schindler and Hilborn 2015). Thus, assessment of effects should be conducted at
spatial and temporal scales that are most relevant to the resources being evaluated (EPA 2019).
This scale-dependence is illustrated clearly in the FEIS, which concludes that "impacts to Bristol Bay
salmon are not expected to be measurable" (USACE 2020: Page 4.24-7). This statement presupposes that
the only scale at which impacts matter is the entire Bristol Bay watershed—that is, only impacts at the
level of the entire Bristol Bay salmon population are important. Reporting conclusions about impacts at
this regional scale results in impacts appearing to be less severe, relatively. The direct loss of 99.7 miles
of streams within the initial 2020 Mine Plan footprint is reported as "...about 20 percent of available
habitat in the Headwaters Koktuli drainage [i.e., the SFK and NFK watersheds], 12 percent of available
habitat in the larger Koktuli River drainage, and 0.3 percent of available stream and river habitat in the
Nushagak watershed" (USACE 2020: Page 4.24-8). Basing conclusions on relative effects at the largest
spatial extent suggests that individual habitats and the fishes they support are similar and
interchangeable throughout the Nushagak River watershed, and evidence suggests that is not the case
(Section 3.3.3). It also does not change the fact that 99.7 miles of streams in the SFK, NFK, and UTC
watersheds would be lost under the 2020 Mine Plan footprint, an amount of loss that would be likely to
have an unacceptable adverse effect on fishery areas in these watersheds (Section 4.2.1).
Ninety-four percent of the 2020 Mine Plan's impacts to streams, wetlands, and other aquatic resources
would occur in the Koktuli River watershed. The miles of streams and acres of wetlands and other
waters that would be lost reflect local conditions and provide habitat to specific fish communities that
are part of a portfolio of local populations of multiple Pacific salmon and other fish species (Section
3.3.3). Thus, the FEIS conclusion does not disclose impacts at the smaller, more relevant and appropriate
scale where impacts would be measurable. Loss of any genetically distinct populations in the Koktuli
River watershed would constitute a measurable, adverse effect, in addition to any effects these losses
may have at the entire Bristol Bay watershed scale via the portfolio effect (Section 3.3.3).
Selection of appropriate temporal scales is also important for evaluating impacts to fishes and their
habitats. For example, the FEIS presents streamflows and estimates of streamflow change in terms of
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average monthly flows (USACE 2020: Section 4.16, Table 4.16-3). Although hydrologists consider
average monthly flows to be a meaningful measure of a stream's hydrograph, evaluating impacts of
streamflow changes at a monthly temporal scale does not address key ecological considerations relevant
to fishes. A stream's annual hydrograph can be characterized by monthly averages, the annual extremes
of low and high flows, and short-duration flow pulses (Richter et al. 1996, George et al. 2021). A stream's
hydrograph may also be characterized by components that include baseflow, frequent floods, seasonal
timing of flows, and interannual variation in flow. In all cases, the magnitude, timing, duration,
frequency, and rate of change of streamflows are important in characterizing the natural hydrograph
(Poff et al. 1997).
The life histories and behaviors of aquatic organisms are attuned to streamflow cues at different
timescales and may be affected by daily (and even sub-daily) variations in streamflow that affect
physical and ecological processes (Bevelhimer et al. 2015, Freeman et al. 2022). The use of monthly
averages without consideration of daily and interannual variation ignores impacts of predicted flow
changes on other important streamflow components. Evaluating streamflow changes using only average
monthly flows masks the severity of impacts, because percent changes in daily flows are more variable
than changes to monthly averages. This dampening of variability is clearly illustrated by comparing
average daily to average monthly flows (Figure B-l): during both low flow and high flow periods,
average monthly streamflow does not capture the range of flows that occur in the system. However,
such daily flow information is not reported or analyzed in the FEIS. Evaluating streamflow changes using
monthly averages provides only a minimum estimate of the actual streamflow changes likely to result
from the 2020 Mine Plan. The same is true for changes in water temperature, which the FEIS also
presents as monthly averages grouped by winter and summer months (USACE 2020: Section 4.24, Table
4.24-3). The FEIS acknowledges that the potential for daily temperature variations beyond the monthly
ranges exists, but states, without any supporting evidence, that the monthly ranges are representative of
potential temperature changes (USACE 2020: Section 4.24).
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of Aquatic Habitats and Fishes
Figure B-l. Average monthly versus minimum, average, and maximum daily streamflow in the North
Fork Koktuli River. Averages are based on data at site NK100A (USGS Gage #15302250), from 2004-
2015 (USGS 2022).
B.2.2 Spatial and Temporal Variability in Assessment of the 2020 Mine
Plan
Streams and rivers are dynamic, highly variable systems. Oversimplification of this variability, or failure
to account for rare, but disproportionately influential, spatial features or temporal events, can lead to
faulty conclusions. In streams and rivers, infrequent but extreme flow events (i.e., floods or droughts)
can strongly shape ecology. The timing and duration of ecologically important flow events, for example,
can be difficult to predict, but can profoundly affect both physical habitat structure and population
dynamics (Poff et al. 1997, Freeman et al. 2022). Similarly, uncommon or infrequent habitat features can
be disproportionately important. For example, shelters or refuges from environmental conditions that
may be briefly limiting can serve as "bottlenecks," constraining the abundance of future life stages; for
Pacific salmon, critical "bottleneck" habitats can include off-channel habitats and beaver ponds (Pollock
et al. 2004).
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To fully consider this variability in an assessment of potential impacts, all components of these aquatic
systems (i.e., chemical, physical, and biological) should be sampled over spatial and temporal extents
that capture the full range of variability in each component. In addition, connectivity between headwater
streams and wetlands and downstream waters is dynamic, shifting on both short-term and long-term
time frames in response to changing environmental conditions (Fritz et al. 2018). A complete accounting
of how headwaters affect downstream waters should consider aggregate physical, chemical, and
biological connections over multiple years to decades (Fritz et al. 2018, Schofield et al. 2018).
A significant amount of baseline environmental data has been collected in the SFK, NFK, and UTC
watersheds, primarily between 2004 and 2008 (PLP 2011, 2018a). These data demonstrate the natural
variability of these systems, in terms of biological communities, streamflow, water chemistry, and
myriad other factors, across both sites and sampling dates (e.g., see discussion of adult salmon spawner
counts in Section B.1.3). There is no reason to expect that these data, primarily collected over a 5-year
period nearly 15 years ago, fully capture how much these factors vary over longer time scales and more
finely resolved spatial scales. The nearly 100 percent increase in Bristol Bay's total inshore Sockeye
Salmon run in 2022 (ADF&G 2022c), relative to runs between 2004 and 2008 (Tiernan et al. 2021),
provides just one example of the variability in environmental conditions that has not been captured in
the FEIS and, thus, not considered in its evaluation of impacts of the 2020 Mine Plan.
Streamflow data provide another illustration of this point. Accurate quantification of streamflow metrics
requires data collected over sufficient areas and time periods to account for spatial and temporal
variability (George et al. 2021). Multiple studies have shown that streamflow data collected over a
limited number of years are associated with high levels of uncertainty (Kennard et al. 2010, Goguen et al.
2020). For example, Goguen et al. (2020) evaluated the variability of flow metrics calculated with data
collected over different time periods. They found that uncertainty or variability (measured as coefficient
of variation) in monthly flow metrics was 30 percent when metrics were calculated over 5 years but
decreased rapidly when metrics were calculated over 15 or more years (Goguen et al. 2020).
The high natural variability of these systems also makes FEIS claims that impacts of the 2020 Mine Plan
would not be significant because they "would be expected to fall within the range of natural variability"
(e.g., USACE 2020: Page 4.24-46) meaningless. This is easily illustrated by considering streamflow
variability in Figure B-l. Between 2004 and 2015, average daily streamflow at NK100A, the
downstream-most site on the NFK mainstem considered in the FEIS, ranged from roughly 0 to 3,000 cfs;
in May alone, average daily streamflow ranged from 40 to more than 2,000 cfs (Figure B-l). Streamflow
changes that occur within this range of "natural variability" could still have significant impacts on
aquatic resources if they are occurring more or less frequently than under natural, undisturbed
conditions.
Like streamflow, fish populations can be highly dynamic in time and space, limiting the ability of short-
term, spatially unbalanced sampling designs to adequately characterize population dynamics that may
be important for long-term persistence (Davis and Schindler 2021). The baseline data on fish abundance
and distribution used in the FEIS were primarily collected between 2004 and 2008, and many sites were
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not sampled in multiple seasons across multiple years; thus, data were not collected over sufficient
spatial and temporal scales to fully characterize the bounds of the natural spatial and temporal
variability of fish populations in the region, for all species and life stages, to adequately support the FEIS
conclusions about impacts to fishes. Based on 57 years of continuous monitoring data, Davis and
Schindler (2021) conclude that long-term assessments are needed to fully understand the contributions
of individual populations. The FEIS assessment of fish abundance and habitat use relies on data collected
over a much shorter time period. As a result, FEIS conclusions about the long-term impacts on aquatic
resources resulting from the 2020 Mine Plan based on these data should be viewed as minimum
estimates—and, as detailed in Section 4.2, even these minimum estimates constitute an unacceptable
adverse effect on fishery areas.
B.3 FEIS Assessment of Streamflow Changes
The models and methods used in the FEIS to estimate streamflow changes in the SFK, NFK, and UTC
watersheds associated with the 2020 Mine Plan have several shortcomings. This section summarizes the
FEIS conclusions regarding streamflow and identifies several issues with those conclusions or the
underlying methods, many of which EPA expressed throughout the EIS development process (e.g., EPA
2019).
The FEIS presents impacts of the 2020 Mine Plan that were estimated using an end-of-mine watershed
model that incorporated inputs from three primary components: a baseline watershed model, a
groundwater flow model, and a mine-site water-balance model (PLP 2019a: RFI 109g). Streamflow
changes are reported in terms of changes in average monthly streamflow between baseline (i.e., under
natural conditions) and end-of-mine, assuming discharge of treated water in an "average climate year"
(i.e., at a 50-percent exceedance probability), based on 76 synthetic monthly average flows (USACE
2020: Section 4.16 and Appendix K4.16) calculated from runoff estimates derived from long-term
precipitation and temperature data at a site roughly 17 miles from the mine site. The FEIS states that
water would be strategically discharged from wastewater treatment plants (WTPs) to benefit a priority
fish species (Chinook Salmon, Coho Salmon Sockeye Salmon, Rainbow Trout, or Arctic Grayling) and life
stage (spawning or juvenile rearing) selected for each month in each watershed (USACE 2020: Table
4.24-2).
As detailed in Section 4.2.4, downstream flow changes associated with the 2020 Mine Plan, as reported
in the FEIS (USACE 2020: Section 4.16), would exceed 20 percent of average monthly flows in at least 29
miles of documented anadromous fish streams. Reaches of the SFK and NFK closest to the mine site
would experience greater changes in average monthly streamflow than reaches farther downstream
(USACE 2020: Section 4.16). NFK Tributary 1.190 would be dewatered entirely—that is, experience a
100-percent loss of flow—due to construction of the bulk tailings storage facility and seepage-collection
system (USACE 2020: Section 4.16). SFK Tributary 1.190 is predicted to experience a maximum change
in average monthly flow of 19 percent during operations, whereas SFK Tributary 1.24 is predicted to
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experience a maximum change of 98 percent (USACE 2020: Section 4.16). A total of 9.2 miles of
anadromous habitat have been documented within these two SFK tributaries.
Significant streamflow alterations also would extend down the NFK and SFK mainstems. For example,
NFK Reaches A, B, and C would experience a greater than 20-percent increase in streamflow during
April; NFK Reach C could see a 105-percent increase in April and a 20-percent decrease in June. These
alterations are predicted to occur despite attempts to "optimize" the discharge of treated water to
benefit priority fish species and life stages. SFK Reach E would see a 52-percent decrease in average
monthly streamflow in April, whereas SFK Reach D would see a 109-percent increase (USACE 2020:
Table 4.16-3) due to WTP discharges. According to the FEIS, the extent of impacts on streamflow could
extend to just below the confluence of the SFK and NFK (USACE 2020: Page 4.16-2),2 meaning that up to
61 miles of the SFK and NFK mainstems could experience "discernible" streamflow alterations. This
level of change from natural streamflows represents an unacceptable adverse effect on fishery areas in
the SFK and NFK watersheds (Section 4.2.4).
Despite the importance of natural flow regimes as a "master variable" determining the structure and
function of stream and river ecosystems (Bunn and Arthington 2002, Lytle and Poff 2004, Poff and
Zimmerman 2010, Sofi et al. 2020, Tonkin et al. 2021), the FEIS fails to evaluate the myriad ways that
anticipated streamflow changes would affect these systems. The FEIS also likely underestimates the
actual extent to which streamflow in the SFK, NFK, and UTC watersheds would be affected by mine
operations resulting from the 2020 Mine Plan, in terms of percentage change in streamflow, length of
affected streams, and changes in streamflow variability. This underestimation of streamflow changes in
the FEIS results from several issues.
The following sections highlight three specific areas of concern in the FEIS assessment of streamflow
changes: the failure to consider ecological impacts of streamflow changes; the use of average monthly
streamflows to assess impacts; and the failure to sufficiently consider interactions between surface
waters and groundwater.
B.3.1 Impacts of Streamflow Changes
The natural flow regime is a critical component of streams and rivers and their hydrologically connected
aquatic habitats because water flow directly or indirectly affects all other physical, chemical, and
biological components of these systems (Bunn and Arthington 2002, Lytle and Poff 2004, Poff and
Zimmerman 2010, Sofi et al. 2020, Tonkin et al. 2021). The body of published scientific literature on the
functional consequences of hydrograph alteration is extensive (e.g., Poff et al. 1997, Tonkin et al. 2021,
Freeman et al. 2022). Despite its importance, the FEIS does not address the numerous effects of
predicted flow changes directly. There is no explanation of how streamflow changes associated with the
2020 Mine Plan would affect natural flow patterns and variability, nor consideration of how these
2 The FEIS indicates streamflow in the UTC and the Koktuli River below the confluence of the NFK and SFK would
notbe negatively impacted by the project (USACE 2020: Section 4.24).
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changes would alter physical habitat, water quality, and the full suite of organisms adapted to natural
flows in these systems (Section B.5.2).
The FEIS instead uses estimates of streamflow change solely to inform its fish habitat modeling,
presenting summaries of monthly changes to "suitable fish habitat" as defined in the PHABSIM model
(Section B.4). Flow changes that alter monthly averages by more than 100 percent are viewed only
through the lens of the PHABSIM model and are predicted to increase available habitat, notwithstanding
the elimination of nearly 100 miles of streams and the myriad effects the loss of these flows and their
ecological subsidies would have on downstream reaches. There is no distinction made in the FEIS
between flows that create and maintain habitat (e.g., channel-maintenance flows) and those that affect
habitat utilization. As a result, the FEIS presents an extremely simplified assessment of how streamflow
changes will affect mainstem and tributary reaches of the SFK, NFK, and UTC watersheds. As detailed in
Section 4.2.4, even this simplified assessment shows that streamflow alterations associated with the
2020 Mine Plan would constitute an unacceptable adverse effect on fishery areas, and the actual
ecological impact of these changes would likely be more extensive than estimated in the FEIS.
Furthermore, stream lengths in which flow regimes would be significantly altered from natural
conditions are not quantified or discussed in the FEIS. The FEIS states that flow changes may extend to
reaches just below the confluence of the SFK and NFK mainstems (USACE 2020: Page 4.16-2), but the
FEIS does not mention that there are 61 miles combined in the SFK and NFK mainstems before reaching
that confluence. Additionally, the distance between locations at which streamflow information was
collected and modeled limits the ability to accurately predict the extent of streamflow impacts. For
example, WTP discharges to Frying Pan Lake would increase outflows to the SFK up to 109 percent
above average monthly flows. However, it is unclear how far downstream these flow increases would
extend because the next downstream gage at which streamflow information was estimated (i.e., SFK
Reach C) is located 11.7 river miles downstream. At that point, streamflow changes were estimated at
less than 5 percent below baseline average monthly flow (USACE 2020: Table 4.16-3).3 The actual extent
of streamflow changes in the SFK most likely extends some distance downstream of Frying Pan Lake, but
the FEIS does not provide an estimate of that distance.
B.3.2 Use of Average Monthly Flows and Climate Conditions
The FEIS presents streamflows and estimates of streamflow change in terms of average monthly flows
(USACE 2020: Section 4.16, Table 4.16-3). Percentage flow differences between baseline and end-of-
mine conditions are computed based on monthly averages, which as discussed below provide a
relatively coarse measure of potential impacts to fishes and other aquatic resources. Even at this coarse
level of assessment, greater than 20 percent changes in average monthly flows are predicted during at
least 1 month per year in at least 29 miles of documented anadromous fish streams.
3 The next downstream location for which streamflow data are presented in FEIS Table 4.16-3 is SFK Reach C,
which is based on streamflow atgage SK100C (PLP 2019b: RFI 109f), 11.7 river miles (18.9 km) downstream of
SK100F (PLP 2020d: RFI 161).
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In reality, the use of average monthly flows to evaluate impacts of the 2020 Mine Plan likely
underestimates downstream flow changes that would have meaningful ecological effects. Average
monthly flows do not capture ecologically important aspects of the natural hydrograph (Section B.2) or
represent the full magnitude of potential daily flow fluctuations. As a result, the use of monthly averages
downplays the extent of impacts on the natural hydrograph and the aquatic life that is adapted to and
relies on it. Fish do not experience average monthly flows; rather, they experience the dynamic
continuum of flows occurring over much shorter time periods (i.e., daily or even sub-daily flows). As
discussed in Section B.2.1, evaluation of streamflow changes using only average monthly flows masks
the severity of impacts, because percent changes in average monthly flows are less variable than
changes in daily flows (Figure B-l). If average monthly streamflows differ from baseline conditions,
aquatic resources are likely to be altered; if average monthly streamflows do not differ from baseline
conditions, it does not necessarily mean that streamflow patterns on shorter time scales—and, thus,
aquatic resources—will not be affected.
In the FEIS analysis of streamflow changes, WTP discharges would be preplanned for each month based
on modeling and a set of assumptions. Monthly WTP discharges would be the amount needed to
"optimize" downstream habitat for specific anadromous fish species and life stages assuming that the
historic monthly average streamflow was to occur (i.e., given an "average climatic year," or 50 percent
exceedance probability). However, the only monitoring proposed by PLP appears to be quarterly
streamflow and fish presence surveys (PLP 2019c: RFI135), indicating that water discharges were
never proposed to be altered in response to current climatic conditions. Managing water discharges
based on average long-term streamflows would dampen variability in the system (Section B.2.2). The
proposed discharges would transform the naturally varying and unregulated surface water and
groundwater flows in the headwaters into uniform, regulated process-water discharges to surface
waters. The loss of this streamflow variability, which is critical to the structure and function of these
ecosystems (Poff et al. 1997, Bunn and Arthington 2002, Freeman et al. 2022), is not described or
characterized in the FEIS.
Despite these shortcomings, the streamflow change estimates documented in the FEIS provide a
reasonable minimum approximation of the streamflow impacts expected to result from the 2020 Mine
Plan. Even these minimum estimates of changes in average monthly flows, over the stream lengths
documented in the FEIS, would affect the physical, chemical, and biological characteristics of these
streams and constitute an unacceptable adverse effect on fishery areas.
B.3.3 Interactions between Groundwater and Surface Waters
As discussed in Section 3.2.1, surface waters and groundwater in the SFK, NFK, and UTC watersheds are
highly connected and interact in complex ways (USACE 2020: Section 3.17). These interactions influence
streamflow patterns—and thus aquatic resources—in both space and time. The FEIS provides limited
characterization or simulation of the coupled surface water-groundwater interactions critical to
maintaining the region's aquatic ecosystems (Wobus and Prucha 2020). As a result, the FEIS
underestimates the extent of groundwater impacts likely to occur under the 2020 Mine Plan and, thus,
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potential effects on downstream flows. Examples of the failure of the FEIS to adequately consider
groundwater impacts and interactions with surface waters are included below.
• The baseline watershed model and the groundwater flow model used to assess streamflow changes
were not integrated, and instead they were developed and operated independently (Wobus and
Prucha 2020). The baseline watershed model was configured and calibrated prior to development of
the refined groundwater model (MODFLOW). Together, these points indicate that estimates of
streamflow change in the FEIS did not represent a comprehensive, integrated assessment of how
changes in both surface waters and groundwater would affect streamflows under the 2020 Mine
Plan.
• A review of the model calibration shows the groundwater model overestimates groundwater
elevation in the NFK headwaters area and underestimates NFK streamflow downstream of the
headwaters, which may be an indication of poor model calibration (PLP 2019d: RFI 109d).
MODFLOW simulations resulted in groundwater elevations that were up to 35 feet deeper than
observed water table elevations (e.g., Figure 6-10 in PLP [2019d]), suggesting poor model
calibration and the need to expand the alluvial aquifer in the headwaters of the NFK to properly
account for groundwater and surface water observations.
• Within and across the mine site boundary, streamflow changes due to well pumping and
groundwater table depression were not well characterized. Streamflow losses during mine
operation were only characterized by conditions at the end-of-mine (e.g., 20 years). Changes in
shallow groundwater conditions and associated stream losses within and across the mine site
boundary were not rigorously accounted for when estimating streamflow impacts, as indicated by
the significant differences between MODFLOW's simulated groundwater elevations and observed
groundwater elevations (discussed above). Impacts on gaining reaches downstream of the mine,
attributed to groundwater sources under pre-mine conditions in the FEIS, were not considered.
• The majority of surface water and groundwater flows within the mine site boundary were assumed
to be captured, contained, and released via WTP discharge to surface waters. There was no
assessment of impacts associated with the loss of groundwater recharge at the mine site, which
provides baseflow contributions to discharge under low flow conditions (including under surficial
ice) and stabilizes water temperatures under low and transitional flow conditions.
As these examples illustrate, the FEIS likely underestimates the impacts of groundwater pumping and
processing demands, the extent of groundwater drawdown both within and across watersheds, and,
thus, the influence these groundwater-related factors would have on downstream flow changes
associated with the 2020 Mine Plan.
B.4 FEIS Assessment of Fish Habitat Changes
Assessment of streamflow and fish habitat changes under the 2020 Mine Plan are closely related, given
the fish habitat assessment methods used in the FEIS. This section considers potential issues associated
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with how the FEIS evaluated fish habitat changes and how those issues affect conclusions about impacts
of the 2020 Mine Plan. The issues raised here do not affect EPA's conclusion that the habitat losses (i.e.,
losses of anadromous fish streams, additional streams, and wetlands and other waters) or streamflow
changes predicted to occur under the 2020 Mine Plan each constitute an unacceptable adverse effect on
fishery areas. Rather, these issues highlight concerns that the FEIS evaluation of fish habitat changes did
not represent an accurate and thorough assessment of likely impacts.
B.4.1 Overview of Fish Habitat Assessment Methods
The FEIS relied on the PHABSIM modeling approach, which is part of the Instream Flow Incremental
Methodology developed by the U.S. Fish and Wildlife Service (Bovee et al. 1998) to model changes in fish
habitat in response to changes in streamflow. In the FEIS fish habitat analysis, PHABSIM was used to
predict effects of streamflow changes on the amount of available habitat for multiple fish species and life
stages. There are two basic components of a PHABSIM model: (1) the hydraulic representation of the
stream at a stream transect; and (2) the habitat simulations at a stream transect using defined hydraulic
parameters (i.e., water depth and velocity and, for some life stages, substrate). Habitat suitability curves
(HSCs) for different fish species and life stages are used to calculate weighted usable habitat area for a
stream segment represented by the transect.
In addition, the HABSYN program developed by R2 Resource Consultants was used to expand the
standard transect-based component of PHABSIM to unsampled habitat areas (USACE 2020: Appendix
K4.24, PLP 2018b: RFI 048). To EPA's knowledge, the HABSYN model has never been validated or
documented in the scientific literature. The basic premise of extending sampled transect data to
unsampled habitats was not evaluated, but was assumed in the FEIS to be valid for assessing fish habitat
in unsampled areas.
Together, PHABSIM and HABSYN models were used to estimate total acres of fish habitat—by species,
life stage, and reach—for wet, average, and dry climate conditions during pre-mine (baseline), end-of-
mine, and post-closure phases of mine development. The following sections focus on potential issues
associated with the modeling of fish habitat changes under the 2020 Mine Plan, as reported in the FEIS
(USACE 2020: Section 4.24, Appendix K4.24). Many of these issues were previously identified in EPA
(2019) and NMFS (2020).
B.4.2 Use of PHABSIM Models to Estimate Fish Habitat Changes
PHABSIM is a one-dimensional physical model that has been used for decades to model habitat and
manage streamflows for fish populations, including salmon. Because PHABSIM is a method that does not
have a direct relationship to fish population biology (Waddle 2001), it has several limitations that have
long been acknowledged (e.g., Anderson et al. 2006, Railsback 2016) and should be addressed during
application and considered in interpreting results when PHABSIM is used. The FEIS did not consider
many of these issues in its fish habitat analysis; as a result, its estimates of changes to fish habitat
resulting from the 2020 Mine Plan likely underestimate the extent of those changes. This section
explores specific assumptions and limitations of how PHABSIM models were implemented in the FEIS
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(USACE 2020: Section 4.24, Appendix K4.24), as well as factors that were omitted from fish habitat
analyses.
B.4.2.1 Assumption that Streamfiow Equals Fish Habitat
The FEIS bases its conclusions about changes in the availability of fish habitat under the 2020 Mine Plan
on PHABSIM modeling (USACE 2020: Section 4.24, Appendix K4.24), which, as implemented in the FEIS,
assumes that water depth and velocity are the only determinants of fish habitat. This assumption cannot
defensibly be made unless (1) field data and analysis show that water depth and velocity are related to
fish habitat in the region, and (2) there is a comprehensive evaluation of the other factors determining
fish habitat that would potentially be affected by the 2020 Mine Plan.
Importantly, the FEIS and its supporting documents did not establish that relationships between
discharge (water depth and velocity) and fish habitat exist in the SFK, NFK, and UTC. This is of particular
concern because these watersheds are groundwater-driven systems. When the assumption that habitat
use primarily is structured by surface water hydraulics is not valid, hydraulic habitat modeling methods
such as PHABSIM are not appropriate (Waddle 2001). Field data demonstrate that fish occurrence in
areas of differing water depths and velocities changed with streamfiow and over time (PLP 2011:
Appendix 15.1C)—that is, a consistent relationship between water depth and velocity and fish habitat
use was not observed. These data demonstrate variability in fish habitat use among survey years, an
indication that the underlying PHABSIM assumptions are not valid.
The PHABSIM model used in the FEIS incorrectly assumed that habitat can be reduced to discharge.
Even if this assumption were valid—as discussed above, it was not—the PHABSIM analysis also failed to
account for or consider other ecologically relevant fish habitat parameters, such as groundwater
exchange, substrate, water temperature, water chemistry, cover, and habitat complexity (e.g., wetlands
and other off-channel habitats). While water depth and velocity are important determinants of fish
habitat, they are only two variables interacting with a suite of other factors that determine overall fish
habitat suitability.
PHABSIM models are not appropriate as the sole means to evaluate habitat for fish species that key into
specific habitat variables unrelated to water depth and velocity. For example, the SFK, NFK, and UTC
watersheds experience complex interactions between surface water and groundwater, with
repercussions for fish habitat. Spawning Sockeye Salmon (Oncorhyrtchus nerka) and Coho Salmon (O.
kisutch) select habitats based on groundwater upwelling and downwelling, respectively. Changes in
these habitat determinants were not reflected in the PHABSIM analysis; in general, the utility of
PHABSIM approaches may be extremely limited in areas such as the SFK, NFK, and UTC watersheds,
with extensive and complex surface water-groundwater interactions (NMFS 2020).
In addition, the PHABSIM analysis did not consider how disruption of surface water flows, groundwater
pathways, and aquifer characteristics would alter water temperatures and thermal patterns within the
SFK, NFK, and UTC watersheds. The alteration of water temperatures is a concern because fishes are at
risk from disruption of the heterogeneity and spatial distribution of thermal patterns, which drive their
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metabolic energetics. Fish populations rely on groundwater-surface water connectivity, which has a
strong influence on stream thermal regimes throughout the Nushagak and Kvichak River watersheds
and provides a moderating influence against both summer and winter temperature extremes (Woody
and Higman 2011). Coho Salmon may move considerable distances over short time periods in response
to food resources and temperature to enhance growth and survival (Armstrong et al. 2013). The
PHABSIM analysis also does not account for the benefits of complex stream features resulting from off-
channel habitats (e.g., side channels, sloughs) or other habitats, such as islands or tributary junctions.
These can be important features for fish populations: for example, tributary junctions are biological
hotspots, and off-channel habitats are often the most important factors in salmonid distribution (e.g.,
Swales and Levings 1989, Benda et al. 2004).
By considering only water depth and velocity, the one-dimensional PHABSIM analysis simplifies and
homogenizes the complexity of fish habitat into combinations of only water depth and velocity. This
simplified approach provides only a coarse assessment of suitable fish habitat and predicted impacts
resulting from the 2020 Mine Plan. As a result, this approach likely underestimates actual changes to
fish habitat that would be likely to result from changes to the full suite of variables determining
available fish habitat.
B.4.2.2 Data Collection Issues
The approach taken to develop valid fish-habitat associations typically involves mapping defined,
representative, hierarchical habitats; conducting fish surveys at sites both used and unused by fish
across the full seasonal distribution (i.e., spring, summer, fall, and winter) of all fish species and life
stages (including incubation, emergence, and fry); and then selecting study sites for analysis (e.g.,
Rosenfeld 2003). Data collection efforts to support fish habitat modeling in the FEIS did not follow this
approach and do not appear to be structured or consistently implemented to inform the PHABSIM
model in a meaningful way. As a result, there are several issues of concern regarding the data used in the
fish habitat analysis, in terms of both data-collection methods and data completeness; some examples
are discussed below.
Additional environmental baseline data relevant to fish habitat use were collected, but these data were
not used in the habitat impact analysis. Data on off-channel habitats are reported in PLP (2011, 2018a)
(see Table 3-10) but were not used in analyses related to fish habitat. The SFK, NFK, and UTC were
modeled as single-channel systems in the PHABSIM analysis, despite the frequent occurrence of riparian
wetland complexes, floodplains, beaver ponds, and other off-channel habitats throughout the area
(Table 3-10; PLP 2011, 2018: Chapter 15). For example, up to 70 percent of the mainstem SFK
downstream of Frying Pan Lake appears to be bordered by off-channel habitats (USACE 2020: Section
3.24). This complexity is not captured in the instream habitat classification, despite its prevalence and
importance for different life stages of salmon (especially Coho Salmon) and other fish species.
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B.4.2.3 Habitat Suitability Curves
Biology is attempted to be incorporated into PHABSIM through the use of HSCs. The underlying premise
of HSCs is that more fish will occur in more suitable habitats; thus, HSCs look at occurrence of a given
fish species and life stage relative to a single habitat variable (e.g., water depth or velocity) (Naman et al.
2020). Generally speaking, the univariate nature of HSCs greatly oversimplifies the concept of habitat
suitability for fishes (Section B.4.2.1). In addition, HSCs developed for evaluation of fish habitat impacts
resulting from the 2020 Mine Plan do not reflect field data collected at the mine site (Figure B-2). PLP
(2011: Appendix 15.1C) reported that the HSCs generally track the shape of the normalized observed
data histograms, with the exception of maximum depth. However, they concluded that maximum depth
is not a limiting factor for fish habitat use; thus, HSCs used in the fish habitat analysis do not include a
descending limb for depth (Figure B-2). This is an indication that appropriate steps described by
developers of PHABSIM and HSCs (Bovee 1986) were not taken to validate the ecological relevance of
depth before applying a model that forces a relationship with depth.
The HSCs assume that more water means better fish habitat, and that fish will use deeper water if it is
available. This assumption is problematic as applied in the FEIS, given that the field data actually
demonstrate decreased habitat use by juvenile Coho, Sockeye, and Chinook (0. tshawytscha) salmon
with increasing depth (Figure B-2). For example, Figure B-2 shows that as water depth increased above
approximately 2.1 ft, the probability that juvenile Coho and Chinook salmon would be found decreased,
with no juveniles of either species found at water depths above roughly 3.7 ft.
Railsback (2016) considers univariate HSCs obsolete and suggests that they introduce considerable
error to habitat modeling. Modern multivariate resource selection models or HSCs based on
bioenergetic models (which relate habitat conditions to net energy gain by fishes) can address some of
these limitations and provide a better fit to observed fish habitat-use data (Naman et al. 2019, Naman et
al. 2020). Particularly for drift-feeding fishes like salmonids, univariate HSCs may introduce systematic
bias related to factors such as density-dependent territoriality and failure to consider water-velocity
effects on prey availability (Rosenfeld and Naman 2021).
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Figure B-2. Sample habitat suitability curves used in the PHABSIM fish habitat modeling. Models
are for juvenile Coho, Chinook, and Sockeye salmon and water depth. From PLP 2011: Appendix
15.1C.
Coho Salmon Juvenile Depth: All Basins
¦ R2(n*136) ¦^¦HDR (n=85) "i Combined (n*221) Suitability
Chinook Salmon Juvenile Depth: All Basins
I R2 (n=45) !^«HDR(ns46) Combined (n=91) —Suitability
1.1 1.7
2.3 23 3.S 4.1 4.7
Depth (ft)
0.5 1.1 1.7 2.3 23 3.S 4.1
Depth (ft)
Sockeye Salmon Juvenile Depth: All Basins
R2 (n«4) ¦¦HDR(n=15) Combined (n* 19) Suitability
1.0
z
V 08
3-1
£ 5 0.6
"¦ -9
I £ <>•<
n *
i 02
o
Z 0.0
0.5
1.1
1.7
2.3
2.9
3 S 4.1
4.7
Depth (ft)
In addition, HSCs were not developed (or not included in the PHABSIM analysis) for all relevant life
stages. For example, the fry life stage (salmonids less than 50 mm) was not included in the PHABSIM
analysis; according to RFI147, they were excluded because they occupy low velocity areas with cover
and the "habitat needs of fry are generally met with flows much lower than those for other life stages"
(PLP 2019e: RFI 147). This document also states that fry habitat generally is not limiting, although no
support for this statement is provided (PLP 2019e: RFI 147). Hardy et al. (2006) discuss the importance
of evaluating fry response to streamflow changes and present an approach for evaluating fry habitat
availability. No HSCs were developed for the egg-incubation stage; in fact, impacts to the egg incubation
stage were not considered in any assessment of impacts resulting from the 2020 Mine Plan. Early
salmonid life stages (i.e., eggs and alevins) are particularly susceptible to adverse effects associated with
changes in flow (Warren et al. 2015). Potential impacts to these life stages include scouring of redds and
egg mortality with increased streamflows, freezing and desiccation with decreased streamflows, and
loss of water-temperature buffering, waste removal, and aeration during the incubation stage due to
changes in groundwater exchange. These early developmental stages are also when imprinting to natal
waters begins; flow changes that alter the physical and chemical signatures of the water during these
stages may impair imprinting and, thus, adult homing capabilities. Failure to evaluate impacts of the
2020 Mine Plan on these important life stages represents a significant omission in the FEIS.
Recommended Determination
B-20
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B.4.3 Results and Conclusions of PHABSIM Modeling Related to Fish
Habitat
The PHABSIM models used in the FEIS provide an oversimplification of fish habitat changes under the
2020 Mine Plan that does not account for the inherent complexity of aquatic habitats in the SFK, NFK,
and UTC watersheds. As a result, the magnitude of fish habitat changes identified in the FEIS likely is an
underestimate of actual effects of the project. However, even this underestimate represents an
unacceptable adverse effect on fishery areas in the SFK and NFK watersheds (Section 4.2).
Examples of specific issues related to FEIS conclusions about fish habitat changes associated with the
2020 Mine Plan are provided below.
• Based on PHABSIM flow modeling, Figure K4.24.1 (USACE 2020: Appendix K4.24) depicts that most
habitat units would not decrease under the 2020 Mine Plan. Because this figure only includes
information about mainstem channels and omits tributaries and off-channel habitats, it does not
present a complete depiction of potential effects. Exclusion of these non-mainstem habitats—which
are critical habitats for many fish species and life stages—from estimates of fish habitat changes
under 2020 Mine Plan results in a significant underestimate of impacts.
• As detailed in Section B.3, adjacent mainstem reaches of the SFK are predicted to experience both
large decreases (52 percent) and increases (110 percent) in average monthly streamflows in April.
The FEIS did not assess changes to suitable fish habitat in these SFK reaches, despite their
documented use by juvenile salmon. The portion of SFK Reach E above Frying Pan Lake (and stream
gage SK100G) is specified as rearing habitat for Coho Salmon; Frying Pan Lake and portions of the
SFK down to stream gage SK100F are used for rearing by both Coho and Sockeye salmon (USACE
2020: Section 3.24, Giefer and Graziano 2022).
• The FEIS states that treated discharges would be "optimized to benefit priority species and life
stages for each month and stream" (USACE 2020: Section 4.24, Table 4.24-2). Specific details about
how discharges would be managed and monitored are not provided, and EPA has concerns that the
goal of habitat optimization would not come to fruition. These concerns are due in part to
limitations of the flow-habitat model development and application, in addition to limitations of the
planned streamflow monitoring program. The Monitoring Summary provided by PLP states that
monitoring of surface-water flow and quality is proposed to be conducted downstream of water-
discharge points on a quarterly basis and would focus on streamflow and fish presence surveys (PLP
2019e: RFI135). Because streamflow monitoring is not described as being used for real-time WTP
discharge decisions, the optimization approach appears to be pre-planned, based on numerous
assumptions that would not reflect the natural hydrologic regime. The FEIS does not indicate that
adaptive management would be applied to ensure that habitat optimization is achieved or consider
how differences across species and life stages would result in adverse effects for species other than
each month's priority species and life stage.
These and other issues support the contention that application of the PHABSIM flow-routing model to
evaluate fish habitat changes under the 2020 Mine Plan is flawed for two key reasons: (1) it does not
Recommended Determination
B-21
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consider habitat complexity, which is a critical component of the extremely complex aquatic system that
exists in the SFK, NFK, and UTC watersheds; and (2) it does not integrate losses resulting from critical
habitat components other than water depth and velocity, such as water temperature, groundwater
interactions, and off-channel habitats. Cumulatively, the results of the analysis thus underestimate the
project effects and its consequences for fish and fish habitat.
B.4.4 Summary
The fish habitat assessment included in the FEIS relies heavily on the PHABSIM modeling approach.
Because the PHABSIM model only considers water depth and velocity and does not account for complex
interactions between surface waters and groundwater, the FEIS necessarily provides an overly
simplistic characterization of fish habitat. EPA (2019) and NMFS (2020) highlighted the value of
conducting a comprehensive analysis of the suite of environmental drivers associated with distributions
and abundances of the fish species and life stages found throughout the SFK, NFK, and UTC watersheds.
The FEIS acknowledges that PHABSIM does not account for other factors affecting fish habitat and
ultimately fish survival and that losses of headwater streams and wetlands and changes to streamflows,
groundwater inputs, water chemistry, and water temperature would occur under the 2020 Mine Plan
(USACE 2020: Appendix K4.24)—all of which are likely to affect fish habitat use, as well as other
components of these aquatic resources. However, the integrated effect that these changes are predicted
to have on fish habitat was not assessed adequately to conclude in the FEIS that there will be no effects
on fish habitat, abundance, and productivity. The FEIS likely underestimates both direct and indirect
effects on fish habitat under the 2020 Mine Plan, and its conclusion of no "measurable impact" on fish
populations is not supported by the evidence, particularly at spatial scales relevant to the 2020 Mine
Plan (i.e., the SFK, NFK, and UTC watersheds; see Section B.2.1). Even the underestimate of fish habitat
changes resulting from the 2020 Mine Plan documented in the FEIS represents unacceptable adverse
effect on fishery areas in the SFK and NFK watersheds (Section 4.2).
B.5 Other Effects on Aquatic Resources
The prohibition and restriction included in this recommended determination focus on direct losses of
aquatic habitats and losses of the ecological subsidies that these habitats provide to downstream waters
(Sections 4.2.1 through 4.2.3), as well as additional secondary effects caused by streamflow alterations
(Section 4.2.4). These impacts, as evaluated in the FEIS, would result in unacceptable adverse effects on
fishery areas in the SFK, NFK, and UTC watersheds and are the basis for the proposed prohibition and
restriction detailed in Section 5. However, the impacts underpinning this prohibition and restriction are
only a subset of the many ecological effects likely to result from implementation of the 2020 Mine Plan.
This section considers other key impacts that development of the 2020 Mine Plan would have on aquatic
habitats and fish populations in the SFK, NFK, and UTC.
Recommended Determination g 22 December 2022
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B.5.1 Water Quality Effects
The FEIS states that adaptive management strategies would be employed at the WTPs to address water
quality issues prior to discharging to the environment, including adding further treatment, as needed
(USACE 2020: Section 4.18). However, the FEIS also acknowledges that "over the life of the mine, it is
possible that [Alaska Pollutant Discharge Elimination System] permit conditions may be exceeded for
various reasons (e.g., treatment process upset, record-keeping errors) as has happened at other Alaska
mines" (USACE 2020: Page 4.18-13). It is likely that the predicted water quality of effluents is overly
optimistic (Sobolewski 2020), further suggesting that water quality impacts are underestimated in the
FEIS.
Despite acknowledgement of the potential for water quality exceedances, Section 4.24 of the FEIS states
that treated water discharges are expected to result in "no noticeable changes" in water chemistry and
only slight increases in water temperature immediately below discharge points (USACE 2020). This
misrepresents the information presented in the FEIS, which indicates that treated water discharges
would substantially increase concentrations of 11 constituents (e.g., chloride, sulfate, calcium,
magnesium, sodium, nitrate-N, ammonia, hardness) in receiving waters relative to baseline
concentrations (USACE 2020: Section 4.18). For example, chloride loads in the NFK are predicted to
increase by 1,620 percent (USACE 2020: Page 4.18-19); nitrate-nitrite and ammonia are predicted to be
30 times and 12 times higher than baseline concentrations, respectively (USACE 2020: Tables K3.18-7
and K4.18-13); total dissolved solids are predicted to be more than three times higher than baseline
concentrations in UTC, and approximately 12 times higher than baseline concentrations in the NFK
(USACE 2020: Tables K3.18-7, K3.18-9, and K4.18-13).
Section 4.18 of the FEIS does not identify environmental consequences from these predicted changes in
water chemistry, and Section 4.24 of the FEIS suggests that there would be no impacts to fishes because
point-source discharges are not expected to exceed water quality criteria. However, FEIS modeling
indicates that discharges from WTP #1 during operations would exceed the standard for ammonia; it is
also possible that the treated water discharges would result in seasonal exceedances of the turbidity
standard (USACE 2020: Section 4.18). Furthermore, fishes and other aquatic organisms are adapted to
the naturally occurring water chemistry in the SFK, NFK, and UTC headwaters, and the ambient
concentrations of many water chemistry parameters in these systems are much lower than existing
water quality criteria (O'Neal 2020). For this reason, water chemistry changes that do not exceed water
quality criteria but that significantly alter natural conditions may adversely affect aquatic biota.
In addition to water quality changes resulting from treated water releases, there is also the potential for
accidents and spills to affect water quality. Although the FEIS acknowledges the potential for acute
toxicity and sublethal effects on fish, conclusions regarding impacts to fishes from potential spills appear
to be based on the potential for direct habitat loss. For example, regarding the modeled pyritic tailings
release scenario, the FEIS states that "[c]admium and molybdenum would remain at levels exceeding the
most stringent [water quality criteria] as far downstream as the Nushagak River Estuary, approximately
230 miles downstream from the mine site" and "[t]hese metals would remain at elevated levels above
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of Aquatic Habitats and Fishes
WQC [water quality criteria] for several weeks..." (USACE 2020: Page 4.27-139). The FEIS concludes
that:
[t]he low-level use of the habitat that would be impacted (based on densities of juvenile Chinook and
coho salmon captured in these habitats) and the low numbers of coho spawning near the confluence of
Tributary SFK 1.240 with the SFK, indicates drainage-wide or generational impacts to populations of
salmon from direct habitat losses associated with the scenario would not be expected" (USACE 2020:
Page 4.27-144).
As discussed earlier, the FEIS does not appear to address impacts to aquatic resources from the elevated
metal concentrations, which would also affect fish populations.
The proposed mine also would likely alter water chemistry via land runoff and fugitive dust, and the
FEIS likely underestimates these impacts. For example, the volume of material that would potentially
leach metals to the environment is likely underestimated due to the use of a non-conservative
neutralization potential/acid-generating potential ratio to characterize materials (USACE 2020: Section
3.18), as well as the application of a large temperature correction that is not representative of field
conditions (USACE 2020: Appendix K3.18). The modeling of impacts from fugitive dust underreports the
area affected and does not account for watershed loading or the effects of seasonal flushes to surface
waters, such as during snowmelt (USACE 2020: Appendix K4.18). Watershed loading and "first flush"
effects are also relevant to the transport of leached metals to surface waters. The FEIS also does not take
into consideration the likely effect of sulfate loading from the treated water discharges on mercury
methylation and subsequent bioaccumulation in fish and other aquatic organisms.
Predicted changes in average stream water temperature in winter and summer months are presented in
Table 4.24-3 of the FEIS (USACE 2020: Section 4.24). Temperature is predicted to increase by up to
2.8°C within the NFK during winter months. The influence of temperature on fish bioenergetics is well
understood, and the FEIS acknowledges the potential for impacts to eggs and alevins in spawning
gravels (USACE 2020: Section 4.24). Even small increases in water temperature can affect salmon
development, growth, and timing of life-history events such as emergence and migration (e.g., Beacham
and Murray 1990, McCullough 1999, Fuhrman et al. 2018, Adelfio et al. 2019, Sparks et al. 2019).
Water quality in the SFK, NFK, and UTC are predicted to change downstream of the mine site under the
2020 Mine Plan, due to the loss of upstream aquatic habitats, changes in surface water and groundwater
flows, and the release of treated water discharges. These changes would create water quality conditions
that would differ from the current baseline conditions to which fish communities (as well as other
organisms) in the region are adapted. These changes would alter fish habitat and the ecological cues that
influence the timing of fish migration, spawning, incubation, emergence, rearing, and outmigration with
likely negative consequences. Because the FEIS does not consider these effects, it further underestimates
potential impacts of the 2020 Mine Plan to the region's aquatic resources.
B.5.2 Multiple, Cumulative Effects
Under the 2020 Mine Plan, aquatic resources in the SFK, NFK, and UTC watersheds would experience a
suite of co-occurring and interacting changes, including losses of headwater streams and wetlands;
Recommended Determination
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changes in streamflow regime due to changes in surface water and groundwater hydrology and treated
water discharges; and changes in water temperature and water chemistry. However, the FEIS estimates
effects of the 2020 Mine Plan by considering each impact independently—that is, by assuming each
effect would act in isolation, typically without consideration of how multiple effects acting
simultaneously would impact aquatic resources. Even considered in isolation, impacts on aquatic
habitats documented in the FEIS constitute an unacceptable adverse effect on fishery areas (Section
4.2); a more holistic evaluation of how the full suite of changes expected to result from the 2020 Mine
Plan would likely only increase the extent and magnitude of these impacts. This failure to consider
multiple, cumulative effects is evident across multiple contexts, as the following examples below
demonstrate.
• Effects on species, and life stages within species, are considered independently. There is no
consideration of how "optimization" of water discharges for priority species and life stages at
certain times of year would affect other species and life stages (USACE 2020: Section 4.24).
Similarly, there is no consideration of how the direct effects of the 2020 Mine Plan on one life stage
within a species will indirectly influence subsequent life stages (Marra et al. 2015), in addition to
any direct effects those life stages experience.
• Effects on fishes are considered only in terms of changes to fish habitat, despite that fact that fishes
also will be affected by impacts on lower trophic levels (e.g., macroinvertebrates, algae), which may
be particularly sensitive to changes in physical and chemical characteristics likely to occur under the
2020 Mine Plan.
• Effects in different sections of the stream channel are considered independently, without
consideration of how changes in upstream portions may influence effects in downstream portions
and vice versa (e.g., by affecting upstream movement).
• Effects of different stressors (e.g., changes in flow, temperature, water quality, and sedimentation)
are considered independently, without consideration of how simultaneous exposure to multiple
stressors, which also affect each other, would alter aquatic resources.
As a result, the FEIS likely underestimates how multiple, co-occurring changes associated with the 2020
Mine Plan would cumulatively affect the region's aquatic habitats and fish populations. Although all
aquatic resources in and downstream of the mine site would be affected by a suite of co-occurring (and
likely interacting) changes to chemical, physical, and biological conditions (Hodgson et al. 2019), the
impact of each change is only evaluated as if it would be acting in isolation. The impacts reported in the
FEIS likely represent a minimum estimate of how aquatic resources would be affected under the 2020
Mine Plan. This underestimation of cumulative impacts compounds the numerous underestimates of
single-factor impacts throughout the FEIS. For example, based only on modeled streamflow impacts, RFI
149 concludes that there would be a loss of more than 10 percent of Chinook Salmon spawning habitat
in the Koktuli River (PLP 2019f: RFI 149), a major producer of Chinook Salmon within the Nushagak
River and within the state of Alaska. For reasons discussed in Sections B.3 and B.4, this value likely
underestimates streamflow impacts to Chinook Salmon populations; this value also fails to account for
Recommended Determination
B-25
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other co-occurring contributors to Chinook Salmon population impacts that would result from the 2020
Mine Plan, such as changes in water temperature, water chemistry, and downstream transport of energy
and materials from headwater streams and wetlands.
B.6 Climate Change and Potential Mine Impacts to Aquatic
Habitats and Fish
The ecosystems that support Pacific salmon species, in Alaska and elsewhere, are experiencing rapid
changes due to a changing climate (Markon et al. 2018, Jones et al. 2020, von Biela et al. 2022). Alaska is
warming faster than any other state (Markon et al. 2018). Across the entire Bristol Bay watershed,
average temperature is projected to increase by approximately 4°C by the end of the century, with
winter temperatures projected to experience the highest increases (EPA 2014: Table 3-5, Figure 3-16).
Similar patterns are projected in the Nushagak and Kvichak River watersheds (EPA 2014: Table 3-5). By
the end of the century, precipitation is projected to increase roughly 30 percent across the Bristol Bay
watershed, for a total increase of approximately 250 mm annually (EPA 2014: Table 3-6, Figure 3-17). In
the Nushagak and Kvichak River watersheds, precipitation is projected to increase roughly 30 percent as
well, for a total increase of approximately 270 mm of precipitation annually (EPA 2014: Table 3-6). At
both spatial scales, increases in precipitation are expected to occur in all four seasons (EPA 2014: Table
3-6). Based on evapotranspiration calculations (i.e., calculations of the total amount of water moving
from the land surface to the atmosphere via evaporation and transpiration), annual water surpluses of
144 mm and 165 mm are projected for the Bristol Bay watershed and the Nushagak and Kvichak River
watersheds, respectively (EPA 2014: Table 3-7, Figure 3-18).
These projected changes in temperature and precipitation are likely to have repercussions for both
water management at the proposed mine and the surrounding aquatic resources. For example, increases
in air temperature are likely to affect evapotranspiration and exacerbate thermal stress, increasing the
probability of high severity wildfires (Lader et al. 2017). The combined effects of increased air
temperature, altered timing and type of precipitation, and vegetation changes likely will lead to altered
stream temperature regimes, with implications for fish metabolism and timing of key life history events.
For example, if water temperatures increase and cold-water species cannot find optimal conditions of
groundwater exchange, incubating eggs may fail to develop or develop too rapidly. In precipitation
driven streams, Adelfio et al. (2019) reported shifts in modeled incubation timing by Coho Salmon by up
to 3 months during years with warmer winters. Given that substantially warmer winters are projected
to be increasingly common in Alaska in the near future (Lader et al. 2017), these life history shifts may
become increasingly common. Such shifts in timing can result in egg emergence that is out of sync with
the availability of food resources (Cushing 1990, McCracken 2021), as well as other asynchronizations
across salmon life histories. These life history shifts may disrupt the adaptation of salmon life stages to
local environmental conditions, particularly if altered timing of key life history events such as
emergence, migration, or seasonal movements is no longer synched to favorable conditions for salmonid
growth and survival. These changes can lead to adverse impacts on resilience of Pacific salmon
populations (Crozier et al. 2008).
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Such increases in temperature (and associated adverse ecological effects) can occur during the winter,
and at temperatures well below the State of Alaska's critical temperature threshold for spawning or egg
incubation (13°C; ADEC 2020). Thermal effects on fry size and emergence timing can interact with
streamflow to adversely affect juvenile salmon survival. Increases in precipitation, as well as changes in
the seasonality of precipitation, snowpack, and the timing of snowmelt, would likely affect streamflow
regimes. High-intensity rainfalls, projected to increase in frequency with climate change (Lader et al.
2017), may contribute to increased scouring and sedimentation of stream channels. Increased exposure
to earlier or larger peak streamflows can displace incubating eggs or newly emerged salmon fry,
contributing to mortality. Stream types at the mine site are highly susceptible to scour and erosion and
could be destabilized significantly by streamflow or sediment regime changes (Brekken et al. 2022).
Wobus et al. (2015) incorporated climate change scenarios into an integrated hydrologic model for the
upper Nushagak and Kvichak River watersheds. These simulations projected changes in water
temperature, average winter streamflows, and dates of peak streamflows by 2100 (Wobus et al. 2015).
Ultimately, these projected increases in temperature and changes in hydrology could affect salmon
populations in multiple ways, such as alteration of spawning and rearing habitats, changes in fry
emergence and growth patterns, and direct thermal stress (Tang et al. 1987, Beer and Anderson 2001,
Bryant 2009, Wobus et al. 2015).
Despite these expected climate changes in the Bristol Bay region, many of the models used in the FEIS to
evaluate potential impacts of the 2020 Mine Plan were parameterized based on past environmental
conditions. For example, the mine site water-balance model included in the FEIS incorporated climate
variability by using the 76-year average monthly synthetic temperature and precipitation record
(USACE 2020: Section 3.16). EPA (2019) recommended that the FEIS consider how projected changes in
the type (e.g., snow versus rain) and timing of precipitation could affect impacts to aquatic resources
under the 2020 Mine Plan, but no future climate scenarios were included in the FEIS analysis of
streamflow changes under the 2020 Mine Plan. It is not clear that past variability in temperature and
precipitation will adequately capture future variability. Schindler and Hilborn (2015) stated that "...we
should expect that the future is not likely to be a simple extrapolation of the recent past." Predictions of
future habitat based on conditions in the recent past—or even current conditions—are of limited utility
(Moore and Schindler 2022). As a result, models like those used in the FEIS may fail to adequately
characterize mine impacts in ecosystems experiencing an altered future climate (Sergeant et al. 2022).
A thorough evaluation of potential impacts under the 2020 Mine Plan should consider future climate
scenarios, particularly in terms of water treatment and management and potential effects on aquatic
habitats and salmon populations. Even without this evaluation, the impacts on aquatic habitats
documented in the FEIS constitute an unacceptable adverse effect on fishery areas (Section 4.2);
consideration of how future climate conditions would affect these impacts would not change this
unacceptability finding, but would give a more complete assessment of likely effects associated with the
2020 Mine Plan. A key feature of salmon populations in the Bristol Bay watershed is their genetic and
life history diversity (i.e., the portfolio effect), which serves as an overall buffer for the entire population
(Section 3.3.3). Different sub-populations may be more productive in different years, which affords the
Recommended Determination
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entire population stability under variable conditions year to year. If this variability increases over time
due to changes in temperature and precipitation patterns, this portfolio effect becomes increasingly
important in providing the genetic diversity to potentially allow for adaptation; thus, affecting or
destroying genetically diverse populations may have a larger than expected effect on the overall Bristol
Bay fishery under future climate conditions.
B.7 References
ADEC (Alaska Department of Environmental Conservation). 2020.18AAC 70 Water Quality Standards,
Amended as of March 5,2020.
Adelfio, L. A., S. M. Wondzell, N. J. Mantua, and G. H. Reeves. 2019. Warm winters reduce landscape-scale
variability in the duration of egg incubation for coho salmon (Oncorhynchus kisutch) on the Copper
River Delta, Alaska. Canadian Journal of Fisheries and Aquatic Sciences 76:1362-1375.
ADF&G (Alaska Department of Fish and Game). 2022a. Alaska Freshwater Fish Inventory (AFFI)
Database. Anchorage, AK. Available: http://www.adfg.alaska.gov/index.cfm?adfg=ffinventory.main.
Accessed: February 22, 2022.
ADF&G. 2022b. Anadromous Waters Catalog: Overview. Alaska Department of Fish and Game. Available:
https://www.adfg.alaska.gov/sf/SARR/AWC/index.cfm?ADFG=main.home. Accessed: May 16, 2022.
ADF&G. 2022c. 2022 Bristol Bay Salmon Season Summary. Anchorage, AK: Alaska Department of Fish and
Game, Division of Commercial Fisheries.
Anderson, K. E., A. J. Paul, E. McCauley, L. J. Jackson, J. R. Post, and R. M. Nisbet. 2006. Instream flow
needs in streams and rivers: the importance of understanding ecological dynamics. Frontiers in
Ecology and the Environment 4:309-318.
Armstrong, J. B., and D. E. Schindler. 2013. Going with the flow: spatial distributions of juvenile coho
salmon track an annually shifting mosaic of water temperature. Ecosystems 16:1429-1441.
Beacham, T. D., and C. B. Murray. 1990. Temperature, egg size, and development of embryos and alevins
of 5 species of Pacific salmon - a comparative analysis. Transactions of the American Fisheries Society
119:927-945.
Beer, W. N., and J. J. Anderson. 2001. Effect of spawning day and temperature on salmon emergence:
interpretations of a growth model for Methow River chinook. Canadian Journal of Fisheries and
Aquatic Sciences 58:943-949.
Benda, L., N. L. Poff, D. Miller, T. Dunne, G. Reeves, G. Pess, and M. Pollock. 2004. The network dynamics
hypothesis: how channel networks structure riverine habitats. Bioscience 54:413-427.
Recommended Determination
B-28
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Bevelhimer, M. S., R. A. McManamay, and B. O'Connor. 2015. Characterizing sub-daily flow regimes:
implications of hydrologic resolution on ecohydrology studies. River Research and Applications
31:867-879.
Bovee, K. D. 1986. Development and Evaluation of Habitat Suitability Criteria for Use in the Instream Flow
Incremental Methodology. Instream Flow Information Paper No. 21 (OBS 86/7). Washington, DC: U.S.
Fish and Wildlife Service, Instream Flow and Aquatic Systems Group.
Bovee, K. D., B. L. Lamb, J. M. Bartholow, C. D. Stalnaker, J. Taylor, and J. Henrikson. 1998. Stream Habitat
Analysis Using the Instream Flow Incremental Methodology. Information and Technical Report
USGS/BRD-1998-0004. Fort Collins, CO: U.S. Geological Survey, Biological Resources Division.
Brekken, J. M., K. J. Harper, J. M. Alas, and R. C. Benkert. 2022. Aquatic Biomonitoring at the Pebble
Prospect, 2010-2013. Technical Report No. 22-09. Anchorage, AK: Alaska Department of Fish and
Game, Habitat Section.
Brennan, S. R., D. E. Schindler, T. J. Cline, T. E. Walsworth, G. Buck, and D. P. Fernandez. 2019. Shifting
habitat mosaics and fish production across river basins. Science 364:783-786.
Bryant, M. D. 2009. Global climate change and potential effects on Pacific salmonids in freshwater
ecosystems of southeast Alaska. Climatic Change 95:169-193.
Bunn, S. E., and A. H. Arthington. 2002. Basic principles and ecological consequences of altered flow
regimes for aquatic biodiversity. Environmental Management 30:492-507.
Crozier, L. G., A. P. Hendry, P. W. Lawson, T. P. Quinn, N. J. Mantua, R. G. Shaw, and R. B. Huey. 2008.
Potential responses to climate change in organisms with complex life histories: evolution and
plasticity in Pacific salmon. Evolutionary Applications 1:252-270.
Cummins, K. W., and M. A. Wilzbach. 2005. The inadequacy of the fish-bearing criterion for stream
management. Aquatic Sciences 67:486-491.
Cushing, D. H. 1990. Plankton production and year-class strength in fish populations: an update of the
match/mismatch hypothesis. Advances in Marine Biology 26:249-293.
Davis, B. M., and D. E. Schindler. 2021. Effects of variability and synchrony in assessing contributions of
individual streams to habitat portfolios of river basins. Ecological Indicators 124: 107427.
EPA (U.S. Environmental Protection Agency). 2014. An Assessment of Potential Mining Impacts on Salmon
Ecosystems of Bristol Bay, Alaska. Final Report. EPA 910-R-14-001. Washington, DC.
EPA. 2019. EPA Comments on Pebble Project DEIS (Letter from Chris Hladick, EPA Region 10 Regional
Administrator, to Shane McCoy, USACE Alaska District Program Manager). July 1.
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Freeman, M. C., K. R. Bestgen, D. Carlisle, E. A. Frimpong, N. R. Franssen, K. B. Gido, E. Irwin, Y. Kanno, C.
Luce, S. K. McKay, M. C. Mims, J. D. Olden, N. L. Poff, D. L. Propst, L. Rack, A. H. Roy, E. S. Stowe, A.
Walters, and S. J. Wenger. 2022. Toward improved understanding of streamflow effects on
freshwater fishes. Fisheries 47:290-298.
Fuhrman, A. E., D. A. Larsen, E. A. Steel, G. Young, and B. R. Beckman. 2018. Chinook salmon emergence
phenotypes: describing the relationships between temperature, emergence timing and condition
factor in a reaction norm framework. Ecology of Freshwater Fish 27:350-362.
George, R., R. McManamay, D. Perry, J. Sabo, and B. L. Ruddell. 2021. Indicators of hydro-ecological
alteration for the rivers of the United States. Ecological Indicators 120:106908.
Giefer, J., and S. Graziano. 2022. Catalog of Waters Important for Spawning, Rearing, or Migration of
Anadromous Fishes—Southwestern Region, Effective June 15, 2022. Special Publication No. 22-05.
Anchorage, AK: Alaska Department of Fish and Game. Available:
https://www.adfg.alaska.gov/sf/SARR/AWC/index.cfm?ADFG=main.home. Accessed: September
29,2022.
Goguen, G., D. Caissie, and N. El-Jabi. 2020. Uncertainties associated with environmental flow metrics.
River Research and Applications 9:1879-1890.
Hardy, T. B., T. Shaw, R. C. Addley, G. E. Smith, M. Rode, and M. Belchik. 2006. Validation of chinook fry
behavior-based escape cover modeling in the lower Klamath River. International Journal of River
Basin Management 4:169-178.
Hodgson, E. E., B. S. Halpern, and T. E. Essington. 2019. Moving beyond silos in cumulative effects
assessment. Frontiers in Ecology and Evolution 7:211.
Jones, E. L. Ill, S. Heinl, and K. Pahlke. 2007. Aerial counts. Pages 399-409 in D.H. Johnson, B. M. Shrier, J.
S. O'Neal, J. A. Knutsen, X. Augerot, T. A. O'Neil, and T. N. Pearsons (eds.), Salmonid Field Protocols
Handbook: Techniques for Assessing Status and Trends in Salmon and Trout Populations. Bethesda,
MD: American Fisheries Society.
Jones, L. A., E. R. Schoen, R. Shaftel, C. J. Cunningham, S. Mauger, D. J. Rinella, and A. S. Saviour. 2020.
Watershed-scale climate influences productivity of Chinook salmon populations across southcentral
Alaska. Global Change Biology 26:4919-4936.
Kennard, M. J., S. J. Mackay, B. J. Pusey, J. D. Olden, and N. Marsh. 2010. Quantifying uncertainty in
estimation of hydrologic metrics for eco-hydrological studies. River Research and Applications
26:137-156.
Lader, R., J. E. Walsh, U. S. Bhatt, and P. A. Bieniek. 2017. Projections of twenty-first century climate
extremes for Alaska via dynamical downscaling and quantile mapping. Journal of Applied
Meteorology and Climatology 56:2393-2409.
Levin, S. A. 1992. The problem of pattern and scale in ecology. Ecology 73:1943-1967.
Recommended Determination
B-30
December 2022
-------
Appendix B
Additional Information Related to the Assessment
of Aquatic Habitats and Fishes
Lytle, D. A., and N. L. Poff. 2004. Adaptation to natural flow regimes. Trends in Ecology & Evolution
19:94-100.
Markon, C., S. Gray, M. Berman, L. Eerkes-Medrano, T. Hennessy, H. Huntington, J. Littell, M. McCammon,
R. Thoman, and S. Trainor. 2018. Alaska. Pages 1185-1241 in D. R. Reidmiller, C. W. Avery, D. R.
Easterling, K. E. Kunkel, K. L. M. Lewis, T. K. Maycock, and B. C. Stewart (eds.), Impacts, Risks, and
Adaptation in the United States: Fourth National Climate Assessment, Volume II. Washington, DC: U.S.
Global Change Research Program.
Marra, P. P., E. B. Cohen, S. R. Loss, J. E. Rutter, and C. M. Tonra. 2015. A call for full annual cycle research
in animal ecology. Biology Letters 11:20150552.
McCracken, B. W. 2021. Spawning Site Selection ofCoho Salmon Oncorhynchus kisutch in Susitna River
Tributaries, Alaska. M.S. Thesis, University of Alaska Fairbanks. Fairbanks, AK.
McCullough, D. A., J. M. Bartholow, H. I. Jager, R. L. Beschta, E. F. Cheslak, M. L. Deas, J. L. Ebersole, J. S.
Foott, S. L. Johnson, K. R. Marine, M. G. Mesa, J. H. Petersen, Y. Souchon, K. F. Tiffan, and W. A.
Wurtsbaugh. 2009. Research in thermal biology: Burning questions for coldwater stream fishes.
Reviews in Fisheries Science 17:90-115.
Montgomery, D. R., and J. M. Buffington. 1997. Channel-reach morphology in mountain drainage basins.
Geological Society of America Bulletin 109:596-611.
Montgomery, D. R., E. M. Beamer, G. R. Pess, and T. P. Quinn. 1999. Channel type and salmonid spawning
distribution and abundance. Canadian Journal of Fisheries and Aquatic Sciences 56:377-387.
Moore, J. W., and D. E. Schindler. 2022. Getting ahead of climate change for ecological adaptation and
resilience. Science 376:1421-1426.
Morstad, S., C. Westing, T. Sands, and P. Salomone. 2009. Salmon Spawning Ground Surveys in the Bristol
Bay Area, Alaska, 2007. Fishery Management Report No. 09-06. Alaska Department of Fish and Game,
Division of Sport Fish, Research, and Technical Services. Anchorage, AK.
Naman, S. M., J. S. Rosenfeld, J. R. Neuswanger, E. C. Enders, and B. C. Eaton. 2019. Comparing correlative
and bioenergetics-based habitat suitability models for drift-feeding fishes. Freshwater Biology
64:1613-1626.
Naman, S. M., J. S. Rosenfeld, J. R. Neuswanger, E. C. Enders, J. W. Hayes, E. 0. Goodwin, I. G. Jowett, and B.
C. Eaton. 2020. Bioenergetic habitat suitability curves for instream flow modeling: introducing user-
friendly software and its potential applications. Fisheries 45:605-613.
NMFS (National Marine Fisheries Service). 2020. NMFS Comments on Pebble Project Essential Fish
Habitat Assessment. Letter from James Balsiger, Alaska Region Administrator, to Colonel David
Hibner, U.S. Army Corps of Engineers. August 18.
Recommended Determination
B-31
December 2022
-------
Appendix B
Additional Information Related to the Assessment
of Aquatic Habitats and Fishes
O'Neal, S. 2020. Toxicological shortcomings of the Pebble Project Final Environmental Impact Statement
(FEIS). Technical memorandum prepared for the Wild Salmon Center.
PLP (Pebble Limited Partnership). 2011. Pebble Project Environmental Baseline Document, 2004 through
2008. Anchorage, AK. Available: https://www.arlis.org/docs/vol2/Pebble/2004-2008EBDIndex.pdf.
PLP. 2018a. Pebble Project Supplemental Environmental Baseline Data Report, 2004-2012. Anchorage,
AK.
PLP. 2018b. RFI048: Revised Habitat Time Series Analysis. AEC0M Request for Information to Pebble
Limited Partnership, September 28.
PLP. 2019a. RFI 109g: Comprehensive Water Modeling System. AECOM Request for Information to Pebble
Limited Partnership, October 7.
PLP. 2019b. RFI 109f: Streamflow Estimates from New Groundwater Model. AECOM Request for
Information to Pebble Limited Partnership, October 11.
PLP. 2019c. RFI 135: Monitoring and Adaptive Management Plan. AECOM Request for Information,
Pebble Limited Partnership, December 23.
PLP. 2019d. RFI 109d: Groundwater Model Validation and Sensitivity Analysis. AECOM Request for
Information, Pebble Limited Partnership, June 20.
PLP. 2019e. RFI 147: Appendix to Summarize Fish Habitat Modeling Procedures. AECOM Request for
Information to Pebble Limited Partnership, November 1.
PLP. 2019f. RFI 149: Fish Habitat Modeling Results for Adult Resident Salmonids by Stream Reach. AECOM
Request for Information to Pebble Limited Partnership, November 21.
Poff, N. L., and J. K. H. Zimmerman. 2010. Ecological responses to altered flow regimes: a literature
review to inform the science and management of environmental flows. Freshwater Biology 55:194-
205.
Poff, N. L., J. D. Allan, M. B. Bain, J. R. Karr, K. L. Prestegaard, B. D. Richter, R. E. Sparks, and J. C.
Stromberg. 1997. The natural flow regime: A paradigm for river conservation and restoration.
Bioscience 47:769-784.
Pollock, M. M., G. R. Pess, T. J. Beechie, and D. R. Montgomery. 2004. The importance of beaver ponds to
coho salmon production in the Stillaguamish River basin, Washington, USA. North American Journal
of Fisheries Management 24:749-760.
Railsback, S. F. 2016. Why it is time to put PHABSIM out to pasture. Fisheries 41:720-725.
Richter, B. D., J. V. Baumgartner, J. Powell, and D. P. Braun. 1996. A method for assessing hydrologic
alteration within ecosystems. Conservation Biology 10:1163-1174.
Recommended Determination
B-32
December 2022
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Appendix B
Additional Information Related to the Assessment
of Aquatic Habitats and Fishes
Rogers, L. A., and D. E. Schindler. 2008. Asynchrony in population dynamics of sockeye salmon in
southwest Alaska. Oikos 117:1578-1586.
Rogers, L. A., D. E. Schindler, P. J. Lisi, G. W. Holtgrieve, P. R. Leavitt, L. Bunting, B. P. Finney, D. T. Selbie,
G. J. Chen, I. Gregory-Eaves, M. J. Lisac, and P. B. Walsh. 2013. Centennial-scale fluctuations and
regional complexity characterize Pacific salmon population dynamics over the past five centuries.
Proceedings of the National Academy of Sciences of the United States of America 110:1750-1755.
Rosenfeld, J. 2003. Assessing the habitat requirements of stream fishes: an overview and evaluation of
different approaches. Transactions of the American Fisheries Society 132:953-968.
Rosenfeld, J. S., and S. M. Naman. 2021. Identifying and mitigating systematic biases in fish habitat
simulation modeling: implications for estimating minimum instream flows. River Research and
Applications 37:869-879.
Schindler, D. E., and R. Hilborn. 2015. Prediction, precaution, and policy under global change. Science
347:953-954.
Sergeant, C. J., E. K. Sexton, J. W. Moore, A. R. Westwood, S. A. Nagorski, J. L. Ebersole, D. M. Chambers, S.
L. O'Neal, R. L. Malison, F. R. Hauer, D. C. Whited, J. Weitz, J. Caldwell, M. Capito, M. Connor, C. A.
Frissell, G. Knox, E. D. Lowery, R. Macnair, V. Marlatt, J. Mclntyre, M. V. McPhee, and N. Skuce. 2022.
Risks of mining to salmonid-bearing watersheds. Science Advances 8:eabn0929.
Sobolewski, A. 2020. Review of Water Treatment Plants Proposed in FEIS for Pebble Project. Technical
memorandum prepared for the Wild Salmon Center.
Sofi, M. S., S. U. Bhat, I. Rashid, and J. C. Kuniyal. 2020. The natural flow regime: a master variable for
maintaining river ecosystem health. Ecohydrology 13:e2247.
Sparks, M. M., J. A. Falke, T. P. Quinn, M. D. Adkison, D. E. Schindler, K. Bartz, D. Young, and P. A. H.
Westley. 2019. Influences of spawning timing, water temperature, and climatic warming on early life
history phenology in western Alaska sockeye salmon. Canadian Journal of Fisheries and Aquatic
Sciences 76:123-135.
Swales, S., and C. D. Levings. 1989. Role of off-channel ponds in the life cycle of coho salmon
(iOncorhynchus kisutch) and other juvenile salmonids in the Coldwater River, British Columbia.
Canadian Journal of Fisheries and Aquatic Sciences 46:232-242.
Tang, J., M. D. Bryant, and E. L. Brannon. 1987. Effect of temperature extremes on the mortality and
development rates of coho salmon embryos and alevins. Progressive Fish-Culturist 49:167-174.
Tiernan, A., T. Elison, T. Sands, J. Head, S. Vega, and G. Neufeld. 2021.2020 Bristol Bay Area Annual
Management Report. Fishery Management Report No. 21-16. Anchorage, AK: Alaska Department of
Fish and Game, Divisions of Sport Fish and Commercial Fisheries.
Recommended Determination
B-33
December 2022
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Additional Information Related to the Assessment
Appendix B of Aquatic Habitats and Fishes
Tonkin, J. D., J. D. Olden, D. M. Merritt, L. V. Reynolds, J. S. Rogosch, and D. A. Lytle. 2021. Designing flow
regimes to support entire river ecosystems. Frontiers in Ecology and the Environment 19:326-333.
USACE (U.S. Army Corps of Engineers). 2020. Pebble Project EIS: Final Environmental Impact Statement.
Department of the Army Permit #POA-2017-00271.
USGS (U.S. Geological Survey). 2022. National Water Information System: Data for USGS15302250 NF
Koktuli R NR Iliamna AK. Available: https://waterdata.usgs.gov/nwis/inventory?site_no=15302250.
Accessed: October 18, 2022.
Van Home, B. 1983. Density as a misleading indicator of habitat quality. Journal of Wildlife Management
47:893-901.
von Biela, V. R., C. J. Sergeant, M. P. Carey, Z. Liller, C. Russell, S. Quinn-Davidson, P. S. Rand, P. A. H.
Westley, and C. E. Zimmerman. 2022. Premature mortality observations among Alaska's Pacific
salmon during record heat and drought in 2019. Fisheries 47:157-168.
Waddle, T. 2001. PHABSIMfor Windows User's Manual and Exercises. Open-File Report 2001-340. Fort
Collins, CO: U.S. Geological Survey, Midcontinent Ecological Science Center.
Warren, C. E. 1971. Biology and Water Pollution Control. W. B. Saunders, Philadelphia, PA.
Warren, M., M. J. Dunbar, and C. Smith. 2015. River flow as a determinant of salmonid distribution and
abundance: a review. Environmental Biology of Fishes 98:1695-1717.
Wobus, C., and R. Prucha. 2020. Comments on the Pebble Project Final EIS. Technical memorandum
prepared for the Wild Salmon Center.
Wobus, C., R. Prucha, D. Albert, C. Woll, M. Loinaz, and R. Jones. 2015. Hydrologic alterations from
climate change inform assessment of ecological risk to Pacific salmon in Bristol Bay, Alaska. PLoS
One 10:e0143905.
Woody, C. A., and B. Higman. 2011. Groundwater as Essential Salmon Habitat in Nushagak and Kvichak
River Headwaters: Issues Relative to Mining. Report prepared for Center for Science in Public
Participation.
Recommended Determination
B-34
December 2022
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Appendix C
Technical Evaluation of Potential Compensatory
Mitigation Measures
Recommended Determination
December 2022
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Executive Summary C-l
Section 1. Compensatory Mitigation Background.............................................................................. C-2
1.1 Location, Type, and Amount of Compensation C-2
1.2 Compensatory Mitigation Guidance for Alaska C-3
Section 2. Important Ecological Functions and Services Provided by Affected Streams and
Wetlands ..........................................................................................................................................C-5
2.1 Aquatic Resources Affected at the Proposed Mine Site C-5
2.2. Importance of Affected Aquatic Resources C-5
2.3 Identifying the Appropriate Watershed Scale for Compensatory Mitigation C-7
Section 3. Review of Additional Potential Compensatory Mitigation Measures C-8
3.1 Permittee-Responsible Compensatory Mitigation C-8
3.1.1 Compensation Measures Suggested within the SFK, NFK, and UTC Watersheds C-8
3.1.1.1 Increase Habitat Connectivity C-8
3.1.1.1.1 Remove Beaver Dams C-9
3.1.1.1.2. Connect Off-channel Habitats and Habitat Above
Impassible Waterfalls C-ll
3.1.1.2. Increase Habitat Quality C-13
3.1.1.3 Increase Habitat Quantity C-15
3.1.1.4 Manage Water Quantity C-17
3.1.1.4.1 Direct Excess On-site Water C-17
3.1.1.4.2. Augment Flows C-18
3.1.1.4.3 Pump Water Upstream C-19
3.1.1.5 Manipulate Water Quality C-19
3.1.1.5.1 Increase Levels of Alkalinity, Hardness, and Total
Dissolved Solids C-20
3.1.1.5.2. Increase Levels of Nitrogen and/or Phosphorus C-21
3.1.2. Other Potential Compensation Measures Suggested within the Nushagak and
Kvichak River Watersheds C-25
3.1.2.1 Remediate Old Mine Sites C-25
3.1.2.2 Remove Roads C-25
3.1.2.3 Retrofit Road Stream Crossings C-26
3.1.2.4 Construct Hatcheries C-26
3.1.2.5 Stock Fish C-27
3.2. Other Suggested Measures C-28
Recommended Determination n; December 2022
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Appendix C
Technical Evaluation of Potential
Compensatory Mitigation Measures
Section 4. Effectiveness of Compensation Measures at Offsetting Impacts on Fish Habitat............. C-29
Section 5. Conclusions..................................................................................................................... C-33
Section 6. References...................................................................................................................... C-34
6.1 Citations ...........................................................................................................................................C-34
6.2 Additional Publications Reviewed C-SO
Recommended Determination
C-ii
December 2022
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Appendix C
Technical Evaluation of Potential
Compensatory Mitigation Measures
Acronyms and Abbreviations
BBA
Bristol Bay Assessment
CWA
Clean Water Act
DA
Department of the Army
EBD
Environmental Baseline Document
EPA
Environmental Protection Agency
FEIS
Final Environmental Impact Statement
MOA
Memorandum of Agreement
NFK
North Fork Koktuli River
NOAA
National Oceanic and Atmospheric Administration
PLP
Pebble Limited Partnership
ROD
Record of Decision
SFK
South Fork Koktuli River
TDS
total dissolved solids
USACE
U.S. Army Corps of Engineers
USGS
U.S. Geologic Survey
UTC
Upper Talarik Creek
WTP
wastewater treatment plant
Recommended Determination
C-iii
December 2022
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Compensatory mitigation refers to the restoration, establishment, enhancement, and/or in certain
circumstances preservation of wetlands, streams, or other aquatic resources. Compensatory mitigation
regulations jointly promulgated by the U.S. Environmental Protection Agency (EPA) and the U.S. Army
Corps of Engineers (USACE) state that "the fundamental objective of compensatory mitigation is to offset
environmental losses resulting from unavoidable impacts to waters of the United States authorized by
[Clean Water Act (CWA) Section 404 permits issued by USACE]" (40 CFR 230.93(a)(1)). Compensatory
mitigation enters the analysis only after a proposed project design has incorporated all appropriate and
practicable means to avoid and minimize adverse impacts on aquatic resources (40 Code of Federal
Regulations [CFR] 230.91(c)).
The Pebble Limited Partnership (PLP) has proposed to develop the Pebble copper-gold-molybdenum
porphyry deposit as a surface mine in the Bristol Bay watershed in southwest Alaska (i.e., the 2020 Mine
Plan) (PLP 2020b). In its 2022 Recommended Determination of the U.S. Environmental Protection Agency
Region 10 Pursuant to Section 404(c) of the Clean Water Act: Pebble Deposit Area, Southwest Alaska, EPA
Region 10 finds that the estimated loss and degradation of wetlands, streams, and other aquatic
resources resulting from the discharge of dredged or fill material for the construction and routine
operation of the 2020 Mine Plan would be likely to have unacceptable adverse effects on fishery areas.
During development and finalization of the Bristol Bay Assessment (BBA) (EPA 2014) between 2011
and 2014 and review of an earlier 404(c) proposed determination regarding the Pebble deposit
published in 2014, PLP and other commenters suggested an array of measures as having the potential to
compensate for the nature and magnitude of adverse impacts on wetlands, streams, and fish from the
discharge of dredged or fill material associated with mining the Pebble deposit.
This appendix provides a detailed technical evaluation of each of these measures, for informational
purposes. Available information demonstrates that known compensation measures are unlikely to
adequately mitigate effects described in this recommended determination to an acceptable level.
Recommended Determination
C-l
December 2022
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Compensatory mitigation is defined as the restoration, establishment, enhancement, and/or, in certain
circumstances, preservation of wetlands, streams, or other aquatic resources conducted specifically for
the purpose of offsetting unavoidable authorized impacts to these types of resources (40 Code of
Federal Regulations [CFR] 230.92, Hough and Robertson 2009). According to compensatory mitigation
regulations jointly promulgated by the U.S. Environmental Protection Agency (EPA) and the U.S. Army
Corps of Engineers (USACE), "the fundamental objective of compensatory mitigation is to offset
environmental losses resulting from unavoidable impacts to waters of the United States authorized by
[Clean Water Act (CWA) Section 404 permits issued by USACE]" (40 CFR 230.93(a)(1)).
Section 404 permitting requirements for compensatory mitigation are based on what is "practicable and
capable of compensating for the aquatic resource functions that will be lost as a result of the permitted
activity" (40 CFR 230.93(a)(1)). In determining what type of compensatory mitigation will be
"environmentally preferable," USACE "must assess the likelihood for ecological success and
sustainability, the location of the compensation site relative to the impact site and their significance
within the watershed, and the costs of the compensatory mitigation project" (40 CFR 230.93(a)(1)).
Furthermore, compensatory mitigation requirements must be commensurate with the amount and type
of impact associated with a particular Section 404 permit (40 CFR 230.93(a)(1)).
1.1 Location, Type, and Amount of Compensation
Regulations regarding compensatory mitigation require the use of a watershed approach to "establish
compensatory mitigation requirements in [Department of the Army] permits to the extent appropriate
and practicable" (40 CFR 230.93(c)(1)). Under these regulations, the watershed approach to
compensatory mitigation site selection and planning is an analytical process for making compensatory
mitigation decisions that support the sustainability or improvement of aquatic resources in a watershed.
It involves consideration of watershed needs and how locations and types of compensatory mitigation
projects address those needs (40 CFR 230.92). The regulations specifically state that compensatory
mitigation generally should occur within the same watershed as the impact site and in a location where
it is most likely to successfully replace lost functions and services (40 CFR 230.93(b)(1)). The goal of this
watershed approach is to "maintain and improve the quality and quantity of aquatic resources within
watersheds through strategic selection of compensatory mitigation sites" (40 CFR 230.93(c)(1)).
The regulations emphasize using existing watershed plans to inform compensatory mitigation decisions
when such plans are determined to be appropriate for use in this context (40 CFR 230.93(c)(1)). Where
appropriate plans do not exist, the regulations describe the types of considerations and information that
should be used to support a watershed approach to compensation decision-making. Central to the
Recommended Determination
C-2
December 2022
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Appendix C
Technical Evaluation of Potential
Compensatory Mitigation Measures
watershed approach is consideration of how the types and locations of potential compensatory
mitigation projects would sustain aquatic resource functions in the watershed. To achieve that goal, the
regulations emphasize that mitigation projects should, where practicable, replace the suite of functions
typically provided by the affected aquatic resource, rather than focus on specific individual functions (40
CFR 230.93(c)(2)). For this purpose, "watershed" means an "area that drains to a common waterway,
such as a stream, lake, estuary, wetland, or ultimately the ocean" (40 CFR 230.92). Although there is
flexibility in defining geographic scale, the watershed "should not be larger than is appropriate to ensure
that the aquatic resources provided through compensation activities will effectively compensate for
adverse environmental impacts resulting from [permitted] activities" (40 CFR 230.93(c)(4)).
With regard to type, in-kind mitigation (i.e., involving resources similar to those being impacted) is
generally preferable to out-of-kind mitigation, because it is most likely to compensate for functions lost
at the impact site (40 CFR 230.93(e)(1)). Furthermore, the regulations recognize that, for difficult-to-
replace resources such as bogs, fens, springs, and streams, in-kind "rehabilitation, enhancement, or
preservation" should be the compensation of choice, given the greater likelihood of success of those
types of mitigation (40 CFR 230.93(e)(3)).
The amount of compensatory mitigation required must be, to the extent practicable, "sufficient to
replace lost aquatic resource functions" (40 CFR 230.93(f)(1)), as determined through the use of a
functional or condition assessment. If an applicable assessment methodology is not available, the
regulations require a minimum one-to-one acreage or linear foot compensation ratio (40 CFR
230.93(f)(1)). Certain circumstances require higher ratios, even in the absence of an assessment
methodology (e.g., use of preservation, lower likelihood of success, differences in functionality between
the impact site and compensation project, difficulty of restoring lost functions, and the distance between
the impact and compensation sites) (40 CFR 230.93(f)(2)).
1.2 Compensatory Mitigation Guidance for Alaska
In addition to the federal regulations regarding compensatory mitigation, EPA and the DA have also
developed compensatory mitigation guidance applicable specifically to Alaska in a 2018 Memorandum
of Agreement (MOA) (EPA and DA 2018).1 The 2018 MOA provides guidance regarding flexibilities that
exist in the mitigation requirements for CWA Section 404 permits, and how those flexibilities can be
applied in Alaska given the abundance of wetlands and unique circumstances involved with Section 404
permitting in the state. Accordingly, the 2018 MOA recognizes that restoring, enhancing, or establishing
wetlands for compensatory mitigation may not be practicable due to limited availability of sites and/or
technical or logistical limitations. It also recognizes that compensatory mitigation options over a larger
1 This MOA updates and replaces the EPA and DA Memoranda entitled Clarification of the Clean Water Act Section
404 Memorandum of Agreement on Mitigation, dated January 24,1992, and Statements on the Mitigation Sequence
and No Net Loss of Wetlands in Alaska, dated May 13,1994.
Recommended Determination
C-3
December 2022
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Appendix C
Technical Evaluation of Potential
Compensatory Mitigation Measures
watershed scale may be appropriate given that compensation options are frequently limited at a smaller
watershed scale.
The 2018 MOA also identifies when compensatory mitigation may be required to ensure that an activity
requiring a Section 404 permit complies with the CWA Section 404(b)(1) Guidelines (40 CFR Part
230.91(c)(2)). The 2018 MOA provides the following examples.
• Compensatory mitigation may be required to ensure that discharges do not cause or contribute to a
violation of water quality standards or jeopardize a threatened or endangered species or result in
the destruction or adverse modification of critical habitat under the Endangered Species Act (40 CFR
Part 230.10(b)).
• Compensatory mitigation may be required to ensure that discharges do not cause or contribute to
significant degradation (40 CFR Part 230.10(c)).
• The Section 404(b)(1) Guidelines also require compensatory mitigation measures when appropriate
and practicable (40 CFR Parts 230.10(d), 230.12, 230.91, and 230.93(a)(1)).
The 2018 MOA also notes that during the Section 404(b)(1) Guidelines compliance analysis, USACE may
determine that a Section 404 permit for a proposed discharge cannot be issued because of a lack of
appropriate and practicable compensatory mitigation options (40 CFR Part 230.91(c)(3)).
It is important to remember that decisions regarding the appropriate type, amount, and location of
compensatory mitigation are made on a case-by-case basis and depend on a number of factors, including
the type, amount, and location of aquatic resources being impacted.
Recommended Determination
C-4
December 2022
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N 2. IMPORTANT ECOLOGICAL FUNCTIONS AN
U rill! j i i W il :VJM aaaftfisl iM i: I =f*I MM I ilWJ a I V>:
2.1 Aquatic Resources Affected at the Proposed Mine Site
As discussed in Section 2 of the recommended determination, the Pebble Limited Partnership (PLP) has
proposed to develop the Pebble copper-gold-molybdenum porphyry deposit as a surface mine in the
Bristol Bay watershed in southwest Alaska. The project (i.e., the 2020 Mine Plan) consists of four
primary components: the mine site, the port, the transportation corridor including concentrate and
water return pipelines, and the natural gas pipeline and fiber optic cable (PLP 2020b).2
As discussed in Section 4 of the recommended determination, USACE's Final Environmental Impact
Statement (FEIS) and Record of Decision (ROD) for the project estimate that the discharge of dredged or
fill material at the mine site would result in the permanent loss of approximately 2,113 acres of
wetlands and other waters and 99.7 miles of streams. Included in these permanent stream losses are
approximately 8.5 miles of documented anadromous fish streams (USACE 2020a and 2020b).3 Section 4
of the recommended determination also discusses how discharges of dredged or fill material for the
construction and routine operation of the 2020 Mine Plan would adversely affect approximately 29
miles of anadromous fish streams resulting from greater than 20 percent changes in average monthly
streamflow. In the recommended determination, EPA Region 10 finds that discharges of dredged or fill
material for the construction and routine operation of the 2020 Mine Plan would be likely to have
unacceptable adverse effects on anadromous fishery areas.
2.2 Importance of Affected Aquatic Resources
Section 3 of the recommended determination provides a detailed description of the importance of the
region's ecological resources. As discussed in Section 3 of the recommended determination, because of
its climate, geology, hydrology, pristine environment, and other characteristics, the Bristol Bay
watershed is home to abundant, diverse, and productive aquatic habitats (recommended determination:
Figure ES-1). These streams, rivers, wetlands, lakes, and ponds support world-class commercial,
2 EPA did not evaluate the ancillary project components along the transportation corridor or at the Diamond Point
port; therefore, this recommended determination does not address them.
3 Anadromous fishes are those that hatch in freshwater habitats, migrate to sea for a period of relatively rapid
growth, and then return to freshwater habitats to spawn. For the purposes of this recommended determination,
"anadromous fishes" refers only to Coho or Silver salmon (Oncorhynchus kisutch), Chinook or King salmon (O.
tshawytscha), Sockeye or Red salmon [O. nerka), Chum or Dog salmon [O. keta), and Pink or Humpback salmon
[O. gorbuscha). Impact values cited here come from the ROD, which provides updates to the impact values provided
in the FEIS.
Recommended Determination December 2022
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Appendix C
Technical Evaluation of Potential
Compensatory Mitigation Measures
subsistence, and recreational fisheries for multiple species of Pacific salmon, as well as numerous other
fish species valued as subsistence and recreational resources (recommended determination: Section
3.3).
The productivity and diversity of the watershed's aquatic habitats are closely tied to the productivity
and diversity of its fisheries. The waters of the South Fork Koktuli River (SFK), North Fork Koktuli River
(NFK), and Upper Talarik Creek (UTC) watersheds are important for maintaining the integrity,
productivity, and sustainability of the region's salmon and non-salmon fishery resources (recommended
determination: Sections 3.2 and 3.3). The Pebble deposit overlies portions of the SFK, NFK, and UTC
watersheds, and these areas would be most directly affected by mine development at the Pebble deposit.
Streams and lakes in the SFK, NFK, and UTC watersheds are ideal for maintaining high levels of fish
production, with clean, cold water, gravel substrates, and abundant areas of groundwater upwelling.
These conditions create preferred salmon spawning habitat and provide favorable conditions for egg
incubation and survival. Figure 4-3 of the recommended determination illustrates reported
distributions for all five species of Pacific salmon (Coho [Oncorhyrtchus kisutch], Chinook [0.
tshawytscha], Sockeye [0. nerka], Chum [0. keta], and Pink [0. gorbuscha]) in these three watersheds.
Streams and lakes in the SFK, NFK, and UTC watersheds also provide high-quality habitat for fishes, such
as Rainbow Trout (0. mykiss), Dolly Varden (Salvelinus malma), Arctic Grayling (Thymallus arcticus), and
Northern Pike (Esox lucius). Wetlands provide essential off-channel habitats that protect young Coho
Salmon and other species, as well as provide spawning areas for Northern Pike. All of these species
move throughout the region's freshwater habitats during their life cycles, and all are fished—
commercially, for subsistence use, and recreationally—in downstream waters. Thus, the intact
headwater-to-larger river systems found in the SFK, NFK, and UTC watersheds, with their associated
wetlands, help sustain the overall productivity of these fishery areas (recommended determination:
Sections 3.2 and 3.3).
Not only do the streams, wetlands, and ponds of the SFK, NFK, and UTC watersheds directly provide
habitat for salmon and other fishes, they also provide critical support for downstream habitats. By
contributing water, organic matter, and macroinvertebrates to downstream systems, these headwater
areas help maintain downstream habitats and fuel their fish productivity. Together, these functions—
direct provision of high-quality habitat and indirect provision of other resources to downstream
habitats—help support the valuable fisheries of the Bristol Bay watershed (recommended
determination: Section 3.2).
This support is vital in Coho, Chinook, and Sockeye salmon fisheries. Chinook Salmon are the rarest of
the North American Pacific salmon species but are a critical subsistence resource, particularly along the
Nushagak River. The SFK, NFK, and UTC watersheds support discrete populations of Sockeye Salmon
that are genetically programmed to return to specific localized reaches or habitats to spawn; they likely
do the same for Coho and Chinook salmon (recommended determination: Section 3.3.3). This portfolio
of multiple small populations is essential for maintaining the genetic diversity and, thus, the stability and
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productivity of the region's overall salmon stocks (i.e., the portfolio effect) (recommended
determination: Section 3.3.3).
2.3 Identifying the Appropriate Watershed Scale for
Compensatory Mitigation
As previously noted, the regulations regarding compensatory mitigation specifically state that
compensatory mitigation generally should occur within the same watershed as the impact site and in a
location where it is most likely to successfully replace lost functions and services (40 CFR 230.93(b)(1)).
For the impacts of the mine site associated with the 2020 Mine Plan, ecological functions and services
would be most directly affected in the SFK, NFK, and UTC watersheds. Accordingly, the most appropriate
geographic scale at which to compensate for any unavoidable impacts resulting from such a project
would be within these same watersheds, as these locations would offer the greatest likelihood that
compensation measures would replace the "suite of functions typically provided by the affected aquatic
resource" (40 CFR 230.93(c)(2), Yocom and Bernard 2013). An important consideration is that salmon
populations in these watersheds possess unique adaptations to local environmental conditions, as
suggested by recent research in the region (Olsen et al. 2003, Ramstad et al. 2010, Quinn et al. 2012,
Dann et al. 2012, Shedd et al. 2016, Brennan et al. 2019). Accordingly, maintenance of local
biocomplexity (i.e., salmon genetic, behavioral, and phenotypic variation) and the environmental
template upon which biocomplexity develops will be important for sustaining resilience of these
populations (Hilborn et al. 2003, Schindler et al. 2010, Griffiths et al. 2014, Brennan et al. 2019). Thus,
the most appropriate spatial scale and context for compensation would be within the local watersheds
where impacts on salmon populations occur.
If there are no practicable or appropriate opportunities to provide compensation in these watersheds,
exploring options in adjoining watersheds may be appropriate. However, defining the watershed scale
too broadly would likely fail to ensure that wetland, stream, and associated fish losses in the SFK, NFK,
and UTC watersheds would be addressed, because compensation in a different watershed(s) would not
reduce the severity of the impacts to aquatic resources in the affected watersheds. Similarly,
compensation in different watersheds would not address impacts to the subsistence fishery where users
depend on a specific temporal and spatial distribution of fish to ensure nutritional needs and cultural
values are maintained (EPA 2014: Chapter 12).
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During development and finalization of the Bristol Bay Assessment (BBA) between 2011 and 2014 and
review of an earlier 404(c) proposed determination regarding the Pebble deposit published in 2014,
PLP and other commenters suggested an array of measures as having the potential to compensate for
the nature and magnitude of adverse impacts on wetlands, streams, and fish from the discharge of
dredged or fill material associated with mining the Pebble deposit. This section provides a technical
evaluation of the likely efficacy, applicability, and sustainability of these additional measures in reducing
the unavoidable aquatic resource impacts estimated for the 2020 Mine Plan to an acceptable level. Since
mitigation bank and in-lieu fee program options are not available, all of these additional measures
would involve permittee-responsible compensatory mitigation.4
3.1 Permittee-Responsible Compensatory Mitigation
3.1.1 Compensation Measures Suggested within the SFK, NFK, and UTC
Watersheds
This section discusses specific suggestions for potential compensation measures within the SFK, NFK,
and UTC watersheds that were provided in the public and peer review comments on the BBA and 2014
Proposed Determination.
3.1.1.1 Increase Habitat Connectivity
Several commenters recommended actions to increase connectivity between aquatic habitats, which are
discussed in this section. Connectivity among aquatic habitats within stream networks is an important
attribute influencing the ability of mobile aquatic taxa to utilize the diversity and extent of habitats
within those networks. Within riverine floodplain systems, a complex array of habitats can develop that
express varying degrees of surface and sub-surface water connectivity to main channels (Stanford and
Ward 1993). In the study area, off-channel floodplain habitats can include side channels (both inlet and
outlet connections to main channel), various types of single-connection habitats including alcoves and
4 Mitigation banks and in-lieu fee programs are other mechanisms for satisfying compensatory mitigation
requirements that rely on third-party providers (40 CFR 230.92). Should a mitigation bank or in-lieu fee sponsor
pursue the establishment of mitigation bank or in-lieu fee program sites to address impacts of the nature and
magnitude estimated for the 2020 Mine Plan, they would encounter the same challenges described in Section 3 of
this appendix. Permittee-responsible mitigation means an aquatic resource restoration, establishment,
enhancement, and/or preservation activity undertaken by the permittee to provide compensatory mitigation for
which the permittee retains full responsibility (40 CFR 230.92).
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percolation channels, and pools and ponds with no surface connection to the main channel during
certain flow conditions (PLP 2011: Appendix 15.ID). Beavers (Castor canadensis) can be very important
modifiers and creators of habitat in these off-channel systems (Pollock et al. 2003, Rosell et al. 2005). As
a result of their morphology and variable hydrology, the degree of surface-water connectivity and the
ability of fish to move among floodplain habitats changes with surface water levels. Connectivity for fish
movement at larger spatial scales within watersheds is influenced by barriers to longitudinal
movements and migrations. Examples include dams and waterfalls.
Efforts to manage or enhance connectivity within aquatic systems have primarily focused on watersheds
altered by human activities, where land uses and water utilization have led to aquatic habitat
fragmentation. Specific activities to increase habitat connectivity within human-dominated stream-
wetland systems may include the following.
• Improving access around real or perceived barriers to migration (including dams constructed by
humans or beavers).
• Removing or retrofitting of road culverts.
• Excavating and engineering of channels to connect isolated wetlands and ponds to main channels.
• Reconnection of historic floodplains via levee removal or other channel engineering.
Within watersheds minimally affected by human activity, efforts to increase connectivity may include
creation of passage around barrier waterfalls to expand the availability of habitat for species like Pacific
salmon. Removal of human-created dams do not offer any opportunities for habitat improvement or
expansion in the Nushagak or Kvichak River watersheds because they are absent, so they are not
discussed further. As stated earlier, this is primarily a roadless area, so road stream crossing retrofits
presently offer few if any opportunities for habitat improvement or expansion within the SFK, NFK, and
UTC watersheds, but exist elsewhere in the larger Nushagak and Kvichak River watersheds and are
discussed in Section 3.1.2. Here, beaver dam removal and engineered connections to variably connected
floodplain habitats, and habitats upstream of barrier waterfalls are discussed. For each of these
measures, the potential applicability, suitability, and effectiveness as mitigation tools within the SFK,
NFK, and UTC watersheds are addressed.
3,1,1,1,1 Remove Beaver Dams
Two commenters suggested the removal of beaver dams as part of a potential compensation strategy
that included beaver management. Presumably, the rationale for this recommendation is that beaver
dams can block fish passage, limiting fish access to otherwise suitable habitat, thus, the removal of
beaver dams could increase the amount of available fish habitat. This rationale is based on early
research that led to the common fish management practice of removing beaver dams to protect certain
fish populations like trout (Salyer 1934, Reid 1952, in Pollock et al. 2004). However, more recent
research has documented numerous benefits of beaver ponds to fish populations and habitat (Murphy et
al. 1989, Pollock et al. 2003). For example, Bustard and Narver (1975) found that a series of beaver
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ponds on Vancouver Island had a survival rate for overwintering juvenile Coho Salmon that was twice as
high as the 35 percent estimated for the entire stream. Pollock et al. (2004) estimated a 61 percent
reduction in summer habitat capacity relative to historical levels, largely due to the loss of beaver ponds,
for Coho Salmon in one Washington watershed.
A recent review by Larsen et al. (2021) describes the extensive and complex ways in which beavers
modify stream ecosystems. Increases in habitat complexity and availability of ponded and productive
floodplain habitats associated with beaver activity can result in positive impacts on Sockeye, Coho, and
Chinook salmon, as well as Dolly Varden, Rainbow Trout, and Steelhead (Kemp et al. 2012). Using meta-
analysis and weight-of-evidence methodology, Kemp et al. (2012) showed that most (71.4 percent)
negative effects cited, such as low dissolved oxygen and impediment to fish movement, lack supportive
data and are speculative in nature, whereas the majority (51.1 percent) of positive impacts cited are
quantitative in nature and well supported by data. In addition to increased invertebrate (i.e., food)
production and habitat heterogeneity, the study cited the importance of beaver ponds as rearing habitat
due to the increased cover and protection that higher levels of woody material and overall structural
diversity provide. Other studies from the Pacific Northwest (Nickelson et al. 1992, Collen and Gibson
2001) and Alaska (Lang et al. 2006) have identified beaver ponds as excellent salmon rearing habitat
because they have high macrophyte cover, low flow velocity, and increased temperatures, and they trap
organic materials and nutrients. DeVries et al. (2012) describe a stream restoration approach that
attempts to mimic and facilitate beaver dam creation and the numerous positive benefits for stream
habitat and riparian enhancement. Studies in Oregon have shown that salmon abundance is positively
related to pool size, especially during low flow conditions (Reeves et al. 2011), and beaver ponds
provide particularly large pools. During winter, beaver ponds typically retain liquid water below the
frozen surface, providing refugia for species that overwinter in streams and off-channel habitats
(Nickelson et al. 1992, Cunjak 1996).
Beaver dams generally do not constitute significant barriers to salmonid migration, even though their
semi-permeability may temporarily limit fish movement during periods of low stream flow (Rupp 1955,
Card 1961, Pollock et al. 2003). Even when beaver dams impede fish movements, the effects are
typically temporary with higher flows from storm events ultimately overtopping them or blowing them
out (Leidholt-Bruner et al. 1992, Kemp et al. 2012). Even the temporary effect may be limited, when
seasonal rainfall is at least average (Snodgrass and Meffe 1998, Kemp et al. 2012). Adding to the body of
evidence, Pacific salmon and other migratory fish species commonly occur above beaver dams, including
above beaver dams in the study area (PLP 2011: Appendix 15.ID). Other surveys have documented both
adult and juvenile Sockeye Salmon, Steelhead, Cutthroat Trout, and char upstream of beaver dams
(Swales et al. 1988, Murphy et al. 1989, Pollock et al. 2003).
Beavers preferentially colonize headwater streams and off-channel habitats (Collen and Gibson 2001,
Pollock et al. 2003). An October 2005 aerial survey of active beaver dams in the mine site area mapped
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113 active beaver colonies (PLP 2011). PLP's Environmental Baseline Document (EBD) highlights the
significant role that beaver ponds are currently providing for Pacific salmon in this area:
[W]hile beaver ponds were relatively scarce in the mainstem UT [UTC], the off-channel habitat study
revealed a preponderance of beaver ponds in the off-channel habitats. As in the SFK watershed, beaver
ponds accounted for more than 90 percent of the off-channel habitat surveyed. Beaver ponds in the UT
provided habitat for adult spawning and juvenile overwintering for Pacific salmon. The water
temperature in beaver ponds in the UT was slightly warmer than in other habitat types and thus, beaver
ponds may represent a more productive habitat as compared to other mainstem channel habitat types.
(PLP2011)
The current body of literature describing the effects of beaver dams on salmonid species reports more
positive associations between beaver dam activity and salmonids than negative associations (Kemp et
al. 2012). Hence, removal of beaver dams as a means of compensatory mitigation could lead to a net
negative impact on salmonid abundance, growth, and productivity. Moreover, because the mine
footprint would eliminate or block several streams with active beaver colonies in the headwaters of the
NFK, the benefits provided by those habitats would be part of the suite of functions that compensatory
mitigation should aim to offset.
3.1.1.1.2 Connect Off-channel Habitats and Habitat Above Impassable Waterfalls
Off-channel habitats can provide important low-velocity rearing habitats for juvenile salmon and other
native fishes. Floodplain-complex habitats including beaver ponds, side channels, oxbow channels, and
alcoves can contribute significantly to juvenile salmonid rearing capacity (e.g., Beechie et al. 1994,
Ogston et al. 2015). Such habitats are a common feature of unmodified alluvial river corridors. These
habitats may express varying degrees of surface-water connectivity to main channels that depend on
streamflow stage and natural channel dynamics in unmodified rivers. Off-channel habitats may become
isolated from the main channel during certain streamflow conditions due to channel migration or
avulsion, and in highly dynamic channels, connectivity may change frequently during bed-mobilizing
events (Stanford and Ward 1993). This shifting mosaic of depositional and erosional habitats within the
floodplain creates a diverse hydraulic and geomorphic setting, contributing to biocomplexity (Amoros
and Bornette 2002). In river systems modified by human activity, isolation or elimination of off-channel
habitats has had severe impacts on salmon productivity (e.g., Beechie et al. 1994), and re-connection and
re-creation of off-channel habitats are now common tools for increasing juvenile salmonid habitat
capacity in those systems (Morley et al. 2005, Roni et al. 2006, Ogston et al. 2015).
Waterfalls or high-gradient stream reaches can prevent fish from accessing upstream habitats, due to
velocity barriers or drops that exceed passage capabilities of fish (Reiser et al. 2006). Waters upstream
of barriers may be devoid of all fish life or may contain resident fish species including genetically
distinct populations (e.g., Whiteley et al. 2010). Engineered passageways for fish around waterfalls have
been used to create access to upstream lakes or stream systems for fish, such as salmon. However, the
response of resident fish species to barrier removal and the colonization success of species from
downstream habitats may be context dependent and difficult to predict (Kiffney et al. 2009, Pess et al.
2014). Salmon population responses to a fishway in southeast Alaska depended on the species, and the
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ecological effects of fish passage on the upstream lake system and watershed are not fully understood
(Bryant et al. 1999). Burger et al. (2000) provide a well-documented history of colonization of Sockeye
Salmon in Frazer Lake, Alaska, above a historically impassable waterfall following passage installation
and planting of salmon eggs, fry, and adults above the barrier. Their study documents how differing
donor populations, each with different life-history characteristics, contributed differently toward the
establishment of populations in the newly accessible habitats (Burger et al. 2000). This study highlights
the importance of genetics and life history adaptations of source populations to colonization success.
Creating connectivity between parts of the river network that are naturally disconnected can have
adverse ecological effects, including impacts on resident vertebrate and invertebrate communities, as
well as disruptions to ecosystem processes. Introduction of fish to fishless areas can lead to altered
predator-prey interactions, food web changes, changes in algal production, nutrient cycling, and meta-
population dynamics of other vertebrate species (Section 3.1.2.5). For example, previous studies on the
introduction of trout species to montane, wilderness lakes have shown that introducing fish to fishless
lakes can have substantial impacts on nutrient cycles (Knapp et al. 2001). The risk of disruption to the
functions of naturally fishless aquatic ecosystems should be fully evaluated before these approaches are
used for the sole purpose of creating new fish habitat area.
The importance of spatial habitat configuration to stream salmonid ecology has been recognized by a
wide variety of systems (reviewed by Flitcroft et al. 2019). For example, Rosenfeld and co-authors
(Rosenfeld et al. 2008, Rosenfeld and Raeburn 2009) conducted a variety of experiments and
monitoring activities within a re-connected river meander in coastal British Columbia to explore the
relationship of salmon productivity to habitat features. Their work highlights the importance of habitat
configuration. In their study, spacing of pools (foraging habitats for fish) and riffles (source areas for
invertebrate prey) was an important factor influencing growth rates of juvenile Coho Salmon. Given the
high diversity of channel conditions within floodplain habitats in the SFK, NFK, and UTC watersheds
(PLP 2011), it is likely that fish responses to increased connectivity would be highly variable.
Rosenfeld et al. (2008) point out the importance of considering the full suite of factors that influence
habitat capacity and productivity when designing restoration or enhancement projects. For instance,
attempting to optimize habitat structure for one species may adversely affect species with differing
habitat preferences, as demonstrated by Morley et al. (2005) who found differential responses of
juvenile Steelhead and juvenile Coho Salmon to conditions in constructed and natural off-channel
habitats. Predator-prey relationships also need to be considered. Increased connectivity of off-channel
habitats has been proposed as a strategy for enhancing Northern Pike production in northern Canada
(Cott 2004). How increased connectivity in the project area would influence trophic relationships
among Northern Pike and salmonids is unknown, although introduced Northern Pike in other areas of
Alaska have the potential to reduce local abundances of salmonids via predation (Sepulveda et al. 2013).
Bryant et al. (1999) in their study of the effects of improved passage at a waterfall concluded that the
effects on food webs, trophic relationships, and genetics among resident and newly colonizing species
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were largely unknown. Rosenfeld and Raeburn (2009) emphasize the high degree of uncertainty
associated with channel design for enhanced fish productivity, stating the following:
...despite the enormous quantity of research on stream rearing salmonids and their habitat associations,
stream ecologists still lack a definitive understanding of the relationship between channel structure, prey
production and habitat capacity for drift-feeding fishes. (Rosenfeld and Raeburn 2009: Page 581)
Several commenters proposed that enhanced or increased connectivity of off-channel habitats or
habitats above waterfalls could provide fish access to the currently underutilized or inaccessible habitat.
This comment presumes that currently disconnected habitats would provide suitable mitigation sites.
Based on the above, multiple criteria would have to be met, and numerous assumptions would have to
be validated for these sites to qualify as effective mitigation sites. Given the examples of the challenges
of connectivity management, use of fishways at waterfalls, and engineered connections to off-channel
habitats there is a great deal of uncertainty regarding the efficacy and sustainability of such techniques
as compensatory mitigation in the affected watersheds. Further, there also appears to be a lack of
opportunities to implement such techniques. When evaluating what compensation measures could
reduce the severity of the adverse effects estimated for the 2020 Mine Plan in the Koktuli River
watershed,5 PLP ruled out all other potential measures aside from preservation stating that
"[Restoration, establishment, or enhancement projects within the identified watershed are not plentiful
enough in size or scale to mitigate for the identified acreage of direct and indirect impacts to be
mitigated" (PLP 2020c).
3.1.1.2 Increase Habitat Quality
EPA received comments about enhancing habitat quality. Addition of large structural elements, such as
wood and boulders to streams, has been a common stream habitat rehabilitation approach in locations
where stream habitats have been extensively simplified by mining, logging, and associated timber
transportation, or other disturbances (Roni et al. 2008). The goals of large-structure additions are
typically to create increased hydraulic and structural complexity and improve local-scale habitat
conditions for fish in streams that are otherwise lacking in rearing or spawning microhabitats. Properly
engineered structural additions to channels can increase hydraulic diversity, habitat complexity, and
retention of substrates and organic materials in channels. However, benefits for fish can be highly
variable and context-dependent (Roni 2019) and can be difficult to quantify (Richer et al. 2022, Rogers
et al. 2022). The unpredictability of beneficial biotic responses to stream structural enhancements is at
odds with perceptions by managers whose evaluations tend to be overtly positive—but usually based on
qualitative opinion rather than scientific observation (Jahnig et al. 2011). In addition, improperly sited
or engineered structural additions can fail to achieve desired effects or have adverse, unanticipated
consequences (e.g., via structural failure or scour and fill of sensitive non-target habitats (Frissell and
Nawa 1992), highlighting the need for appropriate design (Kondolf et al. 2007).
5 The most severe impacts of the 2020 Mine Plan are concentrated in the SFKand NFK watersheds, which are a part
of the Koktuli River watershed.
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Commenters proposed that the quality of stream habitats in the project area could be enhanced by
increasing habitat complexity through the addition of boulders or large wood to existing off-channel
habitats. Off-channel habitats can provide important low-velocity rearing habitats for juvenile salmon
and other native fishes. Floodplain-complex habitats including beaver ponds, side channels, oxbow
channels, and alcoves provide hydraulic diversity that can be important for fishes in variable flows
(Amoros and Bornette 2002, Rosenfeld et al. 2008). Beavers are a major player in the creation and
maintenance of these habitats in the study area (PLP 2011: Appendix 15.ID), as has been noted
elsewhere (Pollock et al. 2003, Rosell et al. 2005). Off-channel habitats also provide important foraging
environments, and can be thermally diverse, offering opportunities for thermoregulation or enhanced
bioenergetic efficiency (Giannico and Hinch 2003). Off-channel habitats are relatively frequent and
locally abundant in area streams and rivers, particularly in lower-gradient, unconstrained valley settings
and at tributary confluences (e.g., PLP 2011: Figure 15.1-15). PLP's EBD, Appendix 15.ID (PLP 2011)
contains an assessment of the natural fluvial processes creating and maintaining off-channel habitats
and their quality, quantity, and function in the SFK, NFK, and UTC watersheds, including mechanisms of
connectivity to the mainstem channels. The EBD (PLP 2011) provides background information that is
useful for evaluating the potential effectiveness of off-channel habitat modification.
Commenters proposed that off-channel habitats could also be improved by engineered modifications to
the depth, shoreline development ratio, and configuration of off-channel habitats to create better
overwintering habitat for juvenile salmon. The degree to which existing habitats could be enhanced to
improve survival of juvenile salmon as proposed by commenters, will depend on several considerations,
including an evaluation of factors known to influence the utilization, survival, and growth within these
habitats. These considerations are discussed below.
Off-channel habitats surveyed by PLP and other investigators reveal that patterns of occupancy and
density are high but variable among off-channel habitats (PLP 2011: Appendix 15.ID). Some of the
highest densities observed were within off-channel habitats, such as side channels and alcoves, but some
"isolated" pools held fish (PLP 2011: Appendix 15.ID). This variability could reflect variation in
suitability, access, or other characteristics of individual off-channel habitats. Juvenile salmonids require
a diverse suite of resources to meet habitat requirements—cover and visual isolation provided by
habitat complexity is one such resource. However, other critical resources include food, space, and
suitable temperatures and water chemistry (Quinn 2018). Habitat configuration within constructed
side-channel habitats can also strongly influence density, size, and growth of juvenile salmonids
(Rosenfeld and Raeburn 2009). Giannico and Hinch (2003) in experimental treatments in side channels
in British Columbia found that wood additions were beneficial to Coho Salmon growth and survival in
surface-water-fed side channels, but not in groundwater-fed channels. They attributed this effect to
differences in foraging strategy and bioenergetics of the juvenile Coho Salmon overwintering in the
channels. Additions of wood had no effect, or even possibly a detrimental effect, on Coho Salmon
survival in groundwater-fed side channels. These findings highlight the importance of understanding the
ecology, bioenergetics, and behavior of the species and life histories present within habitats that may be
quite diverse with regard to hydrology and geomorphology.
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It is not clear from current data that adding complexity would address any limiting factor within existing
off-channel habitats, or that additions of boulders and wood would enhance salmonid abundance or
survival. Placement of structures (e.g., boulders, large wood) within stream channels could also have
potential adverse consequences, including unanticipated shifts in hydraulic conditions that lead to bank
erosion or loss of other desirable habitat features. Sustainability of off-channel habitat modifications is
also in question. As stated in the EBD, off-channel habitats are a product of a dynamic floodplain
environment and "... are continually being created and destroyed" (PLP 2011: Appendix 15.ID; page 2).
Maintenance of engineered structures or altered morphologies of such habitats over the long term
would be a challenging task (Tullos et al. 2021). Observations from the EBD suggest that beavers are
already providing desired complexity:
... habitat mapping from this off-channel study shows that the beaver ponds contain extensive and
diverse habitats and dominate the active valley floor" and "...these off-channel habitats provide a critical
habitat component of freshwater rearing of Coho Salmon, and to a lesser extent, other anadromous and
resident species. (PLP 2011: Appendix 15.ID: Page 14)
3,1,1,3 Increase Habitat Quantity
EPA received comments about increasing habitat quantity. The creation of spawning channels and off-
channel habitats has been proposed as a means to compensate for lost salmon spawning and rearing
areas. The intent of a constructed spawning channel is to simulate a natural salmon stream by regulating
flow, gravel size, and spawner density (Hilborn 1992). Off-channel habitats maybe enlarged or modified
to alter habitat conditions and capacities for rearing juvenile salmonids. Examples include the many
spawning channels (Bonnell 1991) and off-channel habitats (Cooperman 2006) enhanced or created in
British Columbia and off-channel ponds rehabilitated by the City of Seattle (Hall and Wissmar 2004).
Off-channel spawning and rearing habitats can be advantageous to salmon populations by providing
diverse hydraulic and habitat characteristics. Redds constructed in these habitats may be less
susceptible to scour compared to main channel habitats due to flow stability provided by their
hyporheic or groundwater sources (Hall and Wissmar 2004). Moderated thermal regimes can provide
benefits for growth and survival for overwintering juveniles (Giannico and Hinch 2003). Morley et al.
(2005) compared 11 constructed off-channel habitats to naturally occurring paired reference side
channels and found that both natural and constructed off-channel habitats supported high densities of
juvenile salmonids in both winter and summer. Although numerous studies have documented short-
term or localized benefits of constructed off-channel habitats, ascertaining population-level effects is
much more difficult (Ogston et al. 2015). Any additional fry produced by spawning channels (if
successful) would require additional suitable habitat for juvenile rearing and subsequent life stages in
order to have a net positive effect on populations. In a notable study, Ogston et al. (2015) tracked
production of Coho Salmon smolts from rehabilitated floodplain habitats that had been extensively
modified by logging and observed a significant population-level increase in smolts. Hilborn (1992)
indicates that success, measured by increased production of adult fish from such channels, is
unpredictable and generally unmonitored. A notable exception is the study by Sheng et al. (1990), which
documented 2- to 8-fold increases in recruitment of Coho Salmon spawner production from
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groundwater-fed off-channel habitats. Sheng et al. (1990) stated that effectiveness would be greatest in
systems that currently lack adequate overwinter refuges. As with any rehabilitation strategy, population
responses will depend on whether factors actually limiting production are addressed (Gibeau et al.
2020). Additional research and monitoring would be important to quantify factors currently limiting
production within project area watersheds.
Replacing destroyed salmon habitats with new constructed channels is also not a simple task. Factors
for consideration in designing and implementing off-channel habitat development are outlined in Lister
and Finnigan (1997), and include evaluation of species and life stages present, current habitat
conditions, and factors limiting capacity or productivity (Roni et al. 2008). Research indicates that
channels fed by hyporheic flow or groundwater may be most effective for creating suitable spawning
and rearing habitats (Lister and Finnigan 1997). Near-stream excavation and compaction associated
with channel construction can alter groundwater flowpaths, so designing projects to protect current
function and groundwater connectivity is important.
Numerous researchers have emphasized that replacing lost habitats is not merely a process of providing
habitat structure (Lake et al. 2007). Effective replacement of function also requires establishment of
appropriate food web structure and productivity to support the food supply for fish—in essence, an
entire ecosystem, including a full suite of organisms such as bacteria, algae, and invertebrates—needs to
be in place for a constructed channel to begin to perform some of the same functions of a destroyed
stream (Palmer et al. 2010, Bellmore et al. 2017). Quigley and Harper (2006b), in a review of stream
rehabilitation projects, concluded "the ability to replicate ecosystem function is clearly limited."
There is some history of using constructed spawning channels to mitigate for the impacts of various
development projects on fish, based on the premise that they would provide additional spawning
habitat and produce more fry, which would presumably result in more adult fish returning (Hilborn
1992). Off-channel rearing habitats have also been used to create additional overwintering habitats in
Pacific Northwest rivers (Roni et al. 2006), and spawning channels have also been shown to provide
suitable overwintering habitats for juvenile Coho Salmon (Sheng et al. 1990). Reliance on spawning
channels for fishery enhancement may also introduce unintended adverse consequences. Enhancement
of Sockeye Salmon via use of spawning channels in British Columbia's Skeena River has been
accompanied by the erosion of local diversity and homogenization of life history traits, leading to
possible losses in the spatial availability of salmon harvests to indigenous fisheries and local ecosystems
(Price et al. 2021). Constructed spawning channels, particularly those dependent on surface flow, may
also require annual maintenance and cleaning (Hilborn 1992), and salmon using them can be prone to
disease outbreaks (Mulcahy et al. 1982). Off-channel habitats to mainstems are also extremely difficult
to engineer in a way that can self-sustain in the face of a dynamic fluvial environment. Alluvial channels
frequently shift (Amoros and Bornette 2002), and beavers are highly effective ecosystem engineers
whose activities are constantly re-arranging floodplain channels and creating new dams (Pollock et al.
2003), including within engineered channels and culverts (Cooperman 2006).
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C-16
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In light of their uncertain track record, it does not appear that constructed spawning channels and
engineered connections of off-channel habitats would provide reliable and sustainable fish habitat in the
Bristol Bay region.
3.1.1.4 Manage Water Quantity
Two commenters suggested a variety of techniques to manipulate water quantities within the SFK, NFK,
and UTC watersheds to improve fish productivity. Possible techniques for accomplishing this include
flow management, flow augmentation, and flow pump-back.
3.1.1.4.1 Direct Excess On-site Water
Commenters suggested that fish habitat productivity could be improved through careful water
management at the mine site, including the storage and strategic delivery of excess water to streams and
aquifers to maintain or enhance flow and/or thermal regimes in the receiving streams. Delivering such
flows via groundwater (i.e., by using wastewater treatment plant (WTP) discharges to "recharge and
surcharge groundwater aquifers") was identified as a preferred approach; commenters argued doing so
would both render the measure less prone to operational anomalies at the WTP and better mimic
current natural flow patterns, thereby attenuating potential adverse effects related to discharge volume
and temperature. Ideally, flow, temperature, and habitat modeling would inform the design and
operation of flow management to optimize species and habitat benefits, for example, by providing water
at specific times to locations where low flow currently limits fish productivity.
Manipulation of surface flows at another mine in Alaska—Red Dog, in the northwest part of the state—
has resulted in an increase in fish (Arctic Grayling and Dolly Varden) use of the downstream creek
(Weber-Scannell 2005, Ott 2004). The circumstances at Red Dog, however, differ from those in the SFK,
NFK, and UTC area. As described in Weber-Scannell (2005), the near complete absence of fish in Red
Dog Creek prior to implementation of the water management techniques was the direct result of water
quality, not quantity, as the stream periodically experienced toxic levels of metals that occurred
naturally as it flowed through and downslope of the exposed ore body. Furthermore, the Red Dog water
management system primarily involves point-to-point diversion or transfer of surface, rather than
groundwater, both around the ore body and from tributaries upstream of the mine. Utilization of
managed aquifer surcharge or recharge to manage streamflows (e.g., Van Kirk et al. 2020) involves
significant complexities that may require spatially distributed numerical modeling and would still be
subject to considerable uncertainty (Ronayne et al. 2017), particularly in hydrologically complex areas
like the Pebble deposit site.
Given that most streams in the area support multiple salmonid species and life stages, with differing
habitat needs at different times, designing and managing a water delivery system to overcome limiting
factors for one or more species without adversely affecting others would be a significant challenge.
Given the complexity of the surface-groundwater connectivity in the watersheds draining the Pebble
deposit, ensuring that discharges to groundwater actually reached the target habitat at the intended
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C-17
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Compensatory Mitigation Measures
time would, perhaps, be the most difficult task. Quigley and Harper (2006b), in a review of stream
rehabilitation projects, concluded "the ability to replicate ecosystem function is clearly limited."
This challenge could be easier to overcome where habitat limitations occurred only as a result of mine
development, assuming pre-project modeling and verification accurately identified groundwater flow
paths to those areas. It is important to note, however, that even if such actions appeared to be feasible,
they likely would be required to avoid or minimize the adverse impacts of flow reduction due to mine
development, rather than to compensate for unavoidable habitat losses.
If it were an overall enhancement to pre-existing habitat, using WTP discharges to groundwater to
address natural limitation factors could be a form of compensatory mitigation. For example, PLP (2011)
points out that productivity may be limited by the existence of "losing" reaches along the SFK mainstem
and intermittent or ephemeral tributaries to both the SFK and NFK. Altering the natural flow regimes at
such sites, however, could have unintended consequences on the local ecosystem and species
assemblages (Poff et al. 1997). Moreover, "enhancing" these habitats through a WTP-sourced
groundwater flow delivery system would be even more challenging than managing flow to avoid or
minimize impacts to already productive habitat, because it would require "improving" the natural flow
delivery system that currently results in the periodic drying or low flows. Given that aquifer recharge for
streamflow management is a highly experimental approach to enhancing fish productivity, particularly
in a natural stream system there is a great deal of uncertainty regarding the efficacy and sustainability of
this technique as compensatory mitigation in the affected watersheds.
3,1,1,4,2 Augment Flows
Another means suggested for maintaining or increasing habitat productivity downstream of the mine
site is to increase flow volume into specific streams by creating new sources of surface flow or
groundwater recharge, specifically from impoundments or ice fields. EPA Region 10 is unaware of any
documented successful compensatory mitigation efforts to create impoundments or ice fields for the
benefit of salmonids. If there were potential locations for impoundments to manage flow in stream
reaches identified as having "sub-optimal" flow, logistical and environmental issues decrease the likely
efficacy and sustainability of such an approach. Manipulating streamflows in particular watersheds
would require diverting water from other basins or capturing water during peak flows for subsequent
release at other times, with the concomitant engineering, construction, and maintenance challenges.
Doing so would create additional adverse impacts from the construction of infrastructure and would be
subject to modeling and perpetual management sufficient to ensure that water withdrawals from the
"donor" watershed or from other times of the year would not adversely affect fish habitat and
populations in the donor watershed or the watershed's downstream waters. These concerns are in
addition to those commonly associated with impoundments, such as alteration of flow, thermal, and
sediment transport regimes.
Creating ice fields to increase the total volume of water available to a stream would also require water
diversion, with the same challenges and concerns related to building and maintaining system
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C-18
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Compensatory Mitigation Measures
infrastructure and reducing water volumes in the source watershed. Using ice fields to change the
timing of water availability would create issues related to managing the melt to produce stream flow at
the intended time (i.e., late summer or late winter low-flow periods). Moreover, because aquatic
organisms supported by a particular water body typically have evolved specific life history, behavioral,
and morphological traits consistent with the characteristics of that water body's natural flow regime,
local populations are inherently vulnerable to flow modification (Lytle and Poff 2004). Any use of ice
fields would face the potentially substantial challenges of the effects of climate change on ice production
and preservation. Given the logistical and environmental issues associated with this technique and the
lack of evidence of its use to benefit salmonids, it does not appear to be an effective or sustainable
approach to compensatory mitigation in the affected watersheds.
3,1,1,4,3 Pump Water Upstream
Another option suggested for making flow in some stream reaches more persistent is to pump
groundwater or surface water from a down-gradient site upstream to either a direct release point or a
recharge area. This technique has been used for fish habitat restoration at sites in the continental United
States, for example, the Umatilla River in Oregon (Bronson and Duke 2005), the Lower Owens River in
California (LADWP 2013), and Muddy Creek in Colorado (GrandRiver Consulting 2008, AECOM et al.
2012). However, EPA Region 10 is unaware of any documentation addressing its efficacy in increasing
salmonid productivity.
Even if potential source sites with sufficient water could be identified, this technique would require
substantial disturbance and additional environmental impacts associated with the construction of tens
of kilometers of water pipeline, power infrastructure, and access, along with maintenance of those
facilities in perpetuity. It would also entail active management to ensure that releases occur at
appropriate times to increase the persistence of flow in target streams without otherwise adversely
affecting their hydrographs or habitat. Such management would be another aspect of the approach that
would be perpetual. In total, this technique would involve a great deal of uncertainty with regard to both
efficacy and sustainability, making it a questionable mechanism for providing compensatory mitigation.
3,1,1,5 Manipulate Water Quality
Two commenters suggested that alteration of stream water chemistry would improve fish production in
the SFK, NFK, and UTC. They suggested increasing two groups of water chemistry parameters: basic
parameters such as alkalinity, hardness, and total dissolved solids, and nutrients such as nitrogen (N)
and phosphorous (P). This argument suggests that low concentrations of basic parameters or nutrients
limit algae production, thus, limiting aquatic macroinvertebrate production and habitat complexity. This,
in turn, can reduce overall fish production, reduce individual fish growth rates, or result in fish
movements away from low production areas.
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3.1.1.5.1 Increase Levels of Alkalinity, Hardness, and Total Dissolved Solids
PLP suggested in its 2014 comments that current levels of alkalinity, hardness, and total dissolved solids
(TDS) in the SFK, NFK, and UTC are suboptimal for fish production and could be manipulated to improve
fish production. PLP proposes "that streams with higher concentrations of total alkalinity, hardness, and
total dissolved solids, assuming no nutrient limitations due to low concentration of nitrogen or
phosphorus, produce a higher biomass per unit area than areas with lower concentrations" (PLP 2014,
Exhibit 6). However, PLP does not propose any actual mechanisms for fish habitat compensation via
increases in alkalinity, hardness, or TDS nor does it state its basis for assuming that N and P are not
limiting.
PLP proposed increasing levels of alkalinity, hardness, and TDS in streams as a compensation proposal
in its comments on the draft BBA (NDM 2013, Attachment D). In these comments, PLP refers to a
number of field studies of streams. The cited studies of stream manipulations that raise alkalinity,
hardness, or TDS are studies of the mitigation of acid mine drainage or of streams acidified by acid
deposition (Gunn and Keller 1984, Hasselrot and Hultberg 1984, Rosseland and Skogheim 1984,
Zurbuch 1984, Gagen et al. 1989, Lacroix 1992, Clayton et al. 1998, McClurg et al. 2007). The addition of
limestone or dolomite often increases the production of acidic streams, and alkalinity, hardness, and
TDS also increase, but the coincidence is not necessarily causal. It is more likely that the improvement is
due to reduced acidity or reduced dissolved metal concentrations, not to increased alkalinity, hardness,
or TDS per se. Other studies address the differences in the natural ability of streams to buffer natural or
anthropogenic acids. Streams with acidic inputs and high buffering capacity may have higher
productivity, as well as high alkalinity, hardness, and TDS. Other studies cited were not explicitly
acidified sites, but it was not clear what role, if any, alkalinity, hardness, or TDS played in reported
differences in productivity among those streams. Some of the studies are confounded by differences in
habitat, macronutrients, or other factors. Others suffer from pseudo-replication or low replication.
Further, PLP's comments (NDM 2013, Attachment D) do not support that such measures would be
effective. For example, it cites Scarnecchia and Bergersen (1987) as supporting the importance of
alkalinity, hardness, and TDS at the Pebble site (NDM 2013, Attachment D, Section 3.4.2.1). However,
Scarnecchia and Bergersen concluded the opposite. They found that most of the variance in productivity
and biomass was associated with elevation and the three chemical parameters were correlated with
elevation: "The overall weakness (despite statistical significance) of the correlations of chemical factors
with production suggested to us that physical factors strongly influence production in these streams.
Elevation, percentage of zero-velocity stations, and substrate diversity were the three most effective
combinations of variables for explaining variation in production."
Given the lack of a mechanism by which any of the three aggregated parameters would increase
productivity in the absence of acidity or high metal concentrations and inherent problems in the studies,
the causal nature of the reported field relationships is questionable. In any case, their relevance to
compensatory mitigation of the Pebble site has not been demonstrated.
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C-20
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Compensatory Mitigation Measures
The potential for unintended adverse consequences if alkalinity, hardness, or TDS are raised without an
understanding of the mechanisms of action and of the chemistry and biology of the receiving streams is
illustrated by studies that show impairment of stream communities in response to elevating one or
more of those parameters. In particular, the addition of limestone or dolomite to streams to mitigate
acid drainage and the filling of valleys with carbonaceous rock from mining have raised hardness,
alkalinity and TDS/conductivity, which have been shown to cause adverse and persistent effects on
stream invertebrate and fish communities (Weber-Scannell and Duffy 2007, Pond et al. 2008, Bernhardt
and Palmer 2011, Cormier et al. 2013a, Cormier et al. 2013b, Hopkins et al. 2013, Hitt and Chambers
2014, Morris et al. 2019).
3,1,1,5,2 Increase Levels of Nitrogen and/or Phosphorus
Commenters have also suggested that water quality could be manipulated by altering stream water
chemistry to increase levels of N and P where they are individually or co-limiting.
The commenters make recommendations about how to consider these factors when developing
mitigation in the SFK, NFK, and UTC. They suggest that the spatial distribution could focus on existing or
newly created side channels, sloughs, beaver ponds, alcoves, or, if necessary, the main channels at 10-km
intervals. They suggest several possible temporal distribution options, such as adding the nutrients only
during the growing season, potentially earlier, or all winter in open-water locations where biological
production continues year-round. They further indicate that the key considerations are access cost and
maintenance requirements. The commenters note that there are several types of nutrient delivery
methods: liquid fertilizer, slow-release fertilizer, and nutrient analogs (which are essentially slow-
release pellets of processed fish).
As support for their conclusion that lake and stream fertilization represent "demonstrably successful
mitigation techniques" for the SFK, NFK, and UTC, the commenters cite papers summarizing
experiments and case studies, as well as references to several management programs in the United
States, Canada, and northern Europe. These studies have examined the use of increased levels of
inorganic N and P, or fish carcasses, to improve ecosystem productivity and/or fish production.
The commenters assert that current levels of N and P in the SFK, NFK, and UTC are suboptimal for fish
production stating that benefits of fertilizing oligotrophic waters to stimulate fish production have been
demonstrated in many venues. Although numerous studies show an effect at one or more trophic levels
in response to fertilization, these studies are insufficient for drawing conclusions regarding the long-
term effectiveness of nutrient application to streams in the SFK, NFK, and UTC watersheds because they
lack scientific controls or have not been replicated, do not account for potential confounding factors,
were conducted in very different ecosystems, and/or only evaluated short-term effects. These
differences are discussed in the following paragraphs.
Commenters provided examples of experiments and studies aimed at increasing primary productivity
and theoretically salmon productivity. These studies assume that nutrients are the limiting factor
preventing increased salmon productivity, but that is not necessarily the case (Collins et al 2015).
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C-21
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Compensatory Mitigation Measures
Paleolimnetic studies in Alaska indicate nutrient inputs are not always tied to higher primary
productivity or salmon productivity (Chen et al. 2011). Wipfli and Baxter (2010) found that most fish
consume food from external or very distant sources, including from marine systems borne by adult
salmon, from fishless headwaters that transport prey to downstream fish, and from riparian vegetation
and associated habitats. An increase in food via nutrients may not overcome other limiting factors, such
as habitat availability or interspecies competition.
Most studies on stream and lake fertilization to increase productivity are short term in duration and
conducted in ecosystems with important differences from Bristol Bay (e.g., Perrin et al. 1987, Raastad et
al. 1993, Wipfli et al. 1998, Slaney et al. 2003). Many of the studies have been conducted in lakes (e.g.,
Bradford et al. 2000, Kyle 1994), which have different ecosystem dynamics from streams. Furthermore,
factors that limit populations in one habitat or time period may be different than in another (Collins et
al. 2015). Almost all of the stream studies are conducted in locations where salmon populations have
been negatively affected; therefore, the increased production is aimed at restoration, not enhancement,
of an existing healthy population.
Most studies are conducted between one and five years in duration, and a spike in productivity has been
seen in a number of these short-term studies. For example, the studies conducted at the Keogh and
Salmon Rivers (Ward et al. 2003, Slaney et al. 2003) examined the effect of nutrient supplement in the
form of salmon carcasses and inorganic N and P, respectively, in two coastal river systems for a period of
three years. Additionally, most studies quantify responses at the individual level, which may not
translate to an increase at the population level (Collins et al. 2015).
While a short-term spike in productivity is common, long-term studies call into question whether the
trend will be sustained over longer periods. Several papers cite results from the early years of the
longest-running study on stream fertilization located in the pristine Kuparuk River on the North Slope of
Alaska. This study raises concerns about using fertilization other than as an interim restorative measure.
While commenters cite a study capturing the increased size and growth rates of Arctic Grayling during
the first seven years of the study (Deegan and Peterson 1992), a subsequent paper documenting
conditions after 16 years found that persistent increased levels of N and P can result in dramatic
ecosystem shifts (Slavik et al. 2004). This long-term ecological research on the North Slope of Alaska
examined the effect of P input into P-limited streams, finding an increase in production for some species
at all trophic levels over the first few years. These results are similar to the studies finding improved fish
productivity in predominantly degraded systems cited extensively by commenters. However, after
approximately eight years of fertilization, a dramatic rise in moss (photos A and B) changed ecosystem
structure, affecting food and shelter availability (Slavik et al. 2004). Despite higher insect biomass in the
fertilized area during this period, there were no significant differences in fish growth rates between the
fertilized reach and the reference reach. The decrease in fish productivity was thought to result from the
effects of moss on preferred insect prey (Slavik et al. 2004, Gough et al. 2016). Following cessation of
nutrient enrichment, it took eight years of recovery to approach reference levels, after storms had
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C-22
December 2022
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Compensatory Mitigation Measures
scoured most remnant moss in the recovering reach, demonstrating that even at low concentrations,
sustained nutrient enrichment can have "dramatic and persistent consequences" (Benstead et al. 2007].
Photos showing the difference in bottom coverage between the diatom state (Photo A, left) and the
fertilized moss state (Photo B, right). Used with permission (Slavik et al, 2004).
Slavik et al. (2004) conclude that "[additional long-term whole stream fertilization studies are needed
to better understand the delayed stream ecosystem responses to nutrient enrichment. Even studies of
two to eight years in duration may be poor predictors of the long-term responses to added nutrients."
This conclusion is echoed in the most recent (2019) Long Term Ecological Research Network Decadal
Review Self Study (Groffman et al. 2019), which is a collection of papers reflecting study and
experimentation at diverse sites ranging from arctic and alpine tundra to grasslands, forests, streams,
wetlands, and lakes. In the paper addressing nutrient supply effects on ecosystems, the authors state,
"Long term observations and experiments at LTER sites have shown that short term patterns may have
little bearing on the ultimate direction and magnitude of nutrient effects, which can play out over many
decades" (Groffman et al. 2019: Page 23). The risks of long-term fertilization would also play out in the
context of global climate change, which is predicted to cause a release of phosphorous into streams from
melting permafrost (Hobbie et al. 1999), adding yet another layer to the unknowns.
In another study, long-term nutrient enrichment produced an unanticipated trophic decoupling
whereby enrichment continued to stimulate primary consumer production without a similar increase in
predator fish (Davis et al. 2010). The majority of the increased ecosystem productivity was confined to
lower trophic levels because the long-term enrichment primarily stimulated primary consumers that
were relatively resistant to predation. Based on these results, the authors concluded that "even in
ecosystems where energy flow is predicted to be relatively efficient, nutrient enrichment may still
increase the production of non-target taxa (e.g., predator or grazer resistant prey), decrease the
production of higher trophic levels, or lead to unintended consequences that may compromise the
productivity of freshwater ecosystems" (Davis et al. 2010).
These unanticipated results raise important questions about the potential consequences of long-term
nutrient supplementations. They also underscore the unpredictability of nutrient additions on the food
web, and the greater likelihood of unintended consequences as the effects ripple through complex
interactions between species. These implications are relevant considerations for potential long-term
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C-23
December 2022
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Compensatory Mitigation Measures
mitigation, which would be necessary for the SFK, NFK, and UTC. If long-term nutrient addition were to
cause an ecosystem shift at lower trophic levels in the SFK, NFK, and UTC, effects on higher trophic
levels including the productivity of salmon and other target fish species are unknown.
Studies examining the relationship between salmon carcasses and productivity at various trophic levels
are another active area of investigation. Some research provides evidence that carcasses are superior to
inorganic nutrient amendments for sustaining and restoring stream productivity, including fish
production, potentially because inorganic nutrients lack biochemicals and macromolecules that are
utilized directly by consumers (Wipfli et al. 2010, Martin et al. 2010, Heintz et al. 2010). Others have
found the effects of carcasses can be transient, localized, and variable with no increase in fish growth
(Cram et al. 2011). Few studies have documented the long-term impacts of carcass addition, and there
are many remaining gaps in understanding the efficacy of this method of potentially improving salmon
productivity. In addition, a number of authors express concern about the potential for the spread of
toxins and pathogens when carcasses are used as the supplemental nutrient source (Compton et al.
2006).
Authors of many of these studies state that the application of their results are relevant and appropriate
for salmonid restoration in streams or lakes with depressed numbers (e.g., Larkin and Slaney 2011). The
authors do not describe their results as informing methods to manipulate existing unaltered wild
systems to further augment salmon production. Although some commenters draw heavily from Ashley
and Stockner (2003) to support their recommendation to use this as a method of mitigation in the SFK,
NFK, and UTC watersheds, the authors of that study state the following:
The goal of stream and lake enrichment is to rebuild salmonid escapement to historical levels via
temporary supplementations of limiting nutrients using organic and/or inorganic formulations. Stream
and lake enrichment should not be used as a 'techno-fix' to perpetuate the existing mismanagement of
salmonids when there is any possibility of re-establishing self-sustaining wild populations through
harvest reductions and restoration of salmonid habitat. Therefore, fertilization should be viewed as an
interim restorative measure that is most effective if all components of ecosystem recovery and key
external factors (e.g. overfishing) are cooperatively achieved and coordinated. This paper reviews some
of the technical and more applied aspects of stream, river, and lake enrichment as currently practiced in
British Columbia and elsewhere. As a caveat, the discussion assumes that salmonid stock status of
candidate lakes and streams has been quantified and classified as significantly depressed and that
additional limiting factors (e.g. habitat/water quality and quantity) have been addressed and/or
incorporated into an integrated basin or lake restoration plan. (Ashley and Stockner 2003: Page 246)
There are still many gaps in understanding the role of nutrients in fish productivity, so there is much
that is not known about whether nutrient addition can be a successful method to increase fish
productivity especially in the long term. Furthermore, much of the existing literature on which
commenters base their assertions rests on several untested assumptions (Collins et al. 2015).
Setting aside questions of scientific efficacy and applicability, there are also numerous practical
challenges inherent in nutrient addition as a potential mitigation method. Conducting a long-term
management protocol in remote waterways subject to extreme weather changes necessarily requires
careful monitoring of water chemistry, as well as other ecosystem parameters and precise application of
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C-24
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Compensatory Mitigation Measures
nutrients, which calls into question the sustainability of altering stream water chemistry to improve the
fish production.
At this time, there are no scientific studies showing how an increase in nutrients resulting in increased
salmon productivity can be reliably achieved on a long-term basis in the SFK, NFK, and UTC watersheds
or the larger Bristol Bay ecosystem without risk to the region's existing robust populations. Just as for
the addition of non-nutrients, such as limestone, manipulating stream chemistry in this largely
unaltered ecosystem through the addition of N and P would be a challenging and difficult experiment
with many negative outcomes being possible.
3.1.2 Other Potential Compensation Measures Suggested within the
Nushagak and Kvichak River Watersheds
As noted above, if practicable or appropriate opportunities to provide compensation within the SFK,
NFK, or UTC watersheds are non-existent or limited, it may be appropriate in certain circumstances to
explore options in adjoining watersheds. For example, there are a few scattered degraded sites in more
distant portions of the Nushagak and Kvichak River watersheds that could potentially benefit from
restoration or enhancement. This section discusses specific suggestions for other potential
compensation measures within the Nushagak and Kvichak River watersheds that were provided in the
public and peer review comments on the BBA and in response to the 2014 Proposed Determination.
3.1.2.1 Remediate Old Mine Sites
The U.S. Geological Survey identifies four small mine sites within the Nushagak and Kvichak River
watersheds: Red Top (in the Wood River drainage), Bonanza Creek (a Mulchatna River tributary),
Synneva or Scynneva Creek (a Bonanza Creek tributary), and Portage Creek (in the Lake Clark drainage)
(USGS 2008, 2012). These sites could provide opportunities for performing ecological restoration or
enhancement. However, due to their relatively small size and distant location, it is unlikely that these
sites could provide sufficient restored or enhanced acreage or ecological function to reduce the adverse
effects of the 2020 Mine Plan to an acceptable level. Further, some mitigation measures have already
occurred at these mines; for example, there have been some remediation activities at Red Top mine,
although traces of mercury and diesel-range organics remain in soils (BLM 2000). Resolution of liability
and contamination issues at these old mines would be necessary before they could serve as
compensatory mitigation sites for other projects. In its comments on the 2014 Proposed Determination,
PLP rejected this as a potential compensation measure, in part, due to concerns regarding the resolution
of these kinds of liability issues (PLP 2014: Exhibit 2).
3.1.2.2 Remove Roads
Another potential type of restoration within the Nushagak and Kvichak River watersheds is the removal
of existing or abandoned roads. As described in detail in EPA 2014, Appendix G, roads have persistent,
multifaceted impacts on ecosystems and can strongly affect water quality and fish habitat. Common
long-term impacts from roads include (1) permanent loss of natural habitat; (2) increased surface runoff
Recommended Determination
C-25
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Compensatory Mitigation Measures
and reduced groundwater flow; (3) channelization or structural simplification of streams and hydrologic
connectivity; (4) persistent changes in the chemical composition of water and soil; (5) disruption of
movements of animals, including fishes and other freshwater species; (6) aerial transport of pollutants
via road dust; and (7) disruption of near-surface groundwater processes, including interception or re-
routing of hyporheic flows, and conversion of subsurface slope groundwater to surface flows
(Trombulak and Frissell 2000, Forman 2004). Road removal, thus, could facilitate not only the
reestablishment of former wetlands and stream channels, but also the enhancement of nearby aquatic
resources currently degraded by the road(s).
Commenters did not offer specific suggestions for potential road-removal sites. As EPA 2014 Appendix G
highlights, the Nushagak and Kvichak River watersheds are almost entirely roadless areas (EPA 2014,
Appendix G, Figure 1). Further, it is unlikely that local communities would support removal of any
segments of the few existing roads in the watersheds. Thus, it appears there are very few, if any, viable
opportunities to provide environmental benefits through road removal.
3.1.2.3 Retrofit Road Stream Crossings
Another potential type of enhancement within the Nushagak and Kvichak River watersheds is to retrofit
existing road stream crossings to improve fish passage through these human-made features. Stream
crossings can adversely affect spawning, rearing (Sheer and Steel 2006, Davis and Davis 2011), and
refuge habitats (Price et al. 2010), as well as reduce genetic diversity (Wofford et al. 2005, Neville et al.
2009). These changes can, in turn, reduce long-term sustainability of salmon populations (Hilborn et al.
2003, Schindler et al. 2010). Blockage or inhibition of fish passage is a well-documented problem
commonly associated with declines in salmon and other fish populations in many regions of the United
States (Nehlsen et al. 1991, Bates et al. 2003), including Alaska (ADF&G 2022).
Removing and replacing crossings that serve as barriers to fishes could improve fish passage and re-
open currently inaccessible habitat. However, as noted in Section 3.1.2.2, the Nushagak and Kvichak
River watersheds are almost entirely roadless areas and, thus, likely offer few, if any, viable
opportunities to provide the extent of environmental benefits necessary to reduce the adverse effects of
the 2020 Mine Plan to an acceptable level. Further, prior to concluding that any effort to retrofit existing
stream crossings would be appropriate compensatory mitigation, it would first be necessary to
determine that no other party has responsibility for the maintenance of fish passage at those stream
crossings (e.g., through the terms or conditions of a Section 404 permit that authorized the crossing).
After initially proposing this as a potential compensation measure, in its comments on the 2014
Proposed Determination, PLP rejected this measure due to "the long term liability involved as PLP
would be responsible for effectiveness in perpetuity, possible requiring monitoring and maintenance
(including repair and replacement)" (PLP 2014: Exhibit 2).
3.1.2.4 Construct Hatcheries
One commenter referenced the potential use of hatcheries as a compensation measure. Such a proposal
could be very problematic, particularly in the Bristol Bay watershed, where the current salmon
Recommended Determination
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Technical Evaluation of Potential
Compensatory Mitigation Measures
population is entirely wild. There are several concerns over the introduction of hatchery-produced
salmon to the Bristol Bay watershed.
Many of the potential risks associated with fish hatcheries concern reductions in fitness, growth, health,
and productivity that result from decreases in genetic diversity when hatchery-reared stocks hybridize
with wild salmon populations. Hatchery-raised salmon have lower genetic diversity than wild salmon
(Christie et al. 2011, Yu et al. 2012). Consequently, when hatchery-raised salmon hybridize with wild
salmon, the result can be a more genetically homogenous population, leading to decreases in genetic
fitness (Waples 1991). In some cases, wild populations can become genetically swamped by hatchery
stocks. Zhivitovsky et al. (2012) found evidence of such swamping in a wild Chum Salmon population in
Kurilskiy Bay, Russia, during a two-year period of high rates of escaped hatchery fish. This genetic
homogenization is of concern because hatchery-raised fish stocks are considered less genetically "fit"
and, therefore, could increase the risk of collapse of salmon fisheries. This concern is supported by Araki
et al. (2008); a review of 14 studies that suggests that nonlocal hatchery stocks reproduce very poorly in
the wild. The authors of this review also found that wild stocks reproduce better than both hatchery
stocks and wild, local fish spawned and reared in hatcheries.
Hatchery fish can also compete directly for food and resources with wild salmon populations in both
freshwater and marine environments (Rand et al. 2012a). Ruggerone et al. (2012) examined the effect
that Asian hatchery Chum Salmon have had on wild Chum Salmon in Norton Sound, Alaska, since the
early 1980s. They found that an increase in adult hatchery Chum Salmon abundance from 10 million to
80 million adult fish led to a 72 percent reduction in the abundance of the wild Chum Salmon
population. They also found smaller adult length-at-age, delayed age-at-maturation, and reduced
productivity were all associated with greater production of Asian hatchery Chum since 1965 (Ruggerone
et al. 2012). In addition to this competition for resources, hatchery-raised subyearling salmon can also
prey upon wild subyearling salmon, which tend to be smaller in size (Naman and Sharpe 2012).
Despite extensive efforts to restore federally listed Pacific Northwest salmon populations, these salmon
remain imperiled, and hatchery fish stocks may be a contributing stressor (Kostow 2009). Given the
exceptional productivity of the wild Bristol Bay salmon population, hatcheries would likely pose greater
ecological risks than benefits to this unique and valuable wild salmon population.
3,1,2,5 Stock Fish
Comments also mentioned stocking fish. Because many of the fish used in fish stocking originate in
hatcheries, fish stocking raises many of the same concerns as hatcheries and, thus, would also be a
problematic form of compensatory mitigation for the Bristol Bay region. Although stocking has been a
common practice in other regions, even in previously fishless habitats (e.g., Red Dog Mine, Alaska), a
large body of literature describes widespread adverse impacts of such management decisions. Fish
stocking throughout western North America and worldwide has affected other fish (Knapp et al. 2001,
Townsend 2003), nutrient cycling (Schindler et al. 2001, Eby et al. 2006, Johnson et al. 2010), primary
production (Townsend 2003, Cucherousset and Olden 2011), aquatic macroinvertebrates (Dunham et
Recommended Determination
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Technical Evaluation of Potential
Compensatory Mitigation Measures
al. 2004, Pope et al. 2009, Cucherousset and Olden 2011), amphibians (Pilliod and Peterson 2001, Finlay
and Vredenberg 2007), and terrestrial species (Epanchin et al. 2010). Although fish stocking has
provided limited benefits in certain circumstances, it would appear from the growing body of literature
that the ecological costs of fish stocking far outweigh any potential benefits.
3.2 Other Suggested Measures
Commenters also suggested that payments to organizations that support salmon sustainability or
investing in various public education, outreach, or research activities designed to promote salmon
sustainability could constitute potential compensatory mitigation for impacts on fish and other aquatic
resources. Although these initiatives can provide benefits in other contexts, compensatory mitigation for
impacts authorized under Section 404 of the CWA can only be provided through purchasing credits from
an approved mitigation bank or in-lieu fee program or conducting permittee-responsible compensatory
mitigation projects (40 CFR 230.92). One commenter also suggested reducing commercial fishery
harvests to compensate for fish losses due to large-scale mining; however, such a measure would also be
inconsistent with the definition of compensatory mitigation (40 CFR 230.92).
In its comments on the 2014 Proposed Determination, PLP (2014, Exhibit 2) provides a list of
compensation measures that it was not recommending, specifically culvert replacement, contaminated
site clean-up, landfill rehabilitation or replacement, and clean-up and restoration of legacy wells. In
deciding not to recommend these measures in 2014, PLP notes that "[t]he task to evaluate mitigation
actions in the Bristol Bay region included all opportunities available" and that the feasibility of these
opportunities was identified as "very expensive, high-risk, low compensatory credit return" and that
"[g]enerally, the main limitation to these permittee-responsible mitigation projects is a lack of
opportunity for restoration, establishment, and/or enhancement of wetlands within the Bristol Bay
region." PLP goes on to state that "[o]ther limitations to these permittee-responsible mitigation projects
include liability, cost, monitoring responsibilities in perpetuity, and the lack of infrastructure within the
Bristol Bay region to access existing opportunities" (PLP 2014: Exhibit 2).
Recommended Determination
C-28
December 2022
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¦CTIVENESS OF COMPENSATION
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M a i f 11" HH i* I!/»Tn3IM
In North America, 73 percent of fish extinctions are linked to habitat alterations (Miller et al. 1989).
Although extensive efforts have been undertaken to create or improve salmon habitat and prevent
fishery losses, all U.S. Atlantic salmon populations are endangered (NOAA 2022), 40 percent of Pacific
salmon in the lower 48 states are extirpated from historical habitats (NRC 1996), and one-third of
remaining populations are threatened or endangered with extinction (Nehlsen et al. 1991, Slaney et al.
1996, Gustafson et al. 2007). Coho and Chinook salmon are the two rarest of North America's five
species of Pacific salmon (Healey 1991) and have the greatest number of population extinctions among
the five species of Pacific salmon (Nehlsen et al. 1991, Augerot 2005). Approximately one-third of
Sockeye Salmon population diversity assessed by Rand et al. (2012b) was considered at risk of
extinction or extinct. Of remaining populations categorized as of "least concern," Bristol Bay Sockeye
Salmon likely represent the most abundant, diverse Sockeye Salmon populations left in the United
States.
Since 1990, a billion dollars has been spent annually on stream and watershed restoration in the United
States (Bernhardt et al. 2005). More than 60 percent of the projects completed during this period were
associated with salmon and trout habitat restoration efforts in the Pacific Northwest and California
(Katz et al. 2007). Despite the proliferation of projects and the significant funds being expended on these
efforts, debate continues over the effectiveness of various fish habitat restoration techniques and the
cumulative impact of multiple, poorly coordinated restoration actions at watershed or regional scales
(Reeves et al. 1991, Chapman 1996, Roni et al. 2002, Kondolf et al. 2008). However, in the Columbia
River Basin where billions of dollars have been spent on salmon and steelhead recovery efforts, a 2013
report indicates that some stream rehabilitation techniques, such as fish passage improvements, in-
stream wood and rock structures, livestock grazing controls, connection or construction of off-channel
habitat, and flow augmentation appear to be leading to fish habitat improvements in this basin where
logging, grazing, channelization, irrigation, development of urban areas, and construction and operation
of dams have led to extensive historic fish habitat loss and degradation (BPA 2013).
A 2014 review of 434 stream restoration, enhancement, and creation projects conducted to offset
impacts to Appalachian streams from surface coal mining authorized by CWA Section 404 permits
highlights the uncertain outcomes of stream mitigation projects (Palmer and Hondula 2014). Palmer
and Hondula (2014) found that even after five years of monitoring, 97 percent of projects reported
suboptimal or marginal habitat; they conclude that stream mitigation projects "are not meeting the
objectives of the Clean Water Act to replace lost or degraded streams ecosystems and their functions."
Recommended Determination C-29 December 2022
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Compensatory Mitigation Measures
In general, independent evaluations of the effectiveness of fish habitat compensation projects are rare
(Harper and Quigley6 2005b, Quigley and Harper 2006a, Quigley and Harper 2006b), and consequently
the long-term success rates and efficacy of such projects are not well known (DFO 1997, Lister and
Bengeyfield 1998, Lange et al. 2001, Quigley and Harper 2006a). A 2008 review of stream habitat
rehabilitation studies published worldwide found that "[d]espite locating 345 studies on effectiveness of
stream rehabilitation, firm conclusions about many specific techniques were difficult to make because of
the limited information provided on physical habitat, water quality, and biota and because of the short
duration and limited scope of most published evaluations" (Roni et al. 2005, Roni et al. 2008). Despite
these shortcomings, Roni et al. (2008) did find that some techniques, specifically, reconnection of
isolated habitats, floodplain rehabilitation, and instream habitat improvement, were proven to be
effective under numerous circumstances for improving habitat and increasing local fish abundance.
In its 2014 comments, PLP relies heavily on the findings of Roni et al. (2008) and BPA (2013) to support
the following positions.
• The effectiveness of the stream rehabilitation techniques PLP had proposed at that time for use at
the Pebble site is unequivocal and "settled science."
• These stream rehabilitation techniques should be expected to effectively rehabilitate streams
permanently lost or degraded by mining at the Pebble deposit.
• These stream rehabilitation techniques should also be expected to result in demonstrable
improvements in fish habitats in unaltered/undegraded streams that are currently part of an
ecosystem that supports some of the world's most productive wild salmon runs.
While PLP ultimately did not propose any of these measures during the CWA Section 404 permit review
process (PLP 2020a, 2020c), its application of the findings of Roni et al. (2008) and BPA (2013) is
inaccurate or oversimplified for the following reasons.
• Type of restoration is different. The effectiveness of the stream rehabilitation techniques
reviewed in these papers is not settled science, and the success of these approaches is highly
variable and context-dependent (Roni 2019); can be difficult to quantify (Richer et al. 2022, Rogers
et al. 2022); and must address the suite of factors influencing fish populations (water quality,
connectivity, hydrology, sediment, etc.).
• Impact is different. A large majority of the stream rehabilitation studies reviewed in these papers
were conducted in moderate climates, for streams that had been impacted by forestry, agriculture,
6 Dr. Jason Quigley, a scientist employed in 2014 by a company working to advance a mine at the Pebble deposit,
sent EPA Region 10 a letter dated April 28, 2014, indicating his concern that the BBA cited his work in a manner
that is "not fully accurate." EPA notes that the findings and conclusions of Dr. Quigley's earlier studies referenced by
the BBA are taken directly from Dr. Quigley's studies. Further, EPA clearly notes in this section that Quigley's earlier
studies highlight the need for improvements in compensation science, as well as institutional approaches, such as
better project planning, monitoring, and maintenance. Dr. Quigley's letter also notes that compensation success has
improved since his earlier studies; however, no examples of such documented success are included in his letter.
Recommended Determination
C-30
December 2022
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Appendix C
Technical Evaluation of Potential
Compensatory Mitigation Measures
roads, or human activities other than mining. The papers were not a review of rehabilitation of
streams impacted by mining. Where reviews of mined stream mitigation success have occurred in
Appalachia, monitoring revealed that 97 percent of the projects reported suboptimal or marginal
habitat (Palmer and Hondula 2014). These papers do not support use of these techniques to
rehabilitate streams permanently lost or degraded by mining at the Pebble deposit.
• Magnitude of restoration is likely not enough. There is little evidence that unaltered and high-
functioning habitats such as those in the affected watersheds can be made substantially better. Roni
and Beechie (2012) observed that when and where positive responses to restoration have been
observed, it has primarily been in systems where habitat had been greatly simplified due to land
clearing, road building, channelization, or other human activities (e.g., Ogston et al. 2015).
Furthermore, with the exception of downstream barrier removal (e.g., Pess et al. 2012) or barrier
modification, EPA Region 10 is aware of no instances where restoration approaches yielded
significant improvements in fish populations in highly functional watersheds with minimal human
modification. These papers do not support the position that existing unaltered/undegraded fish
habitats could somehow be improved by use of these techniques.
• Population response is not demonstrated. Even in watersheds where significant habitat
rehabilitation efforts have been undertaken, a corresponding salmon response at the population
scale has been elusive (Bennett et al. 2016).
• It is preferable to protect than to restore. Many authors have stated that based on lessons learned
regarding the difficulty of restoring fish habitat once it has been degraded, priority should always be
given to protecting existing high-quality habitat because it is much more effective and efficient to
protect than to restore (Beechie et al. 2008).
In Canada, the Department of Fisheries and Oceans evaluated the efficacy of fish habitat compensation
projects in achieving the conservation goal of no net loss (Harper and Quigley 2005a, Harper and
Quigley 2005b, Quigley and Harper 2006a, Quigley and Harper 2006b). Quigley and Harper (2006a)
showed that 67 percent of compensation projects resulted in net losses to fish habitat, 2 percent
resulted in no net loss, and only 31 percent achieved a net gain in habitat area. Quigley and Harper
(2006a) concluded that habitat compensation in Canada was, at best, only slowing the rate of fish
habitat loss. Quigley and Harper (2006b) showed that 63 percent of projects resulted in net losses to
aquatic habitat productivity, 25 percent achieved no net loss, and only 12 percent provided net gains in
aquatic habitat productivity. Quigley and Harper (2006b) concluded "the ability to replicate ecosystem
function is clearly limited."
Quigley and Harper (2006b) and Quigley et al. (2006) highlight the need for improvements in
compensation science, as well as institutional approaches, such as better project planning, monitoring,
and maintenance. Findings from Quigley and Harper (2006a and 2006b) are echoed in a 2016 study of
marsh and riparian habitat compensation projects constructed within the Fraser River Estuary from
Recommended Determination
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Technical Evaluation of Potential
Compensatory Mitigation Measures
1983 to 2011; this study found that only 33 percent of compensation sites were meeting biological and
functional goals, even after many decades (Lievesley et al. 2016).
Although there are clearly opportunities to improve the performance of fish habitat compensation
projects, Quigley and Harper (2006b) caution the following:
It is important to acknowledge that it is simply not possible to compensate for some habitats. Therefore,
the option to compensate for HADDs [harmful alteration, disruption or destruction to fish habitat] may not
be viable for some development proposals demanding careful exploration of alternative options including
redesign, relocation, or rejection.
Recommended Determination
C-32
December 2022
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PLP and other commenters suggested an array of measures over the past decade as having the potential
to compensate for adverse impacts on wetlands, streams, and fishes from the discharge of dredged or fill
material associated with mining the Pebble deposit. EPA Region 10 evaluated these measures for
informational purposes. Available information demonstrates that known compensation measures are
unlikely to adequately mitigate effects described in this recommended determination to an acceptable
level.
Recommended Determination
C-33
December 2022
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6.1 Citations
ADF&G (Alaska Department of Fish and Game. 2022. Fish Passage Improvement Program, Fish Passage
Inventory Projects. Available: http://www.adfg.alaska.gov/index.cfm?adfg=fishpassage.main.
Accessed: January 20, 2022.
AECOM, AMEC Earth and Environmental, Canyon Water Resources, Leonard Rice Engineers, and Stratus
Consulting. 2012. Colorado River Water Availability Study, Phase I Report. Prepared for the Colorado
Water Conservation Board. Available:
https://dnrweblink.state.co.us/CWCB/0/edoc/158319/CRWAS_March2012_CRWAS_Report_Final.p
df?searchid=dlb42ae8-2045-43ff-9659-08f88f71d09b. Accessed: January 21, 2022.
Ambrose, R. F., and S. F. Lee. 2004. An Evaluation of Compensatory Mitigation Projects Permitted under
the Clean Water Act Section 401 by the Los Angeles Regional Quality Control Board, 1991-2002.
California State Water Resources Control Board.
Amoros, C., and G. Bornette. 2002. Connectivity and biocomplexity in waterbodies of riverine
floodplains. Freshwater Biology 47:761-776.
Araki, H., B. A. Berejikian, M. J. Ford, and M. S. Blouin. 2008. Fitness of hatchery-reared salmonids in the
wild. Evolutionary Applications 1:342-355.
Ashley, K. L., and J. G. Stockner. 2003. Protocol for applying limiting nutrients to inland waters. Pages 245-
258 in J. Stockner (ed.), Nutrients in Salmonid Ecosystems: Sustaining Production and Biodiversity.
Symposium 34. Bethesda, MD: American Fisheries Society.
Augerot, X. 2005. Atlas of Pacific Salmon: The First Map-Based Status Assessment of Salmon in the North
Pacific. Portland, OR: University of California Press.
Bates, K., B. Barnard, B. Heiner, J. P. Klavis, and P. D. Powers. 2003. Design of Road Culverts for Fish
Passage. Olympia, WA: Washington Department of Fish and Wildlife.
Beechie, T. J., E. Beamer, and L. Wasserman. 1994. Estimating coho salmon rearing habitat and smolt
production losses in a large river basin, and implications for habitat restoration. North American
Journal of Fisheries Management 14:797-811.
Beechie, T., G. Pess, and P. Roni. 2008. Setting river restoration priorities: a review of approaches and a
general protocol for identifying and prioritizing actions. North American Journal of Fisheries
Management 28:891-905.
Recommended Determination
C-34
December 2022
-------
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Technical Evaluation of Potential
Compensatory Mitigation Measures
Bellmore, J. R., J. R. Benjamin, M. Newsom, J. A. Bountry, and D. Dombroski. 2017. Incorporating food web
dynamics into ecological restoration: a modeling approach for river ecosystems. Ecological
Applications 27:814-832.
Bennett, S., G. Pess, N. Bouwes, P. Roni, R. E. Bilby, S. Gallagher, J. Ruzycki, T. Buehrens, K. Krueger, W.
Ehinger, J. Anderson, C. Jordan, B. Bowersox, and C. Greene. 2016. Progress and challenges of testing
the effectiveness of stream restoration in the Pacific Northwest using intensively monitored
watersheds. Fisheries 41:92-103.
Benstead, J. P., A. C. Green, L. A. Deegan, B. J. Peterson, K. Slavik, W. B. Bowden, and A. E. Hershey. 2007.
Recovery of three arctic stream reaches from experimental nutrient enrichment. Freshwater Biology
52:1077-1089.
Bernhardt, E. S., and M. A. Palmer. 2011. The environmental costs of mountaintop mining valley fill
operations for aquatic ecosystems of the Central Appalachians. Pages 39-57 in R. S. Ostfeld and W. H.
Schlesinger (eds.), Year in Ecology and Conservation Biology.
Bernhardt, E. S., M. A. Palmer, J. D. Allan, G. Alexander, K. Barnas, S. Brooks, J. Carr, S. Clayton, C. Dahm, J.
Follstad-Shah, D. Galat, S. Gloss, P. Goodwin, D. Hart, B. Hassett, R. Jenkinson, S. Katz, G. M. Kondolf, P.
S. Lake, R. Lave, J. L. Meyer, T. K. O'Donnell, L. Pagano, B. Powell, and E. Sudduth. 2005. Synthesizing
US river restoration efforts. Science 308:636-637.
BLM (Bureau of Land Management). 2000. Statement of Work, Red Top Mill Site (Retort) Closure
Project.
Bonnell, R. G. 1991. Construction, operation, and evaluation of groundwater-fed side channels for chum
salmon in British Columbia. Pages 109-124 in J. Colt and R. J. White (eds.), Fisheries Bioengineering
Symposium. Bethesda, MD: American Fisheries Society Symposium 10.
BPA (Bonneville Power Administration). 2013. Benefits of Tributary Habitat Improvement in the
Columbia River Basin. Bonneville Power Administration, Bureau of Reclamation. Available:
http://www.salmonrecovery.gov/docs/Trib%20Benefits.pdf. Accessed: January 20, 2022.
Bradford, M. J., B. J. Pyper, and K. S. Shortreed. 2000. Biological responses of sockeye salmon to the
fertilization of Chilko Lake, a large lake in the interior of British Columbia. North American Journal of
Fisheries Management 20:661-671.
Brennan, S. R., D. E. Schindler, T. J. Cline, T. E. Walsworth, G. Buck, and D. P. Fernandez. 2019. Shifting
habitat mosaics and fish production across river basins. Science 364:783-786.
Bronson, J., and B. Duke. 2005. Umatilla River Fish Passage Operations Program, 2003-2004 Annual
Report, Project No. 198802200. BPA Report DOE/BP-00004112-4.
Recommended Determination
C-35
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Technical Evaluation of Potential
Compensatory Mitigation Measures
Bryant, M. D., B. J. Frenette, and S. J. McCurdy. 1999. Colonization of a watershed by anadromous
salmonids following the installation of a fish ladder in Margaret Creek, Southeast Alaska. North
American Journal of Fisheries Management 19:1129-1136.
Burger, C. V., K. T. Scribner, W. J. Spearman, C. 0. Swanton, and D. E. Campton. 2000. Genetic contribution
of three introduced life history forms of sockeye salmon to colonization of Frazer Lake, Alaska.
Canadian Journal of Fisheries and Aquatic Sciences 57:2096-2111.
Bustard, D. R., and D. W. Narver. 1975. Aspects of winter ecology of juvenile coho salmon (Oncorhynchus
kisutch) and steelhead trout (Salmo g air dneri). Journal of the Fisheries Research Board of Canada
32:667-680.
Chapman, D. W. 1996. Efficacy of structural manipulations of instream habitat in the Columbia River
basin. Northwest Science 5:279-293.
Chen, G. J., D. T. Selbie, B. P. Finney, D. E. Schindler, L. Bunting, P. R. Leavitt, and I. Gregory-Eaves. 2011.
Long-term zooplankton responses to nutrient and consumer subsidies arising from migratory
sockeye salmon Oncorhynchus nerka. Oikos 120:1317-1326.
Christie, M. R., M. L. Marine, R. A. French, and M. S. Blouin. 2012. Genetic adaptation to captivity can
occur in a single generation. Proceedings of the National Academy of Sciences of the United States of
America 109:238-242.
Clayton, J. E., E. S. Dannaway, R. Menendez, H. W. Rauch, J. J. Renton, S. M. Sherlock, and P. E. Zurbuch.
1998. Application of limestone to restore fish communities in acidified streams. North American
Journal of Fisheries Management 18:347-360.
Collen, P., and R. J. Gibson. 2001. The general ecology of beavers (Castor spp.), as related to their
influence on stream ecosystems and riparian habitats, and the subsequent effects on fish - a review.
Reviews in Fish Biology and Fisheries 10:439-461.
Collins, S. F., A. M. Marcarelli, C. V. Baxter, and M. S. Wipfli. 2015. A critical assessment of the ecological
assumptions underpinning compensatory mitigation of salmon-derived nutrients. Environmental
Management 56:571-586.
Compton, J. E., C. P. Andersen, D. L. Phillips, J. R. Brooks, M. G. Johnson, M. R. Church, W. E. Hogsett, M. A.
Cairns, P. T. Rygiewicz, B. C. McComb, and C. D. Shaff. 2006. Ecological and water quality
consequences of nutrient addition for salmon restoration in the Pacific Northwest. Frontiers in
Ecology and the Environment 4:18-26.
Cooperman, M. S., S. G. Hinch, S. Bennett, J. T. Quigley, R. V. Galbraith, and M. A. Branton. 2006. Rapid
Assessment of the Effectiveness of Engineered Off-Channel Habitats in the Southern Interior of British
Columbia for Coho Salmon Production. Canadian Manuscript Report of Fisheries and Aquatic Sciences
2768.
Recommended Determination
C-36
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Compensatory Mitigation Measures
Cormier, S. M., G. W. Suter, and L. Zheng. 2013a. Derivation of a benchmark for freshwater ionic strength.
Environmental Toxicology and Chemistry 32:263-271.
Cormier, S. M., G. W. Suter, L. Zheng, and G. J. Pond. 2013b. Assessing causation of the extirpation of
stream macroinvertebrates by a mixture of ions. Environmental Toxicology and Chemistry 32:277-
287.
Cott, P. A. 2004. Northern Pike (Esox lucius) Habitat Enhancement in the Northwest Territories. Canadian
Technical Report of Fisheries and Aquatic Sciences 2528.
Cram, J. M., P. M. Kiffney, R. Klett, and R. L. Edmonds. 2011. Do fall additions of salmon carcasses benefit
food webs in experimental streams? Hydrobiologia 675:197-209.
Cucherousset, J., and J. D. Olden. 2011. Ecological impacts of nonnative freshwater fishes. Fisheries
36:215-230.
Cunjak, R. A. 1996. Winter habitat of selected stream fishes and potential impacts from land-use activity.
Canadian Journal of Fisheries and Aquatic Sciences 53:267-282.
Dann, T. H., C. Habicht, J. R. Jasper, E. K. C. Fox, H. A. Hoyt, H. L. Liller, E. S. Lardizabal, P. A. Kuriscak, Z. D.
Grauvogel, and W. D. Templin. 2012. Sockeye Salmon Baseline for the Western Alaska Salmon Stock
Identification Project. Special Publication No. 12-12. Anchorage, AK: Alaska Department of Fish and
Game, Divisions of Sport Fish and Commercial Fisheries.
Davis, J. C., and G. A. Davis. 2011. The influence of stream-crossing structures on the distribution of
rearing juvenile Pacific salmon. Journal of the North American Benthological Society 30:1117-1128.
Davis, J. M., A. D. Rosemond, S. L. Eggert, W. F. Cross, and J. B. Wallace. 2010. Long-term nutrient
enrichment decouples predator and prey production. Proceedings of the National Academy of
Sciences of the United States of America 107:121-126.
Deegan, L. A., and B. J. Peterson. 1992. Whole river fertilization stimulates fish production in an Arctic
tundra river. Canadian Journal of Fisheries and Aquatic Sciences 49:1890-1901.
DeVries, P., K. L. Fetherston, A. Vitale, and S. Madsen. 2012. Emulating riverine landscape controls of
beaver in stream restoration. Fisheries 37:246-255.
DFO (Fisheries and Oceans Canada). 1997. No Net Loss: Assessing Achievement. Richmond, BC. Workshop
Proceedings. Richmond, BC: Kwantlen University College.
Dunham, J. B., D. S. Pilliod, and M. K. Young. 2004. Assessing the consequences of nonnative trout in
headwater ecosystems in western North America. Fisheries 29:18-26.
Eby, L. A., W. J. Roach, L. B. Crowder, and J. A. Stanford. 2006. Effects of stocking-up freshwater food
webs. Trends in Ecology & Evolution 21:576-584.
Recommended Determination
C-37
December 2022
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Compensatory Mitigation Measures
EPA (U.S. Environmental Protection Agency). 2014. An Assessment of Potential Mining Impacts on Salmon
Ecosystems of Bristol Bay, Alaska. Final Report. EPA 910-R-14-001. Washington, DC.
EPA and DOA (Department of the Army). 2018. Memorandum of Agreement Between the Department of
the Army and the Environmental Protection Agency Concerning Mitigation Sequence for Wetlands in
Alaska under Section 404 of the Clean Water Act. Available: https://www.epa.gov/cwa-
404/wetlands-mitigation-alaska. Accessed: January 18, 2022.
Epanchin, P. N., R. A. Knapp, and S. P. Lawler. 2010. Nonnative trout impact an alpine-nesting bird by
altering aquatic-insect subsidies. Ecology 91:2406-2415.
Finlay, J. C., and V. T. Vredenburg. 2007. Introduced trout sever trophic connections in watersheds:
Consequences for a declining amphibian. Ecology 88:2187-2198.
Flitcroft, R. L., I. Arismendi, and M. V. Santelmann. 2019. A review of habitat connectivity research for
Pacific salmon in marine, estuary, and freshwater environments. Journal of the American Water
Resources Association 55:430-441.
Forman, R. T. T. 2004. Road ecology's promise: What's around the bend? Environment 46:8-21.
Frissell, C. A., and R. K. Nawa. 1992. Incidence and causes of physical failure of artificial habitat
structures in streams of western Oregon and Washington. North American Journal of Fisheries
Management 12:182-197.
Gagen, C. J., W. E. Sharpe, and D. R. DeWalle. 1989. Pumping alkaline groundwater to restore a put-and-
take trout fishery in a stream acidified by atmospheric deposition. North American Journal of
Fisheries Management 9:92-100.
Gard, R. 1961. Effects of beaver on trout in Sagehen Creek, California. Journal of Wildlife Management
25:221-242.
Giannico, G. R., and S. G. Hinch. 2003. The effect of wood and temperature on juvenile coho salmon
winter movement, growth, density and survival in side-channels. River Research and Applications
19:219-231.
Gibeau, P., M. J. Bradford, and W. J. Palen. 2020. Can the creation of new freshwater habitat
demographically offset losses of Pacific salmon from chronic anthropogenic mortality? PLoS One 15:
e0237052.
Gough, L., N. D. Bettez, K. A. Slavik, W. B. Bowden, A. E. Giblin, G. W. Kling, J. A. Laundre, and G. R. Shaver.
2016. Effects of long-term nutrient additions on Arctic tundra, stream, and lake ecosystems: beyond
NPP. Oecologia 182:653-665.
GrandRiver Consulting Corporation. 2008.10825 Water Supply Alternatives Summary, Phase 2
Assessment (Draft).
Recommended Determination
C-38
December 2022
-------
Appendix C
Technical Evaluation of Potential
Compensatory Mitigation Measures
Griffiths, J. R., D. E. Schindler, J. B. Armstrong, M. D. Scheuerell, D. C. Whited, R. A. Clark, R. Hilborn, C. A.
Holt, S. T. Lindley, J. A. Stanford, and E. C. Volk. 2014. Performance of salmon fishery portfolios
across western North America. Journal of Applied Ecology 51:1554-1563.
Groffman, P., D. Burkepile, F. Davis, M. Downs, D. Foster, M. Gooseff, C. Gries, S. Hobbie, J. Lau, and J.
McClelland. 2019. Long Term Ecological Research Network Decadal Review Self Study. National
Science Foundation. Available: https://lternet.edu/wp-
content/uploads/2019/10/LTER_Self_Study_2019-10-04.pdf. Accessed: March 18, 2022.
Gunn, J. M., and W. Keller. 1984. In situ manipulation of water chemistry using crushed limestone and
observed effects on fish. Fisheries 9:19-24.
Gustafson, R. G., R. S. Waples, J. M. Myers, L. A. Weitkamp, G. J. Bryant, 0. W. Johnson, and J. J. Hard. 2007.
Pacific salmon extinctions: Quantifying lost and remaining diversity. Conservation Biology 21:1009-
1020.
Hall, J. L., and R. C. Wissmar. 2004. Habitat factors affecting Sockeye salmon redd site selection in off-
channel ponds of a river floodplain. Transactions of the American Fisheries Society 133:1480-1496.
Harper, D. J., and J. T. Quigley. 2005a. A comparison of the areal extent of fish habitat gains and losses
associated with selected compensation projects in Canada. Fisheries 30:18-25.
Harper, D. J., and J. T. Quigley. 2005b. No net loss of fish habitat: A review and analysis of habitat
compensation in Canada. Environmental Management 36:343-355.
Hasselrot, B., and H. Hultberg. 1984. Liming of acidified Swedish lakes and streams and its consequences
for aquatic ecosystems. Fisheries 9:4-9.
Healey, M. C. 1991. Life history of Chinook salmon (Oncorhynchus tshawytscha). Pages 311-393 in C.
Groot and L. Margolis (eds.), Pacific Salmon Life Histories. Vancouver, BC: UBC Press.
Heintz, R. A., M. S. Wipfli, and J. P. Hudson. 2010. Identification of marine-derived lipids in juvenile coho
salmon and aquatic insects through fatty acid analysis. Transactions of the American Fisheries Society
139:840-854.
Hilborn, R. 1992. Institutional learning and spawning channels for sockeye salmon (Oncorhynchus
nerka). Canadian Journal of Fisheries and Aquatic Sciences 49:1126-1136.
Hilborn, R., T. P. Quinn, D. E. Schindler, and D. E. Rogers. 2003. Biocomplexity and fisheries sustainability.
Proceedings of the National Academy of Sciences of the United States of America 100:6564-6568.
Hitt, N. P., and D. B. Chambers. 2014. Temporal changes in taxonomic and functional diversity of fish
assemblages downstream from mountaintop mining. Freshwater Science 33:915-926.
Recommended Determination
C-39
December 2022
-------
Appendix C
Technical Evaluation of Potential
Compensatory Mitigation Measures
Hobbie, J. E., B. J. Peterson, N. Bettez, L. Deegan, W. J. O'Brien, G. W. Kling, G. W. Kipphut, W. B. Bowden,
and A. E. Hershey. 1999. Impact of global change on the biogeochemistry and ecology of an Arctic
freshwater system. Polar Research 18:207-214.
Hopkins, R. L., B. M. Altier, D. Haselman, A. D. Merry, and J. J. White. 2013. Exploring the legacy effects of
surface coal mining on stream chemistry. Hydrobiologia 713:87-95.
Hough, P., and M. Robertson. 2009. Mitigation under Section 404 of the Clean Water Act: where it comes
from, what it means. Wetlands Ecology and Management 17:15-33.
Jahnig, S. C., A. W. Lorenz, D. Hering, C. Antons, A. Sundermann, E. Jedicke, and P. Haase. 2011. River
restoration success: a question of perception. Ecological Applications 21:2007-2015.
Johnson, C. R., C. Luecke, S. C. Whalen, and M. A. Evans. 2010. Direct and indirect effects of fish on pelagic
nitrogen and phosphorus availability in oligotrophic Arctic Alaskan lakes. Canadian Journal of
Fisheries and Aquatic Sciences 67:1635-1648.
Katz, S. L., K. Barnas, R. Hicks, J. Cowen, and R. Jenkinson. 2007. Freshwater habitat restoration actions in
the Pacific Northwest: A decade's investment in habitat improvement. Restoration Ecology 15:494-
505.
Kemp, P. S., T. A. Worthington, T. E. L. Langford, A. R. J. Tree, and M. J. Gaywood. 2012. Qualitative and
quantitative effects of reintroduced beavers on stream fish. Fish and Fisheries 13:158-181.
Kiffney, P. M., G. R. Pess, J. H. Anderson, P. Faulds, K. Burton, and S. C. Riley. 2009. Changes in fish
communities following recolonization of the Cedar River, WA, USA, by Pacific salmon after 103 years
of local extirpation. River Research and Applications 25:438-452.
Kihslinger, R. L. 2008. Success of wetland mitigation projects. Pages 14-16, National Wetlands
Newsletter. Washington, DC: Environmental Law Institute.
Knapp, R. A., P. S. Corn, and D. E. Schindler. 2001. The introduction of nonnative fish into wilderness
lakes: Good intentions, conflicting mandates, and unintended consequences. Ecosystems 4:275-278.
Kondolf, G. M., S. Anderson, R. Lave, L. Pagano, A. Merenlender, and E. S. Bernhardt. 2007. Two decades
of river restoration in California: What can we learn? Restoration Ecology 15:516-523.
Kondolf, G. M., P. L. Angermeier, K. Cummins, T. Dunne, M. Healey, W. Kimmerer, P. B. Moyle, D. Murphy,
D. Patten, S. Railsback, D. J. Reed, R. Spies, and R. Twiss. 2008. Projecting cumulative benefits of
multiple river restoration projects: an example from the Sacramento-San Joaquin River System in
California. Environmental Management 42:933-945.
Kostow, K. 2009. Factors that contribute to the ecological risks of salmon and steelhead hatchery
programs and some mitigating strategies. Reviews in Fish Biology and Fisheries 19:9-31.
Recommended Determination
C-40
December 2022
-------
Appendix C
Technical Evaluation of Potential
Compensatory Mitigation Measures
Kyle, G. B. 1994. Nutrient treatment of 3 coastal Alaskan lakes: trophic level responses and sockeye
salmon production trends. Alaska Fishery Research Bulletin 1:153-167.
LADPW (Los Angeles Department of Power and Water). 2013. Lower Owens River Project 2012 Final
Annual Report and other technical documents. Available:
https://www.ladwp.com/ladwp / faces/ladwp / aboutus/a-water/a-w-losangelesaqueduct/a-w-laa-
lowerowensriverproject;jsessionid=3gQySnNK47xJBClPXC9jTPlQbcwSLlr0pBLM105pHMs4h7ttpB
LX!501433091?_afrLoop=214361777610608&_afrWindowMode=0&_afrWindowId=null#%40%3F_
afrWindowId%3Dnull%26_afrLoop%3D214361777610608%26_afrWindowMode%3D0%26_adf.ct
rl-state%3Dukgc0122h_4- Accessed: January 21, 2022.
Lacroix, G. L. 1992. Mitigation of low stream pH and its effects on salmonids. Environmental Pollution
78:157-164.
Lake, P. S., N. Bond, and P. Reich. 2007. Linking ecological theory with stream restoration. Freshwater
Biology 52:597-615.
Lang, D. W., G. H. Reeves, J. D. Hall, and M. S. Wipfli. 2006. The influence of fall-spawning coho salmon
(iOncorhynchus kisutch) on growth and production of juvenile coho salmon rearing in beaver ponds
on the Copper River Delta, Alaska. Canadian Journal of Fisheries and Aquatic Sciences 63:917-930.
Lange, M., B. C. Cudmore-Vokey, and C. K. Minns. 2001. Habitat Compensation Case Study Analysis.
Canadian Manuscript Report on Fisheries and Aquatic Sciences 2576. Fisheries and Oceans Canada.
Larkin, G. A., and P. A. Slaney. 1997. Implications of trends in marine-derived nutrient influx to south
coastal British Columbia salmonid production. Fisheries 22:16-24.
Larsen, A., J. R. Larsen, and S. N. Lane. 2021. Dam builders and their works: Beaver influences on the
structure and function of river corridor hydrology, geomorphology, biogeochemistry and
ecosystems. Earth-Science Reviews 218:103623.
Leidholt-Bruner, K., D. E. Hibbs, and W. C. McComb. 1992. Beaver dam locations and their effects on
distribution and abundance of coho salmon fry in 2 coastal Oregon streams. Northwest Science
66:218-223.
Lievesley, M., D. Stewart, R. Knight, and B. Mason. 2016. Assessing Habitat Compensation and Examining
Limitations to Native Plan Establishment in the Lower Fraser River Estuary. British Columbia
Conservation Foundation and Community Mapping Network. Available: https://www.cmnbc.ca/wp-
content/uploads/2018/ll/Assessing-Habitat-Compensation_2016Appendix-I-IV.pdf. Accessed:
February 22, 2022.
Lister, D. B., and W. E. Bengeyfield. 1998. An Assessment of Compensatory Fish Habitat at Five Sites in the
Thompson River System. Canadian Manuscript Report of Fisheries and Aquatic Sciences 2444.
Recommended Determination
C-41
December 2022
-------
Appendix C
Technical Evaluation of Potential
Compensatory Mitigation Measures
Lister, D. B., and R. Finnigan. 1997. Rehabilitating off-channel habitat. Pages 7-1 to 7-29 in P. Slaney and
D. Zaldokas (eds.), Fish Habitat Rehabilitation Procedures. British Columbia Ministry of Environment,
Lands, and Parks, Watershed Restoration Program.
Lytle, D. A., and N. L. Poff. 2004. Adaptation to natural flow regimes. Trends in Ecology & Evolution
19:94-100.
Martin, A. E., M. S. Wipfli, and R. E. Spangler. 2010. Aquatic community responses to salmon carcass
analog and wood bundle additions in restored floodplain habitats in an Alaskan stream. Transactions
of the American Fisheries Society 139:1828-1845.
McClurg, S. E., J. T. Petty, P. M. Mazik, and J. L. Clayton. 2007. Stream ecosystem response to limestone
treatment in acid impacted watersheds of the Allegheny Plateau. Ecological Applications 17:1087-
1104.
Miller, R. R., J. D. Williams, and J. E. Williams. 1989. Extinctions of North American fishes during the past
century. Fisheries 14:22-&.
Morley, S. A., P. S. Garcia, T. R. Bennett, and P. Roni. 2005. Juvenile salmonid (Oncorhynchus spp.) use of
constructed and natural side channels in Pacific Northwest rivers. Canadian Journal of Fisheries and
Aquatic Sciences 62:2811-2821.
Morris, J. M., S. F. Brinkman, M. W. Carney, and J. Lipton. 2019. Copper toxicity in Bristol Bay headwaters:
Part 1-Acute mortality and ambient water quality criteria in low-hardness water. Environmental
Toxicology and Chemistry 38:190-197.
Mulcahy, D., J. Burke, R. Pascho, and C. K. Jenes. 1982. Pathogenesis of infectious hematopoietic necrosis
virus in adult sockeye salmon (Oncorhynchus nerka). Canadian Journal of Fisheries and Aquatic
Sciences 39:1144-1149.
Murphy, M. L., J. Heifetz, J. F. Thedinga, S. W. Johnson, and K. V. Koski. 1989. Habitat utilization by
juvenile Pacific salmon (Oncorhynchus) in the glacial Taku River, southeast Alaska. Canadian Journal
of Fisheries and Aquatic Sciences 46:1677-1685.
Naman, S. W., and C. S. Sharpe. 2012. Predation by hatchery yearling salmonids on wild subyearling
salmonids in the freshwater environment: A review of studies, two case histories, and implications
for management. Environmental Biology of Fishes 94:21-28.
NDM (Northern Dynasty Minerals Ltd.). 2013. Comments of Northern Dynasty Minerals on EPA 2013
Draft of the Bristol Bay Watershed Assessment, EPA Docket Number EPA-HQ-ORD-2013-0189.
Available: https://www.regulations.gov/. Accessed: January 20, 2022.
Nehlsen, W., J. E. Williams, and J. A. Lichatowich. 1991. Pacific salmon at the crossroads: stocks at risk
from California, Oregon, Idaho, and Washington. Fisheries 16:4-21.
Recommended Determination
C-42
December 2022
-------
Appendix C
Technical Evaluation of Potential
Compensatory Mitigation Measures
Neville, H., J. Dunham, A. Rosenberger, J. Umek, and B. Nelson. 2009. Influences of wildfire, habitat size,
and connectivity on trout in headwater streams revealed by patterns of genetic diversity.
Transactions of the American Fisheries Society 138:1314-1327.
Nickelson, T. E., J. D. Rodgers, S. L. Johnson, and M. F. Solazzi. 1992. Seasonal changes in habitat use by
juvenile coho salmon (Oncorhynchus kisutch) in Oregon coastal streams. Canadian Journal of
Fisheries and Aquatic Sciences 49:783-789.
NOAA (National Oceanic and Atmospheric Administration). 2022. Species Directory: Atlantic Salmon
(Protected). Available: http://www.nmfs.noaa.gov/pr/species/fish/atlanticsalmon.htm. Accessed:
January 21, 2022.
NRC (National Research Council). 1996. Upstream: Salmon and Society in the Pacific Northwest. National
Academy Press, Washington, DC.
NRC (National Research Council). 2001. Compensating for Wetland Losses under the Clean Water Act.
Washington, DC: National Academy Press.
Ogston, L., S. Gidora, M. Foy, and J. Rosenfeld. 2015. Watershed-scale effectiveness of floodplain habitat
restoration for juvenile coho salmon in the Chilliwack River, British Columbia. Canadian Journal of
Fisheries and Aquatic Sciences 72:479-490.
Olsen, J. B., S. J. Miller, W. J. Spearman, and J. K. Wenburg. 2003. Patterns of intra- and inter-population
genetic diversity in Alaskan coho salmon: Implications for conservation. Conservation Genetics
4:557-569.
Ott, A. G. 2004. Aquatic Biomonitoring at Red Dog Mine, 2003 (National Pollutant Discharge Elimination
Permit No. AK-003865-2). Technical Report 04-02. Alaska Department of Natural Resources, Office of
Habitat Management and Permitting.
Palmer, M. A., and K. L. Hondula. 2014. Restoration as mitigation: analysis of stream mitigation for coal
mining impacts in southern Appalachia. Environmental Science & Technology 48:10552-10560.
Palmer, M. A., H. L. Menninger, and E. Bernhardt. 2010. River restoration, habitat heterogeneity and
biodiversity: a failure of theory or practice? Freshwater Biology 55:205-222.
Perrin, C. J., M. L. Bothwell, and P. A. Slaney. 1987. Experimental enrichment of a coastal stream in British
Columbia: Effects of organic and inorganic additions on autotrophic periphyton production
Canadian Journal of Fisheries and Aquatic Sciences 44:1247-1256.
Pess, G. R., R. Hilborn, K. Kloehn, and T. P. Quinn. 2012. The influence of population dynamics and
environmental conditions on pink salmon (Oncorhynchus gorbuscha) recolonization after barrier
removal in the Fraser River, British Columbia, Canada. Canadian Journal of Fisheries and Aquatic
Sciences 69:970-982.
Recommended Determination
C-43
December 2022
-------
Appendix C
Technical Evaluation of Potential
Compensatory Mitigation Measures
Pess, G. R., T. P. Quinn, S. R. Gephard, and R. Saunders. 2014. Re-colonization of Atlantic and Pacific rivers
by anadromous fishes: linkages between life history and the benefits of barrier removal. Reviews in
Fish Biology and Fisheries 24:881-900.
Pilliod, D. S., and C. R. Peterson. 2001. Local and landscape effects of introduced trout on amphibians in
historically fishless watersheds. Ecosystems 4:322-333.
PLP (Pebble Limited Partnership). 2011. Pebble Project Environmental Baseline Document, 2004 through
2008. Anchorage, AK. Available: https://www.arlis.org/docs/vol2/Pebble/2004-2008EBDIndex.pdf.
PLP. 2014. Comments of the Pebble Limited Partnership on EPA Region 10's Proposed Determination
Pursuant to Section 404(c) of the Clean Water Act Regarding the Pebble Deposit Area, Southwest
Alaska, EPA Docket Number EPA-R10-OW-2014-0505. Available: https://www.regulations.gov/.
Accessed: January 20, 2022.
PLP. 2020a. Pebble Project Draft Compensatory Mitigation Plan for Department of the Army Application
for Permit POA-2017-00271 (January 2020 Draft).
PLP. 2020b. Pebble Project Department of the Army Application for Permit POA-2017-00271 (dated
June 8, 2020). Anchorage, AK.
PLP. 2020c. Pebble Project Draft Compensatory Mitigation Plan for Department of the Army Application
for Permit POA-2017-00271 (November 2020 Draft).
Poff, N. L., J. D. Allan, M. B. Bain, J. R. Karr, K. L. Prestegaard, B. D. Richter, R. E. Sparks, and J. C.
Stromberg. 1997. The natural flow regime: a paradigm for river conservation and restoration.
Bioscience 47:769-784.
Pollock, M. M., M. Heim, and D. Werner. 2003. Hydrologic and geomorphic effects of beaver dams and
their influence on fishes. The Ecology and Management of Wood in World Rivers 37:213-233.
Pollock, M. M., G. R. Pess, T. J. Beechie, and D. R. Montgomery. 2004. The importance of beaver ponds to
coho salmon production in the Stillaguamish River basin, Washington, USA. North American Journal
of Fisheries Management 24:749-760.
Pond, G. J., M. E. Passmore, F. A. Borsuk, L. Reynolds, and C. J. Rose. 2008. Downstream effects of
mountaintop coal mining: comparing biological conditions using family- and genus-level
macroinvertebrate bioassessment tools. Journal of the North American Benthological Society 27:717-
737.
Pope, K. L., J. Piovia-Scott, and S. P. Lawler. 2009. Changes in aquatic insect emergence in response to
whole-lake experimental manipulations of introduced trout. Freshwater Biology 54:982-993.
Price, D. M., T. Quinn, and R. J. Barnard. 2010. Fish passage effectiveness of recently constructed road
crossing culverts in the Puget Sound region of Washington State. North American Journal of Fisheries
Management 30:1110-1125.
Recommended Determination
C-44
December 2022
-------
Appendix C
Technical Evaluation of Potential
Compensatory Mitigation Measures
Price, M. H. H., J. W. Moore, B. M. Connors, K. L. Wilson, and J. D. Reynolds. 2021. Portfolio simplification
arising from a century of change in salmon population diversity and artificial production. Journal of
Applied Ecology 58:1477-1486.
Quigley, J. T., and D. J. Harper. 2006a. Compliance with Canada's Fisheries Act: A field audit of habitat
compensation projects. Environmental Management 37:336-350.
Quigley, J. T., and D. J. Harper. 2006b. Effectiveness of fish habitat compensation in Canada in achieving
no net loss. Environmental Management 37:351-366.
Quigley, J. T., D. J. Harper, and R. V. Galbraith. 2006. Fish Habitat Compensation to Achieve No Net Loss:
Review of Past Practices and Proposed Future Directions. Canadian Technical Report of Fisheries and
Aquatic Sciences 2632. Vancouver, BC: Fisheries and Oceans Canada, Habitat and Enhancement
Branch.
Quinn, T. P. 2018. The Behavior and Ecology of Pacific Salmon and Trout, 2nd Edition. Seattle, WA:
University of Washington Press.
Quinn, T. P., H. B. Rich, D. Gosse, and N. Schtickzelle. 2012. Population dynamics and asynchrony at fine
spatial scales: a case history of sockeye salmon (Oncorhynchus nerka) population structure in Alaska,
USA. Canadian Journal of Fisheries and Aquatic Sciences 69:297-306.
Raastad, J. E., A. Lillehammer, and L. Lillehammer. 1993. Effect of habitat improvement on Atlantic
salmon in the regulated River Suldalslagen. Regulated Rivers-Research & Management 8:95-102.
Ramstad, K. M., C. A. Woody, and F. W. Allendorf. 2010. Recent local adaptation of sockeye salmon to
glacial spawning habitats. Evolutionary Ecology 24:391-411.
Rand, P. S., C. Kellopn, X. Augerot, M. Goslin, J. R. Irvine, and G. T. Ruggerone. 2007. Comparison of
sockeye salmon (Oncorhynchus nerka) monitoring in the Fraser River Basin, British Columbia,
Canada and Bristol Bay, Alaska, USA. North Pacific Anadromous Fish Commission Bulletin 4:271-284.
Rand, P. S., B. A. Berejikian, A. Bidlack, D. Bottom, J. Gardner, M. Kaeriyama, R. Lincoln, M. Nagata, T. N.
Pearsons, M. Schmidt, W. W. Smoker, L. A. Weitkamp, and L. A. Zhivotovsky. 2012a. Ecological
interactions between wild and hatchery salmonids and key recommendations for research and
management actions in selected regions of the North Pacific. Environmental Biology of Fishes
94:343-358.
Rand, P. S., M. Goslin, M. R. Gross, J. R. Irvine, X. Augerot, P. A. McHugh, and V. F. Bugaev. 2012b. Global
assessment of extinction risk to populations of sockeye salmon Oncorhynchus nerka. PLoS One 7:
e34065.
Reeves, G. H., F. H. Everest, and J. R. Sedell. 1991. Rehabilitating and modifying stream habitats. Pages
519-557 inW. R. Meehan (ed.), Influences of Forest and Rangeland Management on Salmonid Fishes
and Their Habitats. Bethesda, MD: American Fisheries Society.
Recommended Determination
C-45
December 2022
-------
Appendix C
Technical Evaluation of Potential
Compensatory Mitigation Measures
Reeves, G. H., J. D. Sleeper, and D. W. Lang. 2011. Seasonal changes in habitat availability and the
distribution and abundance of salmonids along a stream gradient from headwaters to mouth in
coastal Oregon. Transactions of the American Fisheries Society 140:537-548.
Reid, K. A. 1952. The effect of beaver on trout waters. Maryland Conservationist 29:21-23.
Reiser, D. W., C. M. Huang, S. Beck, M. Gagner, and E. Jeanes. 2006. Defining flow windows for upstream
passage of adult anadromous salmonids at cascades and falls. Transactions of the American Fisheries
Society 135:668-679.
Richer, E. E., M. C. Kondratieff, G. Policky, M. D. Robinson, M. Atwood, and M. R. Myers. 2022. From gold
mining to gold medal fishery: evaluating the fishery response to stream restoration on the Upper
Arkansas River, Colorado. North American Journal of Fisheries Management 42:24-36.
Rogers, M., J. Selker, J. Peterson, and I. Arismendi. 2022. Identifying and quantifying sources of temporal
and spatial uncertainty in assessing salmonid responses to watershed-scale restoration. River
Research and Applications.
Ronayne, M. J., J. A. Roudebush, and J. D. Stednick. 2017. Analysis of managed aquifer recharge for
retiming streamflow in an alluvial river. Journal of Hydrology 544:373-382.
Roni, P. 2019. Does river restoration increase fish abundance and survival or concentrate fish? The
effects of project scale, location, and fish life history. Fisheries 44:7-19.
Roni, P., and T. Beechie. 2012. Stream and Watershed Restoration: A Guide to Restoring Riverine Processes
and Habitats. John Wiley & Sons.
Roni, P., T. J. Beechie, R. E. Bilby, F. E. Leonetti, M. M. Pollock, and G. R. Pess. 2002. A review of stream
restoration techniques and a hierarchical strategy for prioritizing restoration in Pacific northwest
watersheds. North American Journal of Fisheries Management 22:1-20.
Roni, P., K. Hanson, and T. Beechie. 2008. Global review of the physical and biological effectiveness of
stream habitat rehabilitation techniques. North American Journal of Fisheries Management 28:856-
890.
Roni, P., K. Hanson, T. Beechie, G. Pess, M. Pollock, and B. D. M. 2005. Habitat rehabilitation for inland
fisheries: Global review of effectiveness and guidance for rehabilitation of freshwater ecosystems. FAO
Fisheries Technical Paper 484. Rome, Italy: United Nations Food and Agriculture Organization.
Available: https://www.fao.Org/3/a0039e/a0039e00.htm. Accessed: January 20, 2022.
Roni, P., S. A. Morley, P. Garcia, C. Detrick, D. King, and E. Beamer. 2006. Coho salmon smolt production
from constructed and natural floodplain habitats. Transactions of the American Fisheries Society
135:1398-1408.
Rosell, F., 0. Bozser, P. Collen, and H. Parker. 2005. Ecological impact of beavers Castor fiber and Castor
canadensis and their ability to modify ecosystems. Mammal Review 35:248-276.
Recommended Determination
C-46
December 2022
-------
Appendix C
Technical Evaluation of Potential
Compensatory Mitigation Measures
Rosenfeld, J. S., and E. Raeburn. 2009. Effects of habitat and internal prey subsidies on juvenile coho
salmon growth: implications for stream productive capacity. Ecology of Freshwater Fish 18:572-584.
Rosenfeld, J. S., E. Raeburn, P. C. Carrier, and R. Johnson. 2008. Effects of side channel structure on
productivity of floodplain habitats for juvenile coho salmon. North American Journal of Fisheries
Management 28:1108-1119.
Rosseland, B. 0., and 0. K. Skogheim. 1984. Attempts to reduce effects of acidification on fishes in
Norway by different mitigation techniques. Fisheries 9:10-16.
Ruggerone, G. T., B. A. Agler, and J. L. Nielsen. 2012. Evidence for competition at sea between Norton
Sound chum salmon and Asian hatchery chum salmon. Environmental Biology of Fishes 94:149-163.
Rupp, R. S. 1955. Beaver-trout relationships in the headwaters of Sunkhaze Stream, Maine. Transactions
of the American Fisheries Society 84:75-85.
Salyer, J. C. 1.1934. Preliminary Report on the Beaver-Trout Investigation. Fisheries Research Report 259.
Michigan Department of Natural Resources, Fisheries Division.
Scarnecchia, D. L., and E. P. Bergersen. 1987. Trout production and standing crop in Colorado's small
streams, as related to environmental features. North American Journal of Fisheries Management
7:315-330.
Schindler, D. E., R. A. Knapp, and P. R. Leavitt. 2001. Alteration of nutrient cycles and algal production
resulting from fish introductions into mountain lakes. Ecosystems 4:308-321.
Schindler, D. E., R. Hilborn, B. Chasco, C. P. Boatright, T. P. Quinn, L. A. Rogers, and M. S. Webster. 2010.
Population diversity and the portfolio effect in an exploited species. Nature 465:609-612.
Sepulveda, A. J., D. S. Rutz, S. S. Ivey, K. J. Dunker, and J. A. Gross. 2013. Introduced northern pike
predation on salmonids in southcentral Alaska. Ecology of Freshwater Fish 22:268-279.
Shedd, K. R., T. H. Dann, H. A. Hoyt, M. B. Foster, and C. Habicht. 2016. Genetic Baseline of North American
Sockeye Salmon for Mixed Stock Analyses ofKodiak Management Area Commercial Fisheries, 2014-
2016. Fishery Manuscript Series No. 16-03. Anchorage, AK: Alaska Department of Fish and Game,
Divisions of Sport Fish and Commercial Fisheries.
Sheer, M. B., and E. A. Steel. 2006. Lost watersheds: Barriers, aquatic habitat connectivity, and salmon
persistence in the Willamette and Lower Columbia River basins. Transactions of the American
Fisheries Society 135:1654-1669.
Sheng, M., M. G. Foy, and A. Fedorenko. 1990. Coho Salmon Enhancement in British Columbia Using
Improved Groundwater-fed Side Channels. Canadian Manuscript Report of Fisheries and Aquatic
Sciences No. 2071. Department of Fisheries and Oceans, Salmonid Enhancement Program.
Recommended Determination
C-47
December 2022
-------
Appendix C
Technical Evaluation of Potential
Compensatory Mitigation Measures
Slaney, P. A., B. R. Ward, and J. C. Wrightman. 2003. Experimental nutrient addition to the Keogh River
and application to the Salmon River in coastal British Columbia. Pages 111-126 in J. Stockner (ed.),
Nutrients in Salmonid Ecosystems: Sustaining Production and Biodiversity. Symposium 34. Bethesda,
MD: American Fisheries Society.
Slaney, T. L., K. D. Hyatt, T. G. Northcote, and R. J. Fielden. 1996. Status of anadromous salmon and trout
in British Columbia and Yukon. Fisheries 21:20-35.
Slavik, K., B. J. Peterson, L. A. Deegan, W. B. Bowden, A. E. Hershey, and J. E. Hobbie. 2004. Long-term
responses of the Kuparuk River ecosystem to phosphorus fertilization. Ecology 85:939-954.
Snodgrass, J. W., and G. K. Meffe. 1998. Influence of beavers on stream fish assemblages: Effects of pond
age and watershed position. Ecology 79:928-942.
Stanford, J. A., and J. V. Ward. 1993. An ecosystem perspective of alluvial rivers: connectivity and the
hyporheic corridor Journal of the North American Benthological Society 12:48-60.
Sudol, M. F., and R. F. Ambrose. 2002. The US Clean Water Act and habitat replacement: Evaluation of
mitigation sites in Orange County, California, USA. Environmental Management 30:727-734.
Swales, S., F. Caron, J. R. Irvine, and C. D. Levings. 1988. Overwintering habitats of coho salmon
(iOncorhynchus kisutch) and other juvenile salmonids in the Keogh River system, British Columbia
Canadian Journal of Zoology 66:254-261.
Townsend, C. R. 2003. Individual, population, community, and ecosystem consequences of a fish invader
in New Zealand streams. Conservation Biology 17:38-47.
Trombulak, S. C., and C. A. Frissell. 2000. Review of ecological effects of roads on terrestrial and aquatic
communities. Conservation Biology 14:18-30.
Tullos, D., D. W. Baker, J. C. Curran, M. Schwar, and J. Schwartz. 2021. Enhancing resilience of river
restoration design in systems undergoing change. Journal of Hydraulic Engineering 147:03121001.
USACE (U.S. Army Corps of Engineers). 2020a. Pebble Project EIS: Final Environmental Impact
Statement Department of the Army Permit #POA-2017-00271.
USACE. 2020b. Record of Decision for Application Submitted by Pebble Limited Partnership to USACE
(Department of the Army Permit #POA-2017-00271).
USGS (U.S. Geological Survey). 2008. Alaska Resource Data File, New and Revised Records, Version 1.5.
USGS. 2012. Alaska Resource Data File.
Van Kirk, R. W., B. A. Contor, C. N. Morrisett, S. E. Null, and A. S. Loibman. 2020. Potential for managed
aquifer recharge to enhance fish habitat in a regulated river. Water 12:673.
Recommended Determination
C-48
December 2022
-------
Appendix C
Technical Evaluation of Potential
Compensatory Mitigation Measures
Waples, R. S. 1991. Genetic interactions between hatchery and wild salmonids: lessons from the Pacific
Northwest. Canadian Journal of Fisheries and Aquatic Sciences 48:124-133.
Ward, B. R., D. J. F. McCubbing, and P. A. Slaney. 2003. Evaluation of the addition of inorganic nutrients
and stream habitat structures in the Keogh River Watershed for steelhead trout and coho salmon.
Pages 127-147 in J. Stockner (ed.), Nutrients in Salmonid Ecosystems: Sustaining Production and
Biodiversity. Symposium 34. Bethesda, MD: American Fisheries Society.
Weber-Scannell, P. 2005. Comparison ofMainstem Red Dog Creek Pre-Mining and Current Conditions.
Scannell Technical Services.
Weber-Scannell, P. K., and L. K. Duffy. 2007. Effects of total dissolved solids on aquatic organisms: a
review of literature and recommendation for salmonid species. American Journal of Environmental
Sciences 3:1-6.
Whiteley, A. R., K. Hastings, J. K. Wenburg, C. A. Frissell, J. C. Martin, and F. W. Allendorf. 2010. Genetic
variation and effective population size in isolated populations of coastal cutthroat trout.
Conservation Genetics 11:1929-1943.
Wipfli, M. S., and C. V. Baxter. 2010. Linking ecosystems, food webs, and fish production: subsidies in
salmonid watersheds. Fisheries 35:373-387.
Wipfli, M. S., J. Hudson, and J. Caouette. 1998. Influence of salmon carcasses on stream productivity:
response of biofilm and benthic macroinvertebrates in southeastern Alaska, USA. Canadian Journal
of Fisheries and Aquatic Sciences 55:1503-1511.
Wipfli, M. S., J. P. Hudson, J. P. Caouette, N. L. Mitchell, J. L. Lessard, R. A. Heintz, and D. T. Chaloner. 2010.
Salmon carcasses increase stream productivity more than inorganic fertilizer pellets: A test on
multiple trophic levels in streamside experimental channels. Transactions of the American Fisheries
Society 139:824-839.
Wofford, J. E. B., R. E. Gresswell, and M. A. Banks. 2005. Influence of barriers to movement on within-
watershed genetic variation of coastal cutthroat trout. Ecological Applications 15:628-637.
Yocom, T. G., and R. L. Bernard. 2013. Mitigation of wetland impacts from large-scale hardrock mining in
Bristol Bay watersheds. Seattle Journal of Environmental Law 3:3.
Yu, J. N., N. Azuma, and S. Abe. 2012. Genetic differentiation between collections of hatchery and wild
masu salmon (Oncorhynchus masou) inferred from mitochondrial and microsatellite DNA analyses.
Environmental Biology of Fishes 94:259-271.
Zhivotovsky, L. A., L. K. Fedorova, G. A. Rubtsova, M. V. Shitova, T. A. Rakitskaya, V. D. Prokhorovskaya, B.
P. Smirnov, A. M. Kaev, V. M. Chupakhin, V. G. Samarsky, V. P. Pogodin, S. I. Borzov, and K. I.
Afanasiev. 2012. Rapid expansion of an enhanced stock of chum salmon and its impacts on wild
population components. Environmental Biology of Fishes 94:249-258.
Recommended Determination
C-49
December 2022
-------
Appendix C
Technical Evaluation of Potential
Compensatory Mitigation Measures
Zurbuch, P. E. 1984. Neutralization of acidified streams in West Virginia. Fisheries 9:42-47.
6.2 Additional Publications Reviewed
Ahearn, D. S., J. H. Viers, J. F. Mount, and R. A. Dahlgren. 2006. Priming the productivity pump: flood pulse
driven trends in suspended algal biomass distribution across a restored floodplain. Freshwater
Biology 51:1417-1433.
Alamaro, M. 1999. On the feasibility of generating and storing winter ice to meet water demands in the
summer. Mechanical Engineer's Degree Thesis, Massachusetts Institute of Technology, Cambridge
MA.
Alexander, R., E. Boyer, R. Smith, G. Schwarz, and R. Moore. 2007. The role of headwater streams in
downstream water quality. Journal of the American Water Resources Association 43:41-59.
Almodovar, A., G. G. Nicola, and B. Elivra. 2006. Spatial variation in brown trout production: the role of
environmental factors. Transactions of the American Fisheries Society 135:1348-1360.
Bailey, R. E. 1974. Development of recommendations for efficient use of catchable trout in West Virginia
(Part I) and development of a stream classification methodology for West Virginia (Part II). Master's
thesis. Virginia Polytechnic Institute and State University, Blacksburg, VA.
Baxter, J. S., and J. D. McPhail. 1999. The influence of redd site selection, groundwater upwelling, and
over-winter incubation temperature on survival of bull trout (Salvelinus confluentus) from egg to
alevin. Canadian Journal of Zoology 77: 1233-1239.
Beechie, T., H. Imaki, J. Greene, A. Wade, H. Wu, G. Pess, P. Roni, J. Kimball, J. Stanford, and P. Kiffney.
2013. Restoring salmon habitat for a changing climate. River Research and Applications 29:939-960.
Bernhardt, E. S., and M. A. Palmer. 2011. River restoration: the fuzzy logic of repairing reaches to reverse
catchment scale degradation. Ecological Applications 21: 1926-1931.
Binns, N. A. 1999. A compendium of trout stream habitat improvement projects done by the Wyoming
Game and Fish Department, 1953-1998. Cheyenne, WY: Wyoming Game and Fish Department, Fish
Division.
Bodznick, D. 1978. Calcium ion: an odorant for natural water discriminations and the migratory
behavior of sockeye salmon. Journal of Comparative Physiology 127:157-166.
Bond, M. H., Nodine, T. G., Beechie, T. J. and Zabel, R. W. 2019. Estimating the benefits of widespread
floodplain reconnection for Columbia River Chinook salmon. Canadian Journal of Fisheries and
Aquatic Sciences 76:1212-1226.
Borchardt, M. A. 1996. Nutrients. Pages 183-227 in RJ Stevenson, ML Bothwell, and RL Lowe, editors.
Algal ecology-freshwater benthic ecosystems. San Diego, CA: Academic Press Inc.
Recommended Determination
C-50
December 2022
-------
Appendix C
Technical Evaluation of Potential
Compensatory Mitigation Measures
Brown, T. G. and G. F. Hartman. 1988. Contribution of seasonally flooded lands and minor tributaries to
the production of coho salmon in Carnation Creek, British Columbia. Transactions of the American
Fisheries Society 117:546-551.
Cada, G. F., J. M. Loar, M. J. Sale. 1987. Evidence of food limitation of rainbow and brown trout in
Southern Appalachian soft-water streams. Transactions of the American Fisheries Society 116:692-
702.
Cederholm, C. J., M. D. Kunze, T. Murota, and A. Sibatani. 1999. Pacific salmon carcasses: essential
contributions of nutrients and energy for aquatic and terrestrial ecosystems. Fisheries 24:6-15.
Clark, I. D. and B. Lauriol. 1997. Aufeis of the Firth River Basin, Northern Yukon, Canada: Insights into
permafrost hydrogeology and karst. Arctic and Alpine Research 29:240-252.
Cleary, J., and D. Underhill. 2001. Annual compendium of aquatic rehabilitation projects for the Watershed
Restoration Program. Ministry of Water, Land and Air Protection, Ministry of Sustainable Resource
Management, and Ministry of Forests. Watershed Restoration Project No. 19.
Cordoleani, F., Phillis, C. C., Sturrock, A. M., FitzGerald, A. M., Malkassian, A., Whitman, G. E., Weber, P. K.
and Johnson, R.C., 2021. Threatened salmon rely on a rare life history strategy in a warming
landscape. Nature Climate Change 11:982-988.
Crozier, L. G., Burke, B. J., Chasco, B. E., Widener, D. L. and Zabel, R. W., 2021. Climate change threatens
Chinook salmon throughout their life cycle. Communications Biology 4:222.
Dekar, M. P., R. S. King, J. A. Back, D. F. Whigham, and C. M. Walker. 2012. Allochthonous inputs from
grass-dominated wetlands support juvenile salmonids in headwater streams: evidence from stable
isotopes of carbon, hydrogen, and nitrogen. Freshwater Science 31:121-132.
Dittman, A. H., T. P. Quinn, and G. A. Nevitt. 1995. Timing of imprinting to natural and artificial odors by
coho salmon, Oncorhynchus kisutch. Canadian Journal of Fisheries and Aquatic Sciences 53:434-442.
Dittman, A. H. and T. P. Quinn. 1996. Homing in Pacific salmon: mechanisms and ecological basis. Journal
of Experimental Biology 199:83-91.
Doucett, R. R., G. Power, D. R. Barton, R. J. Drimmie, and R. A. Cunjak. 1996. Stable isotope analysis of
nutrient pathways leading to Atlantic salmon. Canadian Journal of Fisheries and Aquatic Sciences
53:2058-2066.
Eberle, L. C. and J. A. Stanford. 2010. Importance and seasonal availability of terrestrial invertebrates as
prey for juvenile salmonids in floodplain spring brooks of the Kol River (Kamchatka, Russian
Federation). River Research and Applications 26:682-694.
Ebersole, J. L., P. J. Wigington Jr, J. P. Baker, M. A. Cairns, M. R. Church, B. P. Hansen, and S. G. Leibowitz.
2006. Juvenile coho salmon growth and survival across stream network seasonal habitats.
Transactions of the American Fisheries Society 135:1681-1697.
Recommended Determination
C-51
December 2022
-------
Appendix C
Technical Evaluation of Potential
Compensatory Mitigation Measures
Egglishaw, H. J. 1968. The quantitative relationship between bottom fauna and plant detritus in streams
of different calcium concentrations. Journal of Applied Ecology 5:731-740.
Freeman, M. C., C. M. Pringle, and C. R. Jackson. 2007. Hydrologic connectivity and the contribution of
stream headwaters to ecological integrity at regional scales. Journal of the American Water Resources
Association 43:5-14.
Gaboury, M., and R. Wong. 1999. A framework for conducting effectiveness evaluations of watershed
restoration projects. Province of British Columbia, Ministry of Environment, Lands and Parks, and
Ministry of Forests. Watershed Restoration Technical Circular No. 12.
Government of British Columbia. 2014. Policy for Mitigating Impacts on Environmental Values.
Available: https://www2.gov.bc.ca/assets/gov/environment/natural-resource-policy-
legislation/environmental-mitigation-policy/em_policy_mayl3_2014.pdf. Accessed: January 20,
2022.
Gresswell, R. E., C. E. Torgersen, D. S. Bateman, T. J. Guy, S. R. Hendricks, and J.E.B. Wofford. 2006. A
spatially explicit approach for evaluating relationships among coastal cutthroat trout, habitat, and
disturbance in small Oregon streams. American Fisheries Society Symposium 48:457-471.
Hartman, G. F., J. C. Scrivener, and M. J. Miles. 1996. Impacts of logging in Carnation Creek, a high energy
coastal stream in British Columbia, and their implication for restoring fish habitat. Canadian Journal
of Fisheries and Aquatic Sciences 53:237-251.
Hasler, A. D. and A. T. Scholz. 1983. Olfactory imprinting and homing in salmon. Berlin, New York, NY:
Springer-Verlag.
Hinterleitner-Anderson, D., A. E. Hershey, and J. A. Schuldt. 1992. The effects of river fertilization on
mayfly (Baetis sp.) drift patterns and population density in an arctic river. Hydrobiologia 240:247-
258.
Johnson, J. and P. Blanche. 2012. Catalog of Waters Important for Spawning, Rearing, or Migration of
Anadromous Fishes - Southwestern Region, Effective June 1, 2012. Special Publication No. 12-08.
Anchorage, AK: Alaska Department of Fish and Game.
Johnston, N. T., C. J. Perrin, P. A. Slaney, and B. R. Ward. 1990. Increased juvenile growth by whole-river
fertilization. Canadian Journal of Fisheries and Aquatic Sciences 47:862-872.
Johnston, N. T., and G. D. Moore. 1995. Guidelines for Planning Watershed Assessment Projects. Province of
British Columbia, Ministry of Environment, Lands and Parks, and Ministry of Forests. Watershed
Restoration Technical Circular No. 1.
Jones, L. A., E. R. Schoen, R. Shaftel, C. J. Cunningham, S. Mauger, D. J. Rinella, and A. St. Saviour. 2020.
Watershed-scale climate influences productivity of Chinook salmon populations across southcentral
Alaska. Global Change Biology 26:4919-4936.
Recommended Determination
C-52
December 2022
-------
Appendix C
Technical Evaluation of Potential
Compensatory Mitigation Measures
Hobbs, R. J., and D. A. Norton. 1996. Towards a conceptual framework for restoration ecology.
Restoration Ecology 4:93-110.
Hyatt, K. D., and G. J. Steer. 1987. Barkley Sound sockeye salmon (Oncorhyrtchus nerka) \ evidence for
over a century of successful stock development, fisheries management, research, and enhancement
effort. Pages 435-457 in H.D. Smith, L. Margolis, and C.C. Wood (eds.), Sockeye Salmon
fOncorhynchus nerkaj Population Biology and Future Management. Canadian Special Publication of
Fisheries and Aquatic Sciences 96.
Jungwirth, M., S. Muhar, and S. Schmutz. 2002. Re-establishing and assessing ecological integrity in
riverine landscapes. Freshwater Biology 47:867-887.
Keeley, E. R., P. A. Slaney, and D. Zaldokas. 1996. Estimates offish production benefits from stream
restoration initiatives. Province of B.C. Ministry of Environment, Lands and Parks, Watershed
Restoration Project Report 4, Vancouver, BC.
King, R. S., C. M. Walker, D. F. Whigham, S. Baird, and J. A. Back. 2012. Catchment topography and
wetland geomorphology drive macroinvertebrate community structure and juvenile salmonid
distributions in southcentral Alaska headwater streams. Freshwater Science 31:341-364.
King, S., and J. R. O'Hanley. 2016. Optimal fish passage barrier removal—revisited. River Research and
Applications 32:418-428.
Koch, D. L. and J. L. Hainline. 1976. Benthic macro-invertebrate populations in the Truckee River,
Nevada-California with reference to river flow and water. Water Resources Center, Desert Research
Institute, University of Nevada System.
Koetsier, P., G. W. Minshall, and C. T. Robinson. 1996. Benthos and macroinvertebrate drift in six streams
differing in alkalinity. Hydrobiologia 317:41-49.
Koning, C. W. (ed.). 1999. Riparian Assessment and Prescription Procedures. Province of British Columbia,
Ministry of Forests and Ministry of Environment, Lands and Parks. Watershed Restoration Technical
Circular No. 6.
LaPerriere, J. D., E. E. Van Nieuwenhuyse, and P. R. Anderson. 1989. Benthic algal biomass and
productivity in high subarctic streams, Alaska. Hydrobiologia 172:63-75.
Le Cren, E. D. 1969. Estimates of fish populations and production in small streams of England. Pages
269-280 in T. G. Northcote (ed.). Symposium on Salmon and Trout in Streams. H. R. MacMillan
Lectures in Fisheries, University of British Columbia, Vancouver, BC.
Lee, J. 0. and A. E. Hershey. 2000. Effect of aquatic bryophytes and long-term fertilization on arctic
stream insects. Journal of the North American Benthological Society 19:697-708.
Lorenz, A. W., and C. K. Feld. 2013. Upstream river morphology and riparian land use overrule local
restoration effects on ecological status assessment. Hydrobiologia 704:489-501.
Recommended Determination
C-53
December 2022
-------
Appendix C
Technical Evaluation of Potential
Compensatory Mitigation Measures
McFadden, J. T., and E. L. Cooper. 1962. An ecological comparison of six populations of brown trout
[Salmo trutta). Limnology and Oceanography 10:88-95.
Mclntyre, J. K, D. H. Baldwin, D. A. Beauchamp, and N. L. Scholz. 2012. Low-level copper exposures
increase visibility and vulnerability of juvenile coho salmon to cutthroat trout predators. Ecological
Applications 22:1460-1471.
Meyer, J. L., D. L. Strayer, J. B. Wallace, S. L. Eggert, G. S. Helfman, and N. E. Leonard. 2007. The
contribution of headwater streams to biodiversity in river networks. Journal of the American Water
Resources Association 43:86-103.
Mortensen, E. 1977. Fish production in small Danish streams. Folia Limnologica Scandinavica 17:21-26.
Muhar, S., G. Unfer, S. Schmutz, M. Jungwirth, G. Egger, and K. Angermann. 2004. Assessing river
restoration programmes: habitat conditions, fish fauna and vegetation as indicators for the
possibilities and constraints of river restoration. Pages 300-305 in Proceedings of 5th International
Symposium on Ecohydraulics. Aquatic Habitats: analysis and restoration.
MWLAP (Ministry of Water, Land and Air Protection). 2002. Ecological Restoration Guidelines for British
Columbia. Biodiversity Branch of Ministry of Water, Land and Air Protection. Available:
https://www.env.gov.bc.ca/fia/documents/restorationguidelines.pdf. Accessed: January 21, 2022.
Pieters, R., S. Harris, L. C. Thompson, L. Vidmanic, M. Roushorne, G. Lawrence, J. G. Stockner, H. Andrusak,
K. I.Ashley, B. Lindsay, K. Hall, and D. Lombard. Restoration of Kokanee Salmon in the Arrow Lakes
Reservoir, British Columbia: Preliminary Results of a Fertilization Experiment. Pages 177-196 in J.
Stockner (ed.), Nutrients in Salmonid Ecosystems: Sustaining Production and Biodiversity. Symposium
34. Bethesda, MD: American Fisheries Society.
Quamme, D. L. and P. A. Slaney. 2003. The relationship between nutrient concentration and stream
insect abundance. Pages 163-175 in J. Stockner (ed.), Nutrients in Salmonid Ecosystems: Sustaining
Production and Biodiversity. Symposium 34. Bethesda, MD: American Fisheries Society.
Quinn, T. P. and A. H. Dittman. 1992. Fishes. Pages 145-211 in F. Papi (ed.). Animal Homing London:
Chapman & Hall.
Railsback, S. F., M. Gard, B. C. Harvey, J. L. White, and J. K. Zimmerman. 2013. Contrast of degraded and
restored stream habitat using an individual-based salmon model. North American Journal of
Fisheries Management 33:384-399.
Richardson, J. S., R. J. Naiman, F. J. Swanson, and D. E. Hibbs. 2005. Riparian communities associated with
Pacific Northwest headwater streams: assemblages, processes, and uniqueness. Journal of the
American Water Resources Association 41:935-947.
Recommended Determination
C-54
December 2022
-------
Appendix C
Technical Evaluation of Potential
Compensatory Mitigation Measures
Roni, P., G. Pess, T. Beechie, and S. Morley. 2010. Estimating changes in coho salmon and steelhead
abundance from watershed restoration: how much restoration is needed to measurably increase
smolt production? North American Journal of Fisheries Management 30:1469-1484.
Ryder, R. A., and S. R. Kerr. 1989. Environmental priorities: placing habitat in hierarchic perspective.
Canadian Special Publication of Fisheries and Aquatic Sciences.
Schemel, L. E., T. R. Sommer, A. B. Miiller-Solger, and W. C. Harrell. 2004. Hydrologic variability, water
chemistry, and phytoplankton biomass in a large floodplain of the Sacramento River, CA, USA.
Hydrobiologia 513:129-139.
Schindler, D. E., P. R. Leavitt, C. S. Brock, S. P. Johnson, and P. D. Quay. 2005. Marine-derived nutrients,
commercial fisheries, and production of salmon and lake algae in Alaska. Ecology 86:3225-3231.
Scoppettone, G. G. and R. E. Bailey. 1983. Restoration of a reproductive population of Lahontan cutthroat
trout (Salmo clarki henshawi) to the Truckee River/Pyramid Lake System. Reno: Nevada: U. S. Fish
and Wildlife Service, Great Basin Complex.
Shaftel, R. S., R. S. King, and J. A. Back. 2011a. Alder cover drives nitrogen availability in Kenai lowland
headwater streams, Alaska. Biogeochemistry 107:135-148.
Shaftel, R., R. King, and J. Back. 2011b. Breakdown rates, nutrient concentrations, and macroinvertebrate
colonization of bluejoint grass litter in headwater streams of the Kenai Peninsula, Alaska. Journal of
the North American Benthological Society 30:386-398.
Sharma, R., and R. Hilborn. 2001. Empirical relationships between watershed characteristics and coho
salmon (Oncorhynchus kisutch) smolt abundance in 14 western Washington streams. Canadian
Journal of Fisheries and Aquatic Sciences 58:1453-1463.
Slaney, P. A., C. J. Perrin, and B. R. Ward. 1986. Nutrient concentration as a limitation to steelhead smolt
production in the Keogh River. Proceedings of the Annual Conference of the Western Association of
Fish and Wildlife Agencies 66:146-155.
Sloat, M. R., G. H. Reeves, and K. R. Christiansen. 2017. Stream network geomorphology mediates
predicted vulnerability of anadromous fish habitat to hydrologic change in southeast Alaska. Global
Change Biology 23:604-620.
Sterling, M.S., and K.L. Ashley. 2003. Evaluations of slow-release fertilizer for rehabilitating oligotrophic
streams. Pages 237-243 in J. Stockner (ed.), Nutrients in Salmonid Ecosystems: Sustaining Production
and Biodiversity. Symposium 34. Bethesda, MD: American Fisheries Society.
Stockner, J. G., and E. A. Macisaac. 1996. British Columbia Lake enrichment programme: two decades of
habitat enhancement for sockeye salmon. Regulated Rivers: Research and Management 12:547-561.
Recommended Determination
C-55
December 2022
-------
Appendix C
Technical Evaluation of Potential
Compensatory Mitigation Measures
Stockner, J. G., and K. L. Ashley. 2003. Salmon nutrients: closing the circle. Pages 3-15 in J. Stockner (ed.),
Nutrients in Salmonid Ecosystems: Sustaining Production and Biodiversity. Symposium 34. Bethesda,
MD: American Fisheries Society.
Sundermann, A., S. Stoll, and P. Haase. 2011. River restoration success depends on the species pool of the
immediate surroundings. Ecological Applications 21:1962-1971.
Tank, J. L., E. J. Rosi-Marshall, N. A. Griffiths, S. A. Entrekin, and M. L. Stephen. 2010. A review of
allochthonous organic matter dynamics and metabolism in streams. Journal of the North American
Benthological Society 29:118-146.
U.S. Bureau of Reclamation. 2007. Yakima River Basin water storage feasibility study - Planning report
and Environmental Impact Statement. USBR Yakima Office.
Vannote, R. L., G. W. Minshall, K. W. Cummins, J. R. Sedell, and C. E. Cushing. 1980. The river continuum
concept. Canadian Journal of Fisheries and Aquatic Sciences 37:130-137.
Walker, C. M., R. S. King, D. F. Whigham, and S. J. Baird. 2012. Landscape and wetland influences on
headwater stream chemistry in the Kenai Lowlands, Alaska. Wetlands 32:301-310.
Ward, B. R., D. J. F. McCubbing, and P. A. Slaney. 2003. Evaluation of the addition of inorganic nutrients
and stream habitat structures in the Keogh River Watershed. Pages 127-148 in American Fisheries
Symposium 2003.
Ward, B. R., and P. A. Slaney. Egg-to-smolt survival and fry-to-smolt density dependence of Keough River
steelhead trout. Canadian Special Publication of Fisheries and Aquatic Sciences (1993):209-217.
Wilson, G. A., K. I. Ashley, R. W. Land, and P. A. Slaney. 2003. Experimental Enrichment of Two
Oligotrophic Rivers in South Coastal British Columbia. American Fisheries Society Symposium
31:149-162.
Wipfli, M. S. and D. P. Gregovich. 2002. Export of invertebrates and detritus from fishless headwater
streams in southeastern Alaska: Implications for downstream salmonid production. Freshwater
Biology 47:957-969.
Wipfli, M. S., J. S. Richardson, and R. J. Naiman. 2007. Ecological linkages between headwaters and
downstream ecosystems: Transport of organic matter, invertebrates, and wood down headwater
channels. Journal of the American Water Resources Association 43:72-85.
Wisby, W. J. and A. D. Hasler. 1954. Effect of occlusion on migrating silver salmon (Oncorhynchus
kisutch). Journal of the Fisheries Research Board of Canada 11:472-478.
Wurts, W. A. 2002. Alkalinity and hardness in production ponds. World Aquaculture 33:16-17.
Yoshikawa, K., L. D. Hinzman, and D. L. Kane. 2007. Spring and aufeis (icing) hydrology in Brooks Range,
Alaska. Journal of Geophysical Research 112:G4.
Recommended Determination
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December 2022
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