External Review Draft j EPA910-R-12-004d | May 2012
EPA
United States
Environmental Protection
Agency
An Assessment of Potential Mining Impacts
on Salmon Ecosystems of Bristol Bay, Alaska
Executive Summary
U.S. Environmental Protection Agency, Seattle, WA
www.epa.gov/bristolbay
External Review Draft - Do Not Cite or Quote
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DISCLAIMER ___
This document is distributed solely for the purpose of pre-dissemination peer review under applica
guidelines. It has not been formally disseminated by the U.S. Environmental Protection Agency (US
and should not be construed to represent any Agency determination or policy. Mention of trade names or commercial products
Joes not constitute endorsement or recommendation for use.
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Tributary ofNapotoii Creek, near the Humble claim Photo: Michael Wiedmer
Executive Summary
The Bristol Bay watershed in southwestern Alaska supports the largest sockeye
salmon fishery in the world, is home to 25 Federally Recognized Tribal
Governments, and contains large mineral resources. The potential for large-scale
mining activities in the watershed has raised concerns about the impact of mining
on the sustainability of Bristol Bay's world-class fisheries, and the future of Alaska
Native tribes in the watershed who have maintained a salmon-based culture
and subsistence-based lifestyle for at least 4,000 years. The U.S. Environmental
Protection Agency (USEPA) launched this assessment to determine the significance
of Bristol Bay's ecological resources and evaluate the potential impacts of large-
scale mining on these resources. The USEPA will use the results of this assessment to
inform the consideration of options consistent with its role under the Clean Water
Act. The assessment is intended to provide a scientific and technical foundation for
future decision making; the USEPA will not address use of its regulatory authority
until the assessment becomes final and has made no judgment about whether to
use that authority at this time.
In addition to informing future USEPA actions, this report is of potential use to
other federal and state government entities with an interest in mining in the Bristol
Bay region. It is also of interest to both proponents and opponents of mining. By
providing an unbiased assessment of potential risks, this assessment informs an
active debate concerning the risks of mining development to the sustainability of
the Bristol Bay salmon fishery.
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The Lower Nushagak River between Portage Creek and Ekwok Photo: Michael Wiedmer (ADFG)
Scope of the Assessment
This assessment reviews, analyzes, and
synthesizes available information on the
potential impacts of large-scale mining
development on Bristol Bay fisheries and
subsequent effects on the wildlife and
Alaska Native cultures of the region. The
primary focus of the assessment is the
quality, quantity, and genetic diversity
of salmonid fish. Because wildlife and
Alaska Native cultures in Bristol Bay are
intimately connected and dependent
upon fish, the quantity and diversity
of wildlife and the culture and human
welfare of indigenous peoples, as
affected by changes in the fisheries are
additional endpoints of the assessment.
The geographic scope of the assessment
is the Nushagak River and Kvichak River
watersheds. These are the largest of
the Bristol Bay watershed's six major
river basins and compose about 50%
of the total watershed area. These
two watersheds are also identified
as mineral development areas by the
State of Alaska. The Pebble deposit,
the most likely site for near-term large-
scale mining development in the
region, is located at the intersection of
the Nushagak River and Kvichak River
Watershed Boundary
| Approximate Pebble Deposit Location
The Nushagak River and Kvichak River Watersheds of Bristol Bay
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NORTH FORK k
Mine Pit"
SOUTH FORK KOKTULI
UPPER TALARIK
l\
A
0 2.5 5
2.5 5
] Miles
Note. Sampling intensity is greatly reduced away from the Pebble deposit area
Streams without data may hot have been surveyed; thus, it is unknown
whether or not they provide suitable habitat for these species.
Spawning
Rearing
Present (Life Stage Unknown)
Minimum Mine Size
Site Watershed
Watershed Boundary
Reported Salmon (Sockeye, Chinook, Coho, Pink, and Chum Combined) Distribution in the North and South Fork Koktuli River and Upper Talarik
Creek. Designation of species spawning, rearing, and presence is based on ADFG Draft 2012 Anadromous Waters Catalog (Johnson and Blanche pers. comm.). Spawning
= spawning adults observed, rearing = juveniles observed, present = present, but life stage use not determined. Life stage-specific reach designations are likely
underestimates, given the logistical constraints on the ability to accurately capture all streams that may support life stage use at various times of the year.
watersheds. The headwaters of three
biologically productive tributaries
originate in this region: the North Fork
Koktuli River, located to the northwest of
the Pebble deposit, which flows into the
Nushagak River via the Mulchatna River;
the South Fork Koktuli River, which drains
the Pebble deposit area and converges
with the North Fork west of the Pebble
deposit; and Upper Talarik Creek, which
drains the eastern portion of the Pebble
deposit and flows into the Kvichak River
via Iliamna Lake, the largest undeveloped
lake in the United States.
The assessment addresses two general
time periods for mine activities. The
first is the development and operation
phase, during which mine infrastructure
is built and the mine is operated. This
phase may last from 25 to 100 years or
more. The second is the post-mining,
or post-closure, phase, during which
the site would be monitored and, as
necessary, water treatment and other
waste management activities continued
and failures remediated. Because mining
wastes would be altered by geologic
processes but would not degrade, this
period would continue for centuries and
potentially "in perpetuity."
The assessment was conducted as an
ecological risk assessment. We started
with a thorough review of what is known
about the Bristol Bay watershed fishery
and wildlife and the Alaska Native
cultures. We also reviewed information
about copper mining and available
information outlining proposed mining
operations for the Pebble deposit that
has been the focus of much exploratory
study and has received much attention
from various groups in and outside
of Alaska. Using that information, we
developed a set of conceptual models
to show potential associations between
the endpoints of interest—the salmon
fishery and salmon populations—and
the various types of environmental
stressors that might reasonably be
expected as a result of large-scale
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mining. Those conceptual models
were refined through interactions with
regional stakeholders. The assessment
was then developed based upon the
background characterization studies and
the conceptual models.
This is not an in-depth assessment of a
specific mine, but rather an examination
of the impacts of mining activities at
the scale and with the characteristics
realistically foreseeable in the Bristol
Bay region, given the nature of mineral
deposits in the watershed and the
requirements for successful mining
development. Known information about
the Pebble deposit is very relevant,
because it is likely representative of any
potential near-future mine development
in the area. Thus, the assessment largely
analyzes a mine scenario that reflects
the expected characteristics of mining
operations at the Pebble deposit.
However, the analysis is intended to
provide a baseline for understanding
the potential impacts of mining
development throughout the Nushagak
River and Kvichak River watersheds.
The potential mining of other existing
copper deposits in the region would
likely reflect the same type of mining
activities and facilities analyzed for
50
] Kilometers
50
] Miles
| Approximate Pebble Deposit Location
Watershed Boundary
Confirmed (66%)
Mapped, no field evidence, but use likely (4%)
Potential/probable, but undocumented (7%)
Mapped, no field evidence, but use unlikely or limited (1%)
No evidence (22%)
Salmon-Producing Subwatersheds in the Nushagak River and Kvichak River
Watersheds. A total of 568 subwatersheds (total area of 61,317 km2) were assessed in the
Nushagak River and Kvichak River watersheds. The percentage of this area in each category is
shown in parentheses in the legend. Note that the southwestern portion of the Nushagak River
watershed (i.e., the Nushagak Bay watershed) was not included in this analysis. Data from
Demory et al. (1964), Nelson (1967), Salomone et al. (2009), Johnson and Blanche (2011), and
ADFG (2012).
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Bristol Bay
Russia Mainland & Islands
West Kamchatka
East Kamchatka
Western Alaska (excluding Bristol Bay)
South Alaska Peninsula
Kodiak
Cook Inlet
Prince William Sound
Southeast Alaska
North British Columbia
South British Columbia, Washington & Oregon
Nushagak & Naknek-Kvichak
Egegik
Ugashik
Togiak
Average Annual Relative Abundance and Commercial Harvest of Wild Sockeye Salmon. Average annual relative abundance of wild sockeye salmon stocks in
the North Pacific, 1956 to 2005; with the exception of Bristol Bay, stocks are ordered from west to east across the North Pacific, from Russia (Russia Mainland and Islands,
West Kamchatka, East Kamchatka) to western North America (all other sites). Average annual relative commercial sockeye harvest in Bristol Bay watersheds, 1990 to
2009. Data from Ruggerone et al. (2010) and Salomone (pers. comm.).
the Pebble deposit scenario (open pit
mining, waste rock piles, tailing storage
facilities) and, therefore, would present
potential risks similar to those outlined in
this assessment.
Ecological Resources
The Bristol Bay watershed provides
habitat for numerous animal species,
including 35 fishes, more than 190 birds,
and more than 40 terrestrial mammals.
Many of these species are essential
to the structure and function of the
region's ecosystems and economies.
Chief among these resources is a world-
class commercial and sport fishery for
Pacific salmon and other important
resident fishes. The watershed supports
production of all five species of Pacific
salmon found in North America: sockeye
(Oncorhynchus nerkd), coho (O. kisutch],
Chinook or king (O. tshawytscha), chum
(O. ketd), and pink (O. gorbuschd). Because
no hatchery fish are raised or released
in the watershed, Bristol Bay's salmon
populations are entirely wild. These fish
are anadromous—hatching and rearing
in freshwater systems, migrating to the
sea to grow to adult size, and returning to
freshwater systems to spawn and die.
The most abundant salmon species in the
watershed is sockeye salmon. The Bristol
Bay watershed supports the largest
sockeye salmon fishery in the world, with
approximately 46% of the average global
abundance of wild sockeye salmon.
Between 1990 and 2010, the annual
average inshore run of sockeye salmon in
Bristol Bay was approximately 37.5 million
fish. Annual commercial harvest of
sockeye over this same period averaged
27.5 million. Approximately half of the
Bristol Bay sockeye salmon production
is from the Nushagak River and Kvichak
River watersheds—the area of focus for
this assessment.
In addition to sockeye salmon, Chinook
salmon are also abundant. For example,
Chinook returns to the Nushagak River
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are consistently greater than 100,000
fish per year and have exceeded 200,000
fish in 11 years between 1966 and 2010,
frequently placing Nushagak River
Chinook runs at or near the world's
largest. This is noteworthy given the
Nushagak River's small watershed area
compared to other Chinook-producing
rivers such as the Yukon River, which
spans Alaska, and the Kuskokwim River in
southwest Alaska, just north of Bristol Bay.
The Bristol Bay watershed also supports
populations of resident fishes that
typically remain within the watershed's
freshwater habitats throughout their
life cycles. The region contains highly
productive waters for such sport and
subsistence fish species as rainbow trout
(Oncorhynchusmykiss), Dolly Varden
(Salvelinus malma), Arctic char (Salvelinus
alpinus), Arctic grayling (Thymallus
arcticus), and lake trout (Salvelinus
namaycush). These fish species occupy a
variety of habitats within the watershed,
from headwater streams to wetlands
to large rivers and lakes. The Bristol Bay
region is especially renowned for the
abundance and size of its rainbow trout:
between 2003 and 2007 an estimated
196,825 rainbow trout were caught in the
Bristol Bay Sport Fish Management Area.
The exceptional quality of the Bristol
Bay watershed's fish populations can
be attributed to several factors, the
most important of which is perhaps
the watershed's high-quality, diverse
aquatic habitats, which are untouched
by human-engineered structures and
flow management controls. Surface and
subsurface waters are highly connected,
enabling hydrologicand biochemical
connectivity between wetlands, ponds,
streams, and rivers, thus increasing the
diversity and stability of habitats able
to support fish. The high diversity of
habitats, high quality of surface and
subsurface waters, and relatively low
development pressures all contribute to
making Bristol Bay a highly productive
system. This high diversity of habitats
also has enabled the development of
high genetic diversity offish populations.
This genetic diversity acts to reduce year-
to-year variability in total production and
increases the stability of the fishery.
The return of salmon from the Pacific
Ocean brings nutrients into the
watershed and fuels terrestrial and
aquatic food webs. The condition of
terrestrial ecosystems in Bristol Bay,
therefore, is intimately linked to the
condition of salmon populations. Unlike
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•* - \
most terrestrial ecosystems, the Bristol
Bay watershed has undergone little
development and remains largely intact.
Consequently, the watershed continues
to support its historic complement of
species, including large carnivores such
as brown bears (Ursus arctos), bald eagles
(Haliaeetus leucocephalus), and gray
wolves (Canis lupus); ungulates such as
moose (Alces alces gigas) and caribou
(Rangifer tamndus grant/); and numerous
waterfowl species.
Wildlife populations tend to be relatively
large in the region, due to the increased
biological productivity associated
with Pacific salmon runs. Brown bears
are abundant in the Nushagak River
and Kvichak River watersheds. Moose
and caribou also are abundant, with
populations especially high in the
Nushagak River watershed where felt-
leaf willow, a preferred plant species,
is abundant. The Nushagak River and
Kvichak River watersheds are used by
caribou, primarily the Mulchatna caribou
herd. This herd ranges widely through
these watersheds, but also spends
considerable time in other watersheds.
Indigenous Cultures
The Alaska Native cultures present in
the Nushagak River and Kvichak River
watersheds—the Yup'ik and Dena'ina—
are two of the last intact, sustainable
salmon-based cultures in the world. In
contrast, other Pacific Northwest salmon-
based cultures are severely threatened
due to development, degraded natural
resources, and declining salmon
resources. Pacific salmon are no longer
found in 40% of their historical breeding
ranges in the western United States, and
where populations remain, they tend to
be significantly reduced or dominated
by hatchery fish. Salmon are integral to
the entire way of life in these cultures as
subsistence food and as the foundation
for their language, spirituality, and social
structure. The cultures have a strong
connection to the landscape and its
resources. In the Bristol Bay watershed,
this connection has been maintained
for at least the past 4,000 years and
is in part due to and responsible for
the continued pristine condition of
the region's landscape and biological
resources. The respect and importance
given salmon and other wildlife, along
with the traditional knowledge of
the environment, have produced a
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sustainable subsistence-based economy.
This subsistence-based way of life is a
key element of indigenous identity and it
serves a wide range of economic, social,
and cultural functions in Yup'ik and
Dena'ina societies.
Fourteen of Bristol Bay's 25 Alaska Native
villages and communities are within
the Nushagak River and Kvichak River
watersheds, with a total population
of 4,337 in 2010. Thirteen of the 14
communities are Federally Recognized
Tribal Governments. In the Bristol Bay
region, salmon constitute approximately
52% of the subsistence harvest.
Subsistence from all sources (fish, moose,
and other wildlife) accounts for an
average of 80% of protein consumed
by area residents. The subsistence way
of life in many Alaska Native villages is
augmented with activities supporting
cash economy transactions. Alaska
Native villages, in partnership with Alaska
Native corporations and other business
interests, are considering a variety of
economic development opportunities—
mining included. Some Alaska Native
villages have decided for themselves
that large-scale hard rock mining is not
the direction they would like to go, while
a few others are seriously considering
this opportunity. All are concerned with
the long-term sustainability of their
communities.
Economics Of Ecological
Resources
The Bristol Bay watershed supports
several economic sectors that are
wilderness-compatible and sustainable:
commercial, sport and subsistence
fishing, sport and subsistence hunting,
and non-consumptive recreation.
Considering all these sectors, the
ecological resources of the Bristol Bay
watershed generated nearly $480 million
(M) in direct economic expenditures and
sales, in 2009, and provided employment
for over 14,000 full- and part-time workers.
The Bristol Bay commercial salmon
fishery generates the largest component
of economic activity and was valued
at approximately $300 M in 2009
(first wholesale value) and provided
employment for over 11,500 full- and
part-time workers at the peak of the
season. These estimates do not include
retail expenditures from national and
international sales.
Based on 2009 data, the Bristol Bay sport-
fishing industry supports approximately
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Uiamna Lake
Cook Inle
it
A
29,000 sport-fishing trips, generates
approximately $60 M per year, and
directly employs over 850 full- and part-
time workers. The vast majority of this
revenue is spent in the Bristol Bay region.
Sport hunting—mostly of caribou,
moose, and brown bear—generates
more than $8 M per year and employs
over 130 full- and part-time workers.
The scenic value of the watershed,
measured in terms of wildlife viewing
and tourism, is estimated to generate an
additional $100 M per year and supports
nearly 1,700 full- and part-time workers.
The subsistence harvest offish also
contributes to the region's economy
when Alaskan households spend money
on subsistence-related supplies. These
contributions are estimated to be slightly
over $6M per year.
Geological Resources
In addition to significant and valuable
ecological resources, the Nushagak
River and Kvichak River watersheds
contain considerable mineral resources.
The potential for large-scale mining
development within the region is
greatest for copper deposits and, to a
lesser extent, for intrusion-related gold
deposits. Because these deposits are
Potential 139-kilometer (86-mile) Transportation Corridor Connecting the
Pebble Deposit Area to Cook Inlet
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low-grade—meaning that they contain
relatively small amounts of metals
relative to the amount of ore—mining
will be economic only if conducted over
a large area, and a large amount of waste
material will be produced as a result of
mining and processing.
The largest known deposit and the
deposit most explored to assess future
mining potential is the Pebble deposit.
If fully mined, the Pebble deposit could
produce more than 11 billion metric tons
(1 metric ton = 1,000 kg, approximately
2,200 pounds) of ore, which would make
it the largest mine of its type in North
America. In comparison, the largest
existing copper mine in the United
States is the Safford Mine in Arizona with
7.3 billion metric tons of ore. Although
the Pebble deposit represents the
most imminent and likely site of mine
development, other mineral deposits
with potentially significant resources
exist within the Nushagak River and
Kvichak River watersheds. Several
specific claims have been filed, many
near the Pebble deposit. Findings of this
assessment concerning the potential
impacts of large-scale mining are
generally applicable to these other sites.
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Mine Scenario
A detailed and final mine plan has not
been made available for any of the copper
deposits identified in the Bristol Bay
watershed, nor is one strictly needed to
conduct this assessment. To examine the
mining-related stressors that could affect
ecological resources in the watershed, we
developed a hypothetical mine scenario,
designed to be as realistic as possible.
The mine scenario is based on mining
of the Pebble deposit, because it is the
best-characterized mineral resource
and the most likely to be developed in
the near term. Thus, the mine scenario
draws on plans published by the Pebble
Limited Partnership (PLP) and baseline
data developed by PLP to characterize
the likely mine site and surrounding
environment. Details of a mining plan for
the Pebble deposit or for other deposits
in the watershed may differ from our
mine scenario; however, our scenario
reflects the general characteristics of
mineral deposits in the watershed,
contemporary mining technologies and
best practices, the scale of mining activity
required for economic development of
the resource, and necessary development
of infrastructure to support large-scale
mining. Therefore, the USEPA concludes
that the mine scenario represents the
sort of development plan that can be
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,.:.
_
Minimum and Maximum Mine Footprints in the Assessment Scenario.
Individual mine components are the mine pit, waste rock piles, and one or more tailings
storage facilities (TSFs). The dark bar at the north end of TSF1 indicates the dam for
which tailings dam failure is modeled.
anticipated for a copper deposit in the
Bristol Bay watershed. Uncertainties
associated with the mine scenario are
discussed later in this executive summary.
The mine scenario includes minimum
and maximum mine sizes, based on
the amount of ore processed (2 billion
metric tons vs. 6.5 billion metric tons),
and approximate corresponding mine
life spans of 25 to 78 years, respectively.
Components of the minimum mine
would include a 5.5 km2 (1,358 acre)
mine pit, a 14.9-km2 (3,686-acre) tailings
impoundment behind a 208 m-high
(685-foot-high) earthen dam; a 13.3-
km2 (3,286-acre) waste rock pile; a 139-
km (86-mile) road with four pipelines
for product concentrate, return water,
diesel, and natural gas; and facilities for
ore processing and support services.
The maximum size mine would include
a much larger pit and waste rock pile,
with a combined area of 38.4 km2 (9,486
acres), potentially an underground mine,
and three tailings impoundments, with a
combined area of 43.7 km2 (10,807 acres).
The first part of the assessment considers
routine operation, which assumes that the
mine would be designed using practices
to minimize environmental impacts and
that no significant human or engineering
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Sockeye salmon near Pedro Bay, Iliamna Lake Photo: Thomas Quinn (University of Washington)
failures occur during or for centuries
after operation. The second part of the
assessment considers various failures
that have occurred during the operation
of other mines and have the potential to
occur here.
The assessment does not consider all
mining-related development. Although
the mine scenario assumes development
of a deep-water port on Cook Inlet to
ship concentrated product elsewhere
for smelting and refining, impacts of the
development and operation of a deep-
water port are not assessed. Additionally,
the assessment does not evaluate the
potential environmental impacts of one
or more electricity-generating power
plants that would need to be constructed
to provide power at the mine site and the
deep-water port facility. This assessment
also does not consider potential impacts
resulting from secondary development
that is likely to accompany a large-
scale mine development. Secondary
development includes, but is not limited
to, additional support services for mine
employees and their families, increased
recreational development due to increased
access, development of vacation homes,
and increased transportation infrastructure
(i.e., airports, docks, and roads).
Overall Risks to Salmon and
Other Fish
Based on the mine scenario, the
assessment defines potential mining-
related stressors that could affect the
Bristol Bay watershed's fish and would
consequently have impacts on wildlife
and human welfare.
No Failure
No failure, or routine operation, is a
mode of operation defined as using
the highest design standards and day-
to-day practices, with all equipment
and management systems operated in
accordance with applicable specifications
and requirements. In the no failure
mode of operation, we assume that best
practical engineering and mitigation
practices are in place and in optimal
operating condition. We do not specify
all of those mitigation practices, but
rather, we assume that they would
be in place and properly functioning.
Analyzing routine operations is not
meant to imply that a failure-free mining
operation is likely; rather, it is meant to
isolate the inevitable and foreseeable
effects of mining from those that are
unintended and thus more difficult to
12
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c£*->v4 ; j ) .N
^V' - 7 j » K i *
;% .V,'.1, > -.'
/
Stream Eliminated
Stream Blocked
Wetland Eliminated
Wetland Blocked
Freshwater Habitat
predict. With no failures, adverse effects
outside the mine footprint are minimized
by complete containment of waste rock
and mine tailings, reliable collection
of all water from the site, and effective
treatment of effluents. Nonetheless,
impacts on fish resulting from habitat
loss and modification within and beyond
the area of mining activity would
result from six key direct and indirect
mechanisms.
(1) Eliminated or blocked streams
under the minimum and maximum
mine footprints (i.e., the mine
pit, waste rock piles, and tailings
storage facilities) would result in
the loss of 87.5 to 141.4 km (55 to
87 miles), respectively, of possible
spawning or rearing habitats for
coho salmon, Chinook salmon,
sockeye salmon, rainbow trout, and
Dolly Varden.
(2) Reduced flow resulting from
water retention for use in mine
operations, ore processing,
transport, and other processes
would reduce the amount and
quality offish habitat. Reductions
in streamflow exceeding 20%
would adversely affect habitat in
13
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an additional 2 to 10 km (1.2 to
6.2 miles) of streams, reducing
production of coho salmon,
sockeye salmon, Chinook salmon,
rainbow trout, and Dolly Varden.
An unquantifiable area of riparian
floodplain wetland habitat would
either be lost or suffer substantial
changes in hydrologic connectivity
with streams due to reduced flow
from the mine footprint.
(3) Removal of 10.2 to 17.3 km2
(2,512 to 4,286 acres) of wetlands
in the footprint of the mine would
eliminate off-channel habitat for
salmon and other fishes. Wetland
loss would reduce availability
and access to hydraulically and
thermally diverse habitats that
can provide enhanced foraging
opportunities and important
rearing habitats for juvenile salmon
(4) Indirect effects of stream and
wetland removal would include
reductions in the quality of
downstream habitat for the same
species listed above in the three
headwater streams draining the
mine site. Sources of these indirect
effects would include the following:
• Reduced food resources
would result from the loss of
organic material and drifting
invertebrates from the 87.5
to 141.4 km (55 to 87 miles)
of streams and streamside
wetlands lost to the mine
footprint.
• The balance of surface water
and groundwater inputs to
downstream reaches would
shift, potentially reducing
winter fish habitat and making
the streams less suitable for
spawning and rearing.
• Water treatment and reduced
passage through groundwater
flowpaths could increase
summer water temperatures
and decrease winter water
temperatures, making streams
less suitable for salmon, trout,
and char.
These indirect effects cannot be
quantified but likely would diminish fish
production downstream of the mine site.
(5) Diminished habitat quality in
streams below road crossings
would result primarily from altered
flow, runoff of road salts, and
14
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Groundwater upwelling near Kaskanak Creek in the Lower Talarik Basin Photo: Joe Ebersole (USEPA)
siltation of spawning habitat and
reduced invertebrate prey. The
road is adjacent to Iliamna Lake and
crosses multiple tributary streams.
These habitats are important
spawning areas for sockeye salmon,
putting sockeye particularly at risk
to impacts from the road.
(6) Inhibition of salmonid
movement at road crossings
could result from culverts that may,
over time, block or diminish use of
the full stream length.
Failure
The assessment evaluates four failures
that have occurred at other large-scale
mining and related infrastructure
projects and that could occur during
mine operations or after mine closure:
tailings dam failure, product concentrate
or return water pipeline failure, water
collection and treatment failures, and
failures of roads and culverts. Risks
associated with each of these failures are
summarized in the following table.
Tailings Dam Failure
Tailings are the waste materials produced
during ore processing, which in our
scenario would be stored in tailings
storage facilities (TSFs) consisting of
tailings dams and impoundments. The
annual probability of failure for each
tailings dam would be in the range
of one-in-ten-thousand to one-in-a-
million.The probability of one of several
tailings dams failing increases with the
number of dams. The minimum mine size
outlined in the mine scenario includes
one TSF with three dams; the maximum
mine size includes three TSFs, with a
total of eight dams. The TSFs and their
component dams are likely to be in place
for hundreds to thousands of years, long
beyond the life of the mine. Although
details for the actual design of mining
operations at the Pebble deposit are
unknown, available reports from the
PLP suggest tailings dams as high as 208
m (685 feet) at TSF 1. At this height, the
tailings dam would be higher than the St.
Louis Gateway Arch and the Washington
Monument. We evaluated two dam
failures in this assessment: one when
the TSF was partially full (partial-volume
failure) and one when it was completely
full (full-volume failure). In both cases we
assumed a release of 20% of the tailings,
a conservative estimate that is well
within the range of historical tailings dam
failures.
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Summary of Probability and Consequences of Potential Failures under the Mine Scenario
= recurrenc
Product concentrate pipeline
Concentrate spill into a stream
Concentrate spill into a wetland
10,000 to 1 million years"
10-3perkm-year = 98%
chance per pipeline in 25
years
2x10~2 per year = 1.5 stream-
contaminating spills in 78
years
3 x10~2 per year = 2
wetland-contaminating
spills in 78 years
would be destroyed and mok ^
and rivers would have greatly degraded
habitat for decades.
Most failures would occur between stream
or wetland crossings and might have little
effect on fish.
Fish and invertebrates would experience
acute exposure to toxic water and chronic
exposure to toxic sediment in a stream and
potentially extending to Iliamna Lake.
Invertebrates and potentially fish would
experience acute exposure to toxic water
and chronic exposure to toxic sediment in
a pond or other wetland.
Return water pipeline
Same as product concentrate
pipeline
Fish and invertebrates would experience
acute exposure to toxic water.
Culvert, operation
Frequent inspections and regular
maintenance would result in few
impassable culverts.
Culvert, post-operation
culvert-instantaneous = 4 to
10 culverts
In surveys of road culverts, roughly one
third to two-thirds are impassable to fish
at any one time. This would result in 4 to
10salmonid streams blocked.
Water collection and treatment,
operation
Collection and treatment failures are
highly likely to result in release of
untreated leachates for hours to months.
Water collection and treatment,
planned post-closure
Water collection and treatment,
premature post-closure or perpetuity
Collection and treatment failures are
highly likely to result in release of
untreated leachates for days to months.
When water is no longer managed,
untreated leachates would flow to the
streams.
'nces in derivation, the probabilities are not directly comparable.
d state safety requirements. Observed failure rates for earthen dams are higher (about 5 x 104 peryear or a recurrence frequency of 2,000 years).
-------
Full Volume
Transamerica Building- 260 Meters
Tailings Dam TSF1-208 Meters
Gateway Arch -192 Meters
Washington Monument -169 Meters
Tailings Reservoir
Partial Volume
Height of the Partial-Volume and Full-Volume Dam at TSF 1, Relative to Common Landmarks
The range of estimated probabilities
of dam failure is wide, reflecting the
great uncertainty concerning such
failures. The most straightforward
method of estimating the annual
probability of failure of a tailings dam
is to use the historical failure rate of
similar dams. Three reviews of tailings
dam failures produced an average
rate of approximately 1 failure per
2,000 dam years, or 5 x 10~4 failures
per dam year. The argument against
this approach is that it does not fully
reflect current engineering practice.
Some studies suggest that improved
design, construction, and monitoring
practices can reduce the failure rate by
an order of magnitude or more, resulting
in an estimated failure probability
within our assumed range. The State
of Alaska's guidelines suggest that an
applicant follow accepted industry
design practices such as those provided
by the U.S. Army Corps of Engineers
(USAGE), Federal Energy Regulatory
Commission (FERC), and other agencies.
Both USAGE and FERC require a minimum
factor of safety of 1.5 against slope
instability, for the loading condition
corresponding to steady seepage
from the maximum storage facility. An
assessment of the correlation of dam
failure probabilities with safety factors
against slope instability suggests an
annual probability of failure of 1 in
1,000,000 for Category I Facilities (those
designed, built, and operated with
state-of-the-practice engineering) and 1
in 10,000 for Category II Facilities (those
designed, built, and operated using
standard engineering practice). This
spans the failure frequency used in our
failure assessment. The advantage of
this approach is that it addresses current
regulatory guidelines and engineering
practices. The disadvantage is that we do
not know whether standard practice or
state-of-the practice dams will perform
as expected, particularly given the large
size of potential dams. In addition, slope
instability is only one type of failure;
other failure modes, such as overtopping
during a flood, would increase overall
failure rates.
Failure of the dam at TSF 1 would result
in the release of a flood of tailings
slurry into the North Fork Koktuli River,
scouring the valley and depositing
tailings several meters (yards) in depth
over the entire floodplain of the river.
The complete loss of suitable salmon
habitat in the North Fork Koktuli River
17
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*
Tributary ofNapotoli Creek, near the Humble claim Photo: Michael Wiedmer
along at least 30 km (18.6 miles) of stream
habitat—the spatial limit of the modeling
conducted for this assessment—in the
short term (fewer than 10 years) and
the high likelihood of very low-quality
spawning and rearing habitat in the long
term (decades) would result in near-
complete loss of mainstem North Fork
Koktuli River fish populations. The North
Fork Koktuli River currently supports
spawning and rearing populations of
sockeye, Chinook, and coho salmon;
spawning populations of chum salmon;
and rearing populations of Dolly Varden
and rainbow trout. The slurry flood
would continue down the Koktuli River
with similar effects, the extent of which
cannot be estimated at this time due to
model and data limitations.
The tailings dam failures evaluated here
are predicted to have the following severe
direct and indirect effects on aquatic
resources, particularly salmonid fish.
(1) It is likely the the North Fork Koktuli
River below the TSF 1 dam, and
much of the Koktuli River, would
not support salmonid fish in the
short term (fewer than 10 years).
• Deposited tailings would
degrade habitat quality for
both fish and the invertebrates
they eat. Based largely on their
copper content, deposited
tailings would be toxic to
benthic macroinvertebrates,
although existing data
concerning toxicity to fish is
less clear.
• Deposited tailings would
continue to erode from the
North Fork Koktuli and Koktuli
River valleys.
• Suspension and redeposition
of tailings would likely cause
serious habitat degradation
in the Koktuli River and
downstream into the
Mulchatna River.
(2) Those waters would provide very
low-quality spawning and rearing
habitat for a period of 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 a failed dam.
18
-------
•'.-
• Ultimately, spring floods and
stormflows would carry some
proportion of the tailings into
the Nushagak River.
• For some years, periods of
high flow would be expected
to suspend sufficient
concentrations of tailings to
cause avoidance, reduced
growth and fecundity, and
even death offish.
(3) Near-complete loss of North Fork
Koktuli River fish populations
would likely result from these
habitat losses.
• The Koktuli River watershed
is an important producer of
Chinook salmon. The Nushagak
River watershed, of which the
Koktuli River watershed is a
part, is the largest producer of
Chinook salmon in the Bristol
Bay region, with annual runs
averaging over 160,000 fish.
• The tailings spill would be
expected to eliminate 28%
of the Chinook salmon run
in the Nushagak River due
to loss of the Koktuli River
watershed population; an
additional 10 to 20% could be
lost due to tailings deposited
in the Mulchatna River and its
tributaries.
• Sockeye are the most abundant
salmon returning to the
Nushagak River watershed,
with annual runs averaging
more than 1.3 million fish.
The proportion of sockeye
and other salmon species of
Koktuli-Mulchatna origin is
unknown.
• Similarly, populations of
rainbow trout and Dolly
Varden would be lost for
years to decades. Quantitative
estimates of the impacts
on population sizes are not
possible.
Effects would be qualitatively the same
for both the partial-volume and full-
volume dam failures, although effects
from the full-volume failure would
extend further and last longer. Failure of
dams at the two additional TSFs under
the maximum mine size (TSF 2 and
19
-------
TSF 3) were not modeled, but would
have similar effects in the South Fork
Koktuli River and downstream. However,
because their volumes would be smaller,
effects would be less extensive.
Pipeline Failures
Under the mine scenario, the primary
product of the mine would be a
concentrate of copper and other metals
that would be pumped in a pipeline to
a shipping facility on Cook Inlet. Water
carrying the sand-like concentrate would
be returned to the mine site in a second
pipeline. Based on the record of pipelines
in general, and the world's largest metal
concentrate pipeline in particular, one to
two near-stream failures of each of these
pipelines would be expected to occur
over the life of the maximum mine (78
years). Failure of either the product or
the return water pipelines would release
water that is expected to be highly toxic,
potentially killing fish and invertebrates
in the affected stream over a relatively
brief period. If concentrate spilled into
a stream, it would settle and form bed
sediment predicted to be highly toxic
based on its high copper content and
acidity. Unless the receiving stream was
dredged, causing additional long-term
damage, this sediment would persist
for decades before ultimately being
washed into Iliamna Lake. Potential
concentrations in the lake could not be
predicted, but near the pipeline route
Iliamna Lake contains important beach
spawning areas for sockeye salmon
that could be exposed to a toxic spill.
Sockeye also spawn in the lower reaches
of streams which could be directly
contaminated by a spill.
Water Collection and Treatment
Failures
There is a long history of unplanned
discharges of contaminated waters
from mine sites into surface and ground
waters. Water in contact with tailings
or waste rock would leach copper and
other metals. The failure of collection
and treatment systems due to imperfect
design or operation, or the failure to
maintain and operate these systems in
perpetuity, could result in contamination
of one or more streams draining the
site. Based on a review of historical and
currently operating mines, some failure
of the collection and treatment systems
is likely during operation or post-closure
periods. These failures could range from
operational failures resulting in short-
term releases of untreated leachates,
to long-term failures to operate the
collection and treatment system in
perpetuity. Our evaluation looked at the
realistic possibility of leachate escaping
at the base of TSF 1. We also considered a
failure to collect and treat leachate from
waste rock piles around the mine pit.
Test leachates from the tailings and
non-ore-bearing Tertiary waste rocks—
those formed between approximately
65 million to 2.5 million years ago—are
mildly toxic; they would require an
approximately two-fold dilution to
achieve water quality criteria for copper,
but they are not expected to be toxic
to salmonids. If Tertiary rock were to
be used as planned for construction
of mining infrastructure, leachate
from these areas would need to be
collected and treated to avoid toxic
effects on benthic invertebrates. Our
risk assessment did not evaluate this
potential pathway in detail.
Pre-Tertiary waste rocks, which would
be excavated to expose the ore body,
are acid-forming with high copper
concentrations in test leachates and
would require 2,900 to 52,000-fold
dilution to achieve water quality
criteria. If leachate from a waste rock
pile surrounding the mine pit was
not collected, the 10.6 million m3
(approximately 2.8 billion gallons) of
leachate per year from the waste rock
pile could constitute source water for
Upper Talarik Creek, which flows to
Iliamna Lake. The total flow of Upper
Talarik Creek would provide only 18-fold
dilution, so failure to prevent leachate
releases could cause the entire creek and
20
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a potentially large mixing zone in the lake
to become toxic to fish and the sensitive
invertebrates upon which they feed. The
significance of such an event to salmon is
illustrated by the abundance of spawning
salmon in Upper Talarik Creek. As many
as 33,000 sockeye and 6,300 coho
spawners have been counted in the creek
on a single day; in 2008, 82,000 sockeye
were counted in Upper Talarik Creek and
one of its tributaries in a single day. The
toxic event described could kill adult fish
or the millions of eggs, larvae, and fry
that they generate.
Road and Culvert Failures
Within the Kvichak River watershed, the
transportation corridor would cross 34
streams and rivers supporting migrating
and/or resident salmonids, including
17 streams designated as anadromous
waters at the location of the crossing.
The most likely serious failure associated
with the transportation corridor would
be blockage or failure of culverts.
Culverts commonly become blocked
by debris that may not stop water
flow but would block fish passage. If
these blockages occurred during adult
salmon immigration or juvenile salmon
outmigration and were not cleared for
several days, production of a year-class
(i.e., fish spawned in the same year) could
be lost or diminished.
Culverts can also fail to convey water as
a result of landslides or, more commonly,
floods that wash out the culvert. In such
failures, the stream could be temporarily
impassible to fish until the culvert is
repaired or until erosion reestablishes
the channel. If the failure occurs during
a critical period in salmon migration,
the effects would be the same as with a
debris blockage (i.e., a lost or diminished
year-class).
Culvert failures also would result in the
downstream transport and deposition of
silt, which could cause returning salmon
to avoid a stream if they arrived during
or immediately following the failure.
More likely, deposition of silt would
smother salmon eggs and larvae, if they
were present, and would degrade the
downstream habitat for salmonid fish
and the invertebrates that they eat.
Extended blockage offish passage
at road crossings is unlikely during
operation assuming best-case scenario
daily inspection and maintenance.
21
-------
Homes near Newhalen Photo: David Allnut (USEPA)
However, after mine operations cease,
the road may be maintained less carefully
or be transferred to a governmental
entity. In that case, the proportion of
culverts that are impassable would be
expected to revert to levels found in
published surveys of public roads (30 to
66%). Of the approximately 50 culverts
that would be required, 17 would be
on streams that are believed to support
salmonids. Hence, over the long term,
4 to 10 streams would be expected to
lose passage of salmon, rainbow trout,
or Dolly Varden, and some proportion
of those streams would have degraded
downstream habitat resulting from the
sedimentation from washout of the road.
Common Mode Failures
Multiple, simultaneous failures could
occur as a result of a common event,
such as the occurrence of a severe storm
with heavy precipitation (particularly one
that fell on spring snow cover) or a major
earthquake. Such an event could cause
one to three tailings dam failures that
would spill tailings slurry into streams
and rivers, road culvert washouts that
would send sediments downstream
and potentially block fish passage, and
pipeline failures that would release
product slurry, return water, or diesel
fuel. The effects of each of these accidents
individually would be the same as discussed
previously, but their co-occurrence would
cause cumulative effects on salmonid
populations and make any mitigative
response more difficult.
Over the perpetual timeframe that
tailings, mine pit, and waste rock
would be in place, the likelihood of
multiple extreme precipitation events,
earthquakes, or combinations of these
events becomes much greater. Multiple
events further increase the chances
of weakening and eventual failure of
facilities that are still in place.
Overall Loss of Wetlands
Wetlands are a dominant feature of
the landscape in the Pebble deposit
area and throughout the Bristol Bay
watershed, and are important habitats
for salmon and other fish. Ponds and
riparian wetlands provide spawning,
rearing, and refuge habitat for both
anadromous salmonids and resident fish
species. Other wetlands moderate flows
and water quality, and can influence
downstream delivery of dissolved
22
-------
organic matter, particulate organic
matter, and aquatic macroinvertebrates
that supply food sources to fish. Under
the mine scenario, wetlands would be
filled or excavated in 10.2 km2 (2,512
acres) and 17.3 km2 (4,286 acres) of
the minimum and maximum mine
footprints, respectively. An additional
1.9 km2 (481 acres) and 1.1 km2 (267
acres) of riparian wetlands would be
blocked by the minimum and maximum
footprints, respectively, and would be
lost or suffer substantial changes in
hydrologic connectivity with streams as
a result of reduced flow from the mine
footprint. Another 0.18 km2 (44 acres) of
wetlands would be filled in the Kvichak
River watershed by the roadbed of the
transportation corridor. By interrupting
flow and adding silt and salts, the
roadbed would also affect approximately
2.4 to 4.9 km2 (593 to 1,211 acres) of
wetlands. Finally, a tailings or product
concentrate spill could damage wetlands
and eliminate or degrade their capacity
to support fish.
Fish-Mediated Risk to Wildlife
Although the effects of reduced
salmon, trout, and char production
on wildlife—the fish-mediated risk to
wildlife—cannot be quantified given
available data, some reduction in wildlife
would be expected under the mine
scenario. Changes in the occurrence
and abundance of salmon have the
potential to change animal behavior and
reduce wildlife population abundances.
Assuming no failures, routine operations
would be expected to have local effects
on brown bears, wolves, bald eagles, and
other wildlife that consume salmon as
a result of reduced salmon abundance
from the loss and degradation of habitat
in or immediately downstream of the
mine footprint. Any of the accidents or
failures evaluated would increase effects
on salmon, which would proportionately
reduce the abundance of their predators.
The abundance and production of
wildlife also is enhanced by the marine
nutrients that salmon carry on their
spawning migration. Those nutrients are
released into streams when the salmon
die, enhancing the production of other
aquatic species that feed wildlife. Salmon
predators deposit these nutrients on
the landscape, thereby fertilizing the
vegetation and increasing the abundance
and production of moose, caribou, and
other wildlife that depend on vegetation
for food.
Fish-Mediated Risk to
Indigenous Culture
Under routine operations with no major
accidents or failures, the predicted loss
and degradation of salmon, char, and
trout habitat in North Fork Koktuli and
South Fork Koktuli Rivers and Upper
Talarik Creek is expected to have some
impact on Alaska Native cultures of
the Bristol Bay watershed. Fishing and
hunting practices are expected to
change in direct response to the stream,
wetland, and terrestrial habitats lost due
to the footprints of the mine site and the
transportation corridor. Additionally, it
is also possible that subsistence use of
salmon resources could decrease based
on the perception of reduced fish or
water quality resulting from mining.
The potential for significant effects on
indigenous cultures is much greater
from a mine failure than from routine
operations. As described above,
failures could reduce or eliminate
fish populations in affected areas,
including areas significant distances
downstream from the mine. Any loss
offish production from these potential
failures would reduce the availability
of those subsistence resources to local
Alaska Native villages, and the reduction
of food supply potentially would have
negative consequences on human
health if alternative food resources are
not available. Salmon-based subsistence
is integral to Alaska Native cultures. If
salmon quality or quantity is adversely
affected, the nutritional, social, and
spiritual health of Alaska Natives and their
culture will potentially decline.
23
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Cumulative Risks
This assessment has focused on the
potential effects of a single, hypothetical
mine on salmon and other resources
in the Nushagak and Kvichak River
watersheds, including the cumulative
effects of multiple stressors associated
with that mine. However, the potential
exists for development of multiple mines
and associated infrastructure in these
watersheds. Each potential mine poses
risks similar to those identified for the
mine scenario. Estimates of the loss of
stream and wetland habitats would differ
across different deposits based on the
size and location of mining operations
within the watersheds. Individually, each
mine footprint would eliminate some
amount offish-supporting habitat and,
should human or engineering failures
occur, affect fish habitats beyond the
mine footprint. Cumulatively, multiple
mines have the potential to decrease the
abundance and genetic diversity offish
populations and thereby increase their
annual variability.
We considered development of mines
at several sites in the Nushagak River
watershed, including Big Chunk,
Groundhog Mountain, and Humble
claims. These sites were chosen, because
all contain copper deposits that have
generated exploratory interest. If
all four mine sites were developed,
the cumulative area covered byTSFs
alone would be close to 73 km2 (19,038
acres). Loss of stream habitats as a
result of eliminated or blocked streams
could reach 233 km (144 miles). The
combined facilities would eliminate
an estimated 34.6 km (21.5 miles) of
documented salmon streams. The length
of salmon stream affected is likely an
underestimate, because most streams
have not been sampled for the presence
of salmon. Loss of these distinct streams
would likely result in the loss of their
associated salmon populations, reducing
the genetic and life-history diversity
generated through the existence of
numerous distinct populations.
Summary Of Uncertainties In
Mine Design And Operation
This assessment of a hypothetical
mine scenario is generally applicable
to the copper deposits in the Bristol
Bay watershed and is based on specific
characteristics of the Pebble deposit.
The mine scenario does not represent
the plans of any mining company; if
the resource is mined in the future,
actual events will undoubtedly deviate
from this scenario. This is not a source
of uncertainty, but rather an inherent
aspect of a predictive assessment.
Even an environmental assessment of
a proposed plan by a mining company
would be an assessment of a scenario
that undoubtedly would differ from the
ultimate development.
Multiple uncertainties are inherent
in planning, designing, constructing,
operating, and closing a mine.
• Mines are complex systems requiring
skilled engineered design and
operation. The uncertainties facing
mining and geotechnical engineers
include unknown geologic defects,
uncertain values in geological
properties, limited knowledge
of mechanisms and processes,
and human error in design and
construction. Vick (2002) notes
that models used to predict the
behavior of an engineered system
are "idealizations of the processes
they are taken to represent, and it is
well recognized that the necessary
simplifications and approximations
can introduce error in the model."
Engineers use professional judgment
in addressing uncertainty (Vick 2002).
• Accidents are inherently
unpredictable. Though systems can
be put into place to protect against
system failures, seemingly logical
decisions about how to respond to a
given situation can have unexpected
consequences resulting from human
error (e.g., the January 2012 overflow
of the tailings dam at the Nixon Fork
24
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Mine near McGrath, Alaska). Further,
unforeseen events or events that are
more extreme than anticipated can
negate the apparent wisdom of prior
decisions (Caldwell and Charlebois
2010).
The ore deposit would be mined for
decades and the waste would require
management for centuries or even in
perpetuity. Engineered waste storage
systems of mines have only been in
existence for about 50 years. Their
long-term behavior is not known.
The response of our best technology
in the construction of tailings dams is
untested and unknown in the face of
centuries of extreme events such as
earthquakes and weather.
Mine management or ownership
may change over time. Over the
long timespan (centuries) of mining
and post-mining care, generations
of mine operators must exercise
due diligence. Priorities are likely
to change in the face of financial
circumstances, changing markets for
metals, new information about the
resource, political priorities, or any
number of currently unforeseeable
changes in circumstance.
Such uncertainties are inherent in
any complex enterprise, particularly
when they involve an incompletely
characterized natural system. However,
the large scales and long durations
implied by the effort required to exploit
this resource make these inherent
uncertainties more prominent.
Summary of Uncertainties and
Limitations in the Assessment
Significant uncertainties about and
limitations of the estimated potential
effects of the mine scenario, as judged
by the assessment authors, include the
following.
• Any mine plan submitted by a mining
company may not exactly reflect the
location and sizes of the mine pit,
waste rock pile, and tailings storage
facilities, and the location and length
of the transportation corridor used
in the scenario for this assessment.
An actual mine plan may be smaller,
larger, or laid out differently than the
mine scenario considered here.
• The estimated annual probability
of tailings dam failure is uncertain
and based on both design goals and
25
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Kvichak River below Iliamna Lake and Igiugig Photo: Joe Ebersole (USEPA)
historical experience. Actual failure
rates could be higher or lower than
the estimated probability.
The proportion of the tailings that
would spill in the event of a dam
failure could be larger than the
largest value modeled (20%).
The long-term fate of the spilled
tailings in the event of a dam failure
could not be quantified. Analogous
to other cases, it is likely that tailings
would erode from the areas of initial
deposition and move downstream
over a period of more than a decade.
However, the data needed to model
that process and the resources
needed to develop that model were
not available.
Consequences of the loss and
degradation of habitat on fish
populations could not be quantified
because of the lack of quantitative
information concerning salmon,
char, and trout populations. The
occurrence of salmonid species in
rivers and major streams is known,
but information on abundances,
productivities, and limiting factors
within each of the watersheds is
not available. Estimating changes
in populations would require
population modeling, which requires
knowledge of life stage-specific
survival and production as well as
knowledge of limiting factors and
processes that are not available.
Further, it requires knowledge of how
temperature, habitat structure, prey
availability, density dependence,
and sublethal toxicity influence
life stage-specific survival and
production, which is not available.
Obtaining that information would
require more detailed monitoring
and experimentation. Further,
salmon populations naturally vary in
size because of a great many factors
that vary among locations and years.
Collecting sufficient data to establish
reliable salmon population estimates
takes many years. Estimated effects
of mining on habitat become the
available surrogate for estimated
effects on fish populations.
Standard leaching test data are
available for test tailings and waste
rocks from the Pebble deposit,
but these results are uncertain
predictors of the actual composition
of leachates from tailings
26
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,.**L
NewStuyahok Photo: David Allnut (USEPA)
impoundments, tailings deposited in
streams and on their floodplains, and
waste rocks in piles.
The effects of tailings and product
concentrate deposited in spawning
and rearing habitat are uncertain. It
is clear that they would have harmful
physical and toxicological effects
on salmonid larvae or sheltering
juveniles, but the concentration in
spawning gravels required to reduce
salmonid reproductive success is
unknown.
The actual response of Alaska Native
cultures to any impacts of the mine
scenario is uncertain. Interviews with
village elders and culture bearers,
and other evidence suggest that
responses would involve more than
the need to compensate for lost
food and would likely include some
degree of cultural disruption. It is not
possible to predict specific changes
in demographics, cultural practices,
or physical and mental health.
27
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Salomone, P., S. Morstad,T. Sands, and M.Jones. 2009. Salmon spawning ground surveys in the Bristol Bay
Area, Alaska, 2008; Fishery Management Report No. 09-42. Alaska Department of Fish and Game, Division of
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Salomone, P. Area Management Biologist, Alaska Department of Fish and Game. Unpublished data.
Vick, S. G. 2002. Degrees of Belief: Subjective Probability and Engineering Judgement. American Society of Civil
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Photo Credits
Front Cover, Main Photo....
Front Cover, Thumbnail 1.
Front Cover, Thumbnail 2.
Front Cover, Thumbnail 3.
Front Cover, Thumbnail 4.
Inside Front Cover
Inside Back Cover
Back Cover
. Upper Talarik Creek, Joe Ebersole (USEPA)
. Brown bear, Steve Hillebrand (USFWS)
. Fishing boats at Naknek, Alaska, USEPA
. IliamnaLake, Lorraine Edmond (USEPA)
. Sockeye salmon in the Wood River, Thomas Quinn (University of Washington)
. Sockeye salmon in the Wood River, Thomas Quinn (University of Washington)
. Sockeye salmon in the Wood River, Thomas Quinn (University of Washington)
. Tributary ofNapotoli Creek, near the Humble claim, Michael Wiedmer
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