Comments on the Twin Metals Mine Plan

Acting Director Pendley and Commissioner Strommen
August 31, 2020
Page 3
IV.
Our Team of Experts Is Available to Assist the Bureau of Land Management and the
Minnesota Department of Natural Resources in Analyzing TMM's Mine Plan of
Operation.
We have assembled a team of experts with backgrounds in geology, hydrology, biology, chemistry,
and risk assessment, who collectively have worked for over a century in Minnesota and throughout
six continents on the impacts of mining on terrestrial and aquatic environments. Given the range and
depth of their expertise, they welcome the opportunity to assist BLM and DNR in analyzing current
and future aspects of TMM's Mine Plan of Operation.
If you have any questions or would like additional information regarding the enclosed <strong>Comments</strong>,
please contact me at any time at 651.999.9565, chris@friends-bwca.org or at the above address.
Sincerely,
A
Christopher D. Knopf
Executive Director
Friends of the Boundary Waters Wilderness
cc:
Derek Strohl, U.S. Bureau of Land Management
Northeastern States District Office ( w / encl.)
Jess Richards, Minnesota Department of Natural Resources
Assistant Commissioner (w /encl.)

COMMENTS OF
FRIENDS OF THE BOUNDARY WATERS WILDERNESS
AND
MINNESOTA CENTER FOR ENVIRONMENTAL ADVOCACY,
ON
ENVIRONMENTAL REVIEW SUPPORT DOCUMENTS
SUBMITTED BY TWIN METALS MINNESOTA DATED DECEMBER 18, 2019
MINE PLAN OF OPERATIONS (TMM-ES-115-0001, REV. 0A)
AND
SCOPING ENVIRONMENTAL ASSESSMENT WORKSHEET DATA SUBMITTAL
(TMM-ES-025-0099, REV. 0A)
AUGUST 31, 2020

Table of Contents
I. Introduction ..................................................................................................................................... 1
II. Executive Summary ....................................................................................................................... 4
A. TMM Must Provide Detailed Data Regarding the Mineral and Chemical
Composition of Rock Types in the Project Area to Assess the Potential Risk of
Surface and Groundwater Contamination, Acid Mine Drainage, and Asbestiform
Mineral Releases, and to Evaluate the Economic Feasibility of the Mine. ................... 4
B. TMM Must Identify the Chemical Content of Mine Water, Explain how the
Process Water Will Continue to Function Once Saturated with Salts, Improve the
Safety Margin for Catastrophic Release of Untreated, Contaminated Water and
Solids to the Environment, and Plan for Monitoring and Remediation After Mine
Closure. ................................................................................................................................................... 5
C. TMM Must Demonstrate That It Can Produce Tailings with only 13-16% Water
Content, Demonstrate That the Filtered Tailings Storage Facility (FTSF) Fulfills All
Dam Safety Laws, Provide Data on How Much Mine Water Will Leak Through
Liners, and Demonstrate Feasibility of Growing Vegetation on the FTSF. .................. 6
D. TMM Must Provide Complete Chemical Characterization of All Materials to be
Handled at the Proposed Mine Site and Their Degradation Products, Including
Draindown Water and Fine Particles from the FTSF, and Must Identify and Estimate
the Effects on Human, Wild Rice, and Environmental Health from Release of
Dissolved Sulfate. ............................................................................................................................... 6
E. TMM Must Determine the Environmental Toxicity to Fish and Wildlife of All
Materials to Be Handled at the Proposed Mine Site and Their Degradation Products,
in Which They Must Consider All Wildlife Including Birds Migrating Along the
Mississippi Flyway, Estimate Potential Fisheries Damage, and Engage in a Rigorous
U.S. Fish and Wildlife Service Consultation Process. ............................................................ 7
F. TMM Must Identify and Mitigate Any Effects on Northern Minnesota’s Iconic
Boreal Forest. ....................................................................................................................................... 8
G. TMM Must Address Additional Areas of Concern including Human Health,
Hazardous Materials, Impacts to Visual, Noise, and Transportation Resources,
other Effects on the Environment, and Wetland Restoration. .......................................... 8
H. TMM Must Provide Robust Monitoring and Contingency Planning for All Stages
of Mine Operations. ........................................................................................................................... 9
III. Factual Background .................................................................................................................... 10
A. The Duluth Complex ............................................................................................................... 10
B. Waters of Northeastern Minnesota .................................................................................. 10
C. Mine Plan of Operations (MPO) ......................................................................................... 12

D. Scoping Environmental Assessment Worksheet Data Submittal (SEAWDS) .. 12
E. Scoping Standards under State and Federal Law ....................................................... 13
IV. Scoping <strong>Comments</strong> ..................................................................................................................... 15
A. Geology of the Project Area ................................................................................................. 15
1. Chemical and Mineralogical Composition of Rock Types ............................... 15
2. Geological Structure within the Project Area ...................................................... 17
3. Economic Geology and Analysis ............................................................................... 19
4. Rock Management and Material Characterization ............................................ 21
5. The Likelihood of Acid Mine Drainage ................................................................... 23
B. Mine Water ................................................................................................................................ 26
1. Water Balance ................................................................................................................. 26
2. The Use of 100% Recycled Mine Water ................................................................ 29
C. Filtered Tailings Storage Facility (FTSF) ........................................................................ 30
1. Chemicals Added to the Surface of the FTSF ....................................................... 30
2. Liners for the FTSF, Mine Water Storage Ponds and Crushed Rock
Locations ........................................................................................................................................ 31
3. Soils to Cover the FTSF ................................................................................................ 31
4. Target Water Content for Filtered Tailings .......................................................... 32
5. Temporary Storage of Uncompacted Tailings .................................................... 33
6. Lack of Adherence to Dam Safety Requirements ............................................... 35
7. Infrastructure to Prevent Rewetting of Stored Filtered Tailings ................ 37
8. Incompatibility of Filtered Tailings and Zero Water Discharge/Zero Water
Treatment ...................................................................................................................................... 38
D. Production and Release of Chemicals.............................................................................. 39
1. Analysis of Movement of Chemicals ....................................................................... 39
2. Sulfate and Dangers to Aquatic Ecosystems and Wild Rice ........................... 40
3. Beneficiation Reagents................................................................................................. 45
4. Other Compounds .......................................................................................................... 45
5. Asbestiform Minerals ................................................................................................... 45
E. Potential for Fish and Wildlife Impacts .......................................................................... 46
1. Contaminants of Potential Concern ........................................................................ 46
2. Ecological Receptors among Fish and Wildlife ................................................... 47
3. Potential Sources of Contaminants and Exposure ............................................ 48
4. Ecotoxicity of Contaminants Associated with the Project .............................. 49

F. Potential for Boreal Forest Impacts ................................................................................. 52
G. Other Known Impacts Not Here Addressed .................................................................. 54
H. Monitoring and Continency Planning .............................................................................. 54
V. Conclusion ...................................................................................................................................... 55
VI. Experts who Contributed to this Report ............................................................................ 57
VII. Citations .......................................................................................................................................... 59

I. Introduction
Friends of the Boundary Waters Wilderness (Friends) and the Minnesota
Center for Environmental Advocacy (MCEA) are submitting these comments
(<strong>Comments</strong>) to direct the scope of the Environmental Impact Statements (EISs) that
the Bureau of Land Management (BLM) and the Minnesota Department of Natural
Resources (DNR) will be conducting to evaluate Twin Metals Minnesota’s (TMM’s)
Mine Plan of Operations (MPO) and Scoping Environmental Assessment Worksheet
Data Submittal (SEAWDS).
The Friends is a Minnesota nonprofit organization that has led the fight to
protect the Boundary Waters Canoe Area Wilderness for more than forty years. The
Friends has more than 4,000 members who share our mission of protecting,
preserving and restoring the Boundary Waters Canoe Area Wilderness (BWCAW) and
the Quetico-Superior ecosystem. Our members and followers have a profound and
enduring interest in ensuring that actions proposed in and near the BWCAW protect
the wilderness character and biological integrity of the Quetico-Superior ecosystem.
The Minnesota Center for Environmental Advocacy is a nonprofit
organization of policy professionals and environmental lawyers who work together
to protect Minnesota’s environment, its natural resources, and the health of its
people.
TMM proposes a copper-sulfide mine adjacent to the Boundary Waters Canoe
Area Wilderness (BWCAW), which consists of more than one million acres and 1,100
lakes connected by an in intricate network of rivers, streams, and portage trails. The
BWCAW is visited by more than 150,000 people each year, and provides substantial
contributions to the region’s economy.
Friends and MCEA, in cooperation with a team of Experts, have identified a
large number of alarming deficiencies in the SEAWDS and MPO that, taken together,
indicate that TMM will not be able to safely and economically operate its proposed
mine.
In its submitted documents, TMM consistently underreports and underanalyzes
data concerning the existing mineralogy, geology, hydrology, and biology of
the area in which it proposes to operate; adopts mine construction, operation,
closure, and post-closure monitoring plans without considering alternative plans or
explaining why it has opted for the various plans it has chosen; and ignores,
understates, and/or fails to plan for remedial measures for the range of impacts that
its proposed operations would have on the surrounding waters, forests, wildlife,
ecosystems, and human health. The MPO and SEAWDS lack comprehensive
monitoring plans for the site and affected resources, and they contain neither any
1

contingency plans to address adverse outcomes nor any statements of intention to
develop contingency plans.
BLM and DNR must hold TMM to a much higher standard. The failure to have
an appropriate scope for the EIS will result in a review process that is incomplete and
not protective of the environment (in this case, a unique and irreplaceable American
Wilderness), as required by federal and state law. Given such systemic shortcomings
of data and analysis, and the low grade of the ore proposed to be mined, expert
analysis must address whether TMM’s mining plan is even economically feasible, and
further study the consequences of subjecting the people of northern Minnesota to a
new economic boom-bust cycle based on resource extraction. For instance, a Harvard
economics study predicts that the very short-term (about five-year-long) economic
benefit of the proposed project would be wiped out in a few more years, due to the
effects of the presence of the mine and its environmental damage, and that the region
would then be economically worse off than before. 1
The <strong>Comments</strong> were prepared by a team of experts (Experts) with specialized
knowledge in mining and its environmental impacts, as well as the Project area and
its geology. Fredrick K. Campbell has experience in economic geology and mineral
exploration, as well as water contamination at Superfund sites. Steven H. Emerman
has studied and worked in issues of hydrology and mining for over 40 years. Bruce
Johnson has 30 years of experience in water quality and waste management,
including in copper-nickel mining. Amy Myrbo’s expertise is in human impacts to
lakes, wetlands, and wild rice waters, including the many and often unrecognized
dangers of sulfate. Diana M. Papoulias has expertise in the effects of contaminants on
aquatic species and the impacts on indigenous and rural communities of extractive
industries. Gerald J. Stahnke worked for over 40 years in the Superfund Program and
on the impacts of copper-nickel mining.
Following the Executive Summary, Part III of these <strong>Comments</strong> reviews the
factual background for TMM’s proposed copper-sulfide mine, including the region’s
geology and hydrology, and addresses scoping standards under federal and state law.
Part IV provides specific scoping comments with respect to the following topics:
A. Geology of the Project Area
B. Mine Water
C. Filtered Tailings Storage Facility
D. Production and Release of Chemicals
E. Fish and Wildlife Impacts
F. Boreal Forest Impacts
1 Stock JH, Bradt JT. Analysis of Proposed 20-year Mineral Leasing Withdrawal in Superior National
Forest. Working Paper.
2

G. Other Known Impacts Not Addressed Here
H. Monitoring and Contingency Planning
Part V provides concluding statements, Part VI provides biographies of the Experts,
and Part VII provides a list of literature cited in these <strong>Comments</strong>.
This long list of major problems shows that TMM will not be able to protect
environmental and human health, and that the proposed Project may not even
be economically feasible. Together, these concerns underscore the
determination that this is the wrong mine at the wrong location.
3

II.
Executive Summary
In its Environmental Review Support Documents, Twin Metals Minnesota
(TMM) consistently:
(1)Underreports and under-analyzes data concerning the existing mineralogy,
geology, hydrology, and biology of the area in which it proposes to operate;
(2) Adopts mine construction, operation, closure, and post-closure monitoring
plans without considering alternative plans or explaining why it has opted for the
various plans it has chosen; and
(3) Ignores, understates, and/or fails to plan for remedial measures for the
range of impacts that its proposed operations would have on the surrounding waters,
forests, wildlife, and ecosystems.
Given such systemic shortcomings of data and analysis, and the low grade of
the ore proposed to be mined, BLM and DNR (collectively, the Regulatory Agencies)
must require TMM to engage an independent expert to determine whether TMM’s
mining plan is economically feasible.
But first, that independent expert will need sufficient data on and analysis of
(1) the surrounding mineralogy, geology, hydrology and biology; (2) the limitations
and risks of implementing TMM’s construction, operations, closure and monitoring
plans; and (3) the range of the plans’ negative impacts on the surrounding waters,
forests, wildlife, and ecosystems. To identify necessary information, the Regulatory
Agencies must require TMM to gather and submit information in a number of critical
areas, as described below.
A. TMM Must Provide Detailed Data Regarding the Mineral and Chemical
Composition of Rock Types in the Project Area to Assess the Potential Risk of
Surface and Groundwater Contamination, Acid Mine Drainage, and
Asbestiform Mineral Releases, and to Evaluate the Economic Feasibility of the
Mine.
TMM needs to provide detailed data regarding the mineralogical and chemical
composition of rock types that are likely to be encountered in the Project area. It must
also identify the presence and location of fault, fracture, and alteration (e.g.,
serpentinization) zones in the Project area, because these are relevant to surface- and
groundwater contamination, asbestiform mineral release, and economic feasibility of
the mine.
TMM must develop detailed plans for analysis of chloride content of mine
water and interactions with anticipated lithologies and mineralogies of the mined
rock. TMM must submit data regarding the range of sulfide deposits, including
information about their nature and distribution as well as data regarding mineralogy
and chemistry. Chloride affects metal leaching, and dissolved sulfate and dissolved
sulfide have dangerous ecosystem effects.
With regard to static or kinetic testing results for the material characterization
4

program that have already been collected by TMM or by other parties in the Project
area or in adjacent areas in the Duluth Complex, TMM must submit all such testing
results, because of the danger of acid mine drainage (AMD).
TMM must use multiple methods to calculate AMD potential and provide a
timeline of when AMD would begin, the monitoring plan necessary to detect AMD,
and the actions that would be taken in response to the appearance of AMD, because
of permanent damage to ecosystems that would be caused by AMD.
B. TMM Must Identify the Chemical Content of Mine Water, Explain How
the Process Water Will Continue to Function Once Saturated with Salts,
Improve the Safety Margin for Catastrophic Release of Untreated,
Contaminated Water and Solids to the Environment, and Plan for Monitoring
and Remediation After Mine Closure.
TMM proposes to indefinitely recycle water used on site, and does not include
any water treatment facilities in its proposed Project site. TMM needs to identify the
chemical content of site water with regard to regulatory and toxicological
benchmarks; explain how the process water will continue to function for ore
beneficiation once it has become saturated with salts; and explain how TMM would
address the precipitation of salts from the saturated process water. Contaminated,
untreated water and precipitates stored on site represent unacceptable risks to the
environment.
TMM’s plan for water storage on site allows for a 22% possibility of a
catastrophic release of untreated waste into the environment during the proposed
25-year operation of the mine, and additional risks of a post-closure release. All water
storage infrastructure needs instead to be designed to accommodate a 24-hour storm
with a 1000-year return period or a 1000-year snowpack. Release of contaminated,
untreated water and sediment to Birch Lake, the Kawishiwi River, the Boundary
Waters Canoe Area Wilderness (BWCAW), Ontario’s Quetico Park, and Voyageurs
National Park represents unacceptable risks to the environment.
TMM needs to provide estimates with uncertainties for all components of the
water balance, including groundwater inflow, precipitation, surface runoff,
evaporation, storage of water in filtered tailings, and export of water in the metal
concentrates, because mining operations would need to be built to accommodate
these uncertainties.
TMM must also provide estimates with appropriate uncertainties of the
changes in Birch Lake’s water level and local stream flows that would result from
mine dewatering and from use of water resources for mine processes. Water is the
lifeblood of ecosystems and human communities in the proposed Project area.
TMM needs to submit a plan for construction and operation of the water
treatment facility that would be needed before temporary or final closure of the
mining operation, and to demonstrate that if temporary closure occurred due to
economic reasons, TMM would at that time have the financial ability to immediately
build the required water treatment facility, to avoid the release of untreated mine
5

waste into the environment.
TMM’s must prepare and submit a plan for long-term monitoring of the mine
water that would be released from the water storage facility or other components of
the mining operation following temporary or final mine closure, because effects will
continue long after the proposed mine would cease operation.
C. TMM Must Demonstrate That It Can Produce Tailings with Only 13-16%
Water Content, Demonstrate That the Filtered Tailings Storage Facility (FTSF)
Fulfills All Dam Safety Laws, Provide Data on How Much Mine Water Will Leak
Through Liners, and Demonstrate Feasibility of Growing Vegetation on the
FTSF.
Filtered tailings in TMM’s proposed FTSF are not dry, but have at least 13-16%
water content, so the term “dry stack facility” is misleading and must not be used.
Given current technology, the still-unknown heterogeneity of the ore body,
and the mine site’s weather conditions, TMM needs to demonstrate the ability to
consistently produce filtered tailings with only 13-16% water content. Higher water
content, as is likely according to TMM’s own consultants, would reduce the stability
of the FTSF and increase the likelihood that it will collapse catastrophically.
TMM needs to demonstrate that the structural zone (which serves the same
function as a dam) of the proposed FTSF will fulfill all state and federal dam safety
laws and regulations and that its diversion dikes, overdrains, and underdrains are
designed to ensure that the FTSF can withstand the appropriate design flood in
accordance with dam safety laws and regulations, because the lack of a dam for the
proposed FTSF violates Minnesota Rules Chapter 6115.0320, Subpart 5.
With respect to the liners under the FTSF and other waterways in the Project
area, TMM needs to provide manufacturer warranties and test data regarding liner
defects, leaks, and useful lifetimes; to estimate the potential cumulative volume of
liner leakage; and to estimate the potential environmental impacts of leakage,
because all liners leak. TMM also needs to study the potential environmental impacts
of the chemicals proposed to be added to the surface of the FTSF, because some of
these chemicals are toxic.
Regarding the soil that would cover the FTSF, TMM needs to identify the
location(s) of that future soil cover, including artificial soils, and prove them to be
legally held so that they will be accessible at any time for revegetation. TMM also
needs to conduct and provide a study of the identified natural soils/artificial soils and
nutrient content in order to demonstrate the ability of such soils and tailings to
support vegetative growth needed to successfully cover the FTSF and anchor the
topsoil to the tailings during operations or at closure, because revegetation of tailings
is known to be fraught with difficulty.
D. TMM Must Provide Complete Chemical Characterization of All Materials
to Be Handled at the Proposed Mine Site and Their Degradation Products,
Including Draindown Water and Fine Particles from the FTSF, and Must
6

Identify and Estimate the Effects on Human, Wild Rice, and Environmental
Health from Release of Dissolved Sulfate.
In order to assess the environmental impacts of its mining plan, TMM needs to
present complete chemical characterization data including, but not limited to: (a)
total inorganic chemical analyses (i.e., whole rock geochemical analyses) of all rock
types to be removed; (b) full organic and inorganic chemical characterization of dust
suppression chemicals proposed to be applied to the FTSF; (c) any cementitious
materials to be used for engineered tailings backfill or grouts; (d) all beneficiation and
thickening chemicals; and (e) all materials destined for the FTSF. Degradation
products of these chemicals must be included, and bioassays to determine levels of
toxic effects must also be presented, because of the deleterious effects these materials
could have on human and ecosystem health. Data developed must be sufficient to
conduct both environmental and human health risk assessments, consistent with EPA
guidelines.
In addition, TMM needs to calculate the quantity and composition, with
uncertainties, of draindown from the FTSF, including mineralogical and chemical
analyses of the very fine particles that would be deposited with tailings, holding pond
sediments (the source of dredge spoils that will be deposited on the FTSF), and from
dust control. Rain and snow would transport these contaminants into the holding
ponds through draindown, where they would be accessible by wildlife and could be
catastrophically released if the holding ponds overflow.
Given the new science concerning the impacts of sulfate on water quality in
Minnesota, TMM needs to provide estimates (with uncertainties) for the sulfate
concentrations of all proposed Project site waters over time. It must disclose its
proposed process (if any) for removing sulfate from water used on site and the
disposal method for the resulting products. TMM must also identify the potential
effects of sulfate release from the Project on all wild rice populations; on
methylmercury levels in water and in fish; and on nutrient levels, pH, and water
clarity in waters downstream of the mine, because sulfate contamination could
irrevocably alter these parameters, regardless of whether AMD occurs.
With respect to the engineered tailings backfill final product, TMM needs to
provide characterization of that product, including chemistry, mineralogy, porosity,
and permeability, because this material could release sulfate and other chemicals into
groundwater and from groundwater into surface water.
E. TMM Must Determine the Environmental Toxicity to Fish and Wildlife of
All Materials to Be Handled at the Proposed Mine Site and Their Degradation
Products, in Which They Must Consider All Wildlife Including Birds Migrating
Along the Mississippi Flyway, Estimate Potential Fisheries Damage, and
Engage in a Rigorous U.S. Fish and Wildlife Service Consultation Process.
TMM needs to identify the potential environmental toxicity of each of the
chemicals identified in the Environmental Review Support Documents, their
degradation byproducts, and their combined effects, because these chemicals will be
7

eleased into the environment.
In assessing risks to all terrestrial and aquatic wildlife (including aquatic
invertebrates), plants, and habitat, TMM must focus not only on sensitive or protected
species but also on all resident, transient, and migratory species, including birds
migrating along the Mississippi Flyway, to protect northern Minnesota’s unique
ecosystems and their contribution to global environmental health and conservation.
TMM needs to provide independent economic evaluations of the impact of the
proposed mine on ecosystem services and on fisheries, because the value of these
losses needs to be considered by the affected stakeholders.
TMM must explain how it will prevent animals from colonizing chemical-laden
ponds or ingesting materials in the Project area.
TMM must also provide baseline sediment and water quality data for lakes,
ponds, wetlands, rivers, and streams in the watersheds that would be affected by the
Project. Specifically, TMM needs to provide estimates of environmental impact and
remediation costs for a catastrophic release of untreated mine waste to Birch Lake
and downstream waters including the BWCAW, because the proposed Project has a
22% chance of such a release in the 25 years of mine operations. Beyond the 25 years
of mine operations, the risk is ongoing, should a post-closure release occur.
F. TMM Must Identify and Mitigate any Effects on Northern Minnesota’s
Iconic Boreal Forest.
TMM must submit a study on the potential impacts of its plant construction,
operations, and closure on adjacent and downstream forests, and a plan to prevent
those impacts. In addition to its value as an ecosystem, the boreal forest is iconic of
northern Minnesota.
G. TMM Must Address Additional Areas of Concern including Human
Health, Hazardous Materials, Impacts to Visual, Noise, and Transportation
Resources, Other Effects on the Environment, and Wetland Restoration.
TMM must assess risks to human health from the chemicals it would release
into the environment and their byproducts, including asbestiform minerals, heavy
metals, and methylmercury.
TMM must include scoping of each of the twelve resources it identifies in the
SEAWDS, because at present it fails to call for even future scoping of Contamination/
Hazardous Materials/Wastes, Visual, Noise, Transportation, Cumulative Potential
Effects, and Other Potential Environmental Effects.
TMM must present its plan for post-closure wetland restoration in the areas
that would be cleared of vegetation for the Project area, because it has
inappropriately lumped wetlands together with “terrestrial” resources in TMM
documents.
8

H. TMM Must Provide Robust Monitoring and Contingency Planning for All
Stages of Mine Operations.
TMM needs to provide a monitoring plan and decision making resources for
all stages of mine operations, including post-closure, and contingency plans that will
be carried out in the event of adverse observations, because preparation for
unanticipated events should decrease the severity of negative outcomes.
This long list of major problems shows that TMM will not be able to protect
environmental and human health, and that the proposed Project may not even
be economically feasible. Together, these concerns underscore the
determination that this is the wrong mine at the wrong location.
9

III.
Factual Background
On December 18, 2019, Twin Metals Minnesota (TMM) submitted a Mine Plan
of Operations (MPO) to the U.S. Bureau of Land Management (BLM) and the
Minnesota Department of Natural Resources (DNR). Additinally, TMM also submitted
a Scoping Environmental Assessment Worksheet Data Submittal (SEAWDS) to DNR.
BLM and DNR are collectively referred to as the “Regulatory Agencies.” 2 The
documents describe a plan to construct, operate, and then, after 25 years of operation,
close and monitor (for an unspecified period of time) a mining project to extract
copper, nickel and other metals from the South Kawishiwi Intrusion (SKI) of the
Duluth Complex.
A. The Duluth Complex
The Duluth Complex, located in northeastern Minnesota, is part of the
Midcontinent Rift System and is estimated to contain more than 4.4 billion tons of
material averaging 0.66 percent copper and 0.2 percent nickel (Listerud and Meineke,
1977). It hosts four distinct types of magmatic mineral deposits: (1) large bodies of
low-grade, disseminated copper-nickel sulfide minerals, some with local zones
enriched in platinum group elements (PGEs); (2) localized high-grade zones of
massive copper-nickel sulfides, some moderately enriched in PGEs; (3) strata-bound
PGE-enriched reefs associated with specific types of phase-layer transitions; and (4)
oxide-rich ultramafic zones that, in some instances, are potential sources of titanium
and vanadium (Miller et al., 2002). Experts in the geology of the Duluth Complex have
characterized the copper-nickel and other metallic mineralization as “borderline
chaotic” (Patelke and Severson, 2005) and have also emphasized that the stratigraphy
and mineralogy of the Duluth Complex is highly heterogeneous over very short
distances (Severson, 1994; Figure 2).
B. Waters of Northeastern Minnesota
The proposed tailings management site (one mile to the south of the mine)
would lie as close as 400 feet to the Kawishiwi River in northeastern Minnesota
(SEAW Fig 3-13). The water body that TMM refers to as the “Birch Lake Reservoir” is
a dammed section of the Kawishiwi River. Downstream of the dam, the river flows
through a chain of lakes, including White Iron, Garden, Farm, and Fall lakes, and into
the lakes of the BWCAW (Figure 1). The chain of lakes is for all practical purposes
one lake connected by narrows, meaning that any contaminants released into Birch
2 Citations to the TMM documents herein refer to the MPO unless otherwise noted.
10

Lake would be transported into downstream lakes, including the BWCAW. Farther
downstream from these BWCAW lakes lie Ontario’s Quetico Provincial Park and
Minnesota’s Voyageurs National Park.
Figure 1. Map showing the location of the proposed TMM mining Project area and the chain of
connected lakes (orange) through which contaminants would flow into the Boundary Waters Canoe
Area Wilderness. The specifications of the proposed Project allow for a 22% chance for a catastrophic
discharge of untreated, contaminated mine water and sediment within the 25 year operation of the
mine.
Northeastern Minnesota has the most pristine surface- and groundwater in
the state. These waters are very low in dissolved nutrients, sulfate, salts, and metals
(Thingvold, 1979) and have low biologic productivity (oligotrophic), mostly due to
the thin soils and sparse anthropogenic (human-caused) impacts. Native species
have evolved to live under these oligotrophic conditions. The median conductivity in
surface waters of the area is 65 µS/cm, including the Kawishiwi River at 55 µS/cm
with median hardness of 27 mg/L as CaCO3 (App. 2, Thingvold, 1979; MPCA Surface
Water Data Access, 2020). The Kawishiwi watershed thus has a low capacity to dilute
11

and reduce the harm of introduced toxics, especially during surface water low flow
conditions, which are common in dry periods and during late summer and winter.
The very low ionic content of these waters means that relatively slight changes to the
water chemistry can be toxic to the species inhabiting these waters (Thingvold, 1979;
Minn. R. 7050.150 Subp. 3; 7050.0216 Subp.2; 7050.022 Subp. 4; Johnson, 2015;
Cormier, 2016). The very low natural sulfate concentrations (below 5 mg/L and
mainly below 1 mg/L; Myrbo et al., 2017a, Fig. 1) mean that “ecologically significant
changes may occur even when SO4 [sulfate] concentrations are elevated only
modestly” (Myrbo et al., 2017b).
C. Mine Plan of Operations (MPO)
The MPO identifies three areas of operations: (1) the underground mine; (2)
the plant site; and (3) the tailings management site. In the proposed mine, the ore
would be extracted in five production steps: drilling, blasting, excavating,
transporting, and crushing. Thus prepared, the ore is brought to the plant site surface
where the ore enters the concentrator process consisting of the comminution circuit,
the gravity concentration circuit, and the flotation circuit. The plant also is the site
for the concentrate dewatering and storage and where the reagent make-up area is
located. The tailings management site includes the dewatering plant (producing both
the engineered tailings backfill [ETB] for the underground mine and tailings filter
cakes for aboveground storage) and the filtered tailings storage facility (FTSF). The
FTSF would cover 429 acres of tailings stacked to an average height of 130 feet, well
above the height of the surrounding forest.
The MPO identifies processes for managing four categories of water (process
water, contact water, non-contact water and construction stormwater) and three
categories of rock (ore, development rock and waste rock). As will be explained in
the Scoping <strong>Comments</strong> section below, each of the above areas of operation, as well as
both the water and rock management processes, entails risks for releasing numerous
harmful chemicals and their degradation products, with potential synergistic
combinations, into the surrounding air and waters. Many of these chemicals can be
categorized as pollutants or toxics as defined under the federal Clean Water Act,
Section 502 [33 U.S.C. 1362] (6), (13), (19) and State Statutes and Rules (Minn. Stat.
Sec. 115.01, Minn. Rules Ch. 7050.01217 Subp 1).
D. Scoping Environmental Assessment Worksheet Data Submittal
(SEAWDS)
TMM’s SEAWDS, in following the format prescribed by the Minnesota
12

Environmental Quality Board, identifies and discusses twelve resources: (1) Land
Use; (2) Geology, Soils, and Topography/Land Forms; (3) Water Resources (surface
water, groundwater and wetlands); (4) Contamination/Hazardous
Materials/Wastes; (5) Terrestrial and Aquatic Resources; (6) Historic Properties and
Cultural Resources; (7) Visual; (8) Air; (9) Noise; (10) Transportation; (11)
Cumulative Potential Effects; and (12) Other Potential Environmental Effects. TMM
calls for future scoping on only six of those resources -- 1-3, 5, 6 and 8.
E. Scoping Standards under State and Federal Law
Under both federal and state law, the scope of the EIS must ensure that the
significant issues are analyzed in depth. The intent of a federal EIS is to fully identify
the range of low to high potential impacts, rate them in terms of their risk (probability
of occurrence and severity of the consequences), identify potential mitigations, and
identify impacts that cannot be avoided. In preparing an EIS, agencies must use “all
practicable means and measures” to, among other objectives, “[a]ssure for all
Americans safe, healthful, productive, and aesthetically and culturally pleasing
surroundings“ and “[a]ttain the widest range of beneficial uses of the environment
without degradation, risk to health or safety, or other undesirable . . . consequences”
(National Environmental Policy Act [NEPA], Title I, Section 101).
Federal EIS scoping is controlled by 40 C.F.R. 1501.7. The regulation explains
that as part of the scoping process, the lead agency (here, the BLM) shall determine
the scope and significant issues to be analyzed in depth in the EIS. The scope "consists
of the range of actions, alternatives, and impacts to be considered in an EIS." 40 C.F.R.
1508.25. To determine the scope of EISs, agencies must consider: (a) three actions
("connected actions," "cumulative actions," and "similar actions”); (b) three
alternatives ("no action," "other reasonable courses of actions," and "mitigation
measures”); and (c) three impacts ("direct," "indirect," and "cumulative"). Id.
Under both NEPA and the Minnesota Environmental Policy Act (MEPA),
impact evaluations are required to use the best scientific data available as determined
by experts technically qualified to make such determinations. According to 40 CFR
1500.1 (b), “[t]he information must be high quality. Accurate scientific analysis,
expert agency comments, and public scrutiny are essential to implementing NEPA.”
Moreover, under Minn. Stat. Sec. 116D.03, Subd. 2, state agencies are to “utilize a
systematic, interdisciplinary approach that will insure the integrated use of the
natural and social sciences and the environmental arts in planning and in decision
making which may have an impact on the environment.”
The state scoping process is set out in Minn. Stat. § 116D.04, subd. 2(h), which
13

provides that “[a]n early and open process must be used to limit the scope of the
environmental impact statement to a discussion of those impacts that, because of the
nature or location of the project, have the potential for significant environmental
effects.” The statute also requires that: (1) “[t]he same process must be used to
determine the form, content, and level of detail of the statement as well as the
alternatives that are appropriate for consideration in the statement . . . “; (2) “the
permits that will be required for the proposed action must be identified during the
scoping process”; and (3) “the process must identify those permits for which
information will be developed concurrently with the environmental impact
statement.” Id. The statute concludes that “[t]he determinations reached in the
process must be incorporated into the order requiring the preparation of an
environmental impact statement.” Id.
Under state rules, although the scope is intended to “reduce the scope and bulk
of the EIS,” it is also intended to identify “potentially significant issues” and “define
the form, level of detail, content, alternative, time table for preparation, and preparers
of the EIS . . .” Minn. R. 4410.2100, subp.1. As DNR has stated: “[t]he purpose of
scoping is to identify the potentially significant environmental and socioeconomic
issues requiring detailed analysis, alternatives to be evaluated, and potential
mitigation options. Scoping helps the agency focus the environmental review on the
most important issues, but also helps define alternatives and additional data needs.”
DNR Twin Metals website.
Here, because a scoping EAW is mandated, DNR will also be required to
prepare a proposed draft scoping decision document “to facilitate the delineation of
issues and analyses to be contained in the EIS.” Minn. R. 4410.2100, subp.2
The comments provided below are intended to help both the BLM and DNR
prepare an adequate scope for this project, including the proposed scoping decision
document.
Given the threat that the TMM plan poses to the state’s waters, a note on the
laws protecting those waters is in order. The objective of the Federal Clean Water Act
is to: (a) “restore and maintain the chemical, physical, and biological integrity of the
Nation's waters” (Clean Water Act Sec 101(a)). Minnesota Rules also protect aquatic
communities: “[f]or all class 2 waters, the aquatic habitat, which includes the waters
of the state and stream bed, shall not be degraded in any material manner, there shall
be no material increase in undesirable slime growths or aquatic plants, including
algae, nor shall there be any significant increase in harmful pesticide or other residues
in the waters, sediments, and aquatic flora and fauna; the normal aquatic biota and
the use thereof shall not be seriously impaired or endangered, the species
composition shall not be altered materially, and the propagation or migration of
14

aquatic biota normally present shall not be prevented or hindered by the discharge
of any sewage, industrial waste, or other wastes to the waters” (Minn. R. 7050.0150
Subp. 3). Class 2 waters surround the TMM site. Listed numeric standards and
criteria protect class 2 waters “for the propagation and maintenance of aquatic biota,
the consumption of fish and edible aquatic life by humans, the use of surface waters
for public and private domestic consumption where applicable, and the consumption
of aquatic organisms by wildlife” (Minn. R. 7050.0217 Subp. 1, et al.). Minnesota’s
Class 4 agriculture and wildlife use classification protects wild rice (Zizania palustris),
an ecologically and culturally important aquatic plant species, with a maximum
standard of 10 mg/L sulfate – “applicable to water used for production of wild rice
during periods when the rice may be susceptible to damage by high sulfate levels”
(Minn. R. 7050.0224, subp. 2).
TMM’s Environmental Review Support Documents, notwithstanding their
length and breadth, fail to identity, much less to examine, a number of impacts on and
threats to northeastern Minnesota’s environmental resources. In addition, the
submittal provides very little data or analysis for any resource. It is unusual for such
documents to be as vague and limited as those presented by TMM: such documents
typically present a wide range of options for consideration that are subsequently
evaluated and reduced during preparation of the environmental impact statement
(EIS). In lieu of providing the actual data needed at this stage in the environmental
review process, TMM has instead outlined generalized plans for future work to
generate these data.
IV.
Scoping <strong>Comments</strong>
A. Geology of the Project Area
1. Chemical and Mineralogical Composition of Rock Types
The TMM documents lack data pertaining to geology-related topics, in spite of
extensive existing work on this topic and some two million feet of core from the
Maturi deposit (TMM MPO cover letter, no page number). For example, the SEAWDS
contains no data regarding the chemical and mineralogical composition of the rock
types that TMM expects to encounter in the project area. Although TMM cites Miller
et al. (2002), a reference that contains some of these data, TMM has not included any
of these data (lines 2458-2464).
Similarly, TMM has identified only several types of troctolite and their
15

espective general mineralogies. There is no mention of the ultramafic (i.e., olivinerich)
rock types (e.g., norite), nor is there information about the nature of
inclusions/xenoliths of other rock types that are known to be present in the SKI and
in the basal mineralized zone (BMZ). Note that the BMZ occurs in the lowermost (i.e.,
westernmost) portion of the SKI (Severson, 1991; Patelke and Severson, 2005). The
maps and cross-sections submitted by TMM include only a few general rock types in
this portion of the Duluth Complex. For example, in the submitted figures, TMM has
lumped several types of troctolite together and has mapped the BMZ as one unit (see,
in contrast, Figure 2.). Examination of drill cores by Severson (1994) and others has
shown that the unit mapped by TMM as the BMZ actually contains at least four
different rock types, including a basal heterogeneous unit (picrite to peridotite),
norite, and at least two varieties of troctolite, plus inclusions of banded iron formation
(Figure 2).
Figure 2. Generalized geology of the South Kawishiwi Intrusion (SKI) showing typically high
heterogeneity and complexity of mineralization and lithologies within the distance of only 20 miles.
The ore is in the “basal mineralized zone” (BMZ), which lies about 4000-4500 feet (three-quarters of a
mile) below the surface, and consists of the areas denoted BH, BAN, UW, and U3 in this figure. The
proposed TMM Project would take place in the areas denoted “Maturi” in this figure and may approach
the “State Highway 1 corridor” area. TMM also holds mineral leases in other areas, including those
denoted “Birch Lake” and “Spruce Road” here. From Miller et al., 2002, after Severson, 1994.
Another topic that is not mentioned in TMM’s submittals is the degree of
alteration of some rock types. For example, the primary minerals of the ultramafic
rocks are often highly altered to serpentine, chlorite or other minerals (Miller et al.,
2002). Since some minerals of the serpentine subgroup, such as cummingtonite, can
be asbestiform, it is important for TMM to provide information about their
occurrence in the Project area. This heterogeneity in mineralogy and lithology must
be reflected in TMM’s scoping plans.
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The main ore minerals are listed in the Project Geology section, but only their overall
abundance (1-6%) is provided. TMM does not explain what is meant by percent
abundance of sulfides. Presumably, this sulfide abundance refers to the disseminated
mineralization. If this is true, this percentage of sulfides refers to percent by volume,
which is an initial visual determination made by geologists during drill core logging.
The Plan’s text mentions that there are some areas that have “sulfide contents outside
of that range” (line 1985), but no data are provided to explain or constrain the range
in sulfide content. By not including the full range in sulfide content, TMM is omitting
important information about the “borderline chaotic” (Patelke and Severson, 2005)
nature of the mineralized zone. Available information in numerous publications (e.g.,
Severson, 1994) indicates that massive sulfide mineralization (rocks with more than
50% sulfides) are present in the SKI and are thus to be expected in the TMM Project
area.
This lack of data regarding the specific mineralogy and abundance of sulfide
minerals hinders environmental review of this project. The fact that higher
concentrations of sulfides are present in some portions of the Project area is
important for several reasons. In particular, some areas with higher sulfide
concentrations, due to a high pyrrhotite (iron sulfide) content, may be classified as
either ore or waste rock, depending upon the content of copper or nickel sulfides and
other target compounds. Under either classification, these materials could produce
tailings or waste rock with higher sulfide content, which, under certain conditions,
could lead to metal leaching and/or acid mine drainage (AMD), and to higher than
anticipated sulfate concentrations in mine water.
The Regulatory Agencies must require TMM to take the following
necessary actions:
a. Provide detailed data regarding the mineralogical and chemical
composition of rock types that are likely to be encountered in the Project area.
b. Because the BMZ is the main economic target for the proposed mine,
provide more information about the complexity of the geology in the BMZ,
including the occurrence, distribution, and mineralogical and chemical
composition of inclusions or xenoliths. Detailed maps and cross-sections of the
Project area must be presented.
2. Geological Structure within the Project Area
In its SEAWDS, TMM states that “[t]he Maturi deposit has not been
significantly deformed, but it has been subjected to minor displacements along
reactivated basement faults, as well as cross-faults. Mapped structures are mostly
17

sub-vertical north-northeasterly striking faults” (SEAWDS lines 2515-2517). But the
SEAWDS does not define “minor displacements,” nor does it characterize the density
of minor faults and fractures in the Project area and their relationship to groundwater
flow. Severson (1994) notes a displacement of the Duluth Complex of approximately
200-300 feet along the Birch Lake fault, which lies just south of the Project area.
Severson (1994) also mentions other fault displacements greater than 100 feet in the
Duluth Complex that are present in or near the Project area.
Faults in the context of the proposed mine are important for a number of
reasons. Without detailed knowledge of faults and fractures, there is no means of
predicting surface subsidence due to underground mining. According to the MPO,
neither subsidence nor heaving would exceed 2/3 inch; however, the only
explanation given for this prediction is “three-dimensional numerical simulations”
and a reference to the non-available document “Wood, 2019. Crown Pillar and
Subsidence Analysis – Maturi Deposit. June 11, 2019.” Moreover, without a detailed
study of faults, there is no basis for assessing the potential for local seismicity.
Therefore, there is no basis for a determination of the seismic acceleration that the
FTSF would need to be able to withstand (line 942).
TMM also uses the term “(m)apped structures” (line 2002). Most references
to faults in the literature are based on information that comes from bedrock outcrops,
drill cores, or geophysical evidence. The latter source of information is often indirect,
and although it may be fairly definitive, it may not be considered as “mapped”
evidence of a fault. Thus, in this context, TMM needs to define and specify what they
mean by “mapped structures.”
Faults and fractures (in association with related alteration zones) are also
conduits for the movement of groundwater and other fluids. Several published
articles (e.g., Miller et al., 2002) have concluded that some of the copper, nickel and
precious metal deposits in the Duluth Complex are present due to the leaching of
metals by late-stage magmatic or hydrothermal fluids that migrated along faults and
re-deposited the metals in and near fault and fracture zones. Chloride-rich fluids are
documented in the Duluth Complex; under certain conditions (e.g., high acidity), these
fluids could leach and transport metals and could therefore have an adverse impact
on groundwater and surface water. Dahlberg and Saini-Eidukat (1991) documented
the presence of chloride-rich rocks and fluids in the Minnamax (now Teck) and Dunka
Pit sulfide deposits. The Teck and Dunka Pit deposits are located several miles
southwest of the Project area. These authors analyzed rock samples that contained
up to 3200 parts per million (ppm) chloride in micro-fractures and groundwater
samples that contained up to 11,000 ppm chloride. The samples were collected from
moderately to highly altered (serpentinized) zones that are associated with fault and
fracture zones. Dahlberg and Saini-Eidukat (1991) indicated that their findings
18

agreed with previous studies linking the segregation of PGEs to the movement of
chloride-rich solutions along fault and fracture zones. Pasteris et al. (1995) provided
additional evidence that PGEs were concentrated in some deposits due to the action
of chloride-rich fluids in fractured and altered zones. Thus, there is evidence that
fractures and faults played an important role in the localization of sulfide deposits,
and especially PGEs in certain areas in the Duluth Complex.
Potential leakage/leachate from several different proposed TMM facilities
(especially the 400-plus acre FTSF) could enter fractured bedrock or fault zones and
adversely impact groundwater and surface water. Chloride-rich groundwater that
enters the mine (“mine inflow,” lines 254-276) would be pumped to the surface and
could be mixed with process water, exacerbating the salinity and salt precipitation
problems identified elsewhere in this document as well as causing risk if accidentally
released.
The Regulatory Agencies must require TMM to take the following
necessary actions:
a. Provide data regarding the presence and location of fault, fracture,
and alteration (e.g., serpentinization) zones in the Project area. These data must
be presented in the form of detailed maps of the Project area, and must include
inferred locations based on geophysical evidence.
b. Explain the basis for the prediction that subsidence and heaving due
to underground mining would not exceed ±2/3 inch (±16 mm). In particular,
TMM must provide the document by Wood (2019) that makes this prediction. If
Wood (2019) is not based upon a detailed knowledge of faults and fractures, the
study must be repeated to reflect that knowledge.
c. Identify, quantify, and provide detailed location maps for all altered
(e.g., serpentinized) mafic and ultramafic rock types that contain chlorides
and/or fluorides, which may be removed from the mine as ore, waste rock or
development rock.
d. Detail plans for analysis of chloride content of mine water and
interactions with anticipated lithologies and mineralogies of the mined rock.
3. Economic Geology and Analysis
The SEAWDS states “[t]he Project would be an underground mine and
concentrator for copper, nickel, cobalt, platinum, palladium, gold and silver ore from
the Maturi deposit of the Duluth Complex” (lines 191-193). This specific list of metals
and their proposed extraction from only the Maturi deposit does not mention other
19

metals, such as titanium and vanadium, that are also present (as oxides) in association
with other sulfide deposits of the Duluth Complex. For example, the Nokomis and
Spruce Road deposits, which are adjacent to the Maturi deposit, may contain
economic concentrations of titanium and vanadium (Severson, 1994; Severson and
Hauck, 2003; Patelke and Severson, 2005). Although it is not clear from Figure 2-1 in
TMM’s MPO, it appears that TMM has mineral interests in the Nokomis deposit. The
DNR’s state non-ferrous metallic mineral leasing web map shows that TMM holds a
state lease for 160 acres in that area. Thus, TMM may already have future plans for
mining at the Nokomis deposit and therefore may additionally be interested in
titanium, vanadium, and other metals.
According to the SEAWDS, the mine would annually process approximately 7.3
million tons of ore in order to yield 174,000 tons of copper concentrate, 84,000 tons
of nickel concentrate, and 550 tons of gravity concentrate (lines 217-222). In other
words, these yields would be about 3.5% of the ore (which itself is a small fraction,
along with waste rock and development rock, of the total amount of rock that the
mining operation would handle). The gravity concentrate would contain precious
metals (platinum, palladium and gold) with much higher values (gold brings
$1700/oz., while copper is at 12¢/oz), but it would constitute only 0.2% of the total
yield. And even these projected weights are that of concentrates, not of the metals
themselves. Rather, they include sulfide, water, and (presumably) remaining nonmetal-sulfide
rock fragments. Nowhere in its submissions has TMM projected
the amounts of actual metals that its mine will produce. Because of the much higher
values for the precious metals, the proposed mine may rely heavily on the actual
grades (sometimes expressed in ounces-per-ton [oz/ton]) and recoveries of
platinum, palladium and gold for its economic success and viability. Data from the
U.S. Bureau of Mines showed that gold and platinum grades for the Spruce Road
deposit are each approximately 0.02 to 0.04 oz/ton. These grades are approximately
equivalent to 200-300 parts per billion (Patelke and Severson, 2005). Given these
low grades and high values of precious metals, as well as the documented variability
of the geology and sulfide mineralization of the BMZ (Patelke and Severson, 2005), an
independent economic evaluation of the proposed mine is needed during the
environmental review process to understand the mine’s viability.
The Regulatory Agencies must require an independent economic
evaluation of the proposed mine. Since TMM has multiple mineral leases with the
State of Minnesota in the Project area, the state has an economic interest
(through royalties based on net smelter return) in the economic viability of the
mine. The evaluation must analyze the present and future economic viability of
the proposed mine, and it must consider variables such as achievable ore grades,
metal recoveries, and current and future metal values. TMM must provide full
20

and complete information (such as assays of drill cores) to the consultant who
carries out the economic evaluation. The consultant must: (1) have no financial
conflict of interest; (2) have done no other work for Twin Metals (past, present or
future); (3) have no ownership interest in Twin Metals or any of its affiliates; and
(4) have no relatives who work for Twin Metals. In addition, this economic
evaluation must constitute only a small fraction of the consultant’s business.
4. Rock Management and Material Characterization
“Development rock” is defined by TMM as “sulfide barren rock mined from the
hanging wall that would be used for construction aggregate” (lines 1077-1081). This
definition is problematic because the transitions between sulfide-bearing and sulfidebarren
rock may not be distinct, or may occur over short distances (Figure 2). The
available literature indicates that in some rock types adjacent to the BMZ these
changes may in fact be gradational. Therefore, development rock may contain
sulfides. In such cases, the proposed use of development rock for construction
aggregate may not be environmentally appropriate. In addition, there has been no
explanation as to what would be done with rock from the hanging wall that is not
sulfide barren or whether some or any of the sulfide-rich rock from the hanging wall
can be left in place.
“Waste rock” is defined as “rock mined during operations below the targeted
cutoff grade” (lines 1082-1084). In the SEAWDS, TMM does not specify the cutoff
grade and does not provide a sampling and analysis plan that would be necessary for
TMM to differentiate and classify material as “waste rock” vs. “development rock” vs.
“ore.” Similarly, TMM states that “[d]uring the construction phase, as the mine
declines and ventilation raises approach the BMZ, mined rock would be monitored
and tested to determine the cutoff point where sulfide mineralization begins. When
sulfide mineralization begins, this would represent the ’end’ of the development rock”
(SEAWDS lines 263-266). Again, TMM does not provide a definition of the cutoff point
and does not provide a sampling and analysis plan to identify that cutoff point. It
should be noted that TMM’s MPO mentions a cutoff grade of 0.4% copper, but only in
the context of “mine stopes are generally designed around a proposed cut-off grade
of 0.4% copper” (lines 166-167). In the context of rock management and material
characterization, TMM must provide much more clarity and specificity about the
“cutoff grade” and the “cutoff point” and how those two concepts are related.
The description of the material characterization program (SEAWDS lines 256-
262) and the descriptions in the sections cited therein consistently refer to plans for
future work and suggest that little work has been done to date on the material
characterization program. For example, Section 5.1.3 includes the statement “TMM
21

has developed a Project-specific material characterization program in consultation
with MDNR . . . [which] is ongoing and can be divided into three components”
(SEAWDS lines 2612-2615). The three components, however, are general and nonspecific
plans that do not refer to actual sampling plans or data (SEAWDS lines 2615-
2621).
The minimal data provided by TMM in this context are not detailed enough to
be useful to reviewers or permitting agencies. For instance, SEAWDS lines 2623-2627
include the statements “[w]ith respect to development rock and ore, less than 10% of
the samples tested to date are preliminarily classified as having an ARD potential”
and “[u]nlike many other ore types, elevated sulfur contents in the Maturi deposit
occur almost exclusively in association with the ore with the remainder of the
samples being classified as waste rock.” Such statements do not indicate the number
and type of samples, the type of analyses performed, or the cutoff points used, and do
not provide or reference any actual analytical data.
At lines SEAWDS 2630-2633, TMM again points to non-specific future plans
for material characterization by stating that “[p]lanned future testing . . . includes
continued static testing to inform necessary kinetic testing and additional
mineralogical analysis.” Similarly, at lines SEAWDS 2758-2760, TMM states: “[t]he
development and implementation of the materials characterization program is an
ongoing effort by TMM which will culminate in documentation which captures the
following information . . .” The three bullets that follow mention “framework,”
“description” and “work plan.” These bullets again suggest that very little work has
been completed on the materials characterization program. If actual work has been
conducted and data have been generated, TMM has not included that information in
its data submittal.
Lastly, SEAWDS Section 5.3 notes that “[t]he current focus of the material
characterization program is to continue static testing to further inform where kinetic
testing is necessary. Results from future static, kinetic, and field testing will further
inform material management and engineering controls, as necessary. In addition to
informing material management and engineering controls, data from the material
characterization program will be used as an input to water quality modeling”
(SEAWDS lines 2773-2778). No static testing data (such as sulfur content) have been
provided (other than that cited above from Section 5.1.3 at SEAWDS lines 2623-
2627), and no kinetic testing data (e.g., humidity cell testing) have been provided. In
effect, all TMM has presented is a plan to have a plan, making it impossible to evaluate
the sufficiency of the material management and engineering controls proposed.
The Regulatory Agencies must require TMM to take the following
necessary actions:
22

a. Submit data regarding the full range of sulfide deposits, including
detailed information about their nature and distribution as well as quantitative
data regarding mineralogy and chemistry. In addition, TMM must provide data
regarding ore grades, ore cutoff grades and sulfide cutoff points that would be
expected in the proposed mine, and how these relate to different categories of
rock that would be managed in different ways, including “ore,” “development
rock” and “waste rock.”
b. Submit any available data regarding static or kinetic testing for the
material characterization program that have already been collected by TMM or
by other parties in the Project area or in adjacent areas in the Duluth Complex,
and to submit any other data that have already been collected for the material
characterization program.
c. Prepare and submit a sampling and analysis plan (SAP) for the
material characterization program. The SAP must include a description of the
sampling and analytical methods that have been or would be used in the
program, and include a list of the number of samples and sample types that would
be or have been collected and analyzed.
5. The Likelihood of Acid Mine Drainage
Most, if not all, non-ferrous mining projects throughout the world have
produced acid mine drainage (AMD; Kuipers et al., 2006). (TMM refers to AMD as
“acid rock drainage” (ARD), which is non-standard in the industry: “ARD” ordinarily
denotes acidity caused by natural processes, rather than human-induced effects.)
TMM cites studies (e.g., Wenz, 2016) as support that the TMM project would not lead
to AMD (SEAWDS lines 2581-2610). However, TMM concedes that 10% of the rock
that has been tested is “preliminarily classified as having an ARD potential” (SEAWDS
lines 2623-2625). Neither the relevant test results nor the basis for this classification
are provided.
Kinetic studies are often used to predict AMD and other leachates, but their
uncertainties can result in failure of the models to correctly predict AMD generation.
The heterogeneity of the deposits that cause such uncertainties in the TMM Project
area mean that AMD testing must be mine-specific.
The buffering capacity of the Duluth Complex is an important factor in
estimating the potential for AMD. Kinetic studies (e.g., humidity cell research) are
often used to predict buffering capacity, subsequent AMD, and the release of other
leachates. Gaps in, and misuse of, these studies have resulted in failure to predict
AMD generation (Kuipers et al., 2006). Lack of detailed minerology, as well as many
23

other factors, cause huge uncertainties in the prediction of AMD. As stated above,
kinetic studies must be mine-specific and use detailed mineral types and volumes.
Such studies may not be based on general data.
TMM alludes to DNR’s kinetic testing (lines 3488-3499). DNR has performed
long-term kinetic testing to attempt to develop a possible methodology to predict the
potential for AMD from the Duluth Complex. The most detailed testing was from a
single bulk, composited sample of Duluth Complex waste rock acquired during the
AMAX test mine operation in the late 1970s, from which field test pile leachates have
been collected for years. The DNR’s source of Duluth Complex rock was from an
undefined location in the sulfide-bearing rocks from the AMAX mine. Test piles were
initially designed as an attempt to determine AMAX waste rock leachate quality.
Later, the test piles were used to determine whether leachate quality could be
predicted using humidity cell testing.
To carry out humidity cell testing, DNR identified the minerals and size
fractions of the rock in the field test piles. Humidity cell testing results obtained from
the field test plots were then compared with leachate results from the same field test
piles. The DNR results are not applicable to any specific mine. These tests and others
demonstrate only that Duluth Complex waste rock can produce both AMD and
circumneutral leachates that exceed water quality standards (Eger and Lapakko,
1980; Morin, 2000; Scharer, 2000; DNR, 2004; Lapakko, 2015; Wenz, 2016). DNR’s
methodology may be helpful in conducting humidity cell tests for other Duluth
Complex specific mine predictions. But the DNR tests cited by TMM do not, and
cannot, support the prediction that TMM’s waste would not produce AMD.
The DNR has also conducted limited testing of Duluth Complex tailings. The
two tests samples were from AMAX and Teck-Cominco Inc. bulk samples, both from
the Partridge River Intrusion (Lapakko, 2003, 2013). The tests studied a limited
number of regulated parameters, and the results demonstrated that no AMD was
produced. But the report further stated: (1) “[t]he concentrations observed are not
expected to simulate those under field conditions, and additional analysis of the data,
in conjunction with consideration of fundamental geochemical principles, will be
required for extrapolation”; (2) “[i]f the tailings do not generate acid, trace metal
release will be the major environmental concern”; and (3) “[n]ickel and other heavy
metal concentrations increased substantially over relatively small pH changes.” As
with the waste rock testing discussed above, no up-scaling of laboratory results has
been performed.
The literature (e.g., Maest et al., 2005) identifies best practices for sampling
and analysis inputs to predictive water quality modeling, including: adequate
geochemical characterization; an adequate sampling and analysis plan; accurate
24

mineral identification, quantification, and mapping; adequate test sample size in
proportion to mineral volumes quantified; appropriate methods of kinetic testing
performed; sufficient test duration; adequate particle size determination; treatment
of samples separately rather than composited; appropriate statistical analyses of the
results; and accurate extrapolation of lab test results to field conditions (USEPA,
1994; Lapakko, 1998; Maest et al., 2005; Kuipers et al., 2006; Lapakko, 2015). These
parameters must be part of a transparent program by TMM to evaluate the likelihood
of AMD. In addition, the findings of Kuipers et al. (2006), that Environmental Impact
Statements (EISs) usually greatly underestimate water quality degradation from
mining, must be used to determine margins of error for these calculations that can be
used in risk determinations.
The MPO provides a limited assessment of the acid neutralizing capacity of
silicate minerals in the area of the mine, a key to the TMM argument that AMD would
not occur. It states that silicate minerals “are sufficient to maintain approximately
non-acidic conditions for extended periods (i.e., decades) for rock with low total
sulfur content” (lines 3502-3504); however, on the time scale of past and future
human habitation of northeastern Minnesota, “decades” of protection are woefully
insufficient. Further, the MPO states, “[f]or higher total sulfur content rock, silicate
minerals have the ability to neutralize the generation of acidity (i.e., neutralization
potential) and delay the development of ARD, thereby allowing time for
implementation of appropriate engineering controls” (lines 3504-3508). TMM
appears to concede that AMD would occur (but would be “delay[ed],” though
evidently by a shorter time than by “decades”). No plan is provided for
“implementation of appropriate engineering controls” to handle this AMD. The TMM
document does not provide numerical values for “low” and “higher” sulfur content
rock, nor how abundant these categories are anticipated to be in the ore, waste rock,
and tailings.
The Regulatory Agencies must require TMM to take the following
necessary actions:
a. Make its sampling and analysis plan as well as its predictive water
quality modeling inputs, calculations, and results, available for review. Inputs
include the missing rock and mineral characterizations identified elsewhere in
this report, particle sizes used in kinetic testing, and QA/QC protocols.
b. Use multiple methods to measure and calculate AMD potential,
following published standards (e.g., Maest et al. 2005). TMM must also conduct
sensitivity analyses, and express margins of error on calculations.
c. Provide a timeline of when they anticipate that AMD would begin,
the monitoring plan necessary to detect AMD, and the actions that they would
25

take in response to the appearance of AMD, including a plan for implementation
of appropriate engineering controls.
d. Provide a timeline of when they anticipate that AMD would end and
the monitoring plan necessary to detect the end of AMD.
e. Produce kinetic testing results that include not only AMD-related
substances but also all substances that are numerically regulated in Minnesota
Rules Ch. 7050.0220 Subp. 5a, and toxic pollutants regulated in Minnesota Rules
Ch. 7050.0217.
B. Mine Water
1. Water Balance
The MPO describes a plan for zero discharge of mine water into the
environment. Zero discharge is equivalent to equating the input rate of water into
the Project area to the consumption rate of water on the Project area plus or minus
the rate of change of storage of water within the Project area. TMM apparently has
sufficient confidence in the ability to achieve zero discharge that the proposed mining
operation does not include any facilities for water treatment (Figure 3). The inputs
of water include the flow of groundwater into the underground mine, precipitation
and surface runoff onto the Project site, and the withdrawal of water from Birch Lake.
The consumption of water includes evaporation, the water stored in the filtered
tailings, and the water exported with the metal concentrates.
The MPO estimates the groundwater entry rate as 53,000 gallons per hour
(line 1285). Based on a 14.5% water content (average of the range of 13-16% stated
in SEAWDS lines 886-887) and production of 96 million metric tons of tailings over
25 years (SEAWDS lines 934-936), the rate of storage of water in the filtered tailings
facility can be calculated as 16,800 gallons per hour. The MPO provides no estimates
of the input of water due to precipitation or surface runoff, the output due to
evaporation, nor the water that would be entrained within the exported metal
concentrates. The estimate of the groundwater entry rate includes no uncertainties
and no explanation. Presumably, it has been estimated from measurements of
hydraulic conductivity in monitoring wells, although those hydraulic conductivities
vary over nine orders of magnitude (see SEAWDS, Fig. 6-12). Moreover, there have
been no measurements of hydraulic conductivity deeper than 2300 feet below the
surface (see SEAWDS, Fig. 6-12), even though mining could potentially extend to 4500
feet below the surface. Since the groundwater entry rate is so poorly known, it is
equally unknown how the redirection of groundwater toward the proposed
26

underground mine would affect surface stream flows.
Any shortfalls of water for the mining operation can be met by simply
withdrawing more water from Birch Lake. The threat to the environment, however,
is that the input of water due to groundwater flow, precipitation, and surface runoff
(which are not under the control of the mining company) will exceed the consumption
of water and the capacity of the Project site to store excess water (Figure 3). The
proposed ponds for storage of excess contact water (water that could potentially
come in contact with ore, tailings, or waste rock) will be large enough to contain the
water from a 24-hour storm with a 100-year return period or the runoff from a 100-
year snowpack (lines 2900-2903). In a similar way, the ponds for storage of excess
process water (water that is used to process the ore) will be large enough to contain
the water from a 24-hour storm with a 100-year return period. In other words, in any
given year, there is a 1% probability that the ponds will overflow, resulting in an
uncontrolled release of untreated mine water into the environment (because there
will be no water treatment facility). Moreover, although pond sizes were stated and
shown on drawings, the sizes were not justified in terms of the volumes of water that
would be expected from the design storms and snowpacks.
A 1% annual probability is equivalent to a 22.2% probability of an
uncontrolled release of untreated mine water during at least one year of the 25-year
mining operation. An annual probability of 1% for an environmental catastrophe is
not generally regarded as acceptable by our society. By analogy, FEMA classifies
dams into three hazard potentials, depending upon the consequences of failure of the
dam. According to FEMA (2013), “[d]ams assigned the low hazard potential
classification are those dams for which failure or misoperation results in no probable
loss of human life and low economic and/or environmental losses. Losses are
principally limited to the dam owner’s property. . . Dams assigned the significant
hazard potential classification are those dams for which failure or misoperation
results in no probable loss of human life but can cause economic loss, environmental
damage, disruption of lifeline facilities, or can impact other concerns.” FEMA (2013)
then states that dams with low hazard potential may be designed to withstand the
100-year flood (1% annual probability of exceedance), while dams with significant
hazard potential must be designed to withstand the 1000-year flood (0.1% annual
probability of exceedance). Based upon the above analogy, it would be appropriate
to design the water storage infrastructure so as to accommodate a 24-hour storm
with a 1000-year return period or the 1000-year snowpack.
It should be noted that the objective of zero discharge can be met only when
the mine is in operation. After the final or temporary closure of the mine,
precipitation and surface runoff onto the Project site, as well as the flow of
groundwater into the proposed underground mine, would continue, while the
27

consumption of water by the mining operation would cease. At that point, the release
of mine water into the environment would be inevitable. According to MPO
Appendices, “[i]f test work and analyses show water treatment or other water
management methods are required, then water treatment systems and management
methods would be evaluated and designed as part of future studies” (lines 944-946).
Temporary or final closure could occur simply due to a drop in copper prices.
At the present time projected copper prices are sufficiently high that TMM is pursuing
the opening of a new mine in northeastern Minnesota. Nevertheless, TMM has
presumably decided that the construction of a water treatment facility would be
uneconomical. It seems TMM is claiming that, if a drop in copper prices should force
the closure of the mine, they would have sufficient economic resources to develop a
water treatment facility that would be needed immediately upon cessation of the
mining operation. The economics of this decision process requires further
consideration. This is especially important since Barr Engineering, PolyMet’s
consultant, previously acknowledged that post-closure water treatment at the
proposed PolyMet (NorthMet) mine could last for centuries. Specifically, they wrote:
“Mechanical water treatment is part of the modeled NorthMet Project Proposed
Action for the duration of the simulations – these are 200 years at the Mine Site and
500 years at the Plant Site . . . Water quality modeling performed in support of this
FEIS indicates that water treatment systems would be needed indefinitely at the Mine
Site and Plant Site” (Polymet FEIS, 2015).
Additional sources of potential output water are the seepage from the filtered
tailings storage facility and the precipitation that infiltrates and flows through the
tailings (called the draindown). The MPO mentions these phenomena, but does not
include any estimates of their magnitudes.
The Regulatory Agencies must require TMM to take the following
necessary actions:
a. Provide estimates with uncertainties for all components of the
water balance, including groundwater inflow, precipitation, surface runoff,
evaporation, storage of water in filtered tailings, and export of water in the metal
concentrates. Estimates and uncertainties of meteorological variables must take
projected climate change into account and must be specific to the Project site, not
simply to the nearest weather station. Groundwater flow needs to be estimated
using multiple methods, including measurements of hydraulic conductivity from
monitoring wells and baseflow into streams. Measurements of hydraulic
conductivity must include measurements taken from monitoring wells that are
at least as deep as the maximum depth of the proposed underground mine.
b. Estimate with appropriate uncertainties the reduction in stream
28

flows that would result from mine dewatering.
c. Design all water storage infrastructure to accommodate a 24-hour
storm with a 1000-year return period or a 1000-year snowpack.
d. Design and construct appropriate spillways for all water storage
ponds so that their overflow does not simply result in an uncontrolled release of
water into the environment.
e. Provide a plan for construction and operation of the water
treatment facility that would be needed before temporary or final closure of the
mining operation, and an economic analysis demonstrating their ability to
construct a water treatment facility in advance of temporary closure of the mine.
f. Provide a plan for long-term monitoring of the mine water that
would be released from the water treatment facility or other components of the
mining operation following temporary or final mine closure. The plan must
include planned actions in response to the results of monitoring.
g. Provide estimates (with explanations and uncertainties) of the
rates of seepage and draindown from the FTSF.
2. The Use of 100% Recycled Mine Water
Pursuant to the MPO, all process water would be recycled. The organic and
inorganic chemical composition, toxicity, and mass loading of the 100% recycling of
mine water have not been identified. Lacking such data makes human health and
environmental impact assessment for the site impossible to perform adequately.
The endless recycling of the process water with no water treatment facility
(and with the addition of chloride-rich mine inflow water pumped to the surface) will
result in the inevitable saturation of the process water with soluble salts from
groundwater, the crushed ore, and the reagents. This saturation will cause salts to
precipitate on all surfaces that come into contact with the process water. The
implication of this generalized precipitation of salts has not been considered
anywhere in the MPO. In particular, it has not been considered as to whether the
process water will still function for extraction of the metal concentrates after it has
become saturated with salts. To the best of our knowledge, the only other mining
operations that carry out zero discharge and zero water treatment have enormous
reservoirs (essentially lakes) for storage of the process water, so that the water is
continuously diluted by precipitation and surface runoff.
The Regulatory Agencies must require TMM to take the following
necessary actions:
29

a. Identify the chemical and toxicological content of the 100% recycled
mine water and the range of concentrations and compositions expected. All
characterizations must demonstrate that the samples tested are statistically
representative of the wastewater. The above requirements need to apply to the
process water, the contact water, and the non-contact water.
b. Explain how the process water will continue to function for ore
beneficiation once it has become saturated with salts.
c. Explain how they will address the precipitation of salts from the
saturated process water.
d. Provide other successful examples of mining operations that carry
out zero discharge and zero water treatment under similar environmental
conditions, both with and without large reservoirs for the storage of the process
water.
e. Drill into the closed INCO test drift and perform pump tests to aid in the
determination of possible infiltration rates over a larger expanse than drill holes
alone.
C. Filtered Tailings Storage Facility (FTSF)
Although the MPO uses the expression “dry stack facility,” the expression
“filtered tailings storage facility” (Figure 3) is preferred in these Scoping <strong>Comments</strong>
because the tailings would not be literally “dry,” but would have a target water
content of 13-16%. The expression “dry stack facility” is generally not favored within
the mining industry. For example, according to a publication by engineers from the
mining consulting firm Knight-Pièsold, “[g]eotechnical engineers associate the
optimum moisture content with moisture levels just below full saturation after
compaction, thus terming such a facility as a dry stack is a misnomer. The present
authors would encourage practitioners to abandon the use of the term dry stacking
in favor of the more straightforward term, ‘filtered tailings.’ It is not desirable to
unintentionally mislead the public at large with an industry term that is noticeably
misused” (Ulrich and Coffin 2017).
1. Chemicals Added to the Surface of the FTSF
Once tailings are disposed into the FTSF, additional chemicals would be
applied to attempt to keep the surface of the tailings from generating dust. These
chemicals, along with any reaction products, would be part of environmental leachate
releases to storage ponds, and potentially to unsaturated soils, groundwater, and
30

surface water in the event of liner leaks, overflows as a result of insufficient design
and capacity and unanticipated closures, accidents, and other oversights. The
proposed chemicals could also impair revegetation efforts required during
operations and for closure.
The Regulatory Agencies must require TMM to study the potential
environmental impacts of the chemicals proposed to be added to the surface of
the FTSF. All characterizations must demonstrate that the samples tested are
statistically representative of the chemicals at concentrations applied.
2. Liners for the FTSF, Mine Water Storage Ponds and Crushed
Rock Locations
The FTSF, mine water storage ponds, and crushed rock locations are proposed
to be underlain with synthetic membranes to prevent leaching of contaminated
liquids. The MPO assumes there would be no leaks in perpetuity; however, all liners
leak. In the past, MPCA has allowed public sewage stabilization ponds in small towns
to leak up to 500 gallons per acre per day. Yet these ponds are only a few acres in
size. Here, the tailings management site alone is 653 acres (SEAWDS, table 3.2). If
MPCA permitted a 500 gallon per acre per day rate, the maximum allowable seepage
from the tailings management site would be 326,500 gallons per day (13,600 gallons
per hour, which is nearly equal to the rate at which water would be exported to the
FTSF [16,800 gallons per hour; see section IV.B.1. above]).
The Regulatory Agencies must require TMM to take the following
necessary actions:
a. Provide manufacturer warranties and test data regarding liner
defects, leaks and age. TMM must furthermore estimate the potential cumulative
volume of liner leakage, as well as its potential environmental impacts. The
above estimates will require estimates of seepage and draindown from the FTSF,
as mentioned previously.
b. Provide a thorough description of how holding pond sediments will
be removed without damaging the liners.
3. Soils to Cover the FTSF
The MPO states that the proposed FTSF would be “covered and reclaimed”
with “suitable growth medium, which includes topsoil, peat and mineral soil” (line
976-77). The growth medium would be “underlain by a hydraulic barrier” (line 956).
Yet the MPO fails to identify the location(s) and volumes of soils to be permanently
31

etained for revegetation of the tailings basin. Moreover, the MPO fails to identify any
studies of, or instances where, native plants were able to grow in such soils, underlain
by a hydraulic barrier, in an environment like northeastern Minnesota. Although the
MPO estimates that “502,000 yd 3 (384,000 m 3 ) of organic soil (topsoil and peat) and
878,000 yd 3 (671,000 m 3 ) of mineral soil would be stripped and stockpiled” (lines
984-986), the MPO does not include any geotechnical characterization of the soil or
consideration of the stability of the stockpile.
The Regulatory Agencies must require TMM to take the following
necessary actions:
a. Fully identify the location(s) of the future soil cover, including
artificial soils, and prove them to be legally held so that they will be accessible at
any time for revegetation.
b. Study the identified natural soils/artificial soils and nutrient
content in order to demonstrate the ability of such soils to support vegetative
growth needed to successfully cover the tailings management site and anchor the
topsoil to the tailings during operations or at closure.
c. Demonstrate that species proposed for revegetation would survive
in the tailing chemistry and minerology, since roots will penetrate into the
tailings, and that drainage with respect to the hydraulic barrier would be
appropriate for these species.
d. Carry out geotechnical characterization of the organic soil and
mineral soil and demonstrate that the stockpiles would be stable with an
appropriate factor of safety.
4. Target Water Content for Filtered Tailings
According to the SEAWDS, “the tailings filter cake produced by the filter plant
would be a dry (13 to 16% moisture) silty, sandy material” (lines 886-887). However,
according to a publication by mining engineers from SRK Consulting (available on the
SRK Consulting web site), “[c]ommonly, projects are specifying (or promising) a
target filter-cake moisture at the limit of the filter performance (including at the limit
of the thickener’s ability to deliver feed at the required solids ratio). This has caused
numerous examples where the operating performance does not consistently meet the
target . . . Essentially, irrespective of site, ore body type, or filter press manufacturer,
a 15% moisture content remains a typical target, while tracking of day-in and day-out
moisture contents of filter cakes demonstrates that achievable moisture contents are
often in the range of 17 to 18% when things are running smoothly and can be up to
20 to 23% when off-spec . . . . ‘Targets’ may be cited or promised, but achievable filter
32

cake moisture contents and the variability of the process are not generally within the
tailings engineer’s control” (Crystal et al., 2018). The discrepancy between the
promise in the SEAWDS and the state-of-the-art as described by SRK Consulting is
disturbing because, also according to the SRK Consulting web site, “[b]eginning in
2015, SRK has been providing environmental consulting and permitting expertise to
Twin Metals, a subsidiary of Antofagasta plc, for the development of an underground
copper, nickel, platinum, palladium, gold and silver mine in northern Minnesota”
(SRK Consulting, 2020).
Ore body heterogeneity (as discussed above in section IV.A.1.) is a major
factor in the current difficulty in meeting target water contents for filtered tailings.
The study from SRK Consulting continues, “[n]or do engineers and operators have
significant control over the variability of the ore which may be the controlling factor
in achieving consistently economical filter-pressing . . . Often the designer is provided
with limited and potentially unrepresentative samples of tailings in the early stages
of a project, and it is therefore important that consideration be given to the mine plan
and ore body geological information in considering the likelihood for variation in ore
properties . . . Depending upon the efficiency of the filters, the variability of the ore,
other operational constraints and poor operational control there is a very reasonable
risk that low-density, high-moisture content filtered tailings will be placed within the
dry stack. Figure 6 illustrates that at the range of typical target and achievable
moisture contents, it is more likely than not that the tailings will behave as a saturated
material unless arid conditions prevail and/or other moisture conditioning measures
are not taken during placement” (Crystal et al., 2018).
The Regulatory Agencies must require TMM to demonstrate that it would
be able to consistently produce filtered tailings with 13-16% water content, given
current technology and the still-unknown heterogeneity of the ore body.
5. Temporary Storage of Uncompacted Tailings
Because of the current inability to consistently produce filtered tailings with
the proper water content for compaction, the current solution is to set aside an inner
core (a region away from the outer slopes) for placement of tailings that cannot be
compacted. The study by SRK Consulting explains, “[t]he tailings engineer can,
however, specify acceptable moisture contents for different areas of the dry stack,
depending on stacking strategies. For example, external structural zones may have
more stringent criteria than non-structural zones, for which reduced constraints may
be allowed” (Crystal et al., 2018). The MPO calls for the same strategy: “[t]he lined
dry stack facility would consist of a zone of densely compacted tailings filter cake
around the full perimeter of the facility which would provide increased structural
33

stability. . . Tailings filter cake in the interior of the lined dry stack facility (nonstructural
zone) would be moderately compacted” (lines 929-933).
The production of filtered tailings in a wet environment increases the
technical challenges involved in construction of a FTSF because the tailings can be
rewetted by precipitation (Figure 3) even if they leave the filter presses with the
target water content. The MPO acknowledges that “in order to achieve geotechnical
requirements, dry stack facility construction would not proceed during extremely
wet periods (heavy rain or snowmelt) or during extremely cold periods [defined as
below 5˚ F] as the tailings must be compacted prior to freezing” (lines 958-960 and
SEAWDS line 955). Construction of the filtered tailings facility would also be
interrupted in response to increasing pore pressure within the stored tailings.
According to the MPO, “[i]f monitoring shows an unacceptable rise in pore pressure,
then pore pressure would be allowed to dissipate before placement of additional
material on the dry stack facility” (lines 968-970). However, the MPO includes no
discussion as to how frequently these wet or cold periods could be expected to occur,
or whether there is enough space to temporarily store uncompacted tailings during
wet or cold periods or during periods of elevated pore pressure.
The MPO states, “[t]he radial stacker would be used to create a stockpile with
up to 1.5 days of tailings storage capacity as a tailings filter cake . . . The stockpile
would be enclosed in the heated building to prevent dust, rewetting due to
stormwater, and freezing due to cold temperatures” (lines 888-891). It could require
more than 1.5 days to address elevated pore pressure within the FTSF, and it is
certainly possible to have more than 1.5 days of wet or cold weather: indeed, Babbitt,
MN, near the proposed mining site, has an average of 65 days per year with a
nighttime low temperature below 0˚F (Sperling’s Best Places 2020), i.e., even colder
than the 5˚F specified. The SEAWDS (lines 953-954) does state that “therefore during
the winter, tailings would primarily be deposited underground as engineered tailings
backfill.” However, there is no discussion as to how long “winter” lasts, no assurance
that there would be enough space to store all or most of tailings underground during
the “winter,” and no contingency plan for what to do with the tailings if there is
insufficient underground storage space.
The Regulatory Agencies must require TMM to take the following
necessary actions:
a. Estimate the frequency and duration of periods during which it
would be either too wet or too cold to compact the tailings for permanent storage
in the FTSF.
b. Demonstrate that the proposed Project site would include sufficient
space for temporary storage of uncompacted tailings without release of water to
34

the environment.
c. Establish a weather station to record basic weather information
including the number of days a year that temperatures dip below 5 degrees F at
the plant site and the FTSF.
Figure 3. Generalized diagram of a filtered tailings storage facility (FTSF). TMM claims that “a dry stack
facility does not require a dam." On the contrary, filtered tailings facilities do require an outer shell of
compacted tailings (called the structural zone; see lower left of figure), which serves the same function
as a dam. The distinction is not merely semantic, as the refusal by TMM to use the word "dam" implies
a refusal to comply with dam safety regulations and to consider the consequences of dam failure. Note
also that TMM proposes no water treatment (see top center of figure), so storage ponds will contain
untreated, contaminated mine water. Those ponds are designed with a 22% chance of overflowing
within the 25-year lifetime of the Project, and discharging untreated, contaminated mine water and
sediment into Birch Lake, which flows into the BWCAW. Adapted from Klohn Crippen Berger, 2017.
6. Lack of Adherence to Dam Safety Requirements
A shocking aspect of the MPO is the statement that “a dry stack facility does
not require a dam” (Page xv). This concept is presented even more starkly in the
document “Twin Metals Dry Stack Tailings Storage 101” as “Tailings stored in dry
stacks are piles of sand topped by native soil and vegetation. There is no need for a
dam to hold them in place, no possibility of dam failure, and no long-term storage
issues.” However, it is clarified in a mining industry study that the structural zone of
a filtered tailings storage facility is a dam (Figure 3). According to Klohn Crippen
Berger (2017), “[i]f filtered tailings are placed in a stand-alone facility (pile/stack),
the outer slopes must maintain structural stability (similar to a dam or a waste
dump), particularly under seismic loading conditions . . . [Filtered tailings storage
facilities] still require ‘structural zones’ for containment, which act like dams, made
of compacted tailings.”
35

The MPO defines “dam” as “a structure that impounds water” (Page xv), which
would seem to preclude structures that confine filtered tailings, which are supposed
to contain pore water, but not free water. However, the MPO definition is nonstandard
in the mining industry. For example, the Australian National Committee on
Large Dams (2012), defines “tailings dam” as “a structure or embankment that is built
to retain tailings and/or manage water associated with the storage of tailings, and
includes the content of the structure.” Thus, the structure that confines tailings is
called a “tailings dam” even if no free water is present. It is perhaps most important
that the Minnesota Rules define a dam as “any artificial barrier, together with
appurtenant works, which does or may impound water and/or waste materials
containing water” (Minn. R. 6115.0320). Filtered tailings with a projected water
content of 14.5% would certainly count as “waste materials containing water.”
The discussion as to whether the “structural zone” of the proposed FTSF for
the Twin Metals mine is or is not a “dam” is not simply a matter of semantics. There
is a large body of guidelines, regulations and laws regarding dam safety. The
implication of the refusal of TMM to use the word “dam” seems to be that they are
claiming exemption from dam safety guidelines and legislation and the requirement
of addressing the most basic questions that would be asked of any proposed dam.
Most importantly, these questions would include:
1) What is the design flood or precipitation event for the dam (maximum flood
or precipitation event that the dam must be able to withstand)?
2) What is the design earthquake for the dam (maximum seismic acceleration
that the dam must be able to withstand)?
3) What is the factor of safety and annual probability of failure of the dam?
4) What would be the consequences of failure of the dam?
With regard to the last question regarding the consequences of failure, it
should be noted that the structural zone can fail by slumping even if no liquefaction
or flow behavior occurs. The distance traveled by slumping material can be ten times
the height of the filtered tailings (Klohn Crippen Berger, 2017), or 1300 feet in the
case of the FTSF at the Twin Metals mine. Thus, even a slump could carry the tailings
into or nearly into Birch Lake and thus potentially into the Boundary Waters
Wilderness.
Whether or not the word “dam” is used, the MPO does not include any
discussion of the geotechnical properties of either the filtered tailings or the
foundation. Without any geotechnical characterization, there is no basis for analyzing
the stability of the FTSF. The SEAWDS both denies and acknowledges the lack of
geotechnical characterization within a single paragraph by writing “[t]wo-
36

dimensional stability analysis was conducted using a typical cross-section of the dry
stack facility structure and foundation design” (lines 978-979) followed by “[i]f any
weak, compressible, or loose soils would be identified [in] the foundation of the dry
stack facility, these undesirable soils would be excavated” (lines 988-990). In other
words, stability analysis was carried out using geotechnical parameters of the
foundation, even though the geotechnical parameters of the foundation are unknown.
Moreover, the MPO does not include any analysis of local seismicity or any
consideration of the seismic acceleration that the FTSF must be able to withstand.
The Regulatory Agencies must require TMM to take the following
necessary actions:
a. Demonstrate that the structural zone of the proposed FTSF will
fulfill all applicable state and federal guidelines, regulations and laws for dam
safety, including the appropriate design flood, design earthquake, annual
probability of failure, and factors of safety.
b. Fully analyze the consequences of failure of the structural zone. The
failure analysis must include both the worst-case scenario and the most-likely
scenario that would occur following failure of the structural zone. For
clarification, the worst-case scenario must include the release of 100% of the
stored tailings following failure of the structural zone.
c. Carry out complete geotechnical characterization of both the
filtered tailings and the foundation as a preliminary to all stability calculations.
Since dredged pond sediments would be added to the FTSF, there must also be a
complete geotechnical characterization of the mix of filtered tailings and dredged
sediments.
d. Carry out an analysis of local seismicity and to use the analysis to
specify the design seismic acceleration (or design earthquake) for the FTSF. As
mentioned above, the design seismic acceleration must be consistent with all
state and federal guidelines, regulations and laws for dam safety.
7. Infrastructure to Prevent Rewetting of Stored Filtered Tailings
Any FTSF requires appropriate infrastructure to prevent rewetting of the
stored tailings. The design of appropriate water management infrastructure is
especially important in areas of high rain- and snowfall (Figure 3). Moreover, the
increase in the height of the tailings stack could cause further compaction of the
underlying tailings. This compaction could cause the pores to become saturated with
water (which increases the likelihood of failure by liquefaction) even without any
increase in the water content of the filtered tailings.
37

The MPO calls for the construction of diversion dikes around the perimeter of
the FTSF with sufficient capacity to convey the stormwater from a 24-hour storm with
a 100-year return period (MPO Appendices, lines 67-68). However, there was no
explanation as to why 100 years was the appropriate return period. The important
consideration is the height of the water table within the FTSF at which the factor of
safety would be insufficient to guarantee stability. Whether that critical water table
height would occur would then depend upon the water added from overflow of the
diversion dikes, the draindown from precipitation onto the filtered tailings, and the
progressive compaction of the tailings. Since there has been no geotechnical
characterization of the tailings, no estimates of draindown, and no consideration of
the impact of water table height on stability, there is no basis for designing the
diversion dikes to accommodate a 100-year flood. Along the same lines, although
there is a plan to underlie the FTSF with overdrains (above the liner) and underdrains
(below the liner), there has been no consideration of the storm return period that the
overdrains and underdrains must be able to accommodate.
The Regulatory Agencies must require TMM to design the diversion dikes,
overdrains, and underdrains to ensure that the FTSF can withstand the
appropriate design flood in accordance with applicable state and federal
guidelines, regulations and laws regarding dam safety. At a minimum, this
design requires geotechnical characterization of the tailings, estimates of the
factor of safety as a function of water table height, draindown from precipitation
through the tailings, and the possibility of progressive compaction of the tailings.
8. Incompatibility of Filtered Tailings and Zero Water
Discharge/Zero Water Treatment
It has already been mentioned that endless recycling of the process water with
no water treatment facility will result in the inevitable saturation of the process water
with all soluble salts from groundwater, the crushed ore, and the reagents. Just one
of the implications is that there will be a continuous precipitation of salts into the
pores of the filter presses. In order for the filter presses to function, there would need
to be a continuous washing of the filter presses to remove the precipitated salts.
There is no discussion of this technical challenge in the MPO and especially no
discussion of any source of the relatively fresh water that would be needed for
continuous washing of the filter presses. Obviously, the filter presses could not be
washed with any water that was already saturated or even close to saturation with
soluble salts. We are not aware of any other mining project that has combined or is
even proposing to combine filtered tailings technology with 100% recycling of mine
water with no water treatment.
38

The Regulatory Agencies must require TMM to take the following
necessary actions:
a. Demonstrate that filter presses can effectively operate even with
process water that is saturated with soluble salts.
b. Identify the source of water for washing filter presses and
demonstrate that sufficient, relatively fresh water would be available for this
purpose.
c. Provide other successful examples of the combination of filtered
tailings technology with zero water treatment/zero water discharge.
D. Production and Release of Chemicals
1. Analysis of Movement of Chemicals
At its core, an environmental risk assessment is the analysis of environmental
movement of chemicals through the environment and the toxic effects of those
chemicals on human and ecological health (Benjamin, 2001; Stratus, 2008). TMM
would have significant potential releases of chemicals through air, groundwater,
surface water, soils, and sediments. Yet the TMM scoping proposal lacks the
information necessary for scientific evaluation and risk assessment to identify
potential significant impacts. Both human health and ecological risk assessments
must be performed to reveal and document potential significant impacts to these
resources. These assessments must strictly follow EPA guidance.
The Regulatory Agencies must require TMM to present complete chemical
characterization data including, but not limited to, the following:
a. Total inorganic chemical analyses (i.e., whole rock geochemical
analyses) of all rock types to be removed;
b. Full organic and inorganic chemical characterization of dust
suppression chemicals proposed to be applied to the FTSF, including their
reaction products;
c. Chemical characterization of any cementitious materials to be used
for engineered tailings backfill or grouts;
d. Full organic and inorganic chemical analyses of all beneficiation
and thickening chemicals, including degradation products and bioassays to
determine levels of toxic effects;
e. Total inorganic and organic chemical analyses, grain size, and
39

volumes of all materials destined for the FTSF;
f. Calculation of quantity and composition of draindown from FTSF;
g. Mineralogical and chemical analyses of the very fine particles that
would be deposited with tailings, holding pond sediments (whose dredge spoils
may be deposited along with tailings) and from dust control. This must include
characterization of silicates, sulfur-bearing phases, and asbestiform particles;
h. Detailed hydrogeological analysis of the unsaturated and saturated
zones under the tailings management site, water storage ponds, diversion
ditches, and rock storage areas to determine flow paths of potential liner
leakages.
i. All characterizations must demonstrate that the samples tested are
statistically representative and meet or exceed all applicable USEPA quality
assurance/quality control guidance.
j. Prior to any pump tests being performed as described in section
IV.B.2.e above, a series of full chemical and toxicological analyses needs to be
made of the existing water from the closed INCO test drift to assist in the
determination of long-term leachate concentrations and toxicity to aid in the
prediction of the potential chemistry and toxicity of releases to both ground and
or surface waters from inundated mine workings.
2. Sulfate and Dangers to Aquatic Ecosystems and Wild Rice
The TMM project risks discharge of mining water contaminated with dissolved
sulfate into pristine, low-sulfate lakes, rivers, wetlands, and groundwater-surface
water systems. The dangers of sulfate contamination are unacknowledged in the
TMM documents, but sulfate contamination of aquatic ecosystems presents three
distinct and substantial dangers to environmental and human health (Figure 4): (1)
sulfate harms wild rice (Zizania palustris, a protected species) and other rooted
aquatic plants (Pastor et al., 2017; Myrbo et al., 2017a and references therein)
because sulfate is converted to toxic sulfide in the mud of the plant rooting zone; (2)
sulfate addition causes the soils of lakebeds, wetlands, and riverbeds to release
mercury, as well as nitrogen, phosphorus, and dissolved inorganic and organic
carbon, which individually and collectively can have significant and undesirable
effects on algae growth, water clarity, and pH (Gilmour et al., 2007; Myrbo et al
2017b); and (3) sulfate enhances the growth of existing microbes that make
methylmercury, the highly toxic form of mercury that accumulates in fish and other
life forms (Gilmour et al., 1992; Myrbo, 2017b). These harmful effects occur even if
AMD is neutralized. Dangers (1) and (2) “may severely influence the plant species
40

composition of freshwater wetlands” (Lamers et al., 1998), and thus could have
disastrous effects on the pristine ecosystems into which the Project drains. Danger
(2) could also lead to eutrophication (excess nutrient levels) and harmful algal
blooms in these ecosystems. Danger (3) could lead to more fish consumption
advisories for health threats from methylmercury.
Figure 4. Effects of sulfate pollution of northern Minnesota waters. Sulfate pollution would increase
eutrophication and mercury bioavailability (ability for mercury to get into food webs) in the lowsulfate
systems of northern Minnesota, and could wipe out entire populations of rooted aquatic plants.
(1) The sulfur in sulfate is changed to toxic sulfide in the mud, and can poison aquatic plants (including
wild rice) through their roots. (2) Sulfate pollution enhances the decomposition of organic matter in
mud, releasing the constituents that would have stayed buried. Phosphorus (P) and nitrogen (N) are
released into the overlying water, allowing more algae to grow, which decreases water transparency.
(3) Sulfate pollution not only releases mercury (Hg) from the mud, but it increases the production of
methylmercury, the only form that contaminates fish.
(1) Sulfate harms wild rice and other rooted aquatic plants: Wild rice (Zizania
palustris, manoomin in the Anishinaabe [Ojibwe, Chippewa] language, psiŋ in the
Dakota language) is an annual aquatic grass that grows in very low-sulfate waters in
the Laurentian Great Lakes area (northern MN, WI, and MI; southern Ontario and
Manitoba) – with the best and most widespread wild rice populations in Minnesota.
Wild rice has enormous cultural significance to some American Indian peoples;
degradation of wild rice waters in the project area probably violates the 1854 Treaty
of La Pointe guaranteeing usufructuary rights (e.g., Matson 2018; Fond du Lac Band,
2019). It is also the Minnesota state grain, and is a highly nutritious foodstuff whose
stands provide excellent habitat for waterfowl such as ducks. It has been clearly
demonstrated, both experimentally (Pastor et al 2017) and in a large field survey of
Minnesota waters (Myrbo et al 2017a), that wild rice populations are harmed by
sulfate pollution. Other studies summarized by Myrbo and colleagues (2017a) show
41

the same effects in other important rooted aquatic plants.
Sulfate contamination of low-sulfate surface water, including lakes, wetlands,
rivers, and groundwater connected to surface water, provides sustenance to
populations of sulfate-reducing bacteria (SRB) living in anaerobic (oxygen-free)
sediment pore water. These bacteria “breathe” sulfate (as other organisms use
oxygen) and decompose abundant organic matter in the sediment to produce
dissolved sulfide and a number of other compounds (see [2] below). This process is
called “sulfate reduction” because sulfate, an oxidized form of sulfur, is reduced
(opposite of oxidized) to sulfide. Sulfide is toxic to multicellular organisms. The
waters of northeastern Minnesota are naturally extremely low in sulfate (25% of
Minnesota lakes are below 0.3 mg/L sulfate; MPCA 2017), so even small inputs of
sulfate (especially over the course of years or decades) can have dramatic effects on
the amount of toxic sulfide in the lakebed sediments, where the roots of wild rice and
other aquatic plants take up water and nutrients. As noted earlier, a Minnesota water
quality standard limits the discharge of sulfate to wild rice waters to less than 10
mg/L; analyses of field data (MPCA 2017) show that, for about half of lakes in
Minnesota, even 10 mg/L would produce too much sulfide for wild rice to survive.
Although Birch Lake is the only wild rice water identified in the MPO, other sensitive
lakes and wetlands with wild rice populations are present in and downstream of the
Project area and could be contaminated with sulfate by the TMM Project.
(2) Sulfate causes wetland, lake, and river beds to release nitrogen,
phosphorus, and mercury (Figure 4): When sulfate-reducing bacteria (SRB)
decompose organic matter in the sediment as part of the sulfate reduction reaction
(as described in [1] above), the chemical compounds that comprise the organic
matter are released into the water of the lake or wetland. These chemicals include (i)
nitrogen and phosphorus compounds, which are primary nutrients for plants,
including algae; (ii) inorganic mercury, which can be converted to methylmercury
(see [3] below) and accumulate in the food chain; and (iii) dissolved organic and
inorganic carbon compounds, which can affect the clarity and the pH of the water
(Myrbo et al 2017b). (The inorganic mercury present in all lakebed sediments is
primarily from atmospheric deposition in dust and rainfall.) Sulfate release could
thus lead to more algae in pristine lakes and wetlands; higher mercury levels in the
fish in those lakes; and greener and browner, less transparent water.
(3) Sulfate stimulates microbes that make methylmercury, the highly toxic
form of mercury that accumulates in fish and other life forms. The inorganic mercury
released by the processes described in (2) does not accumulate in fish, and must be
methylated by microbes, including SRB, in order to be taken up into the food chain.
When sulfate contamination stimulates SRB growth, it can increase not only sulfide
production (as described in [1]) and organic matter decomposition (as described in
42

[2]) by these microbes, but the abundance of methylmercury as well. At high levels of
sulfide, mercury methylation is actually suppressed (Gilmour et al 1998; Myrbo et al
2017), which results in a “Goldilocks zone” of highest mercury methylation at
moderate sulfide concentrations (Johnson et al 2016). Because most area waters are
naturally low in sulfate, they are on the rising limb of the Goldilocks curve where
added sulfate would stimulate production of methylmercury. The combined effects of
(2) and (3) could dramatically increase mercury in fish, otters, eagles, and other fisheating
wildlife, and of course the human consumers of fish from impacted waters as
well. Current Minnesota guidelines already advise that pregnant women, women
who could become pregnant, and children under age 15 limit consumption of
Minnesota-caught bass, catfish, lake trout, northern pike, and walleye to no more than
one serving per month due to mercury contamination (MDH 2020); increasing sulfate
discharge could worsen the mercury content in fish, including in the BWCAW where
families often fish for their dinners.
Sulfate is derived from the dissolution and oxidation of minerals that include
the ores that TMM proposed to mine. Many points in TMM’s process would lead to
sulfate contamination of contact and process water, which, if released, would lead to
contamination of surface water and groundwater. The MPO states that 70-94% of
target metals would be removed in processing and transported off site. Some portion
of the sulfide associated with the removed target metals, as well as the 6-30% of the
minerals remaining in the tailings and waste rock, would dissolve into the process
and waste water, be stored in the FTSF (which is not dry but contains a minimum of
13-16% sulfate-rich mine water), or be returned to the mine as backfill.
Sulfate salts are highly soluble, and the removal of dissolved sulfate from
mining water is challenging and expensive, requiring reverse osmosis and/or
multiple chemical treatments (and that creates the problem of disposal of the solid or
liquid products removed, e.g., sulfate brines, precipitated minerals). However, the
TMM documents clarify that there would be no water treatment facility at the
proposed Project site. The only plan for removing sulfate presented in the TMM
documents is to export 100% of the sulfur with the metal concentrates, which is not
realistic, given the additional exposures of sulfur to mine water noted here.
TMM plans that all of the water at the site would be captured, reused, and
stored in holding ponds on the surface. These waters would come into contact with
and dissolve sulfur-bearing materials and become highly enriched in sulfate,
especially as the water is cycled through the process multiple times. The TMM MPO
and SEAWDS, however, do not provide estimates for the sulfate concentrations of
these waters over time, nor do they explain what would happen to these waters at the
end of their use except to note that they would be used in backfill and that storage
ponds would be permanent, persisting after the project ends. Information on these
43

sulfate concentrations and the final dispensation of the mine water is critical in order
to evaluate the risk of storage and handling of these wastes in watersheds of pristine
natural areas and whether the engineering protections against release of these
waters are sufficient. As noted elsewhere, the ponds are designed with a 22.2%
possibility of overflow and catastrophic release of mine water in the 25 year duration
of mine operations.
Both tailings and sulfate-enriched process water are described as constituents
of the backfill, but the binder is described in Table 2-7 of the MPO only as “slag-cement
mix.” Characterization of the backfill in its final state in the mine is essential for
evaluation of the risk of sulfate contamination of groundwater and mine water being
pumped to the surface in mine dewatering. In addition, categories of rock in other
stages of processing would be present on the surface and subject to dissolution due
to rainfall, increasing potential sulfate runoff. Finally, lignin sulfate is described as a
material to be applied to “roads and other disturbed areas” (line 3084).
The Regulatory Agencies must require TMM to take the following
necessary actions:
a. Provide estimates for the sulfate concentrations of all Project site
waters over time.
b. Explain what would happen to these waters at the end of their use.
c. Disclose its proposed process for removing sulfate from mining
water and disposal method for the resulting products.
d. Provide characterization of the engineered tailings backfill final
product, including chemistry, mineralogy, porosity, and permeability; kinetic
tests could inform understanding of leachability of chemical compounds of
concern.
e. Identify and map all wild rice populations downstream of the
Project.
f. Address the potential effects of sulfate release from the Project on
all wild rice populations downstream of the Project.
g. Address the potential effects of sulfate release from the project on
methylmercury levels in waters downstream of the mine.
h. Address the potential effects of sulfate release from the project on
nutrient levels, pH, and water clarity in waters downstream of the mine.
44

3. Beneficiation Reagents
Nonferrous metal mining uses numerous beneficiation reagents to separate
the ore from the tailings and to thicken the tailings from the flotation process for
water reuse. Sodium xanthate is one of the proposed beneficiation reagents. This
chemical has been identified as toxic to aquatic life at low levels (Alto, 1977; Lind,
1978). Furthermore, it can decompose into carbon disulfide, a compound that the
Centers for Disease Control’s Agency for Toxic Substance and Disease Registry has
listed as toxic to the human nervous system (ATSDR, 1997). Sodium xanthate and its
degradation products would be present in the holding ponds and in the pore spaces
of the tailings that are to be disposed on the surface and underground in the mine.
The Regulatory Agencies must require TMM to study potential human
health and environmental risk assessments for all beneficiation reagents, both
on site and beyond the site borders.
4. Other Compounds
Minerals occurring along with ores can be toxic to humans and other species
at very low concentrations either alone or as mixtures; crushing these minerals to a
fine powder exposes them to prolonged weathering and dissolution. Such materials
include arsenic, mercury, manganese, and fluoride. Numerous other elements and
compounds regulated under MPCA rules will be in the tailings, including silicates,
chloride, sodium, ammonia, nitrates, nitrites, non-ionized ammonia, and bicarbonate.
Tailings will also affect the hardness and salinity of waters that come into contact with
them.
The Regulatory Agencies must require TMM to identify and evaluate the
presence and toxicity of all chemical compounds that will be released in the
course of the mining operations.
5. Asbestiform Minerals
In its SEAWDS, TMM states: "[t]he ore that would be processed contains nonasbestiform
mineral fibers. Non-asbestiform concentrations in ore for the Project
would be reviewed and characterized further from an air quality standpoint. The
potential impacts on human health would then be discussed further in the EIS with
input from the RGU" (SEAWDS lines 6279-6282). The Duluth Complex is known to
contain serpentine minerals that may be present in altered troctolitic and ultramafic
rock types (Dahlberg and Saini-Eidukat, 1991). These altered rocks are known to
occur in the basal Duluth Complex and specifically in the Maturi deposit (Severson,
45

1994). If the Maturi deposit is mined, as proposed by TMM, potential human health
concerns exist, as the serpentine minerals (e.g., cummingtonite), may be fibrous or
asbestiform. The potential presence of asbestiform minerals in serpentine-bearing
rock would affect many parameters, including the PPE that the miners wear, the
ventilation system filtration, the dust control measures, and the testing that must be
undertaken.
The Regulatory Agencies must require TMM to define the full magnitude
and extent of serpentine-bearing rock present in the Project area and verify with
appropriate analytical methods (e.g., polarized light microscopy) that it does not
contain asbestiform minerals.
E. Potential for Fish and Wildlife Impacts
Chemical constituent releases from sulfide mineral mines globally, both
historic and contemporary, have had and continue to have adverse effects on fish and
wildlife abundance and health (Alpers et al., 1992; Gray, 1998; Lin et al., 2007; Powell,
2017). Nevertheless, TMM insists that the Project will not lead to AMD and will have
negligible effects on the surrounding biota.
The MPO and associated documents do not address acute or chronic effects on
terrestrial and aquatic species from exposure to the potential toxics produced by the
Project. TMM states only that the nature and extent of any such effects are currently
unknown and will be evaluated in the future scopes (SEAWDS lines 5397–419 as to
terrestrial wildlife, 5462-76 as to aquatic resources).
1. Contaminants of Potential Concern
Mine operations, post-mine closure, and winter road de-icing will produce a
number of environmental contaminants of potential concern. These include the
metals copper, nickel, cobalt, palladium, platinum, gold, silver, vanadium, and
titanium mentioned in the SEAWDS as products or by-products. A number of other
contaminants, though not mentioned by TMM, are found to occur in the rock in the
area, such as arsenic, mercury, manganese, and fluoride. Mine water will contain
dissolved or suspended constituents similar to those found in the ore body itself. In
addition to the elements already listed, there may also be traces of aluminum,
antimony, beryllium, cadmium, chromium, selenium, and zinc (USGS, 1973). Toxicity
among these elements varies greatly, and effects often differ among terrestrial and
aquatic species. Several of these elements enter into the food web and can
accumulate in an individual, but they generally do not increase in concentration up
46

the food chain to higher trophic levels. Mine operations can also be expected to
directly or indirectly result in accidental or unintentional release of mine water with
chloride, sulfate, silicate, nitrate, nitrite, and ammonia. Such releases will have direct
negative effects on aquatic biota and will affect the bioavailability of metals (their
absorption and adsorption by organisms). Beneficent chemicals used during the
process of separating the metals of interest will include: methyl isobutyl carbinol,
carboxymethylcellulose, copper sulfate, sodium isopropyl xanthates, calcium oxide,
sulfuric acid, sodium sulfite, phosphates, silicates, carbonates, dextrin starch glue,
sodium diisobutyl dithiophosphinate, and triethylenetetramine (SEAWDS Table 7-2).
As mentioned previously, sodium xanthate has been identified as toxic to aquatic life
at low levels and breaks down to carbon disulfide, which is also toxic (Alto, 1977;
Lind, 1978). Road salt and dust suppression chemicals (e.g., lignonsulfonates) will
also be used on-site and contribute to potential environmental pollutants (Eastern
Research Group, 2016; Herb et al., 2017). The potential environmental toxicity of
these chemicals is not addressed in the SEAWDS.
2. Ecological Receptors among Fish and Wildlife
The SEAWDS has compiled lists of terrestrial and aquatic species considered
to have sensitive or protected federal or state status that could potentially be
impacted by the Project (SEAWDS Tables 8-7 and 8-8). But TMM has not surveyed
the Project site for these species. There are many more resident, transient, or
migratory species without protective status in the categories listed (SEAWDS lines
5342-52), as well as amphibians, that serve as food for these species or are simply
part of the species assemblages in the habitats associated with the Project that could
also be impacted. With respect to migratory animals, the Project lies squarely in the
path of the Mississippi Flyway, a north-south migratory route used twice every year
by millions of birds from over 300 species.
TMM plans future work to assess the nature and extent of identified
preliminary impacts (habitat loss, habitat fragmentation, displacement, mortality,
effects of noise and lights) to terrestrial species. However, they state that mobile
individuals will move out of the Project area to unimpacted areas and that
populations of the affected non-mobile species are not likely to be affected because
their habitat is abundant in the region (in other words, they are too abundant to be
worth caring about).
There is no mention of the potential exposure to or effects of the contaminants
associated with the mine on the terrestrial ecological receptors. In contrast, TMM
recognizes surface water quality could be impacted and affect aquatic resources,
“however the nature and extent of these water resources impacts are currently
47

unknown and will be evaluated in future scopes of work” but “no future scope of work
exclusive to aquatic resources is proposed” (SEAWDS lines 5612-13). Instead,
“potential impacts to aquatic resources will be assessed using results from the future
scope for water resources outlined in Section 6.3.” Only effects on aquatic resources
from changes identified in surface and groundwater hydrology are mentioned in this
section (SEAWDS lines 4508-21). TMM states that future supplemental scope
questions will address potential impacts to surface water quality, but there is no
mention of evaluating potential effects of degraded surface water quality on aquatic
species.
3. Potential Sources of Contaminants and Exposure
Figures 5 and 6 provide conceptual models of contaminant sources and how
the ecological receptors could be exposed to the contaminants of concern. Sources of
contaminants inside and outside of the Project perimeter are surface waters, soil, and
vegetation. Terrestrial wildlife are most likely to be exposed to Project-generated
contaminants through trophic pathways, whereas aquatic and semi-aquatic species
could be exposed through both ingestion and contact. Fugitive dust, despite controls,
could reach soils, vegetation, and surface water. The MPO and accompanying
documents include many references to dust sources and controls, and Table 11-2
(SEAWDS) provides estimates of fugitive particulates from the various processes.
Using these data, the amount of dust that the project could generate, what it may
contain, and the volume or mass expected on vegetation, surface water, and soils must
be estimated.
The complex interconnected system of ponds and ditches to collect, route, and
provision water for the facility by way of a recirculating system will contain untreated
mine water and contaminated sediments. The MPO describes using water from Birch
Lake and non-contact water ponds to make up for water volume losses; however,
there is no description of the quality of water required for recovery of the target
minerals or how that quality will be maintained. As mentioned previously in this
document, endless recycling of the process water will result in saturation of the water
from added chemicals and their deposition in pond sediments among other locations.
The absence of data on quality of pond water and sediment prevents evaluation of
exposure to ecological receptors. Finally, during operations, but especially after mine
operations have terminated, water and leached chemicals can be expected to leak into
the sub-surface soil from the FTSF and to infiltrate into the bedrock from the
underground mine. In both cases, leached chemicals could potentially enter surface
waters.
48

Figure 5. Conceptual model indicating possible routes of exposure of mine contaminants to terrestrial
receptors.
4. Ecotoxicity of Contaminants Associated with the Project
Acute toxicity generally results in high numbers of mortalities in a short period
of time. The most likely event that would result in high mortalities of aquatic species
would be overflow or failure of the ponds and ditches holding the recirculating
operations waters (untreated mine water) into the environment. (By design, the
annual probability of this event will be 1%. The probability will be 22.2% that this
event will occur during at least one year of the 25 years of the mine project.) The
proximity of the Project to Birch Lake and its location within a very wet area with
many streams and drainages discharging to Birch Lake increase the likelihood that a
catastrophic event would result in untreated mine water and sediment waste
contaminating surface streams, Birch Lake, and downstream waterbodies. Slumping
or other structural failure of the FTSF is another extreme event that could carry
tailings into Birch Lake. Birch Lake is relatively shallow with a maximum depth of 25
feet. The lake and surrounding streams generally have low conductivity, hardness,
alkalinity, turbidity, nutrients, TSS and TDS and neutral to slightly acidic pH –
conditions that generally make dissolved cations more bioavailable to aquatic fauna.
A wide diversity of fish are found in these waters and provide important recreational
fishing. An extreme release of Project waters would likely have an immediate lethal
effect on stream aquatic species and littoral lake species. Contaminants that do not
degrade or enter the trophic cycle will eventually fall to the bottom as sediment. Birch
Lake is dimictic, i.e., its surface and deep waters mix in spring and fall each year. This
process resuspends sediment, metals, and potentially other contaminants into the
49

water column (Sarmiento et al., 2008). Therefore, an extreme event can have adverse
consequences on lake biota for many years into the future, as is seen in lakes that have
received acute spills of mine waste such as the previously pristine Quesnel Lake in
British Columbia, the site of a massive copper-gold mine tailings dam failure in 2014
(e.g., Hamilton et al., 2020).
Figure 6. Conceptual model indicating possible routes of exposure of mine contaminants to aquatic
receptors.
In contrast to acute toxicity, chronic toxicity occurs slowly over time. It may
not result in mortality, but rather can decrease health of affected organisms. Such
effects on individuals may go unnoticed for many years only to be recognized when
populations begin to decline. The zero discharge plan for the mine promotes the idea
that recycling the water, with withdrawals from Birch Lake as necessary, will reduce
exposure of fish and wildlife to chemical contaminants. Nevertheless, the large
volume and area that Project surface ponds will occupy will be foci for chronic
exposure directly or indirectly for potentially all ecological receptors. Unless
extremely toxic, the ponds will be colonized by invertebrates, with fully or partially
aquatic life-stages, which in turn will serve as a food source for animals at higher
trophic levels. Birds and bats can be particularly vulnerable to foraging on
metamorphosed insects that have accumulated metals in ponds as larvae or nymphs
(Vories and Throgmorton, 2000; Custer et al., 2008). Small terrestrial mammals,
reptiles, and amphibians will all be able to access the ponds and ditches particularly
with a 1V:3H gradient providing shallow water at the margins. Contaminants these
organisms accumulate may be passed on to their offspring or predators, e.g., birds of
50

prey or predatory mammals.
Toxic effects of the suite of chemicals of potential concern from this Project are
variable and largely dependent on site- and matrix-specific conditions. Federal and
state water quality standards provide minimum criteria to broadly protect species.
Given the many threatened and endangered species in the region, however, a rigorous
US Fish and Wildlife Service consultation process is needed to determine whether
more stringent criteria are necessary to protect threatened and endangered species.
Minnesota does not have sediment quality standards; rather it provides sediment
quality targets that can be used as benchmarks for evaluating potential effects on
biota (Crane and Hennes, 2007). There are no standards or benchmarks for a number
of chemicals because they have not been sufficiently studied. Moreover,
considerations must be given to impacts on sensitive species, trophic effects over long
periods of exposure, and chemical fate and exposure under specific environmental
and geochemical conditions. Beyond application of standards and targets,
environmental biota can be protected from Project impacts over the long term only
through the development and adoption of; (1) an extensive and strategic chemical
and biological monitoring program; (2) an adaptive decision making program
(usually termed the “Observational Method” in mining) to make adjustments to
processes and operations management as necessary; and (3) contingency plans to be
carried out in response to adverse observations. More detail about necessary actions
regarding monitoring and contingency planning are given in Section H below.
The Regulatory Agencies must require TMM to take the following
necessary actions:
a. Address the potential environmental toxicity of each of the
chemicals identified in the MPO and SEAWDS and their degradation byproducts.
b. Assess all risks to all terrestrial and aquatic wildlife (including
aquatic invertebrates), plants, and habitat: not only sensitive or protected
species but all resident, transient, and migratory taxa. It must specifically
evaluate the effects on birds migrating along the Mississippi Flyway. This
assessment requires an exhaustive literature review including, but not limited to,
reports from the Regional Copper Nickel Study, U.S. Forest Service, U.S. Geological
Survey, Legislative Commission on Minnesota Resources (LCMR), MinnAmax
Mining, University of Minnesota, and MNDNR.
c. Provide independent (as described above) economic evaluations of
the impact of the proposed mine on ecosystem services and on fisheries.
d. Describe the predicted amount of dust that the project could
generate, what it may contain, and the volume or mass expected on vegetation,
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surface water, and soils.
e. Provide baseline sediment quality data for lakes, ponds, wetlands,
rivers, and streams in the watersheds that would be affected by the Project.
f. Provide data on the projected quality and chemistry of pond water
and sediment, and how both will compare with standards for deleterious effects
on biota.
g. Provide estimates of environmental impact and remediation costs
for a catastrophic release of untreated mine water to Birch Lake, the Kawishiwi
River, the BWCAW, Quetico Park, and Voyageurs National Park.
h. Explain how it will prevent animals from colonizing ponds or
ingesting materials in the Project area.
i. Provide a monitoring plan and decision making resources for all
stages of mine operations, including post-closure, and contingency plans that will
be carried out in the event of adverse observations.
F. Potential for Boreal Forest Impacts
The TMM plant site and the adjacent BWCAW are located within a boreal
forest. Found across the northern latitudes of Europe, Asia and North America, boreal
forests provide carbon storage and clean water. In addition, boreal forests are home
to large and varied wildlife populations and large areas of unlogged forest.
As described in detail by Frelich (2019), the impact of copper sulfide mining
by TMM on the surrounding boreal forest will be felt most directly on the plant site,
within the FTSF, and along all of the supporting transit and power corridors (“mining
facilities”). Within those mining facilities, trees will be cut down, habitat will be
destroyed, and various chemicals will be brought in for use in the mining process
(including mineral separation and dust control). In the course of TMM’s mining
operations, chemicals will also be released from the site’s underlying sulfide rock
formations as a result of exposing sulfide minerals to air and water.
Destruction of forest, plant life and habitat within and along the mining
facilities will interrupt historic migration patterns of the local wildlife. In addition,
the construction of the mining facilities will cause fragmentation of the forest, which
will result in an increased edge-to-interior ratio. That, in turn, will lead to increased
light and temperatures along the edges and into the forest. The increased edge space
will also promote the introduction of invasive plants and animals. Fragmentation
effects can be expected to last for decades after the mining operation ends.
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Some amounts of both the imported chemicals and the released chemicals will
migrate (via surface water, groundwater or air-borne dust) to the surrounding forest
areas. Given the close relationship between a boreal forest and its supporting water
system, any negative impact on the water will result in negative impacts in the
surrounding forest.
Streams, wetlands, and lakeshores produce a vast array of aquatic–terrestrial
interfaces. The boreal forest in northeastern Minnesota is best understood as a thin
membrane of soil and the organisms it supports lying on top of bedrock with water
flowing through a vast network of tree and plant roots. Changes to water flow (caused
by roads and culvert systems for the mining) and water chemistry (also caused by
mining) could upset the balance among the various vegetation types. Changes in
water table, in both directions, caused by disruption of waterflow, can lead to the loss
of swamp forests. These effects will be seen at varying distances from the TMM plant
site, depending on the flow structure of the watershed, and they could last for many
decades.
Extreme rainfall events, which are expected with increasing frequency owing
to the warming climate, could lead to large inputs of acid mine drainage moving into
swamp forests downstream from the plant site. That, in turn, would lead to
accelerated ecosystem aging (i.e., acidification of waters and rapid infilling of lakes
with Sphagnum moss mats) throughout the wetland forests. Similar, but more local,
effects could occur from windblown dust from the plant site.
The BWCAW has become a resource for studying ecosystem processes. As
such, it provides a baseline for understanding how adjacent areas are affected by
logging, mining, roads, and other human activities. The TMM project, by imperiling a
range of conditions within the BWCAW, threatens the utility of BWCAW for use as a
baseline against which to measure the effects of human activity across northeastern
Minnesota.
The Regulatory Agencies must require TMM to take the following necessary
actions:
a. Report on the impacts of its plant construction, operations, and closure
on adjacent and downstream forests.
b. Prepare a plan to prevent the impacts identified in its study of impacts
of its plant construction, operations, and closure on adjacent and
downstream forests.
53

G. Other Known Impacts Not Here Addressed
The vagueness and major omissions of TMM’s documents provide many areas
for comment and recommendation before they begin to be adequate to support
development of an EIS. In spite of the numerous topics included in these <strong>Comments</strong>,
additional topics remain that have not been fully addressed by the Experts.
TMM does not estimate the human health risks of its proposed operations,
including leaching of hazardous metals by chloride-rich fluids, potential release of
asbestiform minerals as part of rock and ore processing, and methylmercury
poisoning of people (especially children and women of childbearing age) who
consume fish from impacted lakes. Pearson et al. (2019) provide substantial guidance
on the multitude of potential health impacts from the proposed TMM Project.
As noted earlier, TMM does not address even future scoping of fully half of the
twelve Resources it identifies following the format prescribed by the Minnesota
Environmental Quality Board. TMM must address (4) Contamination / Hazardous
Materials / Wastes, (7) Visual, (9) Noise, (10) Transportation, (11) Cumulative
Potential Effects, and (12) Other Potential Environmental Effects in its future
documents.
TMM also ignores wetlands in its documents, lumping them with “terrestrial”
resources in its restoration plans. Because the soils of wetlands are sometimes or
always water-saturated, they are very different environments from the soils in which
terrestrial plants and trees grow, and should thus have very different restoration
strategies, including soil and vegetation characteristics.
The Regulatory Agencies must require TMM to take the following
necessary actions:
a. Study and explain the potential human health impacts of all
consequences of proposed mining operations
b. Address future scoping of six additional identified subject areas
c. Provide plans for restoration of wetlands in the Project area.
H. Monitoring and Continency Planning
TMM provides only minimal plans for physical, chemical, or biological
monitoring of resources in the proposed Project area, or for built structures such as
the FTSF; recommendations for monitoring targets and approaches are provided
throughout this document. TMM’s monitoring plan must be accompanied by a set of
preplanned actions that will be selected on the basis of the observations that result
54

from the monitoring plan. Monitoring must continue for a period of time that is long
relative to the expected impacts. In the case of the FTSF, monitoring must continue
until the FTSF has achieved a permanent non-credible failure state. A permanent
non-credible failure state means that the FTSF can withstand the Probable Maximum
Flood (PMF) and the Maximum Credible Earthquake (MCE) and can remain in this
state indefinitely with no further monitoring, inspection and maintenance (Morrill et
al., 2020). The PMF and the MCE are the largest flood and earthquake, respectively,
that are theoretically possible at a given location. In the case of AMD, if TMM
anticipates that AMD will end after 1000 years, then they must plan to monitor for
10,000 years. TMM must also specify the actions they will undertake in response to
the appearance of AMD.
All mining plans are based upon the Observational Method. According to the
Observational Method, although a mining project is planned from beginning to end,
not all actions can be specified in advance because the choice of actions will depend
upon particular intermediate outcomes. As the project proceeds, observations will
be made and, depending upon the results of those observations, choices will be made
from a set of preplanned actions. The only exceptions are adverse outcomes that will
occur with no warning (no time to make observations), for which all preventative
actions must carried out from the outset of the project. It is most important that all
of these possible actions in response to observations are planned in advance of
making the observations. The Observational Method is not simply a license to figure
things out later. According to Engineering Investigation and Review Panel (2015),
“the Observational Method is useless without a way to respond to the observations.”
As mentioned previously, the MPO and SEAWDS are largely devoid of any contingency
plans or even intentions to develop contingency plans.
The Regulatory Agencies must require TMM to take the following
necessary actions:
a. Present robust monitoring plans for all stages of proposed mine
operations, including after temporary or permanent closure
b. Present contingency plans that describe the actions that will be
taken in response to adverse monitoring observations
V. Conclusion
Underlying the Twin Metals Minnesota mining proposal are a multitude of
risky and potentially hazardous design flaws and management procedures. We
conclude that each stage of the proposal must be carefully evaluated for adherence to
55

the best engineering and technical procedures to ensure the health and safety of
people and the environment. However, before that evaluation can proceed there are
a large number of information gaps that must be addressed.
Among the unknowns of the current site location are: the mineralogical and
chemical composition of rock types that are likely to be found there; the presence and
location of fault, fracture, and alteration zones there; and the presence and location
of altered rock types that may contain chloride-rich fluids and asbestos-like minerals.
Among the unknowns from the planned mining operations are: the likelihood,
timing and extent of AMD; the extent of subsidence and heaving due to underground
mining; and the ability of the process water, with no treatment facility in site, to be
recycled indefinitely without becoming fully saturated with salts and other
contaminants.
Among the unknowns from the FTSF are: whether a dam-like structure needs
to be built around it; where the cover soil will come from and whether such soil will
support vegetation; whether TMM can produce filtered tailings with 13-16% water
content; and, if so, whether TMM can produce such tailings during all expected
weather conditions and at all expected temperatures.
Among the unknowns concerning threats to the surrounding forests and
waters are: whether the planned water storage facilities on site are sufficient to
handle what are expected to be increasingly large rain events in the next 25 years; the
toxicity of each of the chemicals that will be used in the process and their degradation
byproducts on local terrestrial and aquatic wildlife; the volume and chemical content
of water that will leak through the liners of the FTFS and the waterways on site (that
all liners leak is one of the few knowns in the whole plan); and the cost and details of
an environmental monitoring plan during construction, operation, closure, and postclosure
of the Project.
And finally, among the unknowns for the entire project is whether, given the
low grade of the ore (another of the few knowns) and the likelihood of weatherrelated
interruptions, operational mishaps, copper price fluctuations, and/or
negative environmental consequences, the Project is economically feasible.
Given the great breadth and enormous risks of all of the unknowns inherent in
the TMM proposal, the Regulatory Agencies should, at a minimum, rigorously follow
each and every one of the recommendations set forth in this document.
56

VI.
Experts who Contributed to this Report
Frederick K. Campbell has a B.A. in geology from Macalester College and an
M.S. in geology from the University of Minnesota-Duluth. Mr. Campbell was a
hydrologist at the Minnesota Pollution Control Agency for 29 years, working mainly
on Superfund sites with groundwater and/or surface water contamination. Mr.
Campbell was previously an economic geologist, working on mineral exploration
projects in northern Minnesota and northern Wisconsin. He worked on the Teck
copper-nickel deposit in the Duluth Complex, which was previously known as the
Minnamax/Babbitt deposit.
Steven H. Emerman has a B.S. in mathematics from The Ohio State University,
M.A. in geophysics from Princeton University, and Ph.D. in geophysics from Cornell
University. Dr. Emerman was a professor of hydrology for 31 years, and has studied
and worked in issues of hydrology and mining for over 40 years. Dr. Emerman has
reviewed existing and proposed tailings storage facilities, including filtered tailings
storage facilities, in North America, South America, Europe, Africa, Asia, and Oceania,
and has testified on tailings storage facilities before the U.S. House of Representatives
Subcommittee on Indigenous Peoples of the United States. Dr. Emerman is the author
of the chapter on "Waste Disposal" in the upcoming SME Underground Mining
Handbook.
Bruce Johnson holds a BA in biology, chemistry minor, B.S. in secondary
education from Winona State University, certified hazardous material manager, and
30 years of experience in water quality and waste management. Johnson served as
the metal pathways field chemist for the Minnesota Regional Copper-Nickel Study,
researcher with the U.S. Environmental Protection Agency, copper-nickel mining
researcher with Minnesota Department of Natural Resources, team leader mining
permit enforcement with Minnesota Pollution Control Agency, and supervisor of
environmental compliance and research with Minnesota Department of
Transportation. He has authored and co-authored a number of environmental
research papers.
Amy Myrbo holds a B.A. in English and a Ph.D. in geology from the University
of Minnesota (UMN). She worked for 23 years at UMN studying human impacts on
lakes, wetlands, and wild rice waters, mainly in Minnesota, Wisconsin, and Montana,
and is now an independent consultant and part-time scientist at the St. Croix
Watershed Research Station, Science Museum of Minnesota. Dr. Myrbo was the UMN-
Twin Cities principal investigator for the Minnesota Pollution Control Agency's study
on the Sulfate Water Quality Standard to Protect Wild Rice, and has published several
peer-reviewed papers on the results of that research.
Diana M. Papoulias has a B.A. in aquatic biology from Prescott College, M.N.S
57

in zoology from Arizona State University, and Ph.D. in Fisheries and Wildlife from the
University of Missouri. Dr. Papoulias was a research fish biologist for 25 years at the
USGS Columbia Environmental Research Center where she studied the effects of
contaminants on aquatic species. She currently works with the non-profit E-Tech
International in South America as their aquatic toxicologist to assist indigenous and
rural communities adversely impacted by extractive industries, particularly oil and
mining.
Gerald J. Stahnke has a B.A. in biology from Hamline University and is an MPH
candidate at the University of Minnesota in Water Hygiene. Mr. Stahnke was
an Environmental Scientist at the Minnesota Pollution Control Agency for 38 years
working primarily in the Superfund Program. Mr. Stahnke previously worked for 5
years as an Aquatic Biologist with Barr Engineering focusing on Mining operations
and spent most of his time on the Teck copper-nickel deposit which was previously
known as the Minnamax/Babbitt deposit.
58

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