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Understanding the Impacts of Mining in the
Western Lake Superior region (Minnesota, Wisconsin,
and Michigan)
September 12-14,
2011
Bad River Lodge, Casino, and Convention Center
Odanah, Wisconsin
Agenda
September 12
Session: Western Lake Superior Region Mining and Risk
Mineral
Exploration and Potential Future Mining in the Lake Superior Region
John Coleman, Great Lakes Indian Fish
and Wildlife Commission, Madison, WI
Interest in development of metallic
mineral deposits has increased in recent years and the western Lake Superior
region has been the focus of much of that interest. We have used leasing of mineral rights,
exploratory drilling, and published materials to identify areas where there is
substantial interest in development of base and precious metal mineral
deposits. The three sources of
information vary by state in availability, completeness and accuracy but
combined provide a fairly complete picture of where base and precious mineral
deposits may be developed in the future. There are three centers of interest in base
and precious metal mineral development: the western Upper Peninsula of
Michigan, the northern third of Wisconsin, and the area of Minnesota along the south slope of the Mesaba Iron Range. We present an overview of where exploration
has and is taking place and highlight some projects that are in advanced staged
of characterization and development.
Presentation
Risk
and Regulation in the Mining Industry
Carol Cox Russell, Environmental
Protection Agency, Denver, CO
Mining
is a high risk venture in view of the multitude of unpredictable factors
producing the product and in the potential for impacts to human health and the
environment. Environmental policy-making
has become more dependent on formal, quantitative risk assessment, because of
increasing attention to the prevention of human health damage from toxic
chemicals.
Basically risk assessment has a straightforward
methodology: multiply the magnitude of a
loss by the probability that loss will occur.
Also “risk”
is often defined as a measure of the probability and severity of adverse
effects. Risk is comprised of three
elements: a source, a receptor, and an
exposure pathway by which the receptor is exposed to the hazards from the
source. EPA risk-assessment concepts,
principles, and practices are products of many diverse factors, and each agency
program is based on a “unique mixture of statutes, precedents, and
stakeholders” (F. H. Habicht II, February 1992) http://www.epa.gov/risk
Key principles of how mining is addressed in various laws and regulations and how risk assessment enters into decision-making will be addressed. Specifically EPA recognized that metals present unique risk assessment issues, and saw the need to develop a framework document that puts forth key scientific principles for metals risk assessments to help ensure consistency in metals assessments across EPA programs and regional offices. This framework, called the "Framework for Metals Risk Assessment," is a science-based document that describes basic principles that address the special attributes and behaviors of metals and metal compounds to be considered when assessing their human health and ecological risks. EPA 120/R-07/001 | March 2007 www.epa.gov/osa http://www.epa.gov/raf/metalsframework/pdfs/metals-risk-assessment-final.pdf
Development of a Mining 101 presentation
for Ontario’s Aboriginal Peoples
Peter Hinz, Ontario Ministry of
Northern Development, Mines and Forestry, Thunder Bay, ON
Mineral
exploration and development in Ontario has reached record levels and is being
fuelled by high commodity prices and demand.
The Ontario government has a Duty to Consult with Aboriginal peoples
where rights may affected by development proposals. The government also recognizes the need to
engage Aboriginal communities that could be affected by active mineral
exploration programs and proposed advanced exploration and development
projects. The “Mining 101” presentation
is the result of a 10+ year development of presentations to a variety of
audiences including: First Nations,
municipal councils, Chambers of Commerce, Rotary groups, provincial ministries
and the general public. The “Mining 101”
presentation is intended to be an interactive exchange.
Session: Mineral Deposits, Associated Geology, and
Mineral Economics
Sulfide
Deposits and Associated Geology in Michigan and Wisconsin
Klaus Schulz, U.S. Geological
Survey, Reston, VA
There
are two major types of sulfide deposits that occur in Michigan and Wisconsin: 1) volcanogenic massive sulfide deposits (VMS)
and 2) magmatic nickel-copper-platinum-group element (Ni-Cu-PGE) sulfide
deposits. The VMS deposits occur mostly
in a belt extending across northern Wisconsin from Ladysmith in the west
(Flambeau and Thornapple deposits) to across the Menominee River and into the
Upper Peninsula of Michigan in the east (Back Forty deposit). These deposits, hosted by Paleoproterozoic
(~1875 Ma) volcanic rocks of the Pembine-Wausau terrane of the Penokean orogen,
contain variable amounts of zinc (Zn) and copper (Cu) sulfides as well as some
gold (Au) and silver (Ag). The Crandon
deposit, which contains about 61 million tonnes of 5.6% Zn, 1.1% Cu, 1g/t Au,
and 45g/t Ag, is one of the largest deposits of this type in the world, ranking
in the top ten percent of known VMS deposits.
The VMS deposits were formed on the seafloor as heated seawater was
expelled from vents (black smokers) near rhyolitic volcanic centers.
The
magmatic Ni-Cu-PGE sulfide deposits of the area are related to small dike-like
mafic-ultramafic intrusions emplaced early in the history of the Midcontinent
Rift System, an extensional rift zone that formed about 1100 Ma as a plume of
hot mantle rose up beneath what is now Lake Superior. The Eagle deposit in the Baraga basin of
Northern Michigan, containing about 4.05 million tonnes of 3.57% Ni, 2.91% Cu,
and 1.48 g/t PGE+Au, is currently the only deposit of this type known in
Michigan-Wisconsin, but similar deposits are present in Minnesota (Tamarack)
and Ontario (Thunder Bay North). The
Eagle deposit belongs to a relatively newly recognized type of sulfide deposit
related to small intrusions that served as conduits for the movement of
basaltic magma through the crust. The
magmas, if they encounter a source of sulfur, may precipitate and transport Ni–
and Cu-rich sulfides to shallow levels of the crust. The resulting sulfide deposits, although
generally smaller than those formed in large intrusions like the Duluth
complex, tend to have higher metal concentrations.
The
Lake Superior Iron Ranges: Geology and
Mining
William
Cannon, U.S. Geological Survey, Reston, VA
Seven
belts, known geologically as iron ranges, contain sedimentary layers, commonly
called banded iron-formations, that are rich in iron and form the foundation
for the long history of iron mining in the western Lake Superior region. Iron has been mined from all seven ranges in
the past but only two, the Mesabi Range in Minnesota and Marquette Range in
Michigan, are currently active. Those
two ranges produce about 85% of the current U.S. demand for iron ore and are
capable of producing 100%, if needed, for the foreseeable future. Thus, the Lake Superior iron ranges are of
critical national importance, allowing a near self-sufficiency of this vital
raw material. The first ore discoveries
were in the 1840’s and mine production began soon after. From the earliest production until the 1950’s
ores were high grade concentrations of iron that occurred within the original
banded iron-formations. These ores
formed mostly by near-surface chemical alteration that removed non-iron-bearing
minerals and left behind a residual concentration of ore minerals. Beginning in the 1950’s, production began to
shift away from these high-grade ores, which were nearly depleted in many
areas. They were supplanted by taconite
mining, which mines and concentrates iron from the lower-grade banded
iron-formation itself and produces high-grade pellets of iron concentrate. These large operations, nine in total,
typically produce about 50 million tons of concentrate per year valued at about
$2 billion.
Continued
production of taconite from the Mesabi and Marquette ranges seems likely to
continue well into the future. Other
iron ranges, although containing large amounts of banded iron-formation similar
to that of the Mesabi and Marquette ranges, have geological complications that
inhibit mining under present technologic and economic conditions. The most prospective area for new taconite
mining is part of the Gogebic range in Wisconsin where as much as 3.7 billion
tons of ore have been estimated by previous studies. One segment of the range is currently under
evaluation by a mining company for future taconite development.
Mineral
Deposits and Geology of Duluth Complex, Minnesota
Jim Miller, University of
Minnesota Duluth, Duluth, MN
The
Duluth Complex is one of the largest gabbro complexes on Earth, underlying most
of northeastern Minnesota. It formed
during an attempt by the North American continent to rift apart about 1.1 billion
years ago and create an ocean basin in the breach. Magmas generated by mantle melting beneath
the crust erupted into the widening rift and formed an accumulation of lava
flows up to 20 kilometers thick. Much of
the magma also pooled deep within the lava flows to form the gabbroic intrusions
of the Duluth Complex. These magmas,
which are naturally rich in metals such as iron, nickel, copper, and precious
metals, but poor in sulfur, locally came into contact with sulfide-bearing
rocks. This interaction contaminated the
magmas in sulfur, which resulted in the production of sulfide liquid within the
magma. As this dense sulfide liquid
settled through the magma, it scavenged metals from the magma and ultimately
accumulated at the margins of the gabbro intrusions. There, the sulfide liquid crystallized to
form metal sulfide minerals within the gabbro.
Though originally formed several kilometer deep in the Earth, erosion
has now exposed this mineralized gabbro along a 50-mile-long belt just south of
the eastern end of the Mesabi Iron Range.
First discovered in the 1950’s, this mineralized area is now recognized
as comprising the largest undeveloped copper, nickel and precious metal
resource on Earth. Several companies are
currently in various stages of resource estimation, mine planning and
permitting.
Mineral
Deposit Economics – To Mine or Not to Mine
Keith Long, U.S. Geological
Survey, Reston, VA
The
decision to develop a mine is a lengthy and complex process that involves
private investors, governments, and other stakeholders. New mines are required to replace depleted
reserves and to meet increased demand for mineral products. A well-regulated, internationally-competitive
mineral industry should deliver mineral products at the lowest possible
cost. This includes efficient use of
labor, capital, and land at minimal environmental cost. There are numerous trade-offs at all stages
of mine development, principally between alternative investment
opportunities. From the time an investor
decides on a mining opportunity up to the time a mine is in operation, there
are some 12 principal steps and decision points: (1) determine an exploration
objective; (2) identify suitable prospects; (3) acquire exploration rights; (4)
preliminary geological survey; (5) initial selection of drilling targets; (6)
discovery; (7) selection among discoveries; (8) deposit delineation; (9)
preliminary economic evaluation; (10) feasibility studies and permitting; (11)
development and construction; and (12) commissioning. The Cadia Valley copper-gold mine in New
South Wales, Australia, serves as an example of a state-of-the art mine
developed in a highly regulated environment with significant stakeholder input,
including aboriginal interests. Some
years ago, a major global mining company, Rio Tinto, found that for roughly
every 3,000 of its prospect ideas, one new mine was developed. The time required to proceed from prospect to
mine is highly variable, depending on market cycles, project complexity,
political and regulatory environment, and quality of management. The 17 new metal mines developed in the
United States from 2000 to 2010 took from as little as 2 and as long as 17
years to be fully permitted, averaging 7 years.
The time required for exploration was often very protracted; some mine
sites were inactive for long periods of time due to market cycles and investors
finding better opportunities elsewhere.
A
More Holistic Economic Evaluation of Mining: Considering Costs and
Benefits
Thomas
Power, University of Montana, Missoula, MT
Mineral
extraction activities pay among the highest wages available to blue collar
workers, wages about twice the average. Given
these high wages, one would expect communities that rely heavily on mineral
extraction to be unusually prosperous. That,
in general, is not the case. Across the
United States mining communities, instead, are noted for high levels of
unemployment, slow rates of growth of income and employment, high poverty
rates, and stagnant or declining populations. In fact, our historic mining regions have
become synonymous with persistent poverty, not prosperity: Appalachia (coal), the Ozarks (lead), and the
Four Corners (coal) areas are the most prominent of these. Federal efforts have focused considerable
resources at overcoming the poverty and unemployment found in these historic
mining districts. In addition, the Iron
Range in Minnesota, the copper towns of
New Mexico, Michigan, Montana, and Arizona, the Silver Valley of Idaho,
the gold mining towns of Lead and Deadwood, South Dakota, etc. are also not
prosperous, vital communities. Over the
last several decades some of these areas have begun to recover as a result of
the in-migration of new, relatively mobile residents and economic activities,
but that recovery is entirely non-mining based.
The
dramatic contrast between the wealth created and the high wages paid in mining
and the poor economic performance of mining communities needs to be understood
before expanded mineral extraction activities can be safely promoted as a local
economic development strategy. This
presentation will look at the actual performance of mineral communities over
the last quarter century and then turns to an explanation for that relatively
poor performance.
September 13
Session: Mining and the Environment
Evolution
of Mining Practices in the Western Lake Superior Region
Allan Johnson, Michigan Tech, Houghton,
MI
Native
Americans were the first miners of native copper on the Keweenaw Peninsula and
Isle Royale as far back as 7000 years, producing copper weapons, tools and
jewelry. These products were also used
in trade throughout much of North America.
Modern
mining of copper and iron ore began in the Western Upper Peninsula of Michigan
in the 1840’s with copper mining continuing for 150 years until the closure of
the White Pine mine in 1995. Iron ore
mining has been continuous in Michigan and is still produced today on the
Marquette Range from two large open pit mines.
Early
mining was begun by hand labor using simple tools: steel drills and hand
sledges. Technological improvements over
time greatly increased mining production.
Blasting powder was replaced with nitroglycerine, dynamite and ANFO
(ammonium nitrate/fuel oil). Human labor
was aided by animals, steam power, compressed air, electricity and diesel
engines and modern mining machines of great variety. Transport of waste rock and ore likewise
benefited through modern innovation from human and animal power on land, to
railways and truck transport. Lake
transport was especially important to move mineral cargos from Lake Superior to
copper smelters and steel mills at lower lake centers. Completion of the locks
at Sault Ste. Marie in 1855 greatly expedited and lowered the cost of lake
shipping Later, copper was smelted near
the Michigan mines as milling and smelting processes advanced with
technological improvements comparable to those in mining.
Michigan,
Wisconsin and Minnesota became the leading producers of iron ore which greatly
spurred the growth and rising living standards in America. Steel production from Lake Superior iron ore
played a vital role in America’s role of helping to win two World Wars.
Mining
was the first industry to move into the wilderness of the former Northwest
Territory of our northern Great Lakes states. Heavy transportation via rail or,
better yet, lake shipping, was necessary to move bulk ores and metals to
market. In these early days, little
concern, if any, was given to protecting the environment and some mining
activities in some locations have not been favorable to the image of mining.
However,
over the last fifty years or so, lessons learned from poor outcomes at some
mining operations have resulted in improved working conditions and better
stewardship by the mining companies, especially in the areas of mine safety,
protection of the air and water, and returning mined-out lands to suitable and
productive uses. Today in Michigan,
mining remains a vital, profitable, sustainable industry, providing much needed
minerals for society, good jobs for employees, dollars for local communities,
the state and the nation. Out of necessity,
and through new legislation, the mining industry has evolved its often former
boom and bust reputation to one of a permitted and strictly self-regulated, but
enforced enterprise, committed to good stewardship from exploration to
extraction through acceptable mine closure practices guaranteed through bonded
contracts with the people through good government.
Acid
Mine Drainage (AMD) Environmental Issues – Underground and Surface Mining of
Sulfide Minerals
Chuck Brumleve, Keweenaw Bay
Indian Community, Baraga, MI
This
presentation will discuss the primary environmental concern related to the
mining of metal sulfide minerals. Metal
sulfide minerals, when exposed to air and moisture, undergo oxidation which
creates a solution of sulfuric acid and dissolved metals. The basic qualitative chemical reaction is
described as well as the how and why of acid metal drainage in the mining
environment. The three sources of the
sulfide reaction, wall rock, waste rock and tailings, are examined in light of
surface and underground mining. A brief
review of the legacy of acid mine drainage is undertaken followed by the
history and apparent state of the art of predicting impacts to surface and
ground water. This is brought into
context by looking at the implications of metal sulfide mining for the western
Lake Superior watershed. Lastly, the
philosophical approach to regulatory and permitting activities is examined in
light of sulfide mining’s legacy and industry’s technical capabilities.
Human
Health Aspects of Mineral Deposits and Mining
Geoff Plumlee, Suzette Morman,
U.S. Geological Survey, Denver, CO
Robert
Seal, U.S. Geological Survey, Reston, VA (presenter)
Mineral
deposits and mining present a number of risks to humans and the surrounding
ecosystems. Potential pathways to humans
include contamination of drinking water supplies and mineral dusts resulting
from the mining and milling or ores that can either contaminate soils and be
ingested or inhaled as airborne particles.
The toxic effects of mineral dusts and the bioaccessibility of elements
associated with these dusts are a complex function of the mineralogy of the
mineral dusts, its chemical composition, pathways into the human body, and the
biochemical conditions associated with target organs such as the lungs or
gastrointestinal tract. The USGS is
currently conducting studies on minerals commonly found in mine wastes to
understand the importance of these factors, which are yielding important new
insights.
Toxicity of
Metal-Contaminated Sediments from Mining Areas
John Besser, U.S. Geological
Survey, Columbia, MO
Toxic metals from mining, ore
processing, and smelting activities enter aquatic environments by a variety of
pathways. In receiving waters with
neutral pH, metals tend to move from water to sediment by settling of
particulate wastes and by precipitation and sorption of dissolved metals. Therefore, metals often accumulate to high
concentrations in bed sediments, leading to elevated metal exposure and toxic
effects on benthic organisms, principally benthic macroinvertebrates. Toxic effects of metal-contaminated sediments
on invertebrates can result in loss of metal-sensitive taxa and reduced productivity,
and surviving invertebrates may accumulate high levels of metals that pose
risks of toxicity to fish or other predators.
Field studies often cannot establish casual relationships between metal
exposure (via water, diet, and sediment) and observed impacts on benthic
communities. In contrast, laboratory toxicity
and bioaccumulation studies provide scientific proof of causal links between sediment
exposure and toxic effects. Sediment
toxicity testing is often used to support management decision at sites
contaminated by past or ongoing mining activities, and to meet regulatory
requirements for effluent discharges and disposal of metal-contaminated wastes.
This presentation will: (1) provide an overview of sediment toxicity
test methods, test organisms, and endpoints; (2) illustrate approaches for
interpretation and field validation of sediment toxicity test results; and (3)
demonstrate how toxicity data can support development of reliable sediment
quality guidelines for protection of benthic communities.
The
Effects of Mining on Air Quality
Trent
Wickman, U.S. Forest Service, Superior National Forest, Duluth, MN
What are the effects of mining emissions on air quality and the
environment? What regulations
apply? Who are the agencies that become
involved in the permitting and review of new mines? What types of environmental impacts are
possible? What types of monitoring can
be done to assess impacts? Case examples from the area will be discussed.
Bad
River in a Historical and Eco-cultural Context
Naomi Tillison, Cyrus Hester; Bad
River Band of Lake Superior Natural Resources Department, Odanah, WI
Geography
and governance influences resource distribution, which in turn drives practices
on the landscape. Environmental history provides a unique media for
understanding the impacts of historic land-use and provides a context for
future decision making. With this historic context established, the cultural,
ecological, social importance of the Kakagon and Bad River Sloughs is
highlighted. The Sloughs have earned many recognitions and awards due to its
diversity and uniqueness and the Bad River Tribe’s stewardship practices.
Session: Mine Permitting
Mine
Permitting Process in Michigan
Michelle Halley, National
Wildlife Foundation, Marquette, MI
This presentation will explain the permitting process for
non-ferrous metallic mining in Michigan.
We will discuss the primary permitting statute, Part 632 of Michigan’s
Natural Resources and Environmental Protection Act as well as other potentially
applicable state and federal laws.
Preparation for public participation in these processes will be
emphasized, as will key components of the various laws.
Mine
Permitting Process in Wisconsin
Thomas J. Evans, Wisconsin
Geological and Natural History Survey, Madison, WI
The
current mine-permitting process is characterized by a transparent process of
data-gathering and data-assessment, financial guarantees to support local
participation “early on”, financial guarantees to proactively address unforeseen
environmental impacts, determination of special taxes to ensure capacity to
address issues of boom/bust cycles, and, ultimately, a formal contested-case hearing.
The
present permitting process for metallic mineral development -- a currently controversial
economic activity in Wisconsin -- is the result of a consensus process in which
mining interests, environmental interests, state and local government
perspectives, and a State government and Legislature interested in crafting a
broadly acceptable policy for this resource were engaged in extensive
discussions and legislative action during the 1970s. These discussions were fueled by metallic
mineral exploration activity and the discovery of significant metal
resources. As a result of this permitting
process, two mines have been permitted and reclaimed, a world-class mining
project has twice been initiated and then withdrawn, and several smaller
metallic mineral deposits discovered, initially evaluated, and shelved.
Today,
there is renewed interest in developing Wisconsin’s mineral resources fueled by
high metal prices, a desire to create well-paying jobs in a difficult economic
time, and a perceived more favorable political climate. Accompanying this renewed interest is concern
on that part of the private sector that the present permitting process does not
work very well. Does it?
Mine
Permitting Process in Minnesota
Suzanne Baumann, Minnesota
Pollution Control Agency, St. Paul, MN
It is the
primarily the federal government that sets allowable levels for pollutants,
delegating their implementation to the states. Many states have developed unique ways to
implement the same regulations. Suzanne
will briefly discuss mining in Minnesota and talk about the Minnesota Pollution
Control Agencies environmental responsibilities, the nuances and challenges of
Minnesota’s permitting and environmental review programs.
Mine
Permitting – Roles and Responsibilities of the U.S. Army Corps of Engineers
Ralph Augustin, U.S. Army Corps of Engineers,
St. Paul, MN
This
presentation provides an overview of the Corps of Engineers regulatory program,
with an emphasis on the Clean Water Act and the role of NEPA in the permit
review process. The discussion will
focus on this process for projects that require the preparation of an
Environmental Impact Statement. It
includes an overview of major milestones in the NEPA process including
associated agency actions. Project
management through development of Memorandums of Understand and management plans
will also be discussed.
Solid
Leasable Permitting and Leasing Process - Roles and Responsibilities of the
U.S. Forest Service
Randy
Rabideaux, U.S. Forest Service, Washington D.C.
All
federal lands are comprised of a surface estate and a mineral estate. The mineral estate is either federally owned
or non-federally owned. If the mineral
estate is federally owned, the USDI Bureau of Land Management (BLM) possesses
the authority to manage the permitting and leasing of mineral resources in
conjunction with the U.S. Forest Service (FS) who manages surface resources. The primary set of regulations that the FS
uses for agency activities is the 36 Code of Federal Regulations (CFR), the BLM
uses 43CFR. The FS does not have
specific regulations for solids so the primary source for direction is the
Forest Service Manual 2820 that often cite portions of 43CFR Part 3500 which
are the specific regulations for the BLM. Since the BLM cannot permit or lease without
FS consent, the solid leasable permitting and leasing process requires frequent
communication, cooperation and coordination between the agencies.
September 14
Session: Geochemistry, Water, and Sediments
Pre-mining
Characterization and Prediction
Robert
Seal, U.S. Geological Survey, Reston, VA
The
process of designing, permitting and developing a mine requires a number of
environmental studies that serve numerous purposes. Pre-mining baseline characterization is
important for establishing monitoring sites for use throughout the mine life
cycle for all stages including design, permitting, development, operation,
closure, and beyond. The baseline
characterization exercise is equally important for establishing closure goals
because mineral deposits are geochemical anomalies that express themselves in
all media including surface water, groundwater, sediment, soil, and biota. In many cases, these expressions naturally
exceed regulatory guidelines. Another
important aspect of pre-mining environmental studies is the prediction of the
behavior of mine-waste materials to inform decision planning for waste
management practices and closure strategies.
A key point with regards to environmental challenges associated with
future mining is that no two deposits are alike. Differences arise from the geological
characteristics of the ore deposits being mined, their geologic settings, the
mining and ore processing methods being used, the hydrologic setting of the
mine and its wastes, and climate.
Estimating Solute Release from
Proposed Mining Operations
Kim
Lapakko, Minnesota Department of Natural Resources, St. Paul, MN
Four
general components are presented to aid in quantifying solute release from mine
waste facilities at proposed mining operations.
The first is mine plan development, which extends beyond description of
mining, processing, and other aspects of economic resource recovery. This plan must also identify the wastes to be
generated and describe the predicted mass, compositional range, and schedule of
generating mine wastes, as well as the intended plan for disposal. As the degree of detail in the plan increases,
so does the potential for efficient environmental review. Irrespective of initial detail, the plan will
likely evolve iteratively over the course of more refined environmental and
economic analyses.
Second,
there are existing mine-specific resources, including those on which the mine
model is designed, that can be used for preliminary environmental
analysis. Baseline water quality data,
the geology of the site, and geoenvironmental modeling literature will provide
an indication of what solutes might adversely impact water quality. The mine model is largely based on drill core
samples that describe the location, concentration, and mineral form of economic
resources. Similarly geologists’
description of drill core and any existing analyses of the core from “waste
rock zones” can be used to determine the location and some compositional
aspects of the potential waste rock.
Drill core also represents a source of waste rock (and ore) samples for
testing to evaluate potential to release potentially problematic solutes. Additionally, mineral processing tests
conducted to evaluate economic constituent recovery from ore can provide
tailings samples for environmental testing.
If appropriately designed, these tests can also provide water quality
data to help inform questions regarding solute release from tailings.
Third,
using drill core and tailings discussed above, testing can be conducted on
samples representative of the wastes.
The tests conducted must consider the conditions under which the mine
waste is to be disposed, as described in the mine plan, and should have clearly
defined objectives. Solid-phase tests
include 1) conventional chemical analyses that indicate how much of a specific
chemical component is present; 2) mineralogical, and petrologic analyses that
indicate the mineral in which chemicals are present and the availability of
minerals for dissolution; 3) sequential extractions to assess the ease with
which specific solutes can be leached from solids; and 4) static tests
(acid-base accounting) designed to assess the likelihood that materials will
generate acidic drainage; 5) short-term leach tests (e.g. meteoric water
mobility procedure, synthetic precipitation leach procedure, USGS field test);
and 6) kinetic tests to assess the dissolution behavior of mine wastes over the
course of years and decades.
Fourth,
a model is constructed to describe the chemical release from mine waste
disposal facilities based on the mine plan and the information collected
above. The mechanics of the model should
be transparent as opposed to a “black box” or proprietary model. It should accurately describe the physical
situation to be modeled, present a scientifically based conceptual model that
describes factors controlling solute release from source terms, use algorithms
that accurately reflect the conceptual model, and incorporate sound data and
assumptions. Sensitivity analyses should
be conducted to identify influential variables in the model. Uncertainty ranges for input values of
influential variables should be used to generate a probabilistic description of
the outputs. Outputs should be checked
for accuracy by using simplified calculations, comparison with output generated
by other models, or comparison with empirical data.
Application
of the mass-loading approach to understanding the impacts of mining
Briant Kimball, U.S. Geological
Survey, West Valley City, UT
Watersheds
in mineralized zones may contain many mines, each of which can contribute to
acidity and the metal load of a stream. Combining
the injection of a chemical tracer, to determine stream discharge, and synoptic
sampling, to obtain the chemistry of major ions and metals, spatially detailed
load profiles are quantified. Using the
discharge and load profiles provides a means to answer important questions
about the remediation of mining impacts. (1) Combining the data from a
mass-loading study with the reactive solute transport capabilities of the OTEQ
computer model gives an approach to estimate pre-mining concentrations of
metals in the streams. (2) Various remediation options can be evaluated in
terms of the load reduction they can provide,
using both the OTEQ and the OTIS computer models with the mass-loading
data. And (3), the effectiveness of
stream restoration on reducing metal concentrations can be assessed in a very
detailed spatial approach. These three
applications are illustrated by field experiments in streams affected by mine
drainage in Colorado and Montana. These
applications can help land managers make decisions about how to most
effectively remediate mining impacts.
Art Horowitz, U.S. Geological
Survey, Atlanta, GA
During 1989/1990 a series of 12 gravity cores, and 150 surface grab samples were collected in Lake Coeur d'Alene (Lake CDA), Idaho. Substantial portions of the surface and near-surface sediments in the lake are markedly enriched in Ag, As, Cd, Hg, Pb, Sb and Zn, and somewhat enriched in Cu, Fe and Mn. Surface distribution patterns, as well as variations in the thickness of the trace element-rich subsurface sediments, indicate that the source of much of this enriched material is the CDA River. An estimated 75 million metric tons of trace element-rich sediments have been deposited on or in the lakebed. Based on a 1980 Mt. St. Helens' ash layer, ages estimated from 137Cs activity, and the presence of 80 discernible and presumably annual layers in a core collected near the CDA River delta, indicate that the deposition of trace element-rich sediments began some time between 1895 and 1910, dates consistent with the onset of mining and ore-processing activities that began in the area in the 1880's.
During 1998/1999, surface and subsurface
sediment samples were collected along the
entire length of the Spokane River Basin
(SRB) from its outlet at the northern end of
Lake CDA to Lake Roosevelt on the Columbia
River, Washington. Surface sediments in
the SRB are enriched in Pb, Zn, As, Cd, Sb
and Hg relative to local background levels.
Pb, Cd, and Zn are the most elevated, with
maximum enrichment occurring in the upper
SRB in close proximity to Lake CDA. On average, enrichment decreases downstream,
apparently reflecting both increased
distance from the inferred source (the CDA River
Basin), as well as increased dilution by
locally derived but unenriched materials. Based
on 137Cs and excess 210Pb dating, trace
element enrichment began in the middle part of
the SRB (Long Lake) between 1900 and 1920,
whereas in the most downstream part of
the basin, enrichment began between 1930
and 1940, probably as a result of the closure
of the Grand Coulee Dam (1934-1941), which
formed Lake Roosevelt, backed up the
Spokane River, and increased water levels
in the River Arm by about 30 m.
Use
of Groundwater-flow Models in Mine Permit Evaluations
Michael N. Fienen, U.S.
Geological Survey, Madison, WI
The
assessment of potential water resources impacts of mining projects is an
important element of mine permit evaluation. Many aspects of the hydrologic cycle and
geologic framework play important roles in these evaluations. A model provides a way to combine the
conceptualization, field measurements and observations, and physical and
chemical laws in a framework. The model
can then be used to evaluate how the hydrologic system reacts to various
changes, including those caused by mining operations. Examples of impacts that can be evaluated
include water quality changes do to adding or removing specific compounds from
the water, changes in streamflow, changes in groundwater levels, changes in
water supplied to wetlands, and others.
The key
concepts in groundwater modeling are conservation of mass, conservation of
energy, and correspondence between model outcomes and actual measurements. Conservation of mass means that water, in this
case, cannot be created or destroyed, so the model must make an accounting of
water balance into and out of the system. Conservation of energy is honored similarly by
the model balancing energy inputs and outputs - this controls how water moves
through the area being simulated. Finally,
the correspondence between model outcomes and measurements is enforced through
model calibration and uncertainty analysis.
The
process of using a model to evaluate these potential changes is similar to
using physical models and computer models in engineering design of bridges,
buildings, and other structures. The
models allow for evaluation of responses to changes in conditions and enable
incorporation of safety factors. In the
case of mining permit applications, this enables decision makers to make
evaluations of permits in a way that is protective of water resources.