SECTION 5
RELEVANT UNITED STATES ENVIRONMENTAL
PROTECTION AGENCY GUIDANCE FOR
ENVIRONMENTAL IMPACT ASSESSMENT
REVIEWERS
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5. ENVIRONMENTAL IMPACT ASSESSMENT GUIDELINES
USEPA: (05/98)
Hie US Environmental Protection Agency (USEPA) has a responsibility for independent review
of draft and final environmental impact statements prepared by other federal agencies. USEPA also
must comply with requirements related to environmental impact assessment for its potential permit
actions for new water dischargers. In meeting these responsibilities, USEPA has produced several
guidelines which may serve as a useful resource to reviewers around the globe. Two such guidelines are
included hi this resource manual hi their entirety, the others are available upon request.
Sector specific Environmental Impact Assessment Guidelines: These
guidelines were developed for USEPA staff responsible for preparing Environmental Impact
Assessments (EIAs) for new source permits under the National Pollutant Discharge Elimination System
(NPDES) for facilities in specific industries. The guidelines assist staff hi determining the scope and
contents of such EIA's and are used hi preparing, overseeing preparation, or reviewing and commenting
on environmental impact assessments for these activities:
Fossil Fueled Steam Electric Generating Stations (1994)
Pulp and Paper and Timber Products (1994)
Petroleum Refineries and Coal Gasification Faculties (1994)
*Mining (1994)
Phosphate Fertilizer Manufacturing Facilities (1981)
Canned and Preserved Seafood Processing Facilities (1981)
Mechanical Products Manufacturing Plants (1981)
Phosphate Fertilizer Manufacturing Facilities (1981)
Rubber Manufacturing Facilities (1981)
Explosive Manufacturing Industry (1981)
Non-Fertilizer Phosphate Manufacturing (1981)
This resource manual includes the guidelines prepared for Mining (5.2).
Guidance for reviewers of EIA documents; Separate guidelines are prepared for
USEPA reviewers of EIAs:
Highway Development:
Cumulative Impacts:
Environmental Justice:
Pollution Prevention:
Habitat Evaluation:
^Evaluation of Ecological Impacts (1994)
Council on Environmental Quality Handbook on
Considering Cumulative Effects Under the National
Environmental Policy Act (1997)
Guidance for Addressing Environmental Justice in
EPA NEPA Compliance Analysis (1998)
Guidance for Addressing Environmental Justice hi
§309 Reviews (1998)
Guidance for Pollution Prevention (1994)
Guidance for the Review of Environmental Impact
Assessment Documents (1993)
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Mill! hi, III I,,
Grazing on Federal Lands: Background for NEPA Reviewers (1993)
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The guidance on review of highway projects for ecological impacts is included in its entirety in
this resource manual (5.1)
OTHER
T^ binder is designed to add other key guidance documents for easy reference.
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SECTION 5.1
EXAMPLE 1: ECOLOGICAL IMPACTS FROM
HIGHWAY DEVELOPMENT
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EVALUATION OF ECOLOGICAL IMPACTS
FROM HIGHWAY DEVELOPMENT
April 1994
U.S. Environmental Protection Agency
Office of Federal Activities
401M Street, SW
Washington, DC 20460
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EVALUATION OF ECOLOGICAL IMPACTS
FROM HIGHWAY DEVELOPMENT
EPA Contract No. 68-CO-0070
Work Assignment 2-06
April 1994
Submitted to*
Jim Serfis
U.S. Environmental Protection Agency
Office cf Federal Activities
401M Street, SW
Washington, DC 20460
Submitted by:
Mark Southerland*
Dynamic Corporation
The Dynamac Building
2275 Research Boulevard
RocknOe, MD 20850
iUr it lit oddrctt!
Veaar, Inc.
9200 Runuey Road
Columbia, MD 21045
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CONTENTS
1. Introduction 1
1.1 Definition of Ecological Impacts . ,. . . l
1.2 Report Format -. . 2
2. The Need for Ecological Analysis in Highway Projects 3
2.1 NEPA Mandate 3
2.2 Federal Highway Administration Mandate 3
2.3 Relation of Ecosystem Protection Goals to FHWA Guidance 5
3. Impacts of Highways on Ecosystems 7
3.1 Highway Development Activities '. 7
3.1.1 Planning Phase 7
3.1.2 Design Phase 8
3.1.3 Construction Phase 8
3.1.4 Operation and Maintenance Phase 8
3.2 Types of Impact to Ecosystems 8
3.2.1 Destruction of Habitats . 10
3.2.2 Fragmentation of Habitats 10
3.2.3 Degradation of Habitats 13
3.2.4 Cumulative Impacts ...;.... 15
4. Ecosystem Approaches in Highway Development 17
4.1 Categories of Highway Development . . . .' 17
4.1.1 Urban 18
4.1.2 Suburban 18
4.1.3 Rural 18
4.1.4 Wfldland :...'' 19
4.2 Approaches and Ecosystem Protection Goals '. . 19
5. Evaluation of Ecological Impacts ;.... 21
5.1 Determining the Appropriate Scale 21
5.2 Establishing Ecosystem Goals and Endpoints 21
5.2.1 Ecosystem Endpoints 23
5.3 Garnering Ecosystem Information 25
5.4 Analysis of Impacts 26
5.4.1 Analytical Approach 27
5.4.2 Classification and Mapping of Habitats 28
GIS — Geographic Information Systems 29
5.4.3 Characterization of Habitat Values and Impacts 29
Species Characterization 29
Aquatic Habitat Characterization 30
Wetlands Characterization 31
Ecological Impacts of Highways iii . April 1994
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I'," ; , L.. :,• ;- .I" ,•; "" Terrestrial Habitat Characterization''. . . . :>.;N. . . . v. . . . . . . . • • • .;v. .32
H'} | , "i''; i'f $.4.4 Comparative M^&ods .'........'.'..'."...'.'. ."...... ."'. . . .'" .-' "'33
5.5 Evaluation of Qnnuladve Impacts . . . • •'••"• - • • • • •• • • • • • • • • • 37
r6.' r%fitigation Measures for Ecological Impacts of" Highways"'.....'..-. '" 39
v'': " "eii""" Eco'system Approach to Mitigation .. .'. ."."". . "."". .'.......•/.-. • • • 39
6.2 Mitigations for Each Phase of Highway Development '1' 40
!> ; i •'•«; '6,2.1^ iiPjanningiPhase ..|........... .. .. :/ . .^. ............. . ^ 41
;",. ', . ' ".! gjj^ Design Phase ...... I". ....". . .". .'.'• .''..".".'.'.'... '. ........ " 44
pi; ''.j,i^ i, jsi'i; '112.4'"" o^g^gQn'and Maintenance Phase . .... I ....'.' '.'. .'. . . .".'.'.' •'." •'." 52
els Ecological Restoration as Mitigation 55
•614 Mitigation Monitoring • 56
:7. 'Summary of Mitigations for Ecological Impacts". .'... ..."I"........."..'.'.' 59""
8. Bibliography .;.......,..: 61
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Table of Tables
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Table 1. - Approaches to Meeting Ecosystem Protection Goals Wmin
Four Categories of Highway Development 20
Table 2. Ecosystem Endpoints Associated with Ecosystem Protection Goals for
- Use in Environmental Assessment of Highway Development . . I . . .
Table 3. Hypothetical Comparison of Effects of Alternatives on Ecosystem Endpoints ... 36
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Table 4. Principal Mitigation Measures for Ecological Impacts By Phase and
• Setting of Highway Development ... 1 58
Table of Figures. •
Figure 1. Mitigations in the Planning Phase •' • • 43
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Figure 3. Mitigations m.the Construction Phase -*
Figure 4. Mitigations in me Operations and Maintenance Phase 54
'Ecological Impacts of Highways iv . April 1994
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1. Introduction
The purpose of this report is to provide guidance for the analysis of ecological impacts from
highway development activities and me evaluation of related ecosystem mitigation measures. This
guidance will support NEPA reviewers in providing informed comments for project scoping, EIS review,
and 309 analyses regarding the issue of ecological degradation resulting from highway development and
similar activities. It is hoped that mis report wfll also be used by the Federal Highways Administration
(FHWA) and other federal agencies that do not have land management responsibilities as they consider
ecological issues in environmental analyses. Where appropriate, EPA program offices may want to
support FHWA and other federal agencies in assessing the environmental risks of then' proposed actions
and in developing mitigations for these impacts.
This report builds on the guidance provided by the earlier EPA report, Habitat Evaluation:
Guidance for the Review of Environmental Impact Assessment Documents, and provides specific
information on the ecological impacts associated with highway development. A primary focus of mis
report are the potential mitigations that may implemented during highway planning, design, construction,
and operation. Many of the degrading activities and accompanying ecological impacts associated with
highway development are also relevant to other construction-based projects such as power generation and
industrial or residential development. By providing detailed guidance on both ecological analysis and
mitigation, mis report should improve the environmental impact assessments for a wide range of
development activities.
1.1 Definition of Ecological Impacts
The evaluation of ecological impacts has traditionally been limited to the consideration of
individual species, their immediate habitats, and general natural resource categories such as water and
air quality.. Although this approach has afforded some protection to individual species and their
ecosystems, it is inadequate for regional or global biodiversity protection efforts. The need to address
the conditions of a wide range of species, and biological diversity hi general, requires an ecological
approach to analysis mat focuses on ecosystems. Therefore, mis document defines ecological impacts
as any and all changes hi the structure and function of ecosystems.
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of concern are defined as those sensitive environments whose degradation or loss results in significant
diminution 6f regional biodiversity (see Council on Environmental Quality 1993). The condition of these
ecosystems can be evaluated in terms of both structure and function and should reflect holistic measures1
of ecosystem health or ecological integrity (see Costanza et al. 1992).
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While ecosystem are often classified by broad vegetation-based categories, each ecosystem is
unique and must be evaluated in the context of its specific geographic location. At the same time,
alteration of an ecosystem by degrading activities must be considered hi terms of the impact on the entire
landscape. Therefore, an ecosystem perspective is essential fox the adequate'consideration of ecological
impacts. This approach requires mat the interactions of ecological components be considered, and mat
the un|que characteristics of each ecosystem be evaluated.
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Quality (1993) report, Incorporating Biodiversity Considerations
Into Environmental Impact Analysis Under the National Environmental Policy Act, recommends an
ecosystem approach to biodiversity conservation. Therefore, the approach and methods described hi this
report are consistent with the increased emphasis being placed on preserving biodiversity. As evidenced
by "thereports "of"fee Office of Technology Assessment (U.S. Congress, OTA 1987) and the National
Academy of Sciences (Wilson1988), awareness of the immense social and intrinsic values of biodiversity
. has increased greatly in'recent years. ' The diversity of species 'and genetic steams 'provides a pool of
critically important resources for potential use 'in agriculture, medicine, and industry; the loss of wild
plant ami animal species that have not been tested, or in some cases not yet described, would deprive
society of these potentials. Access to genetic resources contributes about $1 billion annually to U.S.
agriculture through development of unproved crops. Livestock and other sources of protein benefit from
mis access as well. About 25 percent of our prescription drugs are derived from plant materials, and
many more are based on models of natural compounds. Native species themselves are essential as
foodstuffs and are valuable as commodities such as wood and paper. Marine biodiversity, hi particular,
plays a major role in 'meeting;""tneprotein needs of the'world. At the ecosystem level, biodiversity is
essential to the continued provision of important ecological services, such as regulation of hydrologic
cycles, carbon and nutrient cycling, soil fertility, and commercially and recreationally important fish and
wildlife populations. .
1.2 ' Report Format
';;;;;;: [ The following sections of "this report" present the specific' approaches and methods required for
adequate evaluation of ecological impacts from highway development. Section 2 illustrates how the
evaluation of ecological impacts meets existing requirements for integrated NEPA analyses. Section 3
discusses the many specific impacts to ecosystems mat result from highway development activities.
> Section 4 provides the basic framework for addressing ecosystem conservation through evaluation of
highway impacts. Section 5 presents specific methods for evaluating these impacts, including identifying
^ '.^-gg'^jg"g^Qgy^jj"assessment"endpoints. Section 6 follows with specific mitigation measures that may
fie applied to address the impacts to these endpoints. Finally, Section 7 provides a summary table of
impacts in different settings. A bibliography is included as Section 8.
Ecological Impacts of Highways
April 1994
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2. The Need for Ecological Analysis in Highway Projects
Traditionally, NEPA analyses of ecological resources have emphasized threatened and endangered
(and certain commercially important) species, wetlands (and other sensitive aquatic habitats), and
protected areas (such as parks and refuges). As the understanding of ecosystem functioning has
increased, more comprehensive and sophisticated ecological analyses are possible. .The recent Council
on Environmental Quality (CEQ) report (1993), Incorporating Biodiversity Considerations into
Environmental Impact Analysis Under the National Environmental Policy Act, illustrates me increased
level of analysis mat is now expected from environmental impact assessments. Improved ecological
analysis is also the goal of continuing efforts to strengthen the integration of NEPA considerations with
other environmental assessment activities (Bausch 1991). Efforts to develop methods fat cumulative
effects analysis have also been ongoing, and they are expected to culminate in publication of a
practitioner's handbook by the end of 1993 (Ray Clark, CEQ, personal communication).
2.1 NEPA Mandate
Section 102(2) of NEPA requires a systematic, interdisciplinary approach mat integrates science
and environmental design into the decision-making process. In addition, CEQ regulations require
integrating NEPA requirements with other environmental review and consultation requirements. Both
of these provisions are designed to meet the basic objective of NEPA which is—to integrate environmental
quality objectives comprehensively into planning. The ecosystem approach, as embodied in this report,
provides the framework for a truly integrated assessment of environmental objectives. Because it requires
consideration of the interactions among the full range of ecological resources and focuses on the integrity
and functioning of the landscape or regional ecosystem, the ecosystem approach is ideal for integrated
NEPA assessments. .
2.2 Federal Highway Administration Mandate
There are nearly 4 million miles of roads hi the United States. Such a complex system has the
potential to alter the natural environment hi a myriad different ways, and includes the potential for large
cumulative and secondary impacts. The NEPA process offers federal and state highway authorities a
unique tool for considering the full range of environmental impacts from highway development.
The FHWA has recognized the importance of environmental assessment in its Environmental
Policy Statement (EPS) of 1990, establishing policy to avoid, nrinhniga, and mitigate adverse
environmental impacts. The statement gives the environment full consideration along with engineering,
social, and economic factors in project decisionmaking and stresses the need to fully integrate
environmental considerations into agency policies and procedures. Of particular concern to FHWA is
the requirement to-consider the possibility of secondary and cumulative impacts of agency actions.
Cumulative impacts are defined hi 40 CFR 1508.7 (1978) as "the impact on the environment which
results from the incremental impact of the action when added to other past, present, and reasonably
foreseeable future actions." To achieve the balanced consideration of these and other impacts,
environmental concerns must be addressed in the early stages of planning and throughout project
development. The ecosystem approach provides a means of identifying the entire complement of
resources and interactions that must be understood to adequately consider cumulative and indirect impacts.
Ecological Impacts of Highways 3 . April 1994
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Is especially important when the affected environment is'largely undisturbed, while 'm human-altered
a ta^eted' resource approach may be equally valid. ,
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nphasis on integrated assessment of environmental impacts from highway development is
in the 1991 Intermodal Surface Transportation Efficiency Act (ISTEA). ISTEA (U.S.
1991) states mat . .
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"It is the policy of the United States to develop a National Intermodal Transportation System that
is economically efficient, [and] environmentally sound...
and tii at
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".;. Social benefits must be considered with particular attention to the external benefits of reduced
air pollution, reduced traffic congestion and other aspects of the quality of Me hi the United
!• ..... ' ..... :States? ................ ' ' ' ............... |
........ i _ .
ISTEA also contains provisions requiring FHWA to work with State highway agencies as never before
to preserve and enhance environmental resources while implementing transportation programs.
Specifically States are required to "... undertake a continuous transportation planning process... " which
includes statewide and metropolitan plans (including long-range plans) consistent with existing plans under
the Clean Air Act and Clean Water Act, that consider the
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"... overall social, economic, energy, and environmental effects of transportation decisions."
Projects related to ecosystem conservation mature eligible for federal funding under either the
National Highway System or the Surface Transportation Program include the following (emphasis added):
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"... participation m wetlands mitigatkm efforts related to projects funded under this tide, which •
may include particqjation hi wetlands mitigation banks; contribution to statewide and regional
efforts to conserve, restore, enhance and create wetlands; and development of statewide and
regional wetlands conservation and mitigation plans, including any such banks, efforts, and plans
authorized pursuant to the Water Resources Development Act of 1990 (including crediting
provisions)...
. "... Construction, reconstruction, rehabilitation, resurfacing, restoration, and operational
improvements for 'filgnwajs (including bridges on public roads of all functional classifications),
including... mitigation of damage tn wildlife habitat, and ecosystems caused by a transportation
project funded under this tide... .
«... Highway and transit safety improvements and programs, hazard eliminations, projects &
mitigate hazards caused bv wildlife, and railway-highway grade crossings."
Implementation of such wfldlife andecosystem mitigation measures, as well as upfront, areawide
planning, can be fecffitated by incorporation of an ecosystem approach into me environmental
documentation process for highways. For example, me concepts of corridor preservation and integrated
l^usipla^ In many
cases, a regional ecosystem approach can help unite transportation planning widi the land use and
Ecological Impacts of Highways 4 April 1994
* '" ••
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resource management planning process of local and regional communities. The next section discusses
the relationship between ecosystem protection goals and the existing FHWA environmental documentation
process.
23 Relation of Ecosystem Protection Goals to FHWA Guidance
As discussed previously, the FHWA has already developed substantial guidance on the evaluation
of effects on natural resources, including cumulative and secondary impacts. In highly urbanized and
other disturbed environments, existing environmental documentation activities are adequate for assessing
impacts from highway development. However, federal highway assessments involving largely
undisturbed natural environments could be improved by placing mem in the framework of an ecosystem
approach. An ecosystem approach entails application of princhries of ecosystem protection (Le.,
biodiversity conservation) as described by CEQ (1993). The following six principles of ecosystem
protection are already implicit in many of FHWA requirements and policies, and their explicit
incorporation in environmental documentation can strengthen highway assessments:
• . Evaluate within a regional context. The "logical termini" provision in FHWA regulations and
guidance is designed to prevent segmentation of projects and requires the use of a "rational
endpoint for review of environmental, impacts". This provision requires mat an individual
highway project cannot be used to force improvements hi other highway sections. Application
of a' regional analysis of highway development, one mat considers bom the functional utility of
the highway and the effects on the larger ecosystem, can help ensure that the best logical termini
are chosen. At the same time, use of a regional context for assessment can greatly facilitate the
consultation process with other agencies and involved parties. By addressing development within
a region, other planning and management activities are more easily incorporated. Incorporation
of these plans is a goal of the 1992 FHWA guidance on secondary and cumulative impacts.
• Preserve sensitive communities and ecosystems. FHWA regulations (40 CFR 1502.15) state mat
the affected environment includes "environmentally sensitive features". Consideration of the
variety of different habitat types is essential to protecting the larger ecosystem. Usually, natural
resource cooperators are required to point out habitats of concern other man wetlands. An
inventory of ecosystem (habitat) types should be conducted earlier in the planning process. This.
inventory would also serve to identify Section 4(f) lands (Le., public parks, recreation areas, and
wildlife and waterfowl refuges with national, state, or local significance), as required by FHWA
regulations.
• Maintain natural habitat struct"^ and ecosystem processes. The 1992 FHWA guidance on
cumulative and secondary impacts stresses the need to consider indirect effects, such as those on
ecosystem processes. An ecosystem approach that applies strong ecological expertise is the best
means of evaluating indirect effects among ecosystem components. Application of an ecosystem
perspective can also help identify important indirect effects such as the impact of exotic species.
• Protect rare or ecologically important species. Affifa, consideration of "envJmnmftntaHy sensitive
features" under FHWA regulations requires mat assessment extend beyond the traditional
categories of listed endangered (and threatened) species and game species to include rare and
"keystone" (ecologically important) species. An ecosystem approach would include consideration
Ecological Impacts of Highways 5 April 1994
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of me full complement of species in an ecosystem, and would coordinate their protection with the
preservation of sensitive habitat types.
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Ecological Impacts of Highways
April 1994
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3. Impacts of Highways on Ecosystems
The construction of highways can have a substantial impact on die degradation and loss of natural
ecosystems, especially in less developed areas. Although the actual areas converted by highways,
railways, and power line right-of-ways may cover only a small proportion of a region, these areas total
27 million ac nationwide. Perhaps more importantly, the fragmentation of habitats caused by highway
development is often severe (Frey and Hexem 1985). Transportation routes can be described as
"disturbance corridors" mat disrupt the natural, more homogeneous landscape (Barrett and Bohlen 1991).
In forested environments, these disturbances can cause (1) dramatic physical disruption to the continuous
vegetative community; (2) disruption to the structure and function of habitat; and (3) impacts to resident
wildlife, which must negotiate, tolerate, and cope with the habitat barriers. In addition, disturbance
corridors created by forest fragmentation alter the natural mix of habitats and species by providing
conditions suitable for early successional plants and animals. They replace forest trees with grasses and
shrubs, eliminating nesting habitat for forest-interior species. While they provide dispersal routes for
certain small Tngmmak3 they present barriers to many species.
The scale of both the habitat conversion and habitat fragmentation effects caused by highway
development varies with the size of the project. The impacts of projects also vary according to the
environmental setting, especially the degree of naturalness in the local and regional ecosystems. In many
cases, small individual highway projects may have little or no impact on natural ecosystems. In other
cases, large projects can have dramatic impacts on wfldland areas (areas that are largely undisturbed by
human activity). Evaluations based on only a few species or resources may be adequate for small
projects. However, it is important to consider the contribution of small projects to the cumulative impacts
on the region. Although individual road segments may cause only minor environmental impact, the
combined effect of the entire highway system may seriously degrade the natural environment. In the
same way, the cumulative impact of several highway systems can seriously affect entire regions,
disrupting migratory pathways and other ecosystem processes. These effects may be augmented, or even
overwhelmed, by secondary development, i.e., the land conversions to industrial or residential use that
usually accompany road building.
3.1 Highway Development Activities
Highway development consists of four phases of activities: planning, design, construction, and
operation. Each of these phases involve a number of specific actions that vary with each highway
development project. As described in the introduction, an ecosystem is defined to include all the relevant
natural resources affected by highway development projects. These include air quality, water quality,
wildlife, wetlands, and all other types of natural communities. The planning and design phases of
highway development determine which ecosystems will be affected, while the construction practices and
operation and maintenance procedures actually cause the ecosystem impacts.
3.1.1 Planning Phase . • •
The planning phase involves all pre-design activities including the siting of the highway corridor.
Planning proceeds from the purpose and need for the project and includes consideration of all various
transportation options, potential locations, and possible basic designs. In essence, mis phase determines
the locations (and sensitive habitats) to be affected by selecting the corridor route. Selection of me
Ecological Impacts of Highways 7 April 1994
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highway type and basic configuration and number of interchanges also contributes to identifying the
ecosystems 'to be affected. Both direct destruction of ecosystems and potential degradation based on.
proximity are determined in this phase.
"34.2 Design Phase ' ' """ • "
||. ' ", '.
ThiJesign phase involves the siting of the final right-of-way footprmt and aUaspecte^
design and within design mitigations. By selecting such highway parameters as width, slope, and type
of crossing structures (e.g., bridges), mis phase actually determines the specific potential impacts on
adjacent and nearby ecosystems. While planning determines the general areas where habitat wfll be
destroyed or degraded (areas within the highway corridor), design decides which specific locations wfll
be affected or avoided. For mis reason, small-scale mitigations are most important in the design phase.
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3.13 Construction Phase
The constraction phase involves the vegetation removal, earth moving, and road building activities
mat actually impact sensitive habitats. Although the habitats to be affected and me types of impacts are
already determined by the preceding phases and the basic requirement of highway construction, the
specific operation of construction activities may determine the severity of impacts such as erosion and
iisturbiicel wile vegetation removal is inherent within the roadway footprint, excessive vegetation
clearing can be eliminated. In addition to physical destruction of habitat within the footprint, soil erosion
and other forms of pollution are the primary impacts in mis phase. Mitigations involving bom the timing
and performance of these activities can dramatically reduce these latter adverse impacts.
3.1.4 Operation and Maintenance Phase
The operation and maintenance, phase includes all post-construction activities associated with the
built project, including routine vehicle traffic and roadway maintenance, as well as accidents and spills.
Routine maintenance activities include the following (Krame et al. 1985):
;•;: * ^ "•, ,vl., Roadwaypaviogandpatchmg. •' .
• Roadside blading and litter collection.
• Vegetation management (including mowing, chemical control, planting, seeding, and
fertilizing). ,
• Cleaning, painting, .and repair of roadside structures, including curbs, drams, guardrails,
i , Jjj ' • '" '™ Street cleaning, snow removal, lighting, abrasives, and pavement marking.
• Equipment cleaning and hazardous material handling and storage.
I III I 1111 III* * , „ . • :
Although similar in nature to construction impacts, the pollution effects of this phase are long term. Best.
management practices are the principal mitigation measures for these impacts.
fl " ,'•'. (""\'tW .;* "I"'.;!",- ', • ||" ' ;::'; .,i'V.r [', _"! ,! '" ' -.' ' ' ' 'I i : ,' , _ • >:
33 " Types of Impact to Ecosystems
A completed highway project necessarily includes impacts from all of the phases described above.
Genericaily, highway development can be said to affect ecosystems, and their values and functions,
through* me! following stressor processes:
Ecological Impacts of Highways 8 April 1994
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Alteration of topography.
Vegetation removal.
Erosion, sedimentation, and soil compaction.
Dehydration and inundation. •
Acidification, salinization, and wanning.
tOXICIty.
Noise and visual disturbance.
Introduction of exotic species.
Direct mortality from road kills.
These stressor processes can result in the following effects on ecosystems:
Direct mortality of resident species.
Physiological stress and .decreased reproduction.
Disruption of normal behavior and activities.
Segmentation of interbreeding populations.
Modified species interactions and alien species invasions.
Although highway development shares these effects with other human activities that degrade the
natural environment, highways (as well as powerline rignts-of-way and other transportation routes) have
unique impacts associated with their linear form. Within forested landscapes, highways act as concave
corridors, areas that exhibit lower vegetation heights than the surrounding habitat matrix (Gates 1991).
In agricultural and some rangeland landscapes where dense vegetation is encouraged along the roadsides,
highways may act as convex corridors. These highway corridors may function as (1) specialized habitats,
(2) conduits of movement, (3) barriers or filters to movement, or (4) sources of effects on the
surrounding habitats (modified from Forman and Gpdron 1986). Exactly how the corridor wOl function
depends on the condition of the larger landscape, not simply the habitat adjacent to the corridor. For
example, a highway corridor in a forested landscape will function differently than a corridor bordered
by forest, but which exists within a landscape dominated by agricultural land. Highway development is
also unique hi its facilitation of secondary development.
The direct, indirect, and cumulative impacts of highway development can be grouped into three
general categories:
1. Destruction of habitat (resulting in the elimination of certain habitat types and men-
replacement with non-natural uses or with specialized semi-natural habitats)
2. fragmentation of habitat (resulting in the loss of habitat integrity through the creation
of barriers to species and ecological processes).
3. Degradation of habitat (resulting in the loss of habitat integrity through disturbance of
resident species, contamination with pollutants, alteration, of natural processes, and
introduction of exotic species).
Ecological impacts of Highways 9 April 1994
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! ••: 3.2 JL Destruction of Habitats r
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The most direct effect of highway development on ecosystems is the destruction of a natural
habitat through its "conversion" to a transportation land use or "right-of-way"'". Although natural
vegetation may be preserved within the right-of-way, the original natural characteristics of the land are
eliminated within the payed area and adjacent roadsides. The clearing of vegetation (trees, shrubs,
grasses) and accompanying leveling operations (mat destroy the original topography and soil profile) are
the principal changes. In some cases, the natural vegetation may be replanted while hi others different
species are planted and the habitat values modified. In wetland environments, road construction may
require fflmg and Draining operations that destroy wetland habitats. In aquatic environments, flow
alteration (via damming or channelization) may eliminate habitat. Dredging, filling, and draining required
i' SJII"!' I. ''.''I1!: : :"! l;l1 -1',™ '' '""' •• '"'3 " y ; - •-_ ' „>"" *_" T_*Z.V
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b''roadl''constoctSn also" desEby aquatic habitat.
conversion of forested land to
a|ppg the roadway "with grassy or shrubby vegetation. These early successional areas provide additional
habitat for species' such as Brewer's and red-winged blackbirds (Adams and Geis 1981). These and other
birds are likely attracted to suitable nesting, perching, or feeding sites. Interstate rights-of-way have also
%8n P&PJW to, tl'BSf*' sig"ffleant populations of small mammals (constituting 17% of wildlife mortality).
Trapping data indicate that right-of-way habitat and its accompanying edge are attractive not only to
grassland species but also to many less-habitat-specific species. Examples include, in the Southeast— the
eastern harvest mouse, white-footed mouse, and meadow vole; hi the Midwest—the prairie vole; and in
the Northwest— the vagrant shrew, Townsend's vole, and California vole (Adams and Geis 1981).
Although certain species benefit, the creation of homogenous modified early successional environments
negatively "'affect fggionai ecological diversity by replacing complex coevolved systems wim common
species and simplified systems. In the case of .forest environments, this conversion represents a decrease
in the structural diversity. Universally, the removal of vertical habitat structure reduces the diversity of
" species! Staicoiia! d^elfsn^'piovides' more microhabitats (e.g., nest sites) and allows for more complex
species interactions (e.g., avoidance of predation and partitioning of foraging space).
Tn stmiTnary, both the construction of paved roadways and me removal of vegetation from the
right-of-way result hi the destruction of natural environments and the loss of habitats. The impact of
these losses on local and regional ecosystems varies wim the habitats destroyed. Although all habitats
, contribute to ecosystem integrity, those mat are rare .or play critical ecological roles in the landscape can
be designated as "habitats of concern" and given special consideration. A discussion of regional habitats
of concern is available hi the EPA Office of Federal Activities (OFA) report (Soumerland 1993), Habitat
Evaluation: Guidance far the Review of Environmental Impact Assessment Documents.
323. Fragmentation of Habitats
In general, highway development rarely eliminates entire habitat types, but instead destroys part
of a habitat, leaving other areas intact. In most instances mis local habitat destruction is better thought
of as .habitat fragmentation. Such fragmentation is the principal cause of me loss of "area-sensitive"
sgpecies (Harris '1984) and is considered the most serious threat to biological diversity (Wilcox and
Murphy 1985, Harris 1988). For example, fragmentation on a broad geographic scale has been shown
to result in declines of songbird species (Whkcomb et al. 1981). Specifically, studies hi Maryland,
Michigan, and Oregon have shown that me occurrence of most forest-dependent species is correlated with
ill! \' « • ) ,"
-------
forest size, and that contiguous forests of 100 to 300 ac are needed by long-distance, insectivorous,
neotropical migrants, such as flycatchers, vireos, and wood warblers (Terborgh 1992).
The consequences of habitat fragmentation (Hards and Atkins 1990, Hunt et al. 1987) may
include the following:
• Erosion of genetic diversity and amplification of inbreeding (Le., risk to
sedentary species from random variation in demographic and genetic variables
when isolated). .
• .Increased probability of local extinction from small population sizes and reduced
likelihood of reestablishment (because immigration is inhibited by barriers). -
• Extinction of wide-ranging species (e.g., wolves, black bears, panthers,
manatees).
• Loss of interior or area-sensitive species (e.g., sharp-shinned hawk, Cooper's
hawk, Swainson's warbler, red-cockaded woodpecker). .
• Increased abundance of weedy spedes (regionaUy distinct communities give way
to globally homogeneous ones).
As discussed under the destruction of habitat, highway rights-of-way may be converted to a
modified earlier snccessional habitat depending on the width of the corridor. Bom wide and narrow
corridors can act as effective barriers to the movement of anhn^ effectively isolating habitat patches
' and subpopulations. In addition to the effect of distance, wind-funnelling can prevent the migrating and
dispersal of invertebrates and plants across corridors (Sheate and Taylor 1990). The many discontinuities
associated with roadways and traffic also contribute to the barrier effect, principally the break in
microclimate (temperature, humidity, and evaporation), instability of the vegetation (due to mowing and
spraying), vehicle emissions (noise, dust, headlight illuminations, car exhaust, increased salinity in soil,
vegetation, and ditches), and direct road kOls (Mader 1984). In fact, the simple contrast in. habitat
conditions characteristic of edges often acts as barrier to the distribution and dispersal patterns of bom
birds and mammals (Thomas, Maser, and Rodiek 1979).
The most obvious barrier effect is direct mortality of annuals attempting to cross the highway
corridor mat result from collisions with motor vehicles. Millions of animals are killed annually on
highways (Leedy 1975). Road kills may represent a critical mortality factor for large wide-ranging
species mat can often avoid direct impacts of other development activities (e.g., key deer in Florida).
Annual road-killed animals are significantly correlated with average vehicle speed (Case 1978). In an
extensive study of highway impacts on wildlife, Adams and Geis (1981) observed mat 76% of road
wildlife mortality occurred on interstate highways and mat roads appeared to act in a density-dependent
manner, predominantly killing those species attracted to roadways. Species killed in greatest numbers
included meadowlarks, indigo buntings, field sparrows, red-winged and Brewer's blackbirds, deer mice,
several vole species, and rabbits.
Ecological Impacts of Highways n April 1994
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Adains and Geis (1981) also found many species reluctant to cross highways. Shrews are a
disturbance sensitive group that rarely enter rights-of-way; other sensitive species include the golden
mouse, pinon mouse, dusky-footed wood rat, California red-backed vole, and brush mouse. In June
•"surveys, salamanders did not readily cross interstate highways, and were not attracted to right-of-way
habitat/ Turtles, frogs and toads, and snakes were common road kills. Foxes, raccoons, skunks, and
Coyotes 'appe^j[^0 snun interstate rights-of-way even though a substantial small mammal food resource
is available mere. Elk tended to avoid habitat adjacent to interstates and forest roads. Roads did not act
as a critical barrier to. deer, but roadside hunting and dogs affected deer distribution.
Early fSd data from Oxley et al. (l§74) suggested that smaU forest mammals were reluctant to
yenmre daE road surfaces where the distance between forest margins exceeded 20 m. Burnett (1992)
Mader (1984) extended the roadway barrier effect to wandering insects by determining that forest carabid
ivoli "imstaHe habitat conditions. He also demonstrated that mice species will adjust their
^territory boundaries to avoid roadway corridors.
i™ jj,11 !,', ' "*;;,! ....... ;, ' " "i"1 l'lil!±l! ', ,11 ........ "''!'!!!" " ........ „,,' ";,; ',;, , ,' ','" ......... ,,„ „ , , ' ................ ...... , ,,ji " ,,, , , ,„ ............... , ...... ,'
J ......... ™; • |J "' 'J m \"'r "n _";[,, !„",',,, ...... , ', i ,, ..... "" , " I ,!|,' i !,,!„, ,„' , „ '! ' ' ,' " , ,",' |'» |p ' ^ ........ ^ " |'|i|||- ^ ^ "»j ..... ^ " | "• ^ J™ '^ '" ^ • |||1'" 'i""m"\"' : ...... ^a' ; ' ^ """ '""-^ ,,",' ' " , 'j,!, , , ..... ' *|, ,,, ' ' ,'„;",,
Because the majority of species respond to corridors as an activity filter, reducing activity with
?liStance"to ......... me ........ coSIbr; ...... changes "in corridor vegetation can reduce me effectiveness ..of me fitor by.
softening me edge or creating "pores". Edge permeability increases as the contrast between adjacent
j^g-^^.™^-^..^^ Godron 1981). even smaU changes hi edge permeability may have large
impacts on animal movement across patch boundaries (Buechner 1987).
Bom jo'JJ^i and rtonforested environments can be disrupted by fragmentation due to highway
consiruction. However, the dense canopy structure of certain shrublands may be most severely impacted
by fragmentation. An example is the fragmenting of pocosin wetlands and uplands in me Southeast.
Because of the scale at which many pocosin inhabitants move, highway development can effectively
isolate much of me pbcosm fauna.
i.'.....,.
Barrier effects are not limited to terrestrial habitats and may have extreme consequences for
migratory fish species where highways have diverted streams or .constructed impassable culverts.
Upstream passage is a particular problem for anadromous fish such as salmon and shad that must travel
;long"(tistances; to reach natal spawning grounds. Passage of anadromous fish at large dams has received
consWerable attention tough research and the construction of fish ladders and lifts (Bell 1991).
Ironically, culvert barriers associated with highways often occur at the end of spawning runs just below
Spawnmg grounds, thereby negating passage achievements downstream. Even small barriers can act as
blockages near the end of the spawning run when me passage capabilities of anadromous fish species
may decline. In addition, resident fish can be adversely affected by stream blockages, as in the case of
Hout;-pjke, and grayling mat migrate upstream and downstream during their lifecycle in search of habitats
for spawning, rearing,-or shelter.
I III i i i iiiiin i i MI H'vi .,:>,, H':r i, 'f v r ; i,J,hi,jii "i ;:\'\",\ h "iiiini iLrjiin,,1! .""fiin,, , 'i|i*i," •• !M, i •!' . !, 'iHWviiHiK ,
The success of fish passage is principally dependent on the swimming ability of the fish and the
hydraulic conditions of the modified stream segment.(Baker and Votapka 1990). Swimming ability varies
with the size and species of fish (Bell 1991). Passage problems include:
.
• Vertical barriers.
• Water velocities that exceed fish swimming ability over prescribed distances.
i iii
I II llll 111 II I III II I
Ecological impacts of Highways 12 April 1994
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• Low water depth. .
* ' Icing and debris blockages.
In addition, culverts can limit passage through changes in water temperature, water pollution, and
darkness that conflict with behavioral requirements of the fish (Baker and Votapka 1990). Another
important factor is the relation of these modifications to annual hydrographic and seasonal time of fish
passage for all species of concern. For example, even closely related species may have different
spawning times (e.g., brown trout spawn in the fall in Montana where rainbow trout spawn in the spring).
3.2.3 Degradation of Habitats .
Degradation of habitats specifically refers to a decrease in the health or ecological integrity of the
"intact" habitat. In the case of highway development, mis degradation is closely associated with
fragmentation and. what many researchers call the "edge effect". This edge effect can be viewed as a
reduction in habitat integrity at the boundary of a highway corridor caused by disturbance, contamination,
or other degrading factors mat extend into the natural habitat. In addition to direct toxichy and
behavioral effects on resident organisms, this degradation includes the alteration of natural processes such
as water flow, fire regime, and species interactions. Biological invaders are a particular problem along
roadway corridors that can seriously degrade natural systems by modifying species interactions.
1 Sheate and Taylor (1990) state that the vulnerability of woodlands to degradation from motorway
impacts is dependent upon the size of the woodland; mat small woodlands will tend to be susceptible to
physical impacts, whereas larger ones will be more vulnerable to qualitative change. Direct edge effects
on ulterior trees include temperature effects of aspect, wind-funnelling "jet" effects, potential root
starvation from lowered water tables adjacent to cuttings, increases in evapotranspiration, and
susceptibility to wind-blow.
Effects of disturbance associated with forest edges has been well documented for many mammal
and bird species. In particular, large, mobile carnivores such as mountain lions and grizzly bears require
extensive tracts of undisturbed habitat (Wilcove and May 1986). Ferris (1979) found mat bay-breasted
warblers, blackbumian warblers, blue jays, and winter wrens avoided forest edges along highways and
suggested mat noise created by vehicular traffic, rather man vegetation differences, render the forest edge
unsuitable for breeding. Recent research indicates mat increased edge effects result in less "secure"
habitat for nesting birds (Temple 1986) and a much higher incidence of nest predation and parasitism
(Wilcove 1985, Laudenslayer 1986).
Because detrimental edge effects may extend 600 m into a forest, Wilcove (1985) concludes mat
more than 100 ha of contiguous forest are required for forest-interior habitat. Van Der Zande (1980)
found empirical support for Veen's (1973) conclusion that disturbance effects greatly exceed right-of-way
widths and may extend 500 to 600 m from quiet rural roads and 1600 to 1800 m from busy highways
in the Netherlands. Terborgh (1992) estimates mat areas as large as 15,000 ha may be needed to provide
safe havens from nest parasites such as brown-headed cowbirds that fly up to 7 km in search of host
nests.
Ecological Impacts of Highways 13 April 1994
-------
i s
.ti!'|: .I'll' iii il'nlii n: .'it*
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::.',' :' : Pollution
• rfn
.'iChemical contamhiation related to highway development results from ah- or water pollution during
construction and operation and can be a significant cause of habitat degradation, especially in aquatic
environments. Although'toxic effects may be the most severe, conventional pollutants and other effects
s m|"33st in grei^^fre^eng^^ffl^^extent. For example, soils are degraded through erosion or sofl
compaction while elevated temperatures may damage adjacent vegetation. Rivers amji streams can be
degraded by siltatipn and salinization from deicing activities. In general, highway construction parallel
i" to streams provides greater opportunities 'for adverse effects man perpendicular arrangements mat result
in stream crossings. Underground water sources and meir contributions to ecosystem integrity can be
degraded by runoff and hazardous material spills that contaminate aquifers. Where highways cross
permeable sandstone and limestone, they introduce the possibility of fractures mat can contaminate or
111 ..... ;
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v Disruption of natural processes
In addition to disturbance and contamhiation effects, highway development can seriously degrade
habitat through the alteration of ecological processes; These processes include natural hydrology, fire
regimes, animal migration patterns, and competitor and predator-prey relationships (including the effect
of exotic species). By creating barriers to natural water flow, highways can degrade aquatic systems,
wetlands, and terrestrial environments. Natural stream flows are usually maintained by the construction
of bridges or culverts, although barrier effects and local losses of natural aquatic habitat may result.
Wetlands are more problematic. Natural drainage patterns are easily disrupted in the saturated soils
characteristic of wetlands (McLeese and Whiteside 1977). If a surface highway runs perpendicular to
the path of water transport, even precise construction of drains and ehanneig may not prevent sofl
compaction from lowering the water table and eventually draining downfiow wetlands (Sheridan 1988).
On the upflow side, ponded conditions can lead to tree death.
ill,: i
iiP iii IV
The adverse effects of road building on natural hydrological patterns are especially deleterious
for riparian habitats. In arid environments, riparian areas make up 80% of available wildlife habitat and
support the majority of endangered species (Johnson 1989). The maintenance of natural flow patterns
in perennial and intermittent streams is critical to these unique habitats. Impacts on riparian areas from
highway development include the following (Terrene Institute 1993):
(fflff
Ecological Impacts of Highways
14
April 1994
-------
• Acceleration of runoff, increasing flood peaks, erosion, and downstream sedimentation.
• Dewatering of riparian areas as gullies are created by concentrated flows.
• Decreased volume and duration of base flows, causing streams (including former
perennial streams) to dry up earlier in the year.
• Shifts at plant composition from riparian species to drought-tolerant invaders or upland
. species.
• Loss of habitat for riparian-dependent wildlife species.
Suppression of fire is a common impact on virtually all humaoHise lands. Land use practices are
the major factor suppression natural fire regimes, although highways may act as unnatural fire breaks in
some areas. Many plant communities require a natural periodicity and intensity of fires to maintain men*
typical species composition. Where highways combine with land use practices to reduce the frequency
of fires, the accumulation of flammable material may result in less frequent, intense fires mat degrade
native habitats.
Natural animal migration patterns, as well as the relationships among competitors and between
predators and prey, are an essential part of ecosystem integrity. While some species (such as birds of
prey) may benefit from access to a new food source, many less adaptable species are adversely affected
by the presence of new competitors or predators. The greatest danger to these processes is posed by the
invasion of non-native, or exotic, species. Highways can act as movement corridors for exotic animals,
or even provide intentional or unintentional transport in vehicles. Non-native weeds are a particular
problem for highway rights-of-way where the inevitable transport by wind and tires is often exacerbated
by the intentional planting of exotics. The magnitude of the problem has prompted an interagency white
paper for the Federal Coordinating Committee on Science, Engineering, and Technology (FCCSET) mat
calls for mamtaming a Federal Interdepartmental Committee for Management of Weeds (FICMW). The
goals of this committee would be to develop a Federal Land Weed Management Policy that would
strengthen Federal Agency Manuals, review current agency policies for effectiveness, contribute to
national legislative proposals, and create prioritized coordinated treatment efforts (Anonymous 1993).
3.2.4 Cumulative Impacts
As mentioned earlier, .highway development differs from other degrading activities in the
proportion of its effects that can be attributed to cumulative impacts. The effects of highway development
accumulate when different road segments or highway systems overlap in space or time. The principal
effect of the cumulative impacts of highway development is increased habitat fragmentation. As habitat
patches become smaller and more isolated, species mat depend on them become less able to find mem
and to maintain populations in mem. The National Research Council (1986) described these decremental
effects as "nibbling". The combined effect of these cumulative impacts may exceed the sum of each
impact or even create a qualitatively different effect on the ecosystem. For example, individual highway
projects may not affect forest-interior bird species, but when several projects provide enough habitat to
sustain brown-headed cowbirds, nest parasitism may completely eliminate forest-interior species from that
habitat.
Ecological Impacts of Highways 15 April 1994
-------
urn-*.?r"'f i":
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jjjggg g^jg^jjg jj^y ^e augmented, or even overwhelmed, by secondary development, i.e., the land
s'tb industrial or residential use that often accompany road building. Capacity improvements,
additional interchanges, and new location construction have greater potential for secondary development
than upgrades of existing faculties. Creating new access to undeveloped locations can have the greatest
impact, if other economic conditions are favorable. In fact, demand for increased capacity often creates
a highway that, in turn, increases the influx of secondary development and recreation, thus creating
demand for yet more increased capacity (Sheate and Taylor 1990). It is important to note that the
promotion of economic development in depressed areas through infrastructure improvement is often the
purpose of a highway project.
' " " "" I '
The FHWA recognized the importance of considering cumulative impacts in its 1992 Position
1. iLihi :-ii;" jiri > i Paper on secondary and cumulative Impact assessment. In mis guidance, FHWA proposed mat
1 ;!l!!|:|!<:'!ll<;: arj Ijj^jjfi -"i enviromnenial assessment focus on me functional rdationships of rescue larger systems because
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environmental studies that examine only the immediate influence of an isolated project
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4. Ecosystem Approaches in Highway Development
The emerging disciplines of landscape ecology and ecosystem management are providing new
insights into potential approaches for assessing ecological impacts, including those from highway
development. Although mis research has not yet produced definitive methods for ecological impact
assessment, some general principles for ecosystem (or biodiversity) conservation are becoming accepted.
The recent report of the CEQ, Incorporating Biodiversity Considerations into Environmental Impact
Analysis Under tfie National Environmental Policy Act (1993), provides the following eleven general
principals of ecosystem management:
1. Take a "big picture" or ecosystem view.
• 2. Protect communities and ecosystems.
3. 'Minimize fragmentation. •.
Promote the natural pattern and connectivity of habitats.
4. Promote native species.
Avoid introducing non-native species. -
5. Protect rare and ecologically important species. • .
6. Protect unique or sensitive environments.
7. Maintain or mimic natural .ecosystem processes.
8. Maintain or mimic naturally occurring structural diversity.
9. Protect genetic diversity.
10. Restore ecosystems, communities, and species.
11. Monitor for biodiversity impacts.
Acknowledge uncertainty.
Be flexible. -
4.1 Categories of Highway Development
Each of these principles has implications for assessment and mitigation of ecological impacts
caused by highway" development. However, the applicability of each principle wfll vary with the
conditions surrounding individual highway projects. For example, fragmentation will likely be less
important in highly urbanized settings. Therefore, it is useful to consider assessment of the ecological
impacts of four distinct categories of highway projects:
• Urban
• Suburban
Ecological Impacts of Highways 17 • April 1994
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II," II
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Rural
Wildland.
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way development in urban settings may have little impact on sensitive habitats, or natural
of any land. Often, road construction affects only previously developed areas and may not
have even indirect effects on natural habitats.. However, in some instances, urban highway construction
will have substantial impacts on natural water bodies or other habitats existing within the urban matrix.
Destruction of these habitats can occur if new roadways are built on any of me few remaining natural
areas. Fragmentation is of lesser" importance, because natural- habitats are usually already isolated by
urban development. The principal impact of highway development in the urban setting is habitat
degradation. River habitats running through urban areas may receive greater loadings of pollutants from
runoff during construction or normal operation of the highway. Other impacts include adverse effects
on urban trees and wildlife. Direct mortality of certain species may increase through road kills, and air"
pollution may damage terrestrial vegetation. Deposition of airborne contaminants may also degrade
aquatic vegetation and fisheries. Because of the extensive development hi urban areas, cumulative and
secondary development impacts from highway development are usually minor.
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As hi urban areas, highway development hi suburban settings can still adversely affect vegetation
and wildlife mat are well adapted to human-altered habitats. Perhaps more important are the impacts on
species less adapted to urban conditions, which try to move among pockets of natural habitat within the
suburban matrix. For this reason, fragmentation can have a severe impact on suburban habitat. While
high levels of ecosystem functioning are rare in urban environments, suburban areas may maintain
substantial habitat integrity if a considerable undeveloped area remains and natural habitats are connected
in a planned or de facto system of natural areas or greenways. Creation of additional highways can sever
remaining migration corridors and further isolate species. Pollution from air emissions and roadway
runoff are important, as are the higher levels of roadkflls. The introduction of weedy or pest species is
a special problem in suburban areas, where native species are surviving in unnaturally small habitat areas.
Cumulative nnpacts of highway development hi suburban areas can be severe, and secondary development
often follows road construction and other infrastmcture improvements in this high growth setting.
4.13 Rural
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1,1 Rural areas are characterized by less land conversion to residential, commercial, and industrial
uses. Additional highway development may have a greater proportional impact on rural areas man on
suburban or urban areas,' although this is reduced in heavily agricultural regions. In most rural
environments, significant areas of natural habitats remain.. Although they may be fragmented by
cultivated fields, grazing pastures, and commercial timber lands, natural habitats are more likely to be
impacted by highway development hi rural settings man in suburban or urban ones. Except hi areas of
monotypic cropland and timberland, rural areas contain a greater variety of species man do urban and
suburban settings. Many rare and regionally important species may be at risk. Destruction and
degradation of these habitats usually accompany any highway development mat is not confined to existing
agricultural hind. Degradation of hydrological processes, as well as nutrient and energy cycling functions
||e more important hi rural environments. Fragmentation is perhaps the most important impact, serving
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to sever migration routes that continued across agricultural lands and other undeveloped regions.
Cumulative impacts may be a major factor in rural environments where highway development is provided
as a stimulus to secondary development and ultimately local economic enhancement.
4.1.4 Wildland
WHdlands are landscapes largely undisturbed by human activity. Highway development in
wildland areas differs substantially from mat in rural, suburban, and urban settings. Rather man
contributing to the cumulative impacts of a suite of development activities, highways are often the only
major impact on wildland habitats. Where secondary development does follow highway development (as
in second home development), alterations to the natural habitat are almost always severe. The intricate
ecosystems found in wildlands possess far more sensitive species and maintain a larger suite of natural
functions man in previously developed areas. In addition to water, nutrient, and energy cycling, fire
regimes in wildlands can be disrupted by highway development. Destruction of habitat (where virtually
all areas are sensitive), fragmentation of habitat (where contiguous natural areas are the rule), and
degradation of habitat (where species are more sensitive to disturbances such as noise) are all important
factors in wildlands.
4.2 Approaches and Ecosystem Protection Goals
Hie following table illustrates approaches to attaining ecosystem protection goals within each of
the four different categories of highway development With the exception of urban environments, most
of the goals are applicable to virtually all highway development projects. The specific approaches may
differ among categories, and are not limited to the examples given below.
Ecological Impacts of Highways 19 April 1994
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5. Evaluation of Ecological Impacts
FHWA mandates clearly require consideration of direct, cumulative, and secondary highway impacts
on ecosystems. This can be accomplished by using the ecosystem approach presented in the CEQ
biodiversity document (1993) and discussed in this report. The steps required for habitat impact
assessment are basically those of traditional FHWA assessment with me incorporation of a landscape
perspective and the identification of specific ecosystem endpomts. In addition, many of the same
analytical tools currently used in environment assessment can be modified to include me improved land
pattern analysis that can be achieved by using geographic information system (GIS) technology.
Evaluation of ecological impacts from highway development requires both scoping and analysis.
Included in scoping are the determination of the appropriate scale of analysis, the setting of specific
ecosystem goals or endpomts, and the gathering of information. The analysis phase involves
consideration of the impacts on individual ecosystem endpomts and quantification of specific effects where
possible.
5.1 Determining the Appropriate Scale
Scale is a central issue in the ecosystem approach. The appropriate boundary for highway impacts
is one mat ensures adequate consideration of all resources that are potentially subject to non-trivial
impacts. For some resources, mat boundary can be very large. Hydrologic and atmospheric transport
of emissions and surface runoff can affect distant reaches of the watershed. In addition, barriers to
migration may affect populations on the regional scale. At the other end of the spectrum, habitat
protection also includes identifying and avoiding small sensitive areas, such as rare plant communities.
Determining relevant boundaries for assessment is guided by informed judgment, based on the resources
potentially affected by an action and its predicted impacts. Although in some cases ecological impacts
may be limited to the highway corridor (e.g., 300 feet in width), impacts wfll often extend to the
watershed or ecological region (via indirect and cumulative impacts of additional road construction and
secondary development). .
Separate jurisdictions and competing missions may make it initially more difficult for federal and state
highway departments to engage hi cooperative ecosystem management with other agencies. However,
clear benefits are to be gamed from sharing expertise, technical capabilities, and information; such
sharing will lead to unproved environmental decisionmakmg. Highway agencies need not sponsor
regional ecosystem planning efforts to benefit from them, however inclusion of transportation planning
into regional land use planning should be done as early hi the process as possible. Early consideration
of ecological issues in the highway development process may be the most important factor hi ensuring
the environmental success of projects.
5.2 Establishing Ecosystem Goals and Endpoints
In order to consider ecological impacts from highway development, it is important to establish
concrete operational goals for the maintenance of ecosystem integrity. Although the general goal of
ecosystem protection is to protect or restore the diversity of natural organisms and natural ecosystem
processes, mere is no one objective mat will apply to all situations. Because they may represent
important social choices, the establishment of goals and objectives must be undertaken with care. For
Ecological Impacts of Highways 21 April 1994
-------
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example, tiie federal and state highway agencies should involve not only the public, but other agencies
g*™,,,^,_^,,.^__^__^u^ £or managing me affected natural resources. This will help identify those
instances where other parties have developed operational goals and objectives relevant to habitat
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, 1 ^_r_i_i[|BirJ "for the protection of ecosystems, and biodiversity," can be developed by applying
the relevant guiding principles outlined in this report For example, measures to minimize landscape
fragmentation, or to preserve old growth forests, can be assumed to benefit biodiversity without
quantifying the specific biodiversity goal to be 'achieved. Highway agencies may have to limit their
biodiversity objectives to such general guidelines if more specific objectives cannot be identified.
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Ultimately, ecosystem endpoints must be selected based on biodiversity conservation principles.
These endpbints should be quantifiable environmental attributes for which a baseline can be established .
and subsequent monitoring done. A wide variety of objectives and measurement approaches are
potentially useful. For example, Noss (1990) has delineated a hierarchical approach that incorporates
elements of ecosystem composition, structure, and functioning at four levels of organization: regional
landscape, communiry-ecosystem, population-species, and genetic. Incorporation of these individual
indicators, or endpoints, will depend on the ecological resources present, the impacts involved, and the
available hrfbrmation. v ';
r The following table is an attempt to define categories of ecosystem endpoints that should be used hi
environmental assessments of highway development. One or more categories have been defined for each
of five general principles of ecosystem protection (derived from the original 11 principles). Specific
endpoints for each category are described hi the next section.
Table 2. Ecosystem Endpoints Associated with Ecosystem Protection Goals for Use in
"* "'*" Environmental Assessment of Highway Development
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Focns on ecosystems. Address die needs of the
region.
Protect sensitive communities and ecosystems.
M ftTntani native diversity and natural processes.
V
Protect sensitive species.
Minimize fragmentation.
Ecosystem Endpoints
• Consistency with regional plans.
• Integrity of regional ecosystem.
• Area of sensitive communities.
• Status of sensitive communities.
• Native species diversity.
• Native structural habitat diversity.
• Status of hydrology, nutrient and energy
cycling, fire regime, and keystone species
interactions.
• Number of sensitive species.
• Status of sensitive species populations.
• Habitat connectivity.
• Habitat patch distribution.
• Number of contiguous habitat areas affected.
I I HI
Ecological Impacts of Highways
22
April 1994
-------
5.2.1 Ecosystem Endpoints
* •
The categories of ecosystem endpoints defined in the table may be thought of as "assessment
endpoints" in the terminology of Suter (1990), and the more specific indicators discussed below as
"measurement endpoints." The designation of sensitive habitats or species is critical to endpoint selection.
In the context of impact assessment, the term "sensitive" applies to bom ecologically valuable species and
habitat, and to those vulnerable to impact. Rarity is often a good indicator of vulnerability, but the
following characteristics are also indicative of vulnerability:
• species requiring high survival rates rather man high reproduction rates may be more at risk
(given that impact is on survival rather than on nesting or other reproductive parameters) (Mertz
1971).
• species whose intrinsic rates of increase fluctuate greatly are most likely to go extinct, even with
high average population sizes and high birth rates (Goodman 1987).
• communities with vulnerable keystone (sensu Paine 1969) predators or mutualists may be more
vulnerable; similarly, the presence of exotic species may dramatically increase the vulnerability
of communities. • . . •
As discussed previously, the selection of specific ecosystem endpoints, or indicators, is dependent on
the resources of concern and the data available. In addition to Noss's (1990) comprehensive list of
biodiversity indicator types, EPA's Environmental Monitoring and Assessment Program (EMAP) is
developing a wide range of specific indicators of environmental condition (Hunsaker and Carpenter 1990).
These indicators range from population abundances to community indices (e.g., Karr's Index of Biotic
Integrity for fish communities) to landscape-level indicators such as the following:
Abundance or density of key physical features and structural elements. .
Habitat proportion (cover types). .
Patch size and perimeter-to-area ratio.
Fractal dimension (amount of edge).
Contagion or habitat patchiness.
Research into ecological indicators is continuing and promises to provide a diverse toolbox of methods
for determining environmental change and identifying habitat impacts. As new indicators are developed,
they can be incorporated into analyses focusing on the following categories of ecosystem endpoints:
Consistency with regional plans.
CEQ (1981) guidance on the "forty most asked questions" (46 Federal Register 18026) states that
environmental assessments must identify and evaluate conflicts with land use plans (all formally adopted
documents for land use planning, zoning and related regulatory requirements, even if proposed).
Placement of the highway corridor may conflict with land uses assigned to specific areas hi regional
plans. Each such instance should be identified and discussed in detail.
Ecological Impacts of Highways 23 April 1994
-------
Integrity of Iregional ecosystem. •
Once the boundary of the appropriate regional ecosystem is identified (e.g., the Greater Yellowstone area
or the Chesapeake Bay Watershed) the impact'of the project on this ecosystem should be identified and
discussed in at least qualitative terms.
!'"' •"' "' '. ' ",„ '.. ' • | ' ' ' ' ....
Area of sensitive communities.
Distinct local ecosystems and vegetative communities should be identified; where these h?hfrats are
natural or ecological significant it should be so indicated. The areal extent of each community should
be determined and the absolute and relative decrease in area (acres) calculated for highway land
conversion impacts. As an example, sensitive habitats in the southeastern coastal plain include streams
and rivers, riparian areas, wetlands, bottomland hardwoods, scrub habitat, old-growth pine forest, and
contiguous upland hardwood forest. These and habitats of concern for other regions are described in
Habitat Evaluation: Guidance for the Review of Environmental Impact Assessment Documents
(Southerland 1993).
Status of sensitiv6_communities
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In addition to determining areal impacts to distinct local ecosystems and vegetative communities, adverse
effects to remaining habitat areas should be determined. These include changes in the serai stage, loss
of habitat features (e.g., caves, cliffs, slopes, springs, and seeps), and decreased community vigor
through, contaminant toxichy (e.g., needle loss in conifer stands caused by acid precipitation).
Native species diversity.
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Single species diversity indices have often been used ta justify the creation of additional edge habitat.
However, these increases hi diversity simply reflect the replacement of local organisms with species
adapted to disturbed or edge habitats. The invading species are usually common species mat do not
contribute to regional biodiversity. Measures of diversity should be limits to native species adapted to
the intact natural habitat of the area. Numerical indices that use multiple metrics (e.g., Karr's Index of
Biotic Integrity) are often preferable to single metrics such as species richness.
sttnetaral habitat diversity.
Creation of modified roadside areas, stream channels, and wetlands usually results in the simplification
of structural diversity, including the loss of critical microhabitats (e.g., snags and down material). These
cnangess&bulffbeidentifiedart "quaiiitmledLThe UlS.Fish and Wildlife Service Habitat Evaluation
Procedures (HEP) provides a method for describing habitat features important to wildlife (USDOI1980).
Status of hydrology, nutrient and energy cycling, fire regime, and keystone species interactions.
Highway development frequently alters surface and subsurface water flows. Changes in rates and total
volumes should be quantified and their effects on nutrient and energy cycling described. Quantitative
systems cycling studies may be possible hi some instances. Disruption of natural fire regimes should be
described. Effects on ecological important species, such as top predators, major migratory populations,
Ecological Impacts of Highways
1 liillfl !j> '" Jill!1 «iiri „,, ",H!" ; I'1 """ii .u'lit , ,:!' .n>
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essential prey, populations, and dominant plant species, should be evaluation in terms of ecosystem
impacts.' "
Number of sensitive species.
Both rare and. ecologically important species should be identified and counted. This include federal and
state endangered and threatened species, species of special concern, migratory species, as well as keystone
ecological species (i.e., those that control species composition of communities through strong predatory,
competitive, or symbiotic relationships). The number of exotic species invading the area due to highway
development should be included as a negative factor in the assessment
Status of sensitive species populations.
In addition to the number of different species, the demographic status of each sensitive species (including
genetic composition) should be evaluated. Changes in age class distribution, sex ratios, and
subpopuiation migration can be measured.
Habitat connectivity.
Fragmentation caused by highway development results hi reduced connectivity of habitats. Connectivity
of single habitat types, or general classifications such as contiguous forest, can be measured using pattern
analysis (e.g., fractal geometry) and GIS techniques.
Habitat patch distribution. •
N
Another measure of me fragmentation of the landscape is habitat patch distribution. The composition of
different habitat types and habitat sizes may be as important as connectivity for species movement and
maintenance of metapopulations. Again using GIS techniques, quantitative measures of patch distribution
can be obtained.
Number of contiguous habitat areas affected.
A simpler method of measuring fragmentation is to calculate the number of contiguous habitat areas
affected by highway development Once habitat block sizes of interest (e.g., forest stands) are selected,
the number and proportion affected can be determined.
53 Gathering Ecosystem Information
Successful application of an ecosystem approach to evaluating ecological impacts requires sufficient
ecological information. It is important mat information be collected on the distribution and status of the
ecosystems or habitats that could be impacted by the proposed action to establish a baseline of existing
conditions. Assessment of potential impacts at the ecosystem level will aid in me protection of the
majority of the animals, plants, and microorganisms. Information on species populations and
communities that are rare, sensitive, or otherwise in need of special protection (e.g., small, endemic
populations confined to localized areas) is essential as well.
Ecological Impacts of Highways 25 April 1994
-------
ill
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begin by assembling mformation from existing sources. The recently mstituted
Biological Survey (Larson 1993) should improve access to biodiversity mformation, assess
existing information, and improve and standardize information management. Many federal and state
agencies have already developed inventories of the distribution of biota and the ecological conditions hi
areas under men: jurisdiction. The following are several potentially useful sources of ecological
information.
National Biological Survey (202-208-3733).
. Network (703-841-5300).
Resource Agency Management Hans.
Regional Land Use Plans (such as Coastal Zone Management Plans).
Local Zoning and Growth Plans.
Detailed discussions of the information available in the state Natural Heritage Programs, the Gap Analysis
program of the U.S. Fish and Wfldlife Service, state biodiversity inventories, and the cooperative multi-
state Fish and Wildlife Information Exchange are available in Incorporating Biodiversity Considerations
Into Environmental Impact Analysis Under the National Environmental Policy Act (CEQ 1993).
5.4 Analysis of Impacts
Once the necessary background information has been obtained, the potential direct, indirect, and
cumulative hnpacts of highway development on ecosystems ..... can be determined. This task requires the
' :: careful evaluation of the effects of the proposed action and each ...... alternative on attaining ecosystem goals
and objectives. Ecological analyses should consider bom the factors causing the destruction,
fragmentation!, and degradation of habitats and the general principles for ecosystem protection. A wide
range of techniques can be used to evaluate these ecological hnpacts, including checklists, matrices,
mathematical,models, and cartographic displays. No one technique is suitable for all situations, although
geographical analysis is of special importance hi evaluating ecological hnpacts..
In addition to direct effects, CEQ guidance requires that indirect effects be considered:
"EIS must identify all me indirect effects mat are known, and make a good fahh effort to explain the
effects that are not known but are "reasonably foreseeable." (NEPA Section 1508.8(b)). The agency
has tine responsibility to make an informed judgment, and to estimate future hnpacts on mat basis,
especially if trends are ascertainable." .
Highway agencies seeking to consider ecological hnpacts hi men* project-level environmental analyses
must address the same problems faced in other cumulative impact analyses. A basic problem is the
disparity between administrative and ecological boundaries, that is, differences between the scope of the
project decision and the scale of potential hnpacts in both time and space: There are also difficulties hi
„ ___.,,:_ etions on the same resource, and the additive or synergistic effects of multiple
stresses. The use of an ecosystem approach can help address mis issue (see section 5.5).
ml
i in
Ecological Impacts of Highways
26
April 1994
-------
5.4.1 Analytical Approach
* • .
As described in Habitat Evaluation: Guidance for the Review of Environmental Impact Assessment
Documents (Southerland 1993), die following considerations should be central to any process of ecological
impact evaluation:
• Apply an ecosystem-level perspective that considers the full range of interactions among
ecological components. - .
• Assess the cumulative effects that arise from the additive and synergistic impacts of several
degrading activities occurring over time or space.
• Analyze the true effectiveness of mitigation measures hi conserving natural habitats and their
ecological values.
Traditionally, environmental assessments have focused on the following subject areas related to
ecological resources:
Geological Resources .
Noise .
Air Quality .
Water Quality .
Aquatic Environments
Terrestrial Environments
Endangered Species
Wetlands
Designated Natural Areas. '• •
The consideration of aquatic and terrestrial environments has principally focused on economically or
recreationally important species of fish and wildlife, in some cases, these environments have been
subdivided into land use or vegetation based classes. Rarely, however, have the variety of natural
habitats hi project areas been accorded the attention given to wetlands or designated natural areas (e.g.,
parks, wild and scenic rivers, and recreation areas). By definition, an ecosystem approach to the
evaluation of ecological impacts from highway development will consider all habitats in terms of their
ecological importance, and therefore not exclude important environments that do not nave official
designations. Similarly, this approach requires consideration of the full range of species of ecological
importance, not only listed endangered and threatened species.
The Habitat Evaluation report (Southerland 1993) provides useful information on the status and trends
of habitats, and the- likely habitats of concern, in each region of the United States. A review of mat
report and related material can facilitate, the identification of sensitive habitats and .other ecological
resources. Subsequently, the functions and values of the habitats and resources of concern should be
characterized by selected ecosystem endpoints as discussed hi the previous sections. Lastly, the impacts
to these impacts are analyzed. In summary, the following three basic steps can be used to incorporate
landscape-scale considerations into both regional-level and site-level environmental assessments of
highway development-
Ecological Impacts of Highways - 27 April 1994
-------
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*' *"'"' • '>!i l!":" "'"! |l ! f '!"t''-- ""*t'' ' characten^o" of "habitats1 in terms "of" g^gg^-al ' yafu'e^ -^y fungous.
Step 3. Comparative methods for quantifying different degrees of impact to these habitats.
5.42 Classification and Mapping of Habitats
There are two principal systems for classifying natural resources: taxonomic ecosystem classification
and regidnalization. Taxonomic classification systems attempt to develop definitions for different
ecosystem types, irrespective of their location (Pfister and Arno 1980). This approach is similar to the
traditional classification techniques of species taxonomy and uses a dichotomous key rather than a map.
Regionalization of ecological resources is a map-based approach mat defines geographical areas of
similarity based on 'ecbsys£eniisj orecosyslem^etennining factors.
Robert Baflej of me US. Forest Service and James Omernik of me EPA Environmental Research
Laboratory m Corvallis, OR have developed comparable, but conceptually different, ecoregion maps of
the conterminous United States. Bailey's (1980) map is hierarchical, drawing on different factors for
delineating regions at different levels (e.g., Divisions versus Provinces). His classifications are
principally "climate driven, "but"use; soils, landform, and vegetation at successive levels. Omernik (1987)
uses; " " ' ' ----"--*-'-* 1~-"' : J rj"cc -*•——
including 'venation, hydrology, soils, etc. Omernik's maps have been refined in many states to provide
finer resolution for assessing water resource quality, while the U.S. Forest Service is incorporating local
scale ecoregions into Bailey's classification to facilitate forest management.
; ' : .", \ ''•'•
On the relatively fine scale of individual highway projects, vegetation is still the best indicator of
ecosystem type. However, atonal areas (such a riparian zones) are still poorly represented hi vegetation-
based dassificatipnsJ ESchler's (1964) potential natural vegetation (PNV) units is the only organized
description of major above-ground terrestrial ecosystem diversity mat describes the entire United' States
in reasonable detail (Department of Agriculture, 1978), although NASA and cooperating agencies are
developing new vegetation maps from remote sensing data (Janetos, personal communication). In terms
of ecosystem classifications, the new EMAP initiative at EPA is developing a classification of ecosystem
types for each of their major natural systems, including those for forests (developed by the Society of
Foresters) and for deserts and grasslands (developed by the Society of Range Management). In addition,
statewide natural community classifications have now been completed for each state Natural Heritage
program (Larry Master, The Nature Conservancy, personal communication). There is now good
agreement among state classifications on a regional basis, resulting in about 150 to 300 ecosystem types
per state. More general vegetation types are in use by the natural resource agencies and range from
designations such as oak-hickory and spruce-fir associations to simple hardwood forest, conifer forest,
and rangeland categories.
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Given lie advancement of mese efforts, and me many sophisticated habitat classification programs
at local levels, it is now reasonable to expect a good delineation of habitat types and areas.for major
highway development projects. Analysis of these data require graphic overlay capabilities mat are greatly
enhanced by the use of GIS.
m i
Ecological Impacts of Highways 28 . April 1994
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GIS — Geographic Information Systems
A geographic information system (GIS) is a collection of computer hardware, software, and
geographic data that can capture, store, integrate, edit, retrieve, manipulate, analyze, synthesize and
output all forms of geographically referenced information. GIS approaches using remote sensing and
existing data, such as U.S. Geological Survey quad sheets, are also being used in states to develop
statewide land use maps for planning (Turner 1990). Many more examples of GIS for planning are
occurring on local scales as its power for determining spatial patterns is realized. GIS can be used to
analyze the spatial relationships between species ranges and land use patterns, and to identify adequate
buffer areas and potential habitat corridors for the maintenance of ecosystem integrity. For ecological
evaluation, mapping of individual habitat areas is essential. Only through GIS or other graphical methods
can the areas of habitat impacted and the changes in landscape patterns be quantified.
Current GIS approaches to assessing the impacts of highway development use photographic imagery
(usually low level aerial) to delineate vegetation using the Anderson Level I, n, or m classifications
In addition to accurate measures of habitat area, this imagery provides perimeteMo-area ratios and other
measures of habitat fragmentation and isolation. Some analysts are hoping to use the gap analysis
program data developed by the U.S. Fish and Wildlife Service mat correlates Landsat Thematic Mapper
vegetation imagery with ecosystem types and vertebrate distributions (Idaho Cooperative Fish and Wildlife
Unit 1991). Even more promising is me use of GIS in highway planning that has grown since McHars
(1969) advocated map overlay methods to determine me suitability of land for highway development
The anticipated rapid growth of highway systems in North Carolina has prompted the State to create a
Center for Geographic Information and Analysis to provide the locational data on natural resources
needed for effective highway planning (Fred Skaer, FHWA, personal communication).
5.4.3 Characterization of Habitat Values and Impacts
Once habitat areas have been classified and mapped, potentially impacted areas need to be
characterized hi terms of ecosystem values and functions. Traditionally, habitat characterization per se
has been limited to wetlands. Others considerations have focused on individual species and water quality.
Species Characterization
In the ecosystem approach to ecological evaluation, analysis of impacts to individual species continues
to play an important role. To adequately consider the role of individual species in ecosystem protection,
current analyses conducted for endangered and threatened species and for species of economic and
recreational important need only be extended to other rare and ecologically important species. In each
case, predicted mortality from road kflls, contaminant toxichy, and habitat alteration should be evaluated,
.as well as indirect effects on population status, behavior, and movement patterns.
The important factor hi species analysis is identification of the sensitive species. The number of
federally and state listed threatened and endangered species is very small; however, many more species
can be included if consideration is expanded to include U.S. Fish and Wildlife candidate (category 2)
species and state species of concern. The best approach is to survey the species list of each major animal
group (e.g., invertebrates, amphibians, reptiles, birds, and mammals) for rare species, species threatened
by other stresses, migratory species, and keystone species (such as raptors). Potentially sensitive plant
species can be identified through rare species lists and plant community analyses mat identify dominant
Ecological Impacts of Highways 29 April 1994
-------
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vegetation layers, important food source plants, and species critical to nutrient cycling. Plants and
jgnirrials associated with special or unique habitats (such as cedar glades, shale barrens, talus slopes, cliffs, 4fe
and caves) should also be included. Special attention should be given to symbiotic species such as ^F
butterflies and their host plants.
In the urban setting, fewer species will be present, but consideration should extend to the full range
• of "urban" wildlife that increase as more edge is created around fragmented woodlots and wetlands (such '
as raccoon, opossum, muskrat, squirrel, woodchuck, cottontail, chipmunk, meadow vole, American .load,
robm ftf^ c3n"fliTi?iij flTiy deer).
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Aquatic Habitat Characterization
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JII Traditional water quality analysis can be extended to mclude rigorous assessments of aquatic habitat.
The FHWA Technical Advisory T6640.8A addresses'" unpacts to major streams, rivers; reservoirs, and"
springs.'""' More specifically, the FHWA-reference manual for Assessing Water Quality impacts from
Highway Maintenance Practices (Krame et all 1985) prescribes a Habitat Evaluation Method which
classified"jnnpactsT The habitat assessment has mree basic goals:
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(1) Assess the resource value of the undisturbed habitat of the nearest receiving water
P downstream of the expected impact.
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(2) Predict what effects' the expected disturbance might have on the habitat in terms of habitat
loss, alteration, or displacement.
(3) Assess the value of the disturbed habitat and determine if the difference hi resource
values constitutes a significant impact.
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The method is based on the principles set forth in the Habitat Evaluation System (HES) as adapted by
tie U.S. Army Corps of Engineers (COE, 1980) from the Fish and Wildlife Service Habitat Evaluation
Procedure (HEP). The HES operates on mree basic assumptions: (1) the presence or absence, and
abundance and diversity, of animal populations in a habitat or community is determined by basic biotic
and abiotic factors mat can be quantified; (2) if the necessary habitat requirements for a species are
present, 'then a viable population will be, or could be, supported by that habitat; and (3) general habitat
characteristics can be used to indicate the quality of a habitat and its ability to support fish and wildlife
populations.
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The .HES method determines the quality of a habitat type using functional curves relating habitat
quality to quantitative biotic and' abiotic characteristics of the habitat (i.e., a habitat quality index is on
die ordinate ranging from 0-1 for every parameter;, a curve based on a particular measurement endpoint
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is used to quantify the effect). Habitat size and quality are combined to assess project unpacts. The
'which is applied to'"each "
Step 1. Determine habitat type or land use areas.
Step 2. Derive habitat quality index (HQI) scores for each habitat type or land use category.
Score and^weight specific variables based on importance to habitat quality. Calculate an
r;^; '• aggregate score.
Ecological Impacts of Highways
30
April 1994
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Step 3. The area of a given habitat type is multiplied by the aggregate HQI to obtain a Habitat
Unit Value (HUV). .
Step 4. An HUV is projected for die impact of future maintenance activity based on estimated
changes in habitat type due to such influences as channel dredging, sediment loading, and
addition of toxic materials.
Step 5. Calculate the impact: HUV after practice - HUV before practice = impact.
Step 6. The significance of the impact on me resource value of the habitat is evaluated and
possible mitigation requirements examined.
This evaluation requires data from streams and lakes on .basic chemical, physical, and biological features
of the receiving water bodies. Key variables required for streams include fish species association,
sinuosity index (SI), total dissolved solids, turbidity, chemical type, and benthic diversity (aquatic
macroinvertebrates); additional .variables for lakes include spring flooding index, mean depth, shoreline
development index, total fish standing crop, and sport fish standing crop.
This approach to aquatic community characterization is similar to mat being used by EPA's.Office
of Water to develop biological criteria hi support of the water quality standards program (EPA 1990).
Biological criteria research has developed several powerful methods for characterizing aquatic
communities (e.g., the Index of Biotic Integrity, see Karr 1991). These methods are based on the
presence, relative abundance, and condition of several species within an aquatic community and provide
substantially better measures of habitat composition man traditional richness and evenness indices of
diversity. Although existing methods are most applicable to stream ecosystems, technical guidance is
being developed for other waterbodies (e.g., lakes, rivers, estuaries, and wetlands) (Southerland and
Stribling, in press). Application of new biocriteria methods, as well as modifications of HEP procedures
(e.g., Pennsylvania's computer-based PAN HEP), should greatly increase the ability to characterize
aquatic and other habitats.
Qualitative methods for characterizing aquatic habitats include assessing potential impacts to
waterbodies whose value have been recognized by official designations, such as Wfld and Scenic Rivers
(as required by FHWA guidance). Unfortunately, too few rivers have been designated as wfld and scenic .
to affect many projects. There are a much greater number of sensitive river segments in the National
Rivers Inventory and even more hi the American Rivers' Outstanding Rivers List (Southerland et al.
1991). Outstanding Resource Waters are also identified in state 305(b) waterbody assessment reports to
EPA (U.S. EPA 1993). A review of the rivers and streams included in these lists should be a mirnmuim
requirement for characterizing aquatic habitats in the project area.
Wetlands Characterization
Wetlands have also generated substantial research into methods for characterizing habitat. The
Wetlands-FHWA Technical Advisory T6640.8A requires analysts to identify all wetlands using the
National Wetlands Inventory (NWI) maps, Soil Conservation Service (SCS) soil surveys, and field
surveys, as needed, to delineate wetland boundaries according to the current jurisdictional wetlands
manual (U.S. Army COE Environmental Laboratory 1987). Analysts may also designate certain wetlands
as exceptional resource value wetlands, including wetland special areas outside the highway corridor that
Ecological Impacts of Highways 31 April 1994
-------
I, ........ lii ' '"1 ...... 11! ' , n ..... ....... 1 i 1 '. i ..............
• i
may be subject to indirect and secondary impacts (West Virginia DOT 1992). Impact factors include the
size and proximity of the wetland, and the relationship of the wetland to its water source.
'
General wildlife diversity-productivity scores can be determined for specific wetlands using 10 criteria
(Golet 1976, U.S. Army COE and Minnesota Environmental Quality Board 19S8). These criteria include
3 based on vegetational community composition, 3 on wetland structure, 2 on wetland hydrology, 1 on
adjacent land use, and 1 on water chemistry. More commonly, the Wetland Evaluation Technique (WET)
developed for FHWA can be done to determine a functional assessment (Adamus et al. 1987). Wetland
functions of concern include nutrient removal/transformation, sediment/toxicant retention, sediment
stabilization, floodflow* alteration, groundwater recharge, production export, aquatic diversity, and
'; '*, ' ' " wetland-dependent bird habitat diversity. WET n analysis .can be used to develop a rating value for
"''rf, ': ;' wfldlife with a Mgh rating designating floodplaui wetlands, lai^e and vegetationaUy diverse wetlands, an^
moderate-size wetlands that are oases or complexes with some interspersion (U.S. DOT and Michigan
|!" ill 'L;'1!1'1 , i» iiiiiiiHIIililUfc '"I'ii'iJiii'i'illiiilPliliinBHiSiiiliiiii!11 Jllllhi;!llllllllllllliiiiiii'i|l' j'liiiiiiiiiiiiiiiiiiiiiiiiau'ijiiiiUiiiiiiniiiiiiiPi,"1!!!, «niiii«iranii!Pi ..... iiiNiiiijiiiiiiiiiii'^iiiiiiiii^iiiiiPBr/iiiiiiJiniiiiJ!!:11'.!;' jiiii'ii irfiifc ..................... ............ ^ ..... ,n, ........ ,,, „» ......... , ..... ........................................... ™, .......... ,... yg ..... N™™,, [[[ ....... — ...... , ................. ...... , ................. s», . .......................................... .• .............
DOT 1991). Individual functions of wetlands such as plant and wildlife support, flood protection, and
water quality should be determined and mitigation designed to replace lost values. FHWA has developed
specific design criteria for replacing these functions when creating wetlands (Marble 1990). Another
approach is to apply TTEP to wetland characterizations. The use of HEP analyses is being reviewed for
use hi wetland mitigation banking programs for highway development in North Carolina (McCrain 1992).
Terrestrial Habitat Characterization . .
Characterization of terrestrial habitats can follow the same models used for aquatic and wetlands
habitats. In particular, the Habitat Evaluation Procedure (HEP) of the U.S. Fish and Wildlife Service
and the Wildlife-Habitat Relationships (WHR) of die U.S. Forest Service .and certain state wildlife
agencies have been applied to multispecies terrestrial ..... communities (Schroeder 1986, O'Nefl et al. 1991, ........
Short and Williamson 1986). As wife wetland and stream habitat evaluation methods, subjective values
can be attributed to terrestrial environments. Following a Forest Service protocol, community importance
values can be assigned based on 9 characteristics: diversity of plants and animals, density of plants within
each community, canopy height, amount of each community in the state, number of game animals per
community, geologic age and degree to which the community is a relic, moisture requirements of each
community, ..... "the ...... relative degree ...... of insularity in the discontinuous phase witiiin climax communities of
lower sensitivity", and degree of ecological succession. Each factor can men be weighted on a scale of
2 to 10 and summed for the habitat type. (De (Waal Malefyt etal.1976).
Where detailed characterization of terrestrial habitats is not possible, qualitative methods of
designating sensitive areas can be applied. FHWA has existing guidance on the inventory of section
4(f)/6(f) lands including state parks, national recreation areas, community parks, existing and. proposed
National Wildlife Refuges, trails, and other lands acquired or developed with Land and Water
Conservation Fund assistance. These and other natural areas, such as local greenways, private preserves,
aid ..... certain national forest, ...... should be identified and their 'pace ...... in the landscape described. Other areas
that are more disturbed should also be considered as they may be successfully functioning natural
ecosystems of local importance. .Even these human-altered areas are becoming increasingly valuable (and
vulnerable) as others like them are eliminated by urbanization.
','"',. ..... , ~i: " " ............ "' . .......................................... • ' ..... " .......................................... ".'„ ........................... I [[[
!""! Existing designations for identifying sensitive habitats can be taken from national forest management
prescriptions (MP), e.g., wilderness (MP 5), areas emphasizing management for species intolerant of
disturbance (MP 6.1), and areas emphasizing semi-primitive non-motorized recreation hi a natural setting
i ;
-------
(MP 6.2). Otiier possible designations include special botanical areas (defined as state natural heritage
program and national forest management plan (MP 8) areas emphasizing preservation of unique
ecosystems), areas of national significance, and research areas. Many other federal and state
designations have been developed mat should be included in terrestrial habitat characterization. Many
of these designations are compiled in the EPA report, Targeting Priority Natural Resources: A Review
of National lists (Southerland et al. 1991). Twenty-five lists are included comprising over 5,000
terrestrial sites. Many more state designated sites may be found on lists mat are not yet centrally
compiled.
Landscape characterization from remotely sensed data is especially valuable in classifying vegetation
as a means of selecting sensitive habitats. The Anderson Level n Land Cover Mapping from USGS
provides division of forest habitat in deciduous, evergreen, and mixed categories; additional data on local
species associations can provide the more specific vegetation associations needed for habitat designations
related to ecosystem protection goals. For example, remote habitat may be given special consideration
as h supports species intolerant of disturbance (e.g., bear, turkey, bobcat, fisher, warblers, woodpeckers,
thrashes, gnatcatchers, and flycatchers). To evaluate forest fragmentation, the pattern of forests larger
than 200 ac can be determined (because smaller areas do not support forest-interior species).
Riparian areas are a habitat type of special interest because of then* inherent wildlife value and
importance for landscape connectivity. The FHWA authority (Floodplains-FHPM 6-7-3-2 Location
Hydraulic Study hi 23 CFR 650) "... to avoid or minimize highway encroachments with the 100 year
floodplain, where practicable, and to avoid supporting land use development which is incompatible with
floodplain values," can be used to protect riparian habitat mat provides ecosystem services whhin the
floodplain. Areal measures of the regulatory floodway and 100-yr floodplain (high to moderate risk) and
flood hazard areas (low to moderate risk) are already incorporated into environmental assessments of
highway development. In a similar way, existing analyses of geomorphology, surface geology,
groundwater, soil associations, and hydrology can be used to delineate ecological regions and then- unique
watershed values.
In a similar vein, other existing analyses conducted in environmental assessments of highway
development could be expanded to consider landscape units as functioning ecological systems. For
example, evaluation of impacts to the aesthetic and visual character of the site (using visual unit
boundaries of 1/2 mi for 30 sec of visual experience at 55 mph) could be modified to encompass
landscape ecology principles. In addition, air quality considerations focused on compliance with national
ambient ah* quality standards (NAAQS) could be expanded to include vegetation effects not hi the
standards. • •
5.4.4 Comparative Methods
Ultimately the analysis of ecological impacts from highway development must make a clear and
concise comparison of the impacts of each alternative on each ecosystem endpoint. As pointed out hi
Section 4, the suite of ecosystem endpoints of greatest concern varies with the category of highway
development, i.e., urban, suburban, rural, and wildland. Similarly, the type and degree of impact may
vary with each category. In most cases, however, the methods for measuring the impacts are the same.
Ecological Impacts of Highways 33 April 1994
-------
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The simplest method for comparing impacts is to develop a checklist for each ecosystem endpoint.
This may be expanded into matrices that directly illustrate impact degree across endpoints and
alternatives. ......... Where ........ more complex relationships between impacts and endpoints' can 'be measured,
modeling approaches may be used. Finally, spatial measures of impact can best be compared using
graphic methods. Inessence, the comparison of impacts is a table of alternatives vs. ecosystem endpomts
that includes in each cell a qualitative or quantitative measure of predicted impact. Where possible, these
cells should summarize all potential direct, indirect, and cumulative impacts on the ecosystem endpoint
To arrive. at such a summary table, individual analyses may be required for the impacting activities
occurring during each of the four phases of highway development: planning design, construction, and
operation. Within each phase, the relative importance of die following stressor processes can be
'
n ..... , ...... f
Alteration of topography. .............
'^e^d^bn'xemoyd.
' fl; ...............................
gnd wqrming,
'li'iri'iiillllilli i ' IE!'" « IIIIKi'iii'i
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• Noise and visual disturbance.
• Dirett mortality from road kills.
Hi , "!!" ji" '"i ........ Ill" iff,, ' iWllllil, mi • ,i|iil|i|||||ili|i ,F,, ..... J .......................... ......
Qualitative measures may be limited to a description of impacts to individual ecosystem endpomts.
For comparison purposes, this requires summarization of the magnitude, duration, awl frequency of
>; impacts in an ordinal scale such as high, moderate, or low impact. Where possible, numerical measures
o^r -mpact: gjjQ^j-j jje derived. The simplest measure for sensitive habitats is area! extent. The number
of acres destroyed or degraded can be determined by overlays of corridor siting or construction design
drawings with habitat maps. More complex measures of impact are required to describe fragmentation
and indirect effects. Because of edge effects, forest habitat degradation may be more accurately described
by perimeter-to-area ratios for individual forest blocks. Distance to adjacent habitat types can also be
measured. Lastly, numerical measures of habitat mterspersion and connectivity can be given. Although
there is no consensus or standardized protocol for quantifying edge effect, bom vegetation measures and
animal behavior analyses can be used to define edge width. Accurate evaluations of fragmentation
impacts require an adequate means of'quantifying edge length and width (Yahner 1988).
A simple comparative analysis was conducted by Bohm and Henry (1979) for highway development
through a valued forest area surrounding Paris. They set up an algorithm for eliminating extreme
alternative choices a j7rzon by usmg two conflicting criteria: the number of forest ac lost and the number
of driving miles required. They set bounds on the extreme amounts of forest loss per acre mat would
be acceptable (e.g.,10 ac per mile and 100 ac per mile). Where estimates of route impacts fell below
or above these thresholds the route alternative would be eliminated. Although these ic™fc of comparisons
can be constructed for any number of possible tradeoffs, the interactions among multiple scenarios rapidly
increases the difficulty of the analysis.
i
i ,
Ecological Impacts, of Highways
34
April 1994
l"1"1,:,,,i» : ''I Mill: ..iJliliill " I . ' J1
-------
Methods developed for the selection of transmission line routes can be adapted for highway corridor
selection hi fee planning stage, and provide an illustration of possible ways of stanffordirigg differing
impacts. De Waal Malefyt et al. (1976) attempted to quantify such important factors as number of unique
vertebrates, number of endangered vertebrates, areal extent of each community in me state, degree of
stress, and degree of negative impact from construction by measuring the total length of sensitive areas
crossed by the transmission route. These sensitive areas, included steep slopes, lakes, stream, marshes
and wetlands, forest, and specific areas of ecological sensitivity. They applied a screening process mat
produced a regional sensitivity survey of the 23,000 m2 area and identified habitats of endangered fauna,
geographically isolated biotic communities or those of limited extent, and research natural areas. Two
criteria were used to assign impact levels to areas with, the greatest sensitivities. First, impacts to biotic
communities (based on floral composition) were described in acre-years per mile (as a measure of area
and time needed to recover the natural composition). Community impacts were assigned levels 1 to 5
and then were refined with 6 characteristics: areal extent, revegetation potential, floral density, support
for vertebrates, and importance to protected species and stability. The second criterion measured the
geographic range of human-interest animals and identified critical habitat areas. Impact levels of 1 to 5
were assigned to each community based on potentially impacted area. The sum of these areas within each
link of the transmission corridor equaled total impact; the vector sum of all links equaled the route
impact. This kind of acre-year analysis incorporates bom spatial and temporal impacts into a single unit
analysis mat can be adapted to the evaluation of ecological impacts from highway development.
While it is important to quantify impacts, care should be taken not to compare acreages lost among
habitats of different values. la most cases, unique natural areas should be evaluated separately with all
ecological functions explicitly considered.
The following table illustrates potential ecological effects mat might be identified for a hypothetical
set of highway development alternatives. In mis hypothetical example, a new highway project has been
proposed and two possible alignments are evaluated (along with the no action alternative). The project
is planned for a rural area with substantial areas of bom agricultural and natural habitats. The natural
habitats are predominately upland forest (including old growth stands and wilderness areas) with a few
wetlands.
Ecological Impacts of Highways 35 April 1994
-------
fc'llt'*!'"
i' vii'1'1'i n;i iiiii!'.
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IP! ,,':"'»,;;»• , ,'" ,i :, i • 1."'!' • j1, !!- . • , ! ""• ill* • », .irvi, 11 «• •'',', jjlk! .'«• ' li,'"'!',,'' *, •„ ,,! • "if1!! •+•' 'i,* t :!'•«! ' „ ,»!" I j'!"1'1 • ' ,:'i '"!!'''"' !'::i, i» i'i!''!! ii' Jiil!!,; i! ' !!!i!!';, •
Comparison of Effects of Alternatives on Ecosystem Endpoints
, i.
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Hi,;, : "Illiijg? l;'i" ...... |; I 'i1'! i,,,,'i!i! Ii, ...... "iiFlii,,; ..... U1
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"PfO^YS'I 'fc!M ENDPOINTS
Consistency with regional
plans*
Integrity of regional
ecosystem.
Area of sensitive
Status of sensitive
Wfifiv^
-------
5.5 Evaluation of Cumulative Impacts
The evaluation of cumulative impacts to ecosystems from highway development is an essential part
of any environmental impact assessment. Fortunately, the ecosystem approach to ecological impacts
analyses recommended above incorporates the basic principles needed for evaluating cumulative impacts.
Nonetheless, it is valuable to review the following crucial steps involved in cumulative effects analysis:
1. Defining the goals of me assessment. . .
2. Setting the spatial and temporal boundaries of the study.
3. Establishing an environmental baseline for assessing impacts.
4. Selecting the impact fectors to be included in the study.
5. Identifying the role of impact thresholds in the study.
6. Analyzing the impacts of the activity (alternatives) relative to the baseline.
7. Recommending mitigation and monitoring based on the cumulative effects.
These steps closely parallel the evaluation approach presented hi.mis report Of greatest importance, is
the need to set spatial and temporal boundaries based on the resource of concern, i.e., the ecosystem.
In addition, the enumeration of these steps highlight the additional information needed to conduct
cumulative effects analysis as part of the evaluation of ecological impacts from highway development.
Specifically, cumulative effects analysis requires an environmental baseline against which to compare
ecosystem condition (no. 3), identification of other related actions potentially affecting ecosystems (no.
4), and thresholds of significant cumulative impact (no. 5).
Cumulative impacts to ecosystems must be measured against a baseline condition. Depending on the
timeframe of concern, mere may be a need for bom historical and future baselines derived from trends
hi ecosystem change. One of the special problems associated with highway development is the
accumulated effect of individual components of the highway system and the secondary development mat
often follows. In assessing cumulative impacts to ecosystems, special emphasis should be given to
including development activities mat reduce the area! extent of .habitat types. Lastly, thresholds of
significant impact must be set. Because ecosystems are affected in some way by virtually all activities,
the cumulative effects analysis problem can become intractable unless significant levels of change are
defined.
A number of specific methods have been developed for cumulative effects analysis. Narrative
procedural guidance has been developed from reviews of existing methods (e.g., Horak et al. 1983, Lane
and Wallace 1988) and additional conceptual frameworks have been proposed by Westman (1985) and
Bedford and Preston (1988). Mathematical representations of the cause and effect relationship have
included flow diagrams, networks, and matrices (e.g., Stall et al. 1987). More quantitative statistical and
modeling approaches based on analysis of historical patterns of impacts have also been developed (e.g.,
Gosselink et al. 1990). One of the most useful approaches involves map overlay methods that range from
general landscape suitability, ratings (McHarg 1969) to individual habitat patch preservation priorities
(Scott et al. 1987). The recent advancements m GIS technologies have greatly increased the
sophistication of current map overlay approaches.
The synoptic approach to cumulative impact assessment recently developed by EPA for wetlands
(Leibowitz et al. 1992) provides a practical framework mat could be adapted to any habitat type given
adequate data. The approach rests on the selection of synoptic indices (actual functions and values within
Ecological Impacts of Highways 37 April 1994
-------
I
the particular environmental setting of interest) and landscape indicators (actual data used to represent the
indices). By "associating a parameter of concern (such as integrity of interior forest songbird populations)
with a measurable indicator (such as forest patch size), the cumulative impacts within the landscape can
be determined. These synoptic indices can men be compared across landscape subunhs (e.g., counties,
It ..... :' I, Mi I (I I | ^1^^^^^^^^^^^^^ IIIIIIIIIIIHIIIIII I Illlllllllllllllll 111 I 1111 J ..................... *. [[[ r . ^ . N "
tfwi in iffl watersheds, or ecoregions) to promote better decision-making and highway planning.
™n| "™" ~ | ' "* J'1|n|" : | " / '||f"' ^" ..... ~ ....... jj' , | ^ '|l|"°' n™" " |
For many situations, assessment of cumulative impacts on the regional scale, so important to
* understanding threats to ecosystems, poses major difficulties. Frequently the region-specific data
, ..... , , ...... necessary for such assessments are lacing, particularly within the time and "resource constraints often
involved in ..... preparing environmental ...... analyses ..... (twin ...... and ....... Rodes ........ 1992). This emphasizes the need for
:l ,. I ..... federal agencies to cooperate in developing regional baseline information. ........... Even ...... for small projects, it ......
;*f should always be the objective of the environmental document to analyze impacts at the largest relevant
ale, based ...... on me ...... affected resources and expected impacts. .....
1 ,t' ' ' : , ^ &' ' ...... sv ........ wiui ...... a .
' ' ^^ • ' '1 • '
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• ..... .>, ,£ < ', : t" 'iii.*'1. ..... ..... IF..!: ...... •
FHWA recognizes me importance of regional analysis and has taken a significant step toward
improving the consideration of cumulative impacts by publishing an 8-step framework for incorporating
secondary and cumulative impacts considerations into the highway development process (FHWA 1992):
1. Conduct area-wide planning early in the process and look for links with .programmed
development and resource management plans.
2. Where planning information is not available, use historical data and trends information as an
indicator of future Development ..... [[[
i * ill ii i yn .............................. l
11:111 !""llii!l" ......... "'
3. Determine recent and expected changes in development and resources as a measure of
susceptibility of resources.
* x l
4. Rdate information on trends m development to geographic scope of me project.
* ......... • [[[ ' [[[ ; ...................... I ..................... ......... ....................
5. Incorporate the time period defined by the project design life in the analysis of impacts. .
•'..! ' •
6. Assess the impact of all planned and potential development in areas influenced by the project over
its life.
!
7. Estimate me contribution of the highway project to projected development based on project
or' facilitate devdqpmeat. '' .
.
'i.Ti -I ..... Hli.
.; ^
. ..... '"" ; 8. ....... Develop ...... mitigations that are "reasonable and related to project impacts. Recognize mat measures
-I ..... Hli. .......... ...... I .............. ............ in".!!. ......... ............. ' ....... .................... iii ...... ill ...... i ..... €^ ......................... _ ........... S ......................... » ................. ., [[[ w .................... . ................ ,,,,,, ................................ £ ............. ~ . _ , - , ..
' ' to address ...... future, development are often beyond the control of highway programs and require mat
'^^g^way ...... proponents work with local agencies to incorporate environmental protection provision
-------
6. Mitigation Measures for Ecological Impacts of Highways
CEQ guidance requires that mitigation measures be considered even for impacts mat are not
themselves "significant" once the proposal as a whole is considered to have significant effects (46 Federal
Register 18026, 1981). In me case of highway development impacts, these measures must include bom
specific design alternatives (that could decrease pollution emissions, construction impacts, and aesthetic
intrusion) and other mitigation activities such as relocation assistance and possible land use controls mat
could be enacted. To adequately consider ecological impacts of highway development, mitigation
measures should be developed within the ecosystem framework and should consider the possible impacts
of the mitigation itself.
6.1 Ecosystem Approach to Mitigation
Mitigation for ecosystem protection should address the cumulative impacts of all activities within the
landscape (which, depending on the scale of the project, may vary from small watersheds to areas
exceeding several thousand acres) to ensure that ecosystem integrity and health are maintained. The
preservation of individual habitat areas is important but not always sufficient to maintai^ the ecological
integrity of the greater ecosystem. In addition, the size, diversity, distribution, and connectivity of key
habitat tracts must be conserved to provide for the natural diversity characteristic of the larger eco-
complex or region. The two most important methods for maintaining the integrity of fragmented habitats
are (1) the provision of buffer areas, and (2) the creation of habitat corridors. Buffers represent the
principal method of avoiding impacts to sensitive areas, and habitat corridors provide the best means of
mitigating habitat isolation. The most common means of creating bom buffer areas and corridors is the
. preservation of natural habitat along streams, steep slopes, and other sensitive areas.
Habitat Buffers. The preservation of a sensitive habitat includes bom the avoidance of direct
conversion of the area and the maintenance of adequate buffer areas so mat edge effects and other
negative impacts do not affect the sites. For example, highway corridors through forests can be
"feathered" to avoid some edge effects (Gates 1991). Additional areas adjacent to the corridor can be
cut to create successions! bands of vegetation parallel to the corridor opening; mis reduces predation rates
at the edge and minimizes the barrier effects. However, a wider edge results in less forest interior.
Research into the impacts on benthic invertebrate communities indicates mat buffer strips between
roadways and streams of at least 30 m are required to prevent alteration in invertebrate diversity and
ecological structure (Erman et al. 1977). These buffer strips serve to mahitam the riparian canopy and
to stabilize the stream channel.
Habitat Corridors. Mitigation of habitat fragmentation involves the maintenance or restoration of
habitat "connectivity" (Norse 1990). One way to address, the fragmentation caused by highway
construction is to reduce the effective width of a highway corridor and decrease the barrier effect. In
addition to reducing the number of lanes or roadside area, providing wide, densely vegetated medians
can facilitate movement of some species across the highway. However, road kills due to collisions
remains problematic. For those species that cannot cross highways of any size, fragmentation must be
addressed by the provision of habitat corridor underpasses. Corridors have been used successfully in
wildlife management for SO years (Harris and Atkins 1990). Corridors provide for the movement of
armnaiSj serve as a population source, contain whole communities, and withstand natural disturbance
events, but they also provide for contamination transmission (Csuti 1991). Unfortunately, because edge
Ecological Impacts of Highways 39 April 1994
-------
I III
III I 111
ill (IIp II
effects reach 200 to 600 m into the forest (Pace 1990), optimal corridors widths cannot be achieved with
highway bridges and must be addressed when siting the highway.
Although the development of specific mitigation plans must be based on a thorough understanding of
tie site conditions, certain basic principles of ecological management should be followed when mitigation
measures are developed. The following general mitigation principles apply to ecosystem protection
"efforts: ' . '
41' il'Silll !'! i fiM'iJll! ,
1. Base mitigation goals and objectives on a landscape-scale analysis mat considers the needs of the
'
I!:
"UK HI! ..... ,'t ;.iu 'IS,.!!!'
,11.1 'thin!'. ILIUM, ' ihhlli :,,;
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2. Mimic natural processes and promote native species.
I '! :«, !•! "TBil1"., Foil1 '' "IIH'ilJ, ',;•,,* • „„,,,• , .» „, „ ,,,,, ,, ,, , , ,, ,„,, „,„., ,, , ,
3. Protect rare and ecologically important species and communities.
' ' Jl" :,; 'i:. 4TT !j,i, nil JIN I1: .til ^v " Tii 111 i1?: ,mx „ , : .;, ,i « UHI > »„ 'i ;, r .1 j,/,,,. .IF!!,:™*!:':'!,!!! ::;» HU'iiii'ir iiii'rir i' I-IJHI ,1;,, j'lki' L,,',:„! • „ ,> '1,1:,!. 'IT
4. Minimize fragmentation of habitat and promote connectivity of natural areas.
lk''"i O'tlf':1:'! "i"1 I ....... I" I1 ' Tllillli1" I"1 n I 1 1 II i ill j
•;: ...... ' := .. i,
5. Maintain structural diversity of habitats and, where appropriate, species diversity to promote the
naturjl variety of the area.
III II I nil I ill II Pill
6. Tailor management to site-specific environmental conditions and to the unique impacts of the
!1'1:1 ..... :»'spcific degrading ..... activity., '"' ............... ; ........ '
illiil:'::! ':< '(I'''1'-'!* ' " 7. Monitor for ecological impacts and revise mitigation plans as necessary.
.ir-HiUf.i i"1- " i,.. tin1 „ "'" .v"'V 'iiiiiitii ( t'liiiiiiii in ii'f. i;:"! *37, • f- ; •. -,,. ,., f? 5' •. ,T .:- ,* .;„,
• f>3, Mitigations for Each Phase of Highway Development
The first priority in developing mitigation plans for ecosystem degradation should be avoidance of
the impact. This is usually a siring issue, i.e., locating all construction activities at a distance from the
habitats of concern. The ecosystem is adequately preserved if all possible impact scenarios are accounted
for. Barring this solution, effective management measures must be implemented to ensure the protection
...of jhe habitats,,pf concern. Failing effective management, mitigation falls to the restoration of habitat,
which is often problematic, or finally to compensation.
3; • iji I i' Li if ,J : • •', fit i \ ,'i1" ™{3v r, {::Sirii- :JJM • i;V ii"} \ if ii - "i'iiii ;n3," iiiiliii ii t;*~' f-'""!:: «•<" '** • •'':- >"",. iii,Hii" •;»','/9iitt. iwii>' « • »• I , ' ^,, '/' ,' l! '"i1*" ,>i*il>i 't
IIIII I III III II ,
IIIII II 11 IIIII I • . „. i
III I I "i I ' i II HI llll V
*
Ecological Impacts of Highways 40 April 1994
-------
6.2.1 Planning Phase
* *
The planning phase involves all pre-design activities including die siting of the highway corridor.
This is the most important opportunity for mitigation of highway impacts because it allows for
consideration of the roll range of landscape-level factors. The principal mitigation measure in the
planning phase is avoidance of sensitive areas during the selection of the corridor route. Because the
route selection is only constrained by the purpose and need of the project, alternative transportation
options can also be considered in mis phase.
As soon as the purpose and need fox a project has been developed, environmental considerations and
potential mitigations should be enter into the highway development process. Incorporation of these
concerns early in the planning process is the best way of avoiding irreconcilable conflicts. Consideration
of alternative transportation options (such as railways and bikeways, or traffic management) should be
viewed as initial "mitigation" opportunities before the type of highway is selected. Whfle the range of
alternative transportation options may be greater in the urban and suburban settings, these alternatives
should be considered for .all categories of highway projects. The planning phase is also the best place
to consider effects such as reductions hi the carbon sink caused by vegetation removal and its implications
for global warming.
The next opportunity for mitigation is corridor selection. This is a critical step, especially in wfldland
and rural settings, because it offers the greatest range of options for avoiding sensitive habitats. For large
highway projects, corridor selection itself is worthy of an EIS, even though the actual roadway alignment
will be selected at a later time. In the case of Appalachian Corridor H (West "Virginia DOT 1992), a
corridor selection process based bn a width of 2000 ft was used as a means of considering the many
valued natural resources within the project area. The only way to avoid habitat fragmentation and
impacts to contiguous forest and remote habitat is to mitigate in the planning phase. The vulnerability
of many wildland habitats means mat even the most conscientious design and construction phases cannot
mitigate adverse impacts from a nearby corridor.
An important component in the consideration of corridor impacts is the likelihood and extent of future
secondary development. Again, these impacts can be especially devastating to wfldland habitats. In
devising planning phase mitigation for secondary development, the analyst should look at existing land
use within potential corridors, and project possible future land use (forest, agricultural, and urban) based
on current land use plans and controls. This requires consideration of state planning regions and local
growth centers. It is only in the planning phase mat conflict between ecosystem protection and economic
development can be resolved. Traditionally, environmental assessments have been limited to identifying
which alignment alternatives have the lowest potential for direct support of base floodplain development.
This approach should be expanded to include development on an sensitive lands, and mitigation
encouraged in the form:of appropriate applications of local zoning restrictions.
The final opportunity for mitigation during planning is the selection of the highway alignment (usually
a corridor of 150 to 300 ft). This is the step where specific sensitive habitats can be avoided to the extent
practicable given the general corridor route. The mitigation goal is to avoid ecologically sensitive areas
and limit encroachments to fringe takings rather than severances. To date, mis has included avoiding
wetlands, large forested or vegetationally diverse tracts, raptor nests, and major wildlife travel corridors,
as well as minimizing construction parallel to streams with important fisheries. As before, these
considerations should be extended to all sensitive habitats. Mitigations for secondary development can
Ecological Impacts of Highways 41 April 1994
-------
•11 III 111 111 111
III (11 III I Pill
•:•: '. : '. I--"1
,„:;,„ ,• L
••iri • j1" - j |;
1(111111 II 111 111 III 111,, "ll'll1 Illi'! "Ml:i ."ill:' , 'lull '! ' I'll!!-',!!'/';,
-------
Figure 1. Mitigations in the Planning Phase
Ecological Impacts of Highways
43
April 1994
-------
in, iiijijiyi!!1 'i"WIN"''.ill'1
it ;ji|iiiiiiij;p!:!«« ' irt'i'iii.
,111, I 'viTlll,
Design Phase
i •
The design phase involves the siting of the final right-of-way footprint and all aspects of structural
design and within design mitigations. This phase also provides several important mitigation opportunities
including both site-scale avoidance of sensitive habitats and structural modifications to the highway design
that may reduce impacts of fragmentation or off-site effects. Design of corridor width, median type,
roadside vegetation, and location of borrow areas can all contribute to the minimization of ecological
Impacts. Specific structural mitigations, such as bridges, underpasses or tunnels, and fencing, have
considerable potential for enhancing habitat conservation goals.
lill || , i,., ,'i • ,,,111 ' ,„»' ' ,„
Once the highway project has been planned (both corridor and alignment selected) many of the
opportunities for avoiding sensitive habitats have been removed. However, certain site-level changes in
the roadway footprint can be made in the design phase and these changes can tnfaimfae effects which can
not be avoided. These include limiting impingement on adjacent habitats (through lane adjustments and
bridge design), minimizing barrier affects (through the use of bridges and water conveyance), and
reducing pollutionimpacts (through noise walls, curb design, and catchment basins). The unique problem
of road kOls can be addressed through combinations of fencing and underpasses. At the same time, the
Design phase provides the opportunity for incorporating substantial restoration or habitat creation activities
within the right-of-way (mitigation banking may be better considered under the planning phase).
Avoidance of sensitive habitats through highway design is progressively more important in suburban,
rural, and wildland settings. Essentially, the strategy is to reduce the roadway "footprint." Reliance on
existing roadway alignments is a primary means of doing mis. It may also be accomplished by reducing
the roadbed elevation to minimize shoulder width; by shifting the alignment (e.g., to avoid pothole
Wetlands); or by widening the median to encompass small communities or wetlands. A reduced footprint
also allows for a larger buffer zone between the roadway and sensitive habitats, especially stream and .
' """ ""
I'"'11""""1'!';'!''1!!'
{! MB;" 'I El! 'HIM i 'i i : aill'T lii •• , !r, ' i I mill r, i ; JUKMHIJ , '"•' a ni
4:! Even mough sensitive habitats may not be directly altered, nearby highway construction usually entails
negative impacts associated with a "barrier effect." Designs to ameliorate the effect of highway barriers
should be based on an understanding of the functioning of habitat patches, corridors, edges, and the
landscape matrix in the project area (Gates 1991). Mitigations for nearby wetlands include use of
minimal practical slopes and median widths; maintenance of existing surface and subsurface hydrology;
and provision of passageways through and around structures for movement of biota. Burnett (1992)
. recommends the following mitigation measures for barrier effects in forests:
* "Construct narrow roads.
. . E;;:"* Leave .the canopy intact. •
' • Incorporate subrroad tunnels
*' Build long bridges (as opposed to culverts or tunnels) over gullies and waterways.
Although the provision of underpasses for animal movement is still being researched, it can generally
be said that long bridges are preferable (althpugji this entails higher costs). Barrier effects have been
demonstrated for reptiles and amphibians" and some small mammals. Certainly, the fall and spring
migrations of amphibians are problems hi certain areas. In some cases, successful migrations can be
facilitated with short-term traffic management, but roadway tunnels may be the preferred solution (Daly
1993). Solid concrete median barriers pose an additional problem and ithas not been determined whether
Ecological Impacts of Highways 44 April 1994
IIIHII i|h, j,, "I111 Ml,!i;,!i ::, rniUl ti'BIR » , , • j, ;i,,,' ." , „ "|ii,J" ;| f| + • " ' „• , iifll '„,, ";„,, ' ,,1. : ,„',,' '„ Jl, .H1 "'•..•,, >' <""'< ' ••&>'! , ,,„, • • "• •;, •; ,„ "| ' " :., " n
JUKI'1 ! ,1 ,' M",V\ ' IP "i JP'l'1 ,. "lll'll'llliliilill I"n •, ,1 ! lii,, K , ':' I1'1 lillin ' ,"' II ' ' III ,' JMI IN Jin1!1 I1 ... ". , , : • ,JI« ' "'« ' ' >. ",I!V iir 'PIP «!' ',lh' U II I ,"l " '
n|' llllilHl, t ' ilp1 i| : r.iil, < 1 Mi 'I, >,; U „ ,' j. "lib!! ."'H'llll . 'iiln '" :' >. ,n,,'i, < '"' ' HI1' , ',!! "V , ,' i, ' ' I" MlllPin'!!!!" " IP": ' " ,nl' , It ,i' lll'il11!! ". 'PH ,', 'I', ''il I ij " , ' , /'! , il < SI Jiitri1' 'ilU J
ijijiiiiiiiiiiiiiii,, AI ill, i,,;. jiiiiiiigggijiiipi jiiiEyiiiiiPiiiingnii jiiiiiiiiEiaiini i iiiiMiiiiiiiiiiiiiiiiii; iiiiiiiiiiiiiiiii, j. niiiii'i: iiiiiiiiijiiiiiiiiii^aiii,: „ iiijiniinii; iiiiiiiiiiiiiiiifi HIE:: ,1111 < iiiiiiSiir: tii lii ijuii IE jiiniii n iiiiiiiiiiiiiiiiiiiiiiiiiiiiii": JijiEaEiiiiiiiPiiiiihiiiiLiiiiiriiU':'.' ,iii! piiiniiiii!" ^ :i rj a :;< IIPLJ nih JC'iiinijiiiBiiiiiii!'1 nii.'ii.iiiii'iiini,: jiii'viniiiiii'iiaiiiiiiiiiiiiibi pHiUiiiiiii'iinii:,; a i iiig'iiiiniiiiiiinuiiAf i A, ? i^iinnini1: i! i<::ipi n iieiiiiiiiiiiiiiiaiiiiiiiiiiiiiiiiiiiiiiiiui .iiiiiiBiiiiii!',, •
-------
passageways in these barriers would be beneficial for smaller species (Adams and Geis 1981). Hunt et
al. (1987) recommend using a variety of tunnel sizes, because new tunnels are predominately used by
feral predators. Many species also require regeneration of native vegetation around tunnel entrances
before they will use them.
The U.S.H. 53 project hi Washburn and Douglas Counties, Wisconsin is an innovative example of
mitigation for ?™mai migration across a highway (U.S. DOT and Wisconsin DOT 1991). In mis project,
the highway corridor passed through an important wolf migration pathway. In order to minimi™* adverse
impacts on me wolf population, significant lengths of "wolf shift" zones (areas with a wide, forested
median) were proposed. Although mis wide median constitutes the minimal feasible barrier to wolf
migration, passage would still be adversely affected. To mitigate for this impact, full control of access
through mis section of the project (with no new private accesses allowed) was proposed. It was believed
mat the benefit of precluding secondary development in me project area (thereby preserving this dispersal
corridor) would exceed the adverse effects of the highway. In addition, to ensure that wolves or other
large animals such as deer or bear would not be restricted by the expressway, fencing would be installed
only adjacent to farms wife domestic herd animals.
Road kfll mortality is another important factor affecting a wide variety of species. Fencing is a
common solution, although the reduction in deaths must be weighed against increasing the barrier effect,
especially for long stretches of exclusive fencing (Leedy 1975). Research into the use of box-type
underpasses by mule deer crossing under interstates with big game fencing (8 ft high) indicates that
vehicle-deer collisions can be reduced by over 90% (Ward et al. 1980). However, results indicate mat
elk and pronghorn do not significantly use underpasses. All three species were twice as likely to avoid
roads when people were walking nearby than when traffic was present. While fencing solutions may help
resolve deer-human conflicts, Povilitis (1989) feels that road kfll problems are fundamentally a land use
issue (because conflicts arise when deer occupy wooded areas finely interspersed over land) mat needs
to be mitigated in the planning phase.
Another impact from highway development mat can be mitigated with barrier design is noise and
visual disturbance. FHWA noise abatement criteria (currently 67 dBA for parks and 55 dBA for
wilderness) could be based on threshold levels of substantial increase above ambient levels, not
predetermined levels. Noise abatement measures (usually entailing substantially higher costs) include
creating noise barriers of concrete, stone, wood, or earth; shifting the centerline away from sensitive
receptors; and depressing the roadway below the level of sensitive receptors. Van Der Zande (1980) has
shown that highway disturbance is especially severe hi open field habitats, and mat it cannot be eliminated
by simply placing walls or trees along the roadside, since these features only partially reduce the
disturbance. Where effects might be reduced by constructing me road below ground level, the benefits
must be balanced against the tendency of this practice to worsen hydrological impacts.
Perhaps the most severe barrier effect mat can be remediated within the design phase is blockage of
fish migration. As. stated earlier, the retention of natural habitat and maintenance of normal stream flow
are best achieved by constructing bridges mat do not impinge on the stream environment. However,
culverts are considerably more economical; therefore it is important to set threshold conditions where it
is appropriate to use culverts in place of bridges. Ideally, a culvert installation should not change the
conditions mat existed prior to that installation, i.e., the cross-sectional area should not be restricted by
the culvert, the slope should not change, and the roughness coefficients should remain the same. Changes
hi these parameters could alter velocity and sediment transportation capacity of the stream and adversely
Ecological Impacts of Highways 45 April 1994
-------
, mm .
• ; 3s ....... Jl •
* « ..... i'"' '«'
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1 i:,' • ; IH'li:; ,'i, ...... irl • .911 ' t ..... j!M ••'•i ......... li '.i ...... h i
materials such as riprap or geotextiles.
of Highways
46
April 1994
-------
• Omit the use of curbs for delineation and stonnwater runoff control where possible. Consider
leaving gaps in continuous curbs to allow transport of pollutants from the highway.
• Establish permanent discharge points for stonnwater, including directing stonnwater runoff over
vegetated surfaces, using wet or dry detention basins, or using infiltration systems to retain
runoff. .
Ecological Impacts of Highways 47 . April 1994
-------
i :i , i1!frt •,, ,1,'ln,; ; : • i •;; : i, '<;i A , t;.( »«tf im::; u;1 KM • '.iifiiK «Mn; R»*J :'' '
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. liltii"1!!1;! ,:,'i"n,,, ""SI 1 .""i'lJIiftiili!! V,1;
;*.'; r Jtlli; '(ii«f!«*Wi»iif, " ii'lfi 'llitii!;:-,' JUT'- '• ' :iiii {If H !' - i" i' : S • "ii'i'«f. "iff kill!1 <*'.','. ,"• '.if'S il
,„,,, n , , , .j.nnf „,,, l|il| , ,,,, , , , , , .I;,, HI „,,,,, , , „
Hgure 2. Mitigations in the Design Phase
I1
Ecological Impacts of Highways
i ',: w ':! ..... t: . a •: ..... t :;l!i v kr/ ;»] ..... i ••• w- a^
48
..... ;;::!"
• ..... I ........... n • .- ...... i •;«": •
April 1
-------
6.2.3 Construction Phase
The construction phase consists of the vegetation removal, earth leveling, and paving steps provided
for in the planning and design phases. While each of mese steps is required by the preceding decisions,
the specifics of the construction process can be modified to eliminate many of the short-term adverse
impacts of completing these steps. The opportunities for mitigation in mis phase are primarily pest
management practices (BMPs) mat reduce sou* erosion, toxic runoff, noise, and other construction-related
pollution. Careful planning and supervision of construction operations can also reduce unnecessary
vegetation removal and land scarring.
Mitigations of construction impacts are similar in urban, suburban, rural, and wildland settings, but
their importance may vary dramatically. la wildland and rural settings, where mere are more sensitive
receptors, minimization of pollution and disturbance impacts is especially important. Even in urban and
suburban settings, however, the cumulative effects of runoff from many highway projects may severely
impact downstream waterbodies such as the Chesapeake Bay.
The principal mitigation measure hi the construction phase is strict application of standard
specifications for erosion and sediment control, including routine inspections (Krame et al. 1985). This
involves the installation of erosion curtains, runoff settlement ponds, and stream diversions where
necessary. In general, 200-ft grass filter strips should be provided around staging areas and special
precautions should be taken to contain hazardous waste spills. Where possible, consideration should be
given to soundproofing individual sensitive receptors and or completely eliminating construction during
critical nesting or breeding periods.
An erosion control system plan should be carefully designed to minimally affect local water quality
and to clean sediment-laden water resulting from the disturbed area. If a stream passes through the
construction area, it should be diverted or piped so mat it does not acquire sediment. All sediment-laden
water is men channelized and directed to sediment ponds for treatment. Water should only be returned
to the stream when it has a sediment load comparable ito the undisturbed stream. To accomplish mis, a
ditch is built above the project and lined with plastic; a flexible pipe diverts the water; erosion bales are
used to contain runoff; chemical agents may be used to settle clay silt.
Construction can also install permanent pollution control measures marstabflize the disturbed area and
minimize soil movement through natural means. This includes the planting of grasses and the placement
of rock at culvert outlets and small streams intercepted by cut slopes. Revegetation should include early
topsoil placement, seeding, fertilization, and mulching for all disturbed areas (including marsh disposal
areas). Many new innovative mulches and nettings are available to eliminate erosion and minimize plant
growth delay. Retaining walls and sidehfll structures can be built of modular components to fit into the
natural topography and reduce construction time and limit impacts. Bridges can use precast structures
and on deck construction techniques to minimize terrain disruption, tree removal, and stream
encroachment. Haul bridges should be used to eliminate crossing streams with heavy equipment and
specially designed machinery or mats should be used to reduce soil compaction.
. Stream relocation should consider the needs of the resident aquatic community. Construction should
be limited to dates when spawning, nesting, and breeding are not at risk. If the relocation is permanent,
construction must be a true recreation and provide fish habitat in the form of deep pools, riffle areas, and
constant flow in new channel. The new stream should achieve a stable morphology and natural meander
Ecological Impacts of Highways 49 April 1994
-------
i ^^^^^^^^^^^^ !! "!
' ...........
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i ..... i! i"
ISM
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pattern (Rosgen 1985), and use natural materials and plantings. The original gravel size should be
maintained in the streambed, and stream shading vegetation should remain on the banks. Where habitat
structure have been lost, log dams, channel deflectors, overhang bank cover, ranker structures, and
boulders can be added* Equally important is the maintenance of natural riparian zones by minimizing
Vegetation clearing and protecting areas mat are not cleared.
"' :-' ,: I ' """" "":" =
Many innovative methods are available for maintenance of aesthetic characteristics following
' „;' construction. A return, to the natural landform is desirable for ecological as well as aesthetic reasons
(e.g., microclimate conditions). Careful landscape work concentrated near the base of fills and at the top
of cut slopes can blend the physical features of the site. Where slopes must be modified along the
roadbed, adjacent areas can be flattened and rolled to reflect existing landscape characteristics. Rock cut
sculpturing can retain natural fracture lines and cleared areas can be blended into "natural" .forest
openings. Careful revegetation efforts are critical and should use transplants of young trees from Hie
neighboring area, as well as native grasses and wfldflowers. Monitoring should be conducted to
'' determine if vegetative invasion from "natural areas is adequate.
ik, ....... in ..... ai ........ iii ,
< • » •<•'
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lili." 1JOK .',» t i .;>.!•( '! '.'VH ,,:"! ..... :. '»• .•"il"-!!'*-*:, l:^:i.V .•;.' Sfe'i' ,"li'.E' ...... :;<-~ "Hr ifciii! ':» ..... /".lit:,-:" i
i, • '*&•: ..... I'1:' --,: .......... .' i. ' '.-. ^ ••<:, &KV: ....... : rt „ "'• - ; "&<, M f ,; \ •; $$• ;•• ti " •; i.
11,1,1, " ..... ' ....... i, ,t(,i.,|,:",ii, i' ..... i'l'ilniiii!,"'!' " :'"! iiii'ii"!! .'! ...... ''
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IM
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i
-------
Figure 3. Mitigations in the Construction Phase
Ecological Impacts of Highways
51
April 1994
-------
6.2.4 Operation and Maintenance Phase
I in in
The operation and maintenance phase is the long-term result of the three preceding phases. A
highway will necessarily carry traffic and require regular maintenance activities. A certain amount of
' jj^ig--"(jxjgi ^_g^runoff and atmospheric deposition of toxic materials) is associated with road
traffic. Street parotmg, cleaning, and periodic construction also contribute to these impacts. Mitigation
opportunities in mis phase are basically long-term applications of BMPs similar to those used in the
construction phase. Stormwater retention ponds are one "of the most important. Another, equally,
important, mitigation opportunity is the requisite monitoring and enforcement activities required to ensure
mat mitigations included in the design phase remain functional for the life of the project.
' • ; | : ; ;
As with the construction phase, the pollution impacts of the operation and maintenance phase
generally have greater impact on the more sensitive wildland and rural habitats. However, because of
the greater traffic volumes in urban and suburban settings, the cumulative effect of highway operation
may be greater in these areas, especially in receiving waters. Fortunately, ft is likely that greater
mitigative efforts through maintenance programs wfll be available in higher traffic areas.
- General highway:managemlirtpoli^ can have a major beneficial effect on mitigating
the impacts of highway operation and maintenance. Even programs to reduce driving miles, automobile
emissions, and roadside litter are important. Direct mitigation measures in the operation and maintenance
phase fall into me following categories:
• I ' !
• Control litter and limit potential pollution sources.
• Properly manage the storage, handling, and application (at optimal rates wfth well-maintained
spreading equipment) of deicing chemicals.
in i inn i ii i i ii i ii in lit vw,,' i::iiii ™'' ii
« Manage pesticide and herbicide use so that sensitive receptors are not negatively impacted.
• Avoid direct discharge of highway runoff to receiving waters.
• Reduce runoff velocities through[flatter grades, drop sttuctures or baffles, br grassed waterways.
si ..'I"-. "" ' is'V : j^g™™jl^aj^ concentrations m" runoff by maintaining dense grass cover, increasing grass
height, and leaving cuttings on the ground,
• Properly manage roadside and median vegetation, using only native species and enhancing
wildlife food and cover where appropriate (e.g., for bird species not subject to road mortality).
Stormwater management is an important component of operation phase mitigation strategies and
^^^ ^g;^n™f ^^^ including vegetative
controls, detection basins, and infiltration systems. Vegetation management is associated with stormwater
management^ but also plays an important role hi the mitigation of wildlife impacts. For example,
vegetation can serve as noise buffers and shrub plantings can increase production of nesting birds (Leedy
1975). Mowing should be avoided prior to July so young birds and mammals can fledge and disperse;
while, selective mowing and cutting can be used to maintain ecotone diversity. Invasion by exotic species
Ecological Impacts of Highways .52 April 1994
I
-------
poses a special problem that should not be enhanced by plantings of non-native species along roadways.
Driver education programs can be targeted at reducing the transportation of exotics and intentional road
kills, especially of box turtles.
Ecological Impacts of Highways 53 April 1994
-------
Ill I 11111
Manage Vegetation for
_•__ _ ^Wildlife
"and Control of Exotics
Figure 4. Mitigations in the Operations and Maintenance Phase
Ecological Impacts of Highways
54
April 1994
-------
63 Ecological Restoration as Mitigation
When impacts to ecosystems cannot be avoided or substantially minimized during the planning
design, construction, and operation phases of highway development, mitigation falls to ecological
restoration. Recent experience with wetlands mitigation involving the restoration or creation of wetlands
has unproved bom the science of restoration (Kusler and Kentula 1989, Marble 1990,. Hammer 1992) and
the management of mitigation options for unavoidable losses (Kentula et al. 1993). Mitigation banking
for highway impacts to wetlands has been initiated hi several states under programs of varying design
(Short 1988, Eoworth 1991). An alternative to banks are "joint projects" where a group of developers
agrees to carry out a specific mitigation project to compensate for specific losses. Although the
restoration of large wetland areas that is possible under banking is desirable, the difficulty .of
compensating for the loss of on-site and like-wetland-type values suggests caution in relying solely on
mitigation banks (Kusler 1992). Nonetheless, substantial opportunities exist for integrating these
innovative approaches into FHWA procedures dealing with NEPA and Section 404 requirements (FHWA
et al. 1988).
Adequate mitigation of ecological impacts from highway development may require restoration of
habitat types other than wetlands. Fortunately, wetland restoration is increasingly being seen as a
landscape or watershed level activity (NRC 1992) mat includes restoration of other habitats (e.g., riparian
areas and forests). At the same time, new mitigation efforts are being focused on restoration of
endangered species habitats (David Wyatt, Caltrans, personal communication). Although the difficulties
in achieving sustainable restored wetlands wfll doubtlessly be duplicated as restoration is undertaken for
other habitat types, considerable success has been achieved for many habitats (notably forests and
prairies). The following five-point framework is proposed for addressing ecosystem restoration
(Southerland 1991):
1. Define the restoration goal. . • -
2. Specify the restoration objectives of sustainability and ecological values.
3. Apply a holistic approach to achieve functional restoration.
4. Assess the restoration by comparison with reference systems and integrated measures.
5. Use practical criteria mat reflect the desired ecosystem values for each ecosystem type.
Larger policy decisions, such as whether to restore for a particular use or for the natural condition,
should be addressed in Step 1. It is also the time to determine how to incorporate the landscape setting
into the project goals. When the goal is ecological restoration, the objective of a "natural sustainable
community" should be explicitly stated. In addition, the specific suite of ecosystem values and services
that are desired should be selected. This wfll determine the degree of restoration required and the
expected deviation of the restored system from the predisturbance condition. Even when it is impossible
to return affected areas (e.g., medians and roadsides) to their natural condition, innovative restoration
techniques can be used to better integrate the areas into the surrounding landscape (Barker et al. 1993).
Even simple tree planting along highways by organizations such as American Treeways and Maryland's
Cloverleaf Foundation (in coordination with state highway departments) can benefit the landscape
(Rodbell 1993).
The actual restoration steps required will depend on the condition of the degraded habitat to be
restored. Two classes of restoration can be envisioned for highway-related impacts: (1) restoration of
habitat which remains intact but is degraded by highway development activities and (2) restoration and
Ecological Impacts of Highways 55 April 1994
-------
iin ii mil i "lit
ii] WiiilFJlihiJi':,,::!!,!!!1'!" mill1 IF •
Jlllllllllll |||l|< liiiiNj'Ji'llfr'f,,,!!1!1!1!!1,:1' 9,H'
creation of habitat (both in-kind and different habitats) as a replacement for habitat mat has been
converted to "highway pavement or other incompatible use. The second class includes restoration or
creation within the highway corridor of habitats that provide desired landscape functions but were not
specifically degraded by highway activities. It is FHWA policy to encourage states to convert excess
rights-of-way to public uses or to joimvuse projects (Linker 1989). Increasingly, joint-use projects are
being undertaken to construct engineered wetlands for basinwide control of nonpoint source pollution and
water qpjjty improvement. Other types of restoration within extensive right-of-way areas include habitat
enhancement for certain birds species or restoration of remnant of prairie plant communities (Drake and
Kirchner 1987). The most important factor in conducting right-of-way restorations (and maintenance)
is the control of exotic species.. Bom accidental and purposeful introductions of non-native species
(especially plants) must be avoided.
Depending on the seventy of the degradation, ecological restoration will intervene at one of. the
Slowing stages of restoration: detoxification, creation of physical structure, restoration of chemical
balance and nutrient supply, return of vegetation and soil microfauna, integration of habitat features and
spatial heterogeneity of patches, and colonization with fauna. Whatever the method employed, the
assessment and modification of the restoration effort should be based on comparisons with appropriate
reference systems to ensure that the desired ecosystem structures, functions, and values are attained. This
reference-based approach may be most useful when combined wim a regional ecological classification
fsuch as Omernik's (1987) EPA ecpregions concept) and integrated measures of ecological integrity
_,_s^_..^_, ,._g___g _™_m_ £—j.^ — iggjj'g (199 j) index of Biological Integrity).
6.4 Mitigation Monitoring
""'' ^Monitoring is essential to understanding the effects' of a project. It 'is likewise critical to evaluating
Jne. Degree of implementationand successor failure of mitigation efforts. Effects observed through
Monitoring can help modify project management or improve future decisionmalting on projects with
similar impacts, or in similar areas (Canter 1993). It is unlikely mat adequate information on project
effects and mitigation implementation and success will be obtained unless it is provided for in the
monitoring program.
Many of the elements necessary for adequate monitoring will have been developed as part of project
planning and environmental analysis. These include the following (Noss 1990):
Gathering data.
Establishing baseline conditions.
Identifying ecological elements at risk.
Selecting ecological goals and objectives.
Predicting likely project impacts.
Establishing theobjectives of mitigation.
The following additional monitoring-specific steps can build upon these elements:
• Formulate specific questions to be answered by monitoring.
• .Select indicators.
• Identify control areas/treatments.
• Design and implement monitoring.
Ecological Impacts of Highways
56
April1994
i Jii:M^
-------
• Confirm relationships between indicators and goals and objectives.
• 'Analyze trends and recommend changes to management.
The breadth and specificity of the monitoring program will be determined by the habitat mitigation
goals. Mitigation of habitat impacts in the planning and design phases usually involve avoidance of
sensitive habitats and monitoring is required ensure mat the distribution of habitats was accurately
understood and that the attenuation of impacts at the habitat boundary were as expected. Mitigation in
the construction and operation phases primarily involve control of pollution. This is especially true for
wetland and aquatic systems where, after physical alteration, off-site impacts to hydrology and water
quality pose the greatest tfrre** Monitoring of pollution control measures is an essential .part of the
mitigation of highway construction and operation impacts.
The fact mat many restoration projects designated as mitigation have not achieved their desired
objectives is well documented. It is also believed mat mitigation measures for many projects are not
adequately implemented or enforced. Therefore, determination of the true effectiveness of mitigation
should be the goal of monitoring programs.
In the case of mitigation based on ecological restoration, monitoring is essential to determine
restoration effectiveness, and thus mitigation success. Practical criteria must be selected for use in
evaluating the success of restoring the habitats of concern. Because the constraints of practical
measurement are already being considered by various agencies in the development of environmental
monitoring programs, a greater range of validated quantitative ecosystem parameters may soon be
available for evaluation of restoration success (e.g., Hunsaker and Carpenter 1990). The following
categories of criteria are proposed as the minimum from which habitat restoration indicators should be
selected:
Areal extent
Absence of contamination .
Hydrology
Water chemistry and quality
Physical structure and soils
Nutrients
Productivity
Microbial community - . '
Vegetation
Habitat structure
Biota
Biological integrity
Population response.
Ecological Impacts of Highways 57 . April 1994
-------
ill 1,1 I, II
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,;< Hi.,, ;, jiiii •": i :f\[ :"!>•' ' ,: I|;;;;i;.,!i'iii i,'1"1,;, 'SNiim .iJi'i'nihi'.T u1,1"1
1, P'll"1 ,'! 'Li11., ,', ,i: 'illl',,,* V1"!:!'.1'I, "I '"11* ''.JIlHIIIIIili!! 'fl'S'iii'ii1'',1,'!' ! Ullllllll
Ecological In^acts of Higjiways
58
April 1994
Sv'M^Mlii.'-'^'rr.lii ^:>^"''f^:V 'l-'.^/"!1:^!
'!' "i^iiHKii'J 'gR'ininiH 'HifeiiiJ1 .lii;1""!]!!!'!! V/: rJIIBII/ii'iiHaj* vli!1iliiillii|liiii!i||lLiii'Ullii:|Mi;i"1lii1i;lfl IM" ; !!(," ll,i; :l !i;s!i, ii!,,/1 ; ' "<:;' 1,1; SL illOrlV Jliifi1
-------
7. Summary of Mitigations for Ecological Impacts
The following table is a summary of the principal mitigation measures recommended for highway
impacts arising in each phase of project development (planning, design, construction, and operation)
within each of the four environmental settings (urban, suburban, rural, and wildland).
Table 4. Principal Mitigation Measures for Ecological Impacts By Phase and Setting of
Highway Development
Planning
Design
Construction
Operation
Urban
Use' alternative
transportation
options
Fence roadway
to reduce road
kills
Reduce erosion
and pollution
effects through
best management
practices
Conduct trash
removal and
ensure operation
of stormwater
controls
Suburban
Use alternative
transportation
options and select
alignment to
avoid sensitive
environments
Fence roadway
to reduce road
kills and provide
CQTHieCtivfoy of
habitat with
bridges and
underpasses
Reduce erosion
and pollution
effects through
best management
practices
Ensure operation
of design
mitigations ^^i
stormwater
controls
Rural
Select corridor
and alignment to
avoid sensitive
habitats
Provide
gOHHfl^jv|ty of
l*«»V!*«t* «v«£*V
naoitat witn
bridges and
underpasses
Apply best
management
practices and
protect sensitive
receptors' with
walls and
nonintrusive
construction
schedule
Ensure operation
of design
mitigations and
stormwater
controls and
manage roadside
for rare
communities
Wildland
Select corridor
to avoid
sensitive habitats
and control
secondary
development
Reduce roadway
footprint and
provide.
connectivity of
naoitat witn
bridges and
underpasses
Apply best
1713713 P&TTl&flf
practices and
protect sensitive
receptors with
walls and
nonintrusive
construction
schedule
Ensure operation
of design
mitigations and
stormwater
controls and
manage to
control invasion
of exotics
Ecological Impacts of Highways
59
April 1994
-------
iHllhl
1 ....... 1,1
| ...... IK
............... (in
Ecological Impacts of Highways
60
April 1994
-------
8. Bibliography
Adams, L.W. and A.D. Geis. 1981. Effects of Highways on Wildlife. Urban Wildlife Research Center
and U.S. Fish and Wildlife Service. Prepared for U.S. Department of Transportation, Federal Highway
Administration, Washington, DC. FHWA/RD-81/067.
Adamus, PJR., EJ. Clairain, Jr., RJD. Smith, and R.E. Young. 1987. Wetland Evaluation Technique
(WET). Vol. n. Methodology. U.S. Army Corps of Engineers Waterways Experiment Station,
Vicksburg, MS. 178 pp. ,
Anonymous. 1993. White Paper: Management of Weeds on Native American and Federal Natural
Resource Lands for the Purpose of Maintaining and Restoring Healthy Ecosystems. Submitted to Federal
Coordinating Committee on Science, Engineering, and Technology (FCCSET) by Federal
Interdepartmental Committee for Management of Weeds (FICMW), Washington, DC.
Bailey, R.G. 1980.. Description of the Ecoregions of the United States. U.S. Department of Agriculture,
Forest Service. Miscellaneous Publication Number 1391. 77 pp.
Baker, C.O. andFJE. Votapka. 1990. Fish Passage Through Culverts. USDA-Forest Service, SanDimas,
CA. Prepared for U.S. Department of Transportation, Federal Highway Administration, Washington,
DC.
Barrett, G.W. and PJ. Bohlen. 1991. Landscape Ecology. In: W.E. Hudson. Landscape Linkages and
Biodiversity. Island Press, Washington, DC. pp. 149-161.
Bausch, C. 1991. NEPA Integration: Effective, Efficient Environmental Compliance in the 1990s.
Proceedings of a Workshop at Hyatt. Fairlakes, Fairfax, VA.
Bedford, B.L. and E.M. Preston. 1988. Developing the Scientific Basis for Assessing Cumulative Effects
of Wetland Loss and Degradation on Landscape Functions: Status, Perspectives, and Prospects.
Environmental Management 12(5):751-771.
Bell, M.C. 1991. Fisheries Handbook of Engineering Requirements and Biological Criteria. U.S. Army
Corps of Engineers, Norm Pacific Division, Fish Passage Development and Evaluation Program,
Portland, OR.
Bohm, P. and C. Henry. 1979. Cost-Benefit Analysis and Environmental Effects. AMBIO 8(1): 18-24.
Buechner, M. 1987. Conservation in Insular Parks: Simulation Models of Factors Affecting the
Movement of Animals Across Park Boundaries. Biological Conservation 41:57-76.
Burnett, S JE. 1992. Effects of a Rainforest Road on Movements of Small Mammals: Mechanisms and
Implications. Wldtife Research 19:95-104.
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SECTION 5.2
EXAMPLE 2: ENVIRONMENTAL IMPACT
ASSESSMENT GUIDELINES FOR MINING (ORE
AND COAL)
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EIA Guidelines for Mining
Environmental Impact Assessment Guidelines
for New Source NPDES Permits
ORE Mining and Dressing
and
Coal Mining and Preparation Plants
Point Source Categories
September 1994
U.S. Environmental Protection Agency
Office of Federal Activities
401 M Street, S.W.
Washington, D.C. 20460
; 'Printed on Recycled Paper
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DISCLAIMER
This document was prepared for the U.S. Environmental
Protection Agency by Science Applications International
Corporation in partial fulfillment of EPA Contract No. 68-W2-
0026, Work Assignment 27-1. The mention of company or
product names is not to be considered an endorsement by the
U.S. Government or by the Environmental Protection Agency.
-------
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EIA Guidelines for Mining ^ Table of Contents
TABLE OF CONTENTS
1. INTRODUCTION . 1-1
1.1 PURPOSE OF ENVIRONMENTAL IMPACT ASSESSMENT GUIDELINES . . .' 1-2
1.2 SCOPE OF THE MINING INDUSTRY 1-3
1.3 ORGANIZATION OF GUIDELINES : 1-4
2. NEPA REQUIREMENTS AND PROVISIONS i , 2-1
2.1 OVERVIEW f 2-1
2.1.1 EPA REQUIREMENTS FOR ENVIRONMENTAL REVIEW UNDER NEPA 2-2
2.1.2 ENVIRONMENTAL REVIEW PROCESS FOR NEW SOURCE NPDES PERMITS 2-4
2.2 TRIGGERS FOR NEPA REVIEW ACTIVITIES . . .. 2-7
2.2.1 PRIMARY CONDITIONS THAT TRIGGER NEPA REVIEW '.'. 2-7
2.2.1.1 New Source Determination 1 ... 2-7
2.2.1.2 EPA is the. Permitting Authority . . - 2-7
2.2.2 WHEN is AN EIS REQUIRED? 2-8
2.2.2.1 Impacts to Already^degraded Environments and Cumulative Impacts ....... 2-9
2.2.2.2 Uncertain Impacts 2-11
2.2.2.3 Delayed Impacts . ; 2-12
2.2.2.4 Duration of Impacts 2-13
2.2.2.5 Transfer of Responsibility for Facility 2-13
2.2.2.6 Controversial Actions and Impacts 2-13
2.2.3 THE RELATIONSHIP BETWEEN NEPA REVIEW AND NPDES PERMITTING AcnvrnEs . -2-14
213 LEVELS OF REVIEW , 2-15
2.3.1- ENVIRONMENTAL INFORMATION DOCUMENT (EID) 2-15
2.3.2 ENVIRONMENTAL ASSESSMENT DOCUMENTS (EA) - '. 2-15
2.3.3 . ENVIRONMENTAL IMPACT STATEMENTS (EISs) 2-15
2.4 INFORMATION REQUIRED FROM PERMIT APPLICANTS 2-17
2.5 TIME INVOLVED IN PREPARING AND PROCESSING NEPA DOCUMENTS 2-17
2.6 LIMITATIONS ON PERMIT APPLICANT ACTIONS DURING THE REVIEW PROCESS . 2-17
3. OVERVIEW OF MINING AND BENEFICIATION . . . 1 . .3-1
3.1 ORE MINING 3.!
3.1.1 EXPLORATION 3-2
3.1.2 SITE DEVELOPMENT 3-3
3.1.2.1 Construction of Access Roads, Rail Lines, or Ship/Barge Terminals • 3.3
3.1.2.2 Construction of Mining Facilities : . . 3-3
3.1.2.3 Construction of Mill Facilities 3-4
3.1.2.4 Other Pre-Mining Activities 3-4
3.1.3 MINING 3.4
'3.1.3.1 Surface Mining 3.5 "
3.1.3.2 Open Pit Mining 3-5
3.1.3.3 Dredging 3.5
3.1.3.4 Underground Mining 3-6
3.1.3.5 In Situ Solution .Mining : 3-g
3.1.4 MINING WASTES AND WASTE MANAGEMENT ;.. 3-9
3.1.4.1 Mine Water 3-9
3.1.4.2 Waste Rock 3-10
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Table of Contents' • EIA Guidelines for Mining
3.1.5 RESTORATION AND RECLAMATION ............"'.... I 3-11
' 3.2 ORE DRESSING (BENEFICIATION) . . '. . ', 3-13
3.24 GRAVITY CONCENTRATION , \. . 3.13
3.2.1.1 Sizing . . .. . . .... . . . . . . . . . . . ._\ ,. . f ,^ . r . . 3_14
3.2.1.2 Coarse Concentration n 3-15
1 3.2.1.3 Fine Concentration . . . . s-ig
3.2.1.4 Sink/Float Separation . .'".' . . \ . ". . S-ig
3-2-2 ^ASKSKSSABffiff. ». el« -• ™.i'r f. , •"• • •• • ._.'... ,_,..*,.,., i...,: ,-, 5-18
3.2.3 ELECTROSTATIC- SEPARATION •- 3-19
3.2.4 FLOTATION. 3-19
3.2.5 LEACHING .:...... 1.......,".'. 3-20
3.2.6 BENEHCfATION WASTES AND WASTE MANAGEMENT 3-22
3.2.6.1 Mine Backfilling ...... ."". .".'" 1.". .' '. IT .'.". .".". .". .".'. . . •; 3-23
3.2.6.2 Subaqueous Disposal . 3-24
3.2.6.3 Tailings Impoundments ' 3-24
3.2,6-4 Dry Tailings Disposal . ." 3-28
3.3 COMMpprr^^PECIFIC MINING AND BENEHCIATKW PROCESSES . 3-29
3.371 GOLD ANb~Sn.vBt.."' ..:......".".'."."... :".'.....'.. 3-29
3.3.1.1 Geology of Gold Ores 3.39
3.3.1.2 Mining ; 3-34
i ..•.. '-••.- 313.1.3 Beneficiation • ' 3.37
3.3^ GOLD PLACER MINING 3.55
3.3.2.1 Mining ; 3-58
3.3.2.2 Beneficjation ._..._._. ..._.. .._.... ._.... ._. ._. ... , .,.„,,„, ,,„,. . . 3-59
3.3.2.3 Wastes and Management Practices . . . .' 3-60
3.3.2,4; Environmental Effects .• ' 3^2
- 3.3.3 LEAD-ZINC ".'* .......... 3-63
3.3.3.1 Mining .". .'. .'. ". .T.'. . .'. .'.'".'.".'.". ""."".. I'. ! i'.-T .". ."". . ."'.".'. 3-64
3.3.3.2 Beneficiation 3-64
3.3.3,3 Wastes '. . ,.....[... 3-66
3.3.3.4 Waste Management 3.57
3.3.4 COPPER '.'.'.'.'. 3-69
3.3:4.1 Geology of Copper Ores 3-69
3.3.4.2 Mining 3_7j
3.3.4.3 Beneficiation " !!!!!!!!!!!! 3-71
3.3.4.4 Wastes and Waste Management " 3.30
3.3.5 IRON , !.'!!!!!!."'.'.'.'.'.'.'.'. 3-82
3J.5.1 Geolpgy.of Iron Ores 3.33
3.3.512 Mining . .- '.I'.'.'.'.'.'.'.'. 3-83
" 3.3.5.3 Beneficiation !!!!.!!!.! 3-84
33^.4 Wastes and Waste Management 3-87
3.3.6 URANIUM , !....!.!..!..!! 3-88
3.3,6.1 Cjeolpgy of Uranium Ores " " 3.38
3.3.6.2 Mining ; ','.'.[ 3-89
3.3.6,3 Beneficiation 3-go
in in n in i i ii ii MIIII in 11 n '"** M f M -rrr _* «»» «•.' • *• ""*"*•""•*•••••" ••? oy
3.3.6.4 Wastes and Waste Management - 3.95
33.7 OTHER METALS ." '.'. '. I ."".". '.'.'.'.'.'.'.'.'.'.'.'.'.'.I'.'.'.' 3-97
3.3.7.J Aluminum 3.97
. 3.3.7.2 Tungsten . ".' ."". . . '.'", ','", , . . .............. 3.93
3.3.7.3 Molybdenum .............[.[.] 3-99
3.3.7.4 Vanadium '. ..'.... 3-100
313.73 Titariium ". .'.'". .'.". ""." ".",".".". '.' ~.'.".. '.''. ' ".'. '. . ......... 3-100
3.3.7.6 Platinum 3 IQI
Al'_COAL MINING '. I M".1 ;". ...!!!!!!!!!!!!!!!!!!!!!!!!!!! 3-102
3.4.1 COAL FORMATION AND GEOGRAPHICAL DiSTRmtmoN ..'.'.'. 3-102
3.4.1.1 Types and Composition of Coal [ 3-102
i
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EIA Guidelines for Mining . Table of Contents
3.4.1.2 Coal Provinces ....... 3-103
3,4.1.3 Trends . . . . . 3-108
3.4.2 SURFACE MINING SYSTEMS 3-109
3.4.2.1 Area Mining . 3-109
3.4.2.2 Contour Mining 3-112
3.4.2.3 Open Pit Mining 3-115
3.4.2:4 Special Handling . . . -. 3-116
3.4.2.5 Equipment 3-116
3.4.3 UNDERGROUND MINING SYSTEMS 3-116
3.4.3.1 Development 3-117
•3.4.3.2 Extraction- 3-118
3.4.3.3 Abandonment 3-123
3.4.3.4 Pollution Control . 3-124
3.4.3.5 Environmental Effects 3-125
3.5 COAL PROCESSING 3-125
3.5.1 BASIC PRINCIPLES 3-125
3.5.2 COAL CLEANING TECHNOLOGY , . 3-132
3.5.2.1 Stage Descriptions 3-137
3.5.2.2 Process Flow Sheet for Typical Operations . .~. 3-150
'
4. ENVIRONMENTAL ISSUES 4-1
4.1 ACID ROCK DRAINAGE ". . .4-2
4.1.1 NATURE OF Aero ROCK DRAINAGE 4-3
4.1.1.1 Acid Rock Drainage/Oxidation of Metal. Sulfides . 4-3
4.1.1.2 Source of Acid and Contributing Factors 4r4
4.1.2 ACID GENERATION PREDICTION ... 4-7
4.1.2.1 Sampling . . 4-9
4.1.2.2 Static Tests 4-11
4.1.2.3 Kinetic Tests. 4-12
4.1.2.4 Application of Test Results in Prediction Analysis 4-14
. 4.1.2.5 Experience With Static and Kinetic Tests 4-16
4.1.2.6 Mathematical Modeling of Acid Generation Potential . 4-17
4.1.3 ARD DETECTION/ENVIRONMENTAL MONITORING 4-21
4.1.4 MITIGATION OF ARD . 4-22
4.1.4.1 Subaqueous Disposal 4-23
4.1.4.2 Covers i 4-24
4.1.4.3 Waste Blending .- 4-24
4.1.4.4 Hydrologic Controls 4-24
4.1.4.5 Bacteria Control 4-25
4.1.4.6 Treatment 4-25
4.1.5 SUMMARY OF FACTORS TO BE CONSIDERED IN EVALUATING POTENTIAL ARD
GENERATION/RELEASE ...: : 4-27
4.2 CYANIDE HEAP LEACHING . . 4-28
4.2.1 UNCERTAINTIES IN CYANIDE BEHAVIOR IN THE ENVIRONMENT 4-29
4.2.1.1 Cyanide in the Environment J ; 4-29
4.2.1.2 Analytical Issues 4-30
4.2.2 POTENTIAL IMPACTS AND APPROACHES TO MITIGATION DURING ACTIVE LIFE 4-31
4.2.2.1 Acute Hazards 4-32
4.2.2.2 Spills and Overflows .- ; 4-32
4.2.2.3 Liner and Containment Leakage : 4-34
4.2.3 CLOSURE/RECLAMATION AND LONG-TERM IMPACTS 4-35
4.2.3.1 Closure and Reclamation 4-35
4.2.3.2 Long-term Environmental Concerns and Issues • 4-36
4.2.3.3 Assessments of Long-term Impacts 4-38
September 1994
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<£ Contents ""' """' ' '"• ' '' ' "" '"' ''"" EIA ''
4.3 STRyCjnLERAL^T.ABILrrY.pF TAJLJNGAMTOUNDMENTS ' 4-39
4.3.1 SEEPAGE AND STABILITY 4-40
43.2 SEEPAGE/RELEASES AND ENVIRONMENTAL PERFORMANCE 4-42
• 4.4 NATURAL RESOURCES AND LAND USES !'."."!!. 4^3
4.4.1 GROUNDWATER 4-43
4.4.2 AQUATIC LIFE '. .•.',"". 7V.,, *"'*.'...... '.".' '". ."".1 .". ~'."".' 7."..' . ]"". '4^44"
4.4.3 WILDLIFE *..,,...........!.. 4-47
' ' """ """' ;"' ""i::: :'4AA". VEGETATION/WETLANDS 7".'..". ."7"! I.:.'. .'"."; ™,".~.'~. '.' ".".':.'. .' 4.50
4.4.5 . LAND USE 4-52
4.4.5.1 Farmland 4-52
4,4.5.2 Timber ' 4.53
•4.4.53 Grazing 4.53
4.4.5.4 Recreation , ; 4.54
4.4.6 CULTURAL RESOURCES , 4.54
4.4,7 .AESTjHETICS .".... ,.. . . . .„.,.,. . .• 4.54
4.5 SEDIMENTATION/EROSION . . 4.35
4.5.1 BASIC EROSION PRINCIPLES ,. r 4-56
4.5.2 IMPACTS ASSOCIATED WITH EROSION/RUNOFF FROM DISTURBED AREAS ......... 4-58
4.53 ESTABLISHING BACKGROUND CONDITIONS 4-58
4.5.4 PREDICTING SEDIMENT LOADINGS FROM NEW SOURCES .......... 4-61
4.5.4,1 Available Techniques/Model? 4-62
,4.5.4.2 Modeling Considerations . . _v. . r..'..^.._'.."r"~'.-'-.~'i!I.V.."...... -'I'•,',•""•"•',»..' 17". "4*63
4.5.5 _ SEDIMENT AND EROSION MITIGATION MEAsin^'T.'. .",1',,' i I .'.". 7'. 77.".'."...".""'. 4-64
""4.5.5.1 Diversion Techniques ........ '....,..'. 4-65
4.5.5.2 Stabilization Practices 4-65
4.5.53 Structural Practices .._... ..^. , ._. .,. ^ R, v. , 4-66
4.5.5.4 Contact Prevention Measures/Reclamation Process . 4-66
• 4.5.5.5 Treatment Techniques . ; 4-69
4.6 METALS AND DISSOLVED POLLUTANTS 4-69
. 4.7 AIR QUALITY / .".". ". ". I 7.\ \'". 7.'.". ' ; " ' *""" "' 4.73
4.8 SUBSIDENCE i ..,!.!!."!!•!!.'.*." 4-74
4.9 METHANE EMISSIONS FROM COAL MINING AND PREPARATION ...... . . . . . . 4-75
,,,!," I",' I "," : :,' :; n " " ",", .*..." ,.
I i^j y-^^,,^j™«^ -^ .^..- --..^ ^ ^ -... ^ - ^ -^ ^ ,-.^.-,~ , , ,.., - ,,- , ^ ......... , ^
.........
I
, 5.1 DETERMINE THE SCOPE OF ANALYSIS ..... 5-1
5.2 IDENTIFY ALTERNATIVES '.. I. .'.I . . .'.".". . . V I'.'.'.'.'.'.'.'.'.'.'.'. 5-2
5.2.1 ALTERNATIVES AVAILABLE TO EPA 5-3
5.2.2 ALTERNATIVES CONSIDERED BY THE APPLICANT 5-3
5.23 ALTERNATIVES AVAILABLE TO OTHER AGENCIES 5-4
S3 DESCRIBE THE AFFECTED .ENVIRONMENT .'.'.'.'.'.'.'.'.'. 5-4
53.1 THE PHYSICAL-CHEMICAL ENVIRONMENT 5-5
5.3.1.1 Air Resources . : [\[ 5.5
53.1.2 Water Resources . .". ..^. 5-6
53.13 Soils and Geology 5-7
5.3.2 BIOLOGICAL CONDITIONS 5-8
53.2.1 Vegetation 5-8
53.2.2 Wildlife . 5-8
53.23 Ecological Interrelationships 5.9
533 SOCIOECONOMIC ENVIRONMENT '.'.'.'.'.'.'.''.'.'.'.'. 5-9
53.3.1 Community Seryices 5-9
533.2 Transportation'."..""". . . .. "."". . . . ...'"!, '. '."". . .""."..'.".". '. 5-10
5333 Population ........... 5-10
5.3.3.4 Employment ',-, ,.... 5-10
533.5 Healthand]Safity".""."r'."^ .".". ."7-7."'. . ."". 7.\ I"!"! '. . ]"""'""'"! '.'.'.'.'.'.'.'. 5-11
53.3.6 Economic Activity 5_U
(ii ' ^ ^l^1' '"' ^ ;" i(: ^ ^/^ ir ' ij. '
iv September 1994
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EIA Guidelines for Mining _ _ Table of Contents
5.3.4 LAND USE ..... ..................................... ..... 5-1 1
5.3.5 AESTHETICS ....... . ...................................... 5-11
5.3.e GUTTURAL RESOURCES ......................... 5-12
5.4 ANALYZE POTENTIAL IMPACTS ........... . .......... .... ..... .'..." 5.12
5.4.1 METHODS OF ANALYSIS ........................... . .......... 5-13
5.4.2 DETERMINATION OF SIGNIFICANCE ................................ . 5-14
5.4.3 COMPARISONS OF IMPACTS UNDER DIFFERING ALTERNATIVES ............... 5-16
5.4.4 SUMMARY DISCUSSIONS .................... , ........ 5-16
5.5 DETERMINE MITIGATING MEASURES .................... ........ 5-17
5.6 CONSULTATION AND COORDINATION .......... '. .................... 5-18
6. STATUTORY 'FRAMEWORK
6.1 CLEAN WATER ACT ................................ 6-1
6.2 CLEAN AIR ACT ......................... ...... ........ * " 6-15
6 3 RESOURCE CONSERVATION AND RECOVERY ACT ...... .......... 6-17
6.4 ENDANGERED SPECIES ACT ........... . . . ; ....... .......... 6-19
6.5 NATIONAL HISTORIC PRESERVATION ACT . ........... . ......... ... 6-20
6.6 COASTAL ZONE MANAGEMENT ACT ................................ 6-21
6.7 EXECUTIVE ORDERS 11988 AND 11990 ...................... 6-21
6.8 FARMLAND PROTECTION POLICY ACT ....... . : ........... 6-22
6.9 RIVERS AND HARBORS ACT OF 1899 ........................ 6-22
6.10 SURFACE MINING CONTROL AND RECLAMATION ACT .................. . 6-23
6.10.1 PERMITTING PROGRAM FOR ACTIVE COAL MINING OPERATIONS ......... ..... 6-23
6.10.2 ABANDONED MINE LANDS PROGRAM .................. 6-25
6.11 MINING LAW OF 1872 .................................... : " 6-26
6.12 FEDERAL LAND POLICY MANAGEMENT ACT . . / .......... ........ ..... 6-27
6.13 NATIONAL PARK SYSTEM MINING REGULATION ACT ____ ........ 6-29
6.14 ORGANIC ACT; MULTIPLE USE AND SUSTAINED YIELD ACT; NATIONAL FOREST
MANAGEMENT ACT .......................... ... ........... 6-30
6.15 MINERAL LEASING ACT; MINERAL LEASING ACT FOR ACQUIRED LANDS ". '. '.'. '. '. 6-30
6.16 COMPREHENSIVE ENVIRONMENTAL RESPONSE, COMPENSATION, AND LIABILITY
ACT ................................... .................... 6-31
6.17 EMERGENCY PLANNING AND COMMUNITY RIGHT-TO-KNOW ACT .. 6-32
6.18 WILD AND SCENIC RIVERS ACT ............................... ] " : 6-32
6.19 FISH AND WILDLIFE COORDINATION ACT .............. ........ 6-33
6.20 FISH AND WILDLIFE CONSERVATION ACT ......... . * 6-33
6.21 MIGRATORY BIRD PROTECTION TREATY ACT ..................... '.'.'.'. 6-33
7. REFERENCES
September 1994
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Table of Contents
EIA Guidelines for Mining
- • •• LIST OF EXHIBITS
Exhibit - Page
Exhibit 1-1. Standard Industrial Classification Codes for the Metal Mining Industry 1-4
Exhibit 2-1. NEPA Environmental Review Process for Proposed Issuance of New Source
NPDES Permits , . . , .„.,„,„„,„,„„, ,„„,,.-. .' 2-5
Exhibit 2-2. Model Schedules for EAs and EISs for Proposed Issuance of New Source " ' ' '
NPDES Permits . 2-18
. Exhibit 3-1. Twenty-Five Trading Gold-Producing Mines hi the United States, 1991 3.31
Exhibit 3-2. Twenty-Five Leading Silver-Producing Mines in the United States, 1991 . . . . . . . . . . . 3-32
Exhibit 3-3. Materials Handled at Surface and Underground Gold Mines, 1988 3.34
.Exhibit 3-4. Chemicals Stored and Used at Gold Mines •..'."!.'.".".'!.'." 3-36
Exhibit 3-5. Gold Mining and Beneficiation Overview '.'.'.'.'.'.' 3-38
Exhibit 3-6. Gold Ore Treated and Gold Produced, By Beneficiation Method, 1991 . . . . . . . '.'.'.'. '. '. 3-39
Exhibit 3-7. Steps for Gold Recovery Using Carbon Adsorption 3_42
Exhibit 3-8. Chemicals Used at Lead-Zinc Mines ..........!....].... 3-68
Exhibit_34>, Leading Copper Producing Facilities in the United States 3-70
Exhibit 3-10. Copper Flotation Reagents !!....!.!.!....... 3-72
Exhibit 3-11. Characteristics of Copper Leaching Methods .............. 3.74
Exhibit 3-12. Typical Solvent Extraction/Hectrowinning (SX/EW) Plant . . . . . . . '.'.'.'. '. ...... 3-78
Exhibit3-13, Types of Coal and Relative Percentages of Constituents ... :•••••
Exhibit 3-14. Coal Provinces, of the United States !.'."!.".'.'].'!'*"" 3-104
^x^|i.l~ll,: Summary of Environmental Considerations by Province ' 3 IDS
Exhibjs 3-16. Area Mining With Stripping Shovel ].*.".' 3_!10
Exhibit 3-17. Moantaintop Removal With Head-of-Hollow Fill slin
Exhibit 3-18. Box-Cut Mining Operations ' 3 113
Exhibit 3-19. Block-Cut Mining Operation '.'.'.'.'.'.'.'.'.'.'.'.'.'.'.'.'.'.'.'.'.'
Exhibit 3-20. Operations in Conventional Room and Pillar Mining
Exhibit 3-21. Longwall Mming System .".'.'
Exhibit 3-22. Ash and Sulfur Reduction Potential of U.S. Coals] Vol. I p. 395, Eastern
Regions U.S. Department of Energy .... •» 1
Exhibjt3-23. Washability Partition Curve 3"}
Exhibit 3-24. Coal Preparation Plant Processes 3"13-.
Exhibit 3r25, Typical Coal Cleaning Facility' '.'.'.'.'. 3.134
Exhibit 3-26. Typical Circuit for Coal Sizing Stage ...!!!!...!....%/!!..!!! 3-135
Exhibit 3-27. Metric and English Equivalents of U.S. Standard Sieve Sizes and Tyler Mesh
Sizes ' -i fid
E^^itS^S. Ty^ic^i Soce^ Qua^^ for a^oi^a(»b"T)Ver HouV"Q)al CleaninV
Facility * 3 13_
Exhibit 3-29. Typical Three-Stage Crusher System for Raw Coal Crushing " " " " 3-138
Exhibit 3-30.. Single-Roll (a) and Double-Roll (b) Crushers for Sizing of Raw Coal 3-139
Exhibit 3-31. Feed Characteristics of Unit Cleaning Operations for Sizing and Separation of
Cijusfaed Coal , 141
Exhibit 3-32. Typical Circuit for Dense Media Coal Cleaning 3~142
Exh|b|t 3-33. Typical Circuit for Jig Table Coal Cleaning 3 144
Exhibit 3-34. Typical Air Table for Pneumatic Coal Cleaning !.!....!.!!. 3^45
Exhibit 3-35. Typical Circuit for Pneumatic Coal Cleaning '.'.'. 3-146
Exhibit 3-36. Desirable Chemical Characteristics of Make-Up Water for Coal Cleaning
Processes 3 147
Exhibit 3-37. Typical Product Dewatering Circuit for Coal Cleaning ".'.'.'.'.'.'.'.'.'.'.'.'.I'.'.'.'.'.'.'.'. 3^48
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VI
September 1994
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EIA Guidelines for Mining
Table of Contents
Exhibit 3-38. Typical Moisture Contents of Dried Product from Selected Drying Operations
in Coal Cleaning Facilities ; 3-149
Exhibit 3-39. Thickener Vessel for Dewatering of Coal Cleaning Products 3-150
Exhibit 3-40. Schematic Profile of a Sieve Bend Used for Coal Sizing and Dewatering 3-151
Exhibit 3-41. Profile View of a Coal Vacuum Filter 3-152
Exhibit 3-42. Thermal Dryer and Exhaust Scrubber . . . 3-153
Exhibit 3-43. Typical Flash Dryer , 3-154
Exhibit S--44. Coal Cleaning Plant Flow Sheet for Coarse Stage Separation and Dewatering . . '. 3-156
Exhibit 3-45. Coal Cleaning Plant Flow Sheet for Fine Stage Separation and Dewatering . . . ; 3-157
. Exhibit 3-46. Coal Cleaning Plant Flow Sheet for Sludge (Slime) Separation and Dewatering 3-158
Exhibit 4-1. Summary of Static Test Methods, Costs, Advantages, and Disadvantages . . : 4-13
Exhibit 4-2. Summary of Some Kinetic Test Methods, Costs, Advantages, and Disadvantages 4-15
Exhibit 4-3. Stability of Cyanide and Cyanide Compounds in Cyanidation Solutions : 4-30
Exhibit 4-4. Typical Pollutants Associated With Hardrock Mining Operations 4-71
Exhibit 4-5. Typical Pollutants Associated With Coal Mining Operations 4-72
Exhibit 6-1. Major Federal Statutes Generally Applicable to Mining Operations 6-2
Exhibit 6-2. New Source Performance Standards for Coal Mining Category
(40 CFR Part 434) 1 6-9
Exhibit 6-3. New Source Performance Standards for Mine Drainage, Ore Mining and
Dressing Category (40 CFR Part 440, Subparts A-K and M) 6-10
Exhibit 6-4. New Source Performance Standards for Mills and Beneficiation Processes, Ore
. Mining and Dressing Category (40 CFR Part 440, Subparts A-K and M) . 6-",.'.
Exhibit 6-5. Examples of Discharges From Ore Mining and Dressing Facilities
That Are Subject to 40 CFR Part 440 or to Storm Water Permitting c-.
VII
September 1994
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Guidelines for M"""g _ _ __ _ Introduction
1. INTRODUCTION
The National Environmental Policy Act of 1969 (NEPA, 42 U.S.C §4321 et seq.) was the first of
what has come to be an array of statutes whose individual and collective goals are the protection of
the human and natural- environment from a variety of impacts that human activity can have. NEPA
introduced the requirement that Federal agencies consider the environmental consequences of their
actions and decisions as they carry out then* mandated functions.. For "major Federal actions
significantly affecting the quality of the human environment," the Federal agency must prepare a
detailed environmental impact statement that assesses not only the proposed action but also reasonable
alternatives.
The Federal Water Pollution Control Act (33 U.S.C. §§1251-1387), better known as the Clean Water
Act, seeks to restore and maintain the chemical, physical, and biological integrity of the Nation's
waters. One of the major mechanisms by which the Clean Water Act is to attain that goal is the
requirement that all point source discharges of pollutants to waters of the United States be controlled
through permits issued under the National Pollutant Discharge Elimination System (NPDES).
*
The Clean Water Act [§51 l(c)(l)] also requires that the issuance of a NPDES permit by the
Environmental Protection Agency (EPA) or authorized States for a discharge from a new source be
subject to NEPA. In 1979, EPA established the regulations by which it applies NEPA in such cases:
"Environmental Review Procedures for the New Source NPDES Program," 40 CFR 6 Subpart F.
These procedures require EPA to prepare a written environmental assessment based on information
provided by the new source NPDES permit applicant and other available documentation. If the
environmental assessment concludes that no significant impacts will result from issuance of the new
source NPDES permit, EPA issues a Finding of No Significant Impact (FNSI). If the assessment
concludes that there may be significant environmental impacts that cannot be eliminated by 'changes hi
.the proposed project, EPA must prepare (or participate hi the preparation of) an environmental impact
statement that contains the information and analyses described in 40 CFR Part 6 Subpart B and
conforms with Council on Environmental Quality regulations (40 CFR Part 1502) governing NEPA
compliance. •
In preparing the environmental assessment, EPA relies on information and analyses provided by the
applicant for the new source NPDES permit in an "environmental information document," or EID.
The scope and content of an EID is determined by EPA hi consultation with the applicant, with the
regulatory caution that EPA "...keep requests for data to the minimum consistent with his
responsibilities under NEPA" [40 CFR 6.604(b)].
1_1 September 1994
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*ntrodnctlon EIA Guidelines for Mining
1.1 PURPOSE OF ENVIRONMENTAL IMPACT ASSESSMENT GUIDELINES
Following the promul|ation of New Source Performance Standards for new source discharges in the
late 1970s and early 1980s, EPA prepared a series of "Environmental Impact Assessment Guidelines"
for W in determining the scope and consents of HDs for new source, NPDES. permits for •facilities in
specific'industries. The guidelines also were intended to assist EPA staff in reviewing and
commerSng on applicants' BID information and in preparing, overseeing the preparation of, or
commenting on environmental assessments and environmental impact statements
I ' . '"Ill"" 'I*1 I ' '•I"" I" I'1 sed ffijg 2*$^ 5?y have. Because many of the potential impacts, and the information and
analysts needed to assess impacts* are common to metal and coal mining me topics covered by the
three 3™™*® guidelines documents have been combined into this single document.
'
These guidelines are expressly intended to provide background information for EPA staff to assist
tfa*m'ln consulting with and directing new source NPDES permit applicants in the- scope and contents
of E[£>s *??_ !? * 55!???!10? !° ?5?!5! H«S M .Modifying and evaluating the potential impacts of
JfS^ ..... 5^21 ..... E25S: ............... i£i ...... SSEStes ...... several ...... oto audiences ...... for .these guidelines: EPA staff
^° r?fi!!! ...... — ...... SS^ ....... 2n,.5te5^5»L!ffi?^i' ..... ?m^onmen|al.|inpact statements and regulations
pursuant to §309 of the Qean Air Act; other EPA staff who deal with the ruining industry and its
eavfronmental JBpactsj gew.sonoe. NPOES permit applicants who must prepare EIDs for EPA; other
Federal agencies responsible for regulating or overseeing the mining industry; and State, local, and
foreign government environmental officials. Officials in States tha| hayesfeeen authorized to
m5)1
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EIA Guidelines for Mining ^ Introduction
These guidelines supplement the more general document, Environmental Impact Assessment
Guidelines for Selected New Source Industries, which provides general guidance for preparing
environmental impact assessments (EIAs) and presents impact assessment considerations that are
common to most industries,- including mining.
1.2 SCOPE OF THE MINING INDUSTRY
The ore mining and dressing (or beneficiation) industry is composed of mining facilities that remove
raw mineral ores from the earth, and of mill facilities that separate the mineral ores from overburden
and waste rock removed during mining activities. The industry also includes mill facilities that
further concentrate and purify metals in the ore to a condition specified for further processing
(smelting and/or refining) or for incorporation as a raw material by another industry. The mining and
beneficiation of various mineral ores occurs nationwide, and is viewed as critically important to the
Nation's economy since it provides the raw materials on which many other industries rely.
The metal mining industry is identified as Standard Industrial Classification (SIC) Major Group 10.
This industrial.group includes facilities engaged in mining ores for the production of metals and also
includes all ore dressing (or beneficiation) operations, whether performed at mills operating in
conjunction with mines or at mills operated separately. These 'include mills that crush, grind, wash,
dry, sinter, or leach ore, or that perform gravity separation or flotation operations.
EPA has promulgated effluent limitation guidelines for discharges of pollutants from existing and new
sources hi the Ore Mining and Dressing Point Source Category (40 CFR Part 440). These effluent
limitation guidelines provide numeric limitations for discharges from mines and mffls in various
industry subcategories (see also Chapter 5). Exhibit 1-1 shows the SIC categories covered by this
industrial group and the subcategories for which EPA has promulgated effluent limitation guidelines.
The coal mining industry is composed of facilities that mine coal of any rank from the earth, and of
preparation plants that clean or otherwise prepare the coal for combustion and other uses, the coal
mining industry is identified as Standard Industrial Classification (SIC) Major Groups 11 (anthracite)
and 12 (bituminous and lignite). These industrial groups include facilities that are engaged in mining
coal and preparation plants that operate in conjunction with mines or separately.
EPA has promulgated effluent limitation guidelines for discharges of pollutants from existing and new
sources in the Coal Mining and Preparation Plant Point Source Category (40 CFR Part 434). These
effluent limitation guidelines provide numeric limitations on discharges from mines (with separate
standards for acid and for alkaline discharges), preparation plants, and areas of mines that are being
reclaimed.
1-3 September 1994
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Introduction
EIA Guidelines for Mining
In hill
1"
Exhibit 1-1. Standard Industrial Classification Codes for the Metal Mining T^HMC^.
SIC
1011
1021
1031
1041
1044
1051
1061
1092
1094
' 1099
Type of Ore .
Iron Ores
CopperOres
Lead and Zinc Ores
Gold Ores •
Saver Ores
Bauxite and Other Aluminum Ores
Ferroalloy Ores, except Vanadium
Mercury Ores
Uranium, Radium, and Vanadium Ores
Other Metal Ores
Subpait Within 40 CFR Part 440
Subpart A
Subpart J
Subpart J
Subpart J (lode)
Subpart M (placer)
Subpart J
Subpart B
Tungsten: Subpart F
Nickel: Subpart G
Molybdenum: Subpart J
Subpart D
Subpart C
Subpart H (vanadium when mined
alone— reserved)
Antimony: Subpart I
Plathmm: Subpart K (reserved)
Titanium: Subpart E
•—•—•••••••••••I '
•
13 ORGANIZATION OF GUIDELINES
The remainder of this document is organized as follows. Chapter 2 describes NEPA requirements
and Provisions as they apply to issuance of new source NPDE§ permits. Chapter 3 presents
...... ^SSSiiffliSS ..... Miff mdustty- This ...... chapter is intended to give the reader background
information on the operations that take place on mine sites. The apparent simplicity of mining--
amoving OI^ .^5.^?..^*^B* *f? 5™?5;!!3S to* valuable product from the ores— disguises
what *f m I^&£fi™^^OTpi^yi ........... As ...... a ..... result, ...... some ...... understanding of the nature of mining
operations is necessary in any assessment of the potential environmental impacts and in identifying the
infonnationiradaiialyses that are Metal minuig and
beneficianon arc described in the first three subsections of Chapter 3. The first two describe,
operations that are common to the industry; the third describes
«•* rf_*?. SBJor Industry sectors, with particular regard to the mining and beneficiation operations
that are unique to the individual sector. This third subsection focusses on the industry sectors which
are most important to the U.S. mining industry, including gold, copper, iron, lead-zinc, and uranium.
1-4
September 1994
in ,1
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EIA. Guidelines for Mining Introduction
Sectors for which EPA has promulgated effluent limitation guidelines but in which there are currently
very few active mines (e.g., aluminum, molybdenum, platinum, tungsten) or no active or anticipated
mines (e.g., antimony, mercury) are also.described, but hi less detail. Following the subsections on
metal mining are two subsections that describe coal mining and coal preparation, respectively.. All of
the subsections in this chapter describe the major operations that take place and identify the major
environmental concerns of these operations.
Chapter 4 then describes in some detail several of the major environmental issues and impacts that are
of most concern when evaluating the potential major impacts of proposed mining operations.
Separate subsections hi this chapter describe each of a number of major potential impacts and the
circumstances that can lead to their occurrence. These sections also describe the types of information
and analyses that are necessary to identify whether these impacts are of concern for a particular
operation, to evaluate these potential impacts and then* significance, and to identify and evaluate
possible mitigation measures.
The process of analyzing impacts within the context of NEPA and new source NPDES permits is
described in Chapter 5. Separate subsections describe each of the major steps hi the impact analysis.
Chapter 6 then provides information on the major Federal environmental and natural resource
management statutes that directly affect or that regulate mining operations. The purposes and broad
goals of each of these statutes are described, along with a brief indication of the requirements
imposed by the statute and the^implementing agency's regulatory or consultation programs.
Finally, references cited hi the document are listed hi Chapter 6, as are a number of other valuable
references. Appendix A presents an outline, in the form of a "checklist," of the types of information
and analyses that should go into an environmental information document. Appendix B presents a
glossary of terms.
1-5 September 1994
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EIA. Guidelines for Mining ^ NEPA Requirements and Provisions
2. NEPA REQUIREMENTS AND PROVISIONS
2.1 OVERVIEW .
NEPA serves as the basic national charter for environmental protection. Section 102 of NEPA
establishes environmental review requirements for Federal actions. These reviews or impact
assessments are required to be broad in scope, addressing the full range of potential effects of a
proposed action on the human and natural environment. A general framework for implementing these
requirements is presented in regulations issued by the Council on Environmental Quality (CEQ).
Federal agencies, in turn, have developed their own rules for NEPA compliance that are consistent
with the CEQ regulations but address then* specific missions and program activities. Over the past 25
years, the NEPA framework for environmental review of proposed Federal actions has been
substantially refined, based on further congressional directives, action by CEQ, and an .extensive body
of case law.
Congress has determined that most EPA activities are exempt from impact assessment requirements
under NEPA. In the case of EPA's water quality programs, Section 511(e) of the Clean Water Act
(CWA) clearly specifies that actions taken by EPA under the Act shall not "be deemed a major
Federal Action significantly affecting the quality of the human environment within the meaning of the
National Environmental Policy Act of 1969." However, Congress did make two important exceptions
to this exemption:
(1) the provision of financial assistance for the construction of publicly owned treatment works
(2) the issuance of NPDES permits for new sources as defined hi Section 306 of the CWA.
The specific reference to NPDES new source permits makes clear EPA's responsibility to review
proposed permit issuance actions from the broader perspective of the NEPA environmental assessment
framework.
Since EPA does have responsibility for conducting environmental reviews for some types of proposed
activities, the Agency has developed and codified its own set of NEPA procedures. These
procedures, which are found at 40 CFR Part 6, have been revised a number of times. Some of the
relevant steps in the course of the development of EPA's current regulations are as follows:
• Initial EPA proposed rulemaking setting forth procedures for the preparation of EISs (37 FR
879; January 20, 1972)
• Interim EPA regulations for Part—Preparation of Environmental Impact statements (38 FR
1696; January 17, 1973)
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••1
NEPA Requirements and Provisions KTA Guidelines for Mining
• Notice of proposed rulemaking—Preparation of EISs (39 FR 26254; July 17, 1974). This
proposed rulemaking reflects substantial public comment on the interim regulations as well
as additional CEQ requirements. The rulemaking addresses EPA's nonregulatory programs
only. •
••'.•"
• ' Final EPA regulations on the preparation of Environmental Impact statements (40 FR •
16814, April14,1975). Althoughprocedures for new source NPDES permits are not
'included"uTthis rulemddiiigTgp^ ^^in the'preamble that such regulations will be
subsequently issued in 40 CFR Part 6.
•' , . , - v • , . . . •• j • . ^ . : '
• Preparation of Ifovfronrnental Impact Statements, New source NPDES permits (42 FR 2450,
J^anuarj 11, 1977). Presents an outline for the preparation of EISs for proposed new source
permitting action.
i ..'.•.
* Proposed rule—Implementation of Procedures on the National Environmental Policy Act (44
FR 35158; June 18, 1979). In response to major revision of CEQ's regulations in 1978,
EPA revises its procedures accordingly. The revised procedures include streamlining and
clarification of procedures in general. In addition, requirements for NPDES new source
permitting actions were substantially revised and presented as Subpart F of the proposed
rule., ' • • • ','.''
• Final rule—Implementation of Procedures on NEPA (44 FR 64174, November 6, 1979).
Issues raised during promulgation include limitation of construction activities during
permitting process and environmental review and the conditioning .or denying or permits
.based on factors identified during the NEPA review process.
i . •.-......,, . |
* Minor changes to Subpart F,. involving die changing of citations, were made on September
' 12, 1986 (51 FR 32606). "
2.1.1 EPA REQUIREMENTS FOR ENVIRONMENTAL REVIEW UNDER NEPA
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EPA's current National Environmental Policy Act Procedures (40 CER 6) outline the Agency's
policies and processes for meeting environmental review requirements under NEPA. Subpart A of
&& Procures provides/an overview of the Agency's purpose and policy, institutional responsibilities,
and general procedures for conducting reviews. Subpart A outlines EPA's basic hierarchy of NEPA
compliance documentation as follows:
• Environmental Information Document (ETO), which is a document prepared by
applicants, grantees, or permittees and submitted to EPA. This document must be sufficient
in scope to enable EPA to prepare an environmental assessment.
'* ;: SliFJiil^ial J^essjnent (EA), which is a concise document prepared by EPA that
provides sufficient data and analysis to determine whether an EIS or finding of no
gignpcan^impact is required.
IllljIH I i i HIP1 IjllliU -
I!5S' "'!' „'!'!? "i Sl'^n'SpffiiS intent 'to p:repare '^"^ ~
which is published in the Federal Register, reflects the Agency's finding that the proposed
2-2 September 1994
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E1A. Guidelines for Mining/ NEPA Requirements and Provisions
action may result in "significant" adverse environmental impacts and that these impacts can
not be eliminated by making changes in the project.
• Environmental Impact Statement (E3S), which is a formal and detailed analysis of
alternatives including the proposed action, is undertaken according to CEQ requirements
and EPA procedures.
• Finding of No Significant Impact (FNSI), which announces EPA's finding that the action
analyzed in an EA (either as proposed or with alterations or mitigating measures) will not
result in significant impacts. The FNSI is made available for public review, and is typically
attached to the EA and included in the administrative record for the proposed action.
• Record of Decision (ROD), which is a statement published in the Federal Register that
describes the course of action to be taken by an Agency following the completion of an
EIS. The ROD typically includes a description of those mitigating measures that will be
taken to make the selected alternative environmentally acceptable.
• Monitoring, which refers to EPA's responsibility to ensure that decisions on any action
where a final EIS is prepared are properly implemented.
Subpart B of EPA's Procedures provides a detailed discussion of the contents of EISs. This subpart
of the text specifies format and the contents of an executive summary, the body of the EIS, material
incorporated by reference and a list of preparers.
Subpart C of the Procedures describes requirements related to coordination and other environmental
review and consultation requirements. NEPA compliance involves addressing a number of particular
issues, including (1) landmarks, historical, and archaeological sites; (2) wetlands, floodplains,
important farmlands, coastal zones, wild and scenic rivers, fish and wildlife, and endangered species;
and (3) air quality. Formal consultation with other agencies may be required, particularly in the case
of potential impacts on threatened and endangered species and potential impacts on historic or
archaeological resources. . •
Subpart D of the Procedures presents requirements related to public and other Federal agency
involvement. NEPA includes a strong emphasis on public involvement in the review process.
Requirements are very specific with regard to public notification, convening of public meetings and
hearings, and filing of key documents prepared as part of the review process.
Subpart F presents environmental review procedures for the New Source NPDES Program. This
Subpart specifies that the requirements summarized above (Subparts A through D) apply when two
basic conditions are met: (1) the proposed permittee is determined to be a new source under NPDES
permit regulations; and (2) the permit would be issued within a State where EPA is the permitting
authority (i.e., that State does not have an approved NPDES program in accordance with section
402(b) of the CWA). This Subpart also states that the processing and review of an applicant's
2-3 September 1994
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ifepA Requirements and Provisions
EIA Guidelines for Mining
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NPDES permit application must proceed concurrently with environmental review under NEPA.
Procedure? for the environmental review process are outlined. Subpart F also provides criteria for
determining when EISsmust be prepared, as well as rules relattof to the preparation of RODs and
monitoring of compliance with provisions incorporated within the NPDES permit. (A more detailed
discussion of the enYhgimejiM review process and triggers for certain specific environmental
assessment requirements are presented later in this chapter.)
The remaining Subparts of the EPA Procedures (i.e., Subparts E, G, H, I, and J) address aspects of
E?A'Jnmei*ewP^that.??6., n°t rekyapt to these guidelines for the proposed
iff
'i mmm i »
*
NEW SOURCE NPDES PERMITS
^ ....... ...... bl ...... Exhibit ..... 2:ls ....... the ...... 1^ review ...... of proposed new source permitting actions and the
process of NPDES permit issuance are to occur concurrently. However, completion of the
environmental review-either through the issuance of a FNSI or the issuance of a ROD-is to precede
actual permit issuance or denial.
JE SS™, a ^22&6.fSi^S» EPA IS5I SSS ensure that the two primary conditions
^jj:]ii •. $# ^Sg61" NEPA environmental review have been met. EPA Regional office staff then would
,™ i™..iS$pi!S ll£ il P«15! Applicant to determine,,the scope of the information document; and upon
'.1™" *£S£X fejE SS^aPP11031*, to set time limits on the completion of the review process consistent
^5 55 *SOi-8- (Jnfonnation required from permit applicants is addressed in more detail later
" in this chapter.)
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i£u™:,9Bffi lilt...!*111111 applicant has submted Ae EID, EPA Regional office staff must review the
the 'IP1*??11? ^onS with iPy other available information that is relevant.
a written EA which identifies alternatives, including the
a ^^B??? ^ysis of the potential impacts of these alternatives, and
any mitigation measures that could be (of will be) undertaken to address potential significant
impacts.
' „,' i
1 ' " "r" ;" •" ' " -""I ' : : :
The EA will result in one of two possible outcomes. If the review indicates that the proposed
,,, issuance .ofJhe ,,newsource permit is likely to result in "significant" adverse impacts that cannot be
avoided through changes in the proposal, then EPA must initiate the more formal process of EIS
PIffSratio1!: ShouldtheMrcBgw indicate that the proposed action would be unlikely to result in
significant adverse impacts or that those impacts could be avoided by modifying the proposal, EPA
would issue a FNSI.
I ; : ,^|
September 1994
-,
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EIA Guidelines for Mining
NEPA Requirements and Provisions
Exhibit 2-1. NEPA Environmental Review Process for Proposed Issuance of New Source
NPDES Permits
'&&*
PriawCoadl*n*Oi*tTngg*NEPAEmrin>aa*itMltton*r I
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• SoepJn0M*t*tmin«tion of infomuiion ra
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NEJPA Reqmnanenls and Provisions EIA Guidelines for Mining
A FNSI, which identifies any mitigation measures necessary to make a project environmentally
^^fe* »wstfe^available for public review (typically through publication in the Federal
Register) and comment before issuing the permit.
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The process of preparing an EIS is a more complex and formal process that begins with EPA's
consultation with any other Federal agencies that may be involved in the project. Should EPA be
designated as "lead" agency forjheEE5, EPA would then begin the process through the publication
through EPA's Office of Environmental Review of an NOI in the Federal Register. EPA also may
consult with the permit applicant at this point to discuss the option of preparing the EIS through a
"third-party method." If the applicant and EPA agree on this method (and this agreement must be
expressed in writing), the applicant would then engage and pay for the services of a third-party
EE^ !?: ^ ™ *&***?!*, will elminate the need for further independent
l bl *y?PJfcH*: ^A, i? consultation with the applicant, would choose the
SSI PEZls &E2E2*!: ^closure statements attesting to a lack of financial or
SS2.2 SS SHgSSS.SllS S§8 SB& ¥fluld manage the contractor and would
of the process, a preliminary set of alternatives would be identified, based on
T"1:'-.1: "....-several perspectives: " '
by the applicant .-
Altemaliyes available to EPA
Alternatives available to other agencies with jurisdiction over the facility.
f16*1 f ** sc°Pmg P10^' wni* Solves identifying key issues, refining the list and description of
f111!111?!!!5: ?2 EEE! g=55£5 ISC HE daassi analyses that win be required to complete
the assessment. Public involvement and interagency coordination are important parts of the scoping
, 5!^: !*S 5liE!SZ EE°ly«S US convening of a scoping meeting attended by interested parties
If a third^arty contractor is to prepare the EK, the contractor is not to begin work until after the
scoping meeting is held.
the scoping process, the potential impacts of alternatives, including the proposed action,
are analyzed and a Draft EIS (DEIS) is prepared in accordance wifh strict format and content
TOJUiremen£S- *> fc*«w^ff MSpreparation,a numberof specific coordination and consultation
requirements must be met. These incjude formal consultation with the U.S. Fish and Wildlife Service
(and/or the National Marine Fisheries Service) regarding threatened and endangered species issues as
Wdi as formal consultation with the State Historic Preservation .Offices (SHPO) on any relevant
cultural and historic resource issues.
September 1994
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EIA Guidelines for Mining NEPA Requirements and Provisions
After the DEIS is. reviewed internally by EPA, the public and interested parties are notified of its
availability through a. Federal Register notice, notices hi local newspapers, and letters to participants
hi the scoping process. EPA also would conduct one or more public hearings to further solicit
comments on the DEIS.
Following the comment period for the DEIS, EPA (or the third-party preparers as directed by EPA)
would respond to all comments and would prepare the final EIS (FEIS). After internal EPA review
of the FEIS, notification again is made through the Federal Register, notices, and letters to interested
parties. A final review period allows for any additional comments by the public and interested
government agencies.
The last step in the EIS process is the preparation of the ROD; which summarizes the permitting
action that will be taken, as well as any mitigation measures that will be implemented to make the
selected alternative environmentally acceptable. (A discussion of the relationship between the NEPA
review and the permitting procedures is presented later in this chapter.)
2.2 TRIGGERS FOR NEPA REVIEW ACTIVITIES
2.2.1 PRIMARY CONDITIONS THAT TRIGGER NEPA REVIEW
As noted earlier in this chapter, the following two major conditions must be met before NEPA review
requirements apply.
2.2.1.1 New Source Determination
A proposed NPDES permittee must be determined to be a "new source" before NEPA review
requirement apply. The determination is made by the EPA Region in accordance with NPDES permit
regulations under 40.CFR 122.21(1) and 122.29(a) and (b).
2.2.1.2 EPA is the Permitting Authority
The second major condition that must be met before NEPA review requirements apply is that EPA is
the permitting authority. Under NPDES, States and Native American tribes with an approved
program may administer the permitting program. In such cases, the proposed issuance of a new
source permit would not be a Federal action (unless EPA issues a permit in an approved-program
State pursuant to 40 CFR 123.44(h)). Thus, NEPA requirements would not apply. As of mid-1994,
the NPDES permit program is administered in 40 States. In addition to tribal lands, States and other
jurisdictions where EPA is the permitting authority and where NEPA review requirements would
apply are listed below:
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, NEPA Requirements and Provisions
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* Arizona • •
,'• District of Columbia . •
• • Florida •
• Idaho " •
. '• •»'
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. Maine -
Massachusetts
New Hampshire
New Mexico
i ,
EIA Guidelines for Mining
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• Oklahoma
•: :' ' i'" ; •' -J ^Bk
• Texas ' ^V
• American Samoa
, ' / " 1 ' • •
• Guam
• Puerto Rico
1!
1'
2.2.2 WHEN is AN EIS REQUIRED?
: ; ; ; ' ' . , | :
NEPA requires' that an EIS be prepared for "major" Federal actions "significantly affecting the
<:::= :' •l=: human environment." Generally, the determination of the need for an EIS' hinges on a finding that
'T ' ' the proposed action would result in rignifiggnt adverse i
iiiJ'IiB i> "iKi1,• >>l:<
The new source will induce or accelerate signifigant changes in industrial, commercial,
agricultural, or residential land use concentrations or distributions, which have the potential
for significant effects. Factors that should influence this determination include the nature
and extent of vacant land subject to increased development pressure as a result of the new
source, increases in population that may be induced, the nature of land use controls in the
....... and ...... >£Emges'm ..... tie ...... iBvaOabfl^ or 'demand for ewrgy.'. [[[ '
* The new source will directly, or through induced development, have significant adverse
effects on local air quality, noise levels, floodplains, surface water or groundwater quality
nil ................................. I ....... or quantity, ...... or fish and wildUfe and their habitats.
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EIA. Guidelines for Mining NEPA Requirements and Provisions
• Any part of the new source will have significant adverse efforts on parklands, wetlands,
wild and scenic rivers, reservoirs or other important water bodies, navigation projects, or
agricultural lands.
The determination of significance can be challenging. CEQ provides some guidance in the form of a
two-step conceptual framework which involves considering the context for a proposed action and its
intensity (40 CFR 1508.27). Context can be considered at several levels, including the region,
affected interests, and the locality. Intensity "refers to the severity of the impact." CEQ lists a
number, of factors to be considered when judging severity, including:
• Effects on public health and safety
• Unique characteristics of the geographic area
• The degree to which effects are likely to be controversial
• The degree to which effects are uncertain or involve unique or uncertain risks
• Cumulative effect of the action ' •
• Whether the action would threaten a violation of Federal, State, or local law or regulation.
In bis review of legal issues associated with NEPA, Mandelker (1992) summarizes judicial criteria for
significance. He cites the results of Hanfy v. Kleindienst (II), where the court stated four criteria that
could be used to make a significance determination:
"First, did the agency take a 'hard look' at the problem, as opposed to bald conclusions,
unaided by preliminary investigation? Second, did the Agency identify the relevant areas
of environmental concern? Third, as to problems studied and identified, does the agency
make a convincing case that the impact is insignificant? ... If there is an impact of true
'significance/ has the agency convincingly established that changes hi the project have
sufficiently FPTi'TTVT'y* it?"
The nature of the mining industry can make it particularly difficult to assess significance. Potential
impacts are often uncertain, they often are delayed in time from the permitting action, they can be
quite controversial. Several of the more commonly raised issues surrounding whether the impacts of
a given mining operation could be considered significant are described below.
2.2.2.1 Tmpaets to Already-degraded Environments and Cumulative Impacts
Mining operations -are often proposed in areas where previous mining has occurred, sometimes
directly on sites that have been mined in the past. Many of these areas have been severely impacted
by past mining activity, and the impacts of a modern mine would occur within the context of pre-
existing conditions (it should be'noted that "remining" previously degraded sites can lead to net
improvements in the long-term environmental conditions of a site). In these cases, there are three
fundamental approaches for using baseline conditions to evaluate the significance of impacts:
2-9 September 1994
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I
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NEPA Requirements and Provisions EIA Guidelines for Mining
i :
• Define natural b&kground conditions as the baseline in assessing significance: this
: approach emphasizes that'additional impacts to already-affected envh-onments are even more
serious than to more resilient undisturbed environments.
* ' ' i i
* Define existing conditions as the baseline in assessing significance, but adjust the definition
of significance according to the current quality of the resource that would be affected (i.e.;
envinfflmentaLefisgg thai would be considered "significant," and thus would trigger an
EIS, in an undisturbed natural environment may not be considered "significant" in one
where the resource affected is already degraded, and the degree of degradation also
influence? the determination).
f " I" I ! ||" ," „! II I',"!, ' , I !!,"'""!'! ,' II'T'IIIII I '",!!"" , I
Define existing conditions as baseline but use a consistent definition of "significant.1
C^Q regulations require descriptions of the affected environment in EI?s (40 CFR 1502. 15) but do
not address the issue of how or what pre-existing conditions should be taken into account in assessing
significance. The courts have : addressed the issue and come to various conclusions. In practice,
wasting conditions have assumed a central place both in assessing significance and in considering
mitigation measures in EAs and EISs. Environmental effects that would be considered significant in
• one environment may not be considered significant in another. This has allowed impacts to
Partially "valuable^ ...... *£ri*S£5S£U^3£S&B&. ...... a ..... significance ...... differently than similar of more
serious impacts ....... in ...... degraded ..... .environments., .......... TMs ....... jg ...... by no means absolute, however, since the
assessment of significance is generally mtfc on a case-by-case basis.
It should be note? that the Glean Water Act provides less flexibility: discharges to waters of the
United States that do not meet then- State-designated beneficial uses and water quality standards are
not allowed to further degrade these waters, ibis. has proven to be a problem in some areas where
Ill IIIIIII III II III 111 III
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4 ill Sffii-iSS, E£SSbl *5,SS5; , A proposed operation in such areas could
"threaten a violatign p||gderal. State, or local law or requirements imposed for the protection of the
Cmdr0nmenr(t£ EH ME:E*X!°1 ***,*** HSM tei'iSSrfor fflsldjaation |n deterrnining
*t SSSS ££l!S SS2SI 2222: IMS is P9»nts out the need for sufficient technical
documentation of the basis for determination of how a project will ensure compliance with applicable
water quality standards. -
i n
In addition, CEQ regulations include "cumulative" impacts among the environmental impacts that
must be assessed under NEPA, CEQ defines (40 CFR 1508.7) cumulative impacts as "the
51SfJk?.?^00. Ffeen added to, other past, present, and reasonably foreseeable
future actions...^ This is important _fpr proposed, mining operations for two reasons, First, new
mines are often located in areas-or directly on sites-where mining took place in the past, and where
there are residual impacts from that mining. As noted above, this can complicate the process of
,*??%£% frS±S ..... ....... ....... JS ...... gSSffiSfe,expensive. Second, metal mining operations
m particular almost ..... invariably ...... evolve ..... and expand during ^their active lives, ................ The,,,nature,,,,and,,,extent of
-------
EIA Guidelines for Mining NEPA Requirements and Provisions
future operations depends on the experience gained with the initial operation and on information that
is not .obtained until operations begin.
For example, the sizes of and gold concentrations in ore bodies are never fully understood until the
ore body is mined, so the ultimate success in recovering the gold, and the ultimate extent of mining,
are simply not known at the time initial environmental evaluations must be conducted. Typically,
facility design and operations evolve as more and better, information is gained during mining
operations, and the evolution is captured in proposals for major expansions. Such proposed major
expansions usually trigger new evaluations of potential and actual environmental impacts. These
evaluations are limited by similar information gaps at the time the evaluations are made. However,
there is always much more detailed site-specific information (both environmental and operational) at
the time of a planned expansion, since these types of information are gained during operations. This
information could be used to assess the adequacy of the initial environmental evaluation, and thus to
guide the evaluation for the expansion, but this is not always the case. Indeed, it is not uncommon
for secondary environmental evaluations to be confined to incremental effects of the expansion, not to
the total impacts of the evolving operation. Thus, assessments of potential environmental impacts of
expanding operations may sometimes be less comprehensive even than initial evaluations. In
assessing impacts under NEPA, however, CEQ regulations make it clear that an environmental
assessment or EIS consider the sum total of impacts (i.e., the cumulative impacts).
2.2.2.2 Uncertain Tmpartc
As noted above, CEQ regulations (40 CFR 1508.27) indicate that assessing significance requires
considerations of "context" and "intensity." Intensity, in turn; "refers to the severity of impacts,"
and the regulations list a number of factors that should be considered hi evaluating intensity. These
include consideration of "the degree to which the possible impacts . . . are highly uncertain or
involve unique or. unknown risks" (§1508.27(b)(6)). Uncertainty regarding both immediate and
ultimate impacts is a characteristic of most mining operations, particularly metal mining.
In some cases, there may be a relatively low (but to some extent quantifiable) probability that a
mining operation will cause a significant environmental effect, but the effect, were it to occur, could
be severe. Whether such risks "require an impact statement has'received surprisingly little attention"
by the courts (Mandelker, 1992). Mandelker cited one case that addressed the issue, hi which it was
found that effects which were "only a possibility" could indeed be considered in an impact statement,
and that the agency would have "some latitude" hi making a determination that an EIS was or was not
necessary ((Conservation Law Foundation v. Air Force, 26 Env. Rep. Cas. 2146 (D. Mass. 1987)).
This can be an important issue hi the case of mining. Acid generation potential, and the development
of acid drainage, for example, can be extremely difficult to predict. There are some mines where
acid generation can be predicted with some, confidence, and others where there is only a remote or no
2-11 September 1994
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NEPA Requirements and Provisions ^^ Guidelines for Mining
chance of acMjeneration. For many perhaps most) mines, however, i,tfaere_|s, substantial uncertainty
as jto ii'i5tin^,,Qcsurrence,i as described in Chapter 4. Often, acid generation is considered unlikely
fail possible, or likely but not .certain, based on information available at the time. Other active and
abandoned mines in a particular area may give some idea of the possibility or probability that acid
generation will occur, and any such information should always be assessed. Uncertainty regarding
future acid generation is very common at the time of mine permitting (or approval). As the geology
^ geocjiemjstry Q| jjjg ore b_dy ajyj of waste materials are better understood .during the life of the
nime, more accurate predictions can be made; periodic testing and prediction are sometimes required
throughout the life of a mine by States, or Federal regulators. There are some cases, however, where
substantial uncertainty exists even at mine closure/reclamation.
When acid drainage' develops, it can have catastrophic effects on water quality and aquatic resources
in particular environments. It is nearly always possible to assess the potential impacts on water
t _..„!!!,..,_ quality should acid drainage occur, using various reasonable (and/or worst case) assumptions as to
flow rates and frequency, pH, metals concentrations, etc. This information could be used together '
with information on existing surface water or groundwater quality and on aquatic resources, to assess
the significance of acid drainage should it develop. The assessment of acid generation potential (in
terms of its probability) cou_& then provide guidance as to whether an EIS should be prepared for new
source permit issuance (or for other agencies' actions that authorize development of a mine).
When potential impacts could have catastrophic consequences, even if the probability of occurrence is
casds. These regulations apply to situations where an'EIS is being prepared. In general, the
regulations require that incomplete or unavailable information be obtained and included in the EIS
unless toe cost would be "exorbitant." When costs would be "exorbitant," the EIS must include a
statement that the information is incomplete or unavailable, a statement describing the relevance of the
information to the evaluation, a summary of relevant credible evidence, and the agency's evaluation
of potential impacts based on "ti^retical approaches of research methods generally accepted hi the
^aenjific community." Any such analyses must be "supported by credible scientific evidence," must
not be "based on pure conjecture," and must be "within the rule of reason."
2-2.23 Delayed Impacts
. JSP*?*' as" defined by CEQ regulations (§1508.8(b)), include those "caused by the action and
later in time or farther removed in distance, but still reasonably foreseeable.'' Such -impacts must be
..... HLffi ..... ££», snd significant delayed impacts can trigger an EIS. An example of a delayed
the context of mining wouy jjg acid drataage whose onset occurs years or decades after the
mine opens (or closes). However, there must be a causal relationship between the Federal action (hi
this case, permit issuance or other approval) and the indirect effect: the action must be "proximately
2-12 September 1994
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ELA Guidelines for Mining . NEPA Requirements and Provisions
related to a change in the physical environment" (Metropolitan Edison v. People Against Nuclear
Energy, 460 U.S. 7866 (1983)). This would be the case in the case of a new source permit (or other
approval), since the changes in the earth's surface in excavating a pit or an underground mine, or the
placement of materials in a location and in a configuration that can lead to acid drainage, would be
the direct result of issuing the permit (or approving the plan) and thus allowing me operation to go
forward. For at least some mines, however, it is not clear if acid generation is "reasonably
foreseeable," since mere can be substantial uncertainty as to its ultimate development. Any prediction
of acid drainage would seem to have to be quantifiable (or otherwise supportable) to some extent,
since at least one court has determined that "unquantified speculation" (American Public Transit
Association v. Goldschmidt 485 F. Supp. 811 (D.D.C. 1980)) that subsequent events would occur is
not sufficient to qualify an action as significant.
2.2.2.4 Duration of Impacts .
In general, temporary impacts are not considered significant, but generally the operations of all but
the most ephemeral placer or coal mines would not be considered temporary. Specific activities
associated with mine development, operation, and closure/reclamation are indeed temporary (e.g.,
construction activities associated with mine development), but would have to be considered in terms
of the cumulative impacts of all the effects that result from the Federal action.
2.2.2.5 Transfer of Responsibility for Facility
i
The possession of (or responsibility for) a mining facility can change hands several times over the
active life of the faculty. In some cases, EPA (or another agency) may have reason to believe that
the new responsible party (i.e., the new permittee) will be less able or less willing to carry through
on commitments made by the previous parry. For example, the site, and the responsibility for
implementing mitigation measures, can become the responsibility of an owner or operator with less
experience in dealing with issues faced by the mine, smaller in size and/or financial resources, with a
worse history of environmental performance, and/or with differences in other regards that give rise to
the concern. The transfer itself would not be a "major Federal action" (certainly, it would not
involve issuance of a new source permit unless site conditions/operations changed). It is not clear if a
transfer accompanied by material changes in stipulated mitigation measures (e.g., a change in the type
or amount of bonding required by a State or Federal agency) would allow for any intervention by
EPA, even though this could have major environmental implications.
2.2.2.6 Controversial Actions and Impacts
CEQ regulations (40 CFR Part 1508.27(b)(4)) provide that agencies are to consider whether
environmental effects are "likely to be highly controversial" in assessing their significance, and thus
determining whether an EIS must be prepared. Mandelker cites the leading case that addresses this
issue, Hanfy v. Kleindienst (H) (471 F.2d 823 (2d Cir. 1972)): "the term 'controversial' apparently
2-13 September 1994
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NEPA Requirements and Provisions _ _ . _ EIA Guidelines for Mining
i
refers to cases where a substantial dispute exists as to the size, nature or effect of the major federal
action," not to "neighborhood opposition." Many or most proposed mining operations are subject to
[ *?. ,!!?• ' H°w?vels,, for many
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nature' ...... of ...... (£&&" of tte-poteffijal imoacts; or aU^ three. This uncertainty can be particularly i acute as to
die ultimate extent of the operation (this occurs at many metal mines, since the full extent of the ore
body is seldom known at the time the mine begins operation) and to the potential impacts of a given
operation (given the uncertain extent of the operation in the case of metal mines and the difficulty in
predicting the course of reclamation and ultimate performance of mitigation in the case of both metal
and coal mines). . , _..-..
2.2.3 THE RELATIONSHIP BETWEEN NEPA REVIEW AND NPDES PERMITTING ACTIVITIES
How the NEPA review, process affects NPDES permitting activities is a complex issue. EPA
i regulations clearly establish procedural and timing relationships between the two processes.'
However, how the findings of a NEPA review can affect me substantive omrame of me
process" 1 less 555! fapa^culai; j^ere g a'gn^'area as to how Ep^llllpjoujj| JJStosTNEPA ' "
review findings that are not related to water quality. As summarized by Mandelker (1992), in a
' recent court base it was held that NEPA does not confer on EPA the authority to impose conditions in
effluent discharge permits that are not related to water quality or to'other areas within the purview of
the Clean Water Act.1 However, die court held that NEPA authorized EPA to impose NEPA-
inspired water-related conditions on permits for effluent discharges and to rely on jggp^ to ^eny a
discharge permit. Thus, for example, if a NEPA review indicated that construction associated with a
proposed new source discharge would adversely affect a significant historic resource, EPA would not
be authorized to include in the NPDES permit any conditions that related to that construction.
However, EPA would be authorized to deny issuance of die permit'based on a finding that was not
strictly related to water quality. .
* It should be noted tiiat most States in which mining occurs have assumed responsibility for
iiiiiii i (iiiiiii IP in adrnmistering die NPDES program. Consequently, EPA now issues very few NPDES permits to
mining operations (new sources-or otherwise) and thus is not responsible for NEPA compliance: for
such permit issuance very often (neither State issuance of new source NPDES permits, nor EPA's
concurrence in such issuance, triggers NEPA). However, other Federal agencies are frequently
responsible for preparing EAs or EISs on new mines. Mining often occurs on Federal lands hi die
west, tims requiring NEPA compliance by die Bureau of Land Management, Forest Service, or other
2 "i ! "land management agency. Also, new mines often require issuance of a Clean Water Act §404 permit,
thus requiring NEPA compliance by die Army Corps of Engineers. When an EIS is prepared in such
cases, EPA often participates as a cooperating agency in the NEPA process pursuant to 40 CFR Part
'Natural Resources Defense Council, Inc. v. Environmental Protection Agency, 859 F.2d 156 (D.C. Cir. 1988)
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2-14 September 1994
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EIA Guidelines for Mining " NEPA Requirements and ProTisions
1501.7. Even where EPA does issue a new source permit, another Federal agency may be the lead
agency in preparing the EIS, again with EPA participating as a cooperating agency.
23 LEVELS OF REVIEW
Environmental analysis under NEPA is a process that is attended by extensive internal, interagency,
and public review. In particular, NEPA involves a>strong mandate to involve the public hi the
environmental analysis process. As discussed below, document review is an element of all major
aspects of the analysis process. The formality and intensity of review increases with each escalation
in the hierarchy of NEPA documentation. So, EIDs are subject to the least formal and extensive
review; while EISs are subject to the greatest level of review.
2.3.1 ENVIRONMENTAL INFORMATION DOCUMENT (EID)
The EID, which is prepared by the permit applicant, is reviewed by the EPA Region: Although no
formal public notice is involved at this stage, documents prepared as part of the NEPA review process
are intended to be readily available for public review. The applicant may request confidential
treatment of certain types of business information that is provided as part of the EID.
23.2 ENVIRONMENTAL ASSESSMENT DOCUMENTS (EA)
The EA, which is prepared by EPA Regional office staff (or by contractors or the permit applicant
under EPA's auspices), is reviewed and approved by the EPA Regional Administrator or designee.
The Regional Administrator is formally the "responsible official" for EPA's action.
The Regional Administrator is required to give notice and make EAs and FNSIs available for public
inspection. EAs and FNSIs are reviewed by staff responsible for making permitting decisions prior to
those decisions. Copies of EAs and FNSIs are included in the official administrative record for those
permitting actions.
2.3.3 ENVIRONMENTAL IMPACT STATEMENTS (EISs)
Notices, determinations and other reports and documentation related to an EIS are reviewed internally
by EPA to the level of the Regional Administrator, who serves as the "responsible official," or the
Regional Administrator's designee. Through consultation processes with cooperating and other
interested agencies, EPA provides opportunities for joint decision making and review. These
consultation activities take place throughout the EIS preparation process, beginning with initial
discussions regarding the determination of the appropriate Federal lead agencies through review and
comment on the (EIS) ROD.
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NEPA Requirements and Provisions _ ' _ EIA Guidelines for Mining
i
The public, too. is provided many opportunities for review and participation in the assessment
process. These opportunities include the following:
^ II i I , PI 9
• Publication of the NOI in the Federal Register provides an opportunity for parties to express
their interest in an EIS action.
* A scoping meeting is held early in the process to solicit public and government agency
advice on the issues mat should be addressed and any relevant information that should be
considered in the assessment process.
* Draft EEJS are made available for review by the public and interested government agencies.
Cooperating and interested parties are provided review copies of Draft EISs. Other copies
are provided in easily accessible areas, such as public libraries in the local area of the
proposed action. EPA must respond formally to all comments made on the Draft EIS.
Comments and responses are represented in a special section of the final EIS.
* Similar notice is provided of the availability of Final EISs and RODs and copies are sent to
[[[ interested;parties for their review.
* The Office of Federal Activities (OFA) also maintains copies of EISs for public review and
also provides a copy to CEQ for its review and consideration.
«
Draft fi1131 EISs and RODs are subject to internal review at the regional level, prior to release.
Coordination of the internal review is by the lead branch among the regional program branches:
Depending upon the nature of the specific issue, EPA's Office of General Counsel (OGC), OFA, the
Office of the Administrator, or other EPA offices may also be included in the internal review cycle.
i 1 1 i i * .................
Hi nil 11111 HI ill
As is noted elsewhere, EPA's authorization of most States to administer the NPDES system has
resulted in only occasional issuance by EPA of new source NPDES permits for mining operations.
Even then» EPA Regions more often act as a cooperating or oversight agency on EISs prepared by
o^1" federal agencies (e.g., Federal land managers or the Army Corps of Engineers). In these case,
EPA revi^ pteliminai3r;dia?s,,,, aiKi ,othe£ ElS-related^ *»™??: The junsfflctional and,, other
reaspilsyfdr determining lead vs. cooperating agency roles are discussed in CEQ regulations at 40
CF^ J3* ISO1; Vfte^O*?. Circ^mstan5es' me EPA Region typically drafts a memorandum of
agreement (MOA) with the lead rapd agency, defining respective roles. EPA participates to
va*3[ingIevds m me preparation of the EIS document (with the objective of adopting the EIS), and
I|ii^ issues,^ EPA ROD. As would be the case if EPA were the lead agency, the EIS is part of the
administrative, record for the NPDES permit and should be complete with regard to documenting the
basis for the decision to issue the permit.
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EIA Guidelines for Mining _ NEPA Requirements and Provisions
2.4 INFORMATION REQUIRED FROM PERMIT APPLICANTS
In :^c6rdance with EPA NEPA procedures, the nature and extent of information required from
applicants as part of the EID are bounded by two separate requirements:
• EIDs must be of sufficient scope to enable EPA to prepare its environmental assessment.
• In determining the scope of the EID, EPA must consider the size of the new source and the
extent to which the Applicant is capable of providing the required information. EPA must
not require the Applicant to gather data or perform analyses which unnecessarily duplicate
either existing data or the results of existing analyses available to EPA. EPA must keep
requests for data to the minimum consistent with the Agency's responsibilities under NEPA.
The EPA procedures call for EPA to consult with the applicant to determine the scope of the EID at
the outset of the process. As discussed hi more detail in Chapter 5 of these guidelines, elements of
the EID will be consistent with general requirements for the contents of NEPA documents.
Among the types of information required for EIDs is a balanced description of each alternative
considered by the applicant. These discussions should include the size and location of facilities, land
requirements, operation and maintenance facilities, waste management units, auxiliary structures such
as pipelines or transmission lines, and construction schedules. ,
2.5 TIME INVOLVED IN PREPARING AND PROCESSING NEPA DOCUMENTS
The time required to complete NEPA documentation requirements will vary considerably depending
upon the complexity of issues, public controversy, and other factors. As shown on Exhibit 2-2,
completion of the EA process generally requires at least 5 to 6 months; while completion of the EIS
process ideally requires between 12 to 20 months but usually takes somewhat longer. As noted on
this exhibit, some elements of the schedule (e.g., public review periods) are established by regulation,
while others are more flexible.
Under EPA's NEPA procedures, the Applicant may request that EPA establish time limits for the
environmental review process consistent with 40 CFR 1501.8.
2.6 LIMITATIONS ON PERMIT APPLICANT ACTIONS DURING THE REVIEW
PROCESS
EPA NEPA procedures state that actions undertaken by the applicant or EPA shall be "performed
consistent with the requirements" of 40 CFR 122.29(c) (see amendment in 51 FR 32609, September
12, 1986). In his treatise on NEPA law. and litigation, Mandelker (1992) cites a key case that bears
on this issue. In Natural Resources Defense Council, Inc. v. EPA the court held that, provided no
discharge occurred, EPA could not prohibit construction of a new source.
2-17 . September
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NEPA Requirements and Provisions
EIA Guidelines for Mining
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Exhibit 2-2. Model Schedules for EAs and EISs for Proposed Issuance of New Source
NPDES Permits
Determination of N«w
Sourc*/EPA»
permitting authority
Appfcant prepare* and submits EID (1 month)
EPApreparation of Draft FNSt internal rwriaw;
public notie* (1 month)
'
Action detemftMd to
•ignfficant advene
impacts and action
cannot be modified to
be environmentally
Environmental Assessment (EA)
l Impact Statement (EIS)
Drafting of NOI; inttrnal ravimr; pubfication and
e5st«nm*tkx)toint«r»st«dp«rtiM(1 month)
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'
2-18
..... I
\ September 1994
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EIA. Guidelines for Mining . Overview of Mining and Beneficiation
3. OVERVIEW OF MINING AND BENEFICIATION
This chapter presents an overview of the processes and activities associated with metal ore and coal
mining and beneficiation as currently practiced in the United States. The activities and processes for
mining and beneficiatirig many metal ores are quite similar in many regards, so the first sections (3.1
and 3.2) describe general concepts of ore mining and ore beneficiation which apply to one or more of
the commodity sectors. These general overviews are followed by commodity-specific profiles
(Section 3.3), which discuss in greater detail those aspects of mining and beneficiation that are
particularly important within each of the commodity sectors. These profiles emphasize the process
variations that are unique to mat ore, the chemical reagents typically used in beneficiation of each
ore, and physical/chemical properties that result in the discharge of unique waste streams. Coal
mining and coal processing are then addressed in individual sections (3.4 and 3.5).
3.1 ORE MINING
Mining activities generally consist of exploration, site development, ore extraction (including drilling
and blasting, surface mining, and underground mining), and restoration/reclamation. Processes
typical of these activities are discussed below.
In developing effluent limitation guidelines for discharges from mines, a mine was defined by EPA
(1982) as an area of land upon or under which minerals or metal ores are extracted from natural
deposits hi the earth by any means or methods. The mine includes the total area upon which such
activities occur or where such activities disturb the natural land surface. A mine also includes land
affected by ancillary operations that disturb the natural land surface, and can include any adjacent
land the use of which is incidental to any such activities; all lands affected by the construction of new
roads or the improvement or use of existing roads to gain access to the site of such activities; all
lands associated with haulage and excavations, workings, impoundments, dams, ventilation shafts, •
drainage tunnels, entryways, refuse banks, dumps, stockpiles, overburden piles, spoil banks, tailings,
holes or depressions; and all repair areas, storage areas, and other areas upon which are sited
structures, facilities, or other property or materials resulting from or incident to such activities.
Similarly, hi developing effluent limits for discharges from mills, a mill was defined by EPA (1982)
as a preparation facility within which the mineral or metal ore is beneficiated by being cleaned,
concentrated or otherwise processed prior to shipping to the consumer, refiner, smelter or
manufacturer who will extract or otherwise use the metal contained in the ore. This ore preparation
includes .such operations as crushing, grinding, washing, drying, sintering, briquetting, pelletizing,
nodulizing, leaching, and concentrating by gravity separation, magnetic separation, flotation or other
means. A mill includes all ancillary operations and structures necessary for the cleaning and
concentrating of the mineral or metal ore, such as ore and gangue storage areas and loading facilities.
September 1994
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Pro-view of Mining and Benefication • EIA Guidelines for Mining
: : : , : : ! ;: L; : ; : i
3.1.1 EXPLORATION
In the ore mining industry, exploration is defined as all activities and evaluations performed to locate
and define mineral deposits for the purpose of extraction now or in the future. Exploration activities
range from efforts of a one-man prospector to use of sophisticated ground and airborne sensing
equipment, and extensive sampling and testing programs. A typical exploration program consists of
four principal stages (Bureau of Mines, 1977):
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_
* Regional 'appraisal
•< Dete^ed reconnaissance of favorable.areas
• Detailed surface appraisal of target areas
• Detailed sampling and analysis.
A regional appraisal (Stage 1) typically consists of a review of aerial photographs, geologic maps,
geophysical maps, published reports, and other available literature and may cover an area from 2,600
to more than 260,000 square kilometers (km) (1,000 to 100,000 square miles). The detailed
reconnaissance of favorable areas (Stage 2) typically covers 26 to 260 km (10 to 100 square miles),
and involves more extensive geologic aid geophysical surveys using techniques such as geologic
' mapping; stream, sediment, and rock sampling; and non-destructive ground and airborne magnetic,
electromagnetic, radiometric, and remote-sensing imagery studies (Bureau of Mines, 1977a). Stage 3,
the detailed appraisal of target areas, may involve all of the non-destructive evaluation methods used
in Stage 2, and often includes destructive sampling efforts such as drilling and the excavation of test
pits and trenches. These target area examinations usually cover from 3 to 130 km (1 to SO square
miles), and may identify the existence of mineral deposits that constitute potential ore bodies. If
further definition of the potential ore appears warranted, then a three-dimensional sampling and
preliminary evaluation program (Stage 4) will be conducted. A Stage 4. investigation typically covers
from 1 to 25 km (0.4 to 10 square miles). Its purpose is to identify the study boundary or limits, as
well as the depth, size, shape, mineralization, and grade of the potential ore deposit. Testing
activities may involve extensive drilling; excavation of test pits^ trenches, shafts, and adits;
^™^_^_ ___^_ ^_^ _^__^ __^ ^ maj^ Q~er forms of destructive testing, as well as the
, rwtHje&nictive techniques already described. Tjre extent of these tests will depend greatly upon the
location, accessibility, geologic setting, and types of minerals under investigation. In addition,
support activities such as the construction of access roads and the building of temporary living
quarters may be undertaken!
• " ' . '. , • i
The first two principal stages include very limited destructive testing, if any. The potential for
adverse environmental impact is thus limited to those impacts associated with gaining access to the
areas. The last two stages, however, involve destructive testing activities which may be undertaken
before or after permit applications are filed. Therefore, construction activities and destructive
" : - , . " I •]
exploratory testing that may result in adverse environmental impacts can occur prior to the filing of
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3-2 September 1994
111 lilllll !• IIM^^^ lllillliilllliM Iliillli
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EIA Guidelines for Mining Overview of Mining and Beneficiation
applications for NPDES, PSD, and other Federal, State, and local permits. The exploratory tasks
conducted by the permit applicant, and the known environmental impacts (adverse and beneficial)
resulting from the exploratory activities, should be well documented within the BED.
3.1.2 SITE DEVELOPMENT
Once a mineral deposit of commercial value has been defined by exploration activities, it is necessary
to construct facilities for extracting the ore, beneficiating it if necessary, and transporting it to market.
The site development process has many possible stages depending on the type of mine projected and.
its relation to the surrounding transportation system. Site development activities may include the
following.
3.1.2.1 Construction of Access Roads, Rail Lines, or Ship/Barge Terminals
Road and rail lines will require clearing a right-of-way, filling or excavating to a desired grade, and
paving or laying rail. This may involve the use of earthmoving equipment such as graders, scrapers,
bulldozers, power shovels or backhoes. These operations may result -in the destruction of vegetation
along die right-of-way, and possibly the production of excess earth from excavation or the
requirement that borrow pits be created for obtaining fill material. Overburden or waste rock from
the developing mine may be used in road or other construction. In a few cases, acid-generating waste
rock used for various purposes has caused significant problems. In previously undeveloped terrain,
the removal of vegetation and/or soil cover may cause an increase in the rate of local erosion, and,
where terrain is steep, increase the potential for mass wasting processes such as slumps, landslides,
and mud flows. If excavation extends into hard materials, blasting may be employed. It can be
expected that these operations will produce brush and timber debris which must be removed, buried,
or burned if permitted. There will also be dust generated during earthmoving. Development of ship/
barge loading facilities may require dredging and construction activities that disturb bottom sediment.
3.1.2.2 Construction of Mining Facilities
Initial work at most mines involves obtaining access to the ore bodies. At surface mines, topsoil and
overlying rock must be removed; at underground mines, shafts, or adits must be driven. These
operations involve the operation of earth moving and construction equipment, the erection of
structures, and, possibly, major excavation. Waste rock dumps must be provided and topsoil may be
stockpiled for future use in restoration activities.
Also, ancillary facilities such as maintenance and office buildings may be constructed during this
stage. At many larger mining operations, living facilities for mine personnel may involve the
construction of major housing, shopping, and recreational developments.
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Ill 111 Illllll
Overview of Mining and Benefication EIA Guidelines for Mining
3.1.2.3 Construction of Mfll Facilities -
1 '"' ' '''' ' " ' ! '!'' '' 'n'' '' "' |! 'h !' ' ! I1"1 ' l|1'"" '" ""'4| *'"' "' "' !"'
Unless the ore is of such a high grade that it can be economically shipped for offsite beneficiation, a
mill must be constructed in order to beneficiate the ore to a marketable grade. Usually the mill will
be located as close to the mine as is practicable in order to reduce the costs of transporting the raw
ore. However, in some.cases, conditions dictate construction of a mill at a considerable distance
from the mine and sites at lower elevation are always preferred. Roads, railway lines, and/or
conveyors must be constructed train the 'mine' to^'mOL The ^^ —— —- ——-—^-.~
generally be similar,to those incurred in the construction of any industrial/nianufacruring facility.
Land most be cleared of vegetation and preparey excavation and grading. Materials must be ''
transported to the site and assembledby a sizeable labor force. These operations may result hi the
production of vegetation and construction debris, emission of fugitive dust, generation of noise from
construction machinery, and increased sediment loading to local streams, as -well as secondary effects
caused by the influx of construction laborers.
3.1.2.4 Other Pre-Mining Activities
Other aspects of mine/mill development may include the need for installing utilities (i.e., electrical
„ ^f°222S£S SB, °£ ESS lies) to toe she, or hi remote areas constructing a power plant and/or
^^^ &*PPty system. In very remote regions, it may even be necessary to construct a settlement
G-e-» tiring Spacers jnd support facilities) for the mill construction and operation personnel.
3.1.3
Minerals are extracted from the earth by a wide variety of techniques. In general, inining consists of
removing the ore from the host rock.or matrix and transporting it away from the mined site: In the
interests of economic efficiency, the extraction process is designed to remove ore of a predetermined
"~ZZ! ...... &?$*. ..... °1 ..... ^?E» ...... !e§Y5S behind lower-grade ore and barren rock if this is, practicable. In practice,
™5?':±5^^?. ...... ^5 ...... 3S!— 2 ..... SEt^3^ Possible, so that 'some lower-grade rock is mined and some
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fe an economic one that varies from mine to mine and can vary in time at specific mines.) Most
SS^Si5;i:i^??i!fe^.,ff2S?S2 ...... 5=5!! ....... "~ ..... ^I^lSl,0! ,§??„ ..... and, associated rock or matrix in bulk form from the
"*"* various mechanical means to break the ore into pieces of manageable size or to separate
ore minerals from unwanted material.
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SL!!^!11!!!"68, JElHf?6,, *?„ HSS °I,e?plosives or heavy machhiery to break up or to excavate
ore-bearing rock or matrix; high-pressure streams or jets of water, to disaggregate beds of
:; sluices, riffles and other hydraulic devices to separate placer minerals from the bedload of
streams. Some (copper and uranium) ore deposits are suitable for extraction by in situ solution
techniques, in which the ore minerals are dissolved hi the ore body by solvents and pumped to
processing' areas in solution.
3-4 September 1994
i 11 ill in 111 PI i in in i i i i i ill in n iiiii in iniii1111 mi ni in nlii11 in nun iiiiiiiiiiiiiiiliiiiiiiiiiii ill i n 11 nil
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EIA. Guidelines for Mining '. Overview of Mining and BeneStiation
Although mining processes may be classified according to the numerous techniques that are employed
in removing ore, they can be broken down into two broad categories that are associated with the
general setting of the running operation. These are: (1) surface mining or open-pit processes; and
(2) underground mining processes. Specific techniques and applications within this framework are
discussed below.
3.13.1 Surf ace Mining
Surface mining is the major type of mining operation for most of the major metallic ores in the
United States. This is the method of choice when the ore deposit is near the surface, or is of
sufficient size to justify removing overburden. At present, this is the most economical way of mining
highly disseminated (lower-grade) ores. Generally, ore deposits must be within 150 meters
(approximately 500 feet) of the surface for surface mining methods to be economically feasible.
Surface mining methods typically used for ore extraction are discussed in the following paragraphs.
3.1.3.2 Open Pit Mining
This method involves excavation of an area of ground and removal of the ore exposed in the resulting
pit. Depending on the thickness of the ore body, it may be removed as a single vertical interval or in
successive intervals or benches. If the ore is mined as a single vertical interval, it may be feasible to
place waste rock from one area in the space (pit) left by previous mining of the adjacent area. ..
However, the ore body generally is mined in benches after the overburden has been completely
removed from.the mine area. In resistant materials, the procedure usually employed involves mining
each bench by drilling vertical shot holes from the top of the bench, and then blasting the ore onto the
adjacent lower level. The broken ore and waste rock then is loaded into rail cars or trucks for
transport to the mill or waste rock dumps, as the case may be. In less resistant materials, the ore
may be excavated by scrapers or digging machinery without the use of explosives. A variation of
open pit mining involves use of a central shaft (or glory hole) into which ore from an open pit is
dropped. The ore is allowed to move downward through the vertical or inclined shaft to an
underground level where it is loaded into cars for transport to the surface. This method is especially
favored if the ore body is relatively deep and narrow.
3.133 Dredging
Placer deposits are concentrations of heavy metallic minerals which occur in sedimentary deposits
associated with watercourses or beaches (either current or ancient). These deposits can be mined by
surface open pit methods, but in some cases can be better handled by dredging. For this method, the
mine area is flooded and the excavating/mining equipment mounted on a barge. In hard materials the
dredge uses a mechanical digging system to break up and excavate the deposit, while soft deposits can
be removed by hydraulic suction alone. Mechanical dredges can use individual digging buckets
(clamshells) to excavate the material; or, if conditions permit, will use a chain of buckets which dig
3-5 September 1994
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Orei-view of Mining and Benefidation
: I : ; :
I!
EIA Guidelines for Mining
85 ^ continuoussequence and transport material steadily into the dredge for processing. Suction
dredges essentially operate as "vacuum' cleaners" to mine out the alluvial material, although some
***&* E!°!E1<:?&£ te?dB.5Minbreaking up the material prior to its removal by suction. Placer
deposits can also be worked with small portable suction units and by traditional hand sluicing and
panning; however, these portable suction and panning methods can handle only limited volumes of
material. There are no commercial dredges operating in the United States as of jhe11990s, although
,$f ffffaofogy may be in use elsewhere. Also, suction dredging hi the United States is mainly
practiced by recreational miners or very small commercial miners
* i _ i .
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ii
3.13.4 Underground Mining
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Underground mining has been the major method for production of several metals but is increasingly
less common in die United'States. Underground mining activities typically have significantly less
SSffiSS £* suxgce ffSHSSS liHS, fe-SSJaS ttS&Bta. .IMS, is due both to the fact that less
waste rock is mined with ores that are mined'underground, and the fact that waste material can be
"^ to, backfill mined out spaces. However, large underground openings such as slopes can cause
s^^?^,0£ ^Y?? a*_*®.?1?*!?^»^suiting m significant disturbance to structures, roads, drainages,
etc. Drainage from underground mines also may cause significant alteration to the quality of surface
water and can affect groundwater quantity and quality.
SeVeraI underground mining procedures rely on the natural support of the ground, including:
• Room and Pillar. This method is suitable for level deposils lhat are fairly uniform in
thickness, ft consists of excavating drifts (horizontal passages) in a rectilinear pattern so
that evenly spaced pillars are left to support theoverlying material. A fairly large portion
of the ore (40%-50%) must be left in place. Sometimes the remaining ore is recovered by
removing or shaving the pillars as the mine is vacated, allowing the overhead to collapse or
making future collapse more likely.
i 2 Open.Stope. In competent rock, ft is possible to remove all of a moderate sized ore body
'' I' resulting in an opening of considerable size. Such, large, irregularly-shaped openings are '
called slopes. The'.mining of large inclined ore bodies often requires leaving horizontal
P ^acr^*®=°J^,^ ?° prevent collapse of the walls.
Some other degree of support is required hi most underground nunes. The basic concepts of the
methods described above, gmjgeaended to permit working hi less competent rock to allow
" extraction of a greater percentage of the ore, by using variotis methods of permanent or temporary
support in order to prevent or delay collapse.
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3-6 September 1994
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EIA Guidelines .for Mining ' Overview of Mining and Beneficiation
Underground mining methods that use these temporary or permanent methods of support include the
following:
• Longwall. In level, tabular ore bodies it is possible to recover virtually all of the ore by
using this method (in the United States, only coal is known to have been mined using
longwall methods). Initially,.parallel drifts are driven to the farthest boundary of the mine
area. The ore between each pair of drifts is then mined along a continuous face (the
longwall) connecting the two drifts. Mining proceeds back toward the shaft or entry, and
only enough space for mining activities is held open by moveable steel supports. As the
longwall moves, the supports are moved with it and the mined out area is allowed to
collapse. Various methods can be used to break up and remove the ore. In many cases,
the rock stresses that are caused by the caving of the unsupported area aids in breaking the
material, in the longwall face.
• Shrinkage Stoping. In this method, mining is carried out from the bottom of an inclined
or vertical ore body upwards, as in open sloping. However, most of the broken ore is
allowed to remain in the stope in order both to support the stope walls and to provide a
working platform for the overhead mining operations. Ore is withdrawn from chutes in the
bottom of the stope in.order to maintain the correct amount of open space for working.
When mining is completed in a particular stope, the remaining ore is withdrawn, and the
walls are allowed to collapse. ..-•'.
• Cgt and Fill Stoping. If it is undesirable to leave broken ore in the stope during mining
operations (as in shrinkage sloping), the lower portion of the stope can be filled with waste
rock and/or mill tailings. In this case, ore is removed as soon as it has been broken from
overhead, and the stope filled with waste to within a few feet of the mining surface. This
method eliminates or reduces the waste disposal problem' associated with mining as well as
preventing.collapse of the ground at the surface.
• Square-set Stoping. Ore bodies of irregular shape and/or that occur in weak rock can be
mined by providing almost continuous support as operations progress. A squareset is a
rectangular, three-dimensional frame usually of timber, which is generally filled with waste
rock after emplacement. In this method, a small square section of the ore body is removed,
and the space created is immediately filled by a square-set. The framework provides both
lateral and vertical support, especially after being filled with waste. Use of this method
may result in a major local consumption of timber and/or other materials utilized for
construction of the sets. -
• Top Slicing. Unlike the previously described methods in which mining begins at the
bottom of an ore body and proceeds upward, this procedure involves mining the ore hi a
series of slices from the top downward, first removing the topmost layer of the ore and
supporting the overhead with timber. Once the top layer of an area is completely removed,
the supports are removed and the overlying material allowed to settle onto the new top of
the ore body. The process is then repeated, so that as slices of ore are removed from the
ore body, the overburden repeatedly settles. Subsequent operations produce an ever-
thickening mat of timber and broken supports. This method consumes major quantities of
timber.
1994
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i ill i
'I'Oyeryiew of Mining and Benefidation EIA Guidelines for Mining
i '" i ''
Additional methods of underground mining' involve procedures in which ore is broken by removing its
K*d as the ore mass subsides to break the ore into manageable
- pieces. JMds based on Ais priiuqpa include:
; , • • . • , i,
* Block Cavjng. Large massive ore bodies may be broken up and removed by this method
with a mmfntfim of direct handling of the ore required. Generally, these deposits are of
= sucn f sizethat they would be mined by open-pit methods if the overburden were not so
thick. Application of this method begins with the driving of horizontal crosscuts below the
bottom of the ore body, or below that portion which is to be mined at this stage. From
these passages,' inclined raises are driven upward to the level of the bottom of the mass
which |s to be broken. Then a layer is mined so as to undercut the ore mass and allow it to
setfle ,?nd'breakup. Broken ore descends through me raises and can be dropped into mine
cars for transport to the surface. When waste material appears at the outlet of a raise it
signifies exhaustion of the ore in that interval. If the ore extends to a greater depth, the
entire process can be continued by mining out the mass which contained the previous
i working passage.
llllllllllllllllll I 111 Ill III 11 IN III —70 J-——O
I''
* Sublevel Caving. In this method, relatively small blocks of ore within a vertical or steeply
sloping; vein are undercut within a slope and allowed to settle and break up. The broken
1 ore *l|!fl Hi?*11 into rais68 and dropped into mine cars. This method can be considered
as an intermediate between block carving and top slicing.
NaturaUy mere are many variations and combinations of the basic methods discussed above. For
exanjiple, a stope which is not quite capable of standing open without support may be. maintained by a
i&$ of single timbers (or stalls) placed from wall to wall in a system called stall sloping. Many of
the variations and combinations of underground mining utilized today have been developed hi
response to specific or unusual characteristics of the ore being mined Mining methods used in the
production of specific ores are presented by ore subcategory in subsequent sections of this chapter.
„„; ' i MM .IS ,SS .Solution Mining
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This is a method of underground mining that is applicable to certain ores under certain geohydrologic
conditions. In principal, a series of wells are drilled into the ore body and a solvent is circulated
through the ore-bearing formation by injection through some of the wells and withdrawal through
owners. Use of me method has obvious geochemical restrictions based upon the amenability of the ore
minerals to solution and the cost and practicality of solvents, and based on concerns related to
groundwater quality. Hydrologic requisites include: (1) the host rock must be permeable to
| J J . __ . •' ' • ' ' •"' ' » • • *
£S£J2 225 £2 ii = Ill !??! HfiJ* OYerllln and underlain by impermeable formations or
ro^c "nte ttejeajtoldiie vertical low oj fluids, Jn situ solution mining is at present applied most
widely to uranium and copper deposits in suitable geohydrologic settings.
Although there is little disturbance of the bulk properties of the surface and underground materials at
an in fitu solution mine, the effects of the operation on the quality of underground water can be
enormous. In order to solubilize the ore minerals, the chemistry of the groundwater must be
-3-8 September 1994
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EIA Guidelines for Mining • •- ' • Overview of Mining and Benefidation
drastically altered by 'the introduced solvents. In addition to the ore minerals, other materials are
dissolved by the solvent action and these, too, enter the groundwater, generally rendering it
unacceptable for human or animal consumption and often presenting a hazard of further contamination
if the altered groundwater moves out of the mine area and into surrounding areas. Provisions for
emergency cleanup and post-mining restoration of the groundwater often are required prior to
issuance of permits for this type of operation.
3.1.4 MINING WASTES AND WASTE MANAGEMENT
The wastes generated by mining operations (as opposed to mills) in the largest quantities, and that
present the most significant environmental impacts during and after mining, are mine water and waste
rock. These are described in the following two subsections. .Other wastes are generated in much
smaller quantities, and they generally have much less environmental significance. Many of these
wastes are described in the commodity-specific discussions in Section 3.3. (It should be noted that
the use of the terms "mining waste" and "waste management unit" in this document does not imply
that the materials in questions are "solid wastes" within the meaning of the Resource Conservation
and Recovery Act.)
3,1.4.1 Mine Water
Mine water is water that must be removed from the mine to gain or facilitate access to the ore body.
For surface mines, mine water can originate from precipitation, flows into the pit or underground
workings, and from groundwater aquifers that are intercepted by the mine. Mine water can be a
significant problem at many, mines, and enormous quantities may have to be pumped continuously
from the mine during operations. Dewatering can result hi significant groundwater drawdowns, and
this in turn can result in the loss of streamflows as well as wetland and riparian habitat hi some areas.
Uses of mine water can include:
• Dust control on the mine site (with or without prior treatment, depending on its quality and
regulatory requirements). "
• Process water hi the mill circuit (again, with or without prior treatment).
• Discharge to surface water pursuant to an NPDES permit, which would include effluent
limits on the discharge (limits would be either the 40 CFR Part 440 effluent units on mine
drainage or more stringent limits if those were necessary to protect water quality).
When a mine closes, removal of mine water from the mine generally ends. Underground mines can
then fill (or partially fill) and mine water may be released through adits, or through fractures and
fissures that reach the surface. Surface mines that extend below the water table fill to that level when
pumping ceases, either forming a "lake" hi the pit or inundating and saturating fill material.
Recovery of groundwater to or near pre-rnining levels following the cessation of pumping can take
3.9 September 1994
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and Beneficiation _ EIA Guidelines for Mining
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' '"""•' '"'^^ 522SJ5 ™,5SS £222il? fiSSS?, £2 SSLlES groundwater drawdown (e.g.,
reduction or elimination of surface water recharge) may continue to be felt for decades or centuries
1 in i''' T liiiiiiiiiiinniinn, nil! 11,1, iiiiiiiiiiiiiiiiiiriiiiiiiiiiiininii:
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EIA Guidelines for Mining Overview of Mining and Beneflciation
disposing of waste rock down slope from the crest of a ridge and represent the most common form of
waste rock dumps (BCMDC, 1991). Heaped fills or waste piles are constructed in areas of flat
terrain where available topography and other factors require.
Regardless of the layout of the unit, waste rock dumps are generally constructed on unlined terrain,
with underlying soils stripped, graded, or compacted as regulations and engineering consideration
require. Such conditions may include steep foundations of unconsolidated material or partially
saturated terrain that may not support the weight of fill material. Rock is hauled to the face of the
unit in trucks or by conveyor systems and dumped. Surface grading of fill material is typically
performed to provide haulage trucks access to the working face. Most commonly, waste rock is
deposited at the angle of repose. If multiple lifts are constructed, or if stability of the dump is a
concern, side slopes may.be graded. Additionally, final dump slopes may be graded during
reclamation activities.
Depending on site hydrology and regulatory constraints, drainage systems may be incorporated into
dump foundations. In areas of ground water intrusion or where catchment areas channel substantial
surface water flows into the dump, drainage systems help to prevent instability due to foundation
failures from saturation (BCMDC, 1991). Drainage systems may be constructed of gravel-filled
trenches or'gravel blankets, with capacity and configuration determined according to site-specific
conditions. Dump toe drains may be particularly favored to reduce pore pressure near the face .of the
structure to prevent toe spreading or local slumping.
Equally important are surface water and run-on controls. Such controls are often necessary to
maintain stability .and prevent mobilization of fines as well as erosion of exposed slopes. Upstream
surface water diversion ditches and rock drains are options often incorporated into design for these
purposes.
3.1.5 RESTORATION AND RECLAMATION
Restoration activities often are conducted during surface mining activities in order to reduce
environmental impacts and enhance visual aesthetics in the mining area. Although these restoration
activities do prove valuable, they do not replace or lessen the necessity for full and comprehensive
land reclamation at the completion of various staged mining activities. Temporary restoration
activities may involve tasks such as landscaping in non-mining areas, soil stabilization by replacement
of native grasses on spoil bank slopes, and using temporary vegetation covers on topsoil and other
stockpiles.
Restoration activities conducted during underground mining operations are similar to those used in
conjunction with surface mines, but are more limited since the waste piles developed as a result of
underground mining are relatively smaller. Restoration activities conducted during underground
3-11 September 1994
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SriKsSSfi' l&F i*
....... ....... —
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periodc seaing of drift ennywaysto prevent mine drainage.
^ ...... ~ ....... ?!°sion contro1 measures around the mining site, and the
.....
" '""' ' ............................. ^li!!!16 land reclamation activities begin upon ...... congletion of ..mining or of planned unit mining
" ..... Bli [[[ st^S" ..... These s^ges can be three to five yearplans ...... for ...... large ..... mines! ...... or: ..... one- to three-month events .
[[[ ftF ...... SL22S ...... 2S2| operations. Land reclamation activities are not temporary restoration measures
........... "' ................. ........... ' .................. .......... ......... tafce* to «
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EIA Guidelines for Mining ... . . Overview of Mining and Beneficiation
• Removing waste rock and using it as backfill in underground workings or the open pit.
This can be prohibitively expensive, and is generally not an economic option after the waste
rock has already been placed in dumps. In addition, nonreactive (i.e., not acid forming)
waste rock can be used as construction material during successive stages of mine
development (e.g., roads, tailings dams, water diversion berms, building foundations,
underdrains) and for off-site construction.
• ' Regrading steep slopes of the dump to slopes less than the angle of repose, thus enhancing
long-term stability. Regrading can include incorporating flat benches at intervals of the
slope to reduce runoff velocity and provide another surface suitable for revegetation.
Depending on the size of the waste rock, it may be appropriate to cover slopes with topsoil
and revegetate.
• If the dump contains acid-generating waste rock, reducing infiltration becomes even more
important. This can be accomplished by lining the top surfaces of dumps with synthetic
materials or clay. Then, the cap or liner is covered with a protective layer of fine-grained
material, covered with topsoil, and revegetated; alternatively, the surface can be covered
with large rocks and boulders. When revegetating, particular care must be taken in
selecting the plant species, since they must resist extreme cycles of drought and saturation.
In addition, species must be shallow-rooted to avoid penetrating clay caps.
3.2 ORE DRESSING (BENEFICIATION)
Most ores contain the valuable metals disseminated in a matrix of less valuable rock called gangue.
The purpose of ore beneficiatibn is the separation of valuable minerals .from the gangue to yield a
product which is much higher in content of the valued material. To accomplish this, ore generally
must be crushed and/or ground small enough so that each particle is composed predominantly of the
mineral to be recovered or of gangue. This separation of the particles on the basis of some difference
in physical or chemical properties between the ore mineral and the gangue yields a concentrate high in
values, as well as waste (tailings) containing very little value. Overall recovery is optimized
according to the value (and marketability) of the concentrate produced.
Many properties are used as the basis for separating valuable minerals from gangue, including:
specific gravity, conductivity, magnetic permeability, affinity for certain chemicals, solubility, and the
tendency to form chemical complexes. Processes for effecting separation may be generally considered
as: gravity concentration, magnetic separation, electrostatic separation, flotation, and leaching.
Amalgamation and cyanidation are variants of leaching which bear special mention. Solvent
extraction and ion exchange are widely applied techniques for concentrating metals from leaching
solutions, and for separating them from dissolved contaminants.
3.2.1 GRAVITY CONCENTRATION
Gravity-concentration processes exploit differences in density to separate ore minerals from gangue.
Several techniques (e.g., jigging, tabling, spirals, sink/float separation) are used to achieve the
3-13 September 1.994
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Overview of Mining and Beneficiation EIA Guidelines for Mining
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separation. Each is effective over a somewhat limited range of particle sizes, the upper bound of
; set by the size of the apparatus and .the need to transport ore within it, and the lower bound
by the point at which viscosity forces predominate over gravity and render the separation ineffective.
Selection of a particular gravity-based process for a given ore will be strongly influenced by the size
to which the ore must be crushed or ground to separate values from gangue,. as well as by the density
difference and other factors.
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Gravity concentration typically involves three general steps, the first to remove grossly oversized
material from the smaller fraction that contains the valuable mineral (generally gold), the second to
concentrate the mineral, and the third to separate the fine values from other fine, heavy minerals.
The same typtof^yapn^. is pften.used in more than one step; for example, an array of jigs may be
employed to handle successively finer material (Flatt, 1990).
Classification (sizing) is the initial step in the beneficiafion operation. Large, oversized material
(usually over 3/4 inch) is removed. A rough (large diameter). screen is usually used. This step may
be feji by a bulldozer, front-end loader, backhoe, dragline or conveyor belt. Within the gold placer
industry, this step is also referred to as roughing (EPA, 1988a). Previous studies have indicated that
. the practice improves the efficiency of gold recovery and reduces water consumption (Bainbridge,
1979). 1- • ' ' ' " ' ' _ ..... ; ........ ; ..... _
• •
After ..... SX,iSSi,i:2222!- ...... SmS^JSFB61 n13161*3! during sizing, ore is subject to a coarse concentration
stage; This step, also referred to as cleaning, may employ trommels or screens. Other equipment
used in the coarse concentration stage includes sluices, jigs, shaking tables, spiral concentrators and
cones. Depending on the size of the particles, cleaning may be the final step hi beneficiation (Flatt,
1990; Silva, 1986). [[[ : ....... ..... ............. ' [[[
1 1 ii
Fine concentration is the final operation used to remove very small values from the concentrate
generated in the, previous stages. Many of the previously identified pieces of equipjnent can be
gjljgjj^l g_. ^^ ^qjjJSfon. sensitivity. Final separation uses jigs, shaking tables, centrifugal
concentrators, spiral concentrators or pinched sluices.
The following is a summary of the equipment commonly used in beneficiation. One of the key
detenrunants in selecting equipment is the volume of material that will pass through each step within a
given time period. Rates for ore handling for the equipment discussed below are included where the
information was available.
3.2.1.1 Sizing
' ' i
Sizing is the physical separation of material based strictly on size. The sizing step removes large
rocks prior to additional beneficiation. The waste generated is usually solid and is much lower in
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EIA Guidelines for Mining Overview of Mining and Benefication
volume compared to the ore that passes through. .Discharge material may be used for other
applications including-road aggregates. This step typically involves the ore being loaded into a
grizzly, trommel or screen, or a combination thereof.
A typical grizzly consists of a large screen or row of bars or rails set a specific distance apart (2 to 6
inches) such that undersized (gold-bearing) material can readily pass through while oversized material
is rejected. Typically, the grizzly would be inclined to ease the removal of the rejected material.
Water is usually used to move material through the grizzly and wash off any fines that may be
attached to larger fragments before they are discarded. The undersized material drops onto a
trommel, screen, or sluice depending on the operation. Grizzlies may be stationary or vibrating
(EPA, 1988a).
Trommels are wet-washed, inclined, revolving screens. They usually consist of three chambers, the
first uses a tumbling action and water to break up aggregated material. Successive chambers are
formed of screens or punched metal plates (smaller holes first) that allow the selected sized material
to pass through. The screens are typically 3/8 inch in the second chamber and 3/4.inchIn the final
chamber. Material passing through the screens is directed for further concentration. Material passing
through the trommel may be returned for a second pass or discarded (Cope and Rice, 1992; EPA,
1988a).
A fixed punchplate screen (also called a Ross Box) consists of an inclined plate with holes ranging
from 1/2 to 3/4- inches. Ore is placed onto the plate where nozzles wash the material with a high-
pressure water stream. The undersized (desirable) material is washed to the outside of the plate
where it is fed into a sluice designed to handle 3/4 inch material. The oversized material is directed
down the plate which typically has riffles to collect coarser gold. Oversized material passing off the
plate is discarded.
Screens function to separate oversized, undesirable material from the ore. Screen size (usually 1/2 to
3/4 inch) is selected based on ore characteristics. Screens may be fixed or vibrating. The action of
bom is similar although vibrating screens speed the rate of particle separation. The concentrate
continues for further concentration while the oversized material is removed via a chute or stacker
conveyor belt. Different sized screens may be used to sort material into different sizes for use as
road construction aggregate or other purposes.
3.2.1.2 Coarse Concentration
Separation in the coarse concentration step involves particle density rather than size. Sluices are the
pieces of equipment most commonly used by gold placer mines in the coarse concentration step
although jigs and screens may also be employed. The wastes are discharged to a tailings pond, also
called a recycle pond or settling pond. Most of the material that enters the sluice exits as waste. The
3-15 September 1994
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i liiUiJI liiH^
Overview of Mining and Benefication •.. EIA Guidelines for Mining
gold and other heavy minerals settle within the lining material while the lighter material is washed
through. Coarse concentration generates the largest volume of waste during beneficiation.
A sluice consists of a long, narrow, inclined trough lined with riffles, perforated screens, astroturf,
;;; 1=^^ ":i' corduroy, burlap, or a combination thereof. The sluice mimics the .conditions that .caused the
formation of the placer deposit initially. Ore is placed at the high end of the trough and washed with
aspreamofwater. Gold and other dense minerals settle between me riffles or in the lining while the
lighter material is carried through the sluice. Longer sluices are used for preliminary concentration.
Shorter, wider sluices are used following preliminary separation to separate fine gold from black
sands. The length, grade, riffles and lining are adjusted to suit the nature of the ore. However,
slopes of one to two inches per foot are typical.
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Riffles are bars, slats, screens or material that act to create turbulence and variation of water flow
within the sluice. This action increases the efficiency of gravity separation. Riffles have ranged in
s£zef from 12 inches wide, 12 inches high and 12 inches apart to 1 inch high, 1 inch wide and 2 inches
apart.
™™lkHungarian riffles arc angle irons mounted perpendicular to the sluice box. The vertical angle of the
angle irons may be adjusted to affect the degree of turbulence generated and marinrnrt gold
^j^tieposidon. Astroturf, carpet or coconut husks are sometimes placed between and under the riffles to
mMMFwtfttti7x their efficiency. The units are usually constructed so that sections of the riffles may be
iijJJ^fSPSESl mi £8,folt* can ** recovered from the turf. As mentioned above, the height, spacing and
2S&2* 'construction of the riffles may be adjusted to maximize efficiency of separation depending on the
character of the ore.
has also been tested and/or used as riffles and liners. Expanded metal riffles are
employed at some operations. Like the hungarian riffles, the height, size-and spacing is determined
by the orc and sections are removable for cleaning. Miscellaneous materials including longitudinal or
•!;•== ri?!^0*^..?1!^0"?^]?^!*8* blocks, rocks, railroad ties, cocoa mats, rubber and plastic strips have also
S°SSl lilting used as riffles by different placer operations (EPA, 1988a).
=^^^^ !!!='3.2.O, Une Concentration
'• ' ' ' ' •' "' ' '"' ' ' ' ' ' 1|I'"LIJ1 ' " »•' " ' "" J'" '"' Nl ' ' '"''' "' -
x the ore is concentrated, typically through a trommel and sluice, most waste material has been
, , , , _ * £J5£ SSSSHSS: ISS, SSSSSSSS&Rpy men be subjected to fine concentration
,,....... " ' •• • n
including jigs, shaking tables and pinched sluices. Depending on the nature of the
ie equipment, 80 to 95 percent of gold can be recovered from the concentrate at this
SSl ..... S ..... l49§? ...... I* ...... §.?"ny (often called slimes), and is low in volume compared to that
5 ..... * ottw ..... stages.
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3-16 September 1994
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T3A GviideBnes for Mining . Overview of Mining and Benefidation
Jigs are settling devices that consist of a screen through which water is pulsed up and down via a
diaphragm or plunger numerous times per second.. A layer of rock or steel shot referred to as
ragging may be placed on the screen to accentuate the up and down motion. Slurry is fed above the
screen. The agitation keeps die lighter material in suspension which is then drawn off: The heavier
material falls onto or through the screen and is collected as concentrate. Efficiency is increased by
varying the inflow rate, pulse cycles and intensity. Jigs may handle from 7 to 25 tons per hour, and
can handle particles ranging from 75 mm to 25 mm. At some operations, jigs are also employed hi
the cleaning stage. (Macdonald, 1983; Silva, 1986).
Shaking tables consist of small riffles over which a slurry containing fine ore is passed. The gold
settles into the riffles and, through a vibrating action, is directed to one side of the table where it is
collected. The tails are passed across the middle of the table or remain in suspension. Middlings, •
material that is partially settled, may be collected. Heads and .middlings are commonly reprocessed
on multi-stage tables. Shaking tables can handle materials from 15 am to 3.0 mm (EPA, 1988a;
Macdonald, 1983).
Spiral concentrator is a generic term referring to a method of separation rather a specific piece of
equipment. Ore concentrated from previous steps is fed with water into the top of the spiral and spins
down through the spiral. The heaviest materials are concentrated toward the center of the spiral while
lighter material moves to the outside. Concentrates are collected from the center of the spiral while
the tails pass down the entire spiral. Large operations may employ multiple spiral concentrators in
series to handle a wide range of sizes. Humphreys concentrators, as one example, can be used to
separate particles between 100 urn and 2 mm in diameter. These machines can handle low feed rates
(1.5-2 tons per hour) and low feed density (EPA, 1988a).
Centrifugal concentrators or bowls were typically used in dredges but may also be used in other
operations. Slurry is fed into the top of the circular machine. Driven from the bottom, the ulterior
portion spins on its vertical axis, driving the slurry against a series of concentric circular riffles or
baffles. The lighter material (tails) is driven up the side of the bowl while the heavy material
(concentrate) collects on the bottom or in the riffles (Cope and Rice, 1992).
Pinched sluices work on the concept that as a fine feed is exposed to an opening, the arc formed by
the heaviest particles dropping will be much narrower than the arc formed by the lighter materials. A
divider placed perpendicular to and below the pinched outfall lets heavy materials (concentrate) collect
on one side while lighter material (tails) can be collected and reprocessed separately or directed out of
the operation completely. Reichert cones, which are based on the pinched sluice principle, can handle
75 tons per hour and recover particles in the minus 10 to plus 400 mesh range (45 um to 0.5 mm)
(Gomes and Martinez, 1983).
3_17 September 1994
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ESA
Magnetic separation i^see Section 3.22) is not commonly used in gold placer mining but may be
...... • .............. : W1^ «*« ..... magnetite ...... is ..... a ..... component of the black sani .............. Ibis ...... technique is usedto remove
de<^StatIcaUy ^^^ taas fro* the neutral gold. To be effective, the method should involve
mutaple magnetic treatments followed by demagnetization steps so that the magnetite is removed
slowly, not in a 'magnetically coagulated* form, that may bind gold particles within it. Magnetic
separation, when used, is one of the final steps of beneficjation.
" • i " ......................................... - [[[ ' ..................... "l "12 ..... * ...... 1 ..... IIIIII ...... "; ....... II ........... 2IIiriZI~-I.~ ...... I' ..... II ..... - ....... I ..... • ...... I ...... ' ...... ''I ...... '
3.2.1.4 Sink/Float Separation "
* , ' i
..... ::::i^ ...... ^
...... ™foices *£ ..... H?^ tp s*?3^ the ...... various ..... minerals ...... pn ..... the basis of density. The separation is achieved by
^^ the ore to a tank containing a. medium whose density is higher than that of the gangue and
less than that of the valuable ore minerals. As a result, the gangue floats and overflows the
separation chamber, and the denser values sink and are drawn off at the bottom, often by means of a
^ devator or similar COIttrivan<:?: T^e s^ of material separated by this method varies, and is
l: OT *« densi|y a*1 viscosity of the medium. Because the separation takes place in' a
*» fc* d turbulence is minimized, effective separation may be achieved with a more
S2 !E! !fefc5°J* Siavity-separation techniques. .Viscosity does, however, place a
lS 2SP»«fcte size for practicable separation, since smaU particles settle very slowly
limiting the rate at which ore may be fed. Further, very.fine particles must be excluded, since' they
mix with the separation medium, altering its density and viscosity. Media commonly used for
stak/float sej^on in the ore milling industry are suspensions of very fine ferrosilicon or galena
^ rSS: SSSSSSS particles may be used to achieve medium specific gravities as high as
3-5, and are used m ^feyy-medium separation." Galena aUows the achievement of somewhat higher
pensjties of ore concentrate. • ' ". '
3.2.2 MAGNETIC SEPARATION
Magnenc separation is widely applied in the ore milling industry, both for extraction of values from
ore and for separation of different valuable minerals recovered from complex ores. Magnetic
separation is used in beneficiating ores of iron, columbium and tantalum, and tungsten. Separation is
based on differences in magnetic permeability (which, although small, is measurable for almost all
matenals) * effective r^ti not normally considered magnetic. The basic process
t .
mvolves *ansport of ore through a region of high magnetic-field gradient. The most magnetically
permeable particles are attracted to * moving surface, behind which is the pole of a large
«« « > out ..... of the main stream of ore. As the surface leaves the
.....
high-field region, particles are released into a hopper or onto a conveyor leading to further
processing.
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ELA. Guidelines for Mining '•' Overview of Mining and Beneficiation
For large-scale applications, particularly in the iron-ore industry, large rotating drums surrounding the
magnet are used. Although dry separators are used for rough separations, these drum separators are
most often run wet on the slurry produced in grinding mills. Wet and crossed-belt separators are
frequently employed where smaller amounts of material are handled. '
j
3.2.3 ELECTROSTATIC SEPARATION
Electrostatic separation is used to separate minerals on the basis of then* conductivity. It is an
inherently dry process using very high voltages. In a typical application, ore is charged at 20,000 to
40,000 volts, and the charged particles .are dropped onto a conductive rotating drum. The conductive
particles lose their attractive charge very rapidly and are thrown off and collected, while the
non-conductive particles keep their charge and adhere by electrostatic attraction. They may then be
removed from the drum separately.
3.2.4 FLOTATION
Basically, flotation is a process where the addition of chemicals to an ore slurry causes particles of
one mineral or group of minerals to adhere preferentially to air bubbles. When air is forced through
a slurry of mixed minerals, the rising bubbles carry with them-the particles of the mineral(s) to be
separated from the matrix. If a foaming agent is added which prevents the bubbles from bursting
when they reach the surface, a layer o? mineral-laden foam is built up at the surface of the flotation
cell which may be removed to recover the mineral. Requirements for success of the operation are
that particle size be small (typically flour-sized or less), that reagents compatible with the mineral to
be recovered be used, and that water conditions in the cell, not interfere with the attachment of
reagents to minerals or to air bubbles;.
Flotation concentration has become a mainstay of the ore milling industry because it is adaptable to
very fine particle sizes of less than 0.01 mm (.0004 in.). It also allows for high rates of recovery
from slimes, which are inevitably generated in crushing and grinding and which are hot generally
amenable to physical processing. As a physico-chemical surface phenomenon, it can often be made
highly specific, allowing production of high-
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Oyq^iew of Inning and Beneficiation _ _ EIA Guidelines for Mining
j
the bubbles to create a foam which may be effectively recovered from the water surface. Activators
enhance the attachment of the collectors to specific kinds of particles, while depressants prevent such
ffi±BBi ........... ...... ,ffi fe^^y *** to a*1™ &<>&*<>* of particular minerals that have been -
depressed * «n earner stage of the milling process. In almost all cases, use of each reagent in the
S2 ...... S ...... ,?ffi ...... JS« generally less than 0.5 kg (approximately 1 Ib) per ton of ore processed; at large-
capacity mills, the total reagent usage can be high, since tens of thousand of tons of ore per day may
be beneficiated. , The bulk of the reagent adheres to tailings or concentrates.
Sulfide minerals .are all readily recovered by flotation using similar reagents in small doses, although
reagent requirements and ease of flotation do vary throughout the class. Sulfide flotation is most
often carried out at alkaline pH. Collectors are most often alkaline xanthates having two to five
"ckbon atoms— for example, sodium ethyl xanthate (NaSjCOCzH). Frothers are generally organics
, with a soluble hydroxyl group and a "non-wettable" hydrocarbon. Sodium cyanide is widely used as
a pyrite depressant. Activators useful in sulfide-ore flotation may include cuprous sulfide and sodium
sulfide. Other pyrite depressants which are less damaging to the environment may be used to replace
the sodium cyanide. Sulfide minerals of copper, lead, zinc, molybdenum, silver, nickel, and cobalt
are commonly recovered by flotation.
» i . | ( , .
^
Minerals in addition to sulfides may be recovered by flotation (e.g., oxidized ores of iron, copper,
manganese, the rare earths, tungsten, titanium, and columbium and tantalum). Generally, these
flotation processes are more sensitive to feed-water conditions than sulfide floats; consequently,
oxidized ores can less frequently run with recycled water. Flotation of these ores involves very
different reagents from sulfide flotation-and may require substantially larger dosages. Reagents used
include fatty acids (such as oleic acid or soap skimmings), fuel oil, and various amines as collectors;
and compounds such as copper sulfate, acid dichromate, and sulfur dioxide as conditioners.'
3.2.5 LEACHING
«
Leaching is the process of extracting a soluble metallic compound from an ore by selectively
diving * m a wfeMe solvent such as water, sulfuric hydrochloric acid, or sodium cyanide
solution- "H* ^ired metal is men removed from the "pregnant" leach solution by chemical
P«cipftati°n or omer chemical or electrochemical process. When ores are (or can be) so fractured or
scattered m tenure that air and water can be made to percolate through them as they exist in the
ground, then the ores can be profitably leached in-situ (in place) without being mined. Ores that are
mined, but arc too low in grade to justify the cost of milling, can be recovered by placing the ore
rock in large piles on an impermeable surface and treating them with the leach solution, which is
collected through a drain system at the bottom of the pile. This method is termed "heap" or "dump"
leaching. Heap leaching is widely used in the gold industry, dump leaching in the copper industry.
Vat or tank leaching is similar to heap leaching, with the exception that the ore rock is placed in a
3-20 September 1994
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EIA Guidelines for Mining Overview of Mining and Beneficiation
container (vat) equipped for agitation, heating, aeration, pressurization, and/or other means of
facilitating the leaching of the target mineral.
Ores can be leached by dissolving away either the gangue or the value in aqueous acids or base,
liquid metals, or other special solutions. Typical leaching situations include:
• Water-soluble compounds of sodium, potassium, and boron which are found in arid climates
or under impervious strata can be mined, concentrated, and separated by leaching with
water and reciystallizing the resulting hrihes.
• Vanadium and some other metals form anionic species (e.g., vanadates) which occur as
insoluble ores. Roasting of such insoluble ores with sodium compounds converts the values
to soluble sodium salts (e.g., sodium vanadate). After cooling, the water-soluble sodium
salts are removed from the gangue by leaching in water.
• Uranium ores are only mildly soluble in water, but they dissolve quickly hi acid or alkaline
solutions.
>
• Native gold which is found in a finely divided state is soluble in mercury and can be
extracted by amalgamation (i.e., leaching with a liquid metal).
• Nickel can be concentrated by reduction of the nickel with ferrosilicon at a high
. temperature and extraction of the nickel metal into molten iron. This process, called
slop-ladling, is related to liquid metal leaching.
• Certain solutions (e.g., sodium cyanide) dissolve specific metals (e.g., gold) or their
compounds, and leaching with such solutions immediately concentrates the values.
\
Leaching solutions can be categorized as strong, general solvents (e.g., acids) and weaker, specific
solvents (e.g., cyanide). The acids dissolve certain metals present, which often include gangue
constituents (e.g., calcium from limestone). They are convenient to use, since the ore does not have
to be ground very fine, if at all (i.e., approximately 5 to 30 cm (2 to 12 mches) in diameter), and
then separation of the tailings from the value-bearing (pregnant) leach solution is not difficult. In the
case of sulruric acid, the leach is cheap but gangue constituents hi addition to the value are dissolved.
Specific solvents attack only one (or, at most, a few) ore constituents), including the one being
sought. Ore must often be crushed or finely ground to expose the values, although this is not always
necessary.
Countercurrent leaching, preneutralization of lime in the gangue, leaching in the grinding process,
and other combinations of processes that simplify or improve the effectiveness of the leaching
3-21 September 1994
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, i „: | ; ; ; i ;
i ,
-j , , ', 'J: , ,
• Overview of Mining and Beaeficiation ETA Guideline*: for Mining
. ' > ( i
I
prtjcedure are often seen in the industry.. The values contained in the pregnant leach solution are
recovered By one of several methods, such as: . '
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Precipitation. The process of separating mineral constituents (i.e., values) from a solution
by chemical means, by evaporation, or by changing the temperature and/or pH of the
solution. • '
Electrowinning. The recovery of metal values from solutions by an electrochemical
process similar to electrolytic refining. Insoluble (long-life) anodes are used, with the
desired metal produced as or on a cathode.
• Carbon Adsorption. The target mineral is adsorbed onto activated carbon and further
concentrated.
. - , . •• "• • ' , ,' • •, • il
• Cementation. The process by which a metal is precipitated or "cemented" out of solution
B | as a finely divided metallic product by Replacement with less active^metal. For example,
"=:'~"""'"•"' : =l": ""' wfraT'copper s5SoiT(Cj3o§ ¥brougji into contact ^fli scrap tonplates^ (Fe),'the
SJpjgSf" j™^^ jg£ g^j oiFrae scrap plates ^g g£ j^— ~— g- s'ojjtipn _...__i_ ^^
: copper is then removed by washing the scrap plates.
Amalgamation represents a special application of leaching and/or the recovery of the leached mineral.
Amalgamation is a Pjcpcess by_ which mercury, in its natural liquid state, is alloyed with some other
metal to produce an "amalgam" (a solution containing mercury and another metal(s) in liquid form).
This process is applicable to free milling precious metal ores, which are those in which the ore is
lllliiB IH!'1 free, relatively coarse, and has clean surfaces. The current practice of amalgamation in the United
States !2 ISBlSli fp, SHPH-scate barrel amalgamation of a relatively small quantity of high-grade,
gravity-concentrated gold ore. The gravity concentrate" is ground hi an amalgam barrel with steel
balls or tods before mercury is added. This mixture is then gently ground to bring the mercury and
gold into intimate contact. The resulting amalgam is collected in a gravity trap. Although the
amalgamation process has, in the past, been used extensively for the extraction of gold and silver
fi^jBverlzediores, m recent years it has largely been superseded by cyanidation processes, as
: described in Section 3.3.1.
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£i&£ Siiiil3All0fi,1ffi4Slls AND WASTE MANAGEMENT
Tgilings are the wastes generated in by far the largest quantities by beneficiation operations that use
flotation and gravity separation. This section describes the most common method of managing and
disposing of tailings from metal mines. Tailings from gravity separation are described in the
discussion of gold placer mining hi Section 3.3.2. Leaching operations also generate enormous
quantities of spent ore and small quantities of process solutions: the management of wastes from heap
leaching is described in the discussion of gold mining (Section 3.3.1), the industry sector hi which
heap leaching is most commonly practiced; the management of wastes from dump leaching is
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3-22 September 1994
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E1A Guidelines, for Mining Overview of Mining and Beneficiation
. described in the discussion of copper mining (Section 3.3.4), the industry sector .in which dump
leaching is most commonly practiced.
Tailings are the coarsely and finely ground waste portions of mined material that have been separated
from the valuable minerals during beneficiation (crushing, grinding and concentration). By far the
larger proportion of ore mined in most industry sectors ultimately becomes tailings that must be
disposed of. In the gold industry, for example, only a few hundredths of an ounce of gold may be
produced for every ton. of dry tailings generated. Similarly, the copper industry and others typically
mine relatively low-grade ores that contain less than a few percent of metal values; the. residue
becomes tailings. Thus, tailings disposal is a significant part of the overall mining and milling
operation. The physical and chemical nature of tailings varies according to the ore being milled and
the milling operations used to beneficiate the ore. The method of tailings disposal is largely
controlled by the percent water content of the tailings. Generally, three types of tailings may be
identified based on then: water content; wet, thickened and dry.
Most ore milling processes require the use of water to classify (grinding stage) and concentrate the
valuable minerals. Although dewaterihg of tailings is a common final step prior to the transport and
disposal of the tailings, an equal or greater weight of water remains with the solids in a slurry
mixture. These tailings are known as wet tailings. More recently, some mills have begun to
significantly dewater tailings to where only 40 percent of their total weight is water. These tailings
are known as thickened tailings.
A few beneficiation operations, such as magnetic separation, may require little or no water for
preparing the ore. Tailings beneficiated with these methods are normally known as dry tailings.
Magnetic separation extracts magnetic minerals, such as iron, from the nonmagnetic particles, which
remain as tailings. Although tailings from beneficiation operations may be considered dry tailings,
they may contain a small weight percentage of water. In addition to the specific beneficiation
operations that produce dry tailings, belt filtering (which removes liquids from tailings by transporting
the tailings on a cloth belt over a vacuum box) results hi tailings with only 20 to 30 percent total
weight in water. These tailings are also considered to be dry tailings.
3.2.6.1 Mine Backfilling
Slurry tailings are sometimes disposed in underground mines as backfill to provide ground or wall
support. This decreases the above-ground surface disturbance and can stabilize mined-out areas. For
stability reasons, underground backfilling requires tailings that have a high permeability, low
compressibility, and the ability to rapidly dewater (i.e., a large sand fraction). As a result, only the
sand fraction of whole tailings is generally used as backfill. Whole tailings may be cycloned to
separate out the coarse sand fraction for backfilling, leaving only the slimes to be disposed in an
3-23 September 1994
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1 . • • !'
Overview of Mining and Beneficiation EIA Guidelines for Mining
— -- - , , , . • . — - j ; —— T-
i iii in
kopoundmem. To increase structural competence, cement may be added to the sand fraction before
backfilling (Environment Canada, 1987).
i ill iiii in i i iniii 1 1 in i in i n in i 1 1 iiiiiiiiiiiiiiiiiiii iiiiiiiii i ii mil nil Mini i IIP ill 111 i , i ill
3.2.6*2 Subaqueous Disposal
Subaqueous disposal hra permanent body of water such as a lake, the ocean, or an engineered
structure (e.g., a pit or impoundment) is also a possible disposal method. The potential advantage to
underwater disposal is that it may prevent the oxidation of sulfide minerals in tailings, thus
prohibiting acid generation. However, there is substantial uncertainty regarding other short- and
long-term effects on the water body into which the tailings may be disposed (Rawson Academy 1992;
U.S. Bureau of Mines 1992). Canada's Mine Environment Neutral Drainage (MEND) program is
currently studying subaqueous disposal.
inr Ifoji ...... tsnch-scale ...... 16-year simulation of deep-lake disposal using Ottawa River water by CANMET .
^~. ; ^(Canadian ..... Centre ...... for ..... Mineral ....... and ..... Energy Technology), Ritcey and Silver (1987) found that the •
...... °IL25 ...... —IS?. ..... SBLSES ...... 22* ..... ll°,w, ...... XM^LSSS!!: ........... £JPley» etal- (1978), .
found ...... that ..... te ..... taHSoigs ...... ^ ..... cover ...... ia'axeas'onihe ocean ..... or lake floor and ...... cause ..... turbidity problems if
the ..... disposal practice is not designed correctly. There" are' little, data on the long-term efficacy and
environmental effects of subaqueous "disposal ...... (Environment Canada, 1987), although this issue is '
lllin^ ....... _ liiH Illlllllll llilllilllll iiilllH llllllH^ i 1 ill I in iiiiiiii|iiii i iiiiiiiiiiiiiiiiin I in i in in in PIT i i ..... mil i 1 1 iiiiiiiii in i i i ...... in iiiiii in
being intensively studied in Canada.
Subaqueous disposal recently has been practiced by eight mines in Canada, where its use predated
current regulations. Three of these mines still were active aid disposing of their tailing underwater
(two in lakes, one in the ocean) as .of 1990 (Environment Canada, 1992), as were a number of mines
n dsjwhere m the worjd.,; In the United Staffs, regulations under the Clean Water Act (e.g., the
effluent limitation guidelines for mills that beneficiate base and precious metal ores) effectively
t prohibit subaqueous" disposal of tailings in natural water bodies (i.e., any discharge to "waters of the
iii'''! ••'! !" I'ji iii .U.S.'*). The use of subaqueous disposal in engineered structures has not been tried in the U.S.,
i V 11,1 ||| i gli i ii i 111 Ik 'I 111 Jlllllllllllllllllllni' lilllllllillll11 lill illiililiillllliiWlllliillllllllllflllil Vllllllilliniiinilliiiiiiiiiiiiiiiiiiiiffli nnnnnniiiiiijiiiiiiiiijiiiiniiiiiiiniiiniiijiiiii' 11 \ iinniiiiiiiii«i«iiii iiii uii iiii nil iiiiHii "iiinii.11,', ii ni Hi" mi iiiiiiiii iiiiiii'iiiini, iiiiiii, 111" mil, 'jiiniijiiiiini i 'iminii'' I'iiiiniiHiPiigii1 in wuiiF Niii'iiniii NIIIR niixii;1i,:««
' .^oug" i«. ^ been proposed in at least one case.
3.2.6.3 Tailings Impoundments
i Because mine tailings produced by the mill are usually in slurry form, disposal of slurry tailings hi
impoundments made of local materials is the most common and economical method of disposal.
There are four main types of slurry impoundment layouts; valley impoundments, ring dikes, in-pit
ttBpoundments, and specially-dug pits (Ritcey, 1989). The impoundment design choice is primarily
.dependent upon natural topography, site conditions, and economic factors. Because costs are often
directly related to the amount of fill material used in the dam or embankment (i.e., its size), major
sayings can be realised by minimi-yinc the size of the dam and by marimiring the use of local
materials, particularly the tailings themselves. Leakage from tailings impoundments is a serious and
3-24 September 1994
it 11 him iiiiiiiii i |iiiiiiiiiii • i ii in in in i ii n i n i in i in i 11 i i i iniii ii i 11 i r |ln 11
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EIA Guidelines for Mining . Overview of Mining and Benefiriation
ongoing environmental problem at many operating mines. Any leakage can transport contaminants to
ground or surface water; uncontrolled leakage can threaten the integrity of the impoundment structure
itself. .Increasing numbers of impoundments are lined, with or without leachate collection systems.
Although this reduces the risk of leakage, at least in the short term, the long-term integrity of liners is
as yet untested, particularly following mine closure when routine inspections and maintenance may be
reduced or eliminated.
There are two general classes of impounding structures: water-retention dams and raised
embankments. The choice of impounding structure is influenced by economics and site-specific
factors including the characteristics of the mill tailings and effluent. In general, impoundments are
designed to move, or control die movement of, fluids both vertically and horizontally.
Water retention dams are constructed to men* final height before the impoundment begins to receive
tailings. The design and construction of these impoundments is similar to conventional earth dam
technology. A typical design includes an impervious core, downstream filter and drainage zone and
upstream riprap. Upstream slopes are often steeper than those required for a water storage dam
because rapid drawdown is not experienced. This impoundment type is best suited for tailings
impoundments which must retain large water volumes. Ponds which may require this type of
impoundment construction include those that receive large volumes of storm water runoff or store mill
effluent not recu-culated back to the mill process.
Raised embankments are constructed over die life of the impoundment and are initially begun as a
starter dike constructed of native soils or borrow materials including waste rock and tailings.
Embankment raises are constructed to keep pace with die rising elevation of die tailings and
floodwater storage allowance. The embankment raises may be constructed using a variety of
materials including tailings, overburden and native soil and may be positioned downstream, upstream
or directly on top of die starter dike.
The three most common methods used to construct tailings embankments are upstream, downstream
and centerline. Upstream construction begins with a starter dam constructed at die downstream toe of
die planned impoundment, with tailings discharged peripherally from die crest of die starter dam
using spigots or cyclones. This deposition develops a dike and wide beach area composed of coarse
material which in turn becomes die foundation of die next dike. Some type of mechanical compaction .
of die dike is typically conducted before die next stage of die dam is constructed.
As in upstream construction, downstream construction also begins with a starter dam constructed of
compacted borrow materials; however, this starter dam may be constructed of pervious sands and
gravels or with predominantly silts and clays to minimize seepage through die dam The downstream
method is so named because subsequent stages of dike construction are supported on top of die
3-25 September 1994
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, ,,, , , .QjBZfeg gC JffiBgg sad Beneficiation EIA Guidelines for Mining
ne ctf^the^top of the dam downstream as
progressively ^^^ Peripheral spigotting and on-darn cycloning and spreading
, i ...... i ...... ..................... " ..... inn ...................... iS .............................. ' ................... An ........................ ............................ 3?
^ are common depositional methods used for downstream embankments. .Again, some type of '
' ''' '
1!" 4IK^ k jii.i; ti IP * in: iiii" liiiyiiiiiiiiiliiiiiiiiii'lniiniiiiijiniiiii'' dp •iiii'ili'aiiiiiiiiii i<<«iiiiii»i iniiiiii^ "i?"' :i|ii Jini'iiiiiii aiiiii apTiijiti . Iiii* pii'iiiiiri111!;! IK , , ,! "' • PIHIIIPIIIIF '>, "m < ,i'' nlniiiiiiii'iiiiiiiiniintiiiiiiiiiiiiiiiiivi' SSi ':'" '* " 4iii:':!!iiriiiiii
^S^S^Snn^ffil^n § SiSS IS ^^•!&8i5S!£Sm, SSilirf.SSSSESS SSSiSSJSS SSSiSignS iterf, r,
beach. The centerline of the embankment is maintained as fill and progressive raises are placed on
bolh the beach and downstream face. The tailings placed on the downstream slope are typically
compacted to prevent shear failure. •
- • • "= • Ir i; "
ii lHB!tn^ Ki lliiilV, Jllliiiil! mj fillip ,« iiliiHi: hii^ iilii liiiii S '1iii,iiiijl. liiini iiiiili: iiniii^ i'iiiiiil
Other things being equal, it is economically advantageous to use natural depressions to contain
-tailings. Among other advantages are reduced dam size, since the sides of the valley or other
depression serve to contain tailings. In addition, tailings hi valleys or other natural depressions
111:1',,'' ..... "I."" ....... ' ......... present less relief for air dispersion of tailings material. :" ' ' ' :
............................ j ............................ v?|ify impoundments (and ..... vanations^are^the ...... most ...... commgnly used nnppundments. There are several
variations of vaUey-type unpoundinents. The Cross-Valley design is frequently used because it can be
applied to almost ,any topog^b^_de|^sion ..... in ..... either ...... single or multiple form. Laid out similarly to
a conventional water-storage ...... dam, ........ the dam ...... fs ...... TOnsttucted ...... ajgnecting two valley walls, confining the
tailings in the natural valley •topography. This configuration requires the least fill material and
consequently is favored for economic reasons. TJhe imjwundment "is best located near fee head of Ae •
.................. drainage basin.to minimize flood 'inflows. Side hill diversion ditches'may be used to reduce normal •
• IIIIIIIIH I"1" " iiliiiiiiiiP ...... ' ..... ' ..... ' .............. ...................................... — — — .~ ........ .v»»w ....... uw*.u«u
' ..... ",?x£ffiraa; ...... Sssi ...... 222!, ..... ..... 52 ...... *sss*&*s* ...... 51°!?!? ...... "'
spillways, or separate water-control dams located upstream of the impoundment.
..... n,,
.iiiiiiiiiiiiiiniii" iiiiiin1 "i i 'in, nip,:
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ELA Guidelines for Mining Overview of Mining and Beneficiation
V
Where natural topographic depressions are not available, the Ring-Dike configuration may be
appropriate. Instead of one large embankment (as in the valley design), embankments (or dikes) are
required on all sides to contain the tailings. Construction can be similar to valley dams, with tailings,
waste rock, and/or other native materials typically used in later phases of construction. Because of
the length of the dike/dam, more materials are .necessary for this configuration, and material for the
initial surrounding dikes is typically excavated from the impoundment area.
Open-pit backfilling is also practiced, where tailings are deposited into abandoned pits or portions of
active pits. The Pinto Valley tailings reprocessing operation, located in Arizona, uses this method to
dispose of copper tailings. In active pits,, embankments may be necessary to keep the tailings from
the active area. However, since seepage from the tailings can adversely affect the stability of the pit
walls or embankments, it is umis"ai to see disposal in active pits. Williams (1979), for example,
discusses a failure due to pore water pressure in the floor of a pit in Australia. Ritcey (1989) notes .
that the hydrogeological parameters affecting the migration of seepage and contaminants are poorly
. understood, so tailings with toxic contaminants or reactive tailings may be poor candidates for this
type of impoundment. This method is much less common than the valley and ring-dike
impoundments. Since the tailings are protected by pit walls, wind dispersion is minimized. Good
drainage can be incorporated into the design. Many of the .failure modes common to tailings
embankments (e.g., piping,, liquefaction) do not apply to this design. The lack of dam walls reduces
the possibility of slope failure, but the stability of the pit slopes do have to be checked.
Specially dug pit impoundments are fairly unusual and involve the excavation of a pit specifically for
the purpose of tailings disposal. The impoundment consists of four or more cells with impermeable
liners surrounded by an abovegrade
-------
ill I
Overview of Mining and Benefioafum ' EIA Guidelines for Mining
""7™ : \ : : :;; : : : ™- : : : :: : ' ;:i \ :;: : : • : .
Tailings slurry (wet tailings and thickened tailings) is usually abrasive and highly viscous, which
presents complications for the design, construction, operation and maintenance of tailings transport
systems. Slurried tailings may be transported from the mill to the tailings pond by gravity flow
and/or pumping through open conduits or pipes. Pipe wear is a significant problem that may be
mitigated by the use of rubber lined steel pipes or high-density polyethylene pipe. The transport
system may become plugged with settling solids if the minimum flow velocity is not maintained or if
5^^5:;= provisions are not made for pipe drainage during mill shutdowns. Tailings may be discharged'from
tbe conveyance system to any location along the impoundment perimeter; however, as discussed
ily, tailings (particularly sand'tailings) spigotted along raised embankments may provide •
additional stability.
Ill 111 I IIIIIIIIIH Illllllllll I II I 111 111111 III 111 11111II III III 111 III I I 111111 II Illllllllllll • .
IIH^ . . 11 ill 111 W II lllllllllllllllllll IN ll 111 11 • I 111 1 11 ill 1 PI 111 1 llillllll KIIH1111W^^^ S: . "•;:> JSKtt. :, ( i ili'S s/Si! I
z^um&ss* Siting of tailings impoundments may be influenced by a number of factors, including location and
j the mill, topography, hydrogeology and catchment area,
groundwater. layout' of impoundments may be virtually independent of lie type of embankment used
to confine it. Essentially any of the embankment types or raising methods discussed previously may
, be used, provided that the embankment type is compatible with site-specific conditions and the
sB^^Bfssi characteristics of mill tailings and effluent.
i^::^;.; 3.2.6.4 Dry Tailings Disposal
.
* ' < , . . .. , : ' [ ,
In some cases, as noted above, tailings are dewatered (thickened to 60 percent pulp density or more)
or jdrieg (to a mogture content of 25 JMrcent or .below) priorto disposal. The efficiency^ and
applicability of using thickened or dry tailings depends on the ore grind and concentrations of gypsum
and clay as well as the availability of alternative methods. Except under special circumstances, these
methods may be prohibitively expensive due to additional equipment and energy costs. However, the
advantages include minimising seepage volumes and land needed for an impoundment or pile, and
simultaneous tailings deposition and reclamation (Vick, 1990).
Tailings piles are non-impounding structures that are designed for the disposal of dry tailings or
thickened tailings. Dry tailings piles are considerably different from tailings piles created as a result
Mfi 1 (111| •II Illlllllll w^» Illilpir it liiBiiiSi i ,-> i . , ,
•WMlf" If of thickened tailings disposal. Dry tailings may be disposed of in piles that may be constructed in a
variety of configurations. These include: a valley-fill, where tailings are simply dumped to in-fill a
valley; side hill disposal, where tailings are disposed on a side of a hill in a series of piles; and level
piles that may grow as lifts are added through out the life of the mine. The maxjmuiri slope of
tailings piles is determined by the physical and chemical characteristics of .the tailings.
Thickened tailings are typically spigotted as a very viscous slurry from a permanent discharge line,
creating a conical pile. No embankments are needed with the exception of a small dam constructed
down stream from the piles to intercept and collect seepage. This method of disposal may be best
suited for areas close to the mill and with low relief topography.
•nun iiiiiiiiiiiiiiiiiiiiini i iniii 11 ii inn iiiiiiiiiiiiiiiiini n inn in inn iiiiiiiiiiiiiiiiiiiiini 111111111111111 nnnnnnnnnnnnnnnnnnii iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii i iiiiiiiiiiiiiiiiiiiiiiii inn mi iiiiiiiiiiiiini n iiiiinnnnn nnnninn mi nninnnnnnnnn nnnnnnnnnn iniinii mi mm mm n iniiiii n ninnim nun mi nun iniiinn nn «i Sin in i n n
nnnnnninnnnnnnnnn in nun inn mi i linn iniinnn i n nun in i innnnnnninn nnnninn mi mini mini inn i minimi minim n mmmlmmmnm minium mi ninniinnnn i ninnim minimi i in mi in inn in mm in i nnnninn nniinnnninn n mini inn iinlnin ininnii nn mini mm in iiiinni n iniiiii inn inn mm mm in mm mini i i i II
3-28 September 1994
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EIA. Guidelines for Mining Overview of Mining and Beneficiation
33 COMMODITY-SPECIFIC MINING AND BENEFICIATION PROCESSES
The remainder of this section describes the mining and milling of specific metal ores, with individual
ores discussed in separate subsections. The ores and industry sectors discussed in the following
subsections include gold and silver (Section 3.3.1), gold placer (3.3.2), lead-zinc (3.3.3), copper
(3.3.4), iron (3.3.5), uranium (3.3.6), and other ores (3.3.7). The industry sectors discussed hi more
detail (hi Sections 3.3.1 through 3.3.6) are those representing the most mining activity hi the United
States as of the early 1990s. Although EPA has developed effluent limitations guidelines for other
industry sectors, there are few (and in some cases, no) actives mines for the other sectors, including
molybdenum, tungsten, and mercury.
3.3.1 GOLD AND SILVER
Historically, gold has been the principal medium of international monetary exchange, although its role
has changed significantly to recent years. Between 1934 and 1972, the United States monetary
system was on a gold standard at .a fixed rate of $35 per troy ounce (a troy ounce equals 1.09714
avoirdupois ounces, so there are 14.6 troy ounces per pound). After leaving the gold standard hi
1975 and allowing private ownership of the metal, the U.S. gold market grew rapidly arid the price of
gold peaked at $850 per ounce hi January 1980. Prices are notoriously volatile and gold prices are
set on a number of world exchanges. In the 1990s, gold has generally traded hi the $300 to $400 per
troy ounce range.
In 1992, U.S. gold operations produced an estimated 10.3 million troy ounces of gold from ore,
valued at $3.6 billion. This represented an increase of 10 percent over 1991 production and nearly a
tenfold increase over production hi the early 1980s, which averaged less than 1.5 million troy ounces
annually. An estimated 70 percent of 1992 gold production was used for jewelry and art (including
coinage), 23 percent for industrial purposes (primarily in the electronics industry), and 7 percent hi
dentistry (Bureau of Mines, 1986a and 1993).
Many new gold mines opened hi the United States throughout the 1980s (24 hi 1989), and mines
continue to expand their production capabilities. The United States is now the second largest gold
producer in the world. According to the Bureau of Mines, there, are about 200 lode gold mines hi the
United States, primarily in the west, and a dozen or more large placer mines hi Alaska (plus hundreds
of small commercial placer mines hi Alaska). In addition, there are hundreds or thousands of
"recreational" lode and placer gold mines that may operate periodically (Bureau of Mines, 1993).
Gold has been mined hi virtually every State but production has been concentrated hi 15: Alaska,
Arizona, California, Colorado, Idaho, Michigan, Montana, Nevada, New Mexico, North Carolina,
Oregon, South Carolina, South Dakota, Utah, and Washington. According to the Bureau of Mines,
approximately 10 percent of gold production is produced as a by-product of other mining, with the
3-29 September 1994
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Oyerriew of Mining and Benefication
EIA Guidelines for Mining
reBSainder produced at gold mines. In 1991, about 61 percent.of newly mined domestic gold from
gold mines (or 5.7 million troy ounces) was mined in Nevada, 10 percent in California, 6 percent in
both Montana and South Dakota, and 1 percent in Colorado, Arizona, Alaska, and Idaho. The 25
Soldroducngmnes ™ 1991
5 ...... Inhibit 3-L ................ These ..... mines ..... accounted,,,,
and 1993).
Like gold, silver has been a prihcqwl medium of international monetary exchange. Silver, however,
is aiso an important metal in many other applications. Mine production in 1992 exceeded 57 million
E°*!cea ...... <*5FJ!1 ..... PEE??! ..... °£,i?5 ...... !2!?!z ....... flowed, by Idaho (16 percent), ' -
....... ...... .iZ ..... P5E5Q: .............. AJxjut ...... 50 percent of silver is used m manufacturing
photographic products, 21 percent in electrical and electronic products, and 20 percent for a variety
of othe!,,,?55? ....... ®iHi ...... ?lMii5,! ........ l?^3!: ............. Ii*?* 3-2 identifies ...... the ..... U.S. ....... mfne§ ...... |ha| produced the most
silver in 1991; several of ''these have since closed, either permanently or temporarily.
Prices for silver also peaked in the early 1980s, but have been severely depressed in recent years.
^ Sussed Price (generally in the range of $4 to $5 per ounce) has resulted in a significant
«*£tfgnj5 saver mining: almough silver is produced by over 150 U.S. mines (Bureau of Mines,
1993), it is mined now only in conjunction with other metals, notably gold and copper. At the
P*?8^* 1™?* tfcere is essentially no mining in the U.S. whose primary target is silver. This section
focasses on gold since silver is now recovered by U.S. operations only with gold or with other metals
that are discussed in, .separate sections. (Although ..... BcMKt 3k2 ..... Identifies ..... :severa|,,,,,llllnes ....... whose silver is
derived from "silver ore," in every case only the other metals recovered make recovery of silver
*«. k*A«^ fcT "fc* i i fc>-^^ » J. *^J\J\J LW
deep) are called epithermal deposits, while those formed deeper are called mesothennal
i - • „ - ... ;i, b f ,
-------
EIA Guidelines for Mining
Overview.of Mining and Beneficiation
Exhibit 3-1. Twenty-Five Leading Gold-Producing Mines in the United States, 1991 1
Rank
1
2
2
4
' 5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
' " ' '<':* '"\ ,
Mine. >- ,
Nevada Mines Operations
Goidarike
•** .»_ _. ,^*_^_— ^—
HiHpmfiT CagyoB
lends Canyon (Bnfidd Bell)
Snxfy Va3eyComaoa€pea&aB
Hotncstflifff
McCoy and Cove
Mclaughlin
Chimney Creek
Fortitude and Surprise
Bulldog
Mesqufte
Getchell
Sleeper
_annon
Ridgeway
Tamestown
Paradise Peak
Rabbit Creek
iarney's Canyon
Continental
Zonman-Landusky
3olden Sunlight
Vind Mountain
Fbley Ridge & Annie Creek
County and State
EQcD and Eureka UV
EateSaSiF
SaltLaieUT
HkoNV
N»eWV
LzwKoeeSD
Lander NV
NapaCA .
HumboldtNV
Lander NV
HyeNV
LnperialCA
HumboldtNV
HumboldtNV
ChelanWA
FairfieldSC
fuolumne CA
NyeNV
HumboldtNV.
Salt Lake City UT
Silver Bow MT
Phillips MT
efrerson MT
WashoeNV
Lawrence SD
Oponrtor
Nfiwsoflt Gold Co.
Barrick Mercury Gold Mines Inc.
Kennecott-Utah Copper Corp:
Freeport-McMoran Gold Co.
Round Mountain Gold Corp.
Hmffcstflkc Mining Co
Ecbo Bay Mining Co.
Homestake Mining Co.
Gold Fields Mining Co.
Battle Mountain Gold Co.
Bond Gold, Bullfrog, Inc.
Goldfields Mining Co.
FMG Lie.
Amax Gold Inc.
Asamera Minerals (U.S.) Inc.
Ridgeway Mining Co.
Sonora Mining Corp.
FMC Gold Co.
Rabbit Creek Mining Inc.
Kennecott Corp.
Montana Resources
Pegasus Gold Inc.
Golden Sunlight Mines Inc.
Amax Gold Inc.
Wharf Resources
Source of
Gold
Gold Ore
Gold Ore
Copper Ore
Gold Ore
Gold Ore
Gold Ore
Gold Ore
Gold Ore
Gold Ore
Gold Ore
Gold Ore
Gold Ore
Gold Ore
Gold Ore
Gold Ore
Gold Ore
Gold Ore
Gold Ore
Gold Ore
Gold Ore
Copper Ore
Gold Ore
Gold Ore.
Gold Ore
Gold Ore
Source: Bureau of Mines, 1992.
1
3-31
September 1994
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Overview of Mining and Benefidation
EIA Guidelines for Mining
Exhibit 3-2. Twenty-Five Leading Silver-Producing Mines in the United States, 1991
I
i
Rank
1
2
3
4
S
6
7
S
9
' 10
11
'12
13
14
15
16
17
18
19
20
21
22
23
24
25
!:-:?z.v-'ite^$$?'&.
McCoy and Cove
Greens Creek
Rochester
Rrnoham CaTWffll
Tray
Red Dog
Sunshine
Lucky Friday
DeLanar
Paradise Peak
Galena
Montana Tunnels
Mission Complex
WhJtePine
^andclaria
Coodoeotal
Ray Unit
Demon-Rawhide
j^nrtman-I^fxty^fcy
kforcnci
Bagdad
San Manuel
Baale Mountain Complex
Chino
Pinto Valley
s--vii."'::, '-:' . U *
• COiiilty MDu Stiklt
Lander NV
Admiralty Island AK
PershingNV
Salt Lake UT
Lincoln MT
NW Arctic AK
SboshonelD
ShoshonelD
OwybeelD
NyeNV
ShoshonelD
Jefferson MT
Puna AZ
OotbnogonMT
Mineral NV
Silver Bow MT
Final AZ
Mineral AZ
Phillips MT
GreenleeAZ
YavapaiAZ
PinalAZ .
Lander NV
Grand MM
GflaAZ
. .* ,: f\nm*ilt ii • ' ,'"'•'•• '
• ^ f uptnuar •, .' •'
Echo Bay Mining Co.
Greens Creek Mining Co.
Coeur Rochester Inc.
Kermecott-Utah Copper Co. •
ASARCOInc.
Cominco Alaska
Sunshine Mining Co.
Hecla Mining Co.
NERCO De-Lamar Co.
FMC Gold Co.
ASARCOInc.
Montana Tunnels Mining Inc.
ASARCOInc.
Copper Range Co.
NERCO Metals Inc.
Montana Resources Inc.
ASARCOInc.
Kennecott Rawhide Mining Co.
Pegasus Gold Inc.
Phelps Dodge Corp.
Cyprus Bagdad Copper Co.
Magma Copper Co. '•
Battle Mountain Gold Co.
Phelps Dodge Corp.
Magma Copper Co.
Source: Bureau of Mines, 1992.
Source of Silver
Gold Ore
Zinc Ore
Silver Ore
Copper Ore
Copper ore
Zinc Ore
Silver Ore
Lead-Zinc Ore
Gold Ore .
Gold ore
Silver Ore
Zinc Ore
Copper Ore
Copper ore
Silver Ore '
•-Opper Ore '
Copper ore
Gold Ore
Gold ore
Copper Ore
-opper ore
Copper ore
Gold Ore
Copper Ore •
Copper ore
Ililllllllllllllllll
3-32
September 1994
-------
EIA Guidelines for Mining Overview of Mining and Benefication
deposits. Combinations of the various types of hydrothennal systems in various host rocks create
variations in deposit morphology, grade ranges (variation in gold content), and wall rock alteration.
Deposit morphology ranges in a continuum from veins several feet thick and hundreds to thousands of
feet in vertical and lateral dimensions (formed by mineral precipitation in voids'hi the host rock) to
disseminated mineralization (essentially micro veinlets) pervading through the host rock in irregular
. pods up to several hundred feet in dimension.
Gold deposits may be categorized based on similarities in geologic environment and generic
hydrothennal factors. Recent data show that the 25 largest gold producing mines in the U.S. may be
grouped into four types: sediment-hosted disseminated gold (examples are the Goldstrike and Gold
Quarry mines), volcanic-hosted epithennal deposits (McLaughlin, Chimney Creek), porphyry copper-
related deposits (Bingham Canyon), and greenstone gold-quartz vein deposits (Homestake). (Bureau
of Mines, 1990c).
.Grades range in all deposit types from subeconomic margins to high-grade ores. The term "high
grade" varies with mining methods but usually refers to ores greater than 0.1 or 0.2 oz/t. Likewise,
average deposit grades are economic distinctions. Deposits requiring high-cost mining and milling
methods may require bulk averages of 0.25 oz/t or more, at 0.15 or higher cutoffe. Those deposits
that are. amenable to the lowest-cost mining and milling methods may average 0.03 to 0.04 oz/t or
less with an ore-to-waste separation grade of about 0.01 oz/t.
The mineral content or assemblage of a deposit is the result of reactions between hydrothennal
solutions and the wall rock, influenced by wall rock chemistry, solution chemistry, temperature, and
pressure. Most gold ores contain some amount of sulfur-bearing minerals; carbonate deposits may
also contain carbonaceous material. The weathering environment affecting the ore body following
deposition is determined mainly by the location of the water table (either present or past) in relation
to the deposit. Ores above the water table, hi the vadose or unsaturated zone, will tend to be
oxidized (referred to as "oxide ores"), while ores below the water table will usually be unoxidized
(referred to as "sulfide ores").
Gold ores may contain varying amounts of arsenic, antimony, mercury, thallium, sulfur, base metal
sulfides, other precious metals, and sulfosalts. The amount of these constituents depends on the
nature of the deposit and the amount of weathering that has occurred. Subsequent alteration of the
ore by oxidation influences both gold recovery and the byproducts of extracting the ore. Sulfide
minerals oxidize to form either oxides or sulfosalt minerals. Leaching of sulfides or other minerals
may occur in association with oxidation. Sulfide ores retain their original composition. Zones of
secondary enrichment may form at the oxidized/unoxidized interface.
3-33 September 1994
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•IIH
Overview of Mining and Benefidation
EIA Guidelines for Mining
IK in I in HI 11 ill in
The minerals found in gold ores, and elements associated with them, vary with the type of ore.
Sulfide ores contain varying amounts of native gold and silica (SiO^, as well as sulfur-bearing
minerals, including, but not limited to, sphalerite (ZnS), chalcopyrite (CuFeSj), cinnabar (HgS),
galena (PbS), pyrite (FejjS), sylvinate ([Au,Ag]Te2), realgar (AsS), arsenopyrite (FeAsS), ellisite
(TljAsSj), and other thallium-arsenic aniimony-mercury-bearing sulfides and sulfosalt minerals.
Oxide ores may contain varying amounts of these minerals, as well as silica (SiOj), limonite
(FeO-OH-nH2O), calcfte (CaCOa), clay minerals, and iron oxides (Hurlbut and Klein, 1977).
The mineral assemblage of the ore deposit is an important factor in the beneficiation method to be
used. In general, the percent recovery of gold from sulfide ores using various cyanidation techniques
III 11! 111111|| iiiijin i nil i n n i iiiini minimi in iiiiiini i nnnnnniiiiiiiiini nniiiiiiiiiiini i in mi iiiiiini mi n iiiini n n in i inn i n mi inn iiiini iiiiinn in i iiiiini mi in iiiini n i inn 111 n in n n inn i inn mi iiiiini iiiini in inn i iiiiini 111 in in i mi mi 11 in i in i nil 11 in iiiiini n in n 11 in i in in in i iiiiini in i in iiiiiiiiini in n i n i iiiini nniiiiiiiiiini inn n nil i n iiiiiini iiiini n i in n in nil in nuii t nnn :a \ta\\n~ i
is lower and more costly than from oxide ores. Recovery is reduced because the cyanide solution
also reacts with constituents such as sulfides in addition to gold. Increasingly, sulfide ores may be
oxidized in roasters or autoclaves. This is the result both of the development of more cost-effective
oxidation techniques and of the fact that oxide ores are •becoming increasingly scarce (Weiss, 1985).
3*3.1.2 Mining
Gold ore may be mined by either surface or underground techniques. Mining methods are selected
based, on maxfrmm^ ore recovery, efficiency, economy, and the character of the ore body (including
[[[ dig, size, shape,'and strength) (Whiteway, 1990). ........ With notableexceptions (e.gT, ..... the Homestake
mine), most gold ore in the United States is mined using surface mining techniques hi open-pit mines.
This is primarily because of economic factors related to mining large-volume, low-grade ores and the
[[[ improvement of cyanide leaching techniques. In 1988, a total of 160 million short torn of crude ore
(97.8 'percent of the total) was handled at surface lode mines. " In contrast,' 'underground mines mined
onlySGS ..... miiium ..... Short ..... tons ...... (25 ..... ...... ...... ..... ...... ----— ........ -- .......
oMmes, 199
i II i Illlllllll jitf I 111 1 1 |||||||||||||l|i|||||||i^
amounts of crude ore, waste, and marketable product generated by surface, underground, and placer
operations in 1988.
Exhibit 3-3, Materials Handled at
•'•' Mrterar -••''••'••»
Surface and Unc
lerground Gold Mines, 1988
''•<•'••."/•>-•. •-••''.•.-••^: ' •' •'• Lode-' •••'• •••: •<•' '
•*•• Surface v =
Underground
Total
Placer
Material handled (1,000 short tons):
Total
Crude Ore
Waste
Marketable Product
(1,000 Troy oz.)
553,000
160,000
394,000
5,250
4,890
3,560
1,340
241
558,000
163,560
395,000
5,490
32,900
15,000
17,900
153
Source: EPA, compiled from Bureau of Mines, 1990b.
-------
EIA Guidelines, for Milling Overview of Mining and Beneficiation
. The quantity and composition of waste rock generated at mines vary greatly by site. This material
can contain either oxides or sulfides (or, more likely, both), depending on the composition of the ore
body. Constituents include mercury, arsenic, bismuth, antimony, and thallium, and other heavy
metals. These may occur as oxides, carbonates, and sulfides with varying degrees of solubility.
Sulfur-bearing minerals, such as pyrite and pyrrhotite, can oxidize to form sulfuric acid (Bureau of
Mines, 1984). Factors that influence acid generation by sulfide wastes include the availability of
oxygen and water; the presence and availability of acid-generating and/or neutralizing minerals in the
• • \
rock; and the design of the disposal unit. Overburden and waste rock are generally disposed of in
unlined piles known as mine rock dumps or waste rock dumps (occasionally, they can be called "low-
grade ore" or "subore" stockpiles). Waste dumps are generally unsaturated. Waste rock also is used
in constructing tailings dams, roads, and for other onsite purposes. Waste rock with high sulfide
content and sufficient moisture content, and without adequate neutralization potential or other controls
in the dump itself (e.g., encapsulation or segregation of sulfide material within the dump), has led to
significant problems associated with acid drainage, both from waste rock dumps and from roads and
other onsite construction made of sulfide waste rock.
Mine water consists of water that collects in mine workings, both surface and underground, as a
result of inflow from rain or surface water, and groundwater seepage. Mine water may be used and
recycled in the beneficiation circuit, pumped to tailings impoundments, or discharged to surface water
under an NPDES permit. During the life of the mine, if necessary, water is pumped to keep the mine
dry and allow access to the ore body. This water may be pumped from sumps within the mine or
from interceptor wells surrounding the mine. Interceptor wells are used to withdraw groundwater and
create a cone of depression in the water table around the mine, thus reducing groundwater inflow.
Surface water is most often controlled using engineering techniques to prevent water from flowing
into the mine.
The quantity and chemical composition of mine water generated at mines vary by site. The chemistry
of mine water is dependent on the geochemistry of the ore body and surrounding area. After the
mine is closed and pumping stops, the potential exists for mines to fill with water. Water exposed to
sulfur-bearing minerals in an oxidizing environment, such as open pits or underground workings, may
acidify, and mobilize metals in the rock matrix. In contrast, flooding of some mine workings may, in
some unusual situations, serve to slow or stop acidification by reducing or eliminating the source of
oxygen.
In addition to wastes generated as part of gold mining and beneficiation, facilities also store and use a
variety of chemicals required by the mine and mill operations. Exhibit 3-4 presents a list of
chemicals used at gold mines, compiled from data collected by the National Institute for Occupational
Safety and Health (NIOSH, 1990).
3-25 September 1994
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Overview of Mining and Benefidation
EIA Guidelines for Mining
Exhibit 3-4. Chemicals Stored and Used at Gold Mines j
Acetic Acid
Acetous
Acetylene
Ammonia .
Argon
Asbestos
Butyl Acetate
Calcium Carbonate
Calcium Oxide '
Carbon Dioxide
Chlorine
Coal ,
Copper
Diatomaceous Earth '
Didikttodifluoromethane
Diisobutyl Ketone
Ethauol
Fluoride
Graphite
Hexone
Hydrogen Bromide
Hydrogen Chloride
Hydrogen Peroxide
Iron Oxide Fume
Kerosene
Lead
Lead Nitrate
Litharge
Mercuric Chloride
Mercury
Methyl Acetylene-
Propadiene Mixture
Methyl Alcohol
Methyl Chloroform
Mineral Oil
Molybdenum •
Nitric Acid
Nitrogen
Nitrous Oxide
Oxalic Acid
Phosphoric Acid
Portland Cement '
Potassium Cyanide
Propane
Pyridine
Sucrose
Silica, Sand
Silica, Crystalline
Silver
Silver Nitrate
Sodium Cyanide
Sodium Hydroxide
Stoddard Solvent
Sulfuric Acid
Tin
Vanadium Pentoxide
Xylene
2-Butanone
Diesel Fuel No. 1
Source: National Institute for Occupational Safety and Health, 1990.
1
1
1
1
Surface Mining '
iiiiiiiiiiiii! _ • , Ntvjt;EHK3Mi';ii4,it u is K*,a IE si, »*,i,i;iisii<:flw: ax SMtjHir.* • .• ' ii
Surface mining methods associated with the extraction of gold include open-pit and placer (including
dredging, which is often considered separately). Placer mining is used to mine and concentrate gold
from alluvial sand and gravels and is described hi Section 3.3.2.
Surface mining of gold is generally more economical than underground methods, especially in cases
wfaen_ to oretojjjr bong mnied is large and the degth of ovobmriencoye^'te deposit is limited.
Tne primary advantage of suSce inining is the ability to move large amounts'of material at a
relatively low cost, in con^arison.withunderground operations.
ii in •
I ................... | ..................................
IK ip 11|H ..... l|i||i ii ilillllll'ill illlllllllllllllllill . ..... . - ....... ;;U '.'-Upl
The predominant surface mining method used to extract gold ore is open-pit. Surface mining
practices follow a basic mining cycle of drilling, blasting, and mucking. The depth to which an ore
ftS ..... ...... ...... 22 ..... 22 ..... ..... SE ..... SSSlrfj^^ ....... nature ..... pfjfae ..... overburden, and
the stripping ratio. The stripping ratio is .the amount of overburden and waste rock that must be
removed for each unit of crude ore mined and varies with the mine site and the ore being mined
I II ° :
III ' I "I II i I I ' '
Stripping ratios can range up to 5 to 10 tons of overburden and waste rock per ton of ore or higher at
°Pen"Pit mines; it usually ranges around 1 to 3 tons per ton. These materials become wastes that
must be disposed of, primarily in waste rock dumps. Because ore grades in mined material are
° oncenn below the "cut-off grade (i.e., the 'grade at
: ....... inns is, often referred to as
££2ffi5H^B$ JHST ** stockpiled separately from other waste rock— this
- '
or «iovf_graijs ore
me
. C*?mB*Vfith ±e price of gold' tfn* -leading to more or less waste rock being disposed
~™" ....... •-' ....... iS"fhe stripping ratio changes.
September 1994
-------
EIA Guidelines for Mining Overview of Mining and Beneficiation
Underground Mining
Underground mining operations use various mining methods, including caving, stoping, and room and
pillar. In general, underground mining involves sinking a shaft or driving a drift near the ore body to
be mined and extending horizontal passages (levels) from the main shaft at various depths to the ore.
Mine development rock is removed, while sinking shafts, adits, drifts, and cross-cuts, to access and
exploit the ore body. From deep mines, broken ore (or muck) is removed from the mine either
through shaft conveyances or chutes and hoisted in skips (elevators). From shallow mines, ore may
be removed by train or conveyor belt. Waste rock, mine development rock, or mill tailings may be
returned to the mine to be used as fill for mined-out areas (EPA, Office of Water, 1982). The ratio
of waste rock to ore is much lower at underground mines than.at surface mines, reflecting the higher
cost of underground mining. Because of the higher costs, underground mining is most suitable for
relatively higher-grade ores. This in turn reduces the amount of beneficiation wastes (i.e., tailings)
generated (and disposed) per troy ounce of gold produced. .
. In Situ Mining
In situ leaching, although increasingly common hi the copper industry, is only an experimental
procedure in the gold industry and is not used in commercial operations. It involves blasting an
underground deposit in place to fracture the ore and make it permeable enough to leach.
Subsequently, 20 to 25 percent of the broken ore is removed from the mine to provide "swell" space
for leaching activities. In buried ore bodies, cyanide solution is then injected through a well into the
fractured ore zone. At surface ore bodies, the solution can simply be sprayed over the deposit.
Recovery wells are used to collect the gold-cyanide solution after it percolates through the ore.
Groundwater and surface water concerns are commonly raised in discussions of potential in situ
operations. In situ leaching has only been tested at the Ajax Mine near Victor, Colorado (Bureau of
Mines, 1984).
3.3.1.3 Beneficiation
Four main techniques are used to beneficiate gold ore: cyanidation, flotation, amalgamation, and
gravity concentration. Exhibit 3-5 illustrates the common methods used to beneficiate gold. The
method used at a given operation depends on the characteristics of the ore and economic
considerations (Bureau of Mines, 1984). Each of the four techniques is described below. Base-metal
flotation is described only briefly, since gold is produced only as a byproduct at these operations.
Amalgamation also is discussed only briefly, since this method is primarily of historic significance in
the United States. Gravity concentration methods are generally used only in placer-type operations
and are discussed in a separate section (Section 3.3.2). Cyanidation operations are by far the most
common, and are described in more detail below. The two basic types of cyanidation operations,
heap leaching and tank leaching, are described separately.
3.37 September 1994
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Mining and Benefidation
EIA Guidelines for Mining
Exhibit 3-5. Gold Mining and Benefication Overview
(Adapted from various sources)
(Open Pa or UndMtpound)
CutMntaPuto
Gold Adoption
Ekfton (stripping gold
warn aetivtiKj cuton)
i i u , i
-------
EIA Guidelines for Mining
Overview of Mining and Beneficiation
Exhibit 3-6 presents a comparison of gold ore treated and gold product produced by the various
beneficiation methods in 1991. As can be seen, cyanidation and direct processing (smelting of
precious metals recovered as a by-product from base metal mining) were used to produce 89 percent
and 10 percent of all domestic recovered lode gold, respectively. Placer mining accounted for 1
percent of the total gold produced. Amalgamation was used to beneficiate much less than 1 percent
of all lode gold in 1986, the last year for which complete data were reported (Bureau of Mines,
1990a). .
1
Exhibit 3-6. Gold Ore Treated and Gold Produced, By Beneficiation Method, 1991
, -- -- - ^ , - - '' -\ /sr -
Beneficiation Method
Cyanidation (All)
Heap Leaching
Tajik Leaching •
ATHJJI gatnsil iftn^
Smelting (ore and concentrates)^
Total Lode
Placer (gravity)
Gold Ore Treated
Percent
51
36
14
0.5
49
100
100
Source: Bureau of Mines, 1992.
Notes: .
Due to rounding and unit conversions, totals may not i
a Values for amalgamation axe for 1986 productio
was available.
b^tneltinff tif has£ metal nnss and ^mcmtrates m
information is not available specifically for flota
suggested that these production figures approxin
industry.
Short Tons
(OOOs)
227,271
159,985
67,285
0.9
221,507
. 449,920
5,500,000
cubic meters
Gold Produced
Percent
89
33
56
0.3
10
99
1 .
Troy •oZi-x'-;'« ;-
8,235,820
3,037,084
5,198,736
33,694
909,736
9,227,187
92,851
match exactly.
n, the last year for which complete information
ainly copper and lead ores. Production
tion, but Bureau of Mines personnel have
iate byproduct gold production by the base metal
By-Product Gold (Rotation)
As described above, flotation is a technique hi which particles of a single mineral or group of
minerals are made to adhere, by the addition of reagents, preferentially to air bubbles (EPA, Office of
Water, 1982). This technique is chiefly used on base metal ore that is finely disseminated and
generally contains extremely small quantities of gold hi association with the base metals. Gold is
recovered as a byproduct of the base metal recovery (for example, recovered from electrowinning
sludges or slimes).
3-39
September 1994
-------
of Miffing and Beneficiation .. EIA Guidelines for Mining
''255 ,g SSSsI and SSjSi py size m preparation for flotation. The ore is then slurried with chemical
2.52S 252 22E JSS^^^^S^^^ —S^F5' iactivat°rs, arid depressants. In a-
iJlSS*:*! S*^0,^,.!!?* °Hslu557 ?®*,*??i§Fms *** ™!?^ j£a conditional cell so the reagents coat the
?-Sr|p mtoenl. Thei;con£tion^ slurry is pumped to a flotation cell,, and air is injected. Air bubbles
SJO tie rg|en£s and carry the target mineral i to the surface, away from the remaining gangue,
?!55!!0,!!: Ifi Ife §2§S?°J! .tSSl!!!?116' ^ target mineral is not necessarily the precious metal or
SlES: Dependmg on the specific gravity and the reagents used, the values may be recovered
top or bottom of .the flotation cell.
~ i "" < i
In general, mere would be little or no incremental environmental concerns as a result of byproduct
"=*'* == A=; ±=55=rj^^ would be related to""the ^g"'^^ ^r^— —^
Wastes generated as a result of amalgamation activities consist of gangue in the form of coarse- and
fine-framed particles and a liquid mill water component in the form of a slurry. The constituents of
^ ^K ..... — ..... ^^£ ..... !°, ....... *25 ...... f0.^ ..... 2 ..... ,$£ ...... 25 ..... !Slv. ...... fi£ ..... £5X5!) Plus any mercury lost during
amalgamation. TMs ^^d can then be" i^^ed to. a tailings' impoundment, , In the past, some U.S.
operations (as well as current operations in other parts of the world) simply directed the tailings to
nearby streams or valleys. In some areas, the amount of mercury lost during historic mining has
amalgamation operations, metallic gold is wetted with mercury to form a solution of gold in
mercury, referred to as an amalgam. This method of beneficiation is most effective on loose or free
coarse gold particles with clean surfaces (EPA, 1982). Because of its high surface tension, mercury
does not penetrate into small crevices of ore particles, so the ore generally must be crushed finely
............ | [[[ ^lilSS05* *e*aM material. Use of mis.method of gold beneficiation has been greatly
|iP M, 'HRpSnn -ii« ..... « ........ Si iSSiSF?* past because of its high costs, inefficiency in large-scale
op"^00** and the scarcity of ores amenable only to this technique. In addition, environmental
concerns related to mercury contamination have contributed to its limited use. It is stili used in other
J P3"5 °f the world, particularly remote areas such as the upper Amazon, where its suitability for
small-scale operations and limited environmental concerns have not restricted its use.
i
I I 111 I III I I 111 111 I II Illl 111 II 111 II ll|lllllll illlH^^^^ Illlllilllllll 111 I III I I I III III III 111 I 111 Illl III I 111 111 I I III 111 I III II I 1111 111 111 I Illlllllllll 111 111 I Illl III I I 11111 III III II 111 I I ill 111 II II 1 1 111 II I I 111 III I I 111 III III 11 111 11 II
Ore preparation consists of grinding, washing, and/or floating the ore. The ore is then fed into a ball
mffl along with mercury to form an amalgam. The amalgam is then passed over a series of copper
plates where ifcollects. When fuUy loaded with amalgam, the plate is removed and the amalgam is
scraped off. Upon heating the hardened amalgam in a retort furnace, the mercury is vaporized and
thc S°Id material remains. The mercury driven off by heating is captured, condensed, and reused.
Alternatively, ..holdjutejiitnc acid may be applied to the amalgam, tlissolving the mercury and
lw*v% ....... —,i?—. ..... 25S?^ ............... ^E^IEE!!!0,?. ...... i!55 ....... SS^^SS? ..... .been ..... used ....... m conjunction with other
-------
EIA Guidelines for Mining Overview of Mining and Beneficfation
been significant, and has led to widespread mercury contamination. . For example, modem placer
operations in California have recovered substantial amounts of mercury from stream sediments
contaminated by past amalgamation operations.
Cyanidation •
As noted previously, the predominant methods used in the U.S. and the developed world to ~
beneficiate gold ore involve cyanidation. This technique uses solutions of sodium or potassium
cyanide as lixiviants (leaching agents) to recover precious metals (including gold and silver) from the
ore. Cyanide heap leaching is a relatively inexpensive method of recovering gold from lower-grade
ores while tank leaching is used for higher grade ore. Although other lixiviants are currently being
tested, none are known to be used in commercial operations. Alternative lixiviants include
malononitrile, bromine, urea, and copper-catalyzed thiosulfate (Bureau of Mines, 1985; Bureau of
Mines, undated(a)).
. .The cyanidation-carbbn adsorption processes most commonly used involve four steps: leaching,
loading, elution, and recovery (van Zyl et aL, 1988) (see Exhibit 3-7). In leaching, the cyanide
reacts with the ore to liberate gold material and form a cyanide-gold complex in an aqueous solution.
Precious metal values in this solution are men loaded onto activated carbon by adsorption. When the
loading is complete, the.values are eluted, or desorbed from the carbon, and recovered by
electrowinning or zinc precipitation prior to smelting. An alternative to cyanidation/carbon adsorption
is cyanidation/zinc precipitation. The cyanidation-zinc precipitation technique also involves four
steps: leaching, clarification, deaeration, and precipitation. The precipitate (a solid) is smelted
directly.
Cyanidation is best suited to fine-gram gold in disseminated deposits. Cyanidation techniques used in
the gold industry today include:
• Heap or valley fill leaching followed by carbon adsorption (carbon-in-column, or CIC,
adsorption)
• Carbon-in-pulp (CIP) operations, where the ore pulp is leached in an initial set of tanks
with carbon adsorption occurring in a second set of tanks
• Carbon-in-Leach (CIL) operations, where leaching and carbon recovery of the gold values
occur simultaneously in the same set of tanks
• Cyanide leaching in heaps or tanks (CIP) followed by zinc precipitation (the Merrill-Crowe
process).
3-41 September 1994
-------
' j I
1 I
Orerriew of Mining and Beneficiation
EIA Guidelines for Mining
ExfaibitS-7. Steps for Gold Recovery Using Carbon Adsorption
(Adapted from various sources)
LEApHfNQ
ORE
HEAP OR VALLEY
LEACHING
CRUSHING, GRINDING.
BENEFICATION.
CALCINATION
IH^^^^^^^
IIIIIIIIH^ ....... Ill 111:.
HlltM^^^^^^^^^^
3-42
September 1994
-------
EIA. Guidelines for Mining Overview of Mining and Beneficiation
As noted previously, in situ cyanide leaching to recover gold directly from ore bodies is a subject of
research by the Bureau, of Mines and others, but is not used commercially at this time. Other
methods to recover the precious metal from the cyanide solution following leaching include solvent
extraction and direct electrowinning; these methods are not common in the industry and are not
discussed here.
Heap or valley fill leaching is generally used to beneficiate ores containing an average of less than
0.04 troy ounces- of gold per ton of ore. QP and QL techniques, commonly referred to as tank or
vat methods, are generally used to beneficiate ores averaging more than 0.04 oz/t. Gold beneficiation
cut-off values are dependent on many factors, including .the price of gold and an operation's ability to
recover the precious metal (van Zyl et ah, 1988). At many heap leach operations, the lower cut-off
grade is around 0.01 to 0.02 oz/t.
The sections below describe gold beneficiation using the various cyanidation techniques. The first
subsection describes ore preparation that may take place before cyanidation. This is followed by
sections that describe heap leaching and tank leaching, respectively, with carbon adsorption and zinc
precipitation discussed in the heap leaching section. In each section, the discussion focusses on the
operations, the waste generated, and the major environmental concerns during and after operations.
Ore Preparation
Depending on the type of ore (sulfide or oxide), the gold concentration in the ore, and other factors,
the mine operator may prepare the ore by crushing, grinding, and/or oxidation (roasting, autoclaving,
or bio-oxidation) prior to cyanidation or flotation. Crushing and grinding are described briefly.
below, as is oxidation.
Crushing and Grinding. In most cases, ore is prepared for leaching or flotation by crushing and/or
grinding. These operations produce relatively uniformly sized particles by crushing, grinding, and
wet or dry classification. Factors that determine the degree of ore preparation include the gold
concentration and the mineralogy and hardness of the ore, the mill's capacity, the next planned step in
beneficiation, and general facility economics. Run-of-mine ores with very low gold concentrations
may be sent directly for heap leaching with no prior crushing or classification.
Milling begins when ore material from the mine is reduced in particle size by crushing and/or
grinding. A primary crusher, such as a jaw type, is used to reduce ore into particles less than ISO
millimeters (= 6 inches) in diameter. Generally, crushing continues using a cone crusher and an
internal sizing screen until the ore is less than 19 mm (= 3/4 inch). Crushing in jaw and cone
crushers is a dry process, with water spray applied only to control dust.
3-43 September 1994
-------
lull ill1 illl'illlllH ililill 111 1111 III Illillllllllillllllll
Orerriew of Mining and Benefitiation
EIA Guidelines for Mining
From die cone crusher, ore to be leached in tanks is fed to the grinding circuit where milling
continues in the presence of water, often with cyanide added to begin the ieadung~process (ore to be
' ....... "n .......... " ': ...... "u .......... "" " leached in heaps or valley fills ....... is x&^m'ihe^^ ............... — — . ......
form a slurry containing 35 to 50 percent solids. Grinding then occurs hi ball or rod rniis to further
reduce the ore particle size. In some cases, ore and water are fed directly into an autogenous mill
(where the hard ore itself serves the grinding medium) or a semiautogenous mill (where the ore
• supplemented by large steel balls are the grinding media). Between each grinding unit operation, .
[[[ hydrocyclones ...... are used to classify coarse and. fine particles, with coarse particles returned to the
circuit for further size reduction and fine particles continuing through the process. Milled ore is in
the form of a slurry, which is pumped to the next unit operation (Weiss, 1985; Stanford, 1987).
Fugitive dust generated during crushing and grinding activities is usually controlled by water sprays,
although there may be other ah* pollution control devices whose blowdown streams may be .
[[[ recirculated into the beneficiation circuit.
QxidationjofjSulfides (Roasting. Autoclaving. and Bio-Oxidation). Beneficiation of sulfide ores may
• include oxidation of sulfide minerals and carbonaceous material by roasting, autoclaving, bio- •
HSSS'jS oxidation, ....... or ..... chlorfnatipn ..... (chlorination is not commonly used because of the high equipment •
[[[ I ................ maintenance costs caused by the corrosive nature ..... of the oxidizing agent). Roasting ...... involves ....... heating
sulfide ores in ah* to convert them to oxide ores amenable to cyanidation. In effect, roasting oxidizes
the sulfur in the ore, generating sulfur dioxide that can be captured and converted into sulfuric acid.
Roasting temperatures depend on the mineralogy of the ore, but range as high as several hundred
•'S,™i ™i degrees ....... Cdsjus. .............. Roasting ..... of ores ...... that ...... contain ..... carbonaceoj^ material ....... oxidizes ....... the ...... carbon ..... that
otherwise interferes with leaching and reduces gold 'recovery efficiency. Autoclaving (pressure
oxidation) ....... is ...... a relatively ...... new ...... technique that ogerates at lower ternperatures than roasting.
............. , .............. , ....... ,,, ..... „ ............... ............ '_, ...... , .................. Autoclaving uses pressurized steam to start the reaction and oxygen to oxidize sulfur-bearing •
minerals. ............... Heat ..... released ..... from ..... the ..... oxidation .of sulfur then sustains the reaction. Roasting and
..... !El9lll!!lllll!llllll!!l!!l!!1ll!;1!ll!!!!!lllllll!ll?f ....... !ir ...... ilElllKllBlltlinillllllElllllilinilTirlllii'll'l ......... 'Till1!!!!!!!!1!:!"!!! ...... !l!!l!!llilllllll!l!!!!lill!!!1l||ll>vll!:i!!!!!!!!!l!!l!tl!l ..... III! ....... I'!"!!'!"! ......... llffllliinil'S'llKSISIIIIfJ!] ..... !JI|l1i;ll!!!!!l!l!l!l!!!!l' !I!9"!II!I!I"?SS'I ,r .................... ......... ...........
are being used ..... morej^entl in the USasibe technologic become more cost- •
• ......
bacteria to oxidize the sulfar-bearing minerals. 'This technique
is currently used on an experimental basis at the Congress Gold Property in fanaria and at the
Homcstake ....... Tonkin ....... Springs property in Nevada. The bacteria used in this technique are naturally
Illlllllllllllli lil!!!1l1J|il3|||j||||||ii|'i|||l||l:!||||l||||||F Ill^ ...... ''" ....... '"' ....... :l'"' ..... lll!l!'' ............ i!1'!11!!!':*111!!!1111!1*!!1!1111!!!1!!!1"'!'!! ...... i!1"!1 ''!' 1 ..... iii"ft!il*i|i«|||!|i!!!ii'l»iii| ........ '!iliii|n|i|»!i!iii|i| ..... iipi'iiniillii'.iiiiiiiiiiiniH'ii ...... |iii:!«||||||i«||||||i|iil!! ...... ip ..... IliplwiPPI^lllliiniiiiii''!'!'!!!''!!!^!!!!!'!!!;.!!!''!!!!!! .............. run .............. I'll ..... I!1!"1! ............. **i •'!'"'" •• r -:!
ically include Tfuobatillusferroaxidans, Thiobadllus thiooxidans, and
i^.^i,..^?!1^16' me bacteria are placed hi a vat with sulfide gold ore.
ga ...... the:iiisulfide ...... rmnerals ..... and ..... fenpjis ..... iron components of the gold ore^ Research is
conducted on'other bacteria that can grow at higher temperatures; high-temperature
y-r-.are .thought to trcat me ore ^ a ma<^ fester 5ffe OBureau of Mines, 1990^. Although more
: "• 11;: time,is reqi!red_ for bio-oxidatign, it is considered, ig.bejejs,expensive than roasting or autoclaving
;,«^^^^ ..... ma
^^^^^
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ESA Guidelines for Mining Overview of Mining -and Beneficiation
Heap Leaching
Since the late 1970s,- heap leaching has developed into an cost-effective way to beneficiate a variety of
low-grade, oxidized gold ores. Compared to conventional cyanidation (i.e., tank agitation leaching),
heap leaching has several advantages, including simplicity of design, lower capital and operating
costs, and shorter startup times. Depending on the local topography, a heap or a valley fill method *
may be employed. Where level ground exists, a heap is constructed;.the heap consists simply of a
flat-topped pile of the ore to be leached. In rough terrain, a valley may be dammed and filled with
the ore. Sizes of. heaps and valley fills can range from a few acres up to several hundred. The
design of these leaching facilities and then- method of operation are quite site-specific and may vary
over time at the same site. Gold recovery rates for heap and valley fill leaching generally range from
60 to 80 percent, but may be higher in some cases.
Leaching. Heap leaching activities may involve any or all of the following steps (Bureau of Mines,
1978 and 1984; van Zyl, 1988; many others):
• Preparation of a "pad" (or base under the heap) with an impervious liner on a 1 ° to 6°
slope or greater for drainage. No gold heap or valley fill leaches are known to operate
without a liner (Hackel, 1990). Some liners may simply be compacted soils and clays,
while others may be of more sophisticated design, incorporating clay liners, french drains,
• and multiple synthetic liners.
• Placement of historic tailings or other relatively uniform and pervious material on the liner
to protect it from damage by heavy equipment or other circumstances;
• Mining ore (or, as has been practiced in Cripple Creek, Colorado, and elsewhere, taking
material containing .gold values from old waste piles or coarse tailings).
• Crushing and/or agglomerating the ore (agglomeration is discussed below), typically to
between 1/2 and 1 inch in size if necessary and cost-effective; some operations may leach
run-of-mine ore.
• Placing the ore on the pad(s) using trucks, bulldozers, conveyors, or other equipment.
• Applying cyanide solution using drip, spray, or pond irrigation systems, with application
rates generally between 0.5 and 1.0 pounds of sodium cyanide per ton of solution. This is
known as the "barren" solution because it contains little or no gold.
• Collecting the solution intercepted by the impervious liner via piping laid on the liner,
ditches on the perimeter of the heap, or pipes/wells through the heap into sumps at the liner
surface. The recovered solution, now "pregnant" with gold (and silver), may be stored hi
"pregnant" ponds or routed directly to tanks for gold recovery, or it may be re-applied to
the heap for additional leaching.
Recovering the gold from the pregnant solution.
3-45 September 1994
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Overview of Mining and Benefication
EIA Guidelines for Mining
I
Two common types of pads are used hi gold
heap leaching: permanent heap construction on
a pad where ore is placed, leached, and left in
place; and aictoiFiiacisi —— — ^ ^g^ Qn
' flic pad, fc^lsi, ,SJ, ,22121 £, m Vcn$?:?snt
disposal site, after which more ore is placed on
,1 ^ j tmw^m the pad for a new cycle. Permanent heaps are
built in successive lifts, with
, I i
' Agglomeration. Ores with a high proportion of
:;•' small particle size (mhms 200 mesh) require
additional preparation before leaching can be done
effectively. Because percolation of the Uxiviant
through the heap may be retarded as a: result of
preventing the solution from contacting and
recovering the gold from sections of the heap),
11 lil"""" v
composed of a 5- to 30-foot layer of ore. Each
lift is men leached, a new lift is added to the •
IP i
top and leached, and so on, until the heap
reaches its final height, which can range up to
200 feet or more,, On-off pads are much less
common in the industry (Lopes and Johnston,
1988).' •
: /increase particle size.. Agglomeration aggregates
individual particles iito a larger mass, thus
. • ;• enhancing percolation of the lixiviant and -
ffs extraction efficiency: This technique may ' <
; ^increase the flow of cyanide solution through the
:heapby:a^factor:of 6,000, decreasing the overall
• leaching time needed.: Agglomeration is currently
,. used in about half of all heap leaching operations,
: -The agglomeration technique typically involves "
" the following (Bureau of Mines, 1986).%
marerfals vary withme'iype of pad, site
conditions, and perhaps most importantly,
regulatory requirements. Construction materials
•llllll I I 111 111 111 llllllllilH llllll lllllllllini I IIII , ;
may include compacted soil, or clay, asphaltic
concrete, and low-permeability synthetic
membranes such as plastic or geomembrane
lllliillllll Illlilllllllllllllllli 11 lliill lllllijllliillllll I i n i
„ (van Zyl et al., 1988). As noted above, sand,
•M I llllll l|ll III 11 in in n in i iiiiiiiini i iiiini iiinnilliwili i in iiiinnni inn iininininn inn niinnnn inn inn 11 n inn muni mi ninnm i
historic tailings, or crushed ore may be placed
• on top of the synthetic liner to provide a •
pervious medium for leachate collection as well
as to protect the pad. Older pads tend to be
', with little or no other
made of compacted
site SSSSSSh ............... JJfZ? P3^ are
' *. " -
fltlf ^i
•• Adding Portland cement (a binding agent)
and/or Bme (for alkalinity) to the crushed ore
as or before It is placed on the heap
Wetting the ore with cyanide solution to start :,;
leachhig as or before the ore is placed on the ..,;::
heap (e.g., spraying cyanide solution over
ore on the conveyor that transports ore from •
the crusher to the heap) ^.'
• Mechanically tumbling die ore niLuure so
fine partides adhere to the larger particles.
This can occur, for example, when ore is
damped from the end of a conveyor or truck
:,. and then mechanically spread on the heap.
IS5E ...... ojPna^ye soil or imported clay.
» ...... .typically installed over a
Some mines now use synthetic liners composed of
are
...... 001^05^ liners; dependmg
s, there may be a leachate collection system between the liners to
detec^ and coUect any leakage through the primary liner. On-off pads are generally constructed of
asphaltic concrete to protect the liner from potential damage by heavy machinery used during
unloading.
Illllllllllllli llllll llllll 1(1,111
ill
n i iiiiii nil
i i
iiiiiiiiiiini in i "i in nil
I iii1 it i ill
3-46
September 1994
-------
EIA Guidelines for Mining Overview of Mining and Beneficiation
As notecj above, a variation of heap leaching is valley fill leaching. This method is used at facilities
with, little or no flat land and. utilizes liner systems similar to those used hi heap leaches for solution
containment. In valley fill leaching, the ore material is placed on top of a liner system located behind
a dam on the valley floor. As in heap leaching, the ore is treated with lixiviant but is contained and
collected internally at the lowest point hi the ore on the liner system for further beneficiation, rather
than hi an external solution collection pond. Montana, Utah, and other States have approved valley
fill operations.
In either of these two configurations, cyanide complexes with gold and other metals as the barren
solution percolates through the ore. Leaching typically takes from weeks to several months,
depending on the permeability and size of the pile. An "average/normal" leach cycle takes
approximately three months (Lopes and Johnston, 1988).
The reaction of the solution with the free gold is oxygen-dependent. Therefore, the solution is
oxygenated prior to application or during spraying. Barren solution may be kept hi a barren pond
prior to application, or may be routed directly to the heap from tanks. Barren solution is made up by
adding fresh water, cyanide, and lime to recycled water from the carbon columns (see below).
, * „•
After being applied to the surface of the ore by sprays or drip irrigation, the cyanide solution
percolates through the ore and is collected by pipes placed on the liner beneath the pile, drams
directly to ditches or ponds around the pile, or is recovered from sumps constructed at the liner
surface (Bureau of Mines, 1986; Lopes and Johnston, 1988). The solution is then collected hi a pond
or tank. The pregnant solution pond may be used as a holding pond, a surge pond, or a settling basin
to remove solids contained hi the cyanide solution. Some operations use a series of ponds, which
may include one for the barren solution, an intermediate solution pond (from which semi-pregnant
solution is directed back to the heap for further leaching before gold is recovered), a pregnant
solution pond, and one or more emergency overflow ponds. .
These ponds may be single-lined but are now more often double-lined with plastic (HDPE),
butylrubber, and/or bentonite clay to prevent seepage. Composite liners, often with leachate
collection systems to detect leaks are becoming increasingly common hi response to more stringent
States requirements. Particularly hi the arid west, but also hi the east (e.g., South Carolina) wildlife
and waterfowl may be attracted to the ponds, and the cyanide solutions present an acute hazard. To
control wildlife access to cyanide solution, at least one operation (Castle Mountain hi California) has
elected to construct tanks to collect and store leachate solutions as an alternative to open ponds.
Many active operations now fence or cover solution ponds with screening or netting to prevent
wildlife or waterfowl access, respectively.
3_47 September 1994
-------
pyerriew of Mining and Benefication EIA Guidelines for Mining
I ' I : • ~ : • '• ' """" " "
Leaching occurs according to the foUowing-reactions, with most of the gold dissolving in the second
reaction (van Zyl et aL, 1988):
* 4Au + SNaCN + Qz + 2H20 -» 4NaAu(CN)2 + 4NaOH (Elsener's Equation and
• ' • : Adamson's 1st Eolation)
1™=S ..... IsSsiP®* ...... ± ....... ft + 2H20 - 2NaAu(CN)2 + H2O2 + 2NaOH (Adamson's 2nd
iiiiiH aiiilii "
llri 111 Nil I lllllli III Hi 111111' Ill I lilill liiliill II il I illiili In Ilillll lililliill il I lull Ill II 111
, i , - : * being approximately 10.5.
SSlS ffiSSiSS ffiay result in the loss of .cyanide through hydrolysis, reaction with carbon
Bj^K spill 2£ Sc^S§,,,liydrogen to form hydrogen cyanide (HCN). Alternatively, more basic '
", coidpons tend to slow the reaction process (Bureau of Mines, 1984) Typically, the recovered
cyanide solution contains between 1 and 3 ppm of gold material (Bureau of Mines, 1986). Leaching
continues until me gold concentration in pregnant solution fells below about 0.005 ounces per ton of
S^EE^SS 25 Ife!0!^ !?㤤>! SlS &* OMUK at permanent heaps, another lift is added and
" | "leached or tfaehejip is prepared for closure. ' : :
Barren solution must be treated to reduce cyanide levels to regulatory levels— cyanide species
regulated can be weak-add^isso^ ....... gee, ....... or total ...... cyanide-when recycling is no longer necessary.
Treatment occurs when contaminants ....... build ..... up ..... in ..... the ...... recycung^c^dej.solution, at the .end, of leaching.
seasons, and/or at facility closure. Defending on regulatory '~Teqtirmaa, the wAitian^r'aeii be
land applied, stored in ponds, or evaporated.
" .................................... : ..................... [ [[[ v": ...... : ........................... ;||; [[[ l ......... ' ............ \ ................ '
Whenleaching ends, me spent ore that makes up the heap usually remains in place. Whereon-off
however, spent ore will have been successively removed from the pad for disposal in
*** « fi^SE » 5» .SHiM .tpm, g&off. pads), the
— ..... __ ...... - ...... ,_ ......
I. This is.. _ ^ ^ _r o
wat^TIstlally ^ WJtter OT aSSL «***»*«• Hydrogen peroxide or other oxidants may be added to
J*^6 f31618- Cyanide in rinse water may be treated using one or more of the methods described
5iL,i,»M,2 222 SEE ISS^???, E,,???!*1^ ,*la™^,,,,c51ceittrations, m rinse water/leachate to •
•fe heap can be reclaimed and/or abandoned. The
; i ejMnnousl|; variable,, ranging from a few days for some on-off
..... ......
i ...... i ........ i» ................ •» .......... » ............ ............. heaps to months or ears for some
.
i1 Hill Ilii ili iiillll liiliill1 111 ill i "
Se*pd.fflrt completeness of detoxification, spent ore may continue to have a high
pH. Heaps with agglomerated ores may prove particularly difficult to detoxify, since this tends to
keep pH high. Reclaimed piles may have passive controls to control run-on and runoff; the design
-------
EIA Guidelines for Mining Overview of Mining and Benefidation
or the probable iroxmmTn precipitation event, depending on the component and State regulatory
requirements.
3.
If sulfide ores are present, they may generate acidic leachate over time, which in turn may mobilize
heavy metals that are present in the ore. Although heap leach piles are generally lined, liners may be
damaged or may deteriorate, or may be intentionally punctured as part of reclamation.
Current technology and environmental concerns have led to the development of several methods for
complexing or decomposing cyanide. These include:
• Lagooning or natural degradation through photodecpmposition, acidification by CO2 and
subsequent volatilization, oxidation by oxygen, dilution, adsorption on solids, biological
action, precipitation with metals, and leakage into underlying porous sediments.
• Oxidation by various oxidants:
Chlorine gas
Sodium and calcium hypochlorites
- Electro-oxidation and electrochlorination
-' Ozone ^
- Hydrogen peroxide :•
. - . Sulfur dioxide and air.
In all cases, cyanide is oxidized initially to the cyanate, CNO . In some cases the cyanate
ion is oxidized further to NH<+ and HCO3-, and finally the ammonium ion may be
oxidized to nitrogen gas. •
• .Acidification, with volatilisation and possibly subsequent adsorption of HCN for reuse.
; • Adsorption of cyanide complexes on ion exchange resins or activated carbon.
• Ion and precipitation flotation through cyanide complexation with base metals and recovery
with special collectors.
• Conversion of cyanide to less toxic thiocyanate (CNS") or ferrocyanide (FeCCN)^4".
• Removal of ferrocyanide by oxidation or precipitation with heavy metals.
• Biological oxidation.
Hydrogen peroxide, for example, can be used to detoxify cyanide in spent heaps, tailings, and
solution ponds and tanks. The cyanide-bearing solution is sent to a series of hydrogen peroxide .
reaction tanks (Ahsan et al., 1989). Hydrogen peroxide and lime are added to the solution forming
precipitate of metal hydroxides and oxidizing free and weakly complexed cyanide into cyanate
(OCN-). Additional steps precipitate copper ferrocyanide, a reddish-brown solid that is stable at a pH
3.49 September 1994
-------
i: : 1! -: ; ; ; ,: ! ; : ; j ; : : : : ± _: ;,: ;
!
' " '' ' 1 ' ' ' •
Overview of Mining arid Beneficiation ; OTA. Guidelines for Mining
of less than 9. Precipitates are separated from the solution and discharged to the tailings
impoundment. The solution is then recycled until the desired cyam'de concentration is attained in the
effluent. , '
INCO has also developed a technique for detoxification of mine waste streams containing cyanide—
such as CIP and QL pulps, barren solution, tailings pond waters, and heap leach rinse solutions—by
removing cyanide and base metal complexes. The INCO process uses SO2 and air; which is
dispersed in the effluent using a well-agitated vessel. Acid produced in the oxidation reaction is
neutralized with lime at a controlled pH of between 8 and 10. The reaction requires soluble copper,
which can be provided in the form of copper sulfate (Devuyst et al., 1990).
" V ' ' , i (i if mi if in in111! i in I Hi"!"! 11 "i i ill I miii 11 11 ill i nil"!1 nidi in
Each treatment method may generate a different waste, with the chemical compounds used in cyanide
removal as constituents. Someof these (e.g., chlorine, ozone, hydrogen peroxide) are toxic to
bacteria and other life forms but' are unlikely to persist or can be cleaned' up easily. Others (e.g.,
chloramine or chlorinated organic compounds) may persist for long periods in the natural
environment. In general, the long-term persistence of cyanide residues in mining waste are not
completely understood (University of California at Berkeley, 1988).
I III I III ill III I III III III
Following detoxification, heaps may be regraded to more stable long-term configurations. Liners
may be punctured and the heap covered with topsoil and reclaimed/revegetated. In some cases, heaps
may require capping to reduce leaching of heavy metals. Reclamation requirements vary among the
States, and the types of reclamation that are suitable for a given heap generally depend on the nature
of the site and of "the spent.ore. Any:ponds are usually backfilled. Pond'"linere 'rnayjtejemoved,
folded over and sealed to encapsulate sludges or other wastes, punctured, or otherwise handled,
i depending on State requirements. Because of the enormous amounts of spent ore hi heaps/valleys and
•in spent ore dumps, any long-term environmental problems must be anticipated during design, since it
is not practical to move tijejnaterials after'. (operations """~ "
, 1 1 III 111 I "I ill Illllllllll III! Illllllllllllll Illllll , ..... llllllllliil ....... }
-------
EIA Guidelines for Mining Overview of Mining and Benefication
Activated carbon techniques are better able to process solutions with low metal concentrations and are
thus most often used on solutions with a gold concentration below 0.05 oz/t of solution (Bureau of
Mines, 1978 and 1984). Carbon adsorption is used both for heap leach solution and for tank
leaching.
In heap leaching, carbon adsorption uses the Carbon-in-Column (CIQ technique. In the CIC
technique, the pregnant solution collected from the leach pile is pumped from a collection pond or
tank into a series'of cascading columns containing activated carbon. The solution mixes with the
carbon column in one of two methods: fixed-bed or fluid-bed.
The fluid-bed method involves pumping pregnant solution upward through the column at a rate
sufficient to maintain the carbon bed in a fluid state moving gradually down through the column
without allowing the carbon to be carried out of the system. Thus, loaded carbon can be removed
from the bottom of the tank and fresh carbon added at the top. The fluid-bed method is the more
common of the two methods used in operations adsorbing gold-cyanide values from unclarified leach
solutions containing minor amounts of slimes. Because the fluid-bed method uses a countercurrent
operating principal, it is often more efficient and economical than the fixed-bed method in adsorbing
the gold-cyanide complex from solution (Bureau of Mines, 1978 and 1984).
In the fixed-bed method, the gold-laden cyanide solution is pumped downward through a series of
columns. The columns generally have either flat or dished heads and contain a charcoal retention
screen as well as a support grid on the bottom. Normally, the height-to-diameter ratio of the tanks is
2:1, although, in some instances, a larger ratio will increase the adsorption capacity of the system
(Weiss, 1985). In each vessel, the gold-cyanide complex is adsorbed onto activated carbon granules
that preferentially adsorb the gold-cyanide complex from the remaining solution as the material flows
from one column to the next. The advantage of the fixed-bed method over the fluid-bed method is
that it requires less carbon to process the same amount of solution (Bureau of Mines, 1978 and 1984).
*
Elution. Typically, the activated carbon collects gold from the cyanide leachate until it contains
between 100 and 400 ounces of gold per ton of carbon depending on the individual operation.
Loading efficiency decreases with solutions containing less gold (Bureau of Mines, 1978). The
precious metals are then stripped from the carbon by elution. The values can be desorbed from the
carbon using a boiling caustic cyanide stripping solution (1.0 percent NaOH and 0.1 percent NaCN).
Modifications of this method include the addition of alcohol to the stripping solution and/or stripping
under elevated pressure or temperature (40°C to 150°Q (Bureau of Mines, 1986). At least one
mine, Barneys Canyon, uses a stripping solution of hot sodium hydroxide that has proven to be as
effective as caustic cyanide (LeHoux and Holden, 1990).
3-51 .September 1594
-------
IIIIIIIIIIIIIIIII llllllllllllllllllllllll 1 III II Illllll 1111 Illllll 111 Pl|l|lllllll|llll I IIIIIIIIIIIIIIIII 111 111 111 111 Illllll III IIIIIIIIIIIIIIIII 111 l|lllllll Illllll Illllll IIIIIIIIIIIIIIIII Illllllllllllllllllllll Illllll lll|l IIIIIIII III Illlllllllllllllllllllllllllllllll •••llllllllll IIIIIIII I Illllll IllllllllIIIBIH I IIIIIIIIIIIIIIIII IIIIIIIIIIIIIIIII
iiiiiiini i1 iiiiiiii
Overview of Mining and Benefication EIA Guidelines for Mining
i i * i i
• i
Carbon uses! in adsoiption/desorption can be reactivated numerous times. The regeneration technique
varies with rnj^ng'operations, but generally involves an acid wash before or after elution of the gold-
cyanide complex, followed by reactivation in a kiln and re-introduction into the adsorption circuit
(Bureau of Mines, 1985). Generally, activated carbon is washed with a dilute acid solution (pH of 1
or 2) to dissolve carbonate impurities and metal-cyanide complexes that adhere to the carbon along
I, ' ' . . " • i ' ,., , , i' ' "
witjh the gold. This technique may be employed either immediately before or after the gold-cyanide
complex is removed. Acid washing before the gold is removed enhances gold recovery. Based on
I ' I, ' i ,»in* i • ',"•: "•' ' ,"• ' , •'„ '-' ' ' ' , •'; • , ! " ' ''i , „" , i; ' FT: s"";"" * " • •
impurities to be removed, from the carbon and metallurgical considerations, different acids and
concentrations of those acids may be used. Usually, a hydrochloric acid solution is circulated through
3.6 metric tons (4 short tons) of carbon for approximately 16 to 20 hours. Nitric acid is also used in
these types of operations, but is thought to be less efficient than hydrochloric acid (HCL) in removing
impurities. The resulting spent acid wash solutions may be neutralized with a high-pH tailings slurry,
dilute sodium hydroxide (NaOH) solution, or water rinse. When the wash solution reaches a stable
pH of 10, it is typically sent to a tailings impoundment. Metallic elements may also be precipitated
with sodium sulfide (Smolik et al., 1984; Zaburunov, 1989).
. 11 ii i in pij^^^ I1*" i i i • i i MI i i i i 'i
• i i
The carbon is men screened to remove fines and thermally reactivated in a rotary kiln at about 730°C
. for 20 minutes (Smolik et al., 1984). The reactivated carbon is subsequently rescreened and
xenttrodoced into the recfiyejy system. Recirculating the carbon material gradually'decreases
performance in subsequent adsorption and reactivation series. Carbon adsorption efficiency is closely
monitored and fresh i carbon is added ^maintain efficiency at design levels (Bureau of Mines, 1984
" and 1986)1 :
iiiiiiiiiiiiiiiii iiiiiiiiiiiii _ iiiiiiiiiiiiiiiii i- . " *
f01 °f optnnum size are either lost to the tailings shiny or, to the greatest extent
'"""""SS?^00* C?rbon lost to me circuit fc rep130641 with virgin, optimum-
from I!? ,rjeactiyatipn,,,,,cjrcu|!s .may include carbon fines and the acid wash
solution. The carbon may contain small amounts of residual base metals and cyanide. The acid wash
residues may contain metals, cyanide, and the acid (typically hydrochloric or nitric); according to
Newmont Gold Company, the acid is usually neutralized in a totally enclosed system prior to release.
Up to 10 percent of the carbon may be lost in any given carbon recovery/reactivation circuit from
abrasion, ashing, or incidental losses. Most operations capture less-than-optimum-size carbon
* particles and extract additional gold values (or send fines offsite for gold recovery). Onsite or offsite,
this may involve either incinerating the carbon/gold that could not be desorbed chemically durine the
. ' —-— JJ2J WJJ •»»»•»»»* J»w»» MMUUMUIJ UlUUlg Ulb
gSSSSSMii.SP^ti0118 or subjecting the material to an extended period of concentrated cyanide
T — r1-*1 - - - : - : ' - J
SIS Squids 255?,!? *****OT transport carbon material are recirculated.
;;^SflJdLBssai3!!SD[. Gold hi the pregnant eluate solution may be electrowon or zinc precipitated.
1 uses stainless or mild steel wool, or copper, as a cathode to
!!=^^^^^ US goW product. After two or more cycles of electrodeposition, the steel wool must be
SIlnfH /'iill^ lllllir'''!IWWH«WB!llfll 'ii'i' 1 ' "I'l ' iiiiiiii liiiiiiiii'i'iii' Jiii! lfi" lftiMBIi 'iii'iii'i BKDOHJIWiliTl iii'iiiiliiiiiiiii'ii'iiiiii i iiiii ""ii "ii iiiiiiiiiiiiiiiii mmi" i iiiiiiii
iii/'iiii ii W n ^ i i '.I'" •" i1"!1 r i • 3-52 . ' ' September 1994
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EIA Guidelines for Mining Overview of Mining and Benefication
removed and replaced. The depleted stripping solution may then be reheated and recycled to the
carbon stripping system. The steel wool or electrowhming sludge, laden with gold value, is fluxed
with sodium nitrate, fluorspar, silica, and/or sodium carbonate and melted in a crucible furnace for
casting into bullion. For gold ores containing mercury, a retort step is required before gold smelting
to recover metallic mercury (Bureau of Mines, 1986; Smolik et al., 1984).
Although carbon adsorption is the most common method of gold recovery in the United States, zinc
precipitation is the most widely used method for gold ore containing large amounts of silver. Because
of its simple and efficient operation, die Merrill-Crowe process is used at the 10 largest gold
producing mines in the world, all of which are in South Africa. This technique is well suited to new
mines where the ore has a high silver to gold ratio (from 5:1 to 20:1) (van Zyl et al., 1988).
In zinc precipitation operations (the Merrill-Crowe process), pregnant solution (or the pregnant eluate
stripped from the activated carbon) is filtered using clarifying filters coated with diatomaceous earth
to aid in the removal of suspended particles (see Figure 8) (Weiss, 1985). Dissolved oxygen is then
removed from the solution using vacuum tanks and pumps. This is necessary because the presence of
oxygen in the solution inhibits recovery (Bureau of Mines, 1984).
Metallic zinc dust then is combined with the deoxygenated pregnant solution. At some operations, a
small amount of cyanide solution and lead nitrate or lead acetate is added. Lead increases galvanic
activity and makes the reaction proceed at a faster rate. Zinc precipitation proceeds according to the
reaction described below; the result is a gold precipitate (Bureau of Mines, 1984).
NaAu(CN)z + 2NaCN +Zn +H2O - NajZ^CN^ + Au + H + NaOH.
The solution is forced through a filter that removes the gold metal product along with any other
precipitates. Several types of filters may be used, including submerged bag, radial vacuum leaf, or
plate-and-frame. The gold precipitate recovered by filtration is often of sufficiently high quality (45
to 85 percent gold) that it can be dried and smelted in a furnace to make dor6 (unrefined metals). In
cases where further treatment is necessary, the precipitate may be muffle roasted or acid treated and
calcined with borax and silica before smelting (Weiss, 1985). Following filtration, the barren
solution can be chemically treated (neutralized) or regenerated and returned to the leach circuit
(Weiss, 1985).
The wastes from zinc precipitation include a filter cake generated from initial filtering of the pregnant
solution prior to the addition of zinc, and spent leaching solution, which is often returned to the
leaching process. The filter cake consists primarily of fine gangue material and may contain gold-
cyanide complex, zinc, free cyanide, and lime. The filter may be washed with water, which is
disposed of as part of the waste. The waste is typically sent to tailings impoundments or piles.
3-53 Seotember 1994
-------
II
r'^inSiSivililliilpiiu "lifii,1!!? SBS
U11Ifllli!'1 quit >gil,i!l l!^lh,i' 11lllllffi^ •Illllli I 'ill1 Itll " i J'I'IW
iiiiii:"ii'u!j|iiiiiiiiii iniiiiiiiii ..... IIIIMIIIIII
and • • • '
Tank Leaching
i
As nojeji previously, tank leaching techniques ifoFgdd recove^" ''are pre^red over heq> iieaching"f6r
higher-grade ores, typically those with gold values averaging over 0.04 troy ounces per ton of ore.
In tank leaching operations, primary leaching takes place hi a series of tanks, often in the mill
building, rather than in heaps. Finely ground gold ore is slurried with the leaching solution hi tanks.
The resulting gold-cyanide complex is then adsorbed on activated carbon. In the Carbon-in-Pulp
I • • . •" ' ; t,j i- • - ;!" i • ..... r '• '• ..... • , •'.!:. ' , >• '
method, leaching and adsorption 'occur in two separate series of tanks; in the Carbon-in-Leaching
..... method, they occur- in a single series. Both are described below. In either, the pregnant carbon then
: undergoes elution, followed either by electrowuming or zinc precipitation, "as described previously.
The recovery efficiencies attained by tank leaching are significantly higher than'for heap leaching.
typically recover from 92 to 98 percent of the gold contaned hi the ore.
1
Continuous countercurrent decantatibn (CCD) is a method of washing the solution containing metal
values from the leached ore slurry to produce a clear pregnant solution. This procedure is used for
ores with high silver values that preclude the use of activated carbon and that are very difficult to
filter, thus precluding the use of filters. The resulting pregnant solution is generally treated by the
zinc precipitation technique described above. , • .
A new technology employed in South Africa uses ion exchange resin in place of carbon in the CD*
" ............... This ...... gg^j(^y_^^jn^^ ...... ^^p^,,,,__^ ...... _.. ..... _^_ ..... __^ ..... ££jj ..... ^o^'and ...... energy
i-'te use o ion exchange resins is found to be gQ^z^ggg ...... — — — ...... -— - ..... — -- ...... .-.-—- ..... .__ ......
IliliiW^^^^^^^^ ...... .......................................... ' [[[ -,,~ ............................. ; [[[ •, ..... - .................. , ........... ' ...... ' ....................... : ........................ !!, ............... ' ..... ,
ftto "
inn" i|"iii !i|vi ininiipi qiiiii .|..uiiiiii:.ii|iii|niii m'l'i f. > inraini'in'iiiiiiiiiiiiiiiiiiiii "»'., iJ:"
Caifeonrte-ulpjClP). In the OP technique, a Slurry of ore, px'vt''cyaiae, and' lime" fe
|
; punned jjjj^jgjj a series of tanks for agitation and leaching. Then, the slurry containing leached ore
and pregnant solution is pumped through a second series of tanks for adsorption (or subjected to
continuous countercurrent decantation).
•ill I 111(111 111 Illi IK lllllllliillllli ilillililllli lillllllllll lllllllllllllllllllliil ill I
I »
In the second series of CDP tanks, the slurry is introduced into a countercurrent flow with activated
i i i
carbon. The slurry enters the first tank hi the series, which contains carbon that is partially loaded
with the gold-cyanide complex. In the suspended slurry, the activated carbon adsorbs gold material
on the available exchange sites. As the carbon material becomes laden with precious metals, the
carbon is pumped forward in the circuit toward the incoming solids and pregnant solution. Thus, in
the last tank, the low-gold percentage solution is exposed to newly activated and relatively gold-free
carbon that is capable of removing almost all of the remaining precious metals in the solution. Fully
loaded carbon is removed at the feed end of the tank tram for elution, followed by electrowinnhig or
ES«ii£!s^!fi precipitation 'as described previously. (Bureau of Mines, 1978 and 1986; Stanford, 1987)..
-------
EIA Guidelines for Mining Overview of Mining and Beneficiation
Carbon-in-Leach (CIL). The CIL technique differs from CIP in that activated carbon is mixed with
the ore pulp in a single series of agitated-leach tanks. Leaching and adsorption of values occur hi the
same series of tanks. A countercurrent flow is maintained between the ore and the leaching solution
and activated carbon. In the first tanks of the series, leaching of the fresh pulp is the primary
activity. In later tanks, adsorption is dominant as fresh carbon is added to the system countercurrent
to the pulp. Adsorption takes place as the gold-cyanide complex mixes with the carbon. As with
Carbon-in-Pulp and heap leach operations; the pregnant carbon undergoes elution to remove values.
The pregnant elttate then undergoes electrowinning or zinc precipitation to recover the gold.
The number and size of tanks used in domestic CIP and CIL facilities vary. For example, the
Ridgeway facility in South Carolina uses 10 tanks measuring 52 feet in diameter and 56 feet in
height; the Mercury Mine uses 14 tanks, each of which are 30 feet in diameter and 32 feet in height;
the Golden Sunlight Mine uses 10 tanks, each of which are 40 feet in diameter and 45 feet hi height.
Retention times vary as well, ranging from 18 to 48 hours, depending on the facility, equipment used,
and ore characteristics (Smolik et al., 1984; Fast, 1988; Zaburunov, 1989).
For either CIP or CIL, ore preparation (including grinding, lixiviant strength, and pulp density
adjustment) and the time required to leach precious metal values vary depending on the type of ore.
Oxide ores are typically beneficiated by grinding to 65 mesh and leaching with 0.05 percent sodium
cyanide (for a pulp density of 50 percent solids) over a 4- to 24-hour period. Sulfide ores are
typically beneficiated by grinding to 325 mesh and leaching with 0.1 percent sodium cyanide for a 10-.
to 72-hour period (for a pulp density of 40 percent solids) (Weiss, 1985).
Both of these tank beneficiation methods produce a waste slurry of spent ore pulp, or tailings, which
is pumped as a slurry to a tailings impoundment (Bureau of Mines, 1986; Calgon Carbon
Corporation, undated; Stanford, 1987). The tailings slurry is composed primarily of spent ore and
water, along with small (but sometimes significant) amounts of residual cyanide, lost gold-cyanide
complex, gold hi solution, and any constituents hi the water, including those added to control scale.
The solid component of tailings consists of very fine materials, ranging from sand-sized to talc-sized.
The characteristics of tailings vary greatly, depending on the ore, cyanide concentration, and the
source of the water (fresh or recycled). In some .cases, the tailings slurry may be treated to neutralize
cyanide prior to disposal.
Tailings are disposed of hi large tailings impoundment (up to hundreds of acres). Disposal requires a
permanent site with adequate capacity for the life of the mine. The method of tailings disposal is
largely controlled by the water content of the tailings. Generally, three types of tailings may be
identified based on then- water content: wet (greater than 40 percent of the total weight is water),
thickened (approximately 40 percent water), and dry (less than 30 percent water). Where topography
allows, tailings impoundments are located near the mill, but pipelines can be used transport tailings to
3-55 September 1994
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tf "i
b
pgg i|;;Mjijgg and Benefication • ' EIA Guidelines for Mining-
suitable locations a male or more away (always downhill). The design of tailings dams depends
prfiarily on the topography and the configuration of the impoundment (see Section 3.2.6); the
" " preferred method is for the dam to span a valley, with tailings impounded in the vallev Dam
(ill ...... 1(1 ......... i ...... l ........................ _ ...... l .................................. l ..................... i ................ 1 .......... ill [[[ I [[[ ilil ....... Hi ..... ill ........ iiiii ..... iiiiii ..... ill ................................... , ....... 1 [[[ 1 ........... 8 ................. .............. iiSm .................... i [[[ , .................................. ........................................ J ' .......... __1!J, [[[
construction materials include native soils and clays, waste rock, and components of the tailings (e.g.,
coffser ss^s ^ pff^111.31638 of ** dam and frra "slimes" on the upper face. Dams must be
engineered to withstand seismic events, and to control the flow of liquids through or under the dam to
prevent catastrophic Mure. Dam design must also consider water flow in the drainage following the
act*ve *** °f tte mine, since free water is ticall ket to a minimum
mine, since free water is typically kept to a minimum during operation by recycling
it b(ack to" the roll. '
I HI H |
' « "
In rjart because of the Clean Water Act requirement that there be no discharge from gold beneficiation
use_cyanid^ttira methods,- most of the liquid component of tailings is recycled back to
. Newer tailings impoundments are on prepared surfaces of compacted soils and clays, with a
unpoimdments using clay or synthetic liners. In addition to water in the tailings slurry, .there can
j^^ -| ^j^^ r^ ^ impoundment (this volume of water may be. discharged under
..... Sis ..... iffk ..... ..... & ..... 2S2,5,,,2S ...... ss, ..... & ..... te ..... SsSioasSiSary to *»i&s* ..... sns ...... °i ...... m°i« ....... seepage
SSSSISS ....... SSSSfity ;downgradient of the tailings dam. This has proven necessary for
^3jj%s»l interrelated reasons: the zero discharge effluent u^mjtatign'guideunes, which requite
' seepage to groundwater; State groundwater protection
"
;=^ ....... ^,,,,;I?qgire lineis or other means to reduce^ the ]ps$ of fluids" to the, sjAsurfece; the
[[[ ?!!^* ...... ^"?§S?i ........ !5-^:.^Sg ....... §9™ P*L *!jy ....... S^L Haffi grouridwater infiltration;11 and the need to
control the movement of fluids through or under the dam. During the active life of the mme,
solutions captured 'in such ponds are generally pumped back to the impoundment itself or directly to
the mill.
1 '
i
States usually require reseeding/revegetation of impoundments when the mine closes. Because
...... are ..... often ..... to ...... diainaies, ....... redamation ..... may include ..... pennanent ...... .diversions, ..... .around, ..... the
Ill III 11111 111 111lllllll
Hi I 111
...... ..... ..... ...... ....... ..... ..... ...... ., ..... ., .....
tailings or gating 3^^ over or through the tailings. Reactive tailings (e.g., acid-forming) may
fc^, ..... f0,,,,^ ..... Sffi! ..... ,!^!2S ...... SlSSXiPft ^ ro°t penetration or erosion of any such caps may have to '
be considered in reclamation planning, , . *
.
I ,
33J; GOLD PLACER MINING
Placer mines have historicaUy produced approximately 35 percent of the total U.S. gold production.
iKgSfr, ..... SHE ...... SI £°}d pwduj^ntai ....... mcreased, ...... annually in recent years, placer production has
decrt[ascd ^ *» readily accessible placer deposits have been mined put and with the development of
S^j ...... SSSfeSffi ..... Kfifffi10^ ....... IbFmlning ....... and ..... bradBda^g ..... lode ...... deposit ............... placer ..... rnines produced
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EIA Guidelines for Mining Overview of Mining and Beneficiation
The size and nature of placer mines range from open cut operations disturbing tens of acres annually
to small sluices operated solely as a recreational activity. In 1987, the average number of employees
at placer mines in the contiguous 48 states was between three and four, and few mines employed
more than 10 people (EPA, 1988b).
Regardless of size, most placer mines operate on a seasonal basis (ADEC, 1986; EPA, 1988a). The
small size of .most placer operations and the relative ease in establishing an operation make it difficult
to establish the number of mines operating at any one time (EPA, 1988a). A 1986 EPA survey
showed a total of 454 placer mines in operation in the U.S. Also in 1986, the Bureau of Mines
estimated there were just more than 207 operational placer mines. While the final totals are quite
different, both surveys revealed the overwhelming majority of the mines were in Alaska (190
according to EPA and 195 according to the Bureau). All the mines identified in both surveys were
west of the Mississippi, with most large operations in. Alaska.
Placers exist in different types of sedimentary deposits (fluvial, marine, eolian, etc.), although they all
originate from lode deposits. Most of the gold placers mined in the U.S. are of fluvial origin. Placer
deposits are typically found in unconsolidated sedimentary deposits, although depending on the nature
of the associated materials, placers may be cemented to varying degrees. The terms pay streak, pay
dirt, and pay gravel refer to the zone where the economic concentration of gold is located. This layer
is often found adjacent to the bedrock. Finer gold particles are carried farther from their source and
have a greater tendency to be distributed throughout the sediments in which they are found. The
value of the pay streak is usually assessed as troy ounces per cubic yard, and varies throughout the
deposit (Boyle, 1979).
The density of gold, and its resistance to weathering, are the two principal factors for the
development of placer deposits. Gold is considerably more dense that the minerals typically
associated with it (19.13 grams per cubic centimeter (g/cc) versus 2.65 g/cc for quartz). Heavy
minerals typically settle to the bottom of a stream or beach, displacing lighter material in the process.
Gold continues a downward migration in response to additional agitation in the streambed. Settling
action also occurs on land hi colluvium although the downward migration is not as pronounced hi the
absence of a fluid matrix. Placer deposits are formed as particles accumulate hi this manner (Park
and MacDiamid, 1970).
At a typical placer mine, overburden is removed and ore is blasted to fluff-up the material and make
it easier to excavate. The ore is then hauled by trucks to a wash plant, which consists of a
combination of equipment used to size and concentrate the ore. A typical wash plant consists of a
grizzly and/or a trommel, where sizing takes place. The ore is then washed into a sluice, where the
gold (and other heavy minerals) settle below the riffles and onto matting. The gold remains hi the
sluice, while the tailings and wash water flow out of the sluice and into a tailings or settling pond.
3-57 September 1994
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IIIIIIM^ IIIIIIIIIH Illlllll i 1 H 111 Ililllllllllllli II 'I Illlllll^ Illllll Illlllll Illlllll II Ililllllllllllli il IliiH^ II Illlllll 111 111 111 I 111 111 11 111 Illlllll 1 Illlllll 11111 Ililllllllllllli 1 111 li 111 II Illlllll IP Illlllll IIIIH^^ Inlll 1 Ililll Illlllll I 111 III III11III1 111 ' 11111
Ililllllllllllli l|illlillHii|llilH Ililllllllllllli I PI
Overview of Mining and Beneficiation _ EIA Guidelines for Mining
. IIIIIIH Illlllll III Illllll I Illlllll Illlllll 1 1 IIIIIIH III II I Illlllll I II 111 •Ililllllllllllli Illllll 111 11111 Ililllllllllllli ' 1 1 II 1111 III I l 1 Mill II I ' I I i Illlllll
Periodically (every 1-2 days), the wash plant is shut down and the gold is removed. The concentrate
may then be subjected to further, more refined concentration, with gravity separation techniques such
as jigs, shaking tables and pinched sluices, and possibly magnetic separation, if magnetite is present,
to produce a high grade concentrate suitable for processing.
i [[[ : ..................... ' ......... : ............ , ' , • ' '• • ' i ' •'• .............. :"'"; ........
333.1 Mining ' "' ........ • [[[ ! .......... '• .............. '. [[[
i , • , , ; ^ ' . ' ^ " i ' • '
Extraction methods employed at gold placer operations differ, substantially from hardrock extraction
. Large amounts of overburden, waste rock, and ore must be excavated and concentrated to .
— — —
..... gjjj ..... pjacer mines ....... is ...... high, ........ sometimes ...... as ...... high as 10:1. ............. In ..... toe coldest ..... regions where gold '
!!!!"!"§ ...... i^c£m^» ....... S^^Sl^^^iconsisting of vegetation, ....... muck, ....... and ..... waste ...... rock) and ore
_ ^__^ _ j^^^j -y blasting and/oj. mechanical means prior to extracting the ore. They may
, ^ '
extraction at placer operations may be conducted using either surface or underground
"» to* 55^5, 5E§!5ds 52 m,2§! commonly used because they generally are the least '
» i??0): Jhe principal surface extraction method is open cut mining. Other
.
.SSSKxk employed at gold placer mines include dredging, hydraulickhig, and other
small-scale extraction techniques, such as panning and small suction dredging.
Gently, use of dredging and hydraulicking methods is limited in the United States. Underground
methods include bore-hole and drift mining. (Alaska Miner's Assn., 1986; Argall, 1987)
1987).
™!J!Fg "^yes stripping away vegetation, soil, overburden, and waste rock to reach the
..... below. ..... ,, ..... IMpay ore is blasted if necessary and can be excavated by bulldozers, loaders,
Si ..... f2iS2Sa ........ SSSESS ...... 2£ ..... SHElS ...... .&S2 ..... S2Ssport the ore to a wash plant"" for' beneficiation. '
..... 2£ ...... fSSSSSa ..... ^^^^^^^SS^S^ ...... *** ..... ™& Plant, and me direction of the
activity is awayr:frpm ..... Ae plant. ^Once a cut has been mined, it is generally either backfilled
excavated overburden and waste rock or converted to a water recycle or sediment pond (ADEC
Dredges are used hi both surface mining and underwater mining of placer deposits, but are generally
ass0cifed wira *e mining and beneficiation of metal-bearing minerals (yalues) below water level.
..... I* ..... SBlilliy , of a saturated placer gold deposit or the existence of a water
lllllll Ililllllllllllli
,
table near the surface to create the appropriate excavating environment (i.e., a pond). Four
-------
. EIA Guidelines Tor Mining - Overview of Mining and Beneficiation
is generally a sluice box. The pressurized water jet can also be used to thaw frozen muck and to
break up and wash away overburden. This is generally not used today, having been outlawed hi most
jurisdictions. However, hydraulic removal of overburden may still be practiced at a few mines
* * H
Small-scale extraction methods include panning and suction dredging. Panning is a low budget, labor
intensive method involving fairly rudimentary gravity separation equipment. Panning is also a
sampling method used by prospectors to evaluate a placer gold deposit to determine whether it can be
mined profitably. Small-scale gold placer miners also use a variety of other portable concentrators,
including long loins, rocker boxes, and dip boxes (EPA, 1988a). Small suction dredges are used by
recreational or small (part-tune) gold placer ventures. A pump varying from one to four inches
usually floats immediately above the mined area. The mechanism that recovers the gold sits hi a box
next to the suction pipe and is carried under water. Alternatively, the nozzle has two hoses, one that
transports water to the head and the other that transports material to the surface of a beneficiation
device (i.e., usually a small sluice box that deposits tails back into the stream).
Drift mining and bore-hole mining are terms applied to working alluvial placer deposits by
underground methods of mining. Drift mining is more expensive than open cut sluicing and
hydraulicking, so it is used only hi rich ground. In drift mining, the paystreak is reached through a
shaft or an adit. Ore that has been separated from the vein either by blasting or with hand tools is
carried hi wheelbarrows or trammed to small cars that transport the gravel to the surface for
beneficiation. If a deposit is large, then regular cuts or slices are taken across the paystreak, and
work is generally performed on the deposit hi a retreating fashion from the inner limit of the gravel
(DOI, 1968; Argall, 1987). . .
3.3.2.2 Beneficiation
Beneficiation of placer ores involves the separation of fine gold particles from large quantities of
alluvial sediments. Gravity separation is the most commonly used beneficiation method. Magnetic
separation is used hi some operations to supplement the gravity separation methods. Water is used hi
most, if not all steps to wash gold particles from oversized material and then to move ore concentrate
through the wash plant. For land-based operations, the plant may be stationary but is often mounted
on skids so that it can be moved along with the mining operation as it progresses. Dredge operations
frequently employ floating wash plants, where the beneficiation equipment is carried within the
dredge.
Beneficiation typically involves three general steps: the first is to remove grossly oversized material
from the smaller fraction that contains the recoverable gold; the second is to concentrate the gold; and
the third is to separate the fine gold from other fine, heavy minerals. The same type of equipment is
often used hi more than one step. For example, an array of jigs may be employed to handle
successively finer material (Flatt, 1990).
3-59 September 1994
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I !" • • '" •*•'•••:•'• • "•"" •"" - ' ' "" : ' ' :I '"'I ; • •' • : "
i, • i, ' ,
It "
' i
Overview of Mining and Beneficiation • E3A Guidelines for Mining
t " • . . . • • I
Classification (sizing) is the initial step in the beneficiation operation when the large, oversize material
X«s5aHy Over" 3/4 |5J) g JJnioved duringlieneficXrf^ A rough' (large "diameter)' screen is" usually
used. This step may be fed by a bulldozer, front-end loader, backhoe, dragline or conveyor belt.
Within the industry, this step is also referred to as roughing (EPA, 1988a). The ore is then subjected
fp^a coarse conc^njratfon stage. This step, referred to as cleaning, may employ trommels or screens.
Other equipment used in the coarse concentration stage includes sluices, jigs, shaking tables, spiral
concentrators and cones. Depending on the size of tie gold particles, cleaning may be the final step
in Dcneficiation (Flatt, 1990; Silva, 1986)^ .' "
i ' ' I' i '
Hpe, ..... cooceotration ig ...... the ...... final ..... operation used ..... to remove | very small gold values from the concentrate
WngiaafenBed in the previous stages. Many of the previously identified pieces of equipment can be
calibrated for finer separation sensitivity. Final separation uses jigs, shaking tables, centrifugal
concentrators, spiral concentrators or pinched sluices.
' '• • , ' " • ' .;|,i I ' " '
• ! ! "'","'. ; ••"> . i1 '• " . "' • "'
333,3 Wastes and ..... Management Practices '
Mining and beneficiation wastes associated with gold placer mining include tailings and water used
for beneficiation. Mp|t of these materials are either disposed of at the mine site (overburden and/or
tailings), recycled during the active life of the mine (water), or used for onsite construction material
or reclamation concurrently with mining or after operations end (overburden and/or tailings). Large
amounts of overburden or waste rock are associated with placer mining. Because the desired material
IB sfH;s ' 'i,!!!!,!!: is such a small fraction of the material mined' (< 0.1 troy oz/ton) there is a tremendous amount of
waste rock generated. Then, large amounts of water are used to process the material. The type,
volume, and characteristics of the wastes resulting from gold placer mining, as well as the waste
.management units associated with these wastes are discussed below. (Again, the use of the term
"wastes" is not intended to identify materials that are "solid wastes" under RCRA.)
iiiiii|iiiiii iiiiiiiii 1 1 • ( i ii n n ' '
i n
Waste rpck is generally disposed of in waste rock dumps near the point of excavation. Eventually,
the stockpiled waste rock may be used to backfill the mine cut during reclamation. Surface mining
operations generate more waste per unit of crude ore extracted than underground operations, although
stripping ratios vary from one site to the next." Overburden removed from the mine cut is stored
111 IIIIIIIII 1111 1 III II III 111 I IIIIIIIII IIIIIIIII I _ ^mil 111111 111 Illllin^ IIIIIIIII III I IIIIIIIII 111 • o»vriWM
p nearby, sometimes piled along the edge of the pit until mining ceases, at which time it is used to
backfill the cut.
% • . . „ ,
-.,, ; i i;
Wastes from gravity concentration operations consist of a slurry of gangue (non-gold material) and
process water that passes through tie ...... ^^j^g^ ....... ope^tionT ............ Tailings 'are ..... dassified ..... by ..... their ...... size
into three classes: coarse or oversize tailings, intermediate tailings (nuddlmgs), and fine tailings
(sl™ps)- Of the three grades delineated, fine tailings can be further broken down into two categories.
••™w''l' ..... Components of the slurried tailkigs can be classified as settleable solids, which are made up of sand
3-60 September 1994
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EIA Guidelines for Mining . Overview of Mining and Beneficiation
and coarse .silt, or as suspended solids, composed mostly of fine silt and some clay size particles.
(EPA, 1988a)
Large volumes of flowing water are used to cany the ore through the classification operation. The
velocity of the flowing water generates a large volume of intermediate and fine tailings in the form of
suspended sediment and lesser quantities of dissolved solids. Historically, the water and sediments
were released to streams and created problems downstream from the mining sites. Currently, release
of sediment is controlled by using impoundment structures where the water is held and the velocity is
consequently reduced. As flow is restricted, sediments are deposited. Exposure of waste rock and
ore during mining and beneficiation greatly increases the likelihood that soluble constituents will be
dissolved. Once in solution, dissolved solids are much more likely to pass through sedimentation
structures and reach surface waters.
Recycling or recirculating water at gold placer mines reduces the volume of effluent to be discharged
after treatment. Production statistics from 1984 show that 21.3 percent of the Alaska gold placer
mining industry achieved 90-100 percent recycle of the process wastewater (Harry and Terlecky,
1984a). Operations that separate oversize tailings prior to sluicing typically use less water than mines
that do not classify the excavated material (Harry and Terlecky, 1984b). Where classification
methods are used, approximately 1,467 gallons of water per cubic yard of ore are needed, whereas at
mines-that do not classify material, average water usage is 2,365 gallons per cubic yard of ore (EPA,
1988a; ADEC, 1987). The Clean Water Act effluent limitations guidelines for placer mines (40 CFR
Part 440, Subpart M), promulgated in 1989, generally require recycling of process wastewater and
have reduced the total discharge of wastewater from placer mining operations.
Chemicals are not typically used during beneficiation at placer gold mines, so tailings contain the
same constituents found in the extracted ore. Potential natural constituents of gold placer wastes
include mercury, arsenic, bismuth, antimony, thallium, pyrite, and pyrrhotite. These are often found
in discharges from placer mines.
.-
*
Waste and non-waste materials generated as a result of extraction and beneficiation of gold placer ore
are managed (treated, stored, or disposed) in discrete units. These units are divided into two groups:
(1) waste rock piles and (2) tailings impoundments.
In general, the goal of treating or managing waste streams of gold placer mines is to separate the silt
and fine-grained solids from the water, reusing the water or ensuring it meets NPDES discharge
requirements prior to discharging to a stream. Most waste management occurs after sluicing; die
stacking of overburden and waste rock in areas proximate to the mining operation, however,
constitutes an interim method of managing the materials prior to their ultimate return to the mine cut
(Alaska Miner's Assn., 1986).
3-61 September 1994
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in in in in 11 iiiiiii ill 1 in iiiiiii iiiiiii 11 iiiiiiiiiiiiiiii in 11 Hill i iiiiiiiiiiiiiiiliiiiliiiiiiiiiH iiiiiiiiiiiiiiiiiiiiiii
I lllllllllllllll|llllllllll P'M IIIIIII III III IIIIIIH III IIIIIII I IP III III i in IIIIIII III In I III III 111 III II 111 III 1 I I II I lllllll I III illlllilllilllil III I lll| 111 111 111 lllilll III I III llll III 111 III lllllli III 1 lllllll III lii'in
*
Ofgijgw ...... of,,MMng and Benefication _ EIA Guidelines for Mining
' """" ~ ~ ~ "* ~~ ~ """ *"*** **"*
I lllllll
..
SIS SS2 Hays to maximize the quality of the effluent discharged from a gold placer operation.
Tbg^are ..... used ...... separately ...... or, ........ increasmgly ...... frequently, ....... together. The effluent can be .treated, using a
variety of impoundments (tailraces, pre-settling ponds, and settling/recycle ponds), filtration, and, in
rare instances, flocculants. The mining operation also can be modified to reduce water use during
beneficiation, thereby reducing the volume of effluent discharged. Waste, management methods used
to achieve this reduction include classification^ recycling, use of a bypass, and control of water gain
..... " ..... ...... - ...... ,—~ ...... _™,™__ ....... «._,, ......... —.. ............ .............. _ ,
•* * " i
Tailings are typically disposed of in impoundments or used for construction. The method of tailings
disposal is largely determined by the water content of the tailings. Tailings impoundments associated
with gold placer mines are generally unlined containment areas for wet tailings. At most gold placer
opetittfons, the disposal of tailings requires a permanent site with adequate capacity for the life of the
mine. The size of tailings impoundments varies between operations, however, if the impoundment is
going to function effectively, the dimensions and characteristics are tailored to meet the specifications
i fora paiticular operation.- -•'•••-
Tailraces and pre-settling ponds are characteristic of open cut surface mining operations. Even at
open cut mines, however, there are variations of the typical tailrace and pre-settling pond. Two pre-
settling ponds are sometimes used simultaneously and in series to provide extra storage hi case die
first pond fills prematurely or in the event that a scheduled cleaning is missed. Alternatively, two
parallel pre-settling ponds might be used at alternating times. (Alaska Miner's Assn., 1986; ADEC,
1987) Settling ponds are similar in form and function to tailings impoundments and are used
primarily by large-scale placer operations. Settling ponds are usually created by constructing a dam
composed of tailings across the downstream end of the mined cut When.the next cut is mined, most
°f 1^?, 55?¥^,,§**lllStt Is captured hi this new pond. Thus, as mining progresses, a series of ponds
emerge.
3.3.2.4 Environmental Effects
Most environmental effects associated with placer mining activities concern water quality.
Historically, the most severe impacts have been physical disturbances to stream channels and the
addition of large quantities of sediment downstream.
initiation of any regulatory controls, little or no effort was made to recpntour waste rock
piles to resemble premming topography. Natural revegetation of historical placer grounds from
Alaska to California ranges from none to complete. Depending on the remaining substrate, natural
fSSSi I55555 II I°!Si ,§?,£§§ 53?y ^e a century to return to premining condition. These operations
were also responsible for generating large quantities of sediment and increasing concentrations of .
bsavy metals, including arsenic, copper, lead,'and mercury, downstream from mining activities
(ADEC, 1986; Clark, 1970; HMniesi 1981)! '"
3-62 September 1994
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EIA Guidelines for Mining Overview of Mining and Benefication
A 1985 Alaskan field study indicated that total suspended solids were elevated in a number of actively
mined streams. During this study, sediment ponds were employed at some operations and provided a
wide range of effectiveness. Downstream uses such as water supply, aquatic life, and recreation were
precluded as a result of the increased sediment loads in two of the three streams studied. Fine
sediments were readily carried downstream in response to increased stream flows (spring runoff),
therefore the severity of localized impacts could change with time as sediments were picked up and
redeposited in different locations downstream (ADEC, 1986).
The same study found mat total dissolved solids were not categorically increased as a result of mining
activities although levels of iron, manganese, cadmium, mercury, copper and arsenic were elevated
below mining operations in some streams. (It is not clear from the study whether these concentrations
are expressed as total or dissolved). A study of water quality within the Circle District, Alaska,
conducted in 1983, showed elevated levels of total arsenic, copper, lead, and zinc, and elevated levels
of dissolved arsenic and zinc downstream from placer mining activity. Mercury and cadmium levels
were not elevated downstream from mining. Concentrations of dissolved constituents are typically of
more concern in terms of water quality as the dissolved fraction is available for uptake by living
organisms (ADEC, 1986; LaPierriere, et aL, 1985).
The physical locations of placer mining activities and wetland ecosystems often overlap. Mining
activities, particularly those mining recent alluvial deposits potentially impact wetlands directly during
the removal of vegetation and soils or indirectly by removing or rerouting the hydrologic regimes that
support wetland hydrology. Operators impacting wetlands are required to obtain a Clean Water Act
Section 404 permit, and comply with Section 404(b)(l) guidelines.
Wildlife may also be impacted by placer mining through the physical disturbance of stream channels,
the addition of sediments to streams, and the presence of human activities and heavy equipment in
what are typically remote areas. Mining presents a physical barrier to fish migration through the
disruptions diversion of active stream channels. Sediment concentrations in streams can result in
gffl damage, reduced fertility, and changes in blood chemistry, and reproduction may be inhibited or
precluded when spawning grounds are lost to siltation and eggs are suffocated when covered by
excess sediment (ADEC, 1986; Reynolds, 1989).
3.3.3 LEAD-ZINC
In 1990, there were a total of 29 lead/zinc mines operating within the United States. Of these 29
mines, 16 produce both lead and zinc; two produce lead but not zinc; and 11 produce zinc but not
lead. In 1990 alone, these mines produced 495,000 metric tons of lead concentrate (making the U.S.
the world's largest primary producer) and 515,000 metric tons of recoverable zinc. For the same
year, employment figures were estimated to be 4,500 workers at mines and mills and 3,300 at
secondary smelters and refineries. Twenty-one of the mines are located west of the Mississippi, in
3-63 September 1994
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Overview of Mining and Benefitiation
EIA Guidelines for Mining
States of Missouri (9 mines), Idaho (3), Alaska.(2), Colorado (2), 'Washington (2), Montana (1),
Mexico(1), and Oregon (1). The remaining eight mines are located in Tennessee (5 mines) and
New York (3).
:I| ...... | ...... || ..... P™S|y ...... £2 ..... S25ES5SS ..... Jfid
...... percent ..... » ..... iMJl
...... CZO percent) in batteries,- fuel tanks, solder, seals,
e^^
!^!!^!!Mj^^OT, and other industries. U.S. and world demand fe Jeclinedjn recent years, in large part
SBS&j^!^ !?, 22H5HM concerns. Z|ne, Js isgl |n galvanizing (53 percent), zinc-based alloys .
[[[ .....
l=~™r®? J=j==ik brass ^ br°nze <14 percent), and for other purposes.
m indergj;ound_pperations, although a few surface
tist. The decision to use underground or surface mining techniques is dependent on
*S.!ffiSS ££?.«££& 2 22 ZS2;,, £SSS5S&&to* .techniques are commonly used to '
extract lead-zinc are from large, flat^ymg, Jabular-,shaped, strata-bound deposits. In contrast,
•deposits isTjest ^tedjojnare selective,stope mining .
y the i
I Hill 11(1 II I Ill III III
II II I III III 11 II III
»' • " is • s&Bfflsss ,£i:!!::a \ '"'''""'""''' ''
! ofjeadjnnc§155 ranges from as low as three percent metal in ore for large, easily
.] SSjjjjjS £51522 f°£, SS3L £Sto!&&aSSSa& underground mines, to more than 10
for extremdv .high-cost.remote,,,,,areass I^w grade lead and zinc ores can also be mined
y^^ when Produced as a byproduct of copper mining, or when appreciable quantities of preci
ous
i^S£ SS £ Illlt S ESS! fffSS JS&k Few,!e§d3|nc deposits contaui more than 50
s%± tons of ore.
iliiioiw^ ':':!.i!lj«^
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JP.IIII;. i P4p,n ;IJH^
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Benfificiafion nf \i^>A unA •»?«/» M^«« :<. » *t.___ _*. . . .
S iSS&sjep process consisting of milling, flotation, and
|93S!yi[€|f£og (Bureau oLMinegj 1984c and, 1985).
1900s,, gravity concentration was the chief
owever, with more selective reagents and
tu^ Gra
M§ed ...... for preconcentrating before fine grinding and
nc ..... ores,,,were concentrated. .However, with more selective reagents and
o:,,,v|rtu^ Gravity
.
it lip (iH^^ {''ifii: . i! tmi4:ii', iipfhi^ !«i
Uli Slip gjj |5igi|iii2i 2EE!!25 dLSS&SS and grinding. Crushing is usually a dry
221 =22 SgraI5 ™?y .*? ??ntrol ^dust.' Frequently, a primary crusher Qaw crusher) is
4j le: S»ne; site, to ^reduce the ore material into particles less than 150 millimeters (mm) (6
iilllliM^
^^ iliil
; ' ' '' is '"' *3~O^
-------
EIA Guidelines for Mining Overview of Mining and Beneficiation
inches) in diameter. The crushed ore is then transported to a mill site for additional crushing,
grinding, classification, and concentration.
Additional milling uses a cone crusher, usually followed by grinding in rod and ball mills. Grinding
is a wet operation in which water and initial flotation reagents are added to form a slurry.
Alternatively, the ore may be fed into an autogenous mill (where ore itself acts as a grinding medium)
or a semi-autogenous mill (where the ore is supplemented with large steel balls).
Between each grinding unit operation, hydrocyclones are used to classify coarse and fine particles.
Coarse particles are returned to the mill for further size reduction. The resulting size of the classified
ore is; usually about 65-mesh (6.3 mm). Chemical reagents that will be used during flotation
separation activities may be added to the ore during milling activities (Bureau of Mines, 1985 and •'
1990a). .Mill production capacities can be as high as 7,000 to 9,000 tons per day.
Flotation ,
Flotation is the most commonly used technique to concentrate lead-zinc minerals. Several separate
flotation steps may be necessary to Jbeneficiate these polymetallic ores. Most sulfide ores contain
varying amounts of minerals such as lead, zinc, copper, and silver; thus, multiple floats are needed to
concentrate individual metal values (Bureau of Mines, 1985a; Weiss, 1985). The tailings (residual
material) from one mineral float are then used as feed for a subsequent float to concentrate another
mineral. A typical example includes the following steps (Fuerstenau, 1976):
• Bulk flotation of lead-copper minerals
• Depression of zinc and iron minerals using such chemicals as sodium sulfite and zinc sulfate
• Flotation of a copper concentrate
• Rejection of a lead (sink) concentrate using sulfur dioxide and starch
• Activation and flotation of the sphalerite (using copper solution) from iron and gangue
minerals
• Flotation of pyrite, if recovery is desired
• Flotation of barite concentrate.
The froui recovered in each of the cleaning cells is transferred to thickeners, where the concentrate is
then thickened by settling. The thickener underflow (the concentrate) is pumped, dewatered by
passage through a filter press, and then dried. The liquid overflow from the thickener contains
wastewater, flotation reagents, and dissolved and suspended mineral products. This solution may be
recycled or sent to a tailings pond (Fuerstenau, 1976).
3-65 September 1994
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lllllfl Ill IIP ill I'llilM I ("Ill i'lilltliilllll 1 1 Ilill ill
. .
""Overview of Mining and Beneficiation
EIA Guidelines for Mining
Wastes from the various cells (typically rougher, scavenger, and cleaning cells) are collected and
directed to a tailings thickener. Overflow from this unit (wastewater containing high solids and some
wasted reagent) is often recycled back to the flotation .cells. Thickener underflow (tailings) contains
remaining gangue, unrecovered lead-zinc material, chemical reagents, and wastewater. This
underflow is pumped as a slurry to a tailings pond. The solid content of the slurry varies with each
operation, ranging from 30 to 60 percent.
|l"l ' ' ' ' . .',..!
I Ill J ' ' ' ''
Sintering
Concentrates of lead and zinc minerals that are to be processed by pyrometallurgical methods, such as
smelting and refining, may require sintering, depending on the processing methods used. Sintering
'llflgf . iiiiiii iiiiiiii Hill iiiii iiiiiiiii in iiiiii iiiiiiiiiii i iii iiii iiiiiiiiiii 11 iiiiii iiiiiiiiiiiiiiiiiiii i ill 111 in i in in iiiiiiiiiiii i 11
operations consist of several steps, including blending, sintering, codling, and sizing. Raw materials,
' ' U tJreeze are
blended with small amounts of moisture in pug mills, balling drums, or balling pans. The concentrate
feed is men fired (sintered) .and cooled". The suiter is crushed during cooling and is typically less than
six inches in diameter. This product will be graded and further crushed in some operations to
produce a smaller sinter product (Weiss, 1985). Four of the five primary lead processing facilities in
the United States sinter the concentrate prior to processing.
Wastes
i I
Wastes generated by lead-zinc operations include mine water, waste rock, tailings, and refuse. Many
of these wastes may be disposed of onsite or offsite, while others may be used or recycled during the
active life of the operation. Waste constituents may include base metals, sulfides, or other elements
found in the ore, and any additives or reagents used in beneficiation operations. The primary waste
generated by underground mines is mine development rock, which is typically .used in onsite
, Lin ,i W construction for road or other purposes. Surface mines usually generate large volumes of overburden
[and waste rock that arg usually; disposed of in waste rock dumps. (As before, "wastes" discussed
here are not confined to RCRA solid wastes.)
!' ' • [
' i
Overburden and Mine Development Rock
5M5PS include overburden and mine development rock
to as waste rock. As noted previously, the materials can be used onsite or placed
waste rock dumps. The quantity and composition of waste rock generated at lead-zinc mines varies
|'|||"|| I || ''III!!!!!!!!!!!!!!!!!!!,!!!!!!!!!"!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !1!!!!!!!!!!!"!!!!!!!;!!!!!!!!!!!!,!!,!!'!' I!!!!!!!!!'!:!!!!!,' I!!!!!!!!!!!!!!!,!!! I!!,!!, ,!!!!!!!!!!,,!!!1!! I!!!!!,,!!!!!!!!!!!!!!!!!!!::!!!!!!1!1'!!!!!,!!!' „„!!!''"!: ; ; ; „ : :,: : a, s : i i i \ : :„: i:
*tly_ bejEES! sites. These, .wastes wjll .contain mmeralg a§sp5cjated wjjjjj jjjg pie body andi host rock.
minerals associated with sulfide ores are chalcopyrite, pyrite, calcite, and doloniite (Weiss,
;,.. ^I:MM^^^ KM W:T«IB^^^^^^^^^^^^^^^
\ September 1994
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EIA Guidelines .for Mining ' Overview of Mining and Beneficiation
Mine Water
Mine water consists of all water that collects in mine workings, both surface and underground, as a
result of inflow from rain or surface water, and groundwater seepage. As necessary, water may be
pumped from the mine to keep it dry and allow continued access to the ore. The pumped water may
then be used in beneficiation, pumped to tailings ponds, or discharged to surface water. The quantity
and chemical composition of mine water varies from site to site, depending on the geochemistry of
the ore body and the surrounding area. Mine water may also contain small quantities of oil and
grease from extraction machinery and nitrates (NO3) from blasting activities. Based on studies of lead
mines in the United States, the range of concentrations in mine water (mg/1) for lead was 0.1-1.9,
zinc 0.12-0.46, chromium 0.02-0.36, sulfate 295-1,825, and pH 7.9-8.8. After the mine is closed
and pumping stops, the potential exists for water exposed to sulfur-bearing minerals in an oxidizing
environment, such as open pits or underground workings, to acidify. This may lead to the
mobilization of metals and.other constituents in the remaining ore body exposed by mining and to the
contamination of surface and/or groundwater. Alternatively, flooding of underground workings can
reduce exposure of sulfide minerals to oxygen and effectively eliminate acid generation.
Flotation Wastes ' .
After the removal of values in the flotation process, the flotation system discharges tailings composed
of liquids and solids. Between 1/4 and 1/2 of the tailings generated are made up of solids, mostly
gangue material and small quantities of unrecovered lead-zinc minerals. The liquid component of the .
flotation waste is usually water and dissolved solids, along with any remaining reagents not consumed
in the flotation process. These reagents may include cyanide, which is used as a sphalerite depressant
during galena flotation. Moist operations send tailings to impoundments where solids settle out of the
suspension. The characteristics of tailings from the flotation, process vary greatly, depending on the
ore, reagents, and processes used.
Chemical Wastes
In addition to wastes generated as part of extraction and beneficiation, fadlities also store and use a
variety of chemicals needed for mine and mill operations. A list of chemicals used at lead-zinc mines
is provided in Exhibit 3-8.
333.4 Waste Management
Wastes generated as a result of mining and beneficiating lead and zinc minerals are managed (treated,
stored, and/or disposed) in discrete units—waste rock piles or dumps, mine pits and underground
structures, and tailings impoundments.
3-67 September 1994
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Overview of Mining and Beneficiation
EIA Guidelines for Mining
lllllll 111 111 111 III II Illllllllll IIIIIIM^ Illlllllllllll lllllll 111 Illlllllllllll lllllll III IIIIIIIIIIIIIB 111 II Illlllllllllll 111 II 111 I Illlllllllllll 111 II III Kill 111 I lllllll II Illllllllll Illllllllll 111 lllllll 11 Illllllllll Illlllllllllll 111 I ll|lll|l II
111 •
Illlllllllllll Illllllllll
Exhibit 3-8. Chemicals Used at Lead-Zinc Mines
Acetylene
Calcium Oxide
Hexone
Hydrogen Chloride •
Methyl Chloroform
Methyl Isobutyl Carbinol
Nitric Acid
Propane
Sodium Cyanide
Sulfur Dioxide
SulruricAcid
Diesel Fuel No. 1
Diesel Fuel No. 2
Chromic Acid, Disodium Salt
Copper Solution
Kerosene
Methane, Chlorodifuoro-
Sodium Aerofloat
Sulfuric Acid Copper (2+)
Salt (1:1)
Zinc Solution
Zinc Sulfate
Source: National Institute for Occupational Safety and Health, 1990.
Waste Rock Piles
. I '
* i i i i | i •
Waste rock (overburden and mine development rock) removed from the mine is stored and/or
! Ill 111 lllllll disposed in nnlined piles onsite. Constituents of concern in runoff and leachate from waste rock piles
includes heavy metals. These piles also can generate acid drainage if sulfide minerals and moisture
1 Si1!! are present in sufficient concentrations without adequate neutralization potential or other controls.
I »
Mine Fits and Underground Workings
In addition to wastes generated during active operations, when the mines close or stop operation, pits
and underground workings may be allowed to fill with water. This accumulating water, which may
become mine drainage, can acidify through aeration and contact with sulfide minerals and become
contaminated with heavy metals. At pits where quartz minerals are associated with lead-zinc deposits,
silica dust exposure may be a problem bom during mine operations and following closure. Asbestos
be preseitt in pits where limestone and, dolomite ores are mined, may also be a
minerals,w
! _. I. ^r *•
gxi^y.S. Department of Health and Human Services, 1982).
Tailings Impoundments
5S ..... I§5§® .....
p£taiiijn|s ....... requires * P«rmaiMiit.she with adequate capacity for the life of the mine.
to several hundred acres in size. The method of tailings disposal is
; ,122, SEES! "
structures
!|;D« used to construct, a gilings pond: water-retention dams and raised embankments. Water
construction of a dam, usually in a natural drainage area, and tailings
topography to assist in
the dam. The water retention
of tailings and tailings water. A raised embankment is a phased approach to
in which the, garjhen dam structure, composed of native soils, waste rock,
.™ successive lifts over the life of the project as need arises and materials are
.< ii mi i
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EIA Guidelines for Mining Overview of Mining and Beneficiation
available. Water retention dams are more costly but typically allow greater storage of process water
and effluent in the impoundment.
33.4 COPPER
The physical properties of copper, including malleability and workability, corrosion resistance and
durability,.high electrical and thermal conductivity, and ability to alloy with other metals, have made
it an important metal to a number of diverse industries. Copper was an historically important
resource for the production of tools, utensils, vessels, weapons, and objects of art. According to the
Bureau of Mines, in 1992, copper production was used for building construction (41 percent),
electrical and electronic products-(24 percent), industrial machinery and equipment (13 percent),
transportation (12 percent), and consumer products (10 percent) (Bureau of Mines, 1993a).
The United States is the second largest copper producer in the world. Next to Chile, the United
States had the second largest reserves (45 million metric tons) and reserve base (90 million metric
!tons) of contained copper in 1992. United States' copper operations produced about 1.7 million
metric tons in 1992. In 1991, 1.63 million metric tons were produced. The total value of copper
produced in 1992 was $4.1 billion^ Arizona led production in 1992, followed by New Mexico, Utah,
Michigan, and Montana. In the same year, copper was also recovered from mines hi seven other
States (Bureau of Mines, 1993a and 1993b).
The number of operating copper mines decreased from 68 mines in 1989 to 65 mines hi 1992. Of the
65 mines actively producing copper in 1992, 33 listed copper as-the primary product. The remaining
32 mines produced copper either as a byproduct or co-product of gold, lead, Tine, or silver (Bureau
of Mines, 1993b). Thirteen of the 33 active mines that primarily produce copper are located in
Arizona; the remaining mines are located in New Mexico, Utah, Michigan, and Montana (Bureau of
Mines, undated).
In 1991, the top 25 copper producers in the United States accounted for more than 95 percent of the
United States' domestic copper production. These producers are listed in Exhibit 3-9 (Bureau of
Mines, 1993b).
3.3.4.1 Geology of Copper Ores
Copper deposits are found hi a variety of geologic environments, depending on the rock-forming
processes that occurred. In general, copper deposits are formed by hydrothermal processes (i.e., the
minerals are precipitated as suffides from heated waters associated with igneous intrusions or areas of
otherwise abnormal lithospheric heating). These deposits can be grouped in the following broad
classes: porphyry and related copper deposits, sediment-hosted copper deposits, volcanic-hosted
3-69 September 1994
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1 Overview of Mining and BeneScaation
. EIA Guidelines for Mining
in hi i id'linn inn n i inn
.
mini in iiiiiiiiiiiiiiiiiiiiini iiiiiiiiiiiiiiiiiniiiiiiiiii iiiiiiiiiiiiiiiiiiiiini
•1 iiiiiiiiiiiiiiiiiiiiiiiii1 ninnnnnniiiiiiinniiiiiinnnniniiniiiiinnnn
111 111 Illilli1 III ill
HillIIIII1I Illllil I Ill
M^\l Illllil I Hill 111 I
llllllH
III IIIIIIIIIIIIIIIIIIIIIIIII 1111111111 I Illllill
IIH^^^^^^^^^^^^^
*
Exhibit 3-9. Leading Copper Producing Facilities in the United States
Bank
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
Y:'-.^Mfcie>K;$A:
Morenci/Metcalf
Bingham Canyon
San Manuel
Chino
Tyrone
Sietxita
Ray Complex
Bagdad
Pinto Valley
Mission Complex
Inspiration
White Pine
Continental
TwinButtes
Troy
SanXavief
Superior (Magma)
Miami
Casteel
Silver Bell
Lakeshore
Johnson
Oracle Ridge
Yerington
Mineral Park
County and State
Greenlee, AZ
Salt Lake, UT
Final, AZ
Grant, MM
Grant, MM
Puna, AZ
Final, AZ
Yavapai, AZ
Gila.AZ
Pima, AZ
Gila, AZ
Ontonagon, MI
Silver Bow, MT
Pima, AZ
Lincoln, MT
Pima, AZ
Final, AZ
Gfla,AZ
Iron, MO
Pima, AZ
Final, AZ
Cochise, AZ.
Final, AZ
Lyon,NV
Mohave, AZ
^ -.is :'J .... -'. in .' * •'," ••• 'I VV...V, ',"
Operator?!?-';1--;^:'./.':' "":<*••'• •"••: ';':
Phelps Dodge Corporation
Kennecott, Utah Copper Corporation
Magma Copper Company
Phelps Dodge Corporation
Phelps Dodge Corporation, Burro Chief Copper
Company
Cyprus Sierrita Corporation
ASARCO Incorporated
Cyprus Bagdad Copper Company
Pinto Valley Copper Corporation
ASARCO Incorporated .
Cyprus Miami Mining Corporation
Copper Range Company
Montana Resources, Inc.
Cyprus Sierrita Corporation
ASARCO Incorporated
ASARCO Incorporated
Magma Copper Company .
Pinto Valley Copper Corporation
The Doe Run Company
ASARCO Incorporated
Cyprus Casa Grande Corporation
Arimetco Incorporated
South Atlantic Ventures Ltd.
Arimetco Incorporated
Cyprus Mineral Park
3-70
September 1994
IM^^^^^
• ' ilinil
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EIA Guidelines for Mining Overview of Mining and Beneficiation
massive sulfide deposits, veins and replacement bodies associated with metamorphic rocks, and
deposits associated with ultramafic, mafic, ultrabasic, and carbonatite rocks.
Copper occurs in about 250 minerals;'however, only a few of these are commercially important. The
most common sulfide minerals are chalcopyrite (CuFeSj), covellite (CuS), chalcocite (Cu2S), bornite
(CujFeS^, enargite (CujAsS^, and tetrahedrite ((CuFe),2Sb4Si3). Predominant oxide minerals are
chrysocolla (CuSiOa), malachite (Cu2CO3), azurite (Ca^CO^OH)^ and cuprite (Cu2O),
Chalcopyrite is the most common mineral found in porphyry-type deposits. Chalcocite occurs
predominantly in hydrothermal veins (U.S. Geological Survey, 1973).
3.3.4.2 Mining
Conventional open-pit mining techniques are the predominant methods used today by the copper
mining industry, representing 83 percent of domestic mining capacity. In open-pit mining,
overburden is initially stripped off to expose the ore. The waste rock and ore are excavated by
. drilling rows of 6- to 12-inch (diameter) blast holes. Subsequently, large electric or diesel shovels or
front-end loaders transport the ore onto trucks, trains, or conveyor belts for removal to milling or
leaching facilities, depending on the type of ore (sulfide or oxide) and grade.
The remaining 17 percent of the active copper mines use various types of high-tonnage underground
operations. The three main underground mining methods used to mine copper ore are sloping, room- •
and-pillar, and block caving. Waste rock and mine water are generated by underground mining
operations (as well as by surface mines). See Section 34 for a broad discussion of conventional
open-pit and underground mining techniques.
3.3.4.3 Beneficiation
Beneficiation of copper ores and minerals can occur either through conventional milling and flotation
of high-grade sulfide ore or by leaching and solvent extraction/electrowinning (SX/EW) lower grade
sulfide and oxide ore. The beneficiation method(s) selected varies with mining operations and
depends on ore characteristics and economic considerations.
Conventional Milling/flotation
The first step in the beneficiation of high-grade sulfide ore is comminution. Typically, this is
accomplished by sequential size reduction operations—commonly referred to as crushing and grinding.
Crushing and grinding operations at copper mines are typical of those found throughout the mining
industry, including primary crushing in jaw or gyratory crusher (often in the mine workings),
secondary and tertiary crushing in cone crushers (typically in the mill), and grinding in rod and ball
or autogenous/semiautbgenous mills. After grinding, ore is pumped to a classifier designed to
separate fine-grained material fless than 5 mm) from coarse-grained material requiring further
3-71 September 1994
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Overview of Mining and Beneficiation
EIA Guidelines for Mining
111 , 111 lll|ll I 111 111 111 III 111 111 I ' 11)1111 111 111 II II II Hull -I II I 111 I 111
grinding. The hydrocyclone is the standard technology for classification (Office of Technology
Assessment, 1988; Taggart, 1945; Wills, 1981).
iiimm '
1111 ¥'11111111.1! MIHIIOIPI
The second step in the beneficialion of sulfide ore is concentration. Froth flotation is the standard
method of concentration-used in the copper industry for higher-grade ores. About 70 percent of all
copper is produced by this method. The ore is conditioned with chemicals to make the cooper
1"' ;; , " • ;!' ,i ;;| „ , • V . '; • ' '• "• . ' . 1 i. "'' , *,,*!
minerals water-repellent (i.e., hydrophobic) without affecting the other minerals. Air is then pumped
ttopHjghthe a^itate4 slurry to produce a bubbly from. The hydrophobic copper minerals are
aerophillic; that Is, they are attracted to ah* bubbles, to which they attach themselves, and then float to
' of the cell. ^ As they reach the surface, the bubbles form a froth that overflows into a trough
, for collection. The other noncopper minerals sink to the bottom of the .cell. Following copper •
recovery, molybdenum (as" molybdenite" JMoSJ) and other' metals may then be recovered by selective '
i ; ;;„; ;; ;ili| ; • * * • - • » , • *
flotation before the slurry is disposed of as tailings.-
in inn viiiiiiiiii iiiii iiiiii uiiii ii
Conventional flotation is carried out in stages. The purpose of each stage depends on the types of
" minerals in the ore. Selective flotation of chalcocite-bearing sulfide ores and the rejection of pyrite
utilizes three types of flotation cells: roughers, cleaners, and scavengers. Many copper mills now
also include column flotation to further enhance product recovery after scavenger flotation. Reagents
used in flotation concentrators at copper mines include collectors, depressants, activators, frothers,
flocculants, filtering aides, and pH regulators. A list of the reagents typically used hi a copper
flotation circuit is presented in Exhibit 3-10 (Biswas and Davenport, 1976; Bureau of Mines, 1987).
,
•W^
Exhibit 3-10. Copper Flotation Reagents
Collectors
Ethybcantnate
Amylxanthate
Isopropylxanmate
Isobutylxanthate
Unspecified xantbates
Alkyl dithiophosphate
Unspecified dithiophosphate
Xanthogen formate
Thionocarbamate
Unspecified sulfide collector
Fuel oH
Kerosene
Depressants
Phosphorous pentasulfide
Cyanide salt
Sulfide salt
Sodium silicate
Activators
Sodium sulfide or hydrosulfide
pH Regulators
Lime
Sulfuric acid
Caustic soda (NaOH)
Frothers •
Aliphatic alcohol
Pine oil
Phenol
Polyglycol ether
Unspecified polyol
Flocculants
Anionic polyacrylamide
Nonionic polyacrylamide
Polyacrylate
Unspecified polymer
Dispersants
Sodium silicate
Polyphosphate
'
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EIA Guidelines for Mining Overview of Mining and Beneficiation
Copper concentrates exiting the flotation circuit contain 60 to 80 percent water. The concentrate is
dewatered hi a thickener, then sent to disc or drum filters for final dewatering. The dewatered copper
mineral concentrate is then sent to a smelter for processing. The collected water is usually recycled
to the milling circuit. A second product, waste material or tailings, is sent to a tailings pond for
disposal (possibly after additional flotation steps to recover other metal values). The settling of solids
in the thickeners is enhanced by chemical reagents known as flocculants and filter,cake moisture is
regulated by reagents known as filtering agents. Typical flocculants and filtering agents used are
polymers, nonionic surfactants, polyacrylate, and anionic and nonionic polyacrylamides (ASARCO,
1991).
Leach Operations
Copper is increasingly recovered by solution, or hydrometallurgical, methods. These include dump,
heap, and vat leaching techniques, as well as underground (or in situ) leaching methods. Each of
these methods results in a pregnant leach solution (PLS). Copper is recovered from the PLS through
. cementation or, more commonly, by solvent extraction/electrowinning (SX/EW) (U.S. Congress,
Office of Technology Assessment, 1988). Currently, solution copper mining techniques account for
approximately 30 percent of domestic copper production. Two-thirds of all United States copper
mines employ various types of solution operations (Weiss, 1985).
Most ores occur as mineral compounds that are insoluble hi water; leaching involves chemical
reactions that convert copper into a water-soluble form followed by dissolution. Acid leaching of
ores'and concentrates is the most common method of hydrometallurgical extraction. Its use is
confined to acid-soluble, oxide-type ores that are not associated with acid-consuming rock types
containing high concentrations of calcite (such as limestone and dolomite). Typical acidic leaching
agents include hydrochloric acid (HCL), sulfuric acid (HjSO^, and iron sulfate (Fe^SO^). Sulfuric
and hydrochloric acid leaching at atmospheric pressure is the most common type of copper leaching.
For certain minerals, alkaline (or basic) leaching and microbial (or bacterial) leaching are effective
means of extracting copper. The principal reagents used in alkaline leaching are the hydroxides and
carbonates of sodium and ammonia. The organism associated with bacterial leaching is Thiobacillus
ferrooxidans.
Leaching Methods ffn Situ, Dump, Heap, and Vat)
Exhibit 3-11 summarizes the major copper leaching methods. Each of these methods is discussed hi
the following sections.
3-73 September 1994
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1 Orerview of Mining and Beneficiation
EIA Guidelines for Mining
1l\mi
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Ill
Exhibit 3-11. . Characteristics of Copper Leaching Methods
--• "'•''•::^':''f '•;-.].
Ore grade
*»
l^pes of ore .
cure preparation
Container or
pad
Solution
Length of leach.
cycle
Solution ,
application
method
Metal recovery
method
iv^i^ii
Moderate to high
Oxides, silicates,
and* some sulfides
May be crushed to
optimize copper
recovery
Large impervious
vat
Sulfuric. acid for
oxides; acid cure
and acid-ferric cure
jrovide oxidant
needed for mixed
oxide/sulfide ores
Days to months
Spraying, flooding,
and circulation
SX/EW for oxides
and mixed
oxide/sulfide ores;
liuii precipitation
or mixed ores
11^2211^
Moderate to high
Oxides, silicates,
and some sulfides
May be crushed to
optimize copper
recovery
Impervious barrier
•of clay, synthetic
material, or both
Sulfuric acid for
oxides; acid cure
and acid-ferric cure
jrovide oxidant
needed for mixed
oxide/sulfide ores '
Days to months
Spraying or
sprinkling
SX/EW for oxides
and mixed
oxide/sulfide ores;
iron precipitation
or mixed ores
R2£-iSnf^;-
Low
Sulfides, silicates,
and oxides
Blasting
None for existing
dumps; new dumps
intended to be
leached would be
graded, and
covered with an
polyethylene
membrane, or
bedrock, protected
by a layer of select
fiU
Acid ferric-sulfate
solutions with good
air circulation and
bacterial activity
for sulfides
Months to years
Ponding/flooding,
spraying,
sprinkling, and
trickle systems
SX/EW for oxides
and mixed
oxide/sulfide ores;
iron precipitation
or mixed ores
Underground and
/* sitt Leaching
Low to high
(dependent upon
mine conditions
and layout)
Oxides, silicates,
and some
sulfides
None
None
Sulfuric acid,
acid cure, acid-
ferric cure, or
acid ferric-
sulfate,
depending on the
ore type -
Months
Injection holes,
recovery holes,
or sumps '
SX/EW for
oxides and mixed
oxide/sulfide
ores; iron
irecipitation for
mixed ores
Source: Office of Technology Assessment, 1988.
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EIA Guidelines for Mining Overview of Mining and Beneficiation
In Situ Leaching. The leaching of low-grade copper ore without its removal from the ground is
known as in situ leaching. In situ leaching allows only limited control of the solution compared to
other types of leaching (see below). There are 18 in situ copper operations in the United States that
leach ore in existing underground mines.
In situ leaching extracts copper from subsurface ore deposits without excavation. Typically, the
interstitial porosity and permeability of the rock are important factors hi the circulation system. The
solutions are injected in wells and recovered by a nearby pump/production-well system. In some
cases (where the ore body's interstitial porosity is low), the ore may be prepared for leaching (i.e.,
broken up) by blasting or hydraulic fracturing. Production wells (and/or sumps in underground
mines) capture and pump pregnant lixiviant.solution from the formation to the leach plant where
copper metal is recovered by an SX/EW operation (Biswas and Davenport, 1976; EPA, 1984a- EPA
1989).
Dump Leach Operations. Dump leaching refers to leaching of low-grade sulfide or mixed-grade
sulfide and oxide rock that takes place on (usually) an unlined surface. Copper dump leaches are
typically massive, with rock piles ranging hi size from 20 to hundreds of feet in height. These may
cover hundreds of acres and contain millions of tons of waste rock and low-grade ore (Biswas and
Davenport, 1976). These operations entail the addition of low pH solution to the piles to accelerate
leaching, the collection of PLS, and the extraction of copper by SX/EW or cementation. Since
widespread application of leaching process is a relatively new process, copper mines have frequently
applied leaching techniques to recover values from historic waste rock dumps. Collection of PLS
may not be maximized (i.e., some PLS may escape to the environment). The sites for these historic
dump leaches were selected primarily to minimize haulage distances. New dump leach units are
typically located and designed to prevent or minnni7f! the loss of leach solution (EPA, 1989).
The materials placed hi dump leaches vary considerably hi particle size, .from large angular blocks of
hard rock to highly weathered fine-grained soils. The material is typically less than 0.6 meter in
diameter. In most dump leach operations, the material is hauled to the top of the dump by trucks.
The material is deposited by end-dumping hi lifts on top of materials that have already been leached.
Large dumps are usually raised in lifts of 15 to 30 meters. After the lift is completed, the top layer is
scarified (by a bulldozer and a ripper) to facilitate infiltration of the leach solution (EPA, 1989e).
Natural precipitation, mine water, raffinate (from the SX/EW plant), makeup water, and/or dilute
sulfuric acid may be used as leach solution (i.e., lixiviant). As the lixiviant infiltrates the pile, copper
minerals are leached by oxidizing the pyrite to form sulfuric acid and ferrous iron solution (the
sulfuric acid solution reacts with the ore minerals to ionize the copper into solution). Several methods
are used to distribute leach solutions over the dumps, including natural precipitation, sprinkler
systems that spray the leach solution over the piles, flooding of infiltration ditches or construction of
3-75 September 1994
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of Mining and Benefication EIA Guidelines for Mining
Son of leach solutions through perforated pipes on top
), and the injection of leach solutions through drill holes into
dumps. 'The leach solution percolates through the dump and PLS is collected in ditches or sumps at
the toe of the dump where the slope of the native terrain provides the means for collection of
pregnant liquor. These ditches and sumps are lined at some sites, and are unlfned at others. PLS is
then treated by solvent extraction or cementation. Metals associated with the copper minerals that are
also found in PLS include arsenic, cadmium, chromium, and selenium (EPA, 1985; EPA, 1984a).
Heap.Leaching. In contrast to dump leaching (described above), heap leaching refers to the leaching
"I" »'l "I "III of Ipw-grade ore that has been deposited on a specially prepared, lined pad constructed using
synthetic material, asphalt, or compacted clay. In heap leaching, the ore is frequently beneficiated by
some type of size TCJu^ff,,1^ to placement onthe pad (EPA, 1989).
•
Illilfl iiilHii1 Heapleach pads are constructed above one or more layers of impermeable liner material. Liners can
leach sites are selected to take advantage of existing, less permeable surfaces and to utilize the natural
slope of ridges and ...... valleys for the collection of PLS. Land jst&ftit.'gpe ...... ofgedqgy 'and ..... .......................... - ......
however, is not always within a reasonable hauling distance of the mining operation.
basic principles and procedures discussed above with regard to dump leaching operations
apply to heap leach operations. Heap leach operations, as opposed to dump leach operations, have
]££!£* ...... EPJSS!!!!!0"?, generally are used; (2). leach piles
may be neutralized after leaching operations are completed;. (3) the leach pad design is substantially
:"-d!?!55en£ &e.f the size is smaller, averaging between 100,000 and 500,000 metric tons afore); (4) the
S8! "" °"S' *f f061" ^ained (i-e., usually less than 10 cm); (5) the leaching is considerably fester; and (6) the
~^~~~ extraction of oxide copjper is greater (EPA, 1989e). • '.
y.at,Leaching. The vat leaching process works on the same principles as the dump and heap leaching
i i i || I, .- = ± ; - __---— ---- ===~I -==JMcted in a system of
vats or tanks using concentrated lixiviant solutions. Vat leacbing is typically used to extract copper
from oxide ores by exposing crushed ore to concentrated sulfuric acid (lixiviant) in a series of large
,, I'^^i'0* 2S J1* vats are usually designed hi a series configuration, which acts to concentrate the
| cofJpef coSent of the sohitions as a function of ore-lixiviant contact time (EPA, 1989e). A typical
|p25-mpter-Iongy 15-meter-wide, and 6-meter-deep vat unit is capable of leaching between 3,000 and
5,000 tons of ore per cycle.
i
i I
, Vat and agitation (tank) leaching are usually performed on relatively higher grade oxidized ores.
Tank methods tend to recover copper more rapidly using shorter leach cycle times than heap or dump
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EIA Guidelines for Mining • Overview of Mining and Beneficiation
leaching operations. Generally, copper recovery is higher, and solution losses are lower with tank
methods (EPA, 1984). The.advantages of this method are high copper extraction rates and
recoveries, short leach cycles, and negligible solution losses (EPA, 1989e). The disadvantages are
the low tonnages beneficiated, high suspended solids concentrations in PLS that a cause problems in a
SX/EW plant, and high operating costs.
Copper Recovery from Leach Solutions—Cementation and SX/EW
Cementation. In the past, copper produced from leach solutions was typically recovered by
cementation techniques. In the cementation process, pregnant leach solution (PLS) flows to a
precipitator pond filled with scrap iron or steel. The copper chemically reacts with, and precipitates
onto the steel surfaces. The iron is dissolved into solution, and the copper precipitates out (i.e.,
replaces) the iron. The cemented copper later detaches from the steel surfaces as flakes or powder
when it is washed with high-pressure streams of water. Although subsequent treatment by a normal
smelting/refining method is required, copper recovery from the pregnant solution is very high.
While cementation has been a source of relatively inexpensive copper, the cement copper produced is
relatively impure compared to electrowon copper and must be smelted and refined along with flotation
concentrates (Beard, 1990). As a result, it has largely been replaced by SX/EW technology.
However, several compact and dynamic cementation systems have been developed and are used
industrially. The most successful is the Kennecott Cone System Precipitator, by which the PLS is
forced upwards in a swirling motion through shredded steel scrap. In this system, fine, undissolved
solid particles (called pulp) are concentrated with the copper cemented particles. Consequently, the
cement concentrates containing the pulp must be further beneficiated by flotation. The cemented
copper is easily floated with xanthate or dixanthogen collectors (Biswas and Davenport, 1976).
Solvent Extraction. The first SX/EW plant was developed during the 1960s at the Bluebird property
near Miami, Arizona. Historically, solvent extraction was largely confined to copper oxides.
However, recent refinements in leaching methods have, made it economical for recovery from low
grade sulfide ores. The major advantage of solvent extraction (over cementation) is that the electrolyte
solution it produces is almost free of impurities.
Exhibit 3-12 provides a flow diagram for a typical SX/EW plant. The solvent extraction operation is
a two-stage method. In the first stage, low-grade, impure leach solutions containing copper, iron, and
other base-metal ions are fed to the extraction stage mixer-settler. In the mixer, the aqueous solution
is contacted with an active organic extractant (chelating agent) in an organic diluent (usually
kerosene), forming a copper-organic complex. The organic phase extractant is formulated to extract
only the desired metal ion (i.e., copper),'while impurities such as iron or molybdenum are left behind
in the aqueous phase. The barren aqueous solution, called raffinate, is typically recirculated back to
the leaching units. The loaded organic solution is transferred from the extraction section to the
3-77 September 1994
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Overview of Mining and Benefidation
EIA Guidelines for Mining
I
(Hill III 111
Exhibit 3-12. Typical Solvent Extraction/EIectrowinning (SX/EW) Plant
-------
. ETA Guidelines for Mining Overview of Mining and Beneficiation
stripping section. The aqueous-organic dispersion is physically separated in a settler stage (Office of
Technology Assessment, 1988; EPA, 1984; Engineering and Mining Journal, 1990).
In the second stage, the loaded organic solution is stripped with concentrated sulfuric acid solution
(spent tankhouse electrolyte) to produce a clean,, high-grade solution of copper for electfowinning.
The stripping section can have one or more mixer-settler stages. The loaded-organic phase is mixed
with the highly acidic electrolyte, which strips the copper ions from the organic phase. Then, the
mixture is allowed to separate in settling tanks, where the barren organic solution can be recycled to
the extraction stage. The copper-enriched, strong electrolyte flows from the stripping stages to the
strong-electrolyte tanks, where it is pumped to the electrolyte filters for removal of the entrained
organics or solids. The clarified, strong electrolyte flows to electrolyte circulation tanks, where it
becomes the influent to the electrowinning tankhouse (Office of Technology Assessment, 1988; EPA,
1984a; Engineering and Mining Journal, 1990).
*
Electrowinning. Electrowinning is the method used to recover copper from the electrolyte solution
produced by solvent extraction. To stabilize the tankhouse operating temperature and preheat the
incoming electrolyte solution, strong electrolyte (after filtration) is passed through heat exchangers
where heat is extracted from outgoing, wanner, spent electrolyte. After passing through starting-
sheet cells, the strong electrolyte is received in a circulation tank. In the circulation tank, the strong
electrolyte is mixed with spent electrolyte returning from the electrowinning cells. The feed
electrolyte is then pumped to the electrolytic cells continuously. The electrochemical reaction at the
lead-based anodes produces oxygen gas.and sulmric acid by electrolysis. Copper is plated on
cathodes of stainless steel or on thin-copper starting sheets. The cathode copper is then shipped to a
rod mill for fabrication. Tie spent acid is recycled and pumped back to the leaching operation, while
some of the electrolyte is pumped to the solvent extraction strip-mixer-settlers via the electrolyte heat
exchangers (Office of Technology Assessment, 1988; Engineering and Mining Journal, 1990).
Over time, electrolyte hi the electrowinning cells becomes laden with soluble impurities and copper.
When this occurs, the solution is removed and replaced with pure electrolyte (to maim^n the
efficiency of the solution and prevent coprecipitation of the impurities at the cathode). Purification is
done by electrowinning in liberator cells. Liberator cells are similar to normal electrolytic cells, but
they have lead anodes in place of copper anodes. The electrolyte is cascaded through the liberator
cells, and an electric current is applied. Copper hi the solution is deposited on copper starting sheets.
As the copper in the solution is depleted, the quality of the copper deposit is degraded. Liberator
cathodes containing impurities (such as antimony) are often sent to the smelter to be melted and cast
into anodes. Purified electrolyte is recycled to the electrolytic cells.
3-79 September 1994
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Illllllllllllllllllllllllllll (11111
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Overview of Mining and Beneficiation EIA Guidelines for Mining
" • J
33.4.4 Wastes and Waste Management
1 • ' , f : :
. • ' " " t'' V '.' I ' ' ' • : .
Wastes generated by copper mining and beneficiation operations include materials such as waste rock,
mine water, spent ore, tailings, SX/EW sludges, and spent leaching solution. Many of these materials
If IIIIIIJI I] | I'll . IIHWIII^IMBIHI . I I I!!! I II I .
may be disposed of onsite or offsite, and others may be re-used or recycled during die active life of a
i||||| ^Ufi . • a ,
11111,111111 mine. Waste constituents may include heavy metals, sulfides, or other elements found in the ore, acid
mine drainage (AMD), and any additives used hi beneficiation operations. (It should be noted that
the use of the terms "mining waste" and "waste management unit" hi this document does not imply
that the materials in questions are "solid wastes" within the meaning of the Resource Conservation
and Recovery Act. As indicated previously, the term "wastes" includes both RCRA wastes as well as
other materials.)
::::;:::::: :::::: Mine water '
Mine water consists of all water that collects in siirface and underground mine workings as a result of
imlow^from surface 'ijjrateri ^^p^g^ _. ^^^^ ^^ „_. __
pumped out to keep the mine relatively dry and to allow access to the ore body. At surface copper
mines, name water may be pumped or allowed to dram to centralized sumps. At underground mines,
the quantity of water entering the mine depends on local hydrogeologic conditions. At some
facilities,, little or no water is .encountered. At others, groundwater may continually drain into the
mine; workings. Underground water inflows are often allowed to dram to low areas of the mine
^\|b^:;|mngs and gumgs collect andjjump the water from the.inine. At some facilities,, however,' the,
inflow of water is so great that the capacities of the underground holding and pump mechanisms are
JTOiiMrjjjjIjj? jg£ 5^3 Jo" pimp groundwater, leading to a cone 5 depression around the mine and reducing
RJ&gSfrflfliS , . . i;9
The quantity of mine water generated at mines varies from she to she. The chemistry of mine water
Isdependent on the geochemistry of the ore body and the surrounding area. Water exposed to sulfur-
bearing minerals in an oxidizing environment, such as an open pit or underground workings, may
become acidified. This potential is greatly dependent on site-specific factors (see Section 4.1).
i ' •
Pumped water from copper mines may be used hi extraction and beneficiation activities (including
dust control), pumped to tailings ponds, or discharged. Because mine water at copper mines is often
rich m dissolved copper and other metal ions, some operations pump it to an SX/EW plant to recover
the copper values (Gimming, 1973).
i I ' MI
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Waste rock is typically hauled from the mine to onsite waste dumps for disposal. At some surface
mines, these dumps are located within the pits. Waste rock piles may be highly permeable to both air
i i
3-80 September 1994
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, , M ! '
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EIA Guidelines for Mining Overview of Mining and Beneficiation
and water. Sulfur-bearing minerals in waste rock, such as pyrite and pyrrhotite, can oxidize to form
sulfuric acid. Factors that influence acid generation by sulfide wastes include: (1) the amount and
frequency of precipitation, (2) the design of the disposal unit, and (3) the neutralization potential of
the rock. Even where acid-generating conditions are not present, metals found in the waste rock may
dissolve in infiltration runoff or runon. This low pH solution can dissolve and mobilize metals in the
rock matrix and be transported to ground or surface water. Waste rock disposal units are generally
constructed without liners. Because even waste rock would contain low concentrations of copper,
some operations refer to waste rock as. "low-grade ore" or "subore."
Spent Ore . .
Spent ore from heap and dump leaching contains residual amounts of lixiviant and associated copper
and other metal complexes. The spent ore itself typically contains unleached metals and other
minerals characteristic of the ore body. Dump leack piles are reported to range in size from 20 feet
to hundreds of feet in height and may cover hundreds of acres and contain millions of tons of waste
rock and low-grade ore. Most copper leaching operations are not constructed with synthetic liners
(i.e., they are dump leach units, rather than heap leach units). However, newer units are frequently
shed where natural low permeability features allow for drainage to a centralized collection point (to
facilitate recovery of pregnant leach solution). After collection of leaching solution no longer
becomes economically viable, operators must address reclamation/closure of the leach units and
management of drainage.
Tailings
In 1985, 195 million tons of copper and copper-molybdenum ores were treated by flotation
concentration, resulting in the production of 5.8 million tons of concentrate using 97 million gallons
of water and 0.32 million tons of reagents. More than 97 percent (189 million tons) of ore tonnage
processed hi 1985 was typically disposed of as tailings (Bureau of Mines, 1987).
Tailings impoundments are surface disposal units for tailings generated during flotation. Slurried
tailings are transported from the mill to the tailings pond by gravity flow and/or pumping through
open conduits or pipes. In the arid southwest, where the majority of copper mines are located and
evaporation rates exceed precipitation, the mine-mill water balance usually requires recycling tailings
pond water for reuse in the mill. At copper mines in the central United States (such as the White
Pine hi Michigan) the reverse situation exists; precipitation exceeds evaporation rates and tailings
pond water is typically discharged to surface water. Tailings impoundments may also be used to
disposed of other smaller-volume wastes generated at copper mines including, spent electrolyte
solution, SX/EW tank sludge, etc.
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of Mining and Beneficiation • EIA Guidelines for Mining
Upstream tailings impoundments are most commonly used in the copper mining industry. In this
method (as described in Section 3.2), the embankment is erected by depositing successive layers of
course material on top of the previous dike along the inside of its embankments. Thus, the centerline
of the berm progresses upstream toward the center of the Ham while the outer slope remains stable
(Bureau of Mines, 1984).
1 ''''," . ' •
Sohkfoa Bands g?£.2!l£ E-fS,"-!- If??.*^, ',
;.T .retailing operation ponds can be a source of acid/metal releases by ground and surface water. These
S include: pregnant solution ponds or tanks (where the copper-laden solution is collected), barren •
solujios ponds (where lixiviant solution is held before being applied), surge ponds (to manage
•I Illll IIP Illllllll I" III I III IIIIIPl 11 I 111'' III I lllllllllllllllllllllllllii'ilillllllliiiiiin inn |ii|i|iiiii nil iiiii| »iii| 1 i in 11 nil n n in i i 11 n in 11 qiini i n in nil IIIIIIMI mill* j filii Si gnu in Si ' 11
leachate during high precipitation events), make-up water holding ponds, and associated pipes or
i i i i *i I f
trendies. These units may be lined, depending on the quality of the solution to be contained,
applicable regulatory requirements, the age of the unit, and permeability of the underlying formation.
, , . PLS and raffinate ponds generally measure several hectares hi size and, where the topography
; ', i permits, are built into natural drainage basins. At most older. copper leaching operations, the
collection ponds and trenches through which the solutions flow are unlined. In addition, these areas
.ilillli
received little or no surface preparation before leaching operations were initiated (EPA, 1989). At
newer leaching operations, 'liners have been installed in the collection ponds 'to increase solution
M; recovery and rnjnmiiTe environmental releases. Generally, the trenches-have been lined with
!«^^ total quantity of usable iron ore product snipped from mines in 1991 was estimated to be ,52.8
= ' • ' + million long tons (ft),1 valued ^ $1/7 billion. Of the total 1991 domestic production, 1.97 million It
==•5=!™ of m» product (4 percent) were exported. 'The United States also imported 12.9 million It of usable
i Ispja^sg in, lgf>l i|srii,bsnefisiatio.n and processing. According to the Bureau of Mines, "usable" iron
ZZ^:™".^0??. IP?!*65 mat I*55 tnan 5 percent of the material is made up of manganese (Bureau of Mines,
opeiating ron ore mines (21 open pt; 1 underground '
ofieriftioiift, 16 TOnceniration plants, and' 10 pelletizing plants.- The primary iron ore producers are
in Minnesota .and, Michigan, ...... wMcji account ...... for ..... about ...... 99 percent of all domestic crude iron
tends to measure iron ore production in long tons (It), while the Bureau of Mines used short tons (st) before
w*s metrictons (n§). Production data are presented here in long tons (1 long ton is equivalent to 2,240 Ibs).
IM^ _ ,——,— ;™^E5Sanber 1!W4
III llfji; < llili,1 Unilliii !l!ii''I!" niilnili 11 HiUdi1'1! XI'Uill1"!!,: JilBiiJIii,' " *iH .III! ,<|i"! v P'l'ii' niimn1111!!1!,,, lilPIIB" ll n' i'!i I!: '' iPniHji!!; innil!1 ,'''. f -, 'iilV'lK;"' inllliliiiiiill "if
-------
EIA Guidelines for Mining Overview of Mining and Beneficiation
edacity mills. Operation capacities tend to be in the range of 1 to 10 million long tons of product
per year (Itpy). A few mines, however, produce less than 100,000 Itpy (Weiss, 1985).
Nearly 98 percent of the demand for iron ore comes from the steel manufacturing industry. Iron is
also a component in the manufacture of cement and heavy-media materials. Among the 22 mines
producing iron ore, most larger operations produce material for the steel manufacturers. Mines
producing for cement plants tend to be smaller operations located outside Michigan and Minnesota
(Bureau of Mines, 1988b,1991a, and 1992).
3.3.5.1 Geology of Iron Ores
Iron is an abundant element in the earth's crust averaging from 2 to 3 percent in sedimentary rocks to
8.5 percent in basalt and gabbro. Because iron is present in many areas, it is of relatively low value
and thus a deposit must have a high percentage of metal to be considered ore grade. Typically, a
deposit must contain at least 25 percent iron to be considered economically recoverable. This
.percentage can be lower, however, if the ore exists in a large deposit and can be concentrated and
transported inexpensively (Weiss, 1985). Over 300 minerals contain iron but five are the primary
sources of iron-ore minerals: magnetite (FejO^, hematite (FeA), goethite (Fe^^O), siderite
(FeCp3), and pyrite (FeS^. The first three are of major importance -because of their occurrence in
large economically minable deposits (U.S. Geological Survey, 1973).
Iron ore mineral deposits are widely dispersed in the continental United States and form in a wide
variety of geologic environments, including sedimentary, metamorphic, and igneous rock formations.
Iron ore deposits hi the United States arc formed by three geologic processes:
• Direct sedimentation forming bedded sedimentary deposits
• Igneous activity forming segregation or replacement deposits
• Enrichment due to surface and near surface weathering (EPA, 1985).
Historically, most iron ore was simply crushed and shipped directly to a blast furnace. Currently,
some ores are high enough in iron content (greater than 50 percent) to be sent directly to furnaces
without beneficiation activities other than crushing and washing. Most ores extracted today, however,
must undergo a number of beneficiation procedures to upgrade the iron content and prepare the
concentrate for the blast furnace. .Technological advancements at blast furnace operations require ore
feed of a specific size, structure, and chemical make-up for optimum efficiency (Weiss, 1985).
3.3.5.2 Mining
Iron ore is mined almost exclusively in surface operations. The most predominant surface mining
methods used to extract iron ore are conventional open-pit and open-cut methods. However, there is
3-83 September 1994
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Overview of Mining and Beneficiation
EIA Guidelines for Mining
r,
llliHllllillllilll'IS'llllllili:!1!11!!1
currently one operating underground iron mine, located hi Missouri (five were hi operation in
i in 1985). The mining of taconite, a tough and abrasive low-grade ore (ranging from 40 to
. i Si i | Si i i e * - —
int silica and 17 to 30 percent iron) common to Mi
60 percent;
sota and Michigan, is especially
difficult because of the extreme hardness of the ore but now dominates U.S. iron production.
[ ln|i j, , ,,, j ,,; [( ,_,, „ ; , , , > |/ ; ;;; j*; ^ ,,; 5, , , , , ,
In the iron industry, stripping ratios (overburden/ore) may be as high as 7:1 (for high-grade wash
ores) or as low as 0.5:1 (for low-grade taconite ores) (united States Steel, 1973). Wastes generated
as a result of open-pit and underground iron mining include overburden, waste rock, and mine water
confining stispended solids and dissolved materials.
•I11 • ill
33.5.3 Beneficlation
' ^
Beneficiation at iron, mines pan include the following: milling (crushing and grinding); washing; '
"" filtration; sorting; sizing; gravity concentration; magnetic separation; flotation; and agglomeration
(pelletizing, sintering, briquettmg, or nodulizing).. The American Iron Ore Association indicates that
milling and magnetic separation are the most common methods used. Gravity concentration is seldom
" .used at existing U.S. facilities. Flotation is primarily used to .upgrade concentrates from magnetic
separation by reducing the silica content of the concentrate (Ryan, 1991). Most beneficiation
operations will result in the production of three materials: concentrate; middling or very low-grade
concentrate, which is either reprocessed (in modern plants) or stockpiled; and tailings.
"Mflling " • "
Milling operations are designed to produce uniform size particles by crushing, grinding, and wet or
dry classification. Primary crushing is accomplished by using gyratory and cone crushers (Weiss,
1985). Primary crushing yields chunks of ore ranging hi size from 6 to 10 inches. Secondary
mm "" B milling (conminution) farther J^g^ pUftjcie' size~ JQ"""^^: J~ g^ '| -Jj£jj |j^™ ^ rj——
(11111 ii 11
Secondary crushing, if necessary and economical, is accomplished by. using standard cone crushers
followed by short head cone crushers. Gyratory crushers may also be used.
Subsequent fine grinding
to e consistency of fine powder (325
...... nss, ....... 0.44 ..... microns). .............. hough ..... miM taconite ..... operations employ rod and/or ml
, a few facilities use autogenous or semi-autogenous grinding systems. Autogenous grinding
uses coarse pieces of the ore itself as the grinding media in the mill. Semi-autogenous operations use
metallic balls and/or rods to supplement the grinding action of the ore pieces (Weiss, 1985). Between
grinding unit, hydrocyclones are used to classify coarse and fine particles. Coarse particles are
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ElA Guidelines for Mining Overview of Mining and Benefication
Magnetic Separation
Magnetic separation is most commonly used to separate natural magnetic iron ore (magnetite) from a
variety of less-magnetic or nonmagnetic material. Today, magnetic separation techniques are used to
beneficiate over 90 percent of all domestic iron ore (Ryan, 1991). Magnetic separation may be
conducted in either a dry or wet environment, although wet systems are more common. Magnetic
separation operations can also be categorized as either low or high intensity. Low intensity wet
processes typically involve conveyors and rotary drum separators using permanent magnets and are
primarily used on ore particles 3/8 inch in diameter or less. Low intensity separators use magnetic
fields between 1,000 and 3,000 gauss. High intensity wet separators produce high magnetic field
gradients by using a matrix of shaped iron pieces that act as collection sites for paramagnetic
particles. High intensity separators employ fields as strong as. 20,000 gauss. (Weiss, 1985; United
States Steel, 1973). Primary wastes from magnetic separation include: tailings made up of gangue in
the form of coarse- and fine-grained particles, and wastewater slurry hi the case of wet separation.
Particulate wastes from dry separation may also be slurried..
Flotation
Conventional flotation is primarily used to upgrade concentrates resulting from magnetic separation.
Over 50 percent of all domestic iron ore is upgraded using this technique. Rotation, when used alone
as a beneficiation method, accounts for approximately 6 percent of all ore treated (Ryan, 1991).
Typically, 10 to 14 flotation cells are arranged in a series from roughers to scavengers. Roughers are
used to make a coarse separation of iron-bearing metallic minerals (values) from the gangue.
Scavengers recover smaller quantities of remaining values from the pulp. The pulp moves from the
rougher cells to the scavengers as values are removed. Concentrates recovered from the froth in the
roughing and scavenging cells are sent to cleaning cells to produce the final iron-bearing metallic
mineral concentrate (Fuerstenau, 1970). Flotation reagents of three main groups may be used:
collectors/amines, frothers, and antifoams.
Iron-bearing metallic mineral flotation operations are of two main types: anionic and cationic
(although anionic flotation is not commonly used in North American operations). The difference
between the two methods is related to which material (values or gangue) is floated and which sinks.
In anionic flotation, fine-sized crystalline iron oxides, such as hematite or siderite, are floated away
from siliceous gangue material such as quartz or chert. In cationic flotation, the silica material is
floated and the value-bearing minerals are removed as underflow (Nummela and Iwasaki, 1986).
Wastes from the flotation cell are collected from the tailings overflow weir. Depending on the grade
of the froth, it is recycled for further recovery of iron units or discharged as tails. Tailings contain
remaining gangue, unrecovered iron minerals, chemical reagents, and process waste water.
3-85 September 1994
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. '
liillil lilt"!
is iin^
EIA Guidelines for Mining
ll II 'Ill III
'lllll^^
, nuiniii I iiiv|i! 11,,!1 •& . • ' ih, „
Generally, tailings proceed to a thickener. Thickened tailings may be pumped to an impoundment or
'p3^ *>* recycled for further beneficlation to collect remaining values. Clarified water is often reused
in the milling process.
Gravity Concentration
Although gravity concentration was once widely used in the beneficiation of iron ores, today less than
one percent of total domestic iron ore is beneficiated using this method. Gravity concentration is used
to suspend and transport lighter gangue (nonmetallic or nonvaluable rock) away from the heavier
valuable mineral. Three gravity separation methods have historically been used for iron ore:
. washers, jigs, and heavy-media separators (Weiss, 1985). Wastes from gravity concentration are
tailings made up of gangue in the form of coarse- and fine-grained particles and process water. This
material is pumped as a slurry to a tailings pond.
Agglomeration
I iiii'1 'Ilili 'Ili'iFil'' iililllJUK , |l| II
i
IK inii illillK^ II iiiiililliii.!*'lll«^ i l i inn h iiiiiini i i iiiiiiiiiiiiniiiiii in i in i 1 i i i
activities, agglomeration is used to combine the resulting fine concentrates into
durable clusters. The iron concentrate is balled in drums and heated to create a hardened
A^omerates may be in the form of pellets, sinter, briquettes, or nodules. The
purpose of agglomerating iron ore is to improve the permeability of blast furnace feed leading to
Jas-ioIId contact in {he furnace (Weiss, 1985). Pellets currently account for more than 97
of all agglomeration products ^erefbre, only the pelletizing technique is discussed below,
,,^ olEer ?gg|°mer3tes are pj^^j ^y gj.^^ high-temperature operations).
' " ' ' ' '
iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii?iiiiiiiiiiiiiiiiiiiiiiiiiiii •
operations produce a "green" (moist and unfired) pellet or ball, which is then hardened
...... eoaoeaMUfSSbS ...... the'"
...... ..... ....... .......
pellets. This is usually accomplished hi a series of balling drums or discs. Additives such as
limestone or dolomite may also be added to the concentrate in a process known as "fluxing," prior to
balling to improve blast furnace recovery. One of three different systems can then be used to produce
hardened pellets: ' ' •
l|llllllllllllllllllllllll|l|ll Illllllllllllllllllllll ^ 111 III 111 III 1111 II III II II 111 I III 111111 111 I 111 111 III III I 111 I lllllllll||ll II 111 111 III I II IIIIIIIIIIIIIIIIIIIIB 11111
• Travelling-Grate. Used to produce pellets from magnetite concentrates obtained from
tacolite ores. Green pellets are fed to a travelling grate, dried, and preheated. The pellets
then proceed to the ignition section of the grate where nearly all the magnetite is oxidized to
hematite. An updraft of air is then used to cool the pellets.
Shaft-Furnace. Green pellets are distributed across the top of a furnace by a moving
conveyor belt and pass vertically down the length of the furnace. In the furnace, the pellets
are dried and hejjg| to 2400°F. The bottom 2/3 ofjhg fjirjasg |§ used to cool the.pellets
using an upward-rising air stream. The pellets are Jj^j^g^J gQm ^je j^gg^ Of me
system through a chunkbreaker.
i
i ill ill in 11 in 111 illllllll il '! ll i* l iii in ill i ill ill i llllllll|i 1111!' i|i|jjiiilii ll | ll iiiill ill illllijil | il 1111 i'| ill 3-86
n iii 11 in iiiii i n 11111 ^mii 11 iiiiiii iiiiM in iiiii^ '
, - , , :.., : ,,;,,;,: ,, ', .;.••. , ,• • s.
1994
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EIA Guidelines for Alining Overview of Mining and Beneflciatfon
• Grate-Kiln. Combines the grate technique with a rotary kiln. No fuel material is
incorporated into or applied to the pellets in this process. The pellets are dried and
preheated on a travelling grate before being hardened by high-temperature heating in the
kiln. The heated gas discharge from the kiln is recycled for drying and preheating (United
States Steel, 1973).
Agglomeration generates byproducts in the form of particulates and gases, including compounds such
as carbon dioxide, sulfur compounds, chlorides, and fluorides that are driven off during the
production process. These wastes are usually treated using cyclones, electrostatic precipitators (wet
and dry), and/or scrubbing equipment. These treatment technologies generate either a wet or a dry
effluent, which contains valuable iron units and is commonly recycled back into the operation.
3.3.5.4 Wastes and Waste Management
Overburden, Mine Development Rock, and Ore Piles
.Overburden and mine development rock removed from iron mines are stored or disposed of in
unlined piles onsite. These piles may also be referred to as "mine rock dumps" or "mine dumps."
As appropriate, topsoil may be segregated from overburden and mine development rock, and stored
for later use in reclamation and revegetation. These dumps are generally unsaturated and provide a
prime environment for acid generation if sulfide minerals are present. However, in Minnesota and
Michigan, where most crude iron ore is produced, sulfide-bearing minerals are present in only one
unique geologic environment (Guilbert, 1986). As a result, acid generation has only been observed at
one site, LTV's Dunka ske at the eastern edge of the Mesabi Range (see below).
Mine Pits and Underground Workings
In addition to wastes generated during active operations, pits and underground workings may be
allowed to fill with water when the mine closes or stops operation, since the need for dewatering is
over. At one site in Minnesota, the Dunka Mine, accumulated water, or mine drainage, has acidified
through contact with sulfide minerals in an oxidizing environment and become contaminated with
heavy metals, as well as suspended solids. However, the conditions at the Dunka site (as well as two
other abandoned iron mines with similar acid rock drainage) are generally considered unique in the
iron industry (because of localized sources of sulfide ore). Overall, mine water associated with iron
operations is characterized by low pollutant levels. In fact, the'mine water from at least one mine in
Michigan is used to supplement the local drinking water supply.
At abandoned underground mines, deficiencies in mine shaft protection and mine subsidence may be a
problem. Although there is only one underground iron mine currently operating in the United States,
abandoned underground iron mines have contributed to the creation of subsidence features. In West
Iron County, Michigan, subsidence features caused by abandoned Iron mines have grown into large
3_g7 September 1994
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•lilllii • iflillljlll'l lllllll Il!llllllllii, lll'
Overview of Mining and Benefication EIA .Guidelines for Mining
I1 • , '' |,
pits and caused interruptions in utility service, damage to roadways, and loss of life (Michigan State,
Geological Survey Division, 1983).
Tailings Impoundments
H . , . I II
Impoundments, rather than piles, are used exclusively for tailings management in the iron ore
industry. As a typical example, the tailings impoundment at LTV Steel Mining Company's facility at
, I i • I
Hoyt Lakes is approximately 3,000 acres and contains about 500 million tons of tailings (LTV Steel
i i 111 i ii i i i ii i
Mining Company,' 1991). Two general classes of impounding structures may be used to construct
tailings pond at iron mines: water-retention dams and raised embankments. As solids settle out in
,4 , !' 'I f , 'I , " • • " ,i in , ', I ' " 'i. , ,',"'" I! !, , , , '" P'
eimer of these type of impoundments, water is either recycled to the mill or discharged.
' ! !'""[ "" ; !'"
Trace amounts of several toxic metals are found in raw mill tailings effluents. These metals include
antimony, arsenic, beryllium, cadmium, chromium, copper, lead, nickel, selenium, silver, and zinc.
In some instances (Silver Bay, Minnesota and Groveland Mine, Michigan), amphibole minerals with
! " I ] ' !"' ! . , i .' ' - •• i-, '!"•" , 't i-,:1 • j>... -i, . i,..
fibrous characteristics may be a constituent in the tailings. While amphibole minerals (cummington-
* |l i | t
grunerite) are present in some Eastern Mesabi Range taconite formations, asbestos has not been
identified as such (EPA, 1976). Most of these contaminants are effectively removed or reduced by
" in tailings impoundments.
33.6 URANIUM
| Uranium is extracted using ....... surface, underground and solution mining (in situ) techniques. Although
" relativel young" ...... develc jp ing in the 1940s, the volume of ore recovered by U.S. mines
has dropped significantly since peaking in the early 1980s. Low commodity prices, a reduced
„,„ demand ...... from the ...... military and commercial power generators; and abundant foreign supplies are
responsible for the depressed market.
33.6.1 Geology of Uranium Ores
Elemental uranium is generally found in naturally occurring minerals in one of two ionic states: U*+
"oxidized" ion) and U4* (the uranous "reduced" ion). * Common uranyl minerals include
(CXUO^jVaOg'SHjO), autunite (Ca(UO2)2(PO4)2'8-12H2O), torbemite
JQz)2(PO4)2-8-12H2O) and uranophane (HaO^CadJO^SiO^-3H2O) (Smith, 1984; Hutchinson
i~H and Blackwdl, 1984). Common uranous rninerals include uraninite (UO^), pitchblende (a crystalline
:^^ variant of uraninite) and coffinite gJSiO*) (Smith," 1984; Hutehinson and' Blackwell, 1984). Uranium
occurs in the rninerals as one of three isotopes: U-234, U-235 and the most abundant of the isotopes,
U-238 (Tatsch, 1976).^ In the uraniuni market, references to OTeL intermediate, and some final
products, are in terms of percent of uranium oxide or uranium oxide equivalent. Uranium oxide is a
generic term for a number of common chemical forms of .uranium, the most common being U3O8.
YeUpweake is another generic term, used to describe the yellow powder generated as the end product
i ill (i ii i i iiii iiiii ii I ii11 ' 111 iiiiiiii I IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIH ii iiiiiii i ' i iii (i i IIIIIIB in ii ill ii i in in i
» h
3-88 September 1994
iii
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EIA Guidelines for Mining • Overview of Mining and BeneSdatioa
of uranium beneficiation. The purity of yellowcake typically ranges from 60 to 75 percent U3Og
(Merritt, 1971).
3.3.6.2 Mining
Economically recoverable uranium deposits in the United States historically fit into one of four types
of deposits: stratabound, solution breccia pipes, vein, and phosphatic. The most economically
important deposits occur within stratabound deposits within the Wyoming Basin, south Texas, and the
Colorado Plateau. Stratabound deposits have been mined using surface and underground techniques
and are currently the target of solution mining operations. .Grades of ore mined from these deposits
range from 0.15 to 0.30 percent U3O8. Solution breccia pipe uranium deposits are located in the
Northern Arizona Strip and average approximately 0.64 percent U-238; these deposits have been
mined using surface and underground methods (Pillmore, 1992). Vein deposits have been mined on
an infrequent basis using underground methods in Colorado and Utah. Phosphatic deposits are
associated with phosphate ores in Florida; uranium has been recovered to a limited extent as a
.byproduct of phosphoric acid production from these ores.
Proprietary information surrounding the small number of mines currently producing uranium limits
the level of detail available about the nature and size of recent operations. The primary extraction
(and beneficiation) method used to recover uranium from ore deposits is in situ leaching. According
to the U.S. Energy Information Administration, in situ mining operations generated two-thirds of the
uranium produced in the United States in 1991. The remaining 33 percent of the uranium produced
hi 1991 was by conventional milling operations (DOE/EIA, 1992). Prior to the drop in uranium
prices, ore was more commonly beneficiated using conventional milling techniques.
3.3.6.3 Beneficiation
In conventional uranium milling, the initial step involves crushing, grinding, and wet and/or dry
classification of the ore to produce uniformly sized particles. Ore initially feeds into a series of
crushers where it is reduced to fragments less than 19mm (3/4 inch). Ore from the crushers feeds •
into the grinding circuit where ball and/or rod mills, and/or autogenous or semiautogenous grinding,
continue to reduce the size of the ore. Water or leach liquor is added to the system in the grinding
circuit to facilitate the movement of the solids, for dust control, and (if leach liquor is added) to
initiate leaching (DOI, 1980).
Classifiers, thickeners, cyclones, or screens are used to size the finely ground ore, returning coarse
materials for additional grinding. The slurry generated in the grinding circuit contains 50 to 65
percent solids. Fugitive dust generated during crushing and grinding is usually controlled by water
sprays or, if collected by air pollution control devices, recirculated into the beneficiation circuit.
Water is typically recirculated through the milling circuit to reduce consumption (EPA, 1983a).
3.39 September 1994
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Overview of Mining and Benefidation
EIA Guidelines for Mining
After grinding, the sluny is pumped to a series of tanks for leaching. Two types of leaching have
been employed by uranium mills, acid and alkaline. Acid leaching has' been the predominant leaching
process employed by conventional mills, although some mills have used an alkaline system and some
lip Jigii& JK& (Merritt, 1971). In the discussions;that,follow, an overview, qf leaching is
provided followed by a more detailed description of both acid and alkaline leaches.
-
steP in any uranium leaching operation is oxidation of the uranium constituents. Uranium is
found as uranium dioxide (UO2, U*4 oxidation state) in many deposits (pitchblende and uraninite).
Uranium dioxide is insoluble;,,,, to create'a soluble form, UOj is oxidized from the IT" to .the, U*6
oxidation state. Iron jnratjriftin. the ore, and oxygen, are- used to perform' oxidation via the
following reactions (Twidwell et al., 1983): .
(1) alkaline tlCfe + teC^ ?± UQ,
(2) acid~ "Uft + 2Fe-:5 £' UO??
Iron can be readily regxidized by the addition of O2, sodium chlorate (NadO3), or manganese oxide
illiiill (jf^nOj) to the lixiviant.
!J* ff£™ 2ft 2 J,2£fiS i8 me stabilization of the uraniferous ions in solution. The,,, uraniferous
ions form stable, soluble complexes with sulfate (SO,*) prcarbonate (Cp^2). Sulfuric acid is added
as the source for sulfate ions; sodium bicarbonate, sodium carbonate, or carbon dioxide are added to
alkaljne leach circuits to provide a carbonate source. Uraniferous complexes are formed through the
*-" reactions (Twidwell et al., 1983):
ffia + 2i! 2 HCMCO^ t
-J- 6SO/2 5* UO2(SO4)6'4.
*l^ leaching operation, sulfaric acid is added to the crushed ore slurry to maintain the
10.5 and 2.0. Twenty to 60 kilograms of sulfuric acid per metric ton of ore are normally
jNaClOi SLMnOj !? .added to rnajntam.....the oxidation by iron.'
i SSSSIS ISSS !§ ISsiiily found in uranium deposits, the ore body itself suppUes the iron in the leach
i step
i:, ...... fli ...... Hi; ...... liila).
lill 'iillllll1 ' i (III
^^aljae leaching is not as effective as acid leaching for uranium recovery and is not "used except in
caSK of hi£h Kme^ntent ores. Typically, ore bodies containing greater than 12 percent carbonates
*^ Ie??h«i- MtetiB* leaching is primarily employed in fn situ mining operations,
a fcw conventional mills have maintamed alkaluie leach circuits (Merritt, 1971). Alkalme
SilSuSSSPS oxidant ^ long retention times to oxidize the uraniferous
* **" 198-3>- A8 stated Previously, oxygen and a carbonate source are added to
111 iiiiiiini inn iii i nil 111 iii iii . ii 11! iiiHiii niiii i in 11 in iiiiii (i in iiiniii 111 linn in i ivi i IN iiiinii
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EIA Guidelines for Mining _ Overview of Mining and Benefication
water to make up the lixiviant. The carbonate (CCV2) and bicarbonate (HCO3") concentrations are
typically 40-50 g/L and 10-20 g/L respectively (Merritt, 1971). For its leaching process, the
Highland in situ project injects O2(g) and CO2(g) hito the lixiviant prior to underground injection.
The dissolution of CQj in the lixiviant produces both CO3'2 and HCCy ions (Hunter, 1991).
Leaching maybe performed hi tanks, heaps or in situ. In situ leaching is practiced on low-grade
ores; after crushing and grinding, higher grade ores are typically leached in tanks at conventional
mills. Low-grade ores may also be amenable to heap leaching; however, the available literature
indicates that the application of this technique to uranium ores has been and is limited and
consequently it is not be discussed hi detail. Leach tunes vary depending on the grade of the ore,
grain size (amount of grinding), and the method used. Leaching in tanks may take from four to 24 .
hours while heap leaching may be measured in days or weeks (Twidwell et al., 1983). ..
Once the uraniferous compounds have been leached from the ore, the pregnant leach solution is
separated from the solids using classifiers, hydrocyclones, and thickeners. Sand-sized particles are
removed first and washed with clean water or barren lixiviant/raffinate . Continued treatment
removes the slimes, which are also washed. Depending on the settling time allowed by beneficiation
operations, flocculants may be added to the process to encourage settling of suspended solids. After
final washing, the solids (sands and slimes) are pumped as a slurry to a tailings pond for further
settling. The pregnant leach solution then enters a solvent extraction or ion exchange circuit. Wash
solution is recycled to reduce consumption of leach chemicals, solute, and water (DOI, 1980; EPA,
1983a). . .
Solvent extraction is an operation that concentrates specific ions. Generally, solvent extraction uses
the immiscible properties of two solvents (the pregnant leach solution and a solvent extraction
solution) and the solubility properties of a solute (uraniferous ions) hi the two solvents. Solvent
extraction is typically employed by conventional milling operations since solvent extraction can be
used in the presence of fine solids. The pregnant leach solution is mixed hi tanks with the solvent
exchange solution. Selection of a solvent in which the target solute (uraniferous ions) is preferentially
soluble allows the solute to migrate to the solvent exchange solution from the pregnant leach solution
while other dissolved compounds remain hi the leach solution. Normally, the solvents are organic
compounds mat can combine with either solute cations or solute amons. A» wanyl-caxbonatec or
sulfates are commonly generated in ti» leaching step, anionic soiveni extraction solutions are typically
employed; cationic solvent extraction solutions way be employed depending on liakjae characteristics
of die «es or Jeadnng
Among the anionic SX solutions are secondary amines with aliphatic side chains, high molecular
weight tri-alkyl tertiary amines, and quaternary ammonium compounds. Cationic SX solutions
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EIA Guidelines for Mining
include monodocjecyl phosphoric acid (DDPA), di-2-ethylhexyl phosphoric acid (EHPA), heptadecyl
phosphoric acid (HDPA), and dialkyl pyrophosphoric acid (OPPA). (Twidwell et al., 1983)
* the solvent-exttaction solution is diluted in a low cost carrier -such as kerosene with, a
tribal phosphate modifier or a long chain alcohol (Twidwell et al., 1983). The uraniferous ions
preferentially move from the aqueous pregnant leach solution into the organic solvent as the two are
d fl?ated *D°I> 198°^' After'the uraniferous compounds are thus' enacted from the '
I«cE ...... solution, the barren lixiviant ..... "'" ^' .......
crcut.
After the solute exchange has taken place, the pregnant solvent extraction liquor must be stripped.
rocess ;(Twidwell et al., 1983). . ;
lake solvent exchange, ion exchange operations make use of organic compounds to perform solute
C0ncenteation- Generally, fixed organic resins contained within a column are used to remove
uraniferous c?)inpound| £"*!§e, E^BMnt leach solution by adsorption. After adsorption, the
UtaiferoUS COn9>0m^ rcsins are released (eluded) by a stripping solution and sent to
within meir operations.
Resins are constructed with anionic or cationic functional groups (typically anionic for uranium
'con^
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EIA Guidelines for Mining . Overview of Mining and Beneficiatfon
exchange column increases. Once the uranyl ions at the outlet reach a predetermined concentration,
the column is considered to be loaded and ready for elution. Typically, the pregnant leach stream is
then directed to a fresh vessel of solvent exchange resins. A concentrated chloride salt solution is
then directed through the loaded resins, eluting off the uraniferous complexes. The pregnant elute'
liquor can then be directed to the precipitation circuit. The pregnant elute solution may be acidified
slightly to prevent the premature precipitation of uraniferous compounds (Twidwell et al., 1983).
Once the uraniferous ions have been concentrated by solvent extraction or ion exchange, they are
precipitated out of solution to produce yellowcake. The precipitate is then washed, filtered, dried and
drummed. The chloride stripping solution is recycled back to the stripping circuit. The type of ion
concentration solution (e.g., acid or alkaline solution) governs the precipitation method employed.
With acid pregnant stripping liquors or pregnant elute liquors, neutralization to a pH of 6.5 to 8 using
ammonia hydroxide, sodium hydroxide or lime results in the precipitation of ammonium or sodium
dhiranate (Merritt, 1971). Hydrogen peroxide may also be added to an acid pregnant stripping liquor
or pregnant elute liquor to precipitate uranium peroxide (Yan, 1990). All forms .of the uraniferous
precipitate are known as yellowcake.
Alkaline pregnant stripping liquors or pregnant elute liquors typically contain uranyl carbonates.
Prior to precipitation of the uranyl ions, the carbonate ions must be destroyed. An acid (usually
hydrochloric acid) is added to the carbonate concentrate solution to break down the carbonates to
carbon dioxide; the carbon dioxide is vented off. Once the carbonates have been destroyed, the
acidified solution is neutralized with an alkali or treated with hydrogen peroxide to precipitate the
uraniferous compounds. Precipitation operations based on neutralization of acid solutions are favored.
because of the higher purity of the yellowcake product; sodium, carbonate, and, in some cases,
vanadium, are impurities that may be present hi yellowcake produced from alkaline neutralization
(Merritt, 1971).
The yellowcake is separated from the precipitation solution by filtration. Thickeners may be used in
conjunction with filtration units. The filtered yellowcake can then be dried and packaged for
shipping (Bureau of Mines, 1978). The supernatant generated from precipitation and dewatering
circuits can be recycled to the respective solvent extraction or ion exchange stripping solution.
Typically, yellowcake is shipped to a Federal facility for processing. In the processing step, uranium
fluoride (UFj) is produced from yellowcake. The uranium fluoride is then enriched, an operation that
concentrates the U-235 from 0.7 percent to approximately two to three percent. The enriched
uranium fluoride is further refined to ultimately produce the fuel rods used in nuclear reactors.
In situ leaching is the most commonly employed solution technique and continues to be employed by
at least two mines in Wyoming. Nebraska's Department of Environmental Control permitted an in
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EIA Guidelines for Mining
|
B, tii 2S
amoebic
ilW^ • .-
mineral d
ton in 1990 although its operational status was not determined (NDEC, 1990). Deposits
to in situ
are usually (if not always) within an aquifer. Water quality within a
LI
'
'
deposit may vary depending on the presence of and boundary between oxidizing and reducing
groundwaters. Ore body characteristics, including chemical constituents, grade, and permeability, are
key considerations in the development of production methods (selection of lixiviants, arrangement of
well patterns, etc.). Ideally, the deposit should be confined by impermeable strata above and below
. the deposit to prevent contamination of adjacent aquifers by excursions (solution leaks from the ore
zone). In situ production operations consist of three phases: removal of minerals from the deposit,
concentration of uraniferous minerals, and generation of yellowcake. In addition to the production
, operations," water treatment and, in some cases, deep well injection facilities, are employed.
In the case of in situ operations, beneficiation serves as the first phase of the mining operation. In in
situ mining, barren solvent (lixiviant) is introduced to the deposit through injection wells to initiate
m i , the operation. The lixiviant contains both an oxidizing agent to solublize the target minerals and a
i < iii
complexing agent that binds to the target minerals and keeps them in solution. Wyoming in situ
llJiiiin "in ••iiiil " if " 3 ! ! 15 9 3 5! !P '-!S
•••I . operations recover uraniferous compounds using oxygen gas as the oxidizer and carbon dioxide, as
the complexing agent (WDEQ, 1991). The barren lixiviant is charged with carbon dioxide as the
IH^ IIH^ lfl|M • •^•••••1 lilllllH IIIIIIIIB lllllllllllH IIIIIIHI Illllillllllllllll 111 I 111 II 111 II •• llllllnl IIIIIIIH^^^ Illllllllllllll 1 tin iillllll Illllliilllll1 •
,^ solution leaves the ion exchange facility. Oxygen is injected into the solution in the wellfields,
immediately before'the lixiviant flows into the injection wells. As the solution moves through the
deposit, uraniferous minerals are oxidized and uraniferous ions move into solution. Carbon dioxide
* i ' i . i1 ' •• -
m the lixiviant reacts with water, forming carbonic acid, which in turn complexes with the solubilized
uraniferous ions, forming uranyl carbonates. The uranyl carbonates and gangue minerals solubilized
in the operation remain in solution as the pregnant solution is pumped to the surface through
i production (recovery) wells. "
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II llllllli Bill
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iii i
: lixiviant is pumped from die production wellheads through sand filters to remove any large
I ,. , i , • ' « , „ '•' I.,1'" ; , |. i
pardculates; the lixiviant is then transferred to ion exchange units. Depending on die facility, the ion
exchange units may be placed in trailer-mounted tanks or moved via tanker truck from satellite plants
to a central processing facility. When the resins hi die ion exchange units are loaded, the uraniferous
compounds are stripped from the resins and precipitated to form yellowcake. The lixiviant, after
passing through the ion exchange unite is recharged with carbon dioxide and oxygen following the ion
exchange circuit and injected back 'into me" ore'body! "
,, Numerous well patterns have been investigated since the early 1960s \vbsninsitu "mining techniques '
were first employed. Five spot well plrtelms', 'which consist' of four' U^eietiTn wdk fonni^; the '
"» ''"'"' ' 'injection and production" wells are used in narrow deposits. The" spacing between mjection and '""'""'
ISIISI ii.:::: production wells can range ^m^j^^^^^Jtezn^«|df^^ 2§!!5!!!? M^^iriMI'''!?!?^
• also .vary. ' ' ' ' ' ' ' ' i i ' ' ' MI ' " i i ' MI ^ ' ' ' " " ^
3-94
Illi1' iii'liiS'i1 IE'l!!W,,, i' lli'ii I!1" :!'i!!:!!'jiiSI'-IRlllilHl i11*!11!1 "OlWlilllfiiil'iiWilli^iiiii!; i 'I11'!'
September 1994
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EIA Guidelines-for Mining Overview of Mining and Beneficiation
Mining units are portions of the deposit to be mined during one. operation, often, following "pods" of
ore deposited along a roll front. Mining units may be mined in sequence or simultaneously.
Pumping rates at one in situ operation in Wyoming ranged from two gallons per minute (gpm) to 30
gpm for injection wells and five gpm to 40 gpm for production wells. Approximately one percent of
the fluid drawn from the well field is removed as a bleed to generate a cone of depression within the
"production zone." Pumping rates can be varied at each well individually in order to compensate for
differences in permeability of the deposit and the gradient being generated by the production
operation. . .' ' . ~
Uranium recovery rates at in situ operations are highest within the first year of operation;
economically viable recovery within a wellfield usually lasts one to three years under recent (1990s)
market conditions.
Restoration of the aquifer can be conducted using one (or more) of the following techniques:
groundwater sweep, forward recirculation, reverse recirculation, and directional groundwater
sweeping. In some cases, a reducmg agent may be injected prior to any restoration to reverse the
oxidizing environment created by the mining process. A reducing agent may also be injected during
later stages of restoration if difficulties arise in stabilizing the.-aquifer (Lucht, 1990).
A groundwater sweep involves the selective operation of production wells to induce the flow of
uncontaminated groundwater into the mined zone while "the withdrawn water continues to be treated
through the ion exchange circuit. Contaminate water withdrawn from the aquifer can be disposed c t
in lined evaporation ponds or treated and discharged. Groundwater sweeps are most effective in
aquifers with "leaky" confining layers, since uncontaminated groundwater can be induced to flow in::
the mined areas. Typically, two or more pore volumes are required to improve water quality
parameters. The disadvantage to groundwater sweeping is its consumptive use. of groundwater
(Osiensky and Williams, 1990). . .
Forward recirculation involves the withdrawal and reinjection of groundwater through the same
injection and production wells that were used during the mining operation. Groundwater withdrawn
from the mined aquifer is treated using ion exchange or reverse osmosis with the clean water being
reinjected and recirculated through the system. The water being reinjected is treated to the extent that
it meets or exceeds the water quality required at the endpoint of restoration. The method does not
allow the removal of any lixiviant or mobilized ions that may have escaped from the mined aquifer.
For this reason, forward recirculation is most effective in restoring the portions of the aquifer
associated with the ulterior of the well field (Osiensky and Williams, 1990).
Reverse circulation techniques can also be employed hi which the function of production and recovery
wells is reversed. Again, "clean" water is injected, this time through the recovery wells, while the
3-95 September 1994
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iniiiiliiiiiinii iiiiiiliiiinniii||iiiiiniinniiniiinn
Overview of Mining and Benefication
11
in in in in n In n I
EIA Guidelines for Mining
injection wells are employed to'withdraw groundwater from the aquifer. This method is also more
effective in restoring the aquifer in the interior of the well field than along the perimeter (Osiensky
and'Williams, 1^90). ' ' " : " '
11 iiiiiii in i
111 IB
Directional groundwater sweeping techniques involve the pumping of contaminated groundwater from
specific wells while treated water (at or surpassing baseline quality) is injected into the aquifer beyond
the mined sections of the aquifer. The clean water is then drawn into the contaminated portions of
the aquifer, removing the residual mobilized ions. Clean water injection can progress across a
lllllllllllll j i n in ill mi nil i j n nn i i n inn in ninnim nun j li 111 11 i in f 1111 in iiini in n mini in inn in in inn I"1 i ii.!p!iiiiiiiniiigifi!ii!iiiiiii!iiiiiiiniiiiijnniiiii!iiiiiiiiiiilil iiiiiiiniiiiiiiiiiiiiiiiiiiiiiiiiirj'/iHiiiiiii .'iiiiiiiNnjiiiiiii.'iiinivnr,
wellfield as the contaminants are progressively withdrawn (Osiensky and Williams, 1990).
Uranium can be recovered during the early stages of the restoration process as the water from the
production wells passes through the ion exchange system!. Eventually, uranium recovery is abandoned
f „ ' [ I, ;-i
while restoration continues. A rinse of multiple aquifer pore volumes is typically required to reach a
satisfactory level of restoration. The number of pore volumes required depends on the ease with
which the aquifer returns to baseline conditions and the permit requirements established in State
: ' Wlllams, 1990; Bureau of Mines, 1979).
Demonstration of successful aquifer restoration is accomplished through extended monitoring. The
State of Wyoming, for example, requires that selected wells be monitored for stability for a period of
at least six months following the return of monitoring parameters to baseline levels (WDEQ, 1990)..
• '
rastes generated by uranium mines and nulls would include those generated in other mining sectors
waste rocl, sp'extractibnTieacning
~ ill
tailings, and refuse). Mining method
(conventionalversus solution) has a bearing on the types of wastes produced. Under the Uranium
Mill Tailings Remediation Control Act (UMTRCA), source handling licenses issued by the Nuclear
Regulatory Commission (NRQ place specific requirements on the disposal of radioactive wastes; the
design and construction of tailings impoundments thus have to address requirements for permanent
storage of these wastes. Radionuclide-containing wastes generated by in situ operations-are typically
shipped'11 to tailings impoundments at mill sites.
greatest volume of waste generated by ogen git and underground mines is waste rock, which is
§om£ HE!£ 5** raay *** ^^d °'r onsite 'construction
iiiiiiiiiiiiiiiii 11 i i nil
(roads, foundations, etc.). The generation of acid mine drainage is one of the principal concerns
siirrcfilling waste rock hi other mineral sectors. The potential for generation of acid drainage from
rock has not been addressed in available reference materials. However, pyrite is
ores, and may present the potential to create acid mine
drainage. Other materials generated by open pit and underground mining operations, including low-
: ore and mine water, are ^y^gjjy wai]ZS^ pireite during the active life of the facility. Low-
3-96
September 1994
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' EIA Guidelines for Mining Overview of Mining and Benefication
grade ores that are not beneficiated ultimately become waste rock. If a mill is co-located with a
mine, mine water can be used as makeup water in the beneficiation operation. If a mill is not nearby,
mine water may be treated and discharged as mine drainage or used for dust suppression.
The principal waste generated by conventional beneficiation operations is tailings. In situ operations,
and to a lesser extent conventional mills, generate waste leaching.solutions. Disposal of these wastes
is dependent on the type of operation; beneficiation wastes generated by in situ operations are
disposed of by one of four management methods: evaporation ponds, land application, deep well
disposal, or shipment to NRC-licensed waste disposal facilities. Most beneficiation wastes generated
at conventional mills are disposed of in tailings impoundments.
Waste constituents of concern include: radionuclides (radium, radon, thorium, and to a lesser extent
lead), arsenic, copper, selenium, vanadium, molybdenum, other heavy metals, and dissolved solids.
Brines, spent ion exchange resins, and chemicals used in beneficiation operations are also constituents
of wastes generated during beneficiation. Airborne particulates from blasting, loading, and vehicular
traffic can also be of concern.
3.3.7 OTHER METALS
3.3.7.1 Aluminum
f
Bauxite (a mixture of primarily three aluminum hydroxide minerals, diaspore, gibbsite and boehmite,
and impurities) is the ore of aluminum (Hurlbut and Klein, 1977). Deposits of bauxite in the United
States are located in Arkansas, Georgia and Alabama. In 1992, bauxite was being mined from
surface excavations in Georgia and Alabama (Bureau of Mines, 1993). Virtually all of this domestic
bauxite ore is consumed in the production of nonmetallurgical products (primarily refractory grogs)
and not in producing aluminum (Bureau of Mines, 1993). Imported metallurgical-grade bauxite 'is
used in the production of aluminum in the United States.'
Alumina production is shining to the large-scale bauxite producing countries in response to increasing
energy costs in North America and Europe (Bureau of Mines, 1993). If this results hi increased costs
for alumina for U.S. plants, nonbauxitic aluminum resources in the United States may become
economically more attractive. Current conditions indicate that the United States will continue to be a
major importer of metallurgical-grade bauxite and alumina, precluding the need for extensive
expansions of U.S. bauxite mines (Bureau of Mines, 1993).
The two active bauxite mines use the general surface mining operations discussed in Section 3.1.
Draglines, shovels and haulers remove ore from open pits and transport it to a storage area. Ore may
be loaded directly from storage to the processing plant, or it may undergo beneficiation at the mine.
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Overview of Mining and Benefication
EIA Guidelines for Mining
. IIIIIN iillillll ih I I11!1
•iiiiiiiiiiiiiiiiii i ii in
Beneficiation
P '' j1,,.' • , „
|S^^
Crushing is common to all bauxite
processing; however, the steps following crushing depend on the makeup of the ore. After crushing,
the ore may be washed to remove sand'"and clay sized impurities.' Impurities such as iron, and ,
titanium may be removed using heavy media or magnetic separation, jigging, or spiral concentrators.
The washed ore is generally shipped without further processing; however, it may be dried or calcined
at the mine. Most bauxite ores are not dried at the mine site, because drying may create serious dust
r
problems during transportation and handling (EPA, 1979).
;::i iiij iii! iiiiii
The- wastes produced ...... from the beneficiation ..... of bauxite ores is the wastewater used in the' washing *
process. Generally this water is discharged to the pits and not to surface waters. Chromium, copper,
* ........ nickd ..... a^'zliichave ..... ^j| ..... ^j ..... ,-—— ...... ^ ..... — - ..... _ _ ___ ....... g. ..... _=___ ....... _ ...... __ ...... ___ .....................
He ..... drainage ...... can be ...... 'fflmfpSL' (&&&&)'.
1982)1 ....... In
3.3.7.2 Tungste
The princijpal ore minerals for tungsten are wulframite ((Fe,
and scheelite
, "
resistance and good thermal and electrical conductivity, make it an important material for ..... 'use ....... in"
Tungstenoreshavegenerally
.using gravity concentration or
" gravity of tungsten minerals is high and therefore gravity concentration methods primarily are used.
However, scheelite (the principal U.S. ore) is very friable and in the process of wet-grinding a
' (mBiderab'ie amount' ot^slxmes1 axe produced'and •—.——-« .^H*— — «,-.-». .—«g«« 9j"Q •
I i • , i HI i ir
increase overall recovery, finely divided scheelite particles in the slimes are concentrated by flotation
techniques using fatty acids as collectors. Several hydrometallurgical procedures are used for
upgrading tungsten concentrates. Scheelite concentrates from flotation tend to be lower grade than
gravity concentrates. Calcite and apatite are the principal contaminants hi these low-grade
concentrates (scheelite concentrates seldom contain sulfides in large amounts). These impurities may
be leached out
, and the concentrates upgraded in die process. A first-stage leach with
hydrochloric acid (HC1) removes the calcite as calcium chloride (CaClj) solution, which is discarded,
"'" ' ! !!!|"| " ' I ' I!!""! :l ;'' r1 * ' ' ' F "
while a second-stage leach is used to dissolve the apatite, which is not dissolved hi the presence of
calcium chloride,
One of1 the many variations of'tungsten ore"'benefication 'pyoggjj^g^1 jj!m^ h^dromeailurgicai
i i i i i i i
treatment of low-grade scheelite group concentrates to produce calcium tungstate. A water slurry of
scheelite concentrates from flotation machines is digested in a pressurized digester vessel with sodium
carbonate and steam to produce tungstate and molybdate in solution. To remove the_ molybdenum,
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September 1994
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Guidelines for Mining ' Overview of Mining and Benefidation
.'
the solution is filtered and heated to 91 °C (195 °F), and sodium sulfide is added to precipitate
molybdenum. The solution is adjusted to pH 3.0 with H2SO4 to complete this separation. The hot
purified solution is neutralized with sodium hydroxide to a pH 9.2, then treated with calcium chloride
to precipitate calcium tungstate. Alternatively, the filtered solution after molybdenum separation may
• be solvent-extracted by a proprietary process to produce ammonium paratungstate, which is
crystallized out of solution and dried (EPA, 1976).
The discharge from tungsten milling operations has been found to contain high concentrations of
copper, lead, and zinc (EPA, 1982).
33.73 Molybdenum
Molybdenum is an important metal for use as an alloying agent in steel, iron and superalloys (Bureau
of Mines, 1993). Molybdenite, is the major ore mineral mined for molybdenum. In the United
States, the economically important deposits of molybdenite are generally low-grade porphyry or
.disseminated deposits, but contact-metamorphic zones, quartz veins, pegmatites and aplite'dikes, and
bedded deposits in sedimentary rocks have also been exploited for molybdenite. Most porphyry
copper deposits contain low concentrations of molybdenite (0.02 percent to 0.08 percent). Primary
molybdenite deposits typically grade 0.2 percent to 0.5 percent molybdenite. In 1992, 45,500 metric
tons of molybdenum was mined in the United States, two-thirds for export. Three mines (in
Colorado and Idaho) mined molybdenum ore and 11 (in Arizona, California, Montana, New Mexico,
and Utah).recovered molybdenum as a byproduct. The United States was the major producer of
molybdenum in 1992, and will continue as a top five world producer throughout the rest of the
century (Bureau of Mines, 1993).
Molybdenum ore is mined by both open pit and underground operations in the United States. In
1992, approximately 40 percent of U.S. production was from underground mines and 60 percent fro-
open pits. Underground mines typically use caving methods, since these methods allow for the
economic removal of large tonnages of low grade ores at a low cost. Conventional open pit mining
methods are used. In underground mines, very little waste rock is removed. Significant tonnages of
waste rock can be removed in the development and mining of an open pit.
After the molybdenum ore is mined, it is transported to a mill for beneficiation. The ore is generally
crushed and ground at the mill before traditional flotation methods are used to concentrate the ore
minerals. A final concentrate of 90 percent to 95 percent molybdenite is produced by the
beneficiation operation. The major impurities in the concentrate are copper, iron and lead minerals.
Molybdenite recovery from copper ore is more complex due to the low percentage present hi the ore.
As hi the flotation of other ores, the major wastes produced are tailings, and these are generally
disposed of in tailings impoundments.
3-99 September 1994
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Orerview of Mining and Benefication J2IA Guidelines for Mining
3.3.7.4 Vanadium
SSSlfJ ..... !! ..... i11!!!!!! !'!, &nadimp, ....... is generally not mined as the primary metal of an ore, but as, a co-product, as in carnotite
ores (recovered for uranium and vanadium) mined in the western United States. Currently, one mine
in fhe United States recovers vanadium as the primary constituent of the ore. The primary use of
vanadium is as an iron and steel alloying agent. Mining of the uranium and vanadium ores in the
Jl m , .......... ',";,,!, ,„,;„,, ........ • , ........ ,,;, ,„, ..... ,,, „,,,,„, ...... „ ,,,,;,„'; "„; ........ ;,„,,,, •„, ....... i „';•:!! ,:,!,, ,,„,,,, .;i",f.1;ljl;ll,i .......... :,,, ......... „„, ....... ........ / ,, ....... „
western United States has employed open pit and underground mining methods. The vanadium mine
[[[ in Arkansag ...... us£g ...... open pit methods to extract the vanadium ore.
Mined vanadium ore is crushed, dried, ground, and screened to sizes less than 1.17 mm (-14 mesh).
i ' . • • • " . i • i > x
It is men mixed with about 7 percent weight of salt, pelletized, and roasted at 850 °C (1,560 °F) to
convert the vanadium to soluble sodium vanadate, NaVO3. It is then quenched hi water and acidified
'f with.' sulfiuic aqid to pH 2.5-3.5. The resulting sodium decavanadate (Na<;V,0O2s) removes impurities
such as sodium, calcium, iron, phosphorous, and silica. Slightly soluble ammonium vanadate,
^ i NHtVQj, ........ is ..... precipitated from the ...... stripping solution with ammonia. The ammonium vanadate is then
calcined to yield vanadium pentoxide, V2O5 (EPA, 1976).
i
» 7 »5
.
Aircraft ..... and ...... space ..... appjtfcations ..... account ...... for ..... 75 percent of titanium metal consumption, with the
z ....... SHi ...... S&L ..... ?PPiications-
), and ruffle (TiO^. These minerals are found concentrated
^SsSSSifflSi Sffii feP°5!!5: !?, !.????> only sand deposits of ilmenite were being mined hi the'u.S
(Bureau of Mines, 1993).
:: ; : :' I : : ' : : ' : :i
J The method of mining titanium minerals depends upon whether the ore to be mined is a sand or rock
deposit. Sand deposits occurring in Florida, Georgia, and New Jersey contain 1 to 5 percent TiO2 in
[[[ • hourj. No .hard rpck deposits are currently active.
The land ore is treated by wet gravity methods using spirals, cones, sluices, or jigs to produce a
bulk. ...... 2J»-*}» ...... JS^JSS! ....... SSfi316- ** manv ^ five mdm*^ ...... marketable ...... .minerals,,,, are ...... then,
separated from the bulk concentrate by a combination of dry separation techniques using high-tension
..... SS ...... S^ff10 scpa^ofs, occasionally hi conjunction with dry and wet gravity
titanium minerals from the silicate minerals. The minerals are fed onto a high-speed spinning rotor,
and a heavy corona (glow given off by high voltage charge) discharge is aimed toward the minerals at
the point where they would normally leave the rotor. -The minerals of relatively poor electrical
conductance arejunned to the rotor by the high" surface charge they receive, on passing through the
I'III IH i ill III 'illllliillliliilll lilililiiilllllliiliill ' Mil ii:: iflillllSIl !1W BBIIILIHpa*! I piffil1&fi«MSiSBtf!^S3B ffl illllll
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EIA Guidelines for Mining . . Overview of Mining and Beneficiation
high-voltage corona. The minerals of relatively high conductivity dp not hold this surface charge as
readily and so leave the rotor hi their normal trajectory. Titanium minerals are the only ones present
of relatively high electrical conductivity and are, therefore, thrown off the rotor. The silicates are
pinned to the rotor and are removed by a fixed brush.
Titanium minerals undergo final separation in induced-roll magnetic separators to produce three
products: ilmenite, leucoxine, and rutile. Separation of these minerals is based on their relative
magnetic properties which, hi turn, are based on then* relative iron content: ilmenite has 37 percent to
65 percent iron, leucoxine has 30 percent to 40 percent iron, and rutile has 4 percent to 10 percent
iron.
33.7.6 Platinum
Platinum is one of the six closely related platinum-group metals (platinum, palladium, rhodium,
ruthenium, indium, and osmium). Platinum and palladium are the most commercially important
metals of the group; in 1992, an estimated 1,730 kilograms of platinum and 6,050 kilograms of
palladium were mined. The United States automobile industry is a major consumer of platinum for
use in catalytic converters. Platinum group metals also are used in electrical .and electronic (29
percent), medical (9 percent), and other applications (24 percent). Demand for platinum is expected
to remain high as the use of catalytic converters increases around the world to control automobile
emissions (Bureau of Mines, 1993).
In the past, platinum mining hi the United States was mostly from placer deposits. The only
currently active platinum mine hi the United States is the Stiliwater Mine hi Montana; platinum-group
metals also were recovered as byproducts of copper refining hi Texas and Utah. Platinum and
palladium (at a ratio of 1:3) occur hi an igneous, strataform ultramafic rock at the Stiliwater mine
(Stiliwater Mining Company, undated). The deposit is exploited through underground cut and fill
mining methods. The ore is transported to the mill for crushing and grinding prior to entering the
concentrate circuit. After grinding, the ore is added to the froth flotation units along with reagents.
The recovered concentrate is dried before transport to a refining facility for the recovery of the
palladium and platinum. The mine received an amended permit in 1992 to double the mine's daily
production from 1,000 tons to 2,000 tons.
The tailings sluny-at the Stiliwater Mine is separated into coarse and fine fractions prior to disposal
(Stiliwater Mining Company, undated). The coarse fraction is pumped underground to be used as
sand-fill hi the underground mine. The fine fraction is pumped to a lined tailings impoundment. The
facility recycles water from the tailings impoundment back into the mill. Very little waste rock is
removed during mining. Most of the waste rock is used to raise the dam of the tailings impoundment
when additional capacity for the tailings impoundment is required (Stiliwater Mining Company,
undated).
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_. - , .— . i ;
3.4 COALMINING
.
I * ; , - •
This section focuses on surface and underground coal mining operations and environmental impacts
unique to the coal mining industry. Specifically, the subsections below addresses types of coal, .
geographic ...... location ..... of coal, ....... and ...... nmmig ....... and ...... reclamation methods ....... is ....... the ..... primary ..... determinants ....... of [[[
environmental impact. This approach was taken to isolate those areas of concern that are unique to
coal mining activities and to establish a workable methodology to assess the. magnitude and .
significance of potential impacts.
There are both similarities and differences between coal and other types of mining operations. Any
type of surface mining requires the removals of overlying soil and rock (collectively known as
overburden) prior to the removal of the resource. Coal and non-coal operations use many of the same
techniques in the development and often in the production phase of mining. All mining activities
...... ...... ..... ...... .......
must ...... control ...... surface water ..... runoff, ...... nfimifiiTg ....... fugitive dust, and avoid impacts to the surrounding
environment. *-.,-—
. i •-.. ' '" ™" - - • ..... ;
* i ,• - • • " • , '• • .< • •- ,- , . - "• ..... - .......
In addition to other environmental regulations, coal mining operations must .also comply with the
Surface Mining Control and Reclamation Act of 1976 (SMCRA). SMCRA greatly expanded the
regulatory requirements placed on the operation and reclamation of coal mines (see Chapter 6). One
of the most significant aspects of this program is that of reclamation; areas disturbed by coal mming
activities must be returned to approximate original contour and reclamation must be conducted
concurrently with mining. ,
3.4:1 • COAL FORMATION AND GEOGRAPHICAL DISTRIBUTION .
i , -
' 3.4.1.1 Types and Composition of Coal * .
llllllA IIIH^^ • lifH^^ illH^^ ii! t^ llM^ I >IIM^ "I
: Coal was formed through the accumulation and compaction of marine and freshwater plants and
"aniTtial^ living in ancient marshes. The accumulated organic material was buried by sediments and
altered from complex organic compounds to carbon.
Coal is classified based on the percentages of fixed carbon, natural moisture, and volatile matter
j ....................................... : ................................. : [[[ ! ............... ! [[[ ........... ' ............................. I .............. i .................... ; [[[
present. Lignite, subbituminous coal,- bituminous coal, and anthracite comprise the major classes of
coal. The percentage of fixed carbon increases, the percentage of volatile matter decreases, and the
heating value increases from lignite to anthracite (see Exhibit 3-13). Based solely on heating value,
thepaxost value ofcoal can e expected to ucreaseficom lgnte anmracite. gse suinir
.. content and other, end-use specifications ...... aid ...... requirements ....... can ..... significantly ...... influence ...... tie demand for
SHBSBBS coal, the heating value is only one of several criteria that determine the actual market value of coal
ii,, i ii IIPTPIUIillii 1 ,„ :J i!HI l.ll! IF: HlilWIIIIIIIIIIW^
^^^^^ • jiii<<' ^i'
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EIA Guidelines for Mining
Overview of Mining and Beneficiation
Exhibit 3-13. Types of Coal and Relative Percentages of Constituents
Type
Anthracite
Bituminous
Subbituminous
Lignite , '.
fixed Carbon
(Percent) -. -
> 86 .
47-86
-42
30
BTUs/Pound
12,000-15,000
.11,000-15,000
9,700
6,600
Volatfles
(Percent)
< 14
14
34
25
Moisture
(Percent)
3
3- 12
23
45
\.
Sulfur is the most abundant trace element in coal, and reduces the value of those coals in which it is
found. Sulfur occurs both as an inorganic constituent mineral (mostly in the form of pyrite) in coal
itself and as part of organic complexes associated with the deposit. When the coal is burned, sulfur
.contributes to air pollution and reduces coking quality. When exposed to oxygen and water, the
inorganic forms produce add ™ne drainage. . '.
The sulfur content of coals found hi the United States ranges from 0.2 percent to about 7.0 percent by
weight. The percentage of sulfur in coal generally is greatest hi the bituminous coals of the Interior
and Eastern coal fields. The sulfur contest of coal generally is less than 1 percent hi the Northern
Great Plains and Rocky Mountain Provinces for subbituminous coal and lignite. More than 90,000
million tons (64 percent) of the total surface-mmable reserves in the United States are low-sulfur and
occur hi the west.
Coal contains traces of virtually all elements. Burning coal results hi the concentration of most of
these elements hi the ash, although a few may be volatilized and emitted to the atmosphere. Arsenic,
barium, beryllium, bismuth, boron, cobalt, copper, fluorine, gallium, germanium, lanthanum, lead, .
lithium, mercury, molybdenum, nickel, scandium, selenium, silver, strontium, tin, vanadium,
uranium, yttrium, zinc, and zirconium occur in some coals hi concentrations that are greater than
their average abundance hi the crust of the earth.
3.4.1.2 Coal Provinces
Six coal provinces (Exhibits 3-14 and 3-15) are defined hi the United States: the Pacific Coast,
Rocky Mountain, Northern Great Plains, Interior, Gulf Coast, and Eastern.
Coal deposits hi the Pacific Coast province are found hi scattered fields.hi California and Oregon, and
hi one large field and scattered small fields hi Washington. California coals are mostly of Eocene to
Miocene age,.and range hi rank from lignite to high volatile bituminous. Oregon coals range from
subbituminous to bituminous. Washington coals range from subbituminous to anthracite, but most are
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September 1994
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11 1
Overview of Mining and Benefication
EZA Guidelines for Mining
Exhibit 3-14. Coal Provinces of the United States
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3-104
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3-? 05
September 1994
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Overriew of Mining and Beneficiation EIA Guidelines for Mining
I I * '
subbipuaninous to bituminous; some also are of coking quality. Coals in Alaska range from lignite to
fight .volatile bituminous grades. Coals are found in large fields along the. Arctic Coastal Plain, and in
smaller fields located both inland and along or near southern shorelines.
The Rocky Mountain Coal Province is bordered on the east: by the Great Plains, and on the west by a
series of high plateaus, including most of New Mexico, Colorado, Utah, Arizona, and parts of
. Montana and Idaho, Scattered small fields are found in central and southern New Mexico.
High volatility bituminous coal is found ha rocks^of Upper Cretaceous age in the western Montana
'area. ^Coal bgls gig thins jngure, and usually gSyd^storbedbyfoldhigand faulting. The Big
£ ftm Basjg coa|s of Wyoming and coal found in extreme southwest Wyoming range in age from late
Cretaceous and Paleocene, and is classified from lignite through high volatile subbituminous. These
deposits occur in lenticular beds which rarely persist at a minable thickness for more than 5 miles at
outcrop. Dips of locally folded strata can ^^ 550 ^ resulting ^ ^ irregular distribution of coal '
outcrop. The Paleocene age coals of the Hams Fork region range in rank from subbituminous to
i%n volatile bitumnous. Beds pnggherjrade coals may be as thick as 20 feet; thicknesses of .lower
grade coal range to100 feet. These coal beds are situated in a highly complex zone of thrust faults
and folded rocks, resulting in steeply dipping strata and mereby making minhig difficult hi most parts
of the region. • .
In c^p1 Wyoming (the Wind River Basin) coal beds are Late Cretaceous to Paleocene hi age, and
aw aaoffly subbitumtoous. Although coal beds may approach thicknesses to 17 feet, surface mining is
m^i ...... jjjkultjjy the steep ...... djps of the strata. ................ ID ...... southwestern ..... Wyoming, coals range in rank from
subbituminous to high volatile bitummous, and Mgher rank coak loc^y nay occur in areas of
« igneous intrusion and intense structural deformation.
"
111
major beds up to 77 feet thick. Coals found hi me Green River Region within the Colorado Plateau
of Arizona, New Mexico, Colorado, and Utah, are generally found in horizontal strata of sedimentary
origin- Erosion of these strata has resulted in formation of canyons, mesas, and buttes. The
landscape comprises wide plateaus, uplifts, and broad basin areas. The Late Cretaceous age coal beds
: Hll^ UIB&. Coal Region range hi rank from subbituminous to coking quality high volatile
bituminous; some semianthracite and anthracite deposits occur hi the Crested Butte Field of the Uinta
Region. Coal bed thicknesses generally range from 5 feet to 15 feet, but locally may approach 40
laSHIttSSJi US iSsSSiiSSSSS^RP^ aSe coals of me Southwestern Utah Coal Region range hi rank from
subbitirainous to high volatile bituminous, with local occurrences of anthracite. These coals are
ft""*1 ^ fiat-lying to gently dipping beds from 2 feet to 30 feet thick. The Late Cretaceous and
Eocene age coals of the San Juan River Coal Region occur as lenticular, discontinuous deposits up to
5 feet thick in areas of complex geologic structure. Thicker, more continuous coal beds up to 38 feet
iiiti v in mmm " ii'i i ill nil IH^^^ ii ^\im i iiiii'iiliiii nil iiiiiii i11 ill IIP ii iv ill I* iiiiiiii1)'! i liiii (iiiii'iiii ill ii iiw i«11 • > in IIIIIIIHII in i mi
3-106 September 1994
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EIA Guidelines for Mining Overview of Mining and Beneficiation
thick with numerous shaly partings are found in structurally less complex parts of this region. San
Juan River region coals are generally subbituminous, but high volatile bituminous coals also are
found.
The Northern Great Plains coal province the includes coal regions that occur in the Great Plains east
of and adjacent to the Rocky Mountains. The area is characterized by little surface relief,, gently
rolling plains, some areas of badlands and dissected plateaus, and isolated mountains. Rocks of this
province occur in nearly horizontal •sedimentary strata which curl up sharply along the flanks of the
Rocky Mountains. Coal found in central Montana is of Late Jurassic age and is high volatile
bituminous containing 1.7 to 4.0 percent sulfur. Coals from north-central Montana are of Late
Cretaceous age and range from subbituminous to Tu'gh volatile bituminous. These coal beds generally
are discontinuous and too thin to be of commercial importance, other than as sources of local fuel.
Coal deposits found hi extreme northeastern Montana and western North Dakota contains an estimated
438 billion tons of lignite, the largest single coal resource in the United States. Coals are Late
Cretaceous to Paleocene in age, and increase westward from lignite hi North Dakota to subbituminous
in Montana. Coals found in southern Montana and northeastern Wyoming are Upper Cretaceous to.
Eocene in age, and range from subbituminous to high volatile bituminous. An 8,000 square mile area
of gently rolling plains in northeast central Colorado are underlain by Late Cretaceous and Paleocene
age coal bearing rocks. Coals generally are subbituminous and occur in lenticular, discontinuous beds
up to 17 feet thick. Extensive deposits of lignite also are found in this region. The coal found hi
southern Colorado is of Late Cretaceous and Paleocene age and range from coking high volatile
bituminous to non-coking high volatile bituminous.
The Interior coal province is an extensive area of low relief underlain by flat-lying Paleozoic age
sandstones, limestones, conglomerates, and shales which lie between the Appalachian Plateaus and the
Rocky Mountains. Coal beds of this province are of Pennsylvanian age, and generally comprise high
volatile bituminous grades which improve in quality hi the western part of the coal region. In
Oklahoma and Arkansas, some coal deposits have been devolatilized to coking low volatile bituminous
and semianthrache ranks.
The Gulf Coast coal province comprises extensive lowlands and coastal areas. The subsurface
generally is composed of unconsolidated beds hi detrital sediments and limestones which dip gently
seaward. Outcrops of rock become successively older inland. The province has a good supply of
surface water and groundwater, and droughts are uncommon except hi southwest Texas. Coal
deposits consist of Upper Cretaceous age bituminous beds near the Mexican border, and extensive
deposits of lignite which extend from southern Texas to Alabama.
The Eastern coal province extends 800 miles from northern Pennsylvania to northern Alabama and
essentially is mountainous for its entire length. Coals of this province were deposited in the
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EIA Guidelines for Mining
11 UN 11,1 I
1 mi inn
i n iiiiiiiii n in nil i in iiiii i inn pi i iiii 11 win p in 111 iiiii i i n 11 n mini in n nil n 111 mini iiiiiiini 11 i mini n i in i mini in in in n in
, i iii iiiiini iiiinin nnnnnnn iiiinni inn in in i in inn inn n nun n i innnnnniinniiiini nun iiiigii nun n iniiininn niiiiniiiiiiiiiiiiiiiiiiiiiiniiiiiiiii nun iiiiiiini iiiiiiiiinni nun iiininn K
Pennsylvankn age Appalachian Basin, which consists of a series of sandstones, shales, limestones,
conglomerates, and coals. Structural features such as faults and fold axes, trend northeast-southwest,
II , . . ' .. '-, 9 , , ' ' • •••: :-", : ! -"; :-: I r-: ! : ,
parallel to the basin margins. The eastern part of the basin is extensively folded and faulted, and
I . * , i ' i • I ' i
contains the higher grade coals of the region. These coals range in rank from medium volatile
bituminous coals of the major eastern Appalachian coal fields to the high quality anthracite of
northeastern Pennsylvania. The western part of the Appalachian basin is marked by strata in broad,
open folds which dip gently westward. Coals of the western part of the basin generally are of the
high volatile bituminous grade. The.ranks of coals in the Eastern Coal Province generally decrease
from east to west in bands which trend northeast-southwest, parallel to major structural features.
Ill 11 I IllM^^^ llllllllllllllIB (i 111 A Nlllilllllf IIIII •Illlill11 •IIIIIIIII illlllilll II I IIIIIIIII |l|||l|l ill IIIII Illlllllllllllllli 111 nil 11 lilllln illlllilllllll i 111 IIIIIIIII Ililllllin^^^^ lillllIM^^^^ 1 I I I |
3.4.13 Trends
Trends in the coal industry are primarily driven by a change in the accessibility of eastern and
western deposits and trends in the use of coal as a fuel, particularly in light of the Clean Air Act.
These trends are
4. :•
in the continued development of large, western surface mines as major
suppliers of coal, while underground techniques are being more widely applied hi the east and
midwest. The demand for the low sulfur coals that are common throughout the west and the
desulfurization of high sulfur coals for .use as boiler fuels is produced by increasingly stringent
limitations on stack emissions on sulfur dioxide and participates.
The coal industry will likely continue to grow at moderate levels within the foreseeable future.
Whether the trend in increasing production from western operators continues may be based on the
demand for clean burning coals. Western coals typically have lower sulfur concentrations and hence
than eastern coals. Howev
ite and subbituminous coals of the west contain
fewer BTUs and carry increased transportation costs (either for the coal or for electrical power).
Production trends hi the surface coal .mining industry include (1) shifts of mining activity to coal'
regions which contain large reserves of economically recoverable and usable coal and (2) shifts of
mining activity within regions to situations which previously were avoided because adverse
overburden thickness, or other factors precluded an economic return on investment in
' • ironing operations. • ' "; •
'
"I™™™ .:::,. :!!:::::::::z::::::^^ i;;
factors in addition to the low sulfur content have contributed to the dramatic expansion of the
•-•- '-— ==- 1==-- abots of relativel flat land "
»•"< i * » thick, horizontal seams, are amenable to Ugh production surface mining operations. The pit, spoil
piles, haul.roads, and ancillary facilities can be designed to minimize the cycle times of unit mining
; -. operations, thus maximizing productivity per shift.
Operators of eastern surface mines use such methods as mpuntaintop removal combined with head-of-
I hollow fill to offset ih dgadvan|ages of surface mining in steeply sloping terrain. Although the
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September 1994
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EIA Guidelines for Milling . Overview of Mining and Benefication
extent and magnitude of their environmental impacts have been controversial, mountaintop removal
and head-of-hollow fill will continue. The east has also demonstrated an increase in the number of
underground mining operations to address the limitations established by topography and economics.
3.4.2 SURFACE MINING SYSTEMS
Surface mining systems are sequences of unit operations which have been designed to accommodate
the limitations on mining imposed by geology, topography, and regulatory requirements. Three kinds
of surface mining systems are employed in the removal of overburden and coal extraction. Area
mining and contour mining are by far the most commonly used methods, the third surface mining
technique, open pit mining, is used to a limited extent in southwestern Wyoming.
3.4.2.1 Area Mining
Two forms of area mining are conducted, conventional or strip mining, and mountaintop removal.
Strip mining is employed throughout the United States, primarily in the large mid-western and
western coal fields and to a more limited extent in the Eastern coal province. This type of mining is
applied in regions with flat to rolling terrain where the coal seams lie horizontal or nearly horizontal
to the surface. Overburden in these areas is relatively shallow and regrading to approximate original
contour is possible. Mountaintop removal is used in ragged terrain of the Appalachian Mountains,
where regrading to approximate original contour may not be feasible or desirable. Both methods
. essentially result in total recovery of the mined resource.
A typical strip mining operation proceeds in the following manner (see Exhibit 3-16). A trench (box-
cut) is excavated through the overburden to the coal seam. This trench usually is extended linearly to
the perimeter of the permitted area, to the edge of the coal deposit, or to a location that
accommodates future development of me mine. The mined overburden (spoil) from the box cut is
stockpiled parallel to the trench on unmined ground, and coal is recovered from the exposed seam.
Successive cuts are made parallel to the initial trench, and spoil from each succeeding cut is placed in
the trench of the previous cut. Spoil from the initial cut is typically placed in the trench of the final
cut. The disturbed area is progressively regraded to the approximate original contour and reclaimed
as mining progresses. As required by SMCRA, approximate original contour requires the elimination
of all highwalls and other mining-related escarpments and depressions not needed to facilitate
revegetation and reclamation of the disturbed area.
The mountaintop removal method (Exhibit 3-17) does not return the mined area to the approximate
original contour as an entire mountaintop is typically mined through. This type of operation often
makes use of a head of hollow fill to handle the box cut spoil and any excess overburden. To initiate
a mountaintop removal operation, a box-cut is made through the overburden along a line more or less
parallel to the coal outcrop. This cut is made in a manner such that at least a 15-foot-wide barrier of
3-109 September 1994
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T"
Overview of Mining and Benefitiation
EIA Guidelines for Mining
iiiiiiiiiiiiiiiii
I'lH
....... Ill
Exhibit 3rl6. Area Mining With Stripping Shovel
STRIP BENCH- — _ —
: • I i
m^^itmm iniiiiiii i mi iiiiiiiiiiiiiiiii i n iiiiiiiiiiiiiiiiiiiiiiiiiH^^^^ iiiiiiiiiiiiiiiiiiiiliiii1
IIIIIIIIIIIIIIIII 111 Illllllllllllllllllllllllll IIIIIII I IIIIIIIIIII I III IIIIIIIIIIIIIIIII IIIIIII IIIIIIIIIII IIIIIII llllilM .
3-110
September 1994
^^^^ lllliilliIlliIllllilllllIlM
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EIA Guidelines for Mining
Overview of Mining and Beneficiation
Exhibit 3-17. Mountaintop Removal With Head-of-HoIlow Fill
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Overview of Mining and Benefitiation
EIA Guidelines for Mining
coal seam at the outcrop remains undisturbed. This "bloom" or "blossom" of undisturbed coal acts
as a buttress to help stabilize spoil slopes during mining operations and subsequent reclamation. Spoil
from the initial cut is transported to the head of hollow fill or other approved stockpile area.
Successive cuts are made parallel to the initial cut, and spoil from each successive cut is stockpiled in
the trench of the previous cut. Final stabilization and revegetation of the mined area can result hi flat
to gently rolling terrain suitable for various uses.
3.4.2.2 Contour Mining
i . •
Contour mining methods generally are employed in the mountainous terrain of the Eastern coal
province. Currently, contour mining makes use of one of three methods of operating: box-cut,
block-cut, or haul-back.
Box-cut operations resemble area mines (Exhibit 3-18) but make use of a smaller number of cuts,
progresses across
, bulldozer clears '
l llllllIB Illllllllllll I III Lj ~_ . - - " ' ! I
vegetation from the box cut area and the area immediately downhill. As the initial cut is developed,
|^*£^2i2 SSSii-SSSi 1S5S2SP ** outsI°Pe- Aft** coal is removed from the box cut,
overburden from the next cut is placed in the mined out area. Operation of a dragline to place
overburden into the mined out cut requires the development of a bench on the uphill (highwall) side
of the operation. Operations making use of shovels and front end loaders can move overburden to the
mined out cut without the development of a bench. A barrier of undisturbed overburden at least 15
feet w^de is typically left at the downhfll foot of the coal outcrop.
?Zffi, S2 SLiSEi' i2?£ 2SS H ^?gned P313*161 with me c°al outcrop; mining •
mSt I !«^ die nil within each cut and uphill in successive cuts. Prior to the initial cut, a bull<
u »ii»iiiiji|!i - .. . . . . _•_._. '
road and parallel drainage ditch are constructed along the coal outcrop and the exposed coal is
Often the unrecovered coal seam at the base of the final highwall is mined with augers.
maximum ^^ ^y ^ augerS) ^e ^^ holes generally j^, sealed wijh day or some
nondeleterious, impervious material. The cut then is backfilled with previously stockpiled
2»2?5f2 S £f, IP SS iSSSSSl E S2£fe &), 5i !?ghM'alJs *te eliminated, and (3) toxic and
add-ibrming wastes and unmined,coal seams will not contaminate ground and surface waters with
deleteljious siltation or leaehate. iBackfiU is regraded to the approximate original contour, where
possible. The regraded site is then revegetated with appropriate species of plants and monitored for a
specified length of time to insure success of the revegetation effort. Haul roads are either abandoned
! m »"• af^^blc manner or are stabilized for use during and after reclamation .(Gentry and McCarter,
^992; Grm'anS ISJ 19743.'
i r n
The development of a block-cut contour mine (Exhibit 3-19) is similar to box-cut mining, with major'
differences in spoil handling techniques and the sequence of mining sections. Whereas the box cut
ilinSfi^Sls01161111^ P1006^8 "P and around a mounom m one direction, block cut minjng progresses in
'Sf fejbp^ directions along the coal outcrop. An initial block of overburden is excavated near the center of
' '"3-112
September 1994
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EIA Guidelines for Mining
Overview of Mining and Benefiaation
Exhibit 3-18. Box-Cut Mining Operations
s
i*
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to
3-113
September 1994
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Orerriew of Mining and Benefication
EIA Guidelines for Mining
ill! IIIIIM
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Exhibit 3-19. Block-Cut Mining Operation
. (SkeiiyandLoy. 1975)
'Undisturbed Area
Toosoil Applied /f±
to Final Grade
2nd Step
3-114
September 1994
IlllllllllllllllilliillllilllIB
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EIA Guidelines for Mining Overview of Mining and Beneficiation
the permit area, and spoil temporarily is placed downslope of the coal outcrop, or in a head of hollow
fill. The initial cut is two to three times larger than successive cuts. After the coal has been loaded
out, spoil from the second cut is placed in the trench of the first cut. Because the second cut is only
one-third to one-half .the width of the first cut, spoil from the third cut also can be placed in the first
cut. -The third cut is stripped as coal is loaded, out of the second cut. In some cases, each successive
cut is smaller than the previous cut, minimising the amount of spoil to be hauled to final the cut.
Block-cut mining can also be .applied in area mining (Ramani and Grim, 1978; Gentry and McCarter,
1992). • .
Haulback mining can be used on smaller coal outcrops requiring greater flexibility than box-cut or
block-cut methods. In this method, rectangular pits are developed along the contour of the seam.
The width of the rectangle (pit) is established by topographic or economic recovery constraints.
Overburden from the initial cut is stockpiled in a suitable location. As successive pits are developed,
spoil is "hauled back" to the previous pit by truck, scraper or conveyor. The spoil from the initial
box cut is deposited in the final pit. Reclamation occurs progressively with the backfilling and
regrading of each successive pit (Gentry and McCarter, 1992).
3.4.2.3 Open Fit Mining
The only open pit coal operation currently in production includes a combination of area mining and
contour mining techniques to .recover coal from steeply dipping seams in the mountainous terrain of
the western Wyoming. This operation is classified under the "Special Bituminous Coal Mines"
category by OSM and is subject to special performance standards which closely parallel existing
Wyoming law. Open pit techniques typically defer reclamation until the resource is mined out
completely or to economic limits. This deferred reclamation for open pit methods contrasts with
SMCRA's contemporaneous reclamation requirements.
Equipment selection, spoil placement, and the depth to which coal will be mined are dependent on the
ratio of overburden thickness to coal seam thickness (overburden ratio) and the number of seams to be
mined. Mining usually is initiated in the oldest (lowest) coal seam in the permit area. A dragline or
stripping shovel can be used to cast overburden on both sides of the pit, forming spoil piles on the
previously mined highwall and adjacent to the outcrop of the next coal seam to be mined. Coal is
loaded out with shovels or bucket loaders, and bulldozers reclaim the mined area to a configuration
approved by regulatory authorities. Combinations of scraper loaders and stripping shovels also can be
used for overburden removal.
Coal seams thicker than 70 feet with overburden ratios of 1:1 or less are mined by multiple bench
open pit methods. Emphasis hi the development of this mining method is placed more on proper
sequencing, of coal loading, hauling, and storage techniques than on overburden handling.
Overburden is removed from the initial cut by scraper loaders or a combination of shovels and
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Orcrview of Mining and Benefiriarion . EIA Guidelines for Mining
haulers, and is stockpiled adjacent to the pit. Subsequent overburden cuts are backfilled into the pit
! *S Sipping shovels load coal into haulers for transport to conveyors or unit trains.'' Both of these
••iJlBRfB transport systems' 'can feed preparation facilities or generating plants. ' '
i i ' " ' '
3.4.2.4 Special Handling
|" ' '« '"' ; : : : : : • i . .
If segregation or selective placement of overburden horizons is necessary to achieve rehabilitation of
the site to a particular post-mining land use, a combination of excavators, including scraper, loaders,
draglines, bucket wheel excavators, and truck/shovel operations can be employed. Pit geometry may
I • i . ii
be engineered so that excavators can pass one another during bidirectional mining. It also may be
necessary to place two or more excavators on separate benches to achieve proper location of spoil.
3.4JL5 Equipment
The operational details of surface mines primarily depend upon the excavating, loading, and hauling
• JJ™"'equipment employed at the mine-site. Equipment selection generally is based on the depth aid texture
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of overburden to be removed, the number of coal seams to be mined, the thickness of partings .
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between multiple seams, the friability of the coal seams and die planned geometry of the pit.
; : '" ! ; " ' " "T! ; : ' ' : : ': : ;r • : : • ;
used to remove overburden is based on the above criteria and includes the following,
which may be used alone or in combination: draglines, shovels, bucket wheel excavators, front end
I1 .'.'.«
loaders, scrapers, and bulldozers. Draglines and stripping shovels can be used if the overburden to
be regraded in the mined-out trench orpit can be homogenized during stripping without adversely
affecting the reclamation process. Shovels and front end loaders loading trucks can effectively handle
selective placement in the backfill. (Usually, a limited amount of special handling
' IIIIIIIB lllllllR llllllH^ IIII III - III llllllllllllllIM illllllll 111 Illllllllllllllllll lllitlH ill Illlllll Illlllll Illlllll Illllllllllllllllllllllllll I ••Illlllll I I'lllll Illlllll Illlllll ' II 111111° 111
I a dragline.) Scrapers are effective for removing shallow, unconsolidated
overburden and bulldozers may be employed to prepare for benches or pads for draglines.
Coal is transported from the mine she to cleaning plants, transfer points, and consumption points via
^ i ii i i i 111 i i i
trucks and conveyors. Trucks used for coal hauling range in capacity from 25 to ISO short tons, and
. Mobile conveyor belts are used hi some larger mines to
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Permanent conveyors can be employed to transport coal from truck dump
iii iii i iiii 11 iiiiiiiiiiiiiiii iipi in
points to cleaning plants, railheads, barge points, and consumption points.
• ' :' ' '• : ' , .. .... ! ,il ''
3.43 UNDERGROUND MINING SYSTEMS
Underground mining systems range in complexity from conventional drill-and-shoot operations to
IIIIIIH IIIIIIH Illlllll Iliil Illlllll IIIIIIIH^^^^ Ml Illillill Illlllll III lilldl 111 Illlllllllllll Hill Illlllll
fully automated longwall systems. 'Summary discussions of mining systems (DOE, 1978; EPA, 1978,'
1976d, and' 1975) and comprehensive texts' (Britton and Linebeny, 1992'; Hittman Associates,' Inc.,
III Id ill Illlllll Ililllill III inillUli iillllillllllllllllllllllllllllli Illllllllllllllllllllllllll n Illllllllllllllllll III III 11 iiilnll II IIII IIII PP illiiill IIIIIIIIIIIII HI Illllllll hi
3-116 September 1994
Illllliii'i I' LI, 111(11(11 1 Ill) Illlllll 11 i"l In llNlilii '111 Wl I' IIII I. IllliH II ,"111 ill" nil Ullllll" •ill Mi Ill (11 ilnHli i Iil HI II",!,11 Ill "Ill I' ' Illllll hi J • mil •Jkl MINIM i nll'il 11 '• II' 1 I'* •111 1 1 ,n «ill ' lA III" U, 111 I if .ft ip
! | ilB11!1! ! Ill ! I || HI1! I I I! I I I I I11! ! R | I! ii I I1! I I'l11:1! SB IS1! I! ,'"!'"! I1"!1! !"!! , I"! i I Ill I I1!"! '
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EIA Guidelines .for Mining Overview of Mining and Beneficiation
1976) describe in detail the technical aspects of the development, operation, and abandonment of
underground coal mines. This section presents an overview of underground coal production methods,
including a brief discussion of each production method, and a general discussion of the environmental
impacts typically associated with underground coal mining,
As stated previously, underground mines account for approximately 40 percent of domestic coal
production. The majority of mis production comes from operations using room and pillar methods.
Longwall mining operations account for approximately 25 percent underground production. Shortwall
minrng techniques are employed but only to a limited extent (McElfish and Beier, 1990).
The following presents descriptions of underground mining systems using the minimum level of detail
necessary to identify the sources of potential environmental impact associated with underground coal
mining .' . .
Lite new operations hi other mining sectors, opening a modern underground coal mine represents
planning, development, and intensive capital investment for several years preceding the profitable
production of coal from the mine. Underground mines are significantly more expensive to develop
and operate than surface mines. Therefore they usually are planned for long-term operation in coal
seams that are not recoverable economically by surface mining methods alone.
The considerations necessary to put an underground coal mine into production, including
development, ventilation, roof stability, and moving the coal from the site of extraction to a loadout
or cleaning plant, are similar to those of-other underground operations as discussed above hi Section
3.1. The buildup of methane gas within the mine workings is an additional concern unique to
underground coal mining; additionally, in some circumstances, subsidence tends to be a greater
problem than in other underground rnining operations. This discussion will focus oh those aspects
where underground coal mining techniques differ from those employed at non-coal operations.
3.43.1 Development
The development or construction of an entire underground coal mine may take decades, and
extraction may commence in some parts of the mine years before development begins in others.
While mine development is underway, the some coal may bee produced, however, the extent of
production may be-minuscule compared to. the annual tonnages produced during full scale operation.
Plans for mine development and extraction may change radically after mining commences, based on
the availability of capital, innovative technology, and markets. However, after a operating plan has
been approved and a permit issued, these types of changes must be approved by OSM or the State
regulatory authority as amendments or revisions to the current permit.
3-117 September 1994
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I llllllll
II * ' I k
• , • - ' j-
of Mining and Benefication ' EIA Guidelines for Mining
Mine development generally includes a standard set of operations beginning with the esteblishrnerit of
2^4^ ..... techniques ...... ' ..... ' ............
................... ..... ,: ............... ,,, ...... ...... ....... ...... -, ...... ...... , ...... s,,0.!!^^?, sitng
Tnadimery is" Used further develop entiyways 'and crosscuts, producing a hpneycornb of unexcavated
c031 ^nd voids. The configuration of entryways and crosscuts depends on the strength and thickness
of the coal seam and oy^urden, ........ the ..... amount ....... gf_subs|dence permissible, and the inernod used for
recovering the coal (Britton and |Jnebeny, 1992; Hittman Associates, Inc., 1976). Roof control
systems are installed within the entryways and crosscuts. The specific method used for roof control is
..... Jjgjga ..... .ills ..... §S2££2ZJ2£S2! ....... != ...... S ..... 8555 ..... *5H£*2£ ....... d®Y?!°!»n5n!: ................ ISfe Pr°Ps> trusses,
s are used to prevent roof falls.
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Juubge, and electrical systems are installed as development progresses. One function of
!,|a§2>2 ofjjHJais and barriers is to minjmfze the cost of providing adequate ventilation to all
areas of the mine. A minimum number of entryways and crosscuts also is necessary for
rapid and efficient transport of coal from work areas.
spptapnate for an individual mine is determined on .the basis ' :
tftbe overburden^ sa&tv^recjjuirenient^ conservation practices, and workspace needs
In fl» jdeal situatioiij entryways and-crosscuts are .advanced through the coal seam to
be mined. Coal then is extracted from pillars and longwalls in retreat
fej ....... in ..... tte ...... diregtios ..... opposite to the development advance).
' '
r°Pf properly, a generaUy symmetric system of pillars, barriers, abutments, and ribs
j ..... until ...... the ...... wttraction phase commences. The dimensions and geometry of
unexcavated features generally reflect men-.intended life spans and purposes, as weU as the strengths
i Snd Sfcgl^?1 PJtpf??!"? of the coal seam^and pveAurden, ;
f
IS: ...... °£ ..... 525 ...... 3S2*SX*-
at an
Jjf choice of vertical shaft versus sloge entryway usually depends on the proposed size of
-' 3.43.2 Extraction
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is driven into a coal seam
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: 552J2I: 25EE *°I, 5SE !!2E!°P!!!E!5 55d, coal production are chosen
,E?l, ,5???? .variables:
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„ B. September 1994
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EIA Guidelines for Mining Overview of Mining and Benefication
• Seam height, which determines one economic basis for choosing a mining system.
Conventional mining systems become less efficient as seam height or thickness increases.
Longwall mining systems are impeded by variations ha seam height.
• Bottom quality, which ranges from excellent (dry, firm, and even) to poor (wet, soft, and
pitted or rutted), and affects machine operations by limiting traction and restricting
maneuverability. '
\
• Roof quality, which limits the amount of coal that may be extracted from the without
artificial protection against collapse of the mine roof.
• Methane liberation, which in some seams occurs at a rate proportional to the rate at which
coal is cut or sheared from the working face. Methane accumulates and sometimes ignites
hi underground workings when it is not removed by the ventilation system. Methane
accumulation is monitored at least once every 20 minutes at the seam face, causing
disruption of otherwise continuous work cycles.
• Hardness of seam, which primarily affects the choice of coal cutting equipment.
• Depth of seam, which determines the response of the overburden to excavation of the coal
seam.
• Water, which may infiltrate the underground workings through channels, fractures, fissures,
or other water transmitting voids in mine walls, roof, and bottom.
Conventional (drill and shoot) mining systems utilize five categories of unit operations (Hittman
Associates, Inc., 1976) which can proceed simultaneously at separate working faces. The categories
include:
• Cutting a slit or kerf along the bottom of the working face across its full length
• Drilling a pattern of blast holes into the working face
• Blasting the coal with chemical agents or charges of compressed gas
• Loading and hauling the fractured coal from the face to a centralized crushing and loadout
facility for shipment to the cleaning plant
• Roof bolting with rods, trusses, props, and bolts to ensure the safety of underground
personnel and to minimize the deterioration of roof conditions before a mining section is
abandoned.
A typical sequence for mine development and extraction with conventional techniques is shown hi
Exhibit 3-20. The flow of work depicted hi the figure is from right to left. Each numbered panel
represents an approximate 3 m (10 ft) thickness of coal to be extracted. ,
3-U9 September 1994
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•illllllllll
^
Overview of Mining and Beneficiation
• iiii 111 iiliilii mil in nil n i n iiiiiiii n in iiiiiii
EIA Guidelines for Mining
Exhibit 3-20. Operations in Conventional Room and Pillar Mining
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EIA Guidelines for Mining Overview of Mining and Beneficiation
The cycle of unit operations in Exhibit 3-20 starts with coal loading and ends with roof bolting. After
the coal is loaded from Panel 1, the bolting crew moves up to the face of Panel 8 to secure the roof
over Panel 1. A coal cutting machine then is moved or trammed to Panel 8. A cut 3 m (10 ft) deep
is made in the coal seam with the machine-mounted blade, which is extended into the seam from the
stationary machine. The cutting blade is inserted into the base of the coal and is traversed across the
width of the panel (usually 6 m or 20 ft); the blade produces a narrow kerf, or slot along the base of
the recoverable coal. .
After the cutting machine is trammed to the next panel (panel 9), the drilling crew cuts a specified
pattern of blast holes into the face of Panel 8. The holes are loaded with a blasting agent and then
shot, exposing the working face of Panel 15. The cycle at Panel 8 then returns to loading,, and the
coal is removed from the face area ahead of the bolting crew.
Continuous mining systems generally employ fewer workers per face and produce more tons per
worker and per shift than conventional systems. The efficiency of continuous mining systems remains
essentially unchanged with increasing seam height. Conventional systems reach a point of
diminishing return as seam height reaches 1.8 m (6 ft).
Continuous mining systems use machinery to extract coal during room-and-pillar, shortwall, and
longwall operations. Machinery and panel configurations are chosen within the constraints of the coal
seam variables described previously.
Continuous room-and-pillar operations are based on the capabilities of coal cutting machinery to
combine the unit operations of conventional mining techniques (cut, drill, shoot, and load) into one
continuous operation; roof bolting may also proceed in conjunction.(and slightly behind) continuous
mining. The operation may be halted periodically for methane checks and the installation of
electrical, conveyance, and ventilation services. Coal is cut from the face with cutters, borers,
augers, and shearers that direct the cuttings to conveyor belts mounted inboard on the machine
assembly. These inboard conveyors feed the coal to the mobile conveyor belts, shuttlecars, or load-
haul-dump (LHD) vehicles that transport the coal to the permanent haulage system, which may be
another conveyor or a tram of mine cars pulled by a locomotive.
Longwall mining systems employ one or more parallel entryways. located approximately 90 to 180 m
(300 to 600 ft) apart arid connected by a cross cut (Exhibit 3-21). The equipment necessary to
conduct the operation including the cutter, conveyor, shield, and roof supports are inserted through
the crosscut. Coal is sheared or planed from the face and then directed onto die conveyor, which
feeds the coal to a semi-stationary haulage system located in an adjacent entryway. Roof supports
advance toward the cut face faydraulically, leaving the roof of the mined area (gob) to collapse as the
3-121 September 1994
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• Overview of Mining and Benefidation
Illllllllllllllllllllllllllll11 Ul""l IIIFFI I f FI'FI'I'I1 ln m^HmL*H*u*l***am***^—im*^^^^^^^^^^^^^^^^^^^^^^^^^^^^^—
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Exhibit 3-21. Longwall Mining System
3000-2 miles
i
Collapsed Roof
Coal in Place
Mining Machine ("shear" or "plow")
Hydraulic Roof Support
Entry
1
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3-122
September 1994
iiiiiiiiiii
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EIA Guidelines for Mining . Overview of Mining and Beneficiation
unsupported overburden subsides into the mined-out chamber. When longwall mining methods are
used, there is a clear potential for surface subsidence, as described in section 4.8.
Longwall systems are typically applied in situations where uniformity exists throughout the coal seam
in terms of height, bottom and roof conditions, hardness, and areal distribution. Longwall mining of
multiple seams is possible under some conditions. Shallow seams are mined first, followed by
progressively, deeper seams. Overburden structures and lithologic characteristics influence the rate
and form of the resultant caving and should be considered in the design/development phase.
Longwall mining systems offer the following advantages over other mining systems (DOE, 1978):
• Lower cost per ton of coal produced
• Higher productivity per worker hour .
• Higher percentage of recovery of coal resource
• Predictable subsidence
• Adaptability to thick and multiple seams
• Capability to mine at great depths.
Shortwail mining systems are similar in principle to longwall systems. During shortwall mining, coal
is cut from a panel approximately 45 m (150 ft) long. Roof supports advance toward the panel as
mining progresses. The unsupported, undermined areas subside into the void behind the advancing
roof supports. The panel length is short enough to be worked economically with the .conventional
mining machinery used in room-and-pillar systems, although automated shearers also are available for
shortwall systems. .
Shortwall systems can be used to change existing mining operations from room-and-pillar techniques
to wall-type mining techniques without additional costs for the replacement of machinery or revision
of plans for mine development. Advanceable roof supports may be the only additional equipment
required to consummate the change-over. Shortwall operations also offer the advantage of flexibility
in selecting the locations of mining panels or walls to minimize the interruptions in production that
result from changes in seam height and the presence of want areas, unsuitable roof and bottom
conditions, and gas and oil wells.
3.4.3.3 Abandonment
The techniques that are appropriate for the abandonment of an underground mine generally reflect the
manner in which the mine was developed. Water infiltrates to the mine void through overlying and
adjacent strata. Drift entryways that are advanced up the dip of the coal seam will allow this water to
drain freely from the mine, unless suitable seals are installed at the drift mouth. Entryways that are
advanced down the dip of the seam must be pumped during mine operation. After abandonment,
3-123 September 1994
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,' "„ I1
Overview of Mining and Beneficiaiion
EIA Guidelines for Mining
ITlllii'l 1
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water drains to the depths of the mine, forming a subterranean pool that may slowly drain to the
surface through channels, fractures, and other small voids.
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of seals frequently are installed at mine openings during abandonment:
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* Dry seals to prevent the entrance of air and water into mine portals where there is little or
minimal potential to develop hydrostatic pressure against the seal.
T|rseals'i) re|pce the flow of air into the mine while allowing water to drain from the
mine, Even these mines can still "breathe" through minute cracks and fissures because of
contmued changes in atmospheric air pressure. Enough oxygen usually is available under
these conditions for formation of acid drainage if sufficient pyrite and water are present.
Hydraulic seals which plug the discharge from flooded mine voids and exclude air from the
mine, thus retarding the oxidation of sulfide minerals.
Hydraulic seals may be employed to seal the drift mouths of entryways that were developed up the
:6°
| of concrete block, backfilled material, and grout curtains injected through boreholes from the
"~ " " I tffihnfques and others are thoroughly described hi other EPA
- =•• = publications i(EPA,. 1973 and 1975).
11. " ,»!, i * , „
2lES££S iHY£ !SS SSlSJl poUution control techniques used in the surface coal mining
™= industry. Evolving technologies include:
Alternate mining methods, emphasizing controlled spoil placement and reclamation
'"« 5 !'""" !!' « I! '" W1. • " S • * *
conoirrent with extraction
* Sastewater treatment systems, emphasizing innovative techniques to replace limestone
^ "Stoent ponds, both .of which suffer from reduced
iiiiiit «^^^^^^^^
IH^^^^^^^^^^^^^^^^
ions
!TiiiiiliK
» gnipnasiTlng the replanting of reclaimed areas with plant species
been,spec1ally bred for replanting of local minespoils
s emphasizing (1) the use of soil mechanics in slope design, and
soJlTOvering agents such as stubble mulches, cover crops, artificial soil amendments
.*. ,._...., ... prevent ^{j 3^ water erosion of recently backfilled
or temporarily stockpiled soils.
IIKlLillllli :ll!'l I'l'li'llliI'liiiiillili'iiainllJ.,'< 7"PIIIIIIPIilBlllllllllllirli'liI11)"'i'
111 laiiiiiiiiiiniiiiLiHiii
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. EIA Guidelines 'for Mining . Overview of Mining and Benefication
3.43.5 Environmental Effects . . •
The physical disturbance associated with surface coal mining and the surface aspects of .underground
mining are the same as those of other mining sectors. Surface disturbance reduces the cover and
primary productivity of the land. The loss of vegetation cover results in an increase in erosion and
without adequate control, sediment concentrations are likely to increase in nearby streams. Ground
disturbance and constant movement by vehicles also increases fugitive dust carried in the wind. .
Wildlife habitat is lost at least temporarily with surface disturbance while noise and human activity
create additional impacts in the immediate vicinity of mining operations. Although these impacts are *
to be expected with any mining or other surface-disturbing activity, they may be particularly acute
when mining operations are being conducted on adjacent parcels of land over an extended period of
time. • •
Other environmental effects resulting from coal mines depend on the nature of the operation (surface
versus underground) and to some extent, its location (east versus west). In addition to the surface
water impacts associated with most mining activities, surface coal mining operations may also impact
groundwater. In the east, particularly, acid mine drainage remains a problem .despite developments in
the technology surrounding prediction and control. Acid mine drainage is discussed in Section 4.1
and will not be discussed further here. Subsidence is a response to underground mining activities.
Although concentrated in the east and midwest, impacts from subsidence have also occurred in
Wyoming and Colorado. A discussion of subsidence is presented in Section 4.8.
The extent of impacts to groundwater depends primarily on the premining hydrologic system and the
chemical constituents of the overburden. As with other forms of surface mining, the geologic strata
overlying the coal (or ore) are removed during extraction. Non-coal mining operations typically store
this material in waste rock piles outside the pit while coaj mining operations are required to place
overburden back into the mined-out portions of the mine. As overburden is placed into the pit the
hydrologic setting is changed from consolidated, heterogeneous strata to a highly permeable,
homogeneous mass. The groundwater level and flow rate can be affected by the increased
permeability of the backfill in the pit. The potentiometric surface will eventually stabilize, however
the new surface may not reflect the premining water level.
3.5 COAL PROCESSING
3.5.1 BASIC PRINCIPLES
Coal preparation is a-critical technology supporting both the mining and end-use of coal. The output
of a coal mine consists not only of coal but also non-combustible mineral matter. This mineral matter
ranges in size from large rocks to extremely small grains dispersed throughout the coal seam. The
primary objective of coal beneficiation is the separation and removal of mineral matter from coal to
3-125 September 1994
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Overview of Mining and Benefldation ' . . EIA Guidelines for Mining
, ..... i ............. ' ......... ::„ ....... lEiiB^^^^ ............. in ..... 11 ....... Si ......... NIK ..... . ....... i ..... iiiiiiii: ...... • ..... liiSid^^^^^^^^^^^ ....... 'Hans ......... :^,iii.ii:!!:S!i,i!!:!iii. ..... :,: ....... :;i,,i ...... i:!)!:^^ is.it ....... Is ..... ±!]i!!!ii ...... sill
• .
qj'jjg hoacng in the biler
JBurning coal with less ash increases boiler efficiency, boiler capacity, plant availability, and net heat
ratCl, Reductions 'in auxiliary power ronsinnption, fo^gd ..... outages, ..... partialSe^e^sloK^ ...... aid ....... capital
costs of new power plants all accompany the use of lower ash coals. Additionally, as-mined raw coal
often fluctuates in quality and this is detrimental to boiler operation. Coal beneficiation produces a
..... ..... ...... ...... ....... ..... ...... ........
Concerns over the .environmental effects of coal bunung expanded the objective of coal beneficiation
to include removal of inorganic sulfur in coal. More recently, researchers are examining coal
..... '
........ IflllViiSllSIBlplllllSllliliaHill'lllll'iiywhlll!1' ........ ifiinr vm ............. ll!!!1!11!!?!!!'"'!!:-''!!!!!!!!!11' ........
preparation as a means of reducing air toxic precursors. As New Source Performance Standards
(NSPS) were developed for coal-fired utility boilers/advanced coal cleaning technologies were "
simultaneously developed to remove 70 to 80 percent of the pyritic sulfur present in cod and recover
li^ ;
provided further impetus for coal preparation. Utilities could now choose between several compliance
options such as switching to premium low-sulfur coals, emission allowance trading, or post-
™r™^ ',::;,:,:;::::: "ii:
combustion clean up. Risk averse utilities could choose to pursue a mixed CAA compliance strategy
because of the volatility of stand-alone •strategies. Cod preparation became another viable option to
meet compliance regulations by its ability to convert high and medium-sulfur/ash coals'to low-sulfur/
,,mJn?Ii?l,,,,ma!ler, f*°m ?*w,594 a*6, numerous and the •
configurations in which they are used hi cleaning plants can be complex. Despite the complexity of
actual operating plans, there are only two underlying principles upon which all physical cleaning
plants operate: (1) differences in specific gravity between the organic, combustible matter and the
1 "• ' ,: ,!:!"!!" ,!l!"ii,l : ' ' * „ ' "" • , ,,',,. • , ,' :,,,• , „ „' „„ |, , ,, „ ',„.•„
mineral matte£ present in coal, and (2) differences in surface properties between organic and.
matter'. Conventional coal cleaning processes are bas^i on-the" former principle, -whereas
advanced cleaning processes are based on the later principle.
Conventional coal gleaning involves the immersion of raw coal in a medium that simulates a
: Jblib;
sgeclfic giiviy. -The lighter material is removed as a clean "float" product, while the
""iaviCT material or "stok" ^rejected as refuse. The majority of coal mined inthe United States is
c|e|SM BiSg tfiis^ jplriicipie. A^small percentage of coal consisting of very fine particles-hi the raw
; =P£^ 2522! 5* £!??22! 22S gawS^nKthods. iWithi fine particles m aqueous 'systems, surface
forces become comparable with gravity forces and hence, gravity-based separation becomes
ineffective. Consequently, these fine particles, being only a small portion of the raw coal, are usually
- discarded. Alternatively,, a technigue taown as froA flotation inay be used to clean these 'fine
particles. Unlike specific gravity separation wnlch exploits differences hi the specific gravities of
particles, froth flotation is based on differences hi the surface properties of coal and mineral matter.
Coal surfaces are typically hydrophobic but the surfaces of the refuse material associated with coal are
HIP iiiiiiiiifipiin i,, iiipini, i' iiiiinipi,' ihliiiitii 11 iiipiii "i1 p i' i IP i nippipppi HUP iniipi j ppiinninii 11 iihiiiiiiiiniPiipp iiiiinii PIIMPIIIPIIIIII i , pi iiiiiniiiipiy 11 h i iiiiiiipip'iiiiiiiiiiii
iiiiiiiiiiiipijiii1 iiiiiiii'iii ''in iikii iiiiiiiiiiiiifii ill iiiiiiiiiiiiiiiiii iiiiiiiiiiiiiii iiiiiiiiiiiii i iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiR iiii'iii," n r 'nil 3-126 September 1994
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EIA Guidelines .for Mining Overview of Mining and Beneficiation
hydrophilic. By passing air bubbles through a coal-water suspension, coal and refuse particles can be
separated; the refuse material sinks while the air bubbles attach themselves to the coal particles and
buoy them to the surface where they are collected in a froth.
The actual process of separating raw coal from its associated impurities, using either the specific
gravity separation principle or froth flotation, is only one of the four processes that coal cleaning can
involve. The other three processes are crushing, screening, and dewatering. Crushing serves to
break down large heterogeneous particles into smaller, purer particles prior to separation. The extent
to which crushing can liberate coal from impurities depends in large part on the depositional
characteristics of the coal seam. For example, if the impurities are finely disseminated throughout the
seam, liberation may be relatively difficult. If, on the other hand, the impurities exist as thick bands
of rock within the seam, with weak bonds to the coal, then the raw particles will tend to break along
the weak bonding planes during crushing, resulting hi extensive liberation of the coal from the rock.
In any event, the success of the subsequent separation process depends hi large part on the degree of
. liberation achieved through the crushing process. All particles must report to either a float or a sink
fraction during the separation process; thus, the existence of heterogeneous particles means that the
clean float particles will contain mineral impurities, and the rejected sink material will contain coal.
Coal cannot be completely liberated from its associated impurities through crushing—some
heterogeneous particles will remain. Whether any given heterogeneous particle reports to the float or
sink depends on the overall specific gravity (or, in the case of froth.flotation, the overall hydrophilic
tendencies) of the particle. .
Following crushing, but prior to separation, the raw coal is typically screened. Screening is used to
divide the raw particles into pre-defined size ranges. The various types of equipment used hi the
separation process typically achieve maximum efficiency when processing feed of a relatively
.uniform, narrowly-defined size range. For example, equipment based on the specific gravity
separation principle fails below a mhiimnm particle size; for coal particles this is usually 25 mesh
(575 microns) or 100 mesh (149 microns). For finer particles froth flotation must be used. Thus, the
separation process typically consists of two or three separate circuits, each using a different equipment
type designed to handle a specific size range of particles. Screening is used to direct the raw coal
particles to the proper circuits.
Finally, after separation, the clean coal and refuse are generally dewatered. Moisture, like ash and
sulfur, is an undesirable impurity; through the dewatering process the moisture content of the clean
coal can be reduced. .
A perfect separation of coal from its associated impurities is not possible using either the specific
gravity separation or froth flotation. This is because, hi practice the separation process is
3_127 September 1994
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Overview of Mining and Benefiaation
EIA Guidelines for Mining
fundamentally stochastic in nature. _ As mentioned earlier, some composite particles consisting of
and coilwllremaineven iaSecushin.
• l llnlllll ,, , 'Ijj,
Sulfur occurs in coal in both pyritic and organic form. Pyrite is a mineral that is not an integral part
of coal, but is normally associated with it. Hence, it is possible to separate coal and pyrite using a
I J ! : i, ; sti ; !:!! £ ; ;; _ ; 1 ; l ; ;_ , ;_ ;, ; i , fi ;. CIS.
echmque. Organic sulfur on the other hand, is an integral chemical component of
I separated through physical cleaning.2
^amount
sulfur that can be removed from a given coal through physical cleaning is equivalent to the amount of
Sills oi^urring in pyritic form. ' ' •
, I ; iW liyi'
'
if. 'IHf
degree to which the separation tails short of perfection is dependent on the raw coal qualities, the
-ami 5
cleaning equipment used, plant operating conditions, and the washability of the coal. ' Coal
waspjabjj[t£ canjjejrou^£ defined fajenns of the degree to wh^ a coal'can ^ gg^g^ fjouj ^
assc>ciate4',,,,impuritiesl' . ' •
lull giii ill
Raw goal, feed consists of particles combining coal and impurities in various;
iiiiiiiiiii
lii iiliii lilllf lilllil
tions; thus, the
particles cover a wide spectrum of specific gravities. The washability of a coal defines this spectrum
•
and consists of the percentage (or cumulative percentage), by weight, of the raw coal comprising
contiguous specific gravity intervals, along with the quality (Btu, sulfur, and ash contents) of each
gravity fraction. Exhibit 3-22 is an example of washability data for a sample of a
btaminous, high volatile A coal from the Pittsburgh bed in Jefferson County, Ohio.3 The data are
divided into three size ranges of coal. • Within each size category, the percentages (by weight) of the
(l83i ..... ,5J£ ..... it5^6® gravities less ....... than 1.3, 1.4, and 1.5 are given (e.g., 48.6 percent of the raw •
x, ...... lOg ..... irneshi ...... size, ..... |ange has a specific gravity less than 1.3).- ' Also, the Btu •
previous example, that portion' of the raw coal with a specific gravity less than 1.3 has a" Btu "
14146 '
sample of coal is collected, crushed 'to a given
organic liquids possessing^ definite, precise* specific gravities. The material that floats at each
to
ions example, 48.6 percent of the1V6 inch x 100 mesh sample floated when place in a liquid
j
^'illWIlHt:!' 'J;:!1!11'1!!)'!;
9111 be removed through chemical cleaning. However, chemical cleaning is not a commercially viable
! ' "
ililii?l,,;PP|S«^M:United .States Coals, Vol. 1, p. 395, Eastern Region, U.S. Dept of Energy.
September 1994
n, '^niii iiiiiiiiiiiiiiiiiiij .IHTI
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EIA Guidelines for Mining
Overview of Mining and Benefidation
I
•e
I
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3-129
September 1994
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Ill III
111' Ill
nf Mining and Beneficiation
EIA Guidelines for Mining
witii a specific gravity of 1.3; this "float" had a Btu content of 14,146 (per pound basis). The
specific gravity of the bath (1.3 in the example) is referred to as the specific gravity of separation.
i ' ,,,,|"
i, •' ..... ' ' " '
1 Commercial cleaning plants achieve gravity separations by employing various techniques (including,
e.g., suspensions of ground solids in water) to simulate the heavy liquid media used in the laboratory.
The behavior ..... of a coal ..... sample ..... in ..... a ...... laboratory ..... bath, as ..... measured during ...... washability tests, ....... provides ..... a ...............
. .
..................... • ........ theoretical ..... limit ..... of how the coal will behave in a commercial' cleaning plant.4 Washability data, like
those presented in Exhibit 3-22, are used to estimate1 the yield and clean coal' quality for a given coal
cleaned at a given specific gravity of separation. For example, if the 1 1A inch x 100 mesh coal from
the earlier example is to be cleaned at a specific gravity of separation of 1.6, Exhibit 3-22 predicts
basis), an ash content of 7.5 percent, and a total sulfur content of 2.54 percent. Commercial cleaning
plants rarely reach these theoretical levels of product quality. Computer models for simulating coal
^™| preparation can' be used to estimate commercial plant performance.' Such"models use washability data
to predict the yields associated with cleaning various coals to meet predefined quality specifications.
Hi !• ill! Ill lil . . 1^^ mifi Plilllll Ill* Kill! illillV 1 • I •Ill I'n'l
An important characteristic of all washability data is this trade-off between coal quality and quantity.
From Exhibit 3-22, for all three particle size fractions, Btu content increases and ash and sulfur
nn mini i mm mi i mm mini i in mini nn inn in
, „ .
• The common way of assessing or evaluating coal cleaning systems that use gravity separation
techniques is to determine the sharpness of separation achieved. This is done using partition curves.
The partition curve of any given equipment that separates coal and mineral matter is essentially a
............................................. ............ i ................. ..................... histogram of the distribution of coal groups of different densities hi the product. Typically the
......................... " ............ ............. ' .................................. histogram is represented in the form of a cumulative curve with the partition coefficient on abscissa
U *
................... iii [[[ in the curve is parallel to the abscissa at the density of separation . The partition curve is typically
•ii^ characterized by two parameters dp and e,. d. is the relative density corresponding to partition
III Wlllllllllllll I Illilllllllli I II IIIIIIII IIIIIV Illllnl III illlllllllllll llllllllllllllllllllllllll llllllllllllllllllllllllllllllllllllilliiiimll lllllllllllllllllllllllllllllllllllllllllllliii i Hiiiiiiiiiiii nn 1 1 innnnnnnnnnnnnnnmnn mm i innimiiiiiihn mm " i* t*
........................... ; [[[ coefficient 50. .............. This is ...... the relative density at which an infinitesimal increment of raw feed is equally
i ............... in
content decrease as the yield decreases. Thus, improvements in coal quality can be obtained only at
the expense of reductions in yield; this is true of all coals including the sample represented in Exhibit
3-22. Not only are mere technical limits to the percentage of ash and sulfur that can be removed
from coal through cleaning, there are economic limits as well. For example, referring to Exhibit
1 i*iii i i
3-22, we can see mat it is technically feasible to reduce the sulfur content of 1V6 inch x 100 mesh
coal to 1.82 percent; however, the resulting yield would be 8.6 percent. From an economic
standpoint, it is unlikely that the benefits obtained by reducing the sulfur content to 1.82 percent
would outweigh the costs associated with the loss of 51 .4 percent of the coal.
linn iiiiiiiiiiiii i inn nil i mi n n inn linn iiiiiini inn inn ninnnnnnnnnnnnnnnninininn i nnnnnnnnnnnnniin innnnnninn mini niiiiiiiiiiniiiiiiinnin iiiiigiiiiiiiiiiiiiiiiiiii iiiiiiiiiiiiininn niiiiiininn in niiiiiiiiiiiiiiiiiiiniiiiiiiiiiininn niniiiiiiiiiiiiininiiiiiiiiiiiiiininnnnni i iiniiniiiiiiinnnnn in i niiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiniiiiiiniiiiiniiiiinninin mini iiiini mi inn i i i i i i
^Laboratory washability data represents separation at ideal (equilibrium) conditions, whereas separations in an actual
not have sufficient time to reach equilibrium and conditions for separation are non-ideal.
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EIA Guidelines for Mining
Overview of Mining and Beneflciation
Exhibit 3-23. Washability Partition Curve
0
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^^^~u i ; ; i
Overview of Mining and Benefication
EIA Guidelines for Mining
r illlliillllllll ii
Ililllllliiill
111 illlliillllllll HI
divided between clean coal and refuse. ep> the probable error, gives an indication of the deviation
from ideal separation and is calculated as the slope of the curve around; dp. ep is also a function of the
panicle size and the density of separation. Each equipment hi a coal preparation plant operates at a
liiLlllllll Illllll fllllM^ III IK illlliillllllll 111(11 II III lllllllIllllllllllllliiil ill ll i ll I ll lllllll ill illlliillllllll ill lllllll lllllllllllllliiiB i i i
•^"^^1^ particular*^ and
i
II I V 111 I I lllllll lllllll II
Although washability data provide an indication of how coal will respond when cleaned using gravity-
based equipment, they do not indicate how .coal will respond to surface-based separation equipment,
such as froth floatation. '• ' ' ' "
Coarse ore tailings or coal refuse can be used to construct an impounding dam, typically within a
• rira?T13geway or narrow valley. Then, a slurry of finer tailings or refuse can be pumped" into the
impoundment area for settling (similar to tailings impoundments described for metal mining above).
As with other tailings impoundments, these can be quite large, with impoundments reaching over 100
feet high and 1,000 feet long. Both NPDES and dean Water Act §404 regulations can, in some
Situations, prevent'the construction of such impoundments. When they are allowed, the major
'": !": ;":":"i: " environmental concern is the destruction of the drainage that is being filled. 'States generally 'require
that existing instream uses of surface waters be protected and maintained (generally known as "non-
degradation" policies), and these often prevent such:
COAL CLEANING TECHNOLOGY
EPA has an ongoing research and applications program that may significantly affect the future form
lid economics of current and developing coal cleaning technologies (Section 1.3.3.). Reports of this
program describe in detail the coal cleaning technologies currently used by the mining industry
(Nunenkamp, 1976; McCandless and Shaver, 1978}.' The engineering principles of mechanical coal
cleaning also are described more thoroughly in orner sources (Leonard and Mitchell, 1968; Cummins
and Given, 1973; Merritt, 1978). The following discussion of coal cleaning technology summarizes
the elements of mechanical coal preparation in the detail necessary to identify the impacts and
pollution control strategies associated with proposed projects.
,
The mechanical cleaning of coal generally includes the five basic stages (Exhibit 3-24) described .
below. The number of stages employed and die unit operations that comprise each stage may vary
among individual operations; atthough Stages 1, 2, and 3 are common to most of the Nation's coal
c|eamng facilities (Exhibit 25).
ii iiiiiiiini 11 iiii ill nil mill i r ii i
1:1(11!
Stage 1—Plant Feed Preparation. Material larger than 21 cm (6 hi) is screened from the
ROM coal on a grizzly. The properly sized feed coal is ground to an initial size by one or
more crushers and fed to the preparation plant.
Sfg* 2—Raw Coal Sizing. Primary sizing on a screen or a scalping deck separates the
coal into coarse- and intermediate-sized fractions (Exhibit 3-26). The coarse fraction is
i i ii iiiiii iiiiiiiiiiiii ii
(•Ilillll ((Illllllllllllliiil
3-132
mil 1 Ill lillH liliililll I11 (111 111 1111 ll I (i !i J
September 1994
•iiiii ii i iiii Fiiii iiiii iiiiii iiiii • i i i 1 iii i i | ill
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ETA Guidelines for Mining
Overview of Mining and Beneficiation
Exhibit 3-24. Coal Preparation Plant Processes
PLANT FEED
PREPARATION
Rtm OF MINE STORAGE
3
z
RAW COAL
SIZING
RAW COAL
SBfeRATION
PRODUCT WATB"
DEWATERING
PRODUa I
STORAGE
AND SHIPPING
3-133
September 1994
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I ll
Overview of Mining and Beneficiation
1 mmi
EIA Guidelines for Mining
1
feK
lllllllllllllllllll 111 (II 111 lllllll
111 IIIIIIH lllllll lllllll
II1II1H
IIIIIIH
I
e£
|
a
i
wa
Illillllllll Ilillillllllll |i|||ill III 11 illllllllllllH in llllillilill llllilH^^ i l|||||||||||||||||||l||||
i
3-134
September 1994
" II
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EIA Guidelines for Mining
Overview of Mining and Beneficiation
Exhibit 3-26. Typical Circuit for Coal Sizing Stage
:^mwAW$s$»/R.R. CAR
3-135
September 1994
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iiiiliiiiiiiiii
Overview of Mining and Benefitiation
EIA Guidelines, for Mining
crushed again if necessary and subsequently is re-sized for cycling to the raw coal
separation step. ""Tie" intermediate fraction undergoes secondary sizing on wet or dry
; yjlfra^ng screens to remove fines, which may undergo further processing. The intermediate
fraction then is fed gpjthg^v/gsa! separator. Coal sizes generally are expressed in inches
11 or mesh' size (Exhibit 3-27). In Exhibit 3-26, the notation 4 x 0 indicates .that all, of the
coal is smaller than 10 cm (4 in). A notation such as 4 x 2 indicates that the coal is sized
[ ; Igfweea ^andJO^m (2 and 4 in). The notation 4+ indicates that the coal, |s larger than
10 cm (4 in). . ": •"'
"
in hi mm
IIH^^^^
iiiiiiiniiiiiiniliiinn i ii iiiiiiiiil iiiiiii in 11
i
,' '• , •
IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIILillll1 IIIIIIIIIIIIIIIIIIIIIIIHIIIIIirlllllllL
., .
^^^^^~™
=ss::fsf™
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• • •
;
Ill: Illllllllllllllll i,II lllllJlliiri:,:"!!
= =.
Exhibit 3-27. Metric and English Equivalents of U.S. Standard Sieve Sizes and
Tyler Mesh Sizes
BiS. Standard Sieve
••'-•':. No.
4
6
8
10
12
14
16
18
20
30
35
40
45
50
60
70
80
100
120
140
170
200
230
270
325
" v*< MediSize •'">••./: • .
) CHI
.475
.335
.236
.200
.170
.140
.118
.100
.085
.060
.050
.0425
.0355
.030
.025
.0212
.0180
.015
.0125
.0106
.009
.0075
.0063
.0053
.0045
indies >
.187
.132
.0937
.0787
.0661
.0555
.0469
. .0394
.0331
.0234
.0197
.0165
.0139
,0117
.0098
.0083
.0070
.0059
.0049
.0041
.0035
.0029
.0025
.0021
.0017
'
' .•:•: ;. V..^.:'; ' *, • ..: , . \}%;_ V'.' .'."•
Tyler Mesh No;
4
6
8
9
10
.12
14
16
20
28
32
35
42
48
60
65
80
100
115
150
170
200
250
270
325
111 111 II II
II fill IIIIIII
Ill 111 IIIIIII
ll 1111111II
iiiiiii nil iliinni 111 ii i 11 ii 11 ii ill nnii iiiiiii nil iiiiniiii in n in
, , ,, ,, _,„ _ • . . . • , , _ ( ( ! I '
™ Coal Separation. Approximately 97.5 percent of the U.S. coal subjected to
~= =l"""~* "" " : processes, including dense media separation, hydraulic
and_frojh flotation. Pnejnnatic separation is applied to the remaining 2.5 percent
™™-' 19785). The coarse-, intermediate-, and fine-sized fractions, are processed separately
^^i^f^'J-^sli^ equipment uniquely suited for each size fraction.. Refuse (generally shale and
middlings (carbonaceous material denser than the desired product), -and cleaned
°
••^^ ii i-niu _
•B^^^^^^ 11^^^^^^^^^^^ 9M^
•IIJH^^^^^^^^ \!«IKP]II|H lliilliin^^^^^^^^
!!!!!!• "'''Fill1*1 ili'f
lB^^^^^^^^^^^
I,11 f ISiOM^^ IIVIIPfllllKnlK',1'!
"iiK B iiii ii;:n^^^^^ ilia
jiiSM^^^^ illllllta^^
^ ii.!:!;')*,!!!','!' silt! iiii;!r-ii:i\
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EIA Guidelines for Mining
Overview of Mining and Beneficiation
• Stage 4—Product Dewatering and/or Drying. Coarse- and intermediate-sized coal •
generally are dewatered on screens. Fine coal may be dewatered in centrifuges and
thickening ponds and dried in thermal dryers.
• Stage 5—Product Storage and Shipping. Size tractions may be stored separately in silos,
bins, or open air stockpiles. The method of storage generally depends on the method of
loading for transport and the type of carrier chosen.
For a typical coal cleaning plant with 910 MT (1,000 T) per hour capacity, approximately 70 percent
of the crushed coal reports to the coarse cleaning circuit. Sizing and recrushing of the coarse coal
result in the cycling of 34 percent of die coarse coal charge to the fine and intermediate cleaning
circuits. Approximately 27 percent of the coarse charge is removed as refuse. The remaining 39
percent is removed as clean product. Process quantities for the fine and intermediate cleaning circuits
appear in Exhibit 3-28. •
<
Exhibit 3-28. Typical Process Quantities for a 910 MT (1,000 T) per Hour
v Coal Cleaning Facility
;;; 't <>-^ ,-' ,-
,',"•' * ^ •. y
,,* - - ' - / r% % -
Coarse coal fraction
Intermediate coal fraction
Fine coal fraction
Thermal dryer dust
Total
.;' Washing
Circuit
MT/hr
630
190
90
910
%
69
21
10
100
•• Dewatering ••-
Circuit
MT/hr
245
330
58
633
%
. 39
52
. 9
100
'Process-. i.':,:.-.:"
Water^*':-:-':v
MT/hr
, 3,293
7,040
16,427
26,760
f v %: .
12
26
61
100
•.s..,,: 'Refuse^ .£ ./
'.'•v Recovery -::>s.'-..
MT/hr
173
82
19
•3
277
^•••:%. "•••••
63
30
6
1
100
Source: Nunenkamp, David C. 1976. Coal Preparation Environmental Engineering Manual EPA,
Office of Research and Development, EPA-600/2-76-138, Washington, D.C., 727 p.
3.5.2.1 Stage Descriptions
The initial screening and crushing of ROM coal at Stage 1 (Exhibit 3-24) may be accomplished in one
or more substages (Exhibit 3-29). The grizzly can be a set of iron bars, welded on 21 cm (6 in)
centers to a rectangular frame. Oversized material that would otherwise inhibit the operation of the
primary crusher is scalped from the feed coal on the grizzly bars. In a multicrusher system, the
output from the primary crusher is screened. Over-sized coal is fed next to a series of crushers, and
finer material reports directly to sizing and separation stages.
3-137
September 1994
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I Overview of Mining and Beneficiation
EIA Guidelines for Mining
1 illiwin in iiiiiiin niniiiniiiniiliiini niiiinin IIIIIINIIIIIIIIIIIIIIIIIIIIIIIIIIJ* n iniiiiiiiiiiiiiiiiiiiiiii in i iiiniiinin i n iliillini inline i ill lllliiiiiiiiiH i iiiilin in• innin mi HIM 1111 niiiiiiiiiiiiniiniiiiinnniii
iiiiiiiliiiiiMiiiiiiiiiiiiiiiiMiiiiiiii in nil 11 n inn in i nniinniniiniinnini i ininiiiniiiiiniiiiiininni ni» n i i nn n 11 in ii in n • |i in in i nl HI j
Exhibit 3-29. Typical Three-Stage Crusher System for Raw Coal Crushing
£,,,S2S ...... 22 ..... X ...... £2JS!S,IS,2l?ge l CfasW^ include rotary breakers, single and double
roll Crushers, hammermffls, and ring crushers. Each type of mill is available in various models which
crush the ROM coal at different rates to different sizes. The general characteristics of crushing mills
appear below (McQung, 1968).
'!" ! ....... «•««« ,'!,"
' ....... Mil ftl i
. breaker. Often called the Bradford breaker after its inventor, this large, rotating
cylinder is driven at12 to18 revolutions per minute by an electric motor via a chain and
reducer drive. RO|| cgal |§ilssiucMithrough one end of the cylinder and is crushed
against tne encirc|ing steel plates. The crushed coal exits the breaker through the precut
holes nj the plates and feeds to a conveyor. Slate, overburden, rock, and other gangue
materials that resist breakage are carried by a series of baffles to the far end of the cylinder
Where they are removed from the mill by a continuously rotating plow.
•i ii iii 11
1 Single-and Double-Ron Crushers. A roll crusher comprises one or two steel rollers
I gB^* i^11 two SUSS! Ispgths of heavy teeth. The long teeth slice the large pieces of
I W mtp fragments and feed the flow of coal into the smaller teeth, which make the proper
^reduction. In single-roll mills, the coal is crushed against a stationary breaker place
(Exhibit 3-30a). Double-roll crushers also fragment the coal with specially designed teeth
Crushing action against the rollers (between the teeth) is minimal (Exhibit 3-30b). Both
I nulls are fed through the top. Product exits through the bottom.
11 Mil III IIII III II II II I III 111 III I
in nil in in i ii ii ii nil 11 iiiiiii
in i n n n n in nn i nn in i i n n 11 n in i in Mini
III ill III III I i III 111 III I III III II ill III
3-138
September 1994
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EIA Guidelines for Mining
Overview of Mining and Benefitiation
Exhibit 3-30. Single-Roll (a) and Double-Roll (b) Crushers for Sizing of Raw Coal
Source: McClung, J.D., 1968. Breaking and crushing. In Joseph W. Leonard and David R.
Mitchell (eds.), 1968.
3-139
September 1994
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Overview of Mining and Beneficiation
EIA Guidelines for Mining
i i ,,i grate and discharged to a bin or conveyor.
Ring crusher. The principles of hammermill and ring crusher operations are similar.
Instead of hammers, the ring crushers uses a set of smooth and toothed rings to drive the
feed coal against the breaker plate.
The unit operations that commonly are employed at Stage 3 of Exhibit 3-24 (separation) vary
considerably among, modern cleaning installations nationwide. The choice of unit operations for a
particular installation depends on a number of factors, including coal preparation objectives,
' availability and costs of equipment, and operator *ixperience. Nile of the typii
currently are employed during the separation step are listed below (McCandless and Shaver, 1978).
With the exception of froth flotation, all of these operations utilize the specific gravity principle to
affect a coal/impurities separation! Water requirements, sizes and rates of feed, and dewatering
of selected unit processes are described in Exhibit 3-31.
'- ifi'nBI'IfiiHii
Dense Media. Light, float coal is continuously skimmed from a suspension of solids in
that separates from heavy liquid with a defined specific gravity (usually magnetite;
Exhibit 3-32). Finely-ground magnetite is usually used in the suspension, in part because it
can be easily recovered from the clean coal and refuse by magnets. - Accuracy of separation
is sharp from 0.059 to 20 cm. Quality and sizes of feed can fluctuate widely.
Froth Flotation. A slurry of coal and collector agents is blended to induce water-attracting
tendencies in selected fractions of the feed coal. After the addition of a frothing agent,
finely disseminated air bubbles are passed through the slurry. Selected coal particles adhere
to the air bubbles and float to the surface, to be skimmed off the top. The process can
separate fractions in a band of 0.045 b 1.18 mm (0.002 to 0.05 in). Froth flotation affects
a good separation between coal and ash, but does not successfully separate coal from pyrite,
because the latter mineral is, like coal, hydrophobic. Better sulfur reduction results can be
obtained using two-stage flotation. The first stage proceeds as described above. In the
==^ second stage, the float product is re-slurried and then treated with an organic colloid that
; sl "''• :' ' ' ' selectively prevents the coaTplxticites from flo^gg to the top with the pyrite.
::;!~ :.: •Humphrey Spiral. A; shiny of coal and water is fed into the top of a spiral conduit. ^ The
*™*** ™' :
flowing1 particles are' stratified by differences ...... in density, ....... with ..... the ..... denser ...... fractions ....... flowing .....
IS ...... fe ...... wal| ....... SlJhe ...... condjii|s ............... A ...... spIntiGratlSe ...... imm separates the stratified
5*sluny into final product and middlings.
; [[[ I ............................................... facilities. ' ' • "
....... These ..... products ...... are' ..... fed ...... to separate dewatering
•»• *E!!tS &*hTOcycJoiies. A slurry of coal and water is subjected to centrifugal forces in an
ascending vortex. The denser refuse material forms a layer at the bottom of the vessel.
H&8HHi:!!li'riE!!SpfiS Circulating'water skims the clean coal from the top of the stratified shiny and directs the"
^^^•;i^ ''^^,1 product to a vortex finder, which feeds the cyclone overflow into the product dewatering
•»^^^^^^^^^^^^^^^ i»^^^ "stage (Nunenkamp, 1976). Feed coal sizes range between 0.044 and 64 mm (0.002 and
ill "•"iiii iii'ii'ijiiiii_ . *
25 in).
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EIA Guidelines for Mining
Overview of Mining and Beneficiation
]
.
,
Exhibit 3-31. Feed Characteristics of Unit Cleaning Operations
for Sizing and Separation of Crushed Coal
s > f "~
*• -,
Coal Cleaning Unit
isaumjig
Belknap washer
Chance cone
Concentrating table
DSM heavy media cyclone
.Flotation cell
Humphrey spiral
Hydroseparator
Hydrotator
Menziescone
Rheolaveur free discharge
Rheolaveur sealed
discharge
Water Required
per MT of Feed
ttpn)
12 to 21
21
29 to 50
50 to 67
83 to 125
(heavy media
slurry)
54 to 67
125
58 to 75
50 to 67
58 to 75
12 to 17
25 to 50
Maximum ••:••• ':• ••.':
• Feed -Rate--? --.^
(MTph)
9.8 to 48 per m2
of jig area
124
488 per m2 of
cone area
9.1 to 14
4.5 to 32
1.8 to 3.6
0.9 to 1.4
1.4 per vertical
cm of vessel
49 per m2 of "
surface
273
1.1 to 1.8 per cm
of vessel
2.9 to 3.6 per cm
' of vessel
Range of
Feed Sizes
(cm)1
0.3 to 20
0.6 to 15
0.2 to 20
0 to 0.6
0 to 0.6
0.030 to 0.0075
0.6 to 0.0075
1'.3 to 13
0 to 5.1
1.3 to 13
0 to 0.6
0.6 to 10
Percent Solids
in Feed
85to90
85 to 90
85 to 90
20 to 35
12 to 16
20 to 30
15 to 20
85 to 90
85 to 90
85 to 90
15 to 30
15 to 30
'Range of feed sizes is listed for bituminous coal only. Anthracite feeds for Menzies cones and
hydroseparators range between 0.08 and 13 cm. The DSM cyclone accepts anthracite feeds between 48
mesh and 0.75 in. The flotation cell accepts 200 to 28 mesh. The Belknap washer does not process
anthracite.
Source: Apian, F. F.. and R. Hogg, 1979. Characterization of Solid Constituents in Blackwater
Effluents From Coal Preparation Plants. Prepared for the EPA and U.S. DOE, EPA-600/7-79-006, FE-
9002-1, Washington, D.C., 203 p.
3-141
September 1994
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llllllllllllllllll
l II" 111 111 1111 ill illiilli i ^^ 111 lip lililillii III III npll lllllll \^f ill III I"' ! i ' ' ' ii |l1111 1 in i ' "' I i i" ' i ' i i* |
I1 , . . • < '
verrieff; of Mining and BenefidatJon EIA Guidelines for Mining
] ' _ ' i
Exhibit 3-32. Typical Circuit for Dense Media Coal Cleaning
PLAiiT ALTERNATE!
COARSE MAC. SEPAR. CLEAN COAL
FINE MAG. SEPAR. A •
CENTRIFUGE LOADING OR
CENTRIFUGE «*•« «*
CENTRIFUGE
CRUSHER
CYCLONE
LIGHT MEDIA SUMP
HEAVY MEDIA SUMP
HEAVY MEDIA SUMP
SCREEN
SCREEN
REF. RINSE SCREEN
TO REFUSE UN
COAL RINSE SCREEN
SLURRY SCREEN
REFUSE RINSE SCREEN
MVY. MEDIA RATH
HVY. MEDIA CYCLONE
EMISSION POINTS
(1) TO WTER CLARIFICATION
Ill
III IIIIIIIIIIM Ill lllllii ! III H lllllllII) ill illIill llilllllll
3-142
iiiiiir iii i
September 1994
• 11111 in 111111 iiiii in iiiiiiiiiiiiiiiiiiiiiiii i in
IIII i III I" Hi III Illllllllll ill III 11 111 ill lllllll il IP 111 111 III 11 IIII III III llilllllll ii 111 IIIIIIIIIIIIIIIH i illill III 11 ill IllIill lllllll
II llilllllll lllllll II II lllllll lllllll I III IIIIIIH^^ I llilllllll lllllll 11 Illllllllllllllll II llilllllll 111 III IIII llllllllllllllllll 111 111 Illllllllll II llllllllllllllllll llilllllll 111 llllllllllllllll||l|
i I Ii IL
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EIA Guidelines for Mining _ Overview of Mining and Beneficiation
• Jiggings. A shiny of eoal and water is stratified by pulsating fluid. Clean, low density
coal is skimmed from the top of.the vessel. The accuracy of separation is low. Sizes of
feed coal range between 3.4 and 76 mm (0.1 and 3 in; Exhibit 3-33).
*.
• Launders. Raw coal is fed with a steam of water into the high end of a trough. The coal-
water stream stratifies as it flows down the incline. The denser refuse material forms the
bed load of. the trough while the less dense coal is suspended in the stream. The cleaned
product is split from the stream at the low end of the trough. Feed coal sizes range
between 4.76 and 76 mm (0.19 and 3 in).
• Pneumatic. Streams of pulsating air stratify the feed coal across a table equipped with
alternating decks and wells (Exhibit. 3-34), Refuse is pushed into the wells and withdrawn
under the table. The cleaned product rides over the refuse and is withdrawn at the '
discharge end of the table. Feed coal sizes range to a maximin^ of 9.5 mm (0 38 in-
Exhibit 3-35).
• Wet tables. A slurry of coal and water is floated over a table that pulsates with a
reciprocating motion. Denser refuse materials flow toward the sides of the table, while the
cleaned coal is skimmed from the center. Feed coal sizes range between 0.15 and 6 4 mm
(100 mesh and 0.25 in).
The process waters used during the coal separation stage generally are maintain^ between pH 6.0
and 7.5. Waters with lower pH inhibit the flotation of both coal and ash-forming substances. As pH
increases, the percentage of floating coal maximizes, but the percentage of floating refuse also
increases. The pH of process waters may be elevated with lime. Reagents may be added to control
the percentage of suspended fines (Zimmerman, 1968).
Make-up water for cleaning plant operation ideally has a neutral pH, low conductivity, and low
bicarbonate content. The water preferably is free from contamination by sewage, organic material,
and acid mine drainage. Other dissolved constituents also should occur in low concentrations (Exhibit
3-36). •
Product dewatering (Stage 4 of Exhibit 3-24) includes the use of mechanical devises, thermal dryers,
and agglomeration processes to reduce the moisture contents of processed coal and refuse
(McCandless and Shaver, 1978; Exhibit 3-37). The moisture contents of products dried by typical
processes appear in Exhibit 3-38. Mechanical processes are of two general types:
• In-stream process that do not produce a final product (hydrocyclones.and static thickeners).
These processes remove approximately 30 to 60 percent of the moisture in feed material.
Thickeners and cyclones usually are placed on line with other drying devices that reduce the
moisture contents further.
• End-of-stream processes that produce a final product (screens, centrifuges, spiral classifiers
and filters). «» r •
3-143 September 1994
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Orel-view of Mining and Benefitiation
EIA Guidelines for Mining
IV
Illlllllllllllli
illlillH
Exhibit 3-33. Typical Circuit for Jig Table Coal Cleaning
SCREEN
M
REFUSE BIN { )
(1) TO HATER CLARIFICATION
A POINTS OF EMISSION
CLEAN-COAL LOADING
OR STORAGE
Source: EPA. 1977.
Ill 111 III ' I Ill I in Ill I II Ill 1 1 1 1 nil
3-144 September 1994
IlllllllH I IIIIIIIIIIIII III III 111 I III III l||llllll Illlllllllllllli Illlillill Illlllllllllllli in! Ill II Mi illlliiilililll I Illlllllllllllli 111 hi Illlllllllllllli 111 111 IIIII 111 in I ll'l III IIIIIIIIIIIII I n'HI 111 ill II 11 II Illlllllllllllli ili|l|l|iil|i|||||||llillillill|llill Illllliill llillhli1 II Ill
I I l I I I I |li| | I I I in | I HI I I Ill I
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EIA Guidelines for Mining
Overview of Mining and Beneficiation
Exhibit 3-34. Typical Air Table for Pneumatic Coal Cleaning
*
•FEED BIN
MOTOR
SHAKER UNIT
SPEED REDUCER
I
AIR DUCT
CLEAN COAL
DAMPER
HUTCH
Several of the process that are used for Stage 3 separation also are used for Stage 4 dewatering,
including hydrocyclones, centrifuges, and spiral classifiers. These processes are described above.
Static thickeners, screens, and filters may also have a separation function; but are more appropriately
described as dewatering processes.
• Static thickeners generally are used in conjunction with flocculants to settle the fines from a
static pool of preparation plant refuse water (blackwater). A typical thickener feed contains
1 to 5 percent solids; thickened underflow contains 20 to 35 percent solids. Common
flocculants include inorganic electrolytes such as lime and alum, and organic polymers such
as starches and polyacrylamide (Apian and Hogg, 1977). Sludge from the thickener
underflow may be dewatered further by mechanical devices, thermal drying, or
agglomeration. A typical thickener vessel appears in Exhibit 3-39.
• Screens serve dual functions of dewatering and sizing. The mode of operation (fixed or
vibrating), mesh size, and bed depth of feed material are chosen on the basis of raw feed
characteristics (gradation and moisture content), feed rates, and the desired efficiency of
sizing and dewatering. The sieve bend, a typical dewatering and sizing screen, appears hi
Exhibit 3-40 (Nunenkamp, 1976).
• Filters are of two types—pressure and vacuum. Both types generally accept a feed with 30
percent solids at 27 dry MT (30 T) per hour. Pressure filters produce a cake with 20 to 23
percent moisture. Product cake from vacuum filters may contain 34 to 40 percent moisture.
The moisture removal efficiency of the pressure filter is offset by its higher capital cost
relative to vacuum filter systems. A typical vacuum filter appears in Exhibit 3-41
(Nunenkamp, 1976).
3-145
September 1994
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I ;
t
of Mining and Benefitiation
EIA Guidelines for Mining
l'«l Ill Ill ill
III III 11 in ill 1111 lllill1
iii'iiii ni in
Exhibit 3-35. • Typical Circuit for Pneumatic Coal Cleaning
2 X 3/8 •*•
TO LOADING OR WET CLEANING
VENT TO
ATMOSPHERE
in if i i ill
EMISSION POINTS
STACK EMISSIONS
Source: EPA. 1977.
lllllllNlllIil lllill ill IP i 111111 II ill ill il "Illi ill i IH 1111! ill"!!' 1111 n'lil 1111 lull
3-146
September 1994
IH^^^^ Ill 11 IllB liillllBtmum lUllllil"'illllll lliliiillillllll iiil'll 11II1 ilil Nil lull ill11 1.1 i
•ilil in iiiiiiiiiiiiiiiiiiiiiii iiiiii 11 iiiiiiiiiiiiiiiiiii
liiillllllill IIIIIIIII III I IIIIIIIII I 111 II 111 111 I 111 II II II llllll|lllllll|llllllllllllllllll I Mil Illllll I III IIIIIIIIIIIIIIIIIII
lllill 1 IIIIIIII IIIIII 111 I liiillllllill III 111 111 liiillllllill I III III III III liiillllllill I IIIIIIII 111 lllill II111111111 liiillllllill I I I Illi
iiiiiiiii iiiiiiii I mi ill I 1 liiillllllill I iiiiiiiii iiiiiiH^ in liiillllllill iiiiiiii inn iiiiiiii 11 in 111(11 ill iiiiiiM ii nil lllill
liiillllllill lllllll liiillllllill 111 liiillllllill IIIIIIIII IIIIIIIII IIIIII I|II|II11M liiillllllill II IIIIIIIII^ II 111 Illlllllllllllllllllllllllllllll I lllll|lllll III IIIIII IIIIIIM IIIIIIIII IIIIIIIII 111 I lllllllll|l lllllll(
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Guidelines for Mining
Overview of Mining 'and Beneficiation
Exhibit 3-36. Desirable Chemical Characteristics of Make-Up Water for
Coal Cleaning Processes
,
f s-
. Parameter
pH
Hardness as CaCO3
Ca
•Mg
.Na
K
NH«
C03
HCO3
a
S04
N03
NOj
P04
SiO2
Concentration*
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IIII 111 I III I I I
Overview of Mining and Benefidation
EIA Guidelines for Mining
ii in i
\im™i\ ii iiiiilJi'iiimmiiii''in 8"!'ii "m ii iiB^^^^^^^^^^^^^^^^^^^^^^^ ' iiiiiiiiii 1•! ! I,
Exhibit
?8M X 6
SLURRY
3-37. Typical Product Dewatering Circuit for Coal Cleaning
. <8M X 0 REFUSF
. t- RAW COAL
I/CYCLONE
ts
OFAM
P_FFLOTATION CELLS
fnii
4S X
RETURN TO
WSH1NS CIRCUIT
TO STREAM
DISC FILTER
CLE4H CQgL CLARIPTED WATER
RETURN TO THERMAL RETURN TO
DRYER OR LOADING CIRCUIT
3-148
September 1994
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EIA Guidelines for Mining
Overview of Mining and Beneficiation
I
Source:
First Ai
150,15
Ixhibft 3-38. Typical Moisture Contents of Dried Product from Selected Drying
Operations in Coal Cleaning Facilities
' , ,, ,,,, Typeof '
Equipment or Process
Dewaiering screens
Centrifuges
Filters
Hydraulic cyclones
Static thickeners
Thermal dryers
Oil agglomeration
Moisture Content of
Discharge Product (%)
8 to 20
10 to 20
20 to 50
40 to 60
60 to 70
6 to 7.5
8 to 12
McCandless, Lee C., and Robert B. Shaver. 1978. Assessment of Coal Cleaning Technology:
mual Report. EPA, Office of Research and Development, Washington, D.C., EPA-600/7-78-
3 p. ' •
• Multilouver dryers comprise two concentric, revolving cylindrical shells, each fitted with
. louvers that support the bed of feed coal and direct it toward the discharge point.
Multilouver dryers can handle large volumes of wet material that require a relatively short
drying time to minimise the potential for in-dryer combustion of the feed product.
• Rotary dryers consist of a solid outer cylinder and an inner shell of overlapping louvers that
support and cascade the drying coal toward the discharge end. Drying action can be direct
(using the products of combustion), or indirect (using an intermediate fluid for heat transfer
between the shells).
• Screen dryers apply gas pressure from combustion to squeeze the moisture mechanically
from the feed coal through the supporting screens. A lower percentage of coal fines
(relative to other drying processes) thus may be lifted from the bed. Coal is exposed to
drying heat for approximately SO seconds.
• Suspension or flash dryers continuously introduce feed coal into a column of high
temperature gases (Exhibit 3-43). Surface moisture is dried almost instantaneously (flash
dried). Coal is exposed to the drying gases for approximately 5 seconds.
• Turbo-dryers contain an inert nitrogen atmosphere (less than 3 percent oxygen) that
prevents the explosion or ignition of coal fines in die sealed drying compartment. Wet coal
enters a stack of rotating circular trays that successively feed the coal to lower trays using
stationary wiper blades.
Indirect heat dryers use heat transfer agents (including oil, water, or steam) that do not come into
contact with the feed coal. Drying coal is circulated through the heating chamber on covered
conveyors that may be equipped with helical (worm) screws, fines, paddles, or discs. The drying
fluid circulates around the conveyor and through the hollow screws.
3-149
September 1994
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. Orel-view of Mining and Beneficiation
EIA Guidelines for Mining
i iiiiiiiiiiiiiiiiiiiii iiiiiiiiiiii
Exhibit 3-39. Thickener Vessel for Dewatering of Coal Cleaning Products
: NmrCTVamp, David C., 1976.
operations (Stage 5 of Exhibit 3-24) are discussed more thoroughly in
Eg* ESS"?,**™18 document, The, degree of sophistication in individual storage and loading
*' "*•—*"Ms part me volume of coal being processed, stored, and shipped, as well as the lands
av5*flable-
systems can load a moving train directly from
...... lowers ....... and dump trucks to feed
3.5.2.2 Process Blow Sheet for Typical Operations
Thj complete-coal, cleaning plant utilizes a series of unit processes to prepare ROM coal for storage
": 2^2 P,!0^!5*! BSst be mutually compatible for proper operation of the plant. Rates
.^"M:5°!3Pj™5!?fto?capabilities of other in-line processes.
, especially in operations that use heavy media such as magnetite
°°
water
3-150 September 1994
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EIA Guidelines for Mining
Overview of Mining and Beneficiation
Exhibit 3-40. Schematic Profile of a Sieve Bend Used for Coal Sizing and Dewatering
FEED
SCREEN SURFACE
OEWJTCTED
mooucr
3-151
September 1994
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Ill III 111
Overview of Mining and Benefication
EIA Guidelines for Mining
miillliiiiiiliii i I in
III •
IlllllH
Exhibit 3-41. Proffle View of a Coal Vacuum Filter
DRYING ZONE
otsounci
SUIftMY FEED
OtSCHAMC
SECTION
OVERFLOW
Source: Nunenkamp, David C.. 1976.
in n n in inn i i i nil i hi
ill mm'ii
III •ill i i1
iiii1 uiiiiiiiiiiiNiiii IIP
l" HI IIIHli1
'iii (iinii II i in111 in iiiiiii|i)iiiiiiiiiii ill i in in Hi mi i iiiiiiiiiiiiiiiiiii ii i iiiiiiiiiiiiiii
iiPi 11 in i iimi'i luiiiii hi iiiiw '
111 111 „ II
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EIA Guidelines for Mining
Overview of Mining and Beneficiation
3-153
September 1994
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Overview of
i ..... i ......... Ill ........ II ..... lull .......... | ..................... I .................... I ...................... li nl ................ I .................... I ..... Ill ......... 1 ............. In ij ................... I .......... I ...... Ijillill ...... Ill ........ . ................................... |liiliiliii| ................ I ........ I .............. Iliilll [[[ I ............. I ........... lijj|| ............. 11 ..... II ...... . ...............
and Benefication _ EIA Guidelines for Mining
Exhibit 3-43. Typical Flash Dryer
(1 III III • i I ill
ALTERNATE
WET SCRUBBER.
(IF REQUIRED)
' C-E RAYMOND FLASH DRYING
SYSTEM FOR COAL
ilillll
ALTERNATE ARRANGEMENT
FOR VERY FINE WET COAL
•li ni in
i
VENT ^RELIEF VENT
**
4IRY COAL
CONVEYOR LJ,
DRY COAL DISCHARGE
FROM AIR LOCK^.
AUTOMATIC
DRY DIVIDER
DRY RETURN
WET FEED
MIXER
-•-DRYING COLUMN
DRY COAL CONVEYOR
MET FEED CONVEYOR
WET FEED BIN
GATE
T FEEDER
DOUBLE FLAP VALVE
TEMPERING AIR DAMPER
^^
! 3-154
•
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EIA Guidelines for Mining ' Overview of Mining and Benefication
slurries for the separation of product from refuse. Evaporation and consumptive water use may
require the introduction of make-up water to the process cycle. .
A complete process flow sheet can be broken into three parts:
• Coarse stage (Exhibit 3-44)
• Fine stage (Exhibit.3-45)
• Sludgfr stage (Exhibit 3-46).
The coarse stage feed fine coal and refuse to the fine stage. Coal slime, which includes fine coal and
refuse, is fed to the sludge stage. Each stage .produces characteristic blackwater and refuse. Process
waters from the fine coal and sludge processing stages generally contain higher proportions of fines,
especially clay-size particles, than coarse stage process waters. A series of thickeners, cyclones,
screens, filters, and dryers may be used to recover a iriaTimom percentage of solids from the recycled
process waters.
3.155 September 1994
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Overview of Mining and Benefiriation
EIA Guidelines for Mining
infill H^ Ilillll I i ll|i|li||i|l
Ilillll Ilillll Ilillll
llWliillH III
IllllllllH IIIIIIIIM
Exhibit 3-44. Coal Cleaning Plant flow Sheet for Coarse Stage Separation and
Dewatering
Row CotHi
^ Trash
tr—--—..X^..—-
• FINE COAL .
I- ;_. , j PREPARATIONS
Orjm-Rm«* | j(S** Fif«r* 35 }i
Source; EPA. 1976.
s »••.•••—•••^.•^
] f COAL"fiLli«l
ti«
LEGEND
mti^z
'• Rout* of Coors* Cool
of Refus*
Rout* of Heavy Media Slurry
•Optional Route-Snk-F!oat*Msaia
-Route of Sink-Float-f M*4ia
•Route of Mogiwtit*
Route of Dirty Process Water
Route of Clean Process Water
Route of Fresh Mofafup Water
5-156
I
September 1994
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EIA Guidelines for Mining
Overview of Mining and Beneflciation
Exhibit 3-45. Coil Cleaning Rant Flow Sheet for Fine Stage Separation and Dewatering\
. _
(SooFigur* 34) «•«•••«
, fc , _ . . •. » «»
Mokt-ap
Wfltof
Storooo
I Medium T
to R«f UM
Disposal
To-Dttliming Screen
(S«« Fiur* 34 )
ie Stporoter
i^m^mft^m
LEGEND
N
MIM» Opfionof Routt of Fino Cool
—fr-Rauta of Sink*FIoot
-------
^^^ 111 111 11111 111 I 111 Illlllllin Illlllllf II
111 111 111 11(111111 111 111
in iiiii iiiiiiiiiiiiik i in in i i
111 III III 111 1111 111 1111I111 llilllllllilll
. iiiiiiiiii iiiiiiiiiii in 11 in
iiiiiiiiiiii iiiiii iiiiiiiiiiiiliill
1H^
MI 11 iiiiiiii i iiii in in i in iiiii in iiiiiiiiii
of Mining and Benefication
EIA Guidelines for Mining
iii 11111111 iiiiii nil MI iiiiii iiiii iiii 11 ill n in livlliiilililnnlnininiy iiii n i nun n i in in ill in
Exhibit 3-46. Coal Cleaning Plant Flow Sheet for Sludge (Slime) Separation and
Dewatering *~
Ced Sliffx Frmn Dtstifnitu
Hydfo-Cydenji
*....,..
fttflltt
»i*pe«ol
LEGEND
i Ill
-Route of Cool
-ROU!« of Coktd Rtfust
«*-Rout» of R.fon
Source: EPA. 1976
111 III !• IIIIII IN|III111H IIIIII iV IIIII (Ill
n nil
3-158
September 1994
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EIA Guidelines for Mining Environmental Issues
4. ENVIRONMENTAL ISSUES
This section describes the environmental impacts associated with new source mining operations. The
mining industry and its potential environmental impacts are unusual in a number of ways, of which
three may be the most important. First, many of the potential impacts are unique to the industry
(acid rock drainage, releases from cyanide leaching units, structural failure, etc.). Second, many of
the impacts may be those manifested years or decades after mining ends and can intensify over time.
Finally, the nature and extent of impacts from mining operations, perhaps more than any other
industrial category, are based on factors that are specific to the location (including geology,
hydrogeology, climate, human and wildlife populations, etc.). Impacts from similar types of
operations can range from minimal to extensive depending on local conditions. These factors
emphasize the need for full understanding of baseline conditions and careful planning to avoid/
mitigate potential impacts.
As in all major industrial operations, careful design and planning play a critical role in reducing or
mitigating potential impacts. In the case of the mining industry, the three characteristics that
distinguish it from other industries (unique impacts, often delayed, that depend on site-specific
factors) make initial design and planning even more crucial. This in turn makes any assessment of
potential impacts, both immediate and long-term, reliant on detailed information on site-specific
conditions, and on the design and operation of the facility. Site-specific information is generally
incomplete at the time of permitting. Design and operation plans, including operations to mitigate
potential environmental impacts, are often only conceptual at the time of permitting. This makes it
extremely difficult to delineate the types of information and analyses that are necessary to assess
potential impacts.
The following subsections are organized according to the major environmental issues that are raised
by mining operations. These include:
• Acid rock drainage
• Cyanide
• Structural stability of tailings impoundments
• Natural resources and land uses
• Sedimentation/erosion
• Metals and dissolved pollutants
• Air quality
• Subsidence
• -Methane releases from coal mining and preparation.
4-1 September 1994
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, I I I
lllllll I Illlllllllll III Illllllllllllllllllllllllll 11II 111 III II l|llin IlililH^ IIIIIIIH^ Illlllllllllllllllllll I Illllllllllllllllll HI IIIIIIH lllllll I I 111 III11 11 111 III I Illlllllllllllllll II 11111 111 Illlllllllll II Illlllllll I 111 1|1 111 Hill III IIIIIIIIH III llllllllllllllllllll|llllllllllllll III1IIIIII11I1I1 I 111 Illlllllllllllllllll II III llll|llllll|lll|l llllllllllH llllllllllllllll lllllllllll|lll|(
_
Illlllllllllllllll Illlllllllll I Illlllllllllllllll Mill 111 l|lliilllilliiiiB Illlllllll Illlllllll ill 111 HIM I Mill I • l|| II 11 I
4 Environmental Issues EIA Guidelines for Mining
The discussion of each, of these subjects includes a description of the topic and of the types of
information that are necessary to determine potential impacts.
4.1 ACID ROCK DRAINAGE
The formation of acid drainage and the contaminants associated with it has been described as the
Srgest environmental problem fiicing'the U.S. mining industry (U.S. Forest Service^ 1993; Ferguson
-Lakto,199
mine drainage (AMD), acid drainage from mine waste rock, tailings, and mine structures such as pits
and underground workings is primarily a function of the mineralogy of the rock material and the
of ^gj. and oxygen. While acid may be neutralized by the receiving water, dissolved
metals can remain in solution. Dissolved metals in acid drainage may include the full suite of heavy
===j! ' = i | i , ' i " "I , '," J I, 1,1 *
ilSHSS* including lead, copper, silver, manganese, cadrnintnt fron, and zinc. Elevated concentrations
in surface water and groundwater can preclude then- use as drinking water supplies.
Further, low pH levels and high metals concentrations can have acute and chronic effects' on aquatic
AcM drainage from coal and mineral mining operations is a difficult-and costly problem. In the
United IMS8, more than 7,000 kilometers of streams are affected by acid drainage from
et al.,1982). Similar impacts are observed in coal mining areas of the Midwest. As one
ii^=Min|ny. examples of historic coal mining areas, 2,400 acres of abandoned surface mine land
northwest of Montrose, Missouri, are impacted by acid mine drainage. More than half of the 100
less than 4 and there are 1,200 acres of "barren, acidic spoil." Overland
mine spoil has pH values between 2.9 and 3.5 (Blevins, 1990). In the western United
Jhe= |?pjej| Series jstmratesjbjt between 20,000 and 50,000 mines are currently generating
Se^ce jandSi and that drainage from these mines is impacting between 8,000 and
(U.S. Forest Service, 1993).
I i
generation prediction tests are increasingly relied upon to assess the long-term potential of a
iii!g!!iiiii!!!!«!!!!!!!!!!!!!!S i Y inn in i *•* r
g,| lg|te g generate acid. Becausennmeralggy_ and other factors affecting the potential for
formation are highly variable from site to site, predicting the potential for ARD is currently
difficult, costly, and of questionable reliability. Further, concern has developed because of the lag
.tifn^at existing mines between waste emplacement and observation of an acid drainage problem
(Uniyersity of Caltfornia, Berkeley, 1988). With acid generation, there is no general method to
predict its long-term duration (in some cases necessitating perpetual care). The issue of long-term or
perpetual care of acid drainage at historic mines and some active mines has focused attention on the
need for improving prediction methods and for early assessment of the potential during the
U.S. Forest Service sees the absence
•MH||mKnMV2iiI SS2S jf, ££ 22S S&fliSHSfS ventures, as a major problem facing the future of
SS meal mining in the western United States (U.S. Forest Service, 1993).
I
ii inn
4-2 September 1994
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EiA. Guidelines for Mining _ Environmental Issues
The problems presented by acid drainage are encountered worldwide, and there is a growing body of
literature that documents examinations of all aspects of the phenomenon, from the genesis of acid
drainage to prediction of the timing of its occurrence to prevention. The most recent advances in the
field are compiled in the proceedings of the International Land Reclamation and Mine Drainage
Conference and Third International Conference on the Abatement of Mine Drainage, which was held
in April 1994 (U.S. Bureau of Mines 1994).
/
The remainder of this section addresses the major topics related to understanding how acid rock
drainage is generated, how to predict it during mine planning, how to detect it during operations, and
approaches to mitigating its impacts. " . • ,
4.1.1 NATURE OF Aero ROCK DRAINAGE .
4.1.1.1 Add Rock Drainage/Oxidation of Metal Sulfides
Acid is generated at mine sites when metal sulfide minerals are oxidized. Metal sulfide minerals are
common constituents in the host rock associated with metal mining activity. Prior to mining,
oxidation of these minerals and the formation of sulfuric acid is a function of natural weathering
processes. The oxidation of undisturbed ore bodies followed by release of acid and mobilization of
metals is slow. Natural discharge from such deposits poses little threat to receiving aquatic
ecosystems except hi rare instances. Mining and benefieiation operations greatly increase the rate of
these same chemical reactions by removing large volumes of sulfide rock material and exposing
increased surface area to air and water. Materials/wastes that have the potential to generate acid as a
result of metal mining activity include mined material such as spent ore from heap and dump leach
operations, tailings, and waste rock units, including overburden material. Equally or more important
at some mines are the pit walls in the case of surface mining operations, and the underground
workings associated with underground mines. .
The oxidation of sulfide minerals consists of several reactions. Each sulfide mineral has a different
oxidation rate. For example, marcasite and framboidal pyrite will oxidize quickly while crystalline
pyrite will oxidize slowly. For discussion purposes, the oxidation of pyrite (FeSj) will be examined
(Manahan, 1991):
2H2O + TOj -> 4H+ + 4SO?
In this step, Sf~ is oxidized to form hydrogen ions and sulfate, the dissociation products of sulfuric
acid hi solution. Soluble Fe2* is also free to react further. Oxidation of the ferrous ion to ferric ion
occurs more slowly at lower pH values:
4F62-1- + O2 + 4H* -> 4FC3* + 2H2O
4-3 September 1994
-------
: v g^°n*ental Issues ; '. : ; EIA Guidelines for Miniiig
mSmm ...... nw ...... mt ..... •iSi,,,,2«?xidation fa caXalyzed by a variety of Metallogenium, a •
naturally occurring filamentous bacterium. Below a pH of 3.5 the same reaction is catalyzed by the
naturally occurring iron bacterium ThiobadUasferrooxidans. If the ferric ion is formed in contact
with pyrite the foljgwing reaction can occur, dissolving the pyrite:
"' '
4- 14Fe?* + 8H2O -> ISFe2* + :2SOf + 16H
, f ..... . • ,li ; . . ,•,,'. . ' '
This reaction generates more acid. The dissolution of pyrite by ferric iron (Fe3*), in conjunction with
the oxidation of the ferrous ion constitutes a cycle of dissolution of pyrite. Ferric iron precipitates as
hydrated iron oxide as indicated in the following reaction:
3H
Ill 1111 111 IIIIIIII 111 IlllllH llllllH IIIIIIII lllllllllllIB lllllin^
Fc(OH)3 precipitates and is identifiable as the deposit of amorphous, yellow, orange, or red deposit
on stream bottoms ("yellow boy").
1 i • . ' . , •',„,'„„' '._,,' _' "„„',," j1 ,r '",„,'
4.1.1.2 Source of Acid and Contributing Factors
The potential for a mine or its associated waste to g_ enerate _acjd and .release ...... contaminants, ,|s, dependent
OI fectors and is site-specific. Ferguso^and ...... Ericfaon ..... (1988) ....... identified primary, secondary,
tors ftat control acid jdiainage:" These factors provide a convenient structure for
discussion of acid formation in the mining envhx)nment. Primary factors involve
production of the acid, such as the oxidation; jgacjions. Secondary factors act to control the products
of the oxidation reaction, such as reactions with ..... ofhvjnfaaab ....... thM^consumelacid,,: Secondary factors •
acid or react wiui other minerals, thereby releasing contaminants. Tertiary
...... *£%* to ** Physical aspects of the structure or waste management unit (e.g., pit walls, waste
rock piles, or tailings impoundments) that influence the oxidation reaction, migration of the acid, and
consumption. Other downstream factors change the character of the drainage by chemical reaction .or
dilution. • •
K™SfSJ2 ...... S±5 ...... !,SJ! ...... ..... ..... ..... water, oxygen, ferric iron, bacteria to
................................................ " .................................. Jf^Jyze ..... the ...... oxidation i|reaction,| ....... and ..... generated ...... heat. ............... Some ....... sujfide ...... mjnerals. ....... are ...... rnorgiiisasi|ly oxidized
«ZI«^.g., ..... fean^dal ...... pyrite, marcasite, ....... and ..... pynirotite) ...... and ..... hence, ...... mayjiaye ...... a greater impact on tuning '
™_.__ ..... ....... _____ ..... ..... _ ........
Also, important is the
w|| ..... ,have ....... smallec
•••!• ' |l||il||i||||||i|IHIII 'f Ilillllllllllliiliiiiiiiiiii iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii inn iiiiiiiiiiiiiiiiii PI i' miiiiiiiiiiiiiiiiiiiiiiiin 11111111 in iiiiiiiiiiiiiiiiiiiii iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii"! ii mi i i iiiiiiii inn i iiiiiii n i n jiiiiiii in n~i
• exposed surface areas than those that are disseminated
IIIIIH^ •Illllilll IIIIIIIH^^^^^ -—.•••••.i»«^j.
Both water and oxygen are necessary to generate acid drainage. Water serves as both.a reactant and a
rGedhmi for bacteria in the oxidation process. Water also transports the oxidation products. A ready
of atmospheric oxygen is required to drive the oxidation reaction. Oxygen is particularly
' '
4-4 September 1994
-------
. EIA Guidelines for Mining Environmental Issues
important to maintain the rapid bacterially catalyzed'oxidation at pH values below 3.5. Oxidation of
sulfides is significantly reduced when the concentration of oxygen in the pore spaces of mining waste
units is less than 1 or 2 percent. Different bacteria are better suited to different pH levels and other
. edaphic factors, (edaphic factors pertain to the chemical and physical characteristics of the soil and
water environments). The type of bacteria and.their population sizes change as their growth
conditions are optimized (Ferguson and Erickson, 1988).
The oxidation reaction is exothermic, with the potential to generate a large amount of heat, and
therefore thermal gradients form within the waste unit. Heat from the reaction is dissipated by
thermal conduction or convection. Research by Lu and Zhang (undated) on waste rock using stability
analysis indicates that convective flow can occur because of the high porosity of the material.
Convection cells formed in waste rock would draw in atmospheric air and continue to drive the
oxidation reaction. Convection gas .flow due to oxidation of sulfide minerals depends on the
maximum temperature in the waste rock. The maximum temperature depends on ambient
atmospheric temperature, strength of the heat source, and the nature of the upper Txmndary. If the
sulfide waste is concentrated hi one area, as is the case with encapsulation, the heat source may be
very strong. Lower ambient air temperatures improve conditions for convective gas flow. If the
upper boundary is'covered, convection is less likely. .
Secondary factors act to either neutralize the acid produced by oxidation of sulfides or to change the .
effluent character by adding metals ions mobilized by residual acid. Neutralization of acid by the
alkalinity released when acid reacts with carbonate minerals is an important means of moderating acid
production. The most common neutralizing minerals are calcite and dolomite. Products from the
oxidation reaction (hydrogen ions, metal ions, etc.) may also react with other non-neutralizing
constituents. Possible reactions include ion exchange on clay particles, gypsum precipitation, and
dissolution of otherminerals. Dissolution of other minerals contributes to the contaminant load in the
acid drainage. Examples of metals occurring in the dissolved form include aluminum, manganese,
copper, lead, zinc, and others (Ferguson and Erickson, 1988).
Some of the tertiary factors affecting acid drainage are the physical characteristics of the waste or
structure, how acid-generating and acid-neutralizing wastes are placed in the waste unit, and the
hydrologic regime in the vicinity. The physical nature of the waste, such as particle size,
permeability, and physical weathering characteristics, is important to the acid generation potential.
Particle size is a fundamental concern since it affects the surface area exposed to weathering and
oxidation. Surface area is inversely proportional to particle size. Very coarse gram material, as is
found in waste rock dumps, exposes less surface area but may allow ah- and water to penetrate deeper
into the unit, exposing more material to oxidation and ultimately producing more acid. Air
circulation hi coarse material is aided by wind, changes in barometric pressure, and possibly
convective gas flow caused by heat generated by the oxidation reaction. In contrast, fine-gram
4-5 September 1994
-------
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I I ' II 1 1 1 11
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Enrironmental Issues EIA Guidelines for Mining
material (e.g., tailings) may retard air and very fine material may limit water flow; however, finer
grams exp^e more surface area to oxidation. The relationships between particle size, surface area,
and oxidation play a prominent role in acid prediction methods and in mining waste management
units. As waste material weathers with time, particle size is reduced, exposing more surface area and
changing physical characteristics of the waste unit. Though difficult to weigh, each of these factors
influences the potential for acid generation and are therefore important considerations for long term
waste management (Ferguson and Erickson, 1988; Lu and Zhang, undated).
- ", I ! Ii ' ; •'' ' ! ' - '
I I " I J I I , A I
The hydrology of the area surrounding mine workings and waste units is important in the analysis of
acid generation potential. When acid generating material occurs below the water table, the slow
diffusion of oxygen in water retards acid production. This is reflected in the portion of pits or
underground workings located below the water table. Where mine walls and underground workings
extend above the water table, the flow of water and oxygen in joints may be a source of acid. A
similar relationship is evident with tailings, which, are typically fine grained and disposed of
subaqueously; the slow diflusion of oxygen inhibits formation of acid. However, since tailings are
limited period of time during mine, operation. Following mine closure, the free water surface hi the
impoundment may be drawn down substantially, favoring ARD conditions. (Also, as tailings dry
ove| Imae, previously impermeable layers of fine material may develop cracks or fissures, providing a
,'I1 tjfi - .. ' in in , ii if 'iiiii iiiiiii in iiii' mum ill! i iiiii mm i n" in i ii • i i< iinn i iiiiiii i i i, 11 n
iiiiiiiiinifiiiiriii ii in i iiin^^ iiLiiiiiii \< • : » • '
spatial distribution of mining wastes in units, or waste placement, affects acid generation
i potential. For example, the distribution of acid generating wastes'with neutralizing wastes may be
|™J|! * !""'{l""" ,T|T"!'I II !!!! * '"I "!"""! " ! '• ! ! """i""1!!!1 " ' • '• -" i' • •'"!' ... '' r* ' • " ,
'•^ idling SS^SS^^)^ 2E stggfrinj* sequence^ ^Calcareous^ material may be mixed with or placed above sulfidic
wastes to buffer acid production or provide alkaliniry to infiltrating solution prior to contact with acid
generating wastes. An. alternative to layering or mixing is encapsulation. This technique attempts to
isolater,,acid generating wastes from oxygen and water, thereby reducing its gotential to Pfoduce acid.
Both tfiese tediniques are curreniy being used in waste rock dumps. It is unclear if they are effective
over the long-term, since highly acidic material may overwhelm the buffering capacity of calcareous
material or other alkaline sources. , _ ;
i , ii i i .
I i !
Wetting and drying cycles in any of the mine workings or other waste management units will affect
the character of any acid drainage produced. Frequent wetting will tend to generate a more constant
Volume of acid and other contaminants as water moves through and flushes oxidation products out of
the system. The _build-up_ °f f^njaminants m the system is proportional to the length of time between
1 wett|l prcies (Ferguson and Erickson,. 1988; Doepker, 1993). As the length of the dry cycle
! ""lincr^5S8 SiMllSS Pjrcxfacts will tend to accumulate in the system. A high magnitude wetting event
will then flush accumulated contaminant^ out of the system. This relationship is typical of the
' i II '
i
t
•
4-6 September 1994
in iiiiiiiiiiiiiiii IIIIIH^ 111 mi iiii iiiiiiH^ nil ii iiiii iiiiiii iin in iiiiiiiiii ill i in iiiiiiiiiiiiii i iiiiiiiii i iiiiiiiiiiii i ill iiiiiii n
"I | | II Ill I I I Ill Ill I I I I I Ill II 1 1 1 1 1 1 11"
-------
ElA. Guidelines for Mining . Environmental Issues
increase in contaminant load observed following heavy precipitation for those areas having a wet
season.
4.1.2 ACID GENERATION PREDICTION
The objectives of predictive testing are to (1) determine if a discrete volume of mining waste will
generate acid, .and (2) predict the quality of the drainage based on the rate of acid formation measured
(California Mining Association, 1991). There are two important points that must be considered when
evaluating the acid generation potential of a rock material. The first is how to collect samples from
the field for use in analytical testing. The second is which analytic test method should be used. Both
points have a profound impact on the reliability of analytical tests. Results from any analytical test
are only as reliable as the samples used for the test. Once the sampling strategy is selected, an
appropriate analytical method or methods can be selected. Methods used to predict the acid
generation potential are classified as either static or kinetic. Factors affecting the selection of
sampling regime and analytical method include an existing knowledge of the geology, costs, and
length of time available to conduct the test. This section will examine sample methodology and
analytic tests used to predict acid generation potential.
The following list of components describes the solid phase composition and reaction environment,of
sulfide minerals. Potential contaminants are included to indicate their importance in the scope of acid
generation. These components should be kept in mind while evaluating information on acid
•generation potential. . •'
Components affecting the total capacity to generate acid are characterized by:
• Amount of acid generating (sulfide) minerals present (assuming total reaction of
sulfide minerals)
• Amount of acid neutralizing minerals present
• Amount and type of potential contaminants present.
Components affecting the rate of acid generation include:
• Type of sulfide mineral present (including crystal form)
• Type of carbonate mineral present (and other neutralizing minerals, as appropriate)
• Mineral surface area available for reaction
Occurrence of the mineral grams hi the waste (i.e., included, liberated)
Particle size of the waste
4.7 September 1994
-------
EIA Guidelines for Mining
* Available water and oxygen
'; in^^ •
^^
Bacteria.
1 '
used to assess a material's acid generation potential are either static or kinetic in
determines both the, tgtal, acid-generating and total acid-neutralizing potential of a
capacity of the sample to generate acidic drainage is calculated as either the difference
QZ as a ratio of the values.. Tjiese tests are not Intended to predict the rate of acid
; potential to produce acid. Static tests can be conducted quickly and are
inexpensive compared to kinetic tests. Kinetic tests are intended to mimic the processes found in the
' at an accelerated rate. These tests require more time and are
considerab.ly_inote .expensive than static tots. Data from the tests are used to classify, wastes.
Sg to their add generating potential, fhls^mformation can be collected and evaluated during"'
^
$ ...... sconojnie ...... analysis ....... of mines. ....... in their exploratory phases. Based on this information, management
Zdecjsions can be made with respect to specific mitigation practices.
I '•• ;• " '".'. .• • • , . .M . ' : '
* 1 .......................... ; ......... ; [[[ [[[ ;; [[[ ; ........................ ;, .............. ; ......... : .............. ; ........................................ ; ............................. ; ......... ; [[[ I .......... ; [[[ ; ...........................................
ESprts ..... tyboflnjK ..... mining ....... industry ...... and ....... S^^egulatory ...... agencies ...... to ....... devdogthe ..... best protocols for
—— — — — _ _ potentjaj j^^ Demonstrated that site-
specific conditions (e,g., climate and geology) dictate a case-by-case approach when evaluating acid
F^B^" ........... |TMS| ...... is ....... co^licated ..... by the fact that ..... a ..... variety ...... ofresearch ...... effom ....... on ...... different ...... methods, by
the JBureau..^ MSie$^ EPA, and iie Canadian MJne E^^onment Neutral' Drainage (MEND), as well
as those used by minmg companies and then: consultants, make comparison of data difficult. Several
researchers have conducted comparative evaluations of predictive tests (Lapakko, 1992; Bradham and
CaswxJo, 1990; Coastech, 1989). Lapakko, of the Minnesota Department of Natural Resources, has
conf uct«l ajroparative evaluations of static and kinetic test methods using a range of rock types.
Bradham ....... and ...... Caruccio ...... conducted ..... a comparative study on tailings.
When evaluating the acid generation potential of a waste, a phased testing plan selects samples
appropriate for the detail needed (CaUfornia Mining Association, 1991). This approach allows
investment in acid prediction testing to be commensurate with a deposit's economic potential and
'associated with unnecessary tests. Sampling and testing should be an iterative
nd evaluating a small amount of information to establish the acid
S™ S S£ SSSS^ *>*<&*&> subsequent sampling and testing can be
•'selected to refine .the information as needed.
I" _ i i i i i '
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EIA Guidelines for Mining . * Environmental Issues
1. Define the geologic (or litfaologic) units that will be encountered during mining. Describe
the geology and mineralogy of these units in detail..
2. Develop a sampling plan based on understanding of geology (rock mass, etc.). Collect
samples to represent ranges of compositional variation within a rock unit (see Lapakko,
1988, 1990a).
3. Select static or kinetic tests and evaluate potential for acid formation.
4. Evaluate sampling criteria and conduct additional kinetic tests as required.
5. Develop a model as appropriate.
6. Based on findings, classify geologic (lithologic) units as acid, non-acid forming, or
uncertain. (Note: the potential to produce acid may vary within a given geologic unit.)
4.1.2.1 Sampling
Selection of samples has important implications for subsequent acid prediction. The purpose of
testing rock material is to allow classification and planning for waste disposal based on the predicted
drainage quality from that material. Samples must be selected to characterize both the type and
volume of rock materials and also account for the variability of materials that will be exposed during
mining. When to collect samples for testing is an equally important consideration.
Researchers agree that sampling and testing should be concurrent with resource evaluation and mine
planning (Lapakko, 1990a; British Columbia AMD Task Force, 1989). Sampling techniques used to
evaluate recoverable mineral resources (assay samples) are similar to those required for prediction of
acid generation potential. Active mining operations for which predictive tests were not conducted in
advance of mining lack the advantage of front end planning, but can still use sampling and other site-
specific information (e.g., geology and mineralogy) to establish the acid generating potential.
The pressure is increasing for new operations or those in the exploratory phase to accurately predict
future drainage water quality. By comparison, the acid drainage potential at old mines may be well
established. Examples of information needed from existing operations are the quantity of existing
acid products; the potential and stage of acid generation in each of the waste units, and the acid
forming potential of future wastes to be generated. Broughton and Robertson recommend that the
first two stages of an acid prediction analysis for either new or existing mines are (1) to review .the
geology and mineralogy and (2) classify the rock and collect samples (Robertson and Broughton,
undated; Broughton and Robertson, 1992).
Sample collection for prediction tests for both old and new mines should consider both geologic and
environmental factors. Geologic factors for sample selection are primarily a good understanding of
the local geology. If available, this may include information from mines, core logs, or other sources
4-9 September 1994
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EIA Guidelines for Mining
in the immediate area. This information is important to both the sampling program and application of
test results. Environmental factors include consideration of the potential environmental contaminants
in tne rocjc and climatic variables. A quality assurance/quality control program should be developed
and coordinated with the mine plan for sample collection and acid generation testing.
1 i ' ' '"" ' ! , ; ! ; : " " I
There are many opimons concerning the number of san^Ies to be collected in a fixed-frequency
sampling program. One mining consulting firm recommends about 8 - 12 samples of each significant.
type or a minjmum of one sample for each one million tons (Schafer, 1993). In this case a
significant rock type represents one or two percent of the total mine rock volume. ^ A representative
of the U.S. Forest Service suggests'that one sample (about 1,500 grams) be collected per 20,000 tons
of waste rock, or about 50 samples for each one million tons (U.S. Forest Service, 1992). These
":" I fciL: -si Pllli || ! !;: ! T '• »4i a I '• » Iiii -•
would be coUected oy compositing cuttings from individual drill holes made prior to blasting.
The British Columbia AMD Task Force recommends a minimum number of samples based on the
" sj I ' ' ! ' ' ijij " '"'"""'!'"'""" J| '" '""" ! ' ' I "" ' ! | ' | I ' " ' i,
, mass of the geologic unit. Their recommended minimum sample number is 25 for a one million ton
geologic unit, or one sample for every 40,000 tons. Using the British Columbia method, as waste
volume increases, the proportional number of samples decreases. For example, for a unit of 10
million .fogs, the minimum sample number is 80, or one sample for every 125,000 tons (British
Columbia AMD task Force, 1989).
There are reservations to prescribing a number of samples for collection per volume of material..
This is particularly true for existing mines when collecting samples from waste rock dumps for acid
generation potential tests.- -Waste rock .dumps are usually constructed by endkiumping rock from
trucks, creating heterogeneous deposits that are very difficult to sample with confidence. Tailings are
. comparatively more uniform due to milling and depositional methods used, and it is easier to charac-
terize their variability. Fixed-frequency sampling does not rely on the use of best judgment on the
part of tie sample collector (typically a mining company). It also does hot provide the statistical basis
to account for variability among samples. Therefore, the actual numbers of samples to be collected
should be determined on a site-specific basis. ' .
ii ' , • ' 11 ' i i'
•
1 * ' .
Factors to consider in a sampling program for existing or planned mines include the method of
•iiiii i" 1 a ' t • • • • -.
sample collection, length of tone samples are-to be (or have been) stored, and the sample storage
environment. Each of these can affect the physical and chemical characteristics of a sample. Samples
collected from cores exposed to the environment may be physically and/or chemically altered. If
samples are collected from a drill core, contamination may be a problem if a lubricant was -used. At
existing mines, tailings samples should be taken over a variety of depths to determine if oxidation of
sulfid minerals is occurring. The influence of lime addition during milling may maintain alkaline
Collecting samples of waste rock is difficult because of the variability inherent in these
waste units. Drilling is considered to be the preferred method for collecting samples from waste rock
iiSSwiHi dumps (Ferguson and Morin, 1991).
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-------
. EIA Guidelines for Mining __ Environmental Issues
Since individual samples will be used to test and classify larger volumes .of waste, it is important to
.consider how representative samples are to be collected. Compositing is a common practice used to
sample large volumes of material. Typically, composite samples are collected from drill hole cuttings
on benches prior to blasting. However, compositing merges information about the variation of
sample that would be identified if more samples were collected and analyzed. Therefore, information
about sample variability is lost (British Columbia AMD Task Force, 1990; Robertson and Broughton,
undated). Composite sampling of tailings may be useful as a "first look" for characterizing tailings;
compositing with stratification by lithology and alteration can help to avoid the problems of simple
composite samples (Schafer, 1993).
To be most effective, sampling programs for acid generation prediction should not be confined to
initial prediction during mine permitting. The uncertainties associated with sampling, analytical
techniques, and prediction methods all serve to make continued sampling and prediction appropriate
throughout the life of a mine. This can allow early identification of changed conditions that can lead
.to problems, and thus allow early intervention to prevent major impacts.
4.1.2.2 . Static Tests
Static tests predict acid drainage by comparing the waste sample's Tnaxhrnim acid production potential
(AP) with its maximum neutralization potential (NP). The AP is determined by multiplying the
percent of total sulfur or sulfide sulfur (depending on the test) in the sample by a conversion factor
(AP — 31.25 x %S). NP is a measure of the carbonate material available to neutralize acid. The
value for NP is determined either by adding acid to a sample and back-titrating to determine the
amount of acid consumed or by direct acid titration of the sample (the endpoint pH is dependent on
the test method). The net neutralization potential (NNP), or acid/base account (ABA) is determined
by subtracting the AP from the NP (NNP = NP - AP). A ratio of NP to AP is also used. An NNP
of 0 is equivalent to an NP/AP ratio of 1 (Ferguson and Morin, 1991). Units for static test results
(AP, NP, and NNP) are typically expressed in metric tons of calcium carbonate (CaCO3) per 1,000
metric tons of rock. . . •
If the difference between NP and AP (i.e., the NNP) is negative then the potential exists for the waste
to. form acid. If it is positive then there may be lower risk. Prediction of the acid potential when the
NNP is near zero (between -20 and 20) is especially difficult (Brodie et al., 1991). Similar to Brodie,
Smith and Barton-Bridges also suggest an NNP criteria of greater than 20 where the risk of acid
generation is low (Smith and Barton-Bridges, 1991). Other studies conducted by the State of
Pennsylvania on surface coal mine drainage suggest that sites with an NNP of greater than 10 exhibit
alkaline drainage, with a gray zone ranging from 1 to 10 (Brady et al., 1994). Finally, the State of
Tennessee has encountered acid generation (along with elevated iron and manganese levels) in
backfilled portions of six area coal mines, where positive NNPs were initially observed (some
samples had NPPs between 5 and 20, but averages were generally greater than 20). The
4-11 September 1994
-------
Environmental Issues
EIA Guidelines, for Mining
iiB^ • 'isiiim iiw
„ _ :
inconsistency between test results and actual conditions has been attributed to carbonate materials with
;;; slow djssdutionxate^ heterogeneity between carbonate and sulfidic materials, and the availability of
ItflMW Ill
...... SSi
SHI ..... Sll I ...... fits ..... Sfil ....... if 4 ..... §iPPle's neutralization potential to acid
= ^production potential is greater than 3:1, experience indicates that there is lower risk for acid drainage
_ -J !t- * ,; . .j» ' '•• I'1 »'•' " •' ' '• ' .', . : . . ,., •' • -' • • '• i'1 ' ' f-'IT '-, ',.|T >,& •
to develop. Those samples with a ratio of 1:1 or less are more likely to generate acid. Brodie refers
to ratios between 3:1 and 1:1 as the zone of uncertainty, where additional kinetic testing is usually
reco^nmended and acid mitigation measures may be required (Brodie et al., 1991). Data from coal
mines in the eastern United States indicate that an NP/AP of greater than 2 A is required to ensure
acMl will not bereleased, (Cravotta et al., 1990). ^Finally, data from a single Canadian mine stow that
an NP/AP of up to 4.0 must be maimafrwid te-provide for near neutral drainage. Morin and Hurt
suggest that the criteria for detennining ABA should be established based on site-specific conditions
i I (Morin and Hutt, 1994). * .
*
in1 if in
non-acidic conditions ^(tie early phases of ARD are often under pH neutral conditions), coating of
carbonate grains by precipitated hydroxides, and climatic factors that lead to faster weathering of
catf)0nac£0us materials than sulfide materials (Day, 1994). When reviewing data on static tests, an
waste or
[[[ SS ..... ,S£ ..... ...... SaSSl ......
in ..... Exhibit
IS! ...... S2SlSS|!Pg static testing. Five types of static tests are
'
11 IF in i
orative ,S!2!!, ,525, Performed by Lapakko (Lapakko, 1994a)ona
wSc range of sampjes using the ABA/fte modified,ABA, the BC method,' and the, modified BC test
IIIIIIH
methods (pressed by Lapakko). Lapakko's results suggest.that the ABA and modified ABA methods
tend tQ overestimate actual neutralization potential (and potentially underestimate acid generation).
""- nC and modified BC methods results most closely correlate to the actual mineralpgic NP. As
t in Exhibit 4-|s the modified Bg process determines NP by titrating to pH = 6.0 rather, than
The
•v- ''
Kinetic tests are distinguished from static tests in that they attempt to mimic the natural oxidation
reactions of the field setting. The tests typically use a larger sample volume and require a much
kni"" time for completion than do static tests. These tes|§ provide information on the rate of sulfide
mineral oxidation and therefore acid production, as well as an mdication of drainage water quality.
-------
EIA Guidelines for Mining
Environmental Issues
S.
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Environmental Issues EIA Guidelines for Mining
Of the different kinetic tests used, there is flo one test that is preferred. The preference for tests
1 changes with time as experience and understanding increase.' In a 1988 summary article by Ferguson
and Erickson, the B.C. Research Confirmation Test was considered to be the most widely used. A
similar 1991 article by Ferguson and Morin stated that the use of modified humidity cells was
becoming more common, and mere seems to be a trend toward the preference for modified humidity
cell and column type tests. Six types of kmetic tests are summarized m Exhibit 4-2.
Kinetic tests can be. used to assess the impact of different variables on the potential to generate acid.
For example, samples may be inoculated with bacteria (a requirement for some tests). The
temperature of the sample environment may also be controlled during the test. Most tests require the
sample particle size to be less man a specified sieve size (e.g., minus 200 mesh). Larger sample
volumes and test equipment may examine acid potential from coarse particles. Acid drainage control
by adding lime, may also be examined using kinetic tests.
II-
It is helpful to supplement kinetic tests with an understanding of empirical data characterizing the
sample. Examples include analysis of specific surface area, mineralogy, and metals. Such
................ ! [[[ infojtma^gn ..... nog affect the interpretation of test data and are important when making spatial and
es,based on the. test data. As with static tests, it is important to '
J
consider the ..... particle ...... size ..... of the ...... test ...... sample, particularly when comparing test results with field scale
applications.
.............................. I [[[ ;•• [[[ ' [[[ .................................................. ' [[[ '
4.1.2.4 .............................. Application of Test Results in Prediction Analysis ' . '
Results from static and kinetic tests are used to classify mine wastes on the basis of their potential to
generate acid. Static tests yield information about a sample's ability to neutralize acid and generate
acid,,, JEedjSereoge ..... or ..... ratio ...... ofjhese ..... vajues.bjegojnes. ....... the ..... b,asjs ....... of .the, ...... classification. { As discussed
above, for samples with NNP values greater than 20 tons CaCCyi.boO tons of waste and/or jjp^p
ratios of greater than 3.25:1, the potential to generate acid is low (Smith and Bartort-Bridges, 1991).
For ..... NNP ..... values ..... tetwegi ..... :20 ..... and ..... 20 ....... j&fos between ........ 1:1 ....... and, ...... 3.25:1), the potential for acid generation
remains, and uncertainty will exist, (ft is important to note that each of these values are generalities
and can be af&cted by a wide range of site-specific conditions that can either promote or retard ARD
generation; the relative aya||abi|fty of surface areas of iron sulfides and calcium-magnesium
carbonates, reaction rates, drying/wetting conditions, etc.)
•
The determination of AP based on estimated or reactive sulfur content in the sample has some
iaherem limitations. When total sulfur is used as the basis to estimate sulfide content, this uncertainty
S2X ...... If, ...... aanbutabte ...... to possible ...... errors ....... in ..... (1) ....... assessment ...... pfjrue acidity and neutralization in the
2£2£!e,i ........ SI ..... calculated ..... acidity based on total sulfur conversion value; and (3) analytical error. Similar
errors pxist for static tests that determine reactive sulfide mineral concentrations. Estimating long-
-------
EIA Guidelines for Mining
Environmental Issues
<
•
Exhibit 4-2. Summary of Some Kinetic Test Methods, Costs, Advantages, and
Disadvantages
'Humidify Cells
(Sohek«ud.r1978> -' -
-2.38 mm panicle size
200g of rock exposed to three days dry
air, 3 days humidified air. and rinsed
with 200 mL on day 7
cost: 425-850
''•'• .Soxhdei Extraction
(SingHnn and Lavkulich,. 1978;; Sullivan
- and Skibek, 1982)'
SUMMARY OF TEST METHOD
T=70°C (Singleton and Lavkulich,
1978); T=2S-C (Sullivan and Sobek.
1982); water passed through sample is
distilled and recycled through sample
cost: 212-425
x • Column Tests -,.. •
•(Brnynesteyn and Hackl. 1982; Hood
and Oenel, 1984)
variable panicle size
columns cotitHininR mine waste are
leached with discrete volumes or
rechculating solutions
cost: dependent upon scale
ADVANTAGES AND DISADVANTAGES
models AP and NP well and models
wet/dry;3 approximates field conditions
and rate of acidity per unit of sample
moderate to use. results take long tjine,
and some special equipment1
moderate ease of mterpretation;u large
Source: Lapakko. 1993b)
•":. '?%B -(Duncan -and Walden; 1975)
simple, results in short time, and
assessment of imenction between AP
andNP3
moderate to use and need special
moderate iiHe«iietation'J in
developmental stage and relationship to
' Batund processes not clear*
Batch Reactor .: ' ';••
(Halben et al;;;i983) j*? -MS . :
models AP and NP, models effect of
different rock types, models wet/dry,
and models different grain sizes1
difficult interpretation, not practical for
large number of samples3
large volume of sample2 lots of data
generated, long time,- and potential
problems: uneven leachate application,
• channelization3*3
., ,.; ' -. • -Field Tests.-. ••> '.
•%?*•?•• (Egerand.LapaHco, 1985)
METHOD
-400 mesh panicle size . '
15-30g added to bacteriauy active
solution at pH 2.2 to 2.5, T=35*C; if
pH increases, samole is non acid
-200 *ng
-------
* " Enrironmental Issues
I II I II I I I II II I nll III I III1! 11
EIA Guidelines for Mining
,
term reactive sulfide based on short-term tests may result in uncertainty due to difficulties in making
* oxidatiqn rate predictions (British Columbia .AMD Task Force, 1989).
Acid base accounting tests conducted on an iterative basis, where the initial sample set is small, are
helpful when establishing boundaries between lithologic units. As data from static tests is collected"
, the sampling selection can be refined.. The goal of, sampling is to collect representative
samples that define the variability of the lithologies present If significant variability in the acid
generation or neutralization potential is identified in the initial sample test results, additional sampling
to refine ..... lithologic boundaries is 'necessary (California Mining. Association, 1991).
Kinetic tests are often conducted to confirm results of static tests, to test the potential for ARD' hi the
uncertainty zones of static testing, and to estimate when and how fast acid generation will occur. •
These tests provide insight on the rate of acid production and' the 'water 'quality potentially produced
method for evaluating test results. Data are examined for changes through time and water quality
characteristi.es. ' Kinetic tests tend to accelerate the natural oxidation rate over those, observed in the
field. This may have lie advantage of condensing.time, and providing earlier insight into the
......................... :. ..... potential for acid generation.
•IB .....
............. ................ Jill .......................... If. ..... I ............. i! ..... *,. ...... ! ........ ' ............. .i! ................ l> ........ ,;• ....... I ....... I ........ I ......... ij| ...... ' ....... Illiiill ......... IK ........ (Ilill! ......... ill ..... i ............ I ...... inn* ..... !!li| ..... • ........... 'ill ........... Ill ........ | ..... i>> ...... /P! ..... Hill!1' .....
Generally, kinetic tests are evaluated for changes hi pH, sulfate, acidity and a host of potential ,
According to the British Columbia AMD Task Force (1989), samples with pH values less than 3 are
. i ; , considered strongly acid; between 3 and 5 the sample is acid-generating .and there may be some
; " neutralization occurring; at pH values >5, the sample is not significantly acid or an alkaline source is
neutralizing the acid. Sulfate is a by-product of sulfide oxidation and can be used as a measure of the
i. When evaluating test data it is important to examine the
ion curve as an indicator of sulfide oxidation, in addition to other
parameters. An analysis of metals in the sample solution serves as an indicator of contaminant load
not usually a good indicator of acid generation.
4.1^^ Experience With Static and Kinetic Tests
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: of mines it is easy to determine the likelihood for acid
"" generation to be a problem. For some, acid generation would be expected; for others, it would
definitely not be expected. Predicting the potential for the other 50 percent is more difficult (U.S.
EPA, 1992). When data collected from static and kinetic tests is inconclusive, it may be necessary to
extrapolate from existing data using oxidation rates and other factors and project how a sample may
~ ^^ «| I ' , ' II, _, I ;*,„ ,*
reiMct. The soundness of the extrapolation is dependent on the representativeness of the sample, -
accuracy_of Jhe tests data, and the interpretation of the data.
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-------
EIA Guidelines for Mining Environmental Issues
Ferguson and Morin (1991) found that samples with an NP/AP ratio of less than 0.1 tended to
produce acid during typical laboratory timeframes. They expected that if laboratory tests were
conducted for longer time periods the NP/AP ratio would shift closer to 1 and did not speculate on
what the values for NNP and NP/AP would be in the future. Extrapolating a sample's ability to
generate acid was divided into short (less than one year), medium (a few years), and long term (many
years) time frames. Short-term projections are based on laboratory data. Medium-term projections
require knowledge of the neutralization process, primarily consumption of carbonate. Long-term
extrapolations of acid generation potential will require an understanding of weathering rinds and
diffusion of oxygen into and reaction products out of that rind. Long-term projections were identified
as being extremely difficult.
Researchers hi British Columbia have examined results of static and kinetic tests conducted on tailings
and waste rock (Ferguson and Morin, 1991). The results are based on a study of 20 active or
abandoned mines in British Columbia. Their findings indicate that for tailings, only those samples
having a negative NNP produced acid. The test method was not identified and the limitations are
therefore not discussed here. According to mis report, waste rock data from static tests is very
limited and demonstrates the variability expected with these waste units. They observed that samples
of waste rock that had weathered for one month (prior to sample collection) needed to be flushed
initially to remove existing oxidation products. ,
Lapakko (1990b) used solid phase characterization of the sample in conjunction with acid base
accounting data and the rates of acid production and consumption to extrapolate information beyond
the timeframe of kinetic tests. The rates of acid production and consumption were based on kinetic
test results over a 20-week period. The time required to deplete sulfide and carbonate minerals was
determined using rates established from kinetic tests. Based on these observations the .time required
to deplete the iron sulfide content was 950 weeks and the time to deplete the carbonate content was 40
weeks. This prediction agreed with an observed drop in pH between week 36 and week 56 from 8.7
to 6; after another 20 weeks the pH dropped below 5.
4.1.2.6 Mathematical Modeling of Acid Generation Potential
As the preceding discussion indicates, static and kinetic testing provide an incomplete picture of the
potential for mine wastes to produce ARD. Static testing estimates the ultimate AP and NP of waste
material but is generally silent with regard to the rates of generation of acidic and alkaline flows in
actual waste matrices. Kinetic testing is more helpful with regard to estimating the rates of oxidation
and neutralization within waste units. However, as discussed above, actual waste units can be very
non-homogenous and anisotropic with respect to the distributions of mineral types, particle size,
hydrologic conditions and so forth. Thus, while a given kinetic test may well approximate the
potential for ARD hi a portion of a waste unit, the result may not be representative of the "global"
potential for ARD. Equally important is the practical limitation on the duration of kinetic tests:
4_17 September 1994
-------
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Illlllll ill Illlllll III"
Environmental Issues
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, ,
lead to erroneous cgrahunoiB if they result in the omission of important
instance, failure to consider the presence of neutralising mat-rials in & -waste
pile could result ^ an overestiniation of the rate of acid generation. Similarly, failure to consider
hydrogeochemkal conditions within a waste pile may pzsc&de consideration of adsorption/
precipitation reactions involving metais, thereby miscalculating the potential for metals loading in
effluent streams. Because the importance of any given crairmUmg factor may vary from site to site
(and from time to time), me sigmficBice of a snnplifymg assumption far any particular modeling
....... effort 'must ...... be
"carefiulyT .......
Empirical Models
As stated above, empirical models extrapolate values of sulfide oxidation from existing laboratory and
field test data. The method of extrapolation typically involves determination of the "best-fit lines"
through test data points (British Columbia AMD Task Force, 1989). The equations so derived may
4-18
September 1994
Ij i i "ii1 i i i ni
-------
EIA Guidelines for Mining Environmental Issues
then be solved to provide, for instance, the acid generation rate of a particular waste unit at some
time in the future. Using the projected acid generation rate as an input to a separate
hydrogeochemical model that accounts for attenuation of seepage constituents in soils and dilution in
receiving waters, the estimated constituent loading rates and consequent receiving water quality at
time T may be estimated (Broughton and Robertson, 1991).
Empirical models generally do not explicitly consider the causal mechanisms driving oxidation of
sulfides and neutralization of seepage. Rather, such models assume that the operation of such
controls is accurately represented in the test data, Therefore, the accuracy of empirical models in
predicting ARD depends heavily on the quality of the test data used in the models. Principal sources .
of uncertainty may be expected to include variations in the spatial and particle size distribution of
sulfide and alkaline minerals not captured by the data due to insufficient spacial distribution of
samples; changes in the distribution of particle sizes throughout the waste unit (due to weathering) not
captured by the data; and failure to accurately calibrate the model to reflect the actual quantity and
type of materials (British Columbia AMD Task Force, 1989).
It is important to note that empirical models, by then: nature, are site-specific. Because the models
rely on actual trends observed at a specific site, rather than generic causal mechanisms, the best fit
lines for one site cannot be assumed to be representative for another site. Further, significant changes
in waste unit composition, geometry, or controls over time may invalidate previous representativeness
of empirical models. Nevertheless, empirical models may provide cost-effective and reasonably
reliable estimations of short-term future ARD conditions for sites with sufficient spatial and temporal
data.
Deterministic Models
Deterministic models simulate ARD.by solving systems of equations that represent the various
controlling factors in the waste reaction process (Broughton and Robertson, 1991). The simulation
approach allows the users to examine the potential sulfide oxidation rate and resulting seepage quality
over periods of tens to hundreds of years in the future. The greatest promise of deterministic models
is that they may allow the user to predict ARD as it evolves over time under the changing influence
of rate-controlling factors. Existing models have built upon earlier work on acid releases from coal
mine spoils as well as work on leachate quality in metals heap leach operations (Nicholson, 1992).
The models may rely solely on the causal relationships described in the equations, or may include
empirical data as exogenous drivers (outside the model structure) to solve for certain aspects of the
system (Nicholson* 1992; Broughton and Robertson, 1991). The most important differences between
the models lie hi the particular causal mechanisms (e.g., oxygen diffusion, changing particle size,
temperature variations due to exothermic reactions) addressed within each model structure.
4_19 September 1994
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EIA Guidelines for Mining
Nicholson presents a review of ARD models, in that review, Shumaten (1971), as cited in Nicholson
[[[ ffSls ........ £ ....... S2S22 ....... SS£,,SS5S ...... reggfijzing *£ ...... SS2S ...... of&ygen with™ nun6 rock limits the, overall
raf6 of oxidation of sulfides (Nicholson, 1992). The first working models to incorporate this process
(Mortfa, 1972; Rica and Chow 1974; both cited in Nicholson, 1992) used the acid generation rate to
calculate resulting drainage water quality. Rittchie (1977),'as cited in Nicholson (1992) added to this
..... "•* ...... 3"«2 ..... "22153 ....... fo,L£e, ..... SSSi ....... 2l,,s£3S ..... sife ..... Ssi ...... Ite ...... gsss ...... sCssisfele
il ............................ ....... pnreacted sulfide. Jaynes et'al'., working ^wftfa a model of pyriticsiiaie ...... in ..... coal-mine ...... spoils, assumed
pyritic particles to oxidize as shrinking cores of unreacted material surrounded by an outer layer
e ...... ,52, ..... §E!S5S! ....... SS13S2I ...... ass, ...... atpxygen,
; &« £J!jiJ5£gi§ £25 grovidesa smaUerjrcactive surface area. ^ermodelg, have incjud.ejl
cbnvecSon as a means of ,ox|gen" transport within waste piles (Lu and Zhang, undated). Convection
i may tejjnfiuffl^ed by_ ichaiges in barometric pressure or by the release of heat from the exothermic,
; of SMlfifieg,.,, Ssmg jeisficierstove modeled the feedback;mechanisms operating between
nd^ojogcal and chemical oxidation rates, noting that the, mechanism is only significant
32SS P*1:!!??3^1*68 a"^^gh enough to allow convective oxygen transport to occur (Nicholson,
1992).
. ..... ^Ae Igrdrolggc ...... and^geTChemical ....... conditions,, m ..... waste unit matrices,
as well as reaction product transport, to more realistically represent changes in seepage quality
(N^^kpn? 1992). Bennett (1990) andoifaers found that water flow through the waste pile strongly
influencf2l ...... 2S£ ..... 23JjJ!ttj
-------
Guidelines for Mining - Environmental Issues
Notwithstanding the understanding that existing models have provided, ARD models to date have not
found extensive applications in predicting oxidation rates and effluent quality at operating or proposed
sites (Ferguson and Erickson, 1988). As stated above, models are simplifications of reality, and
consequently are subject to a high degree of uncertainty. Among the sources of uncertainty are
incomplete or invalid model structure; natural variability of certain parameters; and lack of parameter
calibration and model verification (British Columbia AMD Task Force, 1989).
Incomplete model structure leads to uncertainty in predictions by ignoring potentially important rate
controlling factors. In general, incomplete model structure .results from an incomplete understanding
of the system being modeled, or the overuse of simplifying assumptions (British Columbia AMD Task
Force, 1989). For example, failure to accurately account for water flow within the waste matrix .
prevents consideration of the thermal gradient within the pile, the transport of oxidation and
dissolution products, and the conduction of oxygen via water. It is worth noting that modeling water
flow in waste rock piles presents greater difficulties than in tailings piles, and has received little
attention to date (Nicholson, 1992). For this reason (among others), waste rock pile models are
subject to a higher level of uncertainty.
Natural, variability of some parameters of a system can lead to uncertainty in model predictions. For
example, changes in rainfall patterns, which directly effect the hydrologic conditions in the waste pile,
are difficult to predict with certainty. Likewise, particle size distribution and mineral type distribution
throughout the waste pile can be highly variable and difficult to predict.
Among the greatest concerns lacing the reliability of predictive deterministic models are model
calibration and validation. Model parameters must be adjusted to match the conditions prevailing at
an actual she. Therefore, reliable waste characteristics, hydrologic and geochemical data must be
collected and incorporated into the model structure. Validation requires comparison of model
predictions with actual field sampling results. To date, the availability .of field data for validation is
very limited.
4.13 ARD DETECTION/ENVIRONMENTAL MONITORING
•>
Where there is the potential for encountering sulfide mineralization, an assessment of potential
impacts should include appropriate testing for ARD potential (using one or more of the methods
described in the previous section). Where testing results demonstrate potential for ARD generation or
where such test results are inconclusive (particularly in sensitive environments), an applicant's
environmental monitoring program should include specific testing directed at early identification of
ARD. This should involve sampling of effluent streams as well as surface water and groundwater.
Existing data on ARD generation indicate that it is highly variable. (Mine discharge sampling data
compiled by the British Columbia Acid Mine Drainage Task Force at sites with known ARD
4-21 September 1994
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Environmental Issues EIA Guidelines for Mining
generation show significant day-to-day variability in pH and concentrations of dissolved metals.) As a
result, regular monthly or quarterly sampling ([commonly used to monitor effluents/impacts from
|| 11| illllJ nil j|||||||||jjj||||||||l I llJlllllllllllllllll IIJII lllllllllllllllllllllllllliiilllliilllllllllllllli ill II Ill II liliiiiillll£llliilllillillllllllllllllilllllililliilillli!lli I Illlll I II Illil Ill I |l II I lillnl II li|i|lil|||ii||||l III i IIII ' || II " j\ II |i| iinliwiiiililni .nr iiiiinniih
industrial operations) may not be adequate to detect ARD generation. Where ARD is a potential
concern, baseline studies should be designed to establish conditions where ARD is likely to occur.
Monitoring programs during and after operations should be tailored to address the factors that affect
ARD generation. These factors include:
* Seasonal Variability. Most mines where ARD is observed exhibit seasonal variability in
'"! " ARD generation (except underground "adit discharges which" are relatrvelyulu^pactied by
~= •"-" |': ~ "'™ changing seasonal conditions). Generally, either the first rain after a dry season or high
!!! " ' 35owm§(t pencils ——--^ gggjy to produce ARD. (ARD generation can be' specifically
increased by the buildup of salts on rock surfaces during dry conditions.)
I ', • •: . I. , • '•' ; ',' • '[
' Treated Effluent Variability. At mine sites, the treatment system effluent quality may be
variable due to different influent volumes and characteristics—for, example, where natural
conditions affect the influent flow and composition. For example, potentially acidic mine
UH||i . I, „ (| water and runoff may be significant influents to the system under" certain "conditions. " '
I1"' i ^ 11 "" 11 iill ' i i
BBIBfiiji ' ii ii • Impacts on Aquatic Life. The actual effects of ARD on a receiving water may be •
. dependent on the behavior/occurrence of specific aquatic life within the watershed. For
. example, the presence of migratory species may suggest the need for monitoring during
m^at in mm iiiiii specific time periods. Similarly, seasonal releases of ARD may •occur during critical life
••' >l !•*' I)M* stages of inuiviiiiial species. ' ' ' •' " ' '
• Stream and River Effects. Streams and rivers may be heavily impacted due to .sudden
high releases of ARD (especially where there is limited dilution). In snowmelt areas,
I impacts can be particularly significant when a melting at the mine site occurs during a
different time period than other areas within the watershed (thereby reducing dilution).
I Sampling plans should consider when "maximum" flows/discharges can be expected.
• " Lake Effects. In lakes, the, effects of ARD may be impacted by physical and biological
conditions in the lake. In designing a monitoring plan, factors such as thermal
[ " stratification, turnover events, flushing rates, and .seasonal .cycles of aquatic life growth.
should be considered. ' ,
,1'
jii •. ..... ,• . , ••!> . . •„.„:;=,,..' .- >,- ..... ,,. , • ,
As stated above, baseline and operational monitoring programs should be designed to address each of
•iiiiH^^ iiiiiiiiiiiiii the above factors. A reasonable; cost-saving option is to provide for frequent pH or other ARD
|« 111 Illlll I. I I ........... I ........ I [[[ ............... I ......... I ................... I .................... "I [[[ I [[[ '=>' ........ .......... * ..... ! [[[ — [[[ i .............................................. =- [[[ • [[[
!'"' [[[ indicator (suliate, ........ alkalirugr, ....... etc.) ....... mpnftonnj; ...... of ..... effluent ..... discharges ....... and ...... ground and| surface ...... water ................................... . i
quality. When ..... indicator parameters exceed thresholds, increased monitoring could be required for
other parameters (including metals and toxicity) to determine the extent of ARD releases/impacts
(British Columb^AME) ...... TasJcFprcej .......... 1990). '
4.1.4 MITIGATION OF ARD
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EIA Guidelines for Mining • Environmental Issues
completely avoiding mining in areas with the potential to form ARD may be difficult due to the
widespread distribution-of sulfide minerals. The individual applicant's pre-project testing (using the
methods described hi the previous section) should be representative of each rock type, provide good
spatial coverage, and be proportional to waste quantities. As discussed above, this may frequently
require collection and analysis of an extensive number of samples. The results of truly representative
sampling should allow the applicant to develop a mine plan to avoid, wherever possible, sulfide-
bearing/acid-generating rock.' . -
Effective isolation of wastes (backfill, waste rock, or tailings) with the potential to develop ARD is a
key element to conducting mining activities while minimizing perpetual effects to surface water and
groundwater. In isolating these wastes, the acid generation process is brought under control. The
requirements for the formation of ARD, as discussed in previous sections, include the presence of
sulfides, oxygen, and water. Control of materials with a potential for acid generation can therefore
be implemented by preventing oxygen from contacting the material (or minimizing oxygen contact),
preventing water from contacting the material, and/or ensuring that an adequate amount of natural or
introduced material is available to neutralize any acid produced.
The following sections generally describe specific types of mitigation measures for ARD control. For
the most pan, only limited 'data are currently available to document then; effectiveness. Further,
individual site conditions significantly impact their feasibility and performance in the field. In many
cases, the measures discussed below .are most effective when used hi combination and adapted to the
situation existing at a specific site.
4.1.4.1 Subaqueous Disposal
Where fluctuations in water levels are not expected, placement of acid forming materials below the
final potentiometric surface may be an effective means to exclude oxygen. Similarly, some dry waste
management units can be closed by flooding/subaqueous disposal of potentially acid generating
material. The water must be of a sufficient depth to ensure that it is not well oxygenated (since
sulfide can oxidize in subaqueous environments) and it should not pass rapidly through the system.
Wetting conditions must be permanent and physical mechanisms must not be present to allow
entrainment of wastes in the water. Further, it should be noted mat metals found in waste materials
can dissolve into neutral waters. Both Lapakko (1994b) and St.-Amaud (1994) have suggested
placing protective layers over acid generating tailings disposed of hi a subaqueous manner. Similarly,
mine operations hi upland conditions and hi drier portions of the west may not be able to consider
submersion as an effective mitigation tool for acid formation. (See also Section 3.2 above.)
4-23 September 1994
-------
I U Ill
iiiiiiil'iniii1 IP* nil inini
ill III ill I" II f ill Ihil11 'III 1111 II Illllilllllllll^ !! I ! ml '»ilil »i|i|ii|l»»ll'lllp »»l'
i II in mil i mill ii inn n nil p inn iiiiiiiiiiiiiiiiiiiiiiiii inn i null iiiiilllliillll liniillllllll i|iilii|l|lllll|i|l|i|lj|i|ii|ll|i|l|i||ii|lill II1111 nil II lill|ii||i|llillllllll|ii|l|i|l II 11! n p in I nil i in mil! lilll|llllllillllllllilllll|i|lll
|
4.1.4.2 Covers
Issues EIA Guidelines for Mining
±g»S £°52iSa Si !2 SSLBSE (and oxygen) from acid forming materials is the use
°f MOW permeability cover. Covers may consist of compacted soils or synthetic materials. Proper
ESS68 to* meir integrity remain intact; those subject to erosion, weathering,
SS2i! or Penetration by plant roots may not provide adequate protection for an indefinite
period of time. Most (if not all) cover materials are more effective, at controlling infiltration of water
than excluding oxygen. By reducing the amount of water infiltrating a covered system, the potential
for migration of any acid drainage formed beneath the coyer also is reduced. Similar to covers,
can be installed near §e highwaU to isolate disturbed areas from
!: *2S^y> during actual waste disposal, mines can segregate materials to minimize acid
generation potential. For example, carbonate materials can be placed on the surface of piles, while
potentially acid generating materials are placed below the surface.
" ( ' '''.:• • ' i ' ' ' ' ' '• ' ^ ' •
_ L - ' .. , • .. • , -. ,v,i • ... i •-. • :
The Invitations imposed by covers are availability and costs of cover materials. If only limited
"SSlSfSS 2£fi&SBfl3$g4$ SHSWRfl over the life of an operation, those wastes which require special
™^ be precisely identified in the field. In coal mining operations, the complexity of the
situation is compounded by the requirement that reclamation be contemporaneous. In these cases, a
special waste disposal area is generally not permitted for extended periods of time.
i " ! 'i
4.1.43 Waste Blending
:::, ... ..'''iii *? „ , ' , h * , , ,
Blending activities during the mining operation may be used to mix alkaline materials with acid
fonnmS mattrials 'Witoi* a* T^te disposal unit. The effectiveness of blending wastes is directly
****? *° ** ^reallieri°g Properties of the alkaline materials; if a CaCO3 equivalent is available at a
rate equal to or exceeding the oxidation of sulfides, acid formation could be adequately controlled.
Ill AlL^«feI»V«^ M
-------
EIA Guidelines for Mining " . Environmental Issues
disposal facilities. French drains may also be installed to promote ground and surface water flow
underneath a disposal unit. However, french drains constructed under disposal units (waste rock
dumps, head of hollow fills) that eventually generate acid can function as a conduit for acid rock
drainage into surface waters.
At some metal mines, acid-forming waste rock is being "encapsulated" within larger waste rock
dumps. Relatively low-permeability neutralizing material (often waste rock from other lithologic units
that is compacted) is placed under and/or over sulfide rock. The intent is both to reduce water flow
to and through the sulfide rock and to neutralize any acid that may form.
4.1.4.5 Bacteria Control .
Thiobadllus ferrooxidans is the principal organism responsible for the bacterial oxidation of sulfides
that may dramatically (up to a fivefold) increase the rate of acid formation. Studies using bactericides
to control ARD have been conducted with some degree of success. A summary of the effectiveness
of bactericides presented by the British Columbia Acid Mine Drainage Task Force indicates that these
compounds can effectively reduce acidity by 50 to 90 percent (British Columbia AMD Task Force,
1989). However, bactericides are degraded and leached with time, ultimately having a limited life
span. Additionally, if acid generation is occurring hi an absence of bacteria, bactericides will only
control the rate and not the presence of ARD.
.4.1.4.6 Treatment
- Mines currently hi operation experiencing acid mine drainage may face a*costly and long-term battle.
If acid drainage develops (as it often has) unexpectedly, well after waste disposal units have been
constructed, mitigation may require extensive earth moving activity, if sources are small enough to be
pinpointed. Alkaline material (e.g., lime) may be added in solid form to flows moving into or out of
the acid-forming area (the use of "sorbent" polymers and microorganisms is also being studied). The
effectiveness of raising the pH of the water before or after contact with acid-forming material is
limited by the chemistry of the constituents involved, and the volume of acid being produced.
Demonstration projects'have made use of injecting alkaline solutions into acid producing material;
however, the long-term effectiveness of this treatment has not been documented (Bureau of Mines,
1985).
Anoxic limestone drains (ALDs) are currently being studied as passive treatment technologies. The
Tennessee Valley Authority has successfully used ALDs to enhance the performance of constructed
wetlands (Brodie, 1991). Combined ALD and wetland treatment systems have also been successfully
tested in Pennsylvania (Hedin and Watzlaf, 1993; Rowley et al., 1994). However, limited data are
currently available to assess the long-term effectiveness (including potential limiting factors, such as
coating of limestone surfaces with iron and aluminum oxides) and widespread applicability of ALDs
4-25 September 1994
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Environmental Issues
EIA Guidelines for Mining
in mitigating ARD, especially where they are used alone. In addition, design of ALDs or any other
II ,11 , i i i i ii . I,
alkaline/precipitation treatment system must include a settling area. Hedin and Watzlaf (1993)
provide additional information on the design and performance of ALDs.
In cases where mine drainage is only slightly acidic and metal loadings are low to moderate, natural
and constructed wetlands show some ability to improve water quality (Brooks et al., 1990). In
wetlands, "treatment" of ARD (and associated metals) occurs through physical (settling and
I ' ' ',f , ' " : " ;. ,, • ' f .:: "\,r .,., . ,,
adsorption), chemical (hydrolysis and oxidation), and biological (bacterial desulfurization) processes.
Cohen and Staub (1992) provides technical guidance on the design and operation of wetlands
systems. Based on data from an operating wetlands treatment system at the Big Five
Tunnel in Idaho Springs, Colorado, an effective life of approximately 4-6 years is projected for a
PHI i 1 _ i i liil II H ,. * < II < < « i PL < ll N I i II
single loading of substrate material (Cohen aid Staub, 1992). At some sites, operators may need to
provide separate areas for anaerobic (chemical/physical) and aerobic (biological) processes. Based on
a study of six artificial wetlands constructed by the Commonwealth of Pennsylvania, a surface flow
| ' _ ; ; ;i ; i i ; , i ,; , " | , ;
criteria of 6 grams/day/square per meter was recommended (Dietz et al., 1994).
iiiiiiiiii
Testing conducted by the Commonwealth of Pennsylvania has'shown that passive wetlands treatment
can be effective in mitigating ARD for coal mines, especially for mildly acidic drainage (performance
of more than 73 wetlands was evaluated). However, it should be noted that study results generally
showed mat treatment levels for metals were lower than predicted (Hellier et al., 1994). Further,
studies such as those performed by the State of Minnesota, have shown that the capacity of wetlands
for metals removal is often limited. The Minnesota study found that metals removal was limited to
me upper 20 centimeters of a constructed wetland and that limited-flows/periodic maintenance would
^m Jill nllil iliii i (ii liil f
be necessary to provide long-term mitigation (Eger et al., 1994).
While combined ALD and wetland systems show some promise for passive treatment of highly acidic
streams (Rowley et al., 1994), current data to support then* widespread effectiveness and feasibility
||H are limited. Therefore, where flows contain low pH values and nigh'metals concentrations, 'active
II11 111 11 111 111 l|llllllll • 111^^ IIIM llllllllllllll llllllH llllllllllll 111111 111 111 111 11111 llllllllllll III I |
long-term treatment may be necessary to achieve acceptable water quality in the mine's discharge. A
potential alternative to conventional active treatment practices (neutralization/precipitation with lime,
etc.) involves the use of Sulfate'Reducing Bacteria (SRB) to treat acid drainage. SRB decompose
organic compounds and produce sulfide (which is either given off as hydrogen sulfide gas or reacts
, metals to form metal sulfides). At a February 1994 EPA workshop on SRB treatment, several
icipants noted success in reducing metals levels. However, SRB performance data are still limited
fndjigsults. ....... vary
...... optimum design parameters,'
Igpacts, ....... tpwcfty to ..... organisms, and hydrogen sulfide conttpl need' to be address (U.S. EPA, 1994).
inally, Cohen and Staub note research indicating SRB are found in wetlands and are important for
removal in wetlands treatment systems (Cohen and Staub, 1992).
^^^^^^^^^
IlilllH^
llltK^^^ ill' Kill IlllR^^^ ••Ill
-------
EIA Guidelines for Mining Environmental Issues
4.1.5 SUMMARY OF FACTORS TO BE CONSIDERED IN EVALUATING POTENTIAL ARD
GENERATION/RELEASE
ARD from coal and hardrock mining operations has been shown to have significantly affected aquatic
life in thousand of miles of stream segments throughout the country. These effects can be long-term
and the costs of remediation are prohibitive where it is even feasible. - While there is extensive
ongoing research on ARD, there is substantial uncertainty associated with virtually every methodology
used to predict, detect, and mitigate ARD, Further, the extent of ARD generation and the potential
risks are generally dependent on a wide range of site-specific factors. No assessment of potential
environmental impacts of a proposed mine should dismiss acid generation potential based on limited
test data, especially where sulfide ore will be mined. In addition, care must be taken not to be
overconfident hi the efficacy of specific mitigation measures that may be used if ARD is encountered.
ARD-related factors to be considered in evaluating potential impacts include:
• Comprehensive baseline acid generation potential testing of the ore and waste materials.
Where there is any historic basis for believing that ARD could occur and/or where new
sources are proposed in particularly sensitive environment areas, the applicant should
conduct testing of each geological unit as well as analysis of representative waste samples.
Further, the applicant must be cognizant^of the areas/ranges of uncertainty associated with
static testing. Where there is evidence ARD can occur or where static test methods indicate
uncertainty, kinetic testing should be performed to determine the drainage characteristics
(and facilitate mine planning).
• An ongoing environmental monitoring program to detect ARD when it occurs. Sampling of
wastes, discharges, and surface water/groundwater should be tailored to site-specific
conditions mat favor ARD generation (e.g., monitoring during or immediately after a major
precipitation event after a long-term dry period). An effective monitoring program should
emphasize the need for a full understanding of site conditions, including hydrology,
geology, and climate. Typical one-time quarterly or bi-annual sampling events may not be
adequate to detect ARD.
• Where ARD could be encountered, detailed information on the design and operation of
proposed mitigation measures (including a quantitative engineering assessment of then- likely
effectiveness based on then* historic use under similar conditions). If any uncertainties
arise, operators should provide for contingencies if proposed measures are ineffective.
• An approach to reclamation bonding that accounts for the long-term impacts of ARD must
be cognizant of the potential for a significant lag-time/delay in ARD observance (thus
necessitating care in bond release). Also, the need for perpetual treatment measures (and/or
perpetual maintenance of passive treatment techniques) should be considered.
While the potential for ARD generation is highly variable, extensive documentation is available on a
wide range of site conditions. Further information is available from the references cited in this
section and from many other sources. In addition, Canada's Laurentian University Library has
4_27 September 1994
-------
...... [[[ , ...... : [[[ - [[[ EIA Guidelines for Mining
Ji ...... : .......... ,""!™~, '! ...... „"'"" ' ..... '^';l', ,!'':v»^, '"' " , ,'. ,' , ........... '
:. • , • -• , : • • . .' , ............... i ....... •v:;" "'V ,
, Hshed the on-line Mining Database, which contains citations and abstracts, related to ARD and
reclamation. Finally, while there is no consistent National policy related to ARD, several regulatory
entities have developed specific requirements to address ARD generation at new mining operations.
For example, BLM has recently promulgated an ARD policy to guide approval of proposed
operations (Williams, 1994). OSM requires acid-base accounting to assess acid generation potential.
f^» , j- t ' t_ T\ » • ' '
•iSSSZl 2£ Brmsj^olumbja government ^ has sgecific requirements for .ARD prediction,
ggjirgmnenfel mOTutgrJng, mitigation, and bonding (Price and Errington, 1994). Some States and
Forests also hay^poticies rejatecHo jxrediction,monitoring, mitigation, and bonding. .
S"5?y , AD HEAP ICHING
For decades, it hasjbeen used asa pyrite
in base metal flotation. ftalso has teeji used fgj over, a cejggry in gold extraction. In the
I9S)s, technologies that allowed laree-scale beneficiatinn of gold ores, using cyanide (first
iSsnojogtrlgg, a gripple creek, Colorado) set the' stage for the enormous increase in cyanide usage
jold prices skyrocketed in the late 1970s and 1980s. Continued improvements hi cyanidation
F" "r nj"' W" " "iiisr11'1* rs ^ 3 ™i : ~ : : ; ,:;: ,: :T":: T,"1:":1"1 ,::: ::;, ,'",""" r, !:;; ,:"" ::~T~:,ii :: ~ i""::"n ~*,,,, , /
"technology have allowed increasingly lower-grade gold ores to be mined economically. Together with
^.continued ¥& gold prices, this has resulted in increasing amounts of cyanide being used in mining.
A substantial pro^jtion of sodium cyanide produced in the U.S. is now used by the mining industry,
* ™ ..... leaching ...... Ojperations ....... (both ...... tank ..... and ...... heap leaching). in
....... ..... ...... ....... ...... ..... ......
fOT ..... copper/molybdenum flotation, and much less than 5 million
' ' . ' ................ '"• ........................ ...... '
' ' ililiii
'~-~;foe_ 2ff !°5f!^ 2£,5Siiii! = 1 IS!?! ?!lliE JSESlSSs IS5 ISSSSi SiSSlm on gig use, of,; :,
! ^n the Tninmg mdustry. When exposure occurs (e.g., via inhalation or ingestion), cyanide
lal in a short period of time.
operalions a^j cyanide usage proliferated, there were a number of
i|||disiiw.hej| ..... gjey attempted to use tailings ponds or other cyanide-
containing solution ponds (e.jg., pregnant or barren ponds). For example, operators in Nevada,
g^Ugj^g^ ^ /s^Mi^Kp^^ ^Q regulatory authorities on over 9,000 wildlife deaths, mostly
waterfowl, that had occurred on Federal lands in those States from 1984 through 1989 (GAO, 1991).
' &* addition, a number of major spakfaaye occurred, including one hi South Carolina in 1990, when a
dam ^^ resulted in the release of over 10 mflUon gaUons of cyanide solution, causing fish kills for
nearly 50 miles downstream of the operation.
[[[ " ................................... i ......................................... i [[[ ,
to many cases, regulatory authorities— Federal land managers and States— have responded by
developing increasingly stringent regulations or, hi many or most cases, nonmandatory guidelines.
These * ...... £25 ..... Mifegss, ...... $£,;desjgn of facUities that use cyanide (e.g.,
, ...... . ..... ...... ..... , ...... , ..,
reqiiirin^recmnmending liners and site preparation for heap leach piles or tailings impoundments),
III II 111 lllllllllllllllH I ' • I ..... llliillf IlllilH lllllilill ill1 '(I llllill I'll Illli ilPllllliill ........ Ill ll I ............. lull i III 1 ....... 1 ....... lllllll ...... Ill ..... Ill I ........ Ill ...... llllllllllll ........ lllllllllllllllllH ...... I liillllll ................ Ill ......... I'll .......... Ill .............................. I ....... I ..... II ............... I ...... I
4-28 September 1994
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EIA Guidelines for Mining , Environmental Issues
operational concerns (e.g., monitoring of solutions in processes and in ponds, and in some cases
treatr-ent requirements for cyanide-containing wastes), and closure/reclamation requirements (e.g.,
rinsiiu to a set cyanide concentration in rinsate before reclamation can begin).
There are a number of major issues associated with evaluating the potential impacts of cyanide
operations on the environment. These include the complexity of cyanide's chemistry, uncertainties
about its behavior in the environment, and inadequate laboratory analytical methods. These issues are
discussed briefly .below. . '
4.2.1 UNCERTAINTIES IN CYANIDE BEHAVIOR IN THE ENVIRONMENT
4.2.1.1 Cyanide in the Environment
•
Cyanide concentrations are generally measured as one of three forms: free, weak acid dissociable
(WAD), and total. Free cyanide refers to the cyanide that is present in solution as CN' or HCN, and
includes cyanide-bonded sodium, potassium, calcium or magnesium. Free cyanide is very difficult to
measure and its results are often unreliable, difficult to duplicate, or inaccurate. WAD cyanide is the
fraction of cyanide that will volatilize to HCN in a weak acid solution at a pH of 4.5. WAD cyanide
includes free cyanide, simple cyanide, and weak cyanide complexes of zinc, earimhm^ silver, copper,
and nickel. Total cyanide measures all of the cyanide present in any form, including iron, cobalt, and
gold complexes. Exhibit 4-3 shows one means of classifying various forms of cyanide. Free cyanide
would include the"readily soluble" simple compounds, and WAD cyanide would generally include all .
of the forms in the exhibit except the "strongly complexed cyanides. "-
Aqueous cyanide (CN~) has a negative valence and reacts readily to form more stable compounds.
Aqueous cyanide complexes readily with metals in the ore, ranging from readily soluble complexes
such as sodium and calcium cyanide through the complexes measured by WAD analytical methods to
strong complexes such as iron-cyanide. At a pH below about 9 s.u~, weaker cyanide compounds can
dissociate and form hydrogen cyanide (HCN), a volatile gas that rapidly evaporates at atmospheric
pressure. The stronger complexes are generally very stable in natural aqueous conditions.
Unsaturated soils provide significant attenuation capacity for cyanide. Within a short time and
distance, for example, free cyanide can volatilize to HCN if solutions are buffered by the soil to a pH
below about 8 s.u. Adsorption, precipitation, oxidation to cyanate, and biodegradation can also
attenuate free (and dissociated complexed) cyanide in soils under appropriate conditions. WAD
cyanide behavior is similar to that of free, although WAD cyanide also can react with other metals in
soils to form insoluble salts. (Hutchison and Ellison, 1991)
Free cyanide is extremely toxic to most organisms, and this form has been most frequently regulated.
Under the Safe Drinking Water Act, EPA has established a maximum contaminant level (MCL) of
4-29 September 1994
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Environmental Issues
EIA Guidelines for Mining
1 III
t "
!•
t
t
Exhibit 4-3. Stability of Cyanide and Cyanide Compounds in Cyanidation Solutions
' '* , • *
Classification -•
Free cyanide
Simple compounds
a. Readily soluble
b. Neutral insoluble
• salts
Weak complexes
Moderately strong
complexes
Strong complexes
S^y^SV Compounds^' •'"••'•*•• '•"
CN-.HCN
a. NaCn, KCN, Ca(CN). Hg(CN)j
b. Zn(CN),, Cd(CN)j. CuCN,
Ni{CN)2,AgCN
Zn(CN)/2, Cd(CNV', Cd(CN)^
Cu(CNV'. CuCCNV2, Ni(CN)4-2,
AgCCNV1,
FtfCNk-4, OKCN)^, Au^NV,
Fe(CNV3,
•V •.•.'•. "•''••$:' Solution chemistry
Extremely toxic. In natural waters below
pH about 83, HCN form is predominant.
Water soluble. Dissociate or ionize readily
and completely, to yield free cyanide and
metal ion.
Rates of dissociation and release of free
cyanide affected by light, water
temperature, pH, total dissolved, solids, and
complex concentration. pH and
concentration most affect stability and
extent of dissociation (breakdown increases
wim decreases in pH, concentration).
Iron is most common/ important- Very
stable in absence of light. Long-term
stability uncertain.
Source: Column 3. Mudder and Smith 1989; columns 1 and 2 cited in Mudder and Smith.
0.2 mg/1 free cyanide in drinking water. The Clean Water Act ambient water quality criterion
f'iS," ' • "I',,, ,11 , • , ,,, "I ."1; I ^ III |* , ,. .'
recommended for protection of freshwater aquatic life from chronic effects is 0.0052 mg/1 free
i
...... criteripn is 0.022 rgg/1 free _cyanide. Mpre_Tecently_ developed mining-related'
and guidelines often specify weak acid dissociable (WAD) cyanide, largely because of the
difiBculty in measuring free cyanide at the low concentrations of regulatory concern (Mudder and
, 1992). Longer-term environmental concerns with cyanide, those not related to acute hazards
from spills, revolve around the dissociation into toxic free cyanide of coinplexed cyanides in waste
units and in the environment.
Analytical Issues
In developing the effluent limitation guidelines for the Ore Mining and Dressing Point Source
Catejorj (at 40 CFR 5311,440), EPA established, a techno|pgy-based standard for all discharges from
mills that use, Se,,"cyanldation" process to recover gold and sUver, and mills that use cyanide hi froth
•iflotation of copper, lead, zinc, and molybdenum ores. In this process, the Agency considered several'
levels hi mill wastewaters. However, EPA found that the
in both treated and unfreatedjn||l w^tewaters were below the 0.4 mg/1 quantification
• limit for EPA-ajgroyed test methods g.e., treatment performance could not be ievaluated^. Because
E and becauig complete recycling of mill waters was practiced at many facilities, the Agency
" a zero discharge requirement. EPA was aware of specific sites where laboratory methods
4-30
September 1994
! , " ' '
" ' |'"u'"!" ''"" '"""!"|! '" '"! 1""1"1 ''' ''' ""'' ' I1"""! ! ""''' J! ""'' »»i«'f |h
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EIA Guidelines for Mining Environmental Issues
were effectively being used to quantify cyanide removal and suggested that these methods could be
used by permit writers to establish cyanide limits in individual NPDES permits on a site-by-site basis.
Analytical methods used to determine .cyanide concentrations in tailings and tailings solutions,
effluents, and heap pore water are still being debated. At low concentrations, testing is inaccurate
and measurements of cyanide may not be good predictors of actual cyanide concentrations in the field.
(Durkin, 1990; Colorado, 1992a; U.S. EPA ORD, 1993) Many complex and cumbersome analytical
methods have been developed as a result of the need for measuring cyanide in a variety of matrices.
Many "random" modifications of procedures also have made it very difficult to.interpret many
analytical results (California Regional Water Quality Control Board, 1987).
EPA's Office of Research and Development (ORD) is currently evaluating cyanide test procedures
and methods, and is investigating a proprietary, privately developed, distillation method that appears
to be successful for cyanide analysis. One of ORD's activities includes revising the current methods
.for measuring and detecting cyanide fractions and eliminating interferrents. ORD is also reviewing
performance data and problems of 17 currently used methods. Future efforts will involve continued
evaluation of cyanide species (ORD, 1993).
Because, of the uncertainty involving cyanide forms and analytical methods, regulatory standards and
guidelines may not be clear on the form of cyanide being addressed. Nor, in many cases, do
environmental monitoring data make clear which form or which analytical method has been used.
This can make it difficult or impossible to evaluate the short- or long-term potential environmental
impacts of a proposed (or an existing) operation. Thus, it is important that environmental
documentation be clear as to the form of cyanide that is described and addressed, and that appropriate
analytical methods be specified. Similarly, the types of cyanide complexes that are expected to occur
in heap leach piles and tailings should be assessed, along with the rate and extent to which the
complexes may break down to toxic forms upon their release (even in low concentrations) to
receiving waters. .
4.2.2 POTENTIAL IMPACTS AND APPROACHES TO MITIGATION DURING ACTIVE LIFE
In general, cyanide can cause three major types of potential environmental impacts: first, cyanide-
containing ponds and ditches can present an acute hazard to wildlife and birds. Less frequently
(because of lower cyanide concentrations), tailings ponds present similar hazards. Second, spills can
result in cyanide reaching surface water or groundwater and cause short-term (e.g., fish kills) or long-
term (e.g., contamination of drinking water) impacts. Finally, cyanide in active heaps and ponds and
hi mining wastes—primarily heaps and dumps of spent ore and tailings impoundments—may be
released and present hazards to surface water or groundwater, and there may be geochemical changes
that affect the mobility of heavy metals. These impacts and the major issues and uncertainties
associated with each are described briefly below.
4.31 September 1994
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:::: j i »,
ICnviroitmental Issues
EIA Guidelines for Mining
4.2.2.1 Acute Hazards
I •
The heightened awareness of the threat to wildlife and birds presented by cyamde-containing ponds
and, wastes have led regulatory authorities (generally, Federal land managers and States) to require
operators to take steps either to reduce/eliminate access to cyanide solutions or to reduce cyanide
"~~— «)iik?5iEtt!oijsin[ exposed JSterials to Eelow lethal tevelsT jj^jj^y" ^g^— ^ —;-—-— —
I!.!!!!!!!!!!!!!!!!!"!!!!!!,,!!'!!!!!!!"!!!! I """"""! : llSiilii i',!'1'! ."i , ''!. . 'i" • ,,•••!' , • •" i • i"! ," , • '•„"••" ' "» I, ' '!' " ' ,„ ,
' I™"!!""' ........ ! .......................... ;""""!"" [[[ ' ...... jjyij! ............ yi'! ..... i •' i , i i i,1 ...... ' ', • • ip , ' •' ' i ' |!'' ," , ' ''„"'•" ' ''" i ' 'i1 " ' i
to the allowable concentration of cyanide in exposed process solutions are widely variable (when
!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!Z!!!!!!!!!!!!!!!!^ ...... i,,,;:;;;;;;;,;;;;;;;;;;;;;;;;;";;;;;;;;;;;;;;;;;;;;;;;;;,;;;;; ...... ;;;;;;;;;;;;;;;;;i;i;;;;;;;;:;!i;;;;;;;;;;;;;;;;;:;;
...... ,,,,, ...... ,
mm eric ..... limitations ........ are ..... established, they generally range around 50 mg/1), as are the means by which
— comply. '(Operators reduce access in several ways, including covering solution ponds with
, netting or covers, using cannons and other hazing devices (e.g., decoy owls) to scare off waterfowl
and other wildlife, and/or 'ingtaffiig fencing to preclude access by large wildlife. At least one mine
uses tanks to contain all solutions. In addition, operators may be required or may elect to treat
tangs sures to reduce cyane concentratons, they may maintain higher fluid levels hi
nupoundmems so as to dilute concentrations, or they may reduce the amount of 'free liquids in
impoundments to rmnimize pond surface area. Some facilities also provide "micro-nets" over ditches
to keep out rodents and smaller wildlife not excluded by large fences. In-evaluating the threat that
cyanide usage at a proposed facility may pose to wildlife and birds, and the effectiveness of control
and mitigation measures, environmental documentation should describe the standards that must be
f : . ' " i' "':/ • ' "I - • " - | .
met, the types of organisms of most concern (e.g., waterfowl at an operation in a migratory fiyway or
near nesting or staging areas), and the specific measures that will be used to reduce exposures and
,. nwrtgity. The grogram-by' which the measures will be evaluated for effectiveness should also be
described; it will generally involve monitoring aid reporting deaths and supplementing existing
methods as necessary.
, 4.2.
Spills and Overflows
. !B^^^^
Most actual environmental nnpacts resulting from cyanide releases have been-associated" with spills
.'-- -==== = =
^l^jj^jn^jjor failures ^^^^^^^aEu^^^^^ dam~f^u»j"i^^"irfb^p slopes)^ ]MinoFs|)ills
p| cyanide are not uncommon at gold facilities. These occur typically when portions of a heap leach
pile slumps into a drainage ditch or solution pond and cause an overflow of cyanide-containing
solution or when a pipe carrying pregnant or barren solution, or tailings slurry, fails or is
" by mining equipment or vehicles, In all but a few major cases, cyanide spills have
2? ...... §2J!5 ...... 2!°^M? ,5!S5pc?? jattenuatjkin Jn most cases. Facilities routinely
store hypochlorite or other oxidants for use in detoxifying such spills. In addition, some operators
^^^ ...... 1^ jflitaice ...... or placed barriers between pipelines and equipment routes. Others have
reinforced pipelines in high-risk areas.
,2£s,*E?!l!Y£ ^SYF01?!6?!?,—:Serl5r?py including any water bodies—may be the most
potential impacts of spills. In all cases, environmental
' »', , „ '! , ,,, , , ',!, ' ,„,:!' ,' , i , •
the ractices or methods that will be used to reduce the risk of
4-32
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EIA Guidelines for Mining ^ Environmental Issues
ruptures and spills, and in responding to minor and major releases. More details would be necessary
for operations in sensitive environments, including details on spill-prevention practices and on spill '
response procedures. Particularly when cyanide facilities and structures (e.g., pipelines, heaps,
impoundments) are near streams or wetlands, extra precautions are appropriate, including double-
walled pipelines, additional setbacks of heaped ore or intervening barriers between heaps and solution
ponds, automatic pump shutoffs in the event of pressure loss, etc.
During facility operations, great attention is paid to the water balance and the efficient movement of
solution through the system. Facilities are generally required to be able to contain at least the normal
24-hour process solution flow and the maximum volume from the lO-year/24-hour precipitation event.
Many States require additional capacity, sufficient to contain the flows from the lOO-year/24-hour
event. Because of-the size of mining operations and the large areas that can contribute flows, this can
be an enormous volume, well beyond feasibility for many operations. Thus, most States allow an
operation's required storage capacity to include the volume of precipitation and solution that can be
held in heaps as well as in solution ponds and overflow ponds. As a result, continued circulation of
solution is necessary to ensure that heaps do not dewater and overwhelm the capacity of ponds. Most
States require onsite generators to ensure continued supply of electricity to pumps in the event of
power failures. All details of storage capacity and solution management may not be available at the
time environmental documentation is prepared. However, conceptual plans that identify most
components of storage capacity and the means by which capacity will be ensured usually are.
Because miscalculations involving solution management can be catastrophic (for example, this was a
major problem at the Summitville mine, now proposed for the National Priorities List), reviewing
water balance plans, even conceptual plans, is crucial in assessing potential environmental impacts.
This is particularly true when operations are in or near sensitive environments. Every aspect of water
balance calculations should be assessed: the amount of precipitation and runon/runofj assumed to
occur in the designated storm event, the area of the operation that will contribute flows and the
amount, the amount that can be held hi each component of the water management system (e.g., the
saturation status of a heap under normal operating conditions), even the pumping capacities of
solution recirculation pumps. In addition, some assessment should be made of water balances under
conditions other than the designated storm event. For example, spring snowmelt can .provide flows
over several days that are more significant than long return-interval precipitation events. Similarly, a
series of less significant storms (e.g., several 5- or 10-year events) can collectively be more
significant than one extremely large storm. Meteorological data are often provided hi environmental
documentation (or hi proposed operating plans submitted to States and/or Federal land managers), and
these should be evaluated carefully to determine whether reasonable assumptions have been made
regarding hypothetical worst-case events. Also of importance is how both operators and regulators
may respond to unexpected water balance problems. In most cases, such problems are addressed as
they arise, with never a reconsideration of the entire system and whether the original planning and
4-33 September 1994
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thus no re-evaluation of potential environmental impacts. It may be
appropriate in some cases to require more formal contingency planning at the outset, with a
reassessmenl of potential envu-onmental impacts required when critical components of the "water
4.2.2.3 Liner and Containment Leakage
^ ,.
j, ii ,. ; ; ; - ; .•; ••' . [ _' , '
As described in Chapter 3, heap leach operations use liner systems of various sorts under heaps and
solution poods. Ih'general, liner systems consist of a prepared foundation (compacted subsurface,
with large rocks and objects removed), a bedding layer (if used), synthetic or clay liner, seepage
collection/detection layer (if used), and a cover layer of material to protect the liner. Perhaps the
single most important factor in preserving the integrity of liner systems is their proper installation,
including comprehensive construction QA/QC. The type of liner system that is used generally is
based on site conditions, operator preference, and regulatory requirements (Van Zyl, 1991). Liners
are usually of polyvinyl chloride (PVC) or high density polyethylene (HDPE); recently, very low
density polyethylene (VLDPE) liners have emerged. Although there now is ultraviolet-resistant PVC,
there have been some problems with older PVC liners degrading when pond or ditch liners are
exposed to ultraviolet light. In most cases where there have been significant liner failures, they have
been due to improper installation or accidents combined with inadequate construction QA/QC.
There, is a clear economic incentive to Tnimmfae pregnant solution loss during operations; this is often
cited as a reason why operators' design plans should be accepted as proposed. In practice, operators
assess the optimum balance of economic and environmental considerations in design planning. Thus,
the, costs of actual containment technologies and'practices are balanced with th* economic losses
associated with a certain amount of solution loss as w«n as regulatory and esyirocmental
considerations. As noted in Chapter 3, regulatory authorities (Federal land managers and States) are
increasingly requiring solution .ponds to be doobie-iioed, often with a composite liner system that
1 includes' leak detection/collection. Requirements far heaps more often specify" single liners, which
_ may be synthetic or clay. In southern' California, for example, the 'great depth to groundwater and
the artramafinn capacity of soils ted the Regional Watec Quaiiy Control Board to specify single liners
fbrbeapc.
j • ' . "•': '"'• , ' • • • '••;•.[••
In many locations, however, heaps are located entirely or partially in drainagewayc (generally
ephemeral) over shallow alluvial or shallow bedrock aquifers. This is usually the.case for tailings
" impoundments, but"these are infrequently lined; seepage through and under dams is generally
collected in toe ponds* but some seepage may bypass such ponds. Should leaks occur through heap
liners or should seepage bypass collection ponds, cyanide can reach the alluvium and/or shallow
groundwater. This can then affect downgradient surface waters or springs or can reach -bedrock
ILii iii!iiiiiiiiiiiiiiiiiiiiiiiii,iii!iiaiim i i II I i I M P i i
aquifers. Whether subsurface materials can attenuate any such leaks and reduce cyanide levels
depends on the nature of the materials and the location and extent of water present in the subsurface.
t I j i i i i I [i i ij j ii 11 ...i i • |i 111 i • in i
4.34 September 1994
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EIA Guidelines for Mining . Environmental Issues
Evaluating the likelihood and the potential consequences of cyanide leaks is particularly dependent on
detailed information on the subsurface and on proposed liner systems, and on construction QA/QC.
Subsurface information of concern includes the nature and characteristics of the material (depth,
mineral composition, compressibility, shear strength, seasonal saturation levels, presence of springs,
etc.) Liner systems should be fully described, along with a clear justification for then- selection (e.g.,
why PVC over VLDPE, why flexibility was or was not important, why and how their resistance to
sunlight/punctures was considered, etc.). Detailed design and QA information is often not provided
in great detail, but in some cases may be necessary. Information on the minimum standards that are
• imposed by applicable regulatory authorities can assist in determining if more detailed information is
needed—if standards are very general, then more information may be appropriate, for example.
Should a proposed operation be located in an environment where leakage could be especially
damaging, specific information on the subsurface, on site preparation, and on the liner system and
installation and construction QA/QC are always necessary for an evaluation of potential impacts.
Finally, the presence or absence of comprehensive monitoring programs (for example, monitoring of
seepage detection/collection systems, if any; of bedrock and alluvial groundwater, of materials and
pore water in heaps or impoundments themselves; of solution and slurries; of dam/heap stability; of
the integrity of containment devices, etc.) and commitments to 'respond to unexpected events can be a
significant determinant in the level of information needed. A sustained monitoring program,
combined with financial commitments and/or regulatory guarantees that environmentally appropriate
responses will be taken if necessary, can provide significant assurances that long-term impacts will be
minimized, even in the absence of detailed information and analyses.
4.2.3 CLOSURE/RECLAMATION AND LONG-TERM IMPACTS
4.23.1 Closure and Reclamation
Until the recent past, reclamation (if required) commenced immediately upon cessation of operations.
With increasing concern over environmental .quality in general and toxic pollutants specifically hi
recent decades, however, the concept of pre-reclamation closure has received more attention by States
and Federal land managers. However, relatively few cyanide operations have been completely
reclaimed to date, since large-scale cyanidation operations are a phenomenon of recent vintage.
Consequently, closure and reclamation measures are not yet well established.
Closure entails those activities conducted after a cyanide unit ceases operating in order to prepare the
site for reclamation. Closure essentially consists of those activities that are required to remove a
hazard or undesirable component, whether it be chemical or physical, to the extent required by States
or Federal land managers. It can entail detoxification/neutralization of wastes, treatment and/or
evaporation of rinse liquids and pond water, dismantling associated equipment and piping, removal or
treatment of waste, reconstruction, grading or stabilizing, and/or chemical testing.
4-35 September 1994
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Environmental Issues
EIA Guidelines for Mining
Reclamation consists of those activities that are undertaken to return the site to a condition, suitable for
the future uses specified by the State or land manager. Reclamation may involve regrading;
backfilling ponds; removal of wastes; site drainage control such as diversions, channels, riprap, and
collection basins; perforating liners to allow drainage through heaps; capping to reduce infiltration
' I . . • , .. ". rk . . • , ft, '. | ' . .
and/or to provide a substrate for revegetation; and revegetation to establish ground cover and protect
against erosion. -
4333 Long-term Environmental Concerns and Issues
The principal concerns with closure of spent ore and tailings impoundments are long-term structural
stability and potential to leach contaminants. Structural stability is dependent on the physical
characteristics of the waste material (e.g., percent slimes vs. sands in impoundments), the physical
11 in iiiiii 1111111
i iiiiiiiiiiiiiiiiiiiii
configuration of the waste unit, and site conditions (e.g., timing and nature of precipitation, upstream/
uphill area that will provide inflows). The potential to leach contaminants is largely dependent on site
tions, including reclamation and mmeral(s) geochemistry
III III III lllllll 1111111111111
111 • I Ill Ill
Cyanide is not the only contaminant mat is present hi tailings effluents or heaps; numerous other
constituents may be present in the waste material and present potential problems following closure and
reclamation. Nitrate (from cyanide degradation) and heavy metal (from trace heavy metal sulfides in
the ore) migration are examples of other significant problems that can be faced at closure of cyanide
operations. As noted above, testing and analysis of cyanide is a major issue because it is difficult to
obtain consistent and reliable test results. Another significant concern is the generation of acid
i iii .11
drainage, typically caused by the presence of iron sulfides that break down to form sulfuric acid.
ill (• lililillilllll IIH^ 1H iiiliill ' i i • ! '
Because of the great variability among cyanide operations, including ore characteristics and climatic
conditions, adequate characterization of wastes and materials is an important consideration for site
closure and reclamation. In part because few have been closed/reclaimed, there is limited information
I I H.J: .. |, ; „ '. ' .• i,'; •' ,
available on the mobility of cyanide and cyanide complexes in closed and/or reclaimed heaps and .
+4*Im«V*1' i I'm >"> Itll • >V7»» 1 ^ l»l n US^*«*AWAW «*+ n •"••-raaanl O ««4l* TXol^^A^. «±A«_ _ • -. *- _ ,_.__ _.fAl__ J_- 1 _.*.?
tailings impoundments. However, at several South Dakota sites, nitrate, one of the degradation
products of cyanide, has been detected in areas beyond the heap . Operators were able .to meet the
0.2 mg/1 cyanide detoxification criteria, but elevated levels of nitrate have prevented the attainment of
other criteria developed by the State for the site. The nitrate levels in surface runoff from the mine .
sites have exceeded treatment criteria and low levels of nitrate have been detected in downgradient
wells. (purMn, 1990)
,
In addition, the chemistry of a spent heap or tailings impoundment may change over time. Although
effluent samples at closure/reclamation may meet State requirements, the effluent characteristics may
°
Modeling can be performed to assess the long-term geochemical conditions at the site taking into
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EIA Guidelines for Mining Environmental Issues
consideration the chemistry of a spent heap over time, and be used to design closure and reclamation
plans. Factors affecting chemical changes in a heap or tailings impoundment include pH, moisture,
mobility, and geochemical stability of the material.
In addition to high cyanide concentrations, the post-leach solution (pre-cyanide treatment) at heap
leach operations is likely to have the following characteristics (Mudder and Smith (1992):
• HighpH(9.5tolls.u.) . .
• Moderate to high dissolved species, mainly sodium, calcium (from added lime), and sulfate.
• Potentially elevated metals of ionic-forming complexes such as arsenic, molybdenum, and
selenium' . .
• Potentially elevated metals which form soluble metallo-cyanide complexes such as iron,
copper, mercury, cadmfr"ft, and zinc. •
Rinsing spent ore for detoxification typically takes from several weeks to several months; however, hi
some cases a site may require several rounds of rinsing in .order to meet State or Federal standards.
One problem that frequently has been encountered is that rinsing/treatment is conducted and effluent
standards may be met, but subsequent rinsing or testing reveals increased cyanide and other
constituent concentrations. (Nevada, 1993b) Spring snowmelt also has.caused effluent concentrations
to rise. Several States, as well as the Bureau of Land Management, now request follow-up effluent
sampling after periods of rest or after rainy season/spring snowmelt prior to approving completion of
detoxification. (BLM, 1992; Idaho, 1993, South Dakota, 1993) Although the reasons for incomplete
or variable rinsing have not been confirmed, Durkin (1990) suggests that non-uniform neutralization
or dilution may be factors. A number of facilities have had to switch treatment methods after a
chosen method failed to reach the desired concentrations. Thus, in practice, rinsing may take many
seasons, or years, to complete.
Agglomerated heaps are more difficult to rinse because aggregating the material prior to leaching
(with lime or cement or other materials) keeps the pH elevated, which in turn makes reduction of pH
and detoxification of cyanide more difficult. One Nevada mine (Trinity), for example, operated an
agglomerated heap; when leaching ended, initial WAD cyanide concentrations were 400 - 500 mg/1
and the facility proposed using natural degradation to reduce the cyanide concentrations but continued
high pH has prevented mis from being effective (Nevada, 1993c). As a result of this and many other
site-specific circumstances that affect detoxification success, State-granted variances from rinsing
criteria are not uncommon in many States.
One mine in Nevada encountered a major problem during rinsing of a spent heap. While .
recirculating the solution during leaching, gold was removed from the pregnant solution but other
4.37 September 1994
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I n1 I i I" i II i ' i ' ', "i I "IN i'M ii
I '. ' . ' I
' '«"> ' Environmental Issues . EIA Guidelines for Mining
metals and constituents continued to accumulate and were not removed from the solution. As a
result, during rinsing, the mercury levels in me rinse water rose to 4.0 mg/1, three orders of
magnitude higher man the primary drinking water standard of 0.002 mg/1. The tremendous amount
of water required for consecutive rinses in order to reach the 0.2 mg/1 cyanide standards has also
1 • been ...... an ..... issue jn ...... Nevada,' (Nevada, 1993b) " •' '
'' i I .
Severa| ...... mines ....... in ...... five ...... w^estern ..... states ...... have. ...... experienced elevated selenium levels (Altringer, 1991). The
Bureau of Mines is investigating the use of biological and chemical reduction of selenium in cyanide
||||||||| ^ UJ illilllta ...... ' [[[ [[[ .................................. J .....................................
tailings pond water. Although high costs may make the treatment prohibitive, the research study was
siicceisfiil ...... in ...... reducing ..... selemum ...... concentrations ...... in ..... tfiejaboratpiy from up to 30 ppm selenium to 0.02
PII111 iipiiiii ppm. , •
Water balance is a major concern at some sites. In arid regions, with limited water resources, the
amount of water that isiiinecessary-to rinse heaps to a required' standard may be" a significant concern.
Conyeisejy, ....... in wet ...... climates ....... tike ...... South ...... Carolina, excess water from heavy precipitation and/or
snowmelt can place a strain on system operations and may make draining or revegetating a heap or
...... ..... - ..... - ......... - ...................... • ........................... • ........ [[[ • .......... - .............. ............................................ [[[
1 , . . . . • ..!•...
Another potential problemjnay be caused by "btijod-offe,^ Jess p_enneable lenses or isolated .areas of a.
heap that affect percolation and low throu^hi the heap, leading to preferential paths for fluid
migration. Available research data'suggest that preferential flow paths and blind-offs increase with
time and volume of liquid. These preferential flow paths can limit the effectiveness of
treatmo^neatralization and may leave pockets of contaminant,* behind in a heap during closure,
which men have the potential to leach out after reclamation.
i M'l1 ( ^ ^ ' • ('' : . • .
Acid generation also^may be a major problem facing many nunes^ At one itime, acid generation at
II^ZJpy^Qide sites was not considered to be a potential problem as many mining facilities used only oxide
ores" (not suffide ores). However, cyanide leaching facilities that mined predominantly oxide ores
have reported cases of acid generation. Even tailings mat were originally alkaline have subsequently
„_ :i j -_;j ~-!t!--~i* Aiii. *- *• *_ ,«.«.''' ' ' " •
\. acia generation. Aitnouen lime mav be added during cyanide leaching, with residuals
°r agglonierated heaps, the time component may eventually wash away through
weathering, leaving sulfide compounds to form acid drainage. (Ritcey, 1989; Catifomia, 1993b) As
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EIA Guidelines for Mining Environmental Issues
many complexities with detoxification and reclamation and which .if any difficulties will be
encountered are seldom known at the time that the potential environmental impacts of a proposed
mining operation are evaluated. As a result, environmental documentation should describe
contingency plans for overcoming possible difficulties and potential impacts under these conditions.
If detoxification is successful, most residual cyanide hi closed heaps and impoundments will be
strongly complexed with iron. Although the stability of such complexes over long periods is not well
understood, cyanide is generally considered to be much less of a long-term problem than acid
generation, metals mobility, and stability (which are discussed elsewhere). Thus, evaluating the
potential post-operational environmental impacts associated with cyanide in heaps, spent ore dumps,
and tailings would involve assessing the means by which operators will ensure that cyanide and its
breakdown products and metallic complexes are contained and reduced to environmentally benign
levels prior to site abandonment. It also may involve an assessment of the ability and authority of
applicable regulatory authorities to guarantee this. Conceptual plans for operators who will detoxify
and reclaim heaps and tailings are generally available at the time environmental impact assessments
are performed, but not the details. This may be sufficient, given that cyanide may not be an
important environmental issue over the long term. What is important is that the plans describe not
only what is anticipated to occur at closure and reclamation (e.g., continued recycling of rinse water
until WAD cyanide levels reach regulatory standards) but also the implications for long-term
environmental performance .that potential difficulties and changes in plans could have.
4.3 STRUCTURAL STABILITY OF TAILINGS IMPOUNDMENTS
The most common method of tailings disposal is placement of tailings slurry in impoundments formed
behind raised embankments. Modem tailings impoundments are engineered structures which serve
the dual functions of permanent disposal of the tailings and conservation of water for use in the mine
and mill. Impoundments are often favored over other tailings disposal methods (e.g., tailings piles,
mine backfilling) because, among other things, they are "economically attractive and relatively easy to
operate" (Environment Canada, 1987). Such economy derives in part from the fact that tailings and
waste rock may account for a major part of the embankment construction materials. Additionally, the
phased nature of embankment construction spreads the capital expense of disposal unit construction
over the life of the project, reducing initial capital outlays. Section 3.2.6.2 discusses the types of
'tailings impoundments .used and then* construction methods.
The disposal of tailings behind earthen dams and embankments raises a number of concerns related to
the stability and environmental performance of the units. In particular, tailings impoundments are
nearly always accompanied by unavoidable and often necessary seepage of mill effluent through or
beneath the dam structure. Such seepage results from the uncontrolled percolation of stored water
downward through foundation materials or through the embankment as well as the controlled release
of water in order to maintain embankment stability. Impoundment seepage raises the prospect of
4.39 September 1994
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I
Eiy
vironmental Issues
EIA Guidelines for Mining
il'STi'iSS B surface water and groundwater contamination and, coupled with the potential for acid rock drainage
(see above), may necessitate long-term water treatment well after the active life of the facility has
11111 passed. Moreover, failure to rngfatain hydrostatic pressure within and behind the embankment below
• critical levels may result in partial or complete failure of the structure, causing releases of tailings and
i ii i
contained mill effluent to surrounding areas.
' i i /
. Therefore, the challenge posed by raised embankment tailings impoundments is achieving a balance
between cost, stability, and environmental performance objectives. Because raised embankments
evolve over the life of the project they present the need and the opportunity to reevaluate design
" parameters Id address changing conditions and project objectives over time. The evolving nature of
raised embankments also means that finished impoundments often differ substantially from their initial
™" """" pitas! ^ccoxdrngfyTit can" Be very" |i§£i5o".deteiS^ in advance the potential for environmental
difficulties or the need for environmental controls:
ii iiiniiniii1
lilI'llllilK
in in in n I in nil i ill in Iii i iln i in in n
4.3.1 SEEPAGE AND STABILITY
lilililllii • (iii nil i i ii i ii|i|ili ii niii
i I i ' "n ii . I-
In general, tailings impoundments and the embankments .that confine them are designed using
information on tailings characteristics, available construction materials, site specific factors (such as
topography, geology, hydrology and seismicity) and costs, with dynamic interplay between these
factors' influencing the location (or siting) and actual design of the impoundment.
The three methods of embankment construction (upstream, downstream, and centerline) differ with
respect to the quantity of materials required for construction and the types of operational and designed
controls that may be incorporated into the structures for stability and environmental performance.
For fn
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3SIA Guidelines for Mining • Environmental Issues
permeable layers of the foundation may result in piping or exceedence of soil shear strength, causing
foundation subsidence and compromising the stability of the overlying embankment.
The .phreatic surface is the level of saturation in the impoundment and embankment (the surface along
which pressure in the fluid equals atmospheric pressure (CANMET, 1977)); in natural systems it is
often called the water table. Factors that affect the phreatic surface in the embankment include the
depositional characteristics of the tailings (permeability, compressibility, grading, pulp density, etc.)
and site-specific features such as foundation characteristics and the hydrology and hydrogeology of the,
impoundment area and its upstream catchment area. Changes to the phreatic surface can be caused
by: malfunction of drainage systems, freezing of surface layers on the downstream slope of the dam,
changes in construction method (including the characteristics of the placed material), and changes in
die elevation of the pond. The level of the water table also may be altered by changes in the
permeability of the underlying foundation material; sometimes these are caused by strains and
subsidence induced by the weight of the impounded tailings (Vick, 1990).
Impoundment design must provide for a cost-effective and reliable containment system. Choices
regarding materials, slope angles, drainage control, raising rates, etc., all affect the cost as well as
the stability of the structure. Therefore, stability analysis is performed to optimize the structure with
respect to cost and other objectives while maintaining reliability.
Slope stability analysis begins with an estimation of the reliability of the trial embankment.
Typically, the embankment designer proposes the internal and external geometry of the trial
embankment and then calculates the safety factor of the design. Using detailed information on the
physical properties of the fill material and estimates of the volume of tailings and water to be
contained in the impoundment, the phreatic surface is predicted. The designer then examines a wide
range of failure modes to calculate the estimated stresses expressed at hypothetical failure surfaces.
The safety factor for each failure mode is then calculated by dividing the estimated resistance of the
embankment to stress along the failure surface by the stress load expressed at the failure surface.
With this process the designer can look at changes in design parameters and the resulting influence of
the safety factor to arrive at the least-cost option consistent with safety objectives (Inyang, 1993).
The major design precept is that the phreatic surface should not emerge from .the embankment and
should be as low as possible near the embankment face (Vick, 1990). The primary method of
maintaining a low phreatic surface near the embankment face is to increase the relative permeability
(or hydraulic conductivity) of the embankment in the direction of flow. This is accomplished by
using progressively coarser material from upstream (Le., the tailings side) to downstream and/or by
incorporating drainage features (e.g.", chimneys drains, blanket drains) in the dam itself to keep fluids
away from the downstream face. Tailings slimes, clays, and/or synthetic liners (rarely) may be used
to reduce permeability of the upstream face.
4-41 September 1994
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I
I ' '
~i^==EnyifoiimeBialfesaes ' EIA Guidelines for Muring
Other means that, in various combinations, are used to maintain a low phreatic surface near the dam
include:
I I I y i . i
• Reducing the water content of tailings by dewatering prior to disposal.
, * Reducing groundwater infiltration into the tailings. This can be a serious problem, at least
seasonally, when tailings impoundments are placed over alluvial materials. Infiltration can
i of ..reduped by preparing the ground surface in the impoundment-area: "lining" with
L ^j native gojig and fa^ imported clays, or even synthetic liners, and possibly
r n^^inc* im^A^ ffcAPa l*na«*r> +*% nfvmvaetT +1+e** «M>«%»v«*«3***«*,A« » At_ :*_t_ _ ^_«*» . _
including drains under these liners to convey the'^roundwater underneath the tailings.
Incorporating drains underneath and through the dam to ensure that any seepage/drainage is
controlled. This can include incorporating'filters orjlter zo^^upstream of drams to help
prevent clbgfmg^ hence maintain differences in r«rmeabiiity across zones. Filter zones
may be constructed of graded sands or synthetic filter fabrics (Vick, 1990).
" ' '
^E II1III. In ill * s: il^SSSiSSi ?§ IM? !*??, w**?r Ii toe impoundment as possible by recycling water to the
i , mil or by"decanting water aid pumping it.to an alternative fines settling and water storage
111111111111111' 11 llllllllll 11 lllllf Illlllllllllliiili III 111 111 1111111111 111 I IP' I II ill i IT ii I
i mi n n iii i nnllllnillini i linn nnnnnnnnn iiiini inn mi inn n i n i n inn nn nnillllnn i in win inn i in mi inn 11 11 niiii|iiiiiil ill inn i mi linn nil inn in|i 11 n n niilinnnnnn inn inn 11 n n inn mi inn n nil in inn n in i n 11 i i inn 11 n
i ii in iiiiiii n iiii inn in iiiiiii i iiiiiiiiii iiiiiiiiiiiiiiiiiii|iiiiiiiiiiiiiiin i immmmimimm m««m immmmmmmimm minim immmmmmmmmiimmmimm iiiiiiiiiiiiiiiiiiiiiiiini in nil n i n iiiini iiiiiiiiiiiiiiiini i nun iiiiiiiiiiiiiiini iiiiiii iii n i inn iiiiiiiiiiiiiiiiiiiiiiiiiiiii mini i mini inn pi iiiiiiiiin|iiiiiiiiiiiiiiinn iii i mini ««««««inn «i|iiiiiii««««««««« minimi in nil mi inn niiiiiiiiiniinnnin i n n i i inn 11 n
* Maintaining free water as far behind the crest of the dam (i.e., as high in the catchment) as
possible by sloping the surface of the tailings upstream away from the dam.
• ii'i'iji! iiii iiv ii • • ' •
I S Allowing fluids to escape into the subsurface. This.is generally not an option since States
! k generally impose strict groundwater protection •*•«'»•««« • . •
* Diverting runon away from and around the impoundment and dam. This is accomplished
•iiiiiii iiiiiiiiiiiii: mi iiiii'i i! ! with benns and other water diversion techniques.
i ; r I •
PERFORMANCE
, , , . ..... .
The selection of any of these approaches to embankment design has implications for the operational
long-term environmental performance of the impoundment system. For example, incorporation
...... £ ...... SlSE-IEE £«ssure ,H!*i? ,*?. 45m provides a
, ..... , ...... ...... - , ,.
..... Sease ofcomamjnatgd_ ...... Iuids: ............... UiSer, ..... existing ^JDES effluent guidelines, such releases
typically wffl require collection and return to the injwundrnent smce discharges are prohibited from
' ..... a iiner l° prevent downward
, °f P°Uutants to shallow groundwater. Embankment drainage systems also create a post-
...... SSSffii ............. ..... SB ..... fP*0"041116111 fe fey *«ign not impermeable,
contaminated effluent, possibly including acid rock drainage, may be released from the impoundment
^kr tp6 active life of the project. If the active pump-back system for the toe pond is no longer in
operation, such effluent may be released to area surface water. Accordingly, treatment-in-perpetuity
or some alternative passive treatment or containment method may be necessary to prevent surface
water releases.
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EIA Guidelines for Mining Environmental Issues
Another trade-off between stability and environmental performance is the incorporation of liners. In
areas of shallow alluvial groundwater,' liners may be necessary to prevent intrusion of water into the
impoundment. However, such liners will simultaneously increase the retention of impounded water
behind the dam and reduce dam stability, all else being equal. On the other hand, the absence of a
liner may increase the downward migration of impoundment constituents to shallow groundwater.
Surface water controls may be of particular importance in post-closure stability considerations. .
Surface water runoff diversions are generally employed to limit the intrusion of excessive amounts of
water into the impoundment, which reduces dam stability and prevents drying of tailings. Failure.of
surface water controls after impoundment closure could result in an increase hi pore water pressure
within the impoundment, threatening the stability of the embankment. In general, active measures to
control surface water runon and runoff during the operative Me of the project may require alternative
methods or long-term management after closure.
4.4 NATURAL RESOURCES AND LAND USES
The act of mining can result in major changes to all natural resources on and hi the vicinity of the
mine. This section describes several major natural resource systems that may potentially be impacted
and the types of impacts mat may occur.
4.4.1 GROUNDWATER .
The potential impacts to the groundwater resources hi the area of a mine are similar to those that can
impact surface water quality. Acidic water from mine drainage, metals, cyanides, or other toxics
from the mining operation may enter groundwater in the vicinity of the mine. Elevated pollutant
levels can contaminate drinking water supply wells.- Disturbance hi groundwater flow regime may
also affect the quantities of water available for other local uses. Further, the groundwater may
recharge surface water downgradient of the mine, through contributions to base flow hi a stream
channel or springs. Conversely, surface water affected by mining operations can recharge
groundwater, particularly alluvial aquifers.
An assessment of potential groundwater impacts requires that the baseline groundwater resources hi
the area of the mine be completely characterized, including descriptions of the aquifers (bedrock and
alluvial systems), aquifer characteristics, flow regime (an understanding of the potentiometric surface
for each aquifer), springs, and background groundwater quality. At least two years of groundwater
quality data are generally needed (or an alternative interval that is sufficiently representative of likely
variabilities hi groundwater quality). The collection of baseline groundwater data should be described
in study plans that ensure that useable data is being collected. The collection of these data usually
requires the installation of a groundwater monitoring network of wells. Where wells are installed,
4.43 September 1994
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iiiiliii iiiinili in IIIM^^^ iiiiiw^ iiiiiH^^^^
liiTironmental Issues
EIA Guidelines for Mining
documentation should describe the location, depth, construction/completion data, and sampling and
analytical methods. • . ,
"' ' ! i," • .
In addition, to the baseline characterization of the groundwater in the project area, the following
information is generally needed to allow an assessment of potential impacts on groundwater resources:
: ="iL'iES ..... ::<::< i::: ' i i:::1::: . [[[ ' ...... ' [[[ ' ............................................ I [[[ '
' ..................... •'|'"'1' '"'"" 'l|"'1" "'""' ' !lj ................... '" •"" Location and construction design plans for toxic materials storage areas (cyanide, oil, etc.),
waste management units (focusing on impoundments), leach units, solution transport
ditches, process ponds, and surface and underground workings. These should be reviewed
in conjunction with hydrogeologic data (particularly the potentiometric surface for each
aquifer in the area of the proposed units). Any practices to be used to protect groundwater
resources (liners, grouting, etc.) .should be examined closely.
wiS • Acid ...... generation potential for the waste rock, tailings, and the mine workings.
: .waste, .rock and, ore to defennine what, metals, and gther , : - ; •
present and avalable for !
• If the rock has a net acid generation potential, mitigation measures should be outlined.
Iv'ilIF1'!1! - ' ' . i ., .
L.Y.ILocations of and information on any local residential wells or well fields and an evaluation
S™lj««S,;™"j,^S«Sf howtii^y may be .impacted by the new source (both in terms of quantity and quality)
' "
Where there is a hydraulic connection between ground and surface water, an analysis of
how potentially affected groundwater could affect surface water flow and quality (and vice
yersa),;> When dewatering can create a significant cone of depression and affect the
of gjomid water/or surface water recharge (see section 3.L4.1), mfbrmation on
both short- and long-term effects would be necessary.
111 Illllllllll lilllllB II III llllill I III II 111 111 !ll 111 111 lllllll 1111 111 111 II1) ill 111 III II 111 1 III) i III llllllill III Illlill 1 111
SSES SlBlMpg » such that h causes massive land disturbances. These disturbances hi turn can
IS® major types of impacts on aquatic resources, including aquatic life. The first type of impact
would result from die contribution of eroded soil and ngterial to streams and water bgdies (see
. ' I Sli^jji "JM |§ g°i| iE-please" of poJJ^1""^^1»—— ^^ -—.««..-. —- — «m^ ^
' ° 6™ streams; wetlands r
other, water bodies. IJeinpjMrary disruptions would occur, from road, construction. and similar activities.
Permanent impacts would be caused by actual mining of the area or by placement of refuse, tailings,
or waste rock directly in the drainageway—more often than not* this is in the upper headwaters of
intermittent or ephemeral streams. (Both types of activities are subject to §404 of the Clean Water
Act—see section 6.1.)
' - it. i in
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UA Guidelines for Mining ^^ Environmental Issues
Means to prevent future impacts, from the release of pollutants to surface waters from waste materials
or from mine workings should be addressed in a reclamation plan, and effective reclamation can
provide substantial mitigation. As is noted elsewhere, however, reclamation plans for metal mines
are often only conceptual at the time of mine permitting. Thus, preparers and reviewers of EAs and
EISs often must rely on applicable reclamation requirements and on the processes that are in place to
ensure that reclamation planning proceeds according to those requirements.
For impact assessment purposes, aquatic life is generally defined as fish and benthic
macroinvertebrates; however, phytoplankton and other life forms may also be considered, depending
on the type of aquatic habitat and the nature of impacts being assessed.
Impacts to relative abundance or biological diversity may occur as a result of chemical and physical
changes or from direct removal or introduction of species.
A detailed discussion of the many approaches and methodologies that may be used to define and
. monitor aquatic resources is beyond the scope of this document. However, there are numerous
reference documents that can be used in assessing the environmental impacts to aquatic life associated
with a proposed action. Several examples include:
Harrelson, C.C., C.L. Rawlins, and J.P. Potyondy. 1994. Stream Channel Reference Sites:
An Illustrated Glide to Field Technique. U.S. Department of Agriculture, U.S. Forest Service,
Fort Collins, Colorado.
Platts, W.S., W.F. Megahan, and G.W. Minshall. 1983. Methods for Evaluating Stream,
Riparian, andBiotic Conditions. -General Technical Report INT-138. U.S. Department of
Agriculture, U.S. Forest Service, Ogden, Utah.
U.S. Environmental Protection Agency. 1989. Ecological Assessment of Hazardous Waste
Sites: A Field and Laboratory Reference. EPA/600/3-89/013. •
U.S. Environmental Protection Agency. 1989. Rapid Bioassessment Protocols for Use in
Streams and Rivers: Benthic Macroinvertebrates and Fish. EPA/440/4-89/001.
U.S. Environmental Protection Agency. 1993. Habitat Evaluation: Guidance for the Review
of Environmental Impact Assessment Documents.
The impacts of a proposed action on aquatic resources can be either beneficial or adverse. It also
may vary significantly, depending on the species. For example, increases in stream flow may
preclude habitation of certain species of macroinvertebrates and/or fish but, at the same time, may
also provide new habitat for other species of aquatic life. Too often, impact assessment is based on
single species management. A more productive approach is to consider the entire ecosystem.
Whether the analysis considers the entire ecosystem or an individual species, endpoints/criteria must
4-45 September 1994
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Environmental Issues
EIA Guidelines for Mining
! IIW f f!!1'
llllllH
be established by which the impacts of the project will be evaluated. Assessment endpoints are
enyironmental characteristics which, if they were found to be significantly affected, would indicate a
nee||
regulated species of macroinvertebrate may not be directly considered a valuable species but it could
be an important component of the food chain and local ecosystem which contains other valuable
l 5£'ajJ5|>osed action on aquatic life can most effectively be determined insufficient
baseline data are available. In general, baseline aquatic life studies of one or more years reflecting
nxujtipje seasons («.g., spring, ,2222; fall) are-needed to adequately describe reference
'Annual ancVseasonal variation m .aquatic life g|rolations (especiaiy macroinvertebrates)
; normal.Without adequate baseline data, it is not possible to measure if changes in abundance
tion°afc from anthropogenic activities (e.g., mining).
should be obtained directly from the drainage to be affected by the
] Jhfcfarfe not feasible, background data should be collected from'an,,iinimpacted
" ecosystem (e.g., reference site) with similar characteristics to the proposed impact area. (In
been degraded ^ historic mining (or other) activity. There, it
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EIA Guidelines for Mining Environmental Issues
the primary purpose of a study is to determine the presence of a threatened or endangered fish
species, for example, it would be inappropriate to use rotenone, which has a 100 percent mortality
rate. The references cited above provide guidance on method selection and use (both for baseline and
long-term monitoring). In addition, the potential presence and effect of metals such as mercury Or
selenium that are bioaccumuiated should be addressed.
An important variable that the operator and the reviewer should consider in aquatic resource
assessments is the duration and extent of the proposed impacts. For example, if the proposed action
{or potential alternatives) will temporarily decrease stream flow during one season, the impacts on
aquatic resources would be expected to be different than if the activity will lead to long-term effects
(including post-mining conditions). The related indirect impacts of the activity should also be
evaluated. For example, if development of a proposed mining operation provides access to an
otherwise inaccessible land/drainage area, the potential affects of non-mining related human activity
(e.g., recreation) should be considered. Another important consideration in an historically mined area
would be me cumulative impacts of the proposed operation. Thus, the fact that the area to be mined
was degraded from past mining activity would not eliminate the need for a full-scale assessment of the
cumulative impacts of mining (and other) activities on the aquatic resources and of the incremental
impacts of the proposed operation.
4.43 • WILDLIFE
Similar to aquatic resource evaluations, numerous references are available to assist hi evaluating
potential impacts on wildlife or in evaluating data and studies that are submitted by applicants.
Several examples include:
U.S. Environmental Protection Agency. 1993. Habitat Evaluation: Guidance for the Review
of Environmental Impact Assessment Documents. ~ '
U.S. Environmental Protection Agency. 1989. Ecological Assessment of Hazardous Waste
Sites: A Field and Laboratory Reference. EPA/600/3-89/013.
Wildlife Society, The. 1980. Wildtife Management Techniques Manual. Fourth Edition:
Revised. Sanford D. Schemnitz (editor). Washington, D.C.
In general, many of the same concepts described above (section 4.4.2) for aquatic life apply to
assessing impacts to terrestrial wildlife. The assessor/reviewer must still determine the endpoints for
the assessment, including whether to consider impacts on individual species, populations,
communities, and/or entire ecosystems In determining which species or communities are of concern
in the affected area, there should be consultations with experts from State and Federal agencies.
Species' importance/value may be defined by legal (e.g., threatened and endangered listing),
commercial, recreational, ecological, or scientific value. In some instances, it may be desirable to
4-47 September 1994
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Enyironmental Issues
EIA Guidelines for Mining
focus on certain species; however, it is usually preferable, to assess impacts on the overall
ecosystem. ' " " ' '
Biological diversity is often viewed as a way. to measure the health of an ecosystem. For example, a
decline f° fce species diversity of an area could indicate a deterioration in the quality, and possibly a
decrease in the stability, of that ecosystem. Direct loss of mdiyiduals' (mortality) or a decrease in
fecundity may affect species diversity. The above references describe available methodologies for
..... ESSE:?.! ..... — ..... ,*S!!°n. ..... 2251 ...... *S3S ..... *€** imP301 is an important consideration for
^,,!le, ...... E2!l!!!S!0,n P*1386 or during operations, for example, may displace .local
areas surrounding the site. Some individuals or
and
, ..... ,, ...... ..... ....... , ..... ...... ...... ,
•MjSHiS&ttpp^ operational activities. .Still other individuals may be permanently displaced for the life of
111111" lllllll!1 ill llll'llh 11 ' "111" 1111 "I1 IIHy lllil111111111111111111""11111111111111 llllli iiiiiiiiiiiiiiiiiiiiiiiiiiiii iiiiiiiiliiiiiiiiiiiii iiiiiiiiii iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiliiiiiiiiiiiii inn miiiiiiiiiniiiiiiiiiiiiniliiiiiiiiiiiii iiiiiiiiiiiiiiiiiiiiiiiiig game, and small mammal^ the objective of the
program (qualitative versus quantitative); and numerous parameters such as the size of the project
!??? * c ........ found ...... in ...... the project area.
methods that can be used to determine presence and relative abundance of wildlife.
jaaybe surveyed using Sheman live traps, pit traps, and snap traps. Raptors may be
" or on foot. Auditory surveys are often used to survey for wildlife which is
t to observe (e.g., songbirds and frogs). | Surveyors may_ count animals observed and/or rehr
pSgjgSgj^ ^££1 IjackSj scat, etcj; U£«U£gB J£ PJ!!!E^ ^PM when surveying for animals
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EIA Guidelines for Mining _ Environmental Issues
The indirect impacts of a proposed action on wildlife near the project area should also be considered.
For example, a mining operation may be located to avoid impacting an elk migration corridor.
However, elk could be adversely affected by associated increases in housing construction which may
result from an unproved local economy.
NEPA documentation for proposed Dining activities should include mitigation measures which may or
will be used to minimize or avoid impacts to wildlife. Potential mitigation measures for use at mine
sites include: . .
• Avoid construction or new disturbance during critical life stages. For example, delay
construction activities until after sage -grouse strutting occurs at nearby leks.
• Reduce the chance of cyanide poisoning of waterfowl and other wildlife, particularly in arid
environments, by neutralizing cyanide in tailings ponds or by installing fences and netting to
keep wildlife out of ponds. Explosive devices, radios, and other scare tactics have
generally not been proven effective.
• Minimize use of fences or other such obstacles in big game migration corridors. If fences
are necessary, use tunnels, gates, or ramps to allow passage of these animals.
• Utilize "raptor proof* techniques on power poles to prevent electrocution of raptors. For
example, use anti-perching devices to discourage birds from perching or nesting on poles,
or place conductors far enough apart to ensure both wings don't contact them at the same
time.
• To TTMT"T"i*e the number of animals killed on mine-related roadways, use buses to transport
employees to and from the mine from an outer parking area.
• To limit impacts from habitat fragmentation, minimize the number of access roads and close
and restore roads no longer hi use.
• Prohibit use of firearms on site to minimize poaching.
As noted above, mining operations can have substantial impacts on terrestrial wildlife, ranging from
temporary noise disturbances to destruction of food resources and breeding habitat. Unless closure
and reclamation return the land essentially to its pre-mining state, at least some impacts to some
individuals or species will be permanent. Coal mines, as discussed in chapter 6, must return the land
to its "approximate original contour" and revegetate as part of reclamation. When successful, this
can often minimize any long-term impacts. Metal mining, on the other hand, only rarely goes this far
4.49 September 1994
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I ill ill in ill mmt , imt •• ii ni 1111
Environmental Issues
iiiill Illllll Hill liililnl Illillii 1 l»'|iii Ill
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BDV. Guidelines for Mining
iiliiiilH
although most disturbed areas are often returned to productive states following metal
ill lli llllllllll
lllllllllllllllllllllllllllllllllllll|lllllllllllllllllllllllllllllllllllllllli lllllllllllllllllllllllllllllllllllllllllllllllll|lllllllll| | H I ' v
mhting. there are usually significant differences in topography and in vegetation. These hi turn result
a jnjMcts to wildlife, in that they affect available fo^ water and coyer. One of the major
reclamation is to minimize permanent impacts, so reclamation plans are crucial to
mitigation. Because reclamation plans are often (or usually) only conceptual at the time of metal
SHBC remitting,prejjarers and reviewers of EAs and EISs must often rely on applicable reclamation
requirements aid on the processes that are in place to ensure that reclamation planning proceeds
' According to those requirements. •• . ' • " •'•
VEGETATION/WETLANDS
Vegetation consists of natural and managed plant communities. Native uplands consist of forests,
s and grasslands; managed uplands include agricultural lands, primarily croplands and •
................................................. li ...... ; ........ : ............ ! ................ I ............. ; .............. i, " • • , ~ .............. i ........................................ J_ [[[ =, , • [[[ • ......................................
................................................. ...... ........ ............ ! ................ ............. .............. , • , .............. ........................................ _
pastures. Lowland vegetation occurring within drainages forms riparian communities, including
21?- ...... il!iii§§!6! ..... feelow focuses on upland and lowland plant communities; the impact of
on agricultural lands is discussed below in the L?nd Use section
!p. ..... giant ...... communities ....... Perform ..... a ..... number ...... of functions ..... in the ...... landscape. As discussed previously,
ion supports wildlife, with the diversity of vegetation strongly related to the diversity of
Vegetation stabilizes the soil surface, holding soil in place and trapping
i ....... JE ..... SfeSSSHSS ..... IS ...... SS^
..
soil moisture and lowering surface temperatures. A diverse landscape also provides some
tegipee of aesthetic value. | In the, case of rangeland, native communities, provide the rimary
..... used ..... to ....... feed ..... livestock; ............... Riparian
wetlands
defined in Wetland Evaluation Technique (WET) Volume tt: Methodology (Adamus et al., 1987);
™®6* r?diaipj ........ @) ...... loodlPW ..... ftttenuation; (3) sediment stabilization; (4) sedunent/toxicant
...... (5) ..... nutrient ...... ranpva|Aransfor|nati|M^ (6) primary production export; (7) wildlife diversity/
mdance; (8) recreation; and (9) uniqueness-and heritage."
vegetetion within the active mining area is removed prior to and during mine development and
uaPacte^ ty m« roads, water diversions or other
,, .............. ..... ......
dixejpplient. Vegetation further removrf from activities^ may be impacted by sediment carried by
riMislsVi&iii 1°J| and by fugitive dust.
i1
..... Jojnegetation typically involves a study describing the major
cainnninitjesi ....... or ...... associations, ...... withjn ..... ,the ..... affected area. The description of each community should
,Jll ....... I ............... jil ........................................ S ............... II ............... I ............ lllllllillll ......... I ............ Illlllllllllllllll ........... I ............. II .............. I .................. | ................. I .............................. U ............. ; [[[ ; ............................. »» I I * [[[ *
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EIA Guidelines for Mining . Environmental Issues
non-coal mines, the change in surface configuration may result in completely different plant
communities being established. Coal mines, under the SMCRA requirement to restore the
approximate original contour and premining land use, often attempt to establish plant communities
that resemble those tftat existed prior to mining.
The requirements for defining and mitigating impacts to wetlands is more rigorous than other
vegetation community types because of their protection under §404 of the Clean Water Act (see
Section 6.1). The placement of dredged or fill materials into wetlands or other waters of the U.S.
requires that a Section 404 permit be obtained from the U.S. Army Corps of Engineers (Corps).
Permit applications must include a jurisdictional wetland delineation for each of the wetlands that may
be impacted. Delineations are conducted as described in the Corps of Engineers Wetlands Delineation
Manual (USAGE, 1987), and are based on an assessment of vegetative, hydrologic and soils criteria.
If "jurisdictional wetlands" are identified, the project must comply with the §404(b)(l) guidelines (40
CFR Part 230).
Compliance with the §404(bXl) guidelines requires mitigation for any impacts to jurisdictional
wetlands. The guidelines require mat avoidance of impacts be considered as a first mitigation option.
If avoidance is not possible, the guidelines further require the selection of an alternative that results hi
the least amount of impact to wetlands and that some measure of compensation be implemented for
impacted areas. Under the guidelines, the Corps may not issue a permit if the discharge will
substantially damage the aquatic ecosystem if practicable alternatives exist.
Development of a mitigation plan should include an evaluation of the functions and values provided
by the. wetland areas under analysis, the extent of proposed disturbance (acreage), and an assessment.
of potential cumulative impacts to surrounding wetlands. Based on these site-specific factors,
mitigation requirements are usually established on a case-by-case basis. Mitigation may involve
restoration, creation, enhancement, exchange, or in some cases, preservation of wetlands located
either onsite or offsite.
The assessment of wetland functions and values, in the context of a mitigation plan, tend to be
inherently subjective. While functions are tied to properties of the wetland itself, value tends to
reflect societal influence and are necessarily subjective. However, the proximity of one wetland to
others, the uniqueness of a particular wetland, .and the number of functions it performs all influence a
wetlands value. Mitigation considerations include whether the target is to be an "in-kind" or "out-of-
kind" wetland in terms of functions or community types compared to the original. Location (onsite
or offsite), timing (before, concurrent, or after), and mitigation type (restoration, creation,
enhancement, exchange, or preservation) are other variables that must be considered in developing a
mitigation plan. Depending on the variables involved, the ratiaof the areal extent of compensation to
disturbance can range from 1:1 to more than 3:1. Barring avoidance, the preferred approach would
4-51 September 1994
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liii'ili
Environmental Issues
EIA Guidelines for Mining
[[[ .................... began. uci a
in-ldid and onsite, completol before development activities
"
stor:iinpacted ratio may be cose to 1:1. The ratios increase in
situatipns ,
succss can only be acjrieyed through a greater degree of difficul^ or when the
: mitigation cannot be completed before initiation of the project (Kruczynski, 1990).
Wetland restoration and creation tends to be as much art as science under the current state of
knowledge. Therefore, success should be evaluated using a set of clearly defined goals to be achieved
within a specific time frame. Goals should be established in the planning stages. A monitoring plan
should be developed and implemented to ensure that newly restored/created wetlands progress toward
........ the previously ..... defined target ...... in a ..... timely ...... manner. .............. The ...... establishment of clear goals and an effective
monitoring plan are of key importance to project success but are often overlooked hi the planning
i iiiiiiiiiiiiiiiiii iMiinnnnnnnnnininninninn 1 1 nun «iii««iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii|||iii nuiiiiiiiiiiiiiiiiiiiiiiiii iiiiiiiiiiiiiiiiiiiiiiiiiiiiifim ........................... iiiiiiininn ...... nnnnnnnn ...... niiiiiiiiiini ..... iLiin ........... ..... i .......... in [[[ i ...................... n i j nn i ik in ........... i n i \ r ........................... S ...........................................
stages.
nh ii ill i I 111 II |l IIIII lull i II ill II 111 11 III i
4.4.5 LAND USE
i n • •
Metal mining nearly always results hi significant changes to beneficial uses of land after mining. A
description of land use should identify the current use of land needed specifically for the mine and
land use patterns in the nearby area that will be indirectly affected by the project. Particular emphasis
should be placed on land uses that pose potential conflicts with.mining operations—farming timber,
grazing, recreation—and on the local or regional zoning laws that may limit the development of
m|n|Tig operations.
Farmland
U.S, Soil Conserv^on SwjS.SS!,,- S2Fged *"***
and locating Prime and Unique
fermland under Public Law 95-87. The SCS works with State and local agencies, to identify
fiuTmand of statewide or local importance. Farmlands in the vicinity of the mining project under
evaluation should be identified by SCS categories.
iSiiilS.!^13^ maintains lists -of all soil series that fall into the categories of grime, unique, and
State/locally important. Depending on location, lists may be generated and maintained on a county,
llill (1 Ill I | ill Ill lIllH HI! J ° 1 iZmmm SiiiXS..!
_^_ " ~ ~ < ' ' • " '
21, ?tatewide basis. Where appropriate, the reviewer (or the applicant) should contact SCS (or
State/local agencies) to verify the existence of designated ^^^ ^ ^ vicmity Of a
proposed mining action.
best combination of physical and chemical characteristics for
producing food, feed, forage, fiber, and oilseed crops that is available for those uses. Prime farmland
i and exists within
characteristics mclude a lack of rock fragments, a pH range of 4.5 to 8.4, water holding
capacity to a
i'illlllllU! IIIIIH^^^^
of 40 inches and adequate to produce
, and an average annual soil
-------
~E3A Guidelines for Mining 'Environmental Issues
temperature of greater that 32°F at a depth of 20 inches. The prime designation also relates to the
availability of irrigation or a sufficient precipitation regime to sustain crop production.
Unique farmland demonstrates similar characteristics to prime soils and produce high value food or
fiber crops. However, these soils lack a particular characteristic that separates them from prime -
precipitation for example, may limit crop production to eight out of ten years. Soils of statewide or
local importance are identified based on unique characteristics identified on a local basis. Local
conditions or characteristics restrict, production on these soils to a greater extent than soils classified
as prime and unique.
In addition to prime, unique, and State/locally important farmland, EPA's September 1987 policy
identifies three other types of environmentally significant agricultural lands for protection. These
include: farmlands in or contiguous to environmentally sensitive areas, farmlands important for waste
utilization, and farmlands with significant capital investments in best management practices. Such
determinations are made on a site-by-site basis.
Potential impacts from proposed mining actions to farmlands can range from complete elimination of
the land for fanning use to temporal cessation in farmland production. Analysis under NEPA should
specifically consider the effects of an activity on the important soil/farmland categories described
above (as well as the feasibility and likely effectiveness of proposed mitigation measures). Wherever
possible, mitigation measures should allow for returning the land to its previous productivity. For
example, the operator could strip a particular soil series by horizon and stockpile each separately,
with die intent of restoring the soil profile upon completion of mining. Under SMCRA, coal mines
are required to restore prune farmland to its previous state (no such uniform requirements exists for
noncoal mines).
4.4.5.2 Timber .
Timber lands should be identified in the project area and the board feet of lumber represented by that
timber should be estimated. Impacts .to timber are typically the loss of the resource in the. areas to be
cleared for the mine. Mitigation of the loss of timber lands includes the economic harvest of the
existing timber prior to clearing and construction of the mine. Reclamation of the mined areas may
require the replanting of trees but the land may be rendered unusable for timber growth at the close
of mining as a result of poor growing media, or the presence of large excavations. Any mitigation
measure that calls for tree planting (or, indeed, any revegetation) should include monitoring for
several years to verify its success.
4-53 September 1994
-------
11 iiiiiii 111 iiiiiii iiiiiiiini i in i nil i in n 11 |iiiiiiiiiinninnn nn in iiiiini in in i in 11 in iiiiiiiiiiiiiiiiii n111 innninnUi iiii iii iiiinni in in i iiii "i n n n in i nn iiiiini in iiiinni n i nn 11 in n iiii'in in 1111 M nn iiiii nn iii n in i n i n iiii i nn MM nn in 111 in iiiiini nn 11 n i in iii i iiiiiinii mini iiiinni iii iiiinni inn i iiiinni 11 in' i in in iiniiii n n i in n in iiiiini I in iiii 11111 in 11 inn n in n nn iii i n i in i n inn nn in in ninii|niiiinnn iii i nn i iiiiiinn|n i n' iiiiiinii n 111 i in i in iiiinni
i| 'I'lllllllllllllllllllillillllllllllllllllllll I'M..!!.. . n IIIIIII Illllll mmw 111 i IIP III Illllll fill lliilllllllllllllllllPlllllllIIII i 11 IIII1! V 'III lillil«i««l««|i II III 1 Iiiiiinii 111 •lillnlllPllli'll MM1 \ III III ill 11III ill Illllll II«|I Illliillllllllillilli^ 'IliliIIIIIilllll IIIII 11 IIIIIIIIIIIIIIIIII III 1111^ I 111 III Illllll
iiiinni iiii iii iii i n iiiiiii iiiiiiiini nn n n iiiiini nn iiiinni 11 in in iii i iiiiiiiiiiiiiiiiii i in n iiii in p i in ii i ni nil iiii i HI i in i n iii 11 iiii n iiinnin inn n iniiinini i n i nil in n inn nn iiiiini i in iiiiini iniiiniiiiniii|iiiiiniiiiiiiiiiniiiiiniii||iiiiiiinii iiiiiii in i inn n n i linn nn i iiiii i
jn p in in M ii HI g i in, iii iiiii 11,1 iiiiiiiiiiiii iiiiii ii iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii in iiiiiiiiiiiiiiiiiiiiiiiiijii n i iiiiiiiiiiiiiiiiii nn 11 nil n 11 iiiiiii niii iiiiiii iiiiiii Ii I in1" ' iL '" "
ill i' v i piniiiiiiiiiiiiiiiiiii in 1111111 iiiiniiiiiiiiiiiiiiiiiiiiiiii iiiiini ill i 1111 iiiiiiiiiiiiiiiiiiiiiiiii i iiiiii nn nn ni nn i nn ii1ill inn I'liii in i in inn nn 111
! ' Environmental Issues
n iiinnin inn n in n nn in i in i n i nil in n iii nn iii i in nn in in in |i i ii iii inn iiiinni i iiiiiiiiiiiii •• in i inn n n iiiii i iiiii in in in iiniiininii i i HI nn 11 iiiii in iiiii iiiiii
inn • if«ii'i iiiiii iiiiii iiiiiii i1 nii in mill iiiiii Tiiiiiiiiii iiiiiiiiiiiiniiii 1 iiiiiiiiiiiii iiiiiiiiiiiiiiiiii iiiii iii iiii iiiiiiiiiiiiiiii '»iiiiiiiiifiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii iiiiiii
ii iiiiii iiliiiiiiniiiniiiini
4.4.53
EIA Guidelines for Mining
Grazing
The extent of lands used for grazing should be identified within die vegetation survey conducted for
the site. The area! extent of each plant community in which grazing occurs and the extent of
disturbance within those communities should be reported. The animal unit months (AUMs) each
coinmimiry is able to support and vegetation biomass data should be included. Where slopes of pits,
benches and highwalls do not prohibit it, reclamation in most cases will readfly support grazing in the
post-mining landscape.
4.4.5.4 Recreation
m the area of proposed mining projects may be used for public recreation. The types of
recreation provided by the lands in the vicinity of the project should be identified! Potential impacts
should be described with respect to the current level of recreational use as well as opportunities for
additional uses. The extent to which recreational uses will be restored after reclamation should also be
'4.4.6 CULTURAL RESOURCES
iiiii ,( ' i1 ...... iiiii H ...... ' ....... mum iiiiTiinii IH ii ...... 1 1 1 ii •iiiiiiiniB " i ...... .......... wmmtf ..... I'liiii 1 11 ........ IM ....... i in in ....... iiiii < " ii ' i no ii'i
i ....... Cultural resources ...... encompass several areas relating to man's knowledge and appreciation of
prehistoric and historic events. The location of a mine or beneficiation faculty at or near significant
•iiiii
felSSllg ..... J?nds ...... of sites ...... should ...... be,,,,,described ..... .irrrelation ..... to .the project
• mmm
•
f. Arjcheological sites (where man-made artifacts or other remains dating from prehistoric
times are found). These are not uncommon, particularly in the west.
*:=:l^epi^lpgical sites (where significant events happened or where well-known people lived
worked). Again, these freouentiv occur on proposed sites in the west.
ional, religious, scientific, or cultural value. Once again, these are
encountered, particularly .in the west. Native American values (including
5r3!m'iCin£!£2ii!0*B and cultural values associate^ with certain areas) are of particular concern. As
opted in Chapters, artifacts and remnants of historic mining are also increasingly being
protected asiultujal resources. ]
z^=£: ™.,i^™! I;* ; ;, BEPpcrttes on or eligible for listing on the
106 of the National Historic Preservation Act.
i ""iiv'iniii: ih iiiiiiiiii«iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiihiiiiiiiiiiiiiiiiiiiiiiii«iiiiiiiii«iE^ 111111111111111 .u, iiiiiiiniiiiniiiiiniiiiinniniinii i 11 iiiii; 114111111111111111111 iinniiiiiiini 11 ii'n i in in iiiiiiiiiiwiii ini n iiii inlii iiiiiiiiniiiniiiiiiiiiniiiiiiii iinnnii i in in iiiiii 111 n in win IIIIIH
Register for protection under Section
I IIIIIIIIIIIIIIII HI I IIIIII 1111! 1 lull 11 il 1111III ' 11111 ll|li i IIIIIIIIIIIIIIIIII 111 i 111 nl nl III
, a discussion of mitigation
I HI IIII lull II il i I'll "I I ill III
iiinnnnl n ill iinnnili n nniii n n n ill nn i n 11 inn ii in nn n in iiiiini
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EIA Guidelines for Mining • ' Environmental Issues
4.4:7 AESTHETICS
Aesthetics involve the general visual, aural, and .tactile environment. A description of the aesthetic
characteristic of the existing environment should include things that are seen, heard and smelled hi
and around the site and their emotional or psychological effect on people. Descriptions (or pictures)
of views of the site, of unique features or features deemed of special value, and public use and
appreciation of the site provide information that must be available for the assessment of impacts.
Potential aesthetic impacts include the loss of visually pleasing areas as ground is disturbed and
previous surface expressions are eliminated or damaged. Mines typically create significant noise
above the baseline conditions (from blasting, heavy equipment operation, materials/waste transport
and disposal, etc.). Mitigation measures to address aesthetic impacts involve siting of mine features,
as well as facility design and mining practices.
4.5 SEDIMENTATION/EROSION
Because of the large area of land that is disturbed by mining operations and the large quantities of
earthen materials exposed at sites, erosion is frequently of primary concern at coal and hardrock
mining sites. Erosion control must be considered from the beginning of operations through
completion of reclamation. Erosion may cause significant loadings of sediments (and any entrained
chemical pollutants) to nearby streams, especially during severe storm events, as well as high
snowmelt periods.
Major sources of erosion/sediment loadings at mining sites can include:
• Open pit areas
• Heap and dump leaches
• Waste rock and overburden piles
• Tailings piles
• Haul roads and access roads
• Ore stockpiles .
• Vehicle and equipment maintenance areas
• Exploration areas
• Reclamation areas.
The variability hi natural site conditions (e.g., geology, vegetation, topography, climate, and
proximity to and characteristics of surface waters) combined with significant differences in the
quantities and characteristics of exposed materials at mines preclude any generalization of the
quantities and characteristics of sediment loadings. Further, new sources are frequently located in
areas with other active operations as well as historic mines (left in an unreclaimed state). There may
4-55 September 1994
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Environmental Issues EIA Guidelines for Mining
also be many other non-mining sources of erosions in the watershed (other types of industrial
operations, naturally unstable areas, soil conditions, etc.). Therefore, in considering the erosion
effects ftom a new mining source, the cumulative impacts of sediment loadings from all sources
• within a watershed need to be considered. An important element of this analysis is the potential for •
the new source to alter downstream .flow conditions and thereby alter rontribjitions from downstream
sediment sources. . .
ifThe foggwjng subsections describe: (l)'the basic principles of erosion, (2) the impacts associated
with ...... erosion/runoff (i.e., the physical/chemical effects on the watershed), (3) approaches to
^ basdine conditions, (4) methodologies to determine the sedunent <»ntnbjtigns,frj>m a
.^ ,
::=^^
and ^treatment feghnnlfigies).
4.5.1" BASIC J&OSION PRINCIPLES
Water erosion ...may be described as the process by which soil particles are detached, suspended, and
..... source ...... of origin. Sedimentation may be described as the by-product of
-
whereby eroded pgies gj-g deposted a jratt ocation than mg S0urce of origin. Soil
[[[ ,1- ...................................... I, ......................... ± [[[ i ........................... i ........................ s [[[ ; ........................................... i ...... ; [[[ i ........ , ....................... . .......... i .................................................. .,- ............................... . .......... .............................. o
[oetadnnent ..... results ...... from ...... thejsneigy ...... tfnundrops striking the soil surface or it results from suspension
Erosion ................ " ..... ..... ........... '"
occup from the movement of water in sheet flow, in rills or gullies of ephemeral waterways, or
through channel erosion in ditches and streams. Wind erosion occurs when wind energy exceeds the
SfMlttV /\T O/\ll tf\ f*TTlf»?-n /*/\VkAC***r^ «i«t«] +)«A ««M«*«MlAn 1& «««.**. A. J«*AA^._^> T-_i-._1I __ __ ! __ i ____ •__ •_ _
™t*fcJIiS (Qfsott to remain cohesive aad the particles become detached. Typically, wind erosion is a
. problem in arid climates.
i
> influencing erosion and sedimentation are interrelated and all relate to either the impact of
or runoff velocity and volume. Sedimentation is considered the final stage in the erosion
process, thus the mechanisms affecting erosion also affect sedimentation. .The main factors
influencing erosion include:
*
i
Rainfali/Snowrndt ganoff,, The volume and velocity of runoff from storm events are
dctennined by the rainfall intensity and the duration i of .the rainfall event. A more intense
stonnlpplies greater forces which results hi greater displacement of soils; storms of longer
duration naturally produce more runoff, and thus greater erosion. Runoff also occurs
*u?1? 22222S!!, E®55ds_ (552* Y.5I5I15 .?Sd.y
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EIA Guidelines for Mining Environmental Issues
• Soil Texture and Structure. Soil texture describes the percentage composition sand, silt,
and clay particles in a soil. Soil structure generally refers to the aggregation of soil
particles. Sand particles are heavier, and disregarding aggregation are generally less
susceptible to transport than are. silt particles. Soils with high clay content are also less
susceptible to erosion because the particles tend to stick together. Soils high in silt content,
on the other hand, unless well aggregated, are the most erodible soils. The structure will
influence the erodability of each type of soil. Well aggregated soils are less likely to,
detach. Runoff or airflow over these soils however may be increased, due to
impermeability and-thus reduced infiltration. The relationships between soils type and
structure and potential water erosion are well known, yet complex. (Similar principles
apply to water erosion of waste/materials management units.)
• Vegetative Cover. Vegetative coyer influences erosion by:
Reducing the rainfall or wind energy striking the soil's surface
Lowering the velocity of overland and channel flow which:
— ' Reduces peak runoff rates and resultant impacts of channel erosion, and
— Decreases the velocity of overland flow, enabling sediment deposition to occur
closer to the original site
— Providing roots to hold the soil in place.
Because vegetation acts in multiple facets, the relationship between vegetation and erosion is
dramatic.. This is perhaps best illustrated through curve numbers. Curve numbers are used
in the U.S. Geological Survey soil-cover complex method for estimating rainfall runoff and
are an estimate of the percentage of rainfall runoff that will occur. The curve numbers for
forested land of varying soil conditions range from 25 to 83, meaning that forested lands
will produce from 25 to 83 percent runoff.. In comparison, the curve numbers for a
denuded construction site of varying soil conditions, range from 77 to 94.
• Slope length. The term "slope length" is defined as the distance from the point of origin
of overland flow to the defined point of interest, which may be a channel, or the point
where deposition begins. Longer sloped surfaces result hi higher runoff velocities for the
particular segment. '
• Erosion Control Practices in Place. Various practices and structures can be employed to
reduce the effects of land disturbances and developments: Erosion control practices work
by one or more of the following mechanisms: • ,
Reducing the impact of raindrops
Reducing the runoff volume and velocity
Increasing the soils resistance to erosion.
Specific erosion control BMPs applicable to mining sites, are described in Section 4.5.5
below-
4.57 September 1994
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jnilrnnmental Issues EIA Guidelines for Mining
4.5.2 IMPACTS ASSOCIATED WTIH EROSION/RUNOFF FROM DISTURBED AREAS
Paniculate matter is toxic to fish. Decreased densities of jnacroinver|ebia|e and benthic invertebrate
populations have been associated with increased suspended solids. Enhanced sedimentation within
aquatic environments also has the effect of inhibiting spawning and the development offish eggs and
larvae, as well as smothering benthic fauna. In addition, high turbidity may impair the passage of
light, which is necessary for photosynthetic activity of aquatic plants.
i ,
" . HI I Illlllllllllllllllllllll II II HI I 111 Illlllllllllllllll Illllll I Illlllll III PIIII 111111 111 III 111 111 111 I III UIHl 111 III I II IIII II Illllll 1111 III IIII I 111 I 111 1 1 11 III II
Further, exposed materials from mining operations (mine workings, wastes, contaminated soils, etc.)
may contribute sediments with chemical pollutants, including heavy metals. Contaminated sediments
in surface water may pose risks to human health and the ..... environment ...... as ...... ^ persistent source of
...... Bi ...... ..... SSl ..... m^3^ Iife' ,Human exposure occurs through direct contact, eating fish/
w ° contaminated
, ,,,
sediments. Continued bioaccumulation of toxic pollutants hi aquatic species may limit their use for
human consumption. Accumulation in aquatic organisms, particularly benthic specifies, can also
causej acute and chronic toxicjty to aquatic life. Finally, organic-laden solids have the effect of
reducing dissolved oxygen ..... concentration, ....... thus ..... creating toxic conditions.. There areno National,,
sediment criteria for the toxic pollutants likely to be released from mining sites, although criteria for
metals are currently under development and some States have established sediment standards.
..... impacts ...... on ..... human ...... and ..... aquatic life, mere are physical in^iacts
lil ...... gfeJRSJJassd ...... SSnpivejocities ..... and ..... volumes from new land disturbance activities.
SliiSii ...... ml ..... Hiiiili ....... ..... JBSaaasa& ..... flooding, scouring of stream channels, and
itfilc tural damage to bridge footings and culvert entries.
A characterization ...... of background conditions within a stream .is necessary 'to assess the potential
== ...... ^^^^^^^m^^^ ................ A£ ..... iSPO!!??! ....... element in assessing baselme stream
S5 ...... S^-felS?!^,!31?!!!*^ 2f ^ ,S!F,eam- 1E4, (1989b) has suggested
stream parameters be characterized at each stream sampling station in the
"
SUSHIS tond use- A description of the predominant types of land use is
land uses may also potentially affect water quality.
PB ' l!'iKB18fi!'SMiil'!l!f!H
SaaSSs 4 ZHSl estimate of erosion can be made by observing the'
SEfSSS SPii the, stream characteristics (both channel characteristics and
sediment loads). •
• Estimated stream width. A representative transect should be measured from shore to
shore to provide an estimate of stream width.
4-58 September 1994
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EIA Guidelines for Mining Environmental Issues
• Estimated stream depth. Stream depth should be determined for three habitat types: riffle,
run and pool. Measure.the vertical distance from the water surface to stream bottom.
• High water mark. Measure the vertical distance from the bank to the peak overflow level.
The peak overflow level may be indicated Toy debris hanging in bank or fioodplain
vegetation or deposition of silt or clay.
• Velocity. Stream velocity should be estimated in a representative stretch of the stream.
• Dam/obstacles to flow present. The presence of a dam upstream or downstream of the
stream segment under study should be noted. Also, any other impediments to flow or
sediment transport should be noted. How the dam or obstacles affect flow should be noted.
• Channelization. Describe whether the .stream is channelized at any point along the stretch
of stream under study.
• Canopy cover. A description of the percentage of shaded area at each sampling station
along me stream should be provided.
• Sediment odors. Any odors emanating from the disturbed sediment should be noted.
• ' Sediment oils. A visual estimate of the proportion of any oils in the sediment should be
noted. .
•• Sediment deposits. A description of the type of deposits present in the stream (sand,
sludge, organic material, etc) and any blackened undersides of rocks (indicates low
' dissolved oxygen or anaerobic conditions).
* Inorganic substrate components. A visual estimation should be made of the percentage of
inorganic substrate components present.
• Organic substrate components. A visual estimation should be made of the percentage of
organic substrate components present.
This method for evaluating the physical condition of a stream can be made more rigorous by
including quantitative evaluations of sediment transport. A quantitative evaluation of sediment
transport may be more suited for areas where significant disturbances already exist and more rigorous
documentation and understanding of the baseline conditions is necessary. Quantitative measurements
may be made of suspended and bedload sediment in the stream, as well as measurements of sediment
deposits (sediment .bars, substrate, etc.) and turbidity (turbidity measures the ability of a fluid to
transmit light). These data provide a rough estimate of the concentration of suspended sediments hi
water. A quantitative baseline measurement may also be made of the stream channel throughout the
area of impact.
The sampling of suspended sediment can provide information on the physical and chemical
characteristics of the sediment hi suspension. Depth-integrated sampling, as opposed to point
4.59 September 1994
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ll
Environmental Issues
EIA Guidelines for Mining
if . " ,'ii !" ""''i • ' . "" ,' • .. i I ' • ,
sediment and adsorbed constituents (USGS, 1977). Depth-integrated sampling involves the use of a
depth-integrated sampler that is lowered/raised throughout the depth of the stream at a constant speed.
'I ''" ' '' "' T"||l!l!|" ' ' ' i r
If the depth-integrated sampler is also used to sample across a stream transect, the concentration of
I) ii
suspended sediment obtained can be multiplied by the water discharge through the sample zone and a
\ i A ( i i ; . i , .1 v
total suspended sediment discharge can be obtained (USGS, 1977). Consequently, to provide an
accurate measurement of suspended sediment loads hi a stream, samples should be collected near
stream gauging stations.
Sample site selection should take into account the following preferences: located near a stream
|i i i i i » ' ' ~ i i
gauging station, located away from any flow distorting obstacles, and far enough either upstream or
downstream of confluences to prevent the hydraulic variances that exist in those zones (USGS, 1977).
Frequency of sampling should be determined by the known historical streamflow or precipitation
records, at a minimum, the stream should be sampled at periods of annual low and high flow.
I i " I In
• Illllll 11 1111 111 111 ill 111 111 111 11 111 ll III II 111 IIIIIIII 111 I III II 111 III I I 111 I II III 111 I 111 Illlllllllllllllllllllllllllllllllll III III Illllllllllll III III Illllll 111 lllllll 'I II I HIM ll 111 I I III 1 111 I I
II i i r | i
Sampling of the deposited sediment in the streambed can provide a wide range of information
including the type of sediment available for transport, mineralogy of the sediments, stratigraphy, and
amounts and distribution of contaminants (USGS, 1977). Sampling methods are available for
collecting disturbed or undisturbed samples. For the purposes of baseline sampling for a mining
project, an undisturbed sample may not be necessary. .
In addition to a physical characterization of the stream, a habitat assessment should be conducted to
determine the baseline conditions of the stream's ability to support aquatic life. The parameters to be
assessed represent measurements/observations of substrate and instream raver, channel morphology
and riparian and bank structure. EPA (1989b) has identified the following parameters for evaluating
the baseline conditions of stream habitat. .
Bottom substrate/available cover. A visual observation of the ability of the bottom
substrate to provide niches for aquatic life should be madeT
Embeddedness. Embeddedness refers to the percentage of fines surrounding large size
(boulders, rubble or gravel) particles.
Stream Jlpj?/sjream ydoqfty. The volume and velocity of stream flow should be evaluated
resj>ect to optimal conditions for aquatic life.
i Chaindl alteration. An observation of growth or establishment of sediment bars or other
___ — changes hi upstream erosion. The development of channelization
.ihojjld ilso, benoted,.
September 1994
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EIA Guidelines for Mining Environmental Issues
• Bottom scouring and deposition. An observation should foe made of the degree to which
the substrate is scoured and the amount of siltation in riffles and pools. This observation is
typically reported as a percentage of the observed stretch that is scoured or silted. Bottom
scouring and deposition result from sediment transport and may provide an indication of
watershed erosion.
• Pool/riffle or run/bend ratio. This ratio is calculated by dividing the average distance
between riffles or bends by the average stream width. This parameter assumes that the
higher proportion of riffles and bends provides more diverse habitat than a straight or
uniform depth stream.
• Bank stability. Bank stability is typically determined by the steepness of the bank and any
observed erosion into the stream. Steeper banks generally indicate poor quality instream
habitat due to mere susceptibility to erosion, however, stream banks of clay may not be as
susceptible to erosion as stream banks composed of other sediment.
• Bank vegetative/rock stability. Bank stability may also be estimated by the type and
amount of vegetation and rock cover present. Proportions of shrub, trees, grasses and
rocks providing bank cover should be estimated.
• Streamside cover. An estimate of the primary type of vegetation that is providing
• streamside cover should be made It should also be noted if no cover is provided.
The above information on the sediment and habitat quality should be considered in conjunction with
baseline studies of aquatic organisms within the watershed (including fish count, macroinvertebrates,
etc.). The combined data will allow the reviewer to correlate background aquatic life conditions to
sediment quality.
4.5.4 PREDICTING SEDIMENT LOADINGS FROM NEW SOURCES
There are currently several approaches/models available to assist in the prediction of sediment losses
and flow responses of basins both before and after landscape alterations due to mining and other
human activities. As with any models, they are highly sensitive to the input data supplied and caution
must be used in identifying and quantifying the important factors for a specific project.
The primary factors affecting basin sediment yields are:
• Precipitation. Volume, intensity, and duration are all important
• Vegetation. Vegetation increases the ability of hillslopes to retain overland flow, increase
infiltration, and reduce the velocity of overland flow
• Basin size. Basin size controls the lagtime between the beginning of the storm event and
the time of peak flow
4-61 September 1994
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Environmental Issues
El A dlirlelinpc fnr IVTini
ijjjBT,,,., •'!,,,- 1 « i ' it ;:: ' ....... »
! 'iilE 'i !! « ' Li, " ....... Hr , ........ i :«]!!!:", iii,i - 'I!!!1!11:,, i, ift,1! ..... ¥ ' '
aS i ! I|lli||fil iil ffiliik IUPS With steeper overall slopes will have higher overland flow
"~x?cities and quicker response times to storm events
SoM/rock type. Different soil types have varying degrees of erodability, infiltration
=^g>=g2=»~i»;,;jdellng basin hydrology can take forms varying in complexity from "back of the envelope"
calculations to cojnputer-based, multivariate modeling based on data from comprehensive field
investigations. Most modeling, of any level of complexity, is based on several basic equations
developed specifically to predict soil losses from known bashi characteristics. These equations
include: the Universal Soil Loss Equation (USLE), the Modified USLJE'"(MUSLE), and the Revised
USLE (RUSLE). These equations are dcsaSbedbdaw. : \ '. '
The Universal Soil Loss Equation (USLE)
I " i ! " ' • i "
The USLE has been developed utilizing data gathered at a large number of experimental sites. The
equation utilizes six hydrologic variables to |enerate predictions of .annual total soil loss in tons per
i*^^ £S2 ifSSlS ISlS; SHS 2l, IE SSE^P-B. ^F^68 are determined lay comparing site'
5c observations, of bashi characteristics to published graphs and tables to determine the
of the
...... yfto£. ............. The ..... U.S. ........ Soil ...... ComgrattaSovite ..... pribUdies
SIS? ....... 2!S£S ..... ,l2Xg,i,ISffl4Sy£!PI^ .fr0111 numerous studies of bashi characteristics: ..... ma number ...... of
climates.
The tTSLE is written:
iiiiiini
Where A is the total soil loss in tons per acre per year, R is the rainfall erosivity index, K is the soil
erodabflity index, LS is the length-slope steepness factor, C is the cropping management factor, and P
is the erosion control practice factor. An increase of any of these factors will result hi increases hi
the total predicted soil losses for an area.
The Modified Universal Soil Loss Equation (MUSLE)
I ' i i I i
The MUSLE equation is written hi final form identically to the USLE. It varies from its predecessor
in the introduction pf an exponential function for the deterrnination of the length-slope factor (LS).
The T^— t?I^2°- 5?! ,!^n. **E!EL !°, ,'w,?,!l ™* PS, 51PP?? HP to 15 to 20 percent but on steeper
slopes prediclions of erosion become much greater than those actually observed. The R-factor is also
' ,11 .in ,„ n
i••• i^ iiiii ITmiitu iiiiiiiirinMUM ifiiiiii < 11I1111 'iiiiiiiiiiiii " uiiiiiiiiiipiiiiiiiiiiiiiiiiii1 iiiiiiiiiii,, i • ' TK
1 4-62
September 1994
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EIA Guidelines for Mining Environmental Issues
changed and,is now a product of the total per-acre runoff volume and the maximum rainfall intensity
for a given storm.
MUSLE also improved its predecessor by allowing predictions of soil losses for single storm events.
This is important because allows for the examination of losses during peak conditions which may
account for a large percentage of total annual losses.
The Revised Universal.Soil Loss Equation (RUSLE)
RUSLE takes the same basic form as both the USLE and MUSLE. However, the RUSLE improves
upon both previous incarnations by using several LS functions to model slopes of different steepness.
Of the three approaches, RUSLE works best for steep basins (slopes greater than 20 percent).
Other Son Loss Equations
Several other soil loss prediction models have been developed that are based less on standardized
tables of factors and equations but are instead theoretically based. These models are, important in that
they allow for the testing of hypotheses on the physics of hillslope hydrology. However, to date, they
have not yet been shown to be accurate predictors of total sediment losses and so remain more
theoretical than practical. '"..-..
Computer Models
A number of computer models are available which utilize variations of the USLE and other soil loss
equations to perform automated analysis of soil losses from basins. These models are available from
commercial, governmental, and academic sources. The most sophisticated of these allow for the
subdividing of larger basins into smaller sub-basins and utilize routing functions to predict the
response to the same storm of sub-basin areas which may have very different soil, vegetative and
land-use conditions.
4.5.4.2 Modeling Considerations
In. the use of any of the above modeling schemes, the accurate determination of current and potential
site conditions is vital to generating, accurate results. In some cases, what seem to be fairly small
variations in site conditions can make great differences hi predicted soil losses. For example, the
cropping management factor, C, can vary by a factor of 3 with a change hi vegetative cover of 20
percent (U.S. Soil Conservation Service, 1975). Under- or over-estimating canopy cover by 20
percent will produce a 300 percent variation hi the predicted soil loss.
Great importance should be placed on the accurate determination of the conditions within the basin.
It is possible, and not too uncommon, to approximate values for some factors without actually visiting
4.53 September 1994
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Environmental Issues • . EIA Guidelines for Mining
i > i „ i
a sice. The SoU Conservation Service has made available tables and maps which provide probable s
ranges of values for various site conditions. However, since the strength of a model depends on .the
strength of input data, final determination of the factors to be used in a model should be based upon
ions made on site. Some important factors affecting'soil erodability, such as the presence of
thick leaf litter on a forest floor, are.not ^terminable from aerial photos or maps. Any modeling
performed without actual site observation should be considered a first approximation.
{' " , , . ' ' , •',,,,'' , !,"
The final step in any modeling is verification. A model should not be considered to have predictive
I ! | > ! L „' ' 1 ! «""" - -!" ' '. • '• !!'".'!',. , I! | '.',i .;:" !'!"':.' '.',! *,,
power for hypothetical conditions until its ability to accurately model known conditions has been ••
. * This means comparing actual measurements of soil losses with those predicted by the model.
A great disparity between these two values indicates the need to examine either assumptions of the
model or the, field measurement techniques.
The Dejection ofstonn events foruse |n modeling predictions should also be carefully considered.
Since both intensity .aid duration affect the generation of overland 'flow, both short duration/high
intensity storms and long duration/moderate intensity storms should be considered. Also, antecedent
conditions at a site may be important. High intensity storms win produce iigher peak flows and
Sjijter erosion ratw tf Jhey_ fell, on already saturated,'frozen, and/or snow covered soils.
results .should allow die operator to quantify the impacts of the proposed land
...... ISlSESS ....... ojflosses ..... 2!,Si Eel 15!! §£?*„ and 'total solids
loadings). However, available methodologies do not address deposition of generated sediments in
'there are no specific criteria to determine what level of increased TSS
concentrations, turbidity, or total sediment loadings constitutes a significant impact. To a large
this is subject to best professional judgment (in consideration of die baseline watershed
ro|djtions as djscasse£iab£ye). Similarly, BPJ is necessary to assess how any toxic jrolhitants
associated with solids loadings could affect sediment quality, and this should-always be considered.
Faoors to^nsidCT include: potential sources of toxic pollutants, existing sediment ualit, an
\ available data on the affects of similar operations/land disturbance within the watershed (where
^Ijj^licaole^ aid mTnatureTdeslgnated uses ofihe receiving ^^ •
j^nvpOTAM&PsjpNMITIGATIONMEASURES
Sediment and a^jon^njitigtion measures are used to reduce the amount o^materials earned og^sitg
and deposited jn a receiving stream. To meet this objective, mine operators should consider methods
»' '" to limit runon, mjnimige^tfae areas ^disturbed soil (exposed to precipitation), reduce runoff velocity,
and remove sediment from.on-site runoff before it leaves die site. In many cases, a range of different
BM^/sediment ancj^ gosion co^rolg arg.used gncurrentl^ a£ mine sites. The three main gategpries
of sediment and erosion controls are: diversion techniques, stabilization practices, and structural
controls. The following subsections briefly describe each of diese categories.
I iililil -
4-64 September 1994
lllllll Illlllllllllllllllllllll 111 llllll|lll|ll IIIIIIIIIH I lllllll 111 III I"! IIIIIIIP lllllll 111 II III 111 I III'111 III 111 111 HI I 111 III I II III IN Illlllllllllllllllllllll lllllll III1! I III llllllllllllll 1111 Illlllllllllllllllllllll lllllll I ll I ill lllllll 111 i|il| I Illlllllllllllllllllllll Illllllll
' I !
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~E3A Guidelines for Mining Environmental Issues
4.5.5.1 Diversion Techniques
Diversion techniques are measures that prevent run-on, precipitation, and other flows from crossing
areas where there is a risk of significant erosion. Diversion practices often use on-site materials, and
take advantage of on-site topographic, vegetative, and hydrologic factors to divert flows away from
disturbed areas/soils. Typical diversion practices used at mine sites include: interceptor dikes and
swales; diversion dikes, curbs and berms; pipe slope drains; subsurface drams; and drainage/storm
water conveyance systems .(channels, or gutters; open top box culverts, and waterbars; rolling dips and
road sloping; roadway surface water deflectors; culverts).
4.5.5.2 Stabilization Practices.
Stabilization, as discussed here, refers to covering or maintaining an existing cover over soils. The
cover may be vegetation, such as grass, trees, vines, or shrubs. Stabilization measures can also
include nonvegetative controls such as geotextiles (matting, netting or blankets), mulches, riprap,
gabions (wire mesh boxes filled with rock), and retaining walls. These stabilization practices act to
prevent or minimize erosion by holding soil in place, shielding it from the impact of
precipitation/showmelt, and increase surface contours to slow runoff velocity.
The establishment and maintenance of vegetation is one of the most important factors in preventing
erosion. Vegetative controls are often the most important .measures taken to prevent off-site sediment
movement, and can provide a six-fold reduction in the discharge of suspended sediment levels. In
addition, these practices can enhance habitat values and the appearance of a site. Examples of
vegetative practices include temporary or. permanent seeding, vegetative buffer strips and protection of
.trees. Nonvegetative stabilization practices can be used as a temporary or permanent erosion
prevention measure. These controls can be used hi order to aid in establishing vegetation or as stand
alone practices. ' .
Vegetative controls are low cost and require low or no maintenance once a ground cover has been
established. However, prior to the establishment of a vegetative cover, considerable site preparation
may be necessary such as contouring of disturbed areas, placement of tbpsoil on barren areas, soil
conditioning (e.g., with municipal sewage sludge), or spraying areas with fertilizers.
Contouring refers to a number of practices including recontouring, regrading, reshaping, and surface
roughening. Contouring of waste piles will provide a number of benefits, including aiding hi the
reduction of storm water and run-on velocities, assisting in the establishment of a permanent
vegetative cover, and improving site aesthetics. Specifically, reducing the height and steepness of a
slope can greatly reduce erosion and sedimentation at a site.
4-65 September 1994
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Environmental Issues
EIA Guidelines for .Mining
i iii iiiiii
inhere recontouring wastes is not practical due to geographic or resource considerations, reshaping of
1111111111 wasS may" be a viabie option. Reshaping BMPs refer to the rearranging of waste piles and exposed
ig/benching), moving waste piles out
I
areas in such a wajr as to reduce the steepness of sloges
of speambeds or other highly credible areas, and other methods to reduce nates andstonn water
velocities over and around areas susceptible to erosion.
II n in in i| inn 111 in n in ill
Ill After an area has been recontoured or reshaped, surface roughening may be employed to further
i ijiiiiiiiiiiii inn I SB * ; * " " <
reduce nmpff.yelqcjty^and promote infiltration, as well as supporting revegetation. A rough soil
surface is amenable to reyegetation, through creation of horizontal grooves, depressions, and/or
terraces that parallel the contour of the land.
4.5.53 Structural Practices
III 111 Hi in I III i II ill III i
* " 'II
Structural controls involve the installation of devices to store flow or limit runoff velocity. Structural
practices can be used to remove sediment from runoff before the runoff leaves the site. Approaches
II II f I *^-; |!
to removing sediment from site runoff include diverting flows to a trapping or storage device or
filtering diffuse flow througjisflt fences before it reaches the receiving water. These methods are .
designed to slow the flow of water discharged from a site; resulting in the settling of solids and the
limiting of downstream erosion. Structural controls also promote infiltration.
i . •
StruGtoral sediment and erosion control practices are typically low in cost. However, structural
practices require periodic maintenance (including sediment removal) to remain functional. As such,
they serve as more active-type practices which may not be appropriate for permanent use at inactive
mines. However, these practices may be effectively used as temporary measures during active
operation and/or prior to the implementation of permanent measures.
Some examples of structural practices include: settling ponds/detention basins, check dams, rock
outlet protection, level spreaders, gradient terraces, straw bale barriers, silt fences, gravel or stone
filter If1™3' brusb; baf^|eis' sediment traps, grass swales, pipe slope drains, earth dikes, and other
controls such as entrance stabilization, waterway crossings or wind breaks.
i i • ii I i i
i » • .
In some cases, the elimination of a pollution source through capping sources of erosion may be the
most ..... pst ...... ejffiKjtive^control ...... measure, ...... for. ...... sediment, ...... discharges and other pollutants. Depending on the
type of management practices chosen, the cost to eliminate the pollutant source may be very high.
Once completed, however, maintenance costs will range from low to nonexistent.
4.5.5.4 Contact Prevention Measures/Reclamation Practices
| ' ' " ' '
Permanent reclamation, as discussed here, refers to covering or maintaining an existing cover over
disturbed areas. The cover may consist of grass, trees, vines, shrubs, bark, mulch and/or straw.
. 4-66 September 1994
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. EIA Guidelines for Mining . • • • Environmental Issues
Ultimately, revegetation involves establishing a sustainable ground cover at a site through permanent
seeding, mulching, sodding, and other such practices.
The establishment and maintenance of vegetation is one of the most important factors in minimizing
erosion. A vegetative cover reduces the potential for erosion of a site by: absorbing the kinetic
energy of raindrops which would otherwise impact soil; intercepting water so it can infiltrate into the
ground instead of running off; and by slowing the velocity of runoff to promote onsite deposition of
sediment. Vegetative controls are often the most important measures taken to prevent offsite sediment
movement, and can provide a six-fold reduction in the discharge of suspended sediment levels. In
addition, these practices can enhance the habitat and aesthetic values of a site.
Typically, the costs of vegetative controls are low relative to other discharge mitigation practices.
Given the limited capacity to accept large volumes of runoff, and potential erosion problems
associated with large concentrated flows, vegetative controls should typically be used in combination
.with other management practices. These measures are universally considered to be nearly always
appropriate for mining sites, as evidenced by their being required by ail States that require
reclamation of closing coal and non-coal sites.
As noted above, vegetative controls are low cost and require low or no maintenance once a ground
cover has been established. However, prior to the establishment of a vegetative cover, considerable
site preparation may be necessary such as contouring of disturbed areas, placement of topsoil on
barren areas, and the spraying of areas with fertilizers. Further, predicting the likely success of
reclamation practices at mine sites has often proven difficult. Where reclamation/revegetation is a
key element of long-term erosion control, the operator should consider establishing representative test
plots to increase the likelihood of success.
Contouring
Prior to the establishment of vegetation, surface contouring is often required. Contouring refers to a.
number of practices including recontouring, reshaping, and surface roughening.
Recontouring waste piles/disturbed areas at a site will provide a number of benefits. Recontouring
wastes or disturbed areas to match the original land contours of a site will aid in the reduction of
storm water and ran-on velocities, assist in the establishment of a permanent vegetative cover, and
improve site aesthetics. Reducing the height and steepness of a slope, combined with other diversion
BMPs discussed above, can greatly reduce erosion and sedimentation at a site. This practice is also
often times necessary to establish a vegetative cover over exposed materials.
Where recontouring wastes is not practical due to geographic or resource considerations, reshaping of
wastes may be a viable option. Reshaping refers to the rearranging of waste piles and exposed areas
4-67 September 1994
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•••^^ iiiiiiiiiiii iiiiiii iiiiiiiiH^ mi 11 ii mi 11 in iiiii i in i iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii • mi i iiiiiiiiiii in ill 11 11 nil i i in 111 MI i mi in 11 ill mi i iiiiiii||i|i 11 |ii in 11 i in i in iiiiiii
Environmental Issues ' EIA Guidelines for Mining
in such a way as to reduce the steepness of slopes (terracing/benching) and other methods to reduce
rmi-on and storm water velocities over and around areas susceptible to erosion.
After an area has been recontoured or reshaped, surface roughening may be employed to aid in the
establishment of vegetation. A rough soil surface is amenable to revegetation, through creating
I tejgfijSS grooves, degressions, or steps.that run with the contour of the land. Slopes may also' be
left in a roughened condition to reduce discharge flow and promote infiltration.
. - , J, • : " • , '"'.'.
roughening aids in the establishment of vegetative cover by reducing runoff velocity and
seed an opportunity to take hold and grow. Increased vegetative cover, in turn, provides
•ation and sediment trapping, farther decreasing runoff velocity and erosion.
techniques are appropriate for all slopes steeper than 3:1 in order to facilitate stabilization of
9? ? yfS?!3*!}^ PPYer. .Pncfrareas have been,,,,con|oured, they'
-
Topsoiling ' • ,
•H ilUIEII^^ 111, Illlllilllllllllll lllliillllllll Iii!!', III! 1 liillll 1 IlililH^ HI ,. II ll'l'lli II1 ' lllliillllllll IlllllW^^^ lilllliillilill'lllilili'i Win^^ IIP!1 II IIIIIII IT I ••illH 1" I I nflll! i Iiiii1 "linlili liillll 111!! llllhil II Nil
may be necessary to improve,- provide, or preserve the area on which a permanent
_ _ *_ ____,_^ ifa^ practices ^ ^ ^^J £OD& tQ pjovjdg erosion' control,
[[[ i [[[ ii [[[ * , ........ , , ™
...... ^ ........................... il [[[ Mjj.. [[[ i ......................................... [[[ i [[[ ii [[[ , ........ , ,
1*9? :,«re an mtejral part of establishing vegetative controls. Conditioning may be required where soil
& oCpoor quaUty. More resource intensive topsoiMng measures may be needed where soils are
....... where ..... the ..... need to ..... quickljr ...... establish^ vegetatira is paramount, where tbe
....... Snt5n| ..... maieriS ...... trade ..... to plant g^^ (i-e^ acidic sofl ^jj -^
: the soil rooting zone is not deep enough to support plants.
liillll1 llh Ililliililliiii 41
_ S_22!21 23 ,S£!2J!e, *£ W* ?f fertilizers, or less ejq)ensive-measures such as the land
• SliSiSSiJSlS!, 22S Si!?80' Usm£ toPs°a n^y require the importing of soils from an
alternate location or the use of soil from a nearby site.
soSSfSfers^or topsoil, measures must be put hi place to prevent washouts prior
***$*& of this practice should be coordinated with seeding and
I g22iSi 52 £2 S2 22 £S Performed immediately after soil conditioning or topsoiling is
ed. Additionally, it is necessary to provide measures such as mulching or diversion which
prevent erosion of the topsoil or conditioned soil. These practices should be coordinated with seeding
and planting practices so that they can be performed immediately after conditioning or topsoiling. .
i
"
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EL4 Guidelines for Mining Environmental Issues
Seeding
The establishment of plant life stabilizes soils and helps to reduce sediment in runoff from a site. In
addition, vegetation filters sediments, maintains the soil's capacity to absorb water, improves wildlife
habitats, and enhances site aesthetics.
Seeding and planting are appropriate for any disturbed area mat is subject to erosion. This practice is
particularly effective in areas where soils are unstable due to texture, structure, high water table,
and/or high slope such as those commonly found at inactive mining, landfill, and oil and gas sites.
Selection of appropriate vegetation, good seed bed preparation, timing, and maintenance are needed to
ensure the success of this practice. Selection of native species will increase the chances for success
and may lessen future maintenance requirements.
Capping of Wastes/Materials
Capping/sealing of wastes/materials (including surface mine workings, tailings and waste rock) is
designed to limit or eliminate contact between runoff and potential sources of sediment/toxic pollutant
loadings. The use .of this practice depends on the level of control desired, the materials available, and
cost considerations. Many common types of caps may be effective including soil, clay, and/or
synthetic materials. Generally, soil caps will provide appreciable control for the lowest cost. Any
type of cap may be covered with up to several feet of rock and soil and revegetated.
4.5.5.5 Treatment Techniques .
Discharge detention structures can achieve a high removal rate of sediment and metals, such as those
which may be expected to be discharged from inactive mining operations. Complemented by ease in
construction and simple operations and maintenance, the use of detention structures desirable as a
treatment mechanism for discharges from inactive mines and landfills. Site characteristics must be.
such that discharges can practically be channeled to a centralized area for treatment.
Detention basins are most cost-effective at larger sites. In addition to their pollutant treatment
capacity, detention ponds can also create wildlife habitat, recreational, and landscaping benefits.
Even at larger sites, however, hydrologic and topographic factors, as well as inaccessibility and cost,
may limit their utility.
4.6 METALS AND DISSOLVED POLLUTANTS
Dissolved pollutants (primarily metals, sulfates, and nitrates) can migrate from mining operations to
local ground and surface water. While ARD can enhance contaminant mobility by promoting
leaching from exposed wastes and mine structures (see Section 4.1), releases can also occur under
4.59 September 1994
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Environmental Issues
EIA Guidelines for Mining
pH
s. Primary sources of dissolved poUutants from coal and metal mining operations
J ...* d^S^aceimne workings; overburden and waste rock pUes; tailings piles and
impoundments; direct discharges from conventional^inilling^eneficiatiQn operations; leach piles and
processing faeiliaesj coal processing units; chemical storage areas (runoff and spiUs); and reclamation
actiymes. Discharges of process water, mine water, runoff, and seepage are the primary transport
; to surface watei- and groundwater.
:- 1= I ,
One potential
?*!?§* » chemicals used in mining and beneficiation. Common
" ^ogriuoi,cyanide, nitrate and phenolic compounds, along
-"T*«-T -»-Perations. With the exception ofteaching operations and
:iSli Si II rfsfeo&Saaeqoafc in blasting and reclamation, the quantities of reagents
** ***W ^ Con9)ared to ** volumes of water generated. 'As a result, the risks from releases
DOlllltanf frnm nnn-1p*>r>hinCT_ra1a+asf «»•>»<...*.. ti «••...,_.
(see Sections 4.1 and 4.2
of toxic jjwUutant from
««««««««~ii|««««««u«««««
fo
, .
regents are generally .
[[[ *^ -- - — JP~ '"••*«***J ***!*•» W»* ^OWW OW%
...... of the potential impacts associated with acid and cyanide releases).
A major source of poUutants is naturaUy occurring substances in the ore: Mined ore not only
con**™* A* mfn^.1feeing extracted but varying concejaratioisof a wide range of other minerals
' iOPbegesentatmuch higher concentratipns and can be sigtiificantiy
^
»SBS 35«Sfi: Depending on the local geology, the ore (and the surrounding
on include trace levels of aluminum, arsenic, asbestos, cadmium '
£°PP«r. iron, lead, manganese, mercury, nickel, sUver, selenium, and zinc.
•
of specific poUutants, their release potential, and the associated risks are highly
facility-specific conditions, including: des'ign and operation of extraction and
"ons' waste:SSl SlSiiSli:=iiiiiagen^ practices, extent of treatment/mitigation
climate, geology, hydrogeology, waste and ore
—' ™- *-w * ^ ^— —-— £jj 9 **«AM»«r MII^I WA5
j^t*^**?*0*' ?te->.^JI9?«B °f and proximity to human and environmental
" development of the National effhient guidelines for me Ore Mirung and Dressing
^ 5°Sce categories (40 CFR Parts 434 and Part 440), EPA conducted sampling
PIII ............. , »
iff* 12 Identify poUutants of concern at mining operations (focusing primarily on
f^f Trr^+A* *»rf%*. ^^ v«__* *•-.-. '
-
....... SI ..... ............ ..... Mprovidesa summary of the metal pollutants
operations.
with discharges from specific types of hardrockMoiwoal mining operations
...... IP«ices). Exhibit 4-5 describes dissolved pollutants often found in
a presented in the tables were primarily obtained from sampling of mine
,Eastewatera WMh, the exception of coal and refuse pile runoff at
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EIA Guidelines for Mining
Environmental Issues
Exhibit 4-4. Typical Pollutants Associated With Hardrock Mining Operations
Type of Mining
Iron '
Copper, Lead, Zinc, Gold,
Silver, and Molybdenum
(excluding cyanide leaching
operations)
A iiifTf {(Vim
Tungsten
Mercury
Uranium
Antimony
Titanium
Vanadium
•Potential Pollutants of Concern in
Discharges to Surface and
- " Gnmndwater
Asbestos, arsenic, and copper, iron
Aluminum, antimony, arsenic
cadmium, chromium, copper, lead,
manganese,, nickel, thallium, and zinc
None found at high concentrations
Copper, lead, and zinc.
Most .toxic metals
Radium 226
Antimony, arsenic, and asbestos
Most toxic metals
Mercury, arsenic, ga^mmm
chromium, copper, mercury, lead
and zinc
Typical Treatment :
Sealing ponds and flocculation.
Recycling/reuse and
settling/precipitation ponds
Not Applicable
Recycle (mines have generally been
located in arid regions)
Evaporation ponds and/or
recycle/reuse
Evaporation; ion exchange;
flocculation; settling; and
recycle/reuse
Recycle/reuse
Settling and precipitation
(lime/caustic addition)
Neutralization, settling and
precipitation
Source: EPA, 1982; ore mining and dressing development document.
Further, they have historically not been subject to the same level of control/treatment as mine and
process wastewater.
In assessing the nature and extent of potential dissolved pollutant releases from new source raining
operation, reviewers can often supplement general information (such as the above tables) with site-
specific data. This wfll include information on local geology (focussing on the chemistry of each
geological unit and the likely composition of wastes/exposed materials). In addition, mining
operations are often located in historic mining districts. Where this is the case, significant existing
data may be available (or collected under baseline monitoring) to describe past releases to surface
water and groundwater, how they have affected me environment, and the effectiveness of current
treatment/control measures. It is not uncommon to find naturally occurring levels of metals and
sulfates (particularly iron and manganese) in highly mineralized ground and surface water. However,
rnining and land disturbance activities have the potential to increase the loadings and mobility of
specific pollutants.
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Environmental Issues
iilllllllfl!l!il|lllVll ..... Illlliiilii ' ill lllllin liillll ...... 111!! ...... Ill ..... llilii ...... ! ........ r [[[ i [[[ . .......
. _ EIA Guidelines for Mining
I HI 111 111 III IIH
Exhibit 4-5. Typical Pollutants Associated With Coal Mining Operations
';- , ;'.•'. ': V,
Wasfewaier Type
Coal preparation plan:
wastewater
Coal pile runoff •
Refuse pile runoff
Anralfjxf rnntf tfrajnage (see
Section 4.1 lor discussion
of acid mine drainage)
Potential PoDntants of Concmrin
. Discharges; to'Surface. and.:
'- *\ : • Groundwater
Arsenic, cadmium, copper, lead
silver, and zinc.
Manganese, iron, arsenic chromium
copper, lead, mercury, nickel,
selenium, and zinc
Copper, cadmium, .silver, and zinc
Iron ajvj Tnrmtjanese
F ' .
Typical Treatment
Settling and precipitation,
recycle/reuse
Neutralization and precipitation
Neutralization and precipitation
llllllltilllllllllllllllllllllllllllllllllll'HIIIIllllllllllllllin^ ..... Wwwh
Htow provides information on the acute and chronic impacts of dissolved
"Pollutants in surface water @r«luding suggested water quality standards). Each State has promulgated
-**{* quality criteria for surface waters based on the designated uses of the waters as well as
"" " ' ' '! " . "•
to apply the standards. Reviewers,should be cognizant that, unlike
operations ...... 2*1 ...... discharges, ....... there ...... can ...... be ...... extreme ....... variability in toxic
coriuent ..... oadngs from mining operations, both from day to day and over months and years.
™ ticrfarfy ..... sensitive ...... to ...... loadhigs of toxic pollutants during
4.1 and 4.5, ta$donal
and analyses-during these critical periods. _ As discussed,, m Sections,,
or
d
programs may not provide for sampling
jnost advene ,131)3018 on surface water quality.
utants discharged to surtace waters can partition to sediments. Specifically, some toxic
constituents (e.g., lead and mercury) 3550^^ ^J£ disdjajg^ '"^^ mining operations are often
found ^ f!22£! !5!S!$ ™ SSSESS.:, ,2Se, 12! SgSS detected^ in the, water column. Sediment
contamination may impact human health through consumption of fish that bioaccumulate toxic
poUlfaj11!: !!E!!S! flSS! !22!£ 2!,|°SE Po«utantsi in sediments can haye direc|^,,a"cute;and chronic
macromvertebrates and other aquatic life. Finally, sediment contamination provides a
, 222 ofpogutante trough |wtential redjssolutipn in the water colurnn, As note^ in
SectiPn 4,:5i §S| SS SSI^y "o national sediment standards/criteria for toxic pollutants associated
with rruning operation (although EPA is in the process of establishing criteria and partitioning
techniques for toxic metals). Reviewers must typically rely on BPJ to determine the sediment impacts
from new sources.
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353A Guidelines for Mining Environmental Issues
Finally, the ability of pollutants to dissolve and migrate from exposed materials/waste management
units to groundwater varies significantly depending on the constituent of concern, the nature of the
material/waste, the design of the management unit, soil characteristics, and local hydrogeology
(including depth, flows, and geochemistry of the underlying aquifers). Potential risks to human
health and the environment from contaminated groundwater usage are a function of the types of and
distance to local users. In addition, impacts on groundwater can also indirectly affect surface water
quality (through recharge and/or seepage). At some sites, the potential for groundwater
contamination may be limited to alluvial aquifers which have limited beneficial uses but are significant
source of recharge. Section 4.5.1 describes elements to consider in performing baseline and long-
term groundwater monitoring!
4.7 AIR QUALITY
The primary air pollutant of concern at mining sites is paniculate matter. As noted in Chapter 5,
particulates with a diameter of less than 10 microns is one of the air pollutants for which EPA
.established National Ambient Air Quality Standards. State Implementation plans must ensure that
paniculate emissions from whatever source are controlled sufficiently to allow attainment of the
ambient air standard and to meet opacity requirements.
• _ . • • ' v
Particulates are emitted from a variety of mining operations, usually as fugitive dust (as opposed to
emissions from stacks),, and relatively simple controls are typically sufficient:
• * Ore crushing and conveyors can be a substantial source of fugitive dust, and control
generally involves water sprays or mists hi the immediate area of the crusher and
along conveyor routes.
• Loading bins for ore, limestone, and other materials also generate dust. Again, water
sprays are typically used. . .
• Blasting generates dust that can be, and sometimes is, controlled with water sprays.
• Equipment and vehicle travel on access (and haul roads is a major source of fine and
coarse dust. Most mines use water trucks to dampen the surface periodically.
• Waste rock dumping can generate dust, but this generally consists of coarse particles
that settle out rapidly with no other controls.
• Wind also entrains dust from dumps and spoil piles, roads, tailings (either dry as
disposed or the dry portions of impoundments), and other disturbed areas. Spray
from water trucks are often used when the mine is operating. During temporary
closures and particularly after the active life, stabilization and reclamation are aimed
in part at reducing fugitive dust emissions. Tailings in particular can be a potent
source of fine particulates. Rock and/or topsoil covers, possibly with vegetative
covers, can be effective controls.
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" Environmental Issues
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EIA Guidelines for Mining
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As discussed in various sections above, tailings and waste rock at
tm im S"J " ^^
contain trace
concentrations of heavy metals. Fugitive dust would also contain such metals, and areas immediately
downwind could accumulate troubling amounts of dust as coarse particles settle out of suspension hi
the air.
•i! iiiiii'iiiii iiiS j«!L ' i ; ' ' ' i ' '''""' '
* ' '
*& addition, on a few occasions, wind has caused,cyanide sprays on heap leach piles to blow short
distances and caused very localized damage. For this reason, more operators are turning to drip
" application of cyanide solutions.
4.8 SUBSIDENCE
SSlS ...... 251 ...... 2SSS ..... SS ....... a ..... r,S§ult ....... of the collapse of
strata intpjnine voids. JThe potential for •subsidence exists for all forms of .underground
Subsidence .may manifest itself_m the form of sinkholes or troughs. Sinkholes are usually
tit fiofiapse of a portion of a mine void (such as a room in room and pillar mining);
^ * •
extent of the surface disturbance is usually limited hi size. Troughs are formed from the
portions of the underground void and would be typical over areas where most of
been removed (Singh and Bieniawski, 1992).
of snjgdence ..... i§ ...... SMsI ...... ISJfeg ..... njejipd of mining employed. In many mstances,'
...... ...... ..... ...... ...... .....
traditional ...... room ...... and pillar methods leave enough material hi place to avoid subsidence .effects. '
iUar ...... retreat ..... and ..... longwall mining result hi a
ieier, 1990; Britton, 1992).
U I *
• ...... ' ............................. " ................. ' ' - ....... 'strong likelihood that subsidence wfll occur
"
••• Iiiiiiiiiii
1111 1
[[[ ... ...... ..........
operations typically consider subsidence'm the planning process. Two approaches
taken to addressmg the problem: planned subsidence or planned subsidence prevention
(Britton, 1992). The approach can be governed by the type of mining activity planned or by the
degree of severity of subsidence impacts.
Planned subsidence involves predicting the maximum area! extent and depth of ground lowering
induced by the proposed mining activities. Thls.prediction can be used to develop surface mitigation
n«asu^ or appropriate modffication of surface land uses in response to the subsidence. Typically,
subsidence will occur within a few weeks after the mining face passes under an area although it may
Pletel settle-
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Subsidence prevention involves leaving supports (pillars) hi place following mining activities to
prevent subsidence from occurring. In this approach, factors governing subsidence are also analyzed
2 ..... ISJ ..... ! ...... ...... igS3ff,,£,,2le, ..... SSS,S?y ** Amoved while leaving enough material (either the
........ RSffi ...... ffiiSSiS! ....... JS, ,ftlace to prcveiK subsidence. A combination of the planned subsidence and
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4*74
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September 1994
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EIA. Guidelines .for Mining Environmental Issues
planned subsidence prevention approaches could be used in cases where some surface features require
protection while most of the overlying area do not.
The subsidence that occurs hi areas overlying abandoned mines is referred to as unplanned
subsidence. These mines, hi many cases, lacked any overlying development and were operated
without concern for subsidence. Unplanned subsidence can also occur hi association with more
modern mining operations, arising when subsidence is not considered hi the development of the mine
plan, or hi the event of .an unpredicted occurrence (i.e., roof or pillar failures, groundwater inflow).
In these cases, the depth and extent of surface.disturbance cannot be (or is not) determined. Likewise
the time frame for the occurrence of subsidence cannot be predicted.
The extent of subsidence depends on the thickness of the seam (or deposit) mined, the amount of coal
(or ore) left in place or the amount of backfill placed hi the void, the nature and thickness of the
overlying strata, the depth to the void, the permeability of the overburden to water, and the presence
or absence of groundwater. The area potentially affected by subsidence extends beyond the area
directly above the mining void; these effects to the adjacent lands extend into what is termed the angle
of draw. The angle of draw extends 15° to 30° from the edge of the mining void outward (McElfish
and Beier, 1990, Singh, 1992). •
Effects of subsidence may or may not be visible from the ground surface. Sinkholes or depressions
hi the landscape interrupt surface water drainage patterns; ponds and streams may be drained or
' channels may be redirected. Farmland can be impacted to the point that equipment cannot conduct
surface preparation activities, irrigation systems and drainage tiles may be disrupted. In developed
areas, subsidence has the potential to affect building foundations and walls, highways, and pipelines.
Groundwater flow may be interrupted as impermeable strata break down, and could result hi flooding
of the mine voids. Impacts to groundwater include changes in water quality and flow patterns
(including surface water recharge).
The Bureau of Mines has estimated that of the seven million acres of land underlain by underground
mining, two million have been affected by subsidence (McElfish and Beier, 1990). SMCRA requires
that underground coal mining operations prevent subsidence from causing material damage to the
extent technologically and economically feasible or, to employ a mining method which provides for
"planned subsidence hi a predictable and controlled manner." Regulations governing subsidence from
non-coal mines is dependant .on the individual regulatory, authority responsible for those operations.
4.9 METHANE EMISSIONS FROM COAL MINING AND PREPARATION
The biogeochemical processes known as codification give rise to the formation of methane (natural
gas) and other gases which remain closely associated with coal hi virtually all coal-bearing
formations. Adsorbed to surface sites within the highly fractured coal matrix, methane typically
4.75 . September 1994
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Environmental Issues . EIA Guidelines for Mining
,4 constitutes only a small fraction of the total energy content of the in-place coal. Within the
formation, methane remains bound to surface sites in a monomolecular layer under the influence
iliiiiSi! I formation pressure. However, under reduced pressure conditions resulting from mining, water draw
,! , |£"|& 2S 22SlSa' methane desorbs from coal and becomes free to migrate within and beyond the coal
•in111 tirmm
Illllil IIIIH^^^^
" • I
Miners have long known of the release of methane from mined coa|; methane is responsible for some
of the worst mine explosions to have occurred in this country and elsewhere. Accordingly, coal
mining operations always include substantial ventilation equipment to maintafo airborne methane
| I (I ' l l l " I I"! i • ' , i i ' Shi
concentrations below one or two percent. Typically the vented air is released directly to the
, atmosphere, though hi some instances an effort has been made to collect and compress the methane •
' '
, s 2SS SSSSS £°.m».H2f' 555 J?. sixSSRSi.Sl.SSi. Curing extraction operations
raisesa number o.f environmental issues, both local and global. In particular, current political and
,_,,.,,==, .concern oys,,fe. prospect of global warming associated with the release of greenhouse gases
...i;;;;;;;;;;;;;;;;;;;;;;;111!^! "" i i ' i i « i ». "II i " . '"i i i J1 ' * in n ' I1 i i ' * ' i || Sr »
to the atmosphere has focused an increasing amount of attention on the role of methane in radiative
'Qf&Pii ^^^ k a S5!5§l IF®?^0!?? g35 with a radiative forcing potential of 30 to 55 tunes that
Of csEbon dioxide * Because methane's estimated contribution to the total atmospheric radiative
_ j i : i /'"i1 '! '.LI. ' ' . .. n ,n i . . '. , ',,i , u*7 . M, , IN M
forcing associated with industrial emissions is significant, and'because at least some of those
and profitably reduced, such emissions from coal mine
tion may warrant consideration as incremental or cumulative impacts associated with coal
• mining.
, !/!, ,
. ' '
:M!1H^^
emissions associated
^roximately 7-12 percent of annual methane emissions from all U.S. sources. Mejhane, jslreieased
during degassification of operating mines (78 percent of releases), during pre-mining coal seam
degassification (18 percent), and duriig cod grep^aration (4 percent). Further, due to mcreasing
methane concentrations hi coal with depth (due to temperature and pressure), an estimated 88 percent
of al^ methane releases from coal mining and" use results from underground coal, with the remaining
12 percent attributable to surface-mined coal.
As a practical matter, few or no mdmdual,|mines could to expected to release sufficient methane to
constitute a significant impact on the gjobaj attnosj)heric methane budget. However, i the importance
"': 2fj£ef 223! Potential impacts of greenhouse gas emissions make it ^propriate to examine methane
and ii
I
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EL4. Guidelines for Mining * Environmental Issues
More locally, some of the technologies associated with pre-mining degassification may have direct
surface impacts similar to those associated with oil and gas exploration and production activities.
Specifically, wells closely resembling conventional gas production wells may be completed into the
area directly above long .wall mining panels several years in advance of mining for the purpose of
removing (and recovering) methane from the coal seam. The wells are designed to draw down
formation water pressure allowing methane to enter the gas phase and flow to the well. Under
favorable conditions, methane may be recovered in sufficient quantities and under sufficient pressure
to allow onsite use or pipeline sale. In fact, coalbed methane development projects have grown
dramatically in number since the early 1980s, particularly in areas where coal is too deep to mine
economically.
Coalbed gas development wells typically produce substantial quantities of formation water along with
the gas. Such water may be high in chlorides and other dissolved solids, and presents a surface
management challenge. Additionally, drilling muds, workover and completion wastes, and other oil
and gas associated wastes may be generated at the degassification site. Any impacts caused by
coalbed degassification prior to or during mining could be considered as indirect effects of issuance of
a new source permit. Accordingly, the effects should be assessed along with other cumulative
impacts.
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H!!!!!!^ SEililS
'
,] IIIIIIIj^ ii |i|.Hiliii;J«i,l iSilllllii'V Hi !iii
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EIA Guidelines for Mining Impact Analysis
5. IMPACT ANALYSIS
This chapter describes specific NEPA documentation requirements and needs. Where appropriate, the
following sections distinguish among requirements that apply to EIDs, EAs, and EISs.
In many ways, this chapter builds on information presented hi previous sections. Chapter 2 provided
an overview of requirements 'for NEPA reviews of new source NPDES permitting actions. Chapter 4
identified the key environmental issues and impacts associated with mining industry operations.
5.1 DETERMINE THE SCOPE OF ANALYSIS
"Scoping" refers to the process of determining the nature and extent of significant issues associated
with a proposed action. Scoping is a key preliminary step for all types of assessments, allowing the
analyst to focus on what is most important.
In the case of EIDs, scoping is an informal process. As part of an initial consultation between EPA
and the permit applicant, the applicant should be prepared to explain why a permit for a new source
discharge is being requested. The applicant should be prepared to discuss the context for the permit
application and to address such questions as:
• How is the action related to your firm's business or other objectives? -
• How would the proposed new activities relate to any existing operations?
• What issues are thought to be important with regard to the new source permit (e.g., any
additional employment opportunities or effects on the local economy, pollution, nearby
historic or cultural sites)?
• What existing environmental or other studies or data would be helpful hi this review?
• Is the proposed new source discharge anticipated to raise any concerns within your
• Are any groups or individuals likely to be particularly interested in or concerned about the
new wastewater discharge?
In preparing an EA on the proposed issuance of a new source permit, EPA will review information
provided by the applicant to help identify any potentially significant issues. EPA also will contact
representatives of any Federal, State, or local government agencies that may have a particular interest
in the proposed action. Among those agencies likely to offer information that may be helpful hi the
early identification of key issues are State mine land regulatory agencies and Federal land managers,
local land use planning agencies, the State environmental protection and natural resource management
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Impact Analysis
EIA Guidelines for Mining
.agencies, and the State Historic Preservation Officer (SHPO). Contact with Regional representatives
of the U.S. Fish, and Wildlife Service and the National Marine Fisheries Service can be helpful in
early identification of any potential issues relating to federally listed threatened and endangered
species.
i iiiiiiii 11 n i in inn ill i in in i linn in iipiiiiiiiiiiiiiiiiiiiiiiiiiiiii iiiipiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii
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i , . < .« . . ' . .
Where an EIS is required, scoping becomes a formal process that involves public participation and
UTteragency coordination.
Generally, a Notice of Intent for EIS preparation will contain an initial identification of potentially
important issues associated with a proposed action. The NOI also will describe the proposed method
for conducting the scoping process and will identify the office or person responsible for matters
related to scoping. , '
EIS preparation also involves holding one or more scoping meetings, where affected Federal, State,
and local agencies, affected Tribes, and other interested persons are invited to participate in the
identification of key issues. Participants help draw attention to any other actions or previous
assessments that may bear on the proposed action. In addition, the scoping process may involve
addressing procedural issues. For example, the review and consultation procedures for the process
may be identified, a planning schedule may be developed, and page and time limits for the assessment
may beset.
• i in II
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5.2 IDENTIFY ALTERNATIVES.
! , i . , 1
In accordance with NEPA, impact analysis requires a description of the proposed action as well as a
description of all reasonable alternatives. The identification of alternatives is an essential step hi the
preparation of ETOs, EAs, and FJSs. For EISs, alternatives should be described in great detail.
I II ' i '
The description of alternatives should include an identification of any alternatives that were considered
the planning process. Any reasonable alternative should be considered by the
in order to provide EPA with more latitude in considering whether to issue the permit or
not. The rationale for the elimination of any alternatives from further consideration should be
provided.* Alternatives generally are rejected based on tedbnical, economic, environmental, or
institutional considerations. In the case of an EIS, the decision to dismiss an alternative must be
supported by data sufficient to respond to a challenging question or comment.
,
:£r^:=EE_Uj NEPAjwoceduxes recognize three general categories of alternatives: alternatives available to'
l aJteraadyKOHgidered by the applicant; and "alternatives available to other agencies with
•H£:M
IIIIIIH^^^ HIIIH^^^ !!!H
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September 1994
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ELA Guidelines for Mining Impact Analysis
5.2.1 'ALTERNATIVES AVAILABLE TO EPA
Three types of alternatives are available to EPA in assessing the potential impacts of a proposed new
source NPDES permitting action:
• Issue the NPDES permit
• Issue the NPDES permit with modifications to the proposal (including modifications that
may not have, been considered by the Applicant)
• Deny the NPDES permit.
The third option is generally referred to as the "no action alternative." This alternative provides a
baseline for comparing the impacts of other options.
5.2.2 ALTERNATIVES CONSIDERED BY THE APPLICANT
When new industrial faculties are planned, operators typically undertake feasibility and planning
studies. Companies typically investigate processing options, markets, siting alternatives, and a host of
other technical, financial, and legal issues. These planning studies can be helpful in the early
identification of critical issues, including potential land use conflicts, proximity to protected natural
resources or historic sites, or any indication of hazard potential (e.g., location of facilities in
floodplains).
The Applicant should explain the planning process to provide insight into the breadth and depth of
alternatives considered and rejected or pursued for further study. A well-documented explanation of
the Applicant's analysis of alternatives is critically important to die impact assessment process.
In particular, it is important for the Applicant to explore and document a broad scope of alternatives
that look at pollution prevention opportunities.
As part of an EID, the Applicant should provide a detailed description of the proposed action(s) as
well as a description of any alternatives that were considered, but rejected. The Applicant should also
consider the "no action alternative," which would be not to apply for the NPDES permit.
EPA's NEPA procedures require that the Applicant provide: (1) "balanced" descriptions of each
alternative and (2) a discussion covering size and location of facilities, land requirements, operations
and management requirements, auxiliary structures such as pipelines or transmission lines, and
construction schedules.
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Impact Analysis
EIA Guidelines for Mining
IIIIIIH
The Applicant should explain the implications of each option with regard to the firm's goals and
objectives. The Applicant should consider the full range of options for meeting these goals and
objectives, including options that do not involve a discharge subject to permit requirements.
5.2.3 ALTERNATIVES AVAILABLE TO OTHER AGENCIES
A third category of alternatives are those available when EPA is preparing an EIS or other
In i i in , i in i • „ r •
environmental document hi conjunction with another Federal or State agency. These additional
alternatives would be based on other relevant regulatory authorities. For example, hi addition to a
new source NPDES discharge, a proposed project might involve dredging or filling of a wetland. In
mis case, the U.S. Army Corps of Engineers would be responsible for issuing a permit under Section
of the CWA., Accordingly, the environmental analysis should account' for the' various alternatives
available to the Corps of Engineers, which would include: granting the permit; granting the permit
with modifications or conditions; or denying the permit. The information to support issuance of a
permit under Section 404 should be included in the EIS, including how impacts to aquatic resources
compensated for.
were avoided, minimized, or compensa
5.3 DESCRIBE THE AFFECTED ENVIRONMENT
The affected environment section of any NEPA document should be no longer or more detailed than
Deeded to understand potential environmental impacts. Background information on topics not directly
related to expected effects should be summarized, consolidated, or referenced to focus attention on
important issues.
The scope and content of this section of an EID will be determined during an initial consultation
between EPA and the Applicant. Generally, the Applicant will be required to provide any relevant
information that is readily available. In establishing the scope of this section of an EID, EPA will
consider the size of the new source and the extent to which the Applicant, is capable of providing
information. Requests for data should be kept to a minimum consistent with requirements under
iL1 J ' ' ' ;":" " !
For an EA, the description of the affected environment should focus on key issue areas, including the
"' : :: : " following:
Current and projected land use within the project area and within the region
i si i • Current and projected population and population density
Relevant land use regulations
* Leial and regional patterns of energy demand and supply
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September 1994
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"EIA Guidelines for Mining Impact Analysis
• Local ambient air quality conditions •
• Local ambient noise levels
• Location of designated floodplains within the vicinity of the project
• Surface water and groundwater quality and .quantity
• Local biological communities and fish and wildlife habitats
• Critical habitats of any Federal- or State-listed threatened or endangered species
• Location of any properties listed in or eligible for listing in the National.Register of
Historic Places
• Location of specially protected areas, including parklands, wetlands, wild and scenic rivers,
navigational areas, or prime agricultural lands.
in the case of an EIS, the description of the affected environment is more extensive and detailed. The
breadth of topics typically addressed within an EIS is discussed below.
5.3.1 THE PHYSICAL-CHEMICAL ENVIRONMENT
The physical-chemical environment comprises the air, water, and geological characteristics of sites
where the environmental impacts of alternatives will be evaluated. This section of an EIS should
provide sufficient information to determine whether impacts are likely to be significant.
53.1.1 Air Resources
Air resources are described by the physical dynamic behavior of the lower atmosphere and by
variations in the concentrations of various gases and suspended flatter. Physical dynamic behavior is
described by parameters such as the seasonal distribution of wind velocity and the frequency and
height of inversions. Wind velocity and the frequency of occurrence of inversions are often
determined by specific local topographic features, particularly surrounding hills or mountains. Air
quality is described by the variations hi the concentrations of pollutant gases hi the lower atmosphere.
Both are needed to determine the environmental impacts of facility stack emissions, the effects of
mobile sources on local ah* quality, and the likelihood that dust will be of importance during
construction, operation, and after abandonment.
The description of meteorological regime(s> should include a generalized discussion of regional and
site-specific climate including:
• Diurnal and seasonal ground-level temperature
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" Impact Analysis
EIA Guidelines for Mining
Wind characteristics at different heights and times (wind roses are particularly helpful and
Pr°Y^5 ^^? 5E??? Direction, ^K^ipy, and stability characteristics of the atmosphere)
Total monthly, seasonal, and annual precipitation, frequency of storms and their intensity,
including both average and extreme events
11 ' " ' I ' Ih
, 41 '.'
* HeigBt* frequency, and persistence of inversions and atmospheric mixing characteristics
* Description of pattern(s) evident for days of significant pollution episodes; evaporation.
Information on ambient air quality is often required to predict the impacts during construction and the
pollution concentrations can,be predicted for comparison with various Federal, State, and local
Depending on the scale of the analysis, data' should be presented for the relevant airshed,
the, site itself, or both. Also, the site's location relative to airy Class I areas (e.g., National Parks)
areas that are in nonattainment with any National Ambient Air Quality Standard should be
Emission inventories and ambient air quality as reported by State and local air pollution control
^^f15 are ** data sources for an air basin or regional airshed level analysis. At a minimum, .major
sm**j°as*y S0laces snA %"" en^ssipns shou|4 be cjiaracterized, with diurnal variations in emissions by
!™°?£ ££' «i ?eak, season for pollutants of concern. P^jectionsjifjncreases |n emissions, and ; i
long-term pollutant concentrations are also important at this level. The comparison of expected trends
with existing Federal, State, and local standards (including identification of Cjass I areas and the
attainment status of the area) becomes a major design parameter far gaseous emfcsion controjls.
Site-level analyses are more detailed in their geographic scope, but require similar information. One
of odors' dust»
iSfiSS i22S2SS°,5 2?y becom& important in detennjnjng local impacts. Air quality
to determine me directions and ground level concentrations of pollutants of
4^ models require most of the information described in the previous paragraph along
emission temperature, emission velocity, and
. of the stack gases.
IIIH^
5.3.1.2 Water Resources
Information on water resources to be hicluded in the affected environment chapter should cover:
whether these waterbodies are jurisdictional waters of the United States, any special aquatic sites,
descriptions of waterbody types (i.e., local streams, lakes, rivers, and estuaries), and descriptions of
groundwater aquifers. Descriptions of water body types, flows and dilutions, pollutant
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. 'E1A Guidelines for Mining • . • Impact Analysis
concentrations, special aquatic sites, and habitat types near potential discharges are necessary to
determine the changes hi the water environment that will occur with facility construction and
operation. Descriptions of alluvial and bedrock aquifers are necessary to determine the potential for
contamination of groundwaters from site activities. Of key importance here is the depth to the water
table, and the nature of overlying soils and geologic features. Descriptions of groundwaters should
include the location of recharge areas, and, in areas of water shortage, then- present uses.
Descriptions of surface waters should include seasonal and historical maximum, minimum, and mean
flows for rivers and streams, and water levels or stages and seasonal patterns of thermal stratification.
for lakes and impoundments. The use of surface waters (diversions, returns; and reclamation) may
also be important in certain locations where water resources are scarce. Information on ambient
concentrations of pollutants, and other local sources, are also necessary to determine resulting
concentrations of pollutants with new discharges.
If imported water is to be used at the site for process water or other purposes, the source, quantity,
and quality of the water should be described. Any existing NPDES permits should be identified along
with a description of wastewater flows and quality.
If the site might be subject to flooding (is within the 100-year floodplain), the dates, levels, and peak
discharges of previous floods should be reported along with the meteorological conditions mat created
them. Projections of future flood levels should also be included for typical planning levels of SO- and .
100-year floods.. These projections should include anticipated flood control projects such as levees
and dams that will be built.
53.13 Soils and Geology
The physical structure of soils and their underlying geologic elements determine the extent to which
soils will be affected by facility construction and operation. Useful parameters include permeability,
erodability, water table depth, and depths to impervious layers. The engineering properties and a
detailed description of surface and subsurface soil materials and their distribution over a site provide
most of the information necessary.
Local and regional topographic features such as ridges, hills, mountains, and valleys provide
information on watershed boundaries, and site topography (slope and elevation characteristics)
provides information that is needed in determining the potential for erosion.
Geological features are important when paleontological sites and other areas of scientific or
educational value may be disturbed or overlain by facility structures.
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Impact Analysis
EIA Guidelines for Mining
In regions of the country that are seismically active, the description of the affected environment .
should information necessary to assess potential risks. Relevant information can include proximity to
faults, the history of earthquakes in the area, locations of epicenters, magnitudes, and frequency of
occurrence. • '
ii
5.3.2 BIOLOGICAL CONDITIONS . .
M i n i 11 i . 11
\
Key elements of a description of biological conditions include the distribution of dominant species,
• identification and description of rare, threatened, or endangered species, and a characterization of
ecological interrelationships.
St;ft3.i.I > . , . i. .' ,,,, -, , ":,(. • • ' ' '
distribution of vegetation types within the project area. The presence in the area of rare, threatened,
or endangered species and unique'giant assemblages are particularly important, especially if any are
likely to occur at the site. There are a variety of ways to describe vegetation, but the most useful is
to divide the site flora into four or five "typical" assemblages and map their distribution and that of
ized scientific and educational areas. For threatened, endangered, or rare species, however, it
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In areas subject to forest fires, fire hazard should be described by describing the history of fires hi the
area, projecting the severity of fire hazard hi the future, and describing existing fire control and
f""- •.! i " • : " • •• • H, •
management actions.
Aquatic and marine vegetation, particularly in the vicinity and downstream of proposed discharges,
also should be characterized. General .community characteristics, including dominant species and
sity, should be identified.
diversi
Wildlife ' .
N """ I
The presence of wildlife at a site is largely dependent on the nature and distribution of vegetation.
i ' ' r i i i
Particular emphasis should be placed on the presence of rare, threatened, or endangered species hi the
general vicinity of the site, and she-specific discussions are mandatory when the site provides habitat
that is used by rare, threatened, or endangered species. Under these circumstances, the relative
abundance of all rare, threatened or endangered species and the dominant wildlife fauna should be
surveyed on site and presented in the EIS. Otherwise, a general description of the wildlife species
within the area is sufficient.
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EIA Guidelines for Mining _ _ _ _ __ _ Impact Analysis
5.3.23 Ecological Interrelationships
A characterization of the key interrelations and dynamics within an ecosystem provides a foundation
for impact assessment.
Although it is difficult to determine the extent to which plants and animals are interdependent at a
given site* specific attention should be given to identifying the food sources of dominant or rare
animal species, the factors that limit these food sources (including factors such as soil structure and
moisture content, -soil surface temperature ranges, and specific soil micronutrients), and the ability of
animal species to substitute food sources should current food sources be reduced hi abundance.
Ecological interdependencies hi aquatic systems are also important, and aquatic communities change •
dramatically with large increases in nutrient or sediment discharges. While prediction of changes hi
plant and animal populations is difficult under the best of circumstances, significant changes (either
positive or negative) cause concomitant changes hi both terrestrial and aquatic fauna.
: 533 SOCIOECONOMIC ENVIRONMENT
The socioeconomic environment encompasses the interrelated areas of community services,
transportation, employment, health and safety, and economic activity. The activities associated with
the construction and operation of new source facilities must impact human resources (employment,
population, and housing), institutional resources (services or facilities), and economic activity. The
information required to assess impacts are described below.
533.1 Community Services
. • v
Community services such as water supply, sewerage and storm drainage, power supply, and
education, medical, and fire and police services are almost always affected by major new projects. It
is important in an EA or EIS to describe the nature of existing public facilities and services within the
general vicinity, the quality of the service provided, and the ability of the existing public facilities and
services to accommodate additional users. The most critical consideration is the level of services that
would be provided hi the anticipated peak year assuming no project were to be undertaken.
and temporary household relocations create demands on the housing market. The number
of nearby housing units, then* cost, vacancy rates, and owner-occupancy rate are all significant factors
hi determining the suitability of the existing housing stock for occupancy by a temporary or
permanent workforce. In addition, the present rate of growth within the housing sector can be
compared with the anticipated growth hi housing supply and demand and the amount of land available
for new housing to determine whether existing policies and attitudes toward growth are adequate to
accommodate the additional residents.
5.9 September 1994
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Impact Analysis EIA Guidelines for Mining
5.3.3.2 Transportation
l| ! |
Transportation systems provide access to a facility for the import of raw materials, export of final
products, and the movement of staff and service personnel. All relevant forms of transport for the
fecffity should be described. For all facilities, road-based transport is of potential significance, but
railways, airways, pipelines, and navigable waterways may also be important for some facilities.
Current traffic volumes, current traffic capacity, and an assessment of the adequacy of the systems for
meeing peak demands during construction and operation should be presented.
S333 Population
Total population, rate of growth, general spcioecononnc composition, transient population, and the
^f or n*31 aafpre of *&e local population are parameters needed to assess the importance of the
impafts °f PSJffJ"!1*0^ c&iPges on the local community. Information on average household size,
average age, age/sex distributions, ethnic composition, average household income, percent of
households below poverty -level, ....... and ...... median ...... educational ....... level ....... ajlgjr ...... a ..... more ...... refined analysis of
. project-induced changes. Projections of demographic trends for the region and project area without "
the project are also necessary to determine the relative impacts of the project in future years.
* ' ii • i » i ! '
........... ' .................... i:" ......... "::" ..... n~S3~3A ........ ] ................. Employment [[[ "
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» ...... S2S2JI.SE ...... fiS ..... iSSiSSJction ...... and ...... operation of any .new facility. Construction is
nonnS& 2E25! 2HS te 4 temporary workforce of construction workers, not by the permanent
workforce in the area near the site. Qn the other hand, facility operation usually relies on a
pennanent workforce, and the source of personnel for this workforce may be local or from other
parts of the country. In any case, increases in the number of personnel required to build or operate a
^7;?** ""P***** * accomPani«!1J>Z ...... 555?** ....... in employment in enterprises required'to
support the imcfliry, indirect (secondary, non-basic) employment, as demands for goods and services
316 v****- The direct and indirect employment generated by a project, in turn, generates
............................
^va^°ftoasefaolds.resultiiigrnpoin and changes in the demographic
characteristics of communities.
To defzmme impacts of additional employment on the local enyironrnent, it is necessary to present
information about the local labor base-where people work, what they do, their skills and education
Jgjji'! fi—SSiSTO — SSffiESfiSSHE .HE: H* gsaastiaia alfee unemployed •
^"T011 m especially important if Sere is an expectation that a new facility will generate
employment for them. Projections should also be included on anticipated trends in employment and
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EIA Guidelines for Mining Impact Analysis
5.3.3.5 Health and Safety
Description of the present health and safety environment should include statistics on industrial
accidents in the local area; a discussion of-air, water, and radioactive emissions from existing and
prior facilities and their effects on human health and the environment; and an analysis of present
levels of noise and their impacts on people and wildlife. The identification of applicable regulatory
standards provides a benchmark against which the present and future health and safety environment,
with and without the project, can be judged.
5.3.3.6 Economic Activity
Economic activity will always be affected by new facilities. Current economic activity should be
described by characteristics of local businesses (number and types of businesses, annual revenues, and
ownership patterns) and the availability of capital for future growth. To predict changes in the kinds
of economic activity mat would occur with the project, it is necessary to describe the kinds of goods
.and services that would be required by the project or associated workforce and determine whether
they are provided locally or imported. Unique features of the business community such as high
seasonally, high outflow of profit, declining trade, or downtown revitalization should also be
included.
5.3.4 ' LAND USE
A description of land use should identify the current use of land needed specifically for the facility, its
system components, its safe area, and its residuals; and land us& patterns in the nearby area that will
be indirectly affected by the project. Particular emphasis should be placed on land uses that pose
potential conflicts for large-scale industrial activity—residential areas, agricultural lands, woodlands,
wetlands—and on the local or regional zoning laws that may limit the development of industry or
commercial activities on which it relies. Also of crucial importance is the anticipated (and/or
required) use of the land once mining operations end. ,
5.3.5 AESTHETICS .
Aesthetics involve the general visual, audio, and tactile environment (imagine the sensory differences
among urban, industrial, agricultural, and forest environments). A description of the aesthetic
characteristics of the existing environment should include things that are seen, heard, and smelted in
and around the site and their emotional or psychological effect on people. Descriptions (or pictures)
of views of the site, of unique features or features deemed of special value, and public use and
appreciation of the site provide information that must be available for the assessment of impacts.
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Impact Analysis
EIA Guidelines for Mining
ii-
5.3.6 CULTURAL RESOURCES
i ii , i •
Cultural 'resources is a broad category that encompass resources of current, prehistoric and historic
significance. The location of a facility near significant historical and cultural sites can degrade their
resource value or emotional impact. The location of the following kinds of sites should be described
in relation to the project site:
I i i i i .
(
• Archeological sites (where man-made artifacts or other remains dating from prehistoric
.................... times are" found) ' ". •
> Paleontplogical sites (where bones, shells, and fossils of ancient plants or animals are found
in soil or imbedded in rock formations)
> Historic sites (where significant events happened or where well-known people lived or
worked)
Sites of particular educational, religious, scientific, or cultural value.
"'Of particular concern ^^1^ beicaoq»ly^. v^ §106 of the National Historic Reservation Act for
...................... • ....................... sites listed on, or eligible for listing on, the National Register.
"l! ..................... ^ ............. 5.4 ANALYZE POTENTIAL 'IMPACTS
!.•; .. . ." • ..... •• : • • . "• •• !: '
The major environmental issues associated with the mining industries were discussed hi the previous
chapter. Although Chapter 4 presents guidance for the analysis of impacts that tend to be common to
these industrial categories, it is important to recognize.that other types of impacts are bound to be
assoc ated with specific proposed actions. Thus, reviewers must ensure that all key- issues identified
during the scoping process are fully analyzed. The section below provides more specific guidance on
the preparation of the "Environmental Consequences" section of an EIS. It also serves as the focus
"" of any administrative appeal or -legal challenge of the permit.
I :; ; ; ; ; ; : ; : : ; ' : : ' : ":::; :
The "Environmental Consequences" section of an EIS forms the scientific and analytical basis for the
I t i ni i i . i in i i i •
comparison of alternatives. Accordingly, it should contain discussions of beneficial and adverse
impacts of each reasonable alternative and mitigation measure (40 CFR 1502.16 and 1508.8)
I";,;;, , - ' " " : ' . ' " ' , I ' , • ' '
including clear, technical demonstrations of:
;; ; , | J
— : ;::; • *Z,; 2Iffip| Sffscis Sffil IhSIE significance—direct effects are caused by the proposed action and
occur at the same time and place.
Indirect effects and their significance—indirect effects are those caused by the action but are
!2S£ Si iSSHS JiSSSyiSii Hi liSSSSSz but are reasonably foreseeable. This also
growth effects related to induced changes in the pattern of land use, population
_ __^ ^__^ —^ rejj effects on air, water, and ecosystems.
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EIA Guidelines for Mining . ' Impact Analysis
• Possible conflicts between proposed actions and the objectives of Federal, regional, State,
local and tribal land use plans, policies, and controls for the area concerned.
• Energy requirements and conservation potential.
• Natural or depletable resource requirements and conservation potential.
• Urban quality, historical and cultural resources, including reuse and conservation potential.
• Means to mitigate adverse environmental impacts not fully covered by the alternatives.
• Project compliance with water quality standards and the significance of the anticipated
impact of the discharge (this is particularly important for new source permits).
• Project compliance with National Ambient Ah- Quality Standards and, if applicable,
Prevention of Significant Deterioration increments.
The potential impacts of each alternative are identified by a systematic disciplinary and
interdisciplinary examination of the consequences of implementing each alternative.
5.4.1 METHODS OF ANALYSIS '
While information may be gathered from new source NPDES applications, HDs, and other sources,
EPA is responsible for the scientific and professional integrity of any information used in EISs for
which it is responsible. The applicant's EID and other sources of data, therefore, must clearly
explain all sources, references, methodologies, and models used to analyze or predict results. •
Applicants should consider the uses and audiences for their data and EPA's affirmative responsibility
in using them. EPA has the same responsibility in the use of data submitted by other agencies,
private individuals, or groups. ' .
Each impact has its own means of identification, qualification, and quantification. For example, air
quality impacts are modeled using standard State or Federally approved programs. These numerical
models depend on standardized parameters and site-specific data. Stationary source emissions from
plant operation as well as mobile emissions related to traffic circulation from induced employment or
growth all contribute to air quality impact quantification. The goal is to quantify impacts on air
quality, water quality, employment, land use, and community services—categories that lend
themselves to numerical calculations, modeling, and projections. Some environmental elements like
aesthetics lend themselves to more qualitative or graphic analyses.
Biological impacts frequently are not readily quantifiable becaus: absolute abundance of individual
species are difficult to determine. Impacts may be described as acres of habitat lost or modified or to
qualitative impact descriptions of population changes in major species or species groups. The key in
the Environmental Consequences section is to clearly and succinctly lead a reader through each impact
5-13 September 1994
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Impact Analysis
EIA Guidelines for Mining
identification, qualification and/or quantification. Detailed methodologies or extensive data can be
!!_ ji|p»2£2S2 «X SSSSfi EiSLiXP?- ^ readav obtainable. WUdltfe agencies can' be source of data
W pSs section. Materials from applicants must carefully follow this pattern to facilitate validation
and incorporation in tfie EIS. • . '.
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5.4:2 DEIERRHNATION OF SIGNIFICANCE ' : '_
As djscussed in Chapter 2 of these guidelines, The term "significant effect" is pivotal under NEPA,
for an EIS must be1 prepared when a new source facility is likely to cause a significant impact. What
is significant can be set by law, regulation, policy, or practice of an agency; the collective wisdom of
a recognized group (e.g., industry or trade association^standards); or the_ professional judgment of an
expert or group of experts. CEQ (40 CER 1508.27) explains significance in terms of .context and
intensity of an action. Context relates to scale—local, regional. Slate, national, or global; intensity
refers to the seventy of the impact. Primary impact areas include affects on public health and safety,'
and unique characteristics of the area (e.g., historical or cultural resources, parks, prime farm lands,
wetlands, wild and scenic rivers, or ecologically critical areas). Other important factors include:
' Degree of controversy
Degree of uncertain or unknown risks
Jkelihood a precedent will be set
V
^S!? ie?ISc!?^y ^ individually not significant)
!2 which sjtes Ksted, or eKgible for listing, in the National Register'of Historic
Places may be affected
Degree to which significant scientific, cultural, or historical resources are lost
Degree to which threatened or endangered species or their critical habitat is affected
* The, iike#ho<|| of violations of Federal, State, regional or local environmental law or
requirements or alternatively, likelihood that applicable standards applicable to the operation
and various environmental media can be achieved.
EPA's NEPA procedures require that the Agency consider short-term and long-term effects, direct
and indirect effects, and beneficial and adverse effects.. Of particular concern are the following types
»of impacts: " • ' .' ' • •
The new source will induce or accelerate significant changes hi industrial, commercial,
agricultural, or residential land use concentrations or distributions which have the potential
1
5-14
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ELL Guidelines for Mining Impact Analysis
for significant environmental effects. Factors that should be considered in determining
whether these changes are environmentally significant include but are not limited to:
The nature and extent of the vacant land subject to increased development pressure as a
result of the new source
The increases in population or population density which may be induced and the
ramifications of such changes
The nature of the land use regulation in the affected areas and their potential effects on
development and the environment
The changes in the availability or demand for energy and the resulting environmental •
consequences.
• The new source will'directly, or through induced development, have significant adverse
effects upon local ambient noise levels, floodplain, surface or. groundwater quality or
quantity, fish, wildlife, and then: natural habitats.
• Any major part of the new source will have significant adverse effect on the habitat of
threatened or endangered species on the Department of the Interior's or a State's list of
threatened and endangered species.
• The environmental impacts of the issue of a new source NPDES permit will have significant
- direct and adverse effect on property listed in the National Register of Historic Places.
• Any major part of the source will .have significant adverse effects on park lands, wetlands,
wild and scenic rivers, reservoirs, or other important bodies of water, navigation projects,
or agricultural lands.
With the regulations hi mind, it is ultimately up to the EA and/or EIS preparer(s) to make judgments
on what constitutes a significant impact. The threshold of significance is different for each impact,
and those making the judgments need to explain the rationale for the thresholds chosen. Clear
descriptions of the choice of the threshold of significance provides a reviewer with a basis for
agreeing or disagreeing with the determination of significance on based on specific assumptions,
criteria, or data. Sometimes the thresholds are numerical standards set by regulation. In other cases,
the thresholds may be set by agency practice (e.g., the U.S. Fish and Wildlife Service may consider
the potential loss of a single individual of ah endangered species as a significant impact), or the EPA
preparer's professional judgment that determines the rationale for the threshold. The NPDES permit
applicant may suggest a threshold for each impact identified in the EID, but it is critical to carefully
define how and why each particular threshold was chosen and applied.
5.15 September 1994
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!!i!!!!!!i! iiiil!!!!!!!!!!!!!1!' i!!!!!!!!!!!!!!!!!!!' "i!'!!!! "!!!!««!!!!«""!•!!!!!!!!!!!!!!!«'"" in!!!!!!!!!!!!1'!!"!'!' !!!!!!•!!!!!!!!!!!!!!!!!!!!!!!!!!!!•!!
Impact Analysis
EIA Guidelines for Mining
t
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i nun iiiiiiiiiinnn iiiiiiiiiiiiiiiiiii mini iniiiiiiiiiiiiiiini nun iiiiiiiiiiiiiiiniiiiiiiiiiiiiiiiiiiiiiiiii iiiiiiniiiiiiiiiiiiiiiiiiiilliiiiiiiiiiin inn miiiimii||immmm mi iinniiiiiiiiiiiiinniiiyiiiiiiiiiiiiiiiiiiiii n iiiiiiiiinn 1 1 iiiiiiiini ni jiiiiiiiiiiiiiini linn iniiiininn in n inn i iiiiiini i nun iiiiiiiini mi mil mmnnmimmmmimmmmmnnn inn n myi in 1 1 1 iiiiiiiiini iiiiiiini m inn mini n nun nviiiiiiiiiiiiinn m iiiiini in inn in in mum 1 1 1 inn 1 1 n mmnmlmiillm
5-4.3 COMPARISONS OF IMPACTS UNDER DIFFERING ALTERNATIVES
' i,,'' ,*'i ''•'•"• ' / • ;.' "' •>'. •' ' > '.i, i , :! , ,]."•..•! '!„ ' :' '' ..
Alternatives can be compared in several different ways. All of the impacts associated with a single
alternative may be examined together and summarized in a final list'of significant unavoidable
impacts, or the like impacts of all the alternatives can be determined and compared within a final
summarized list of significant unavoidable impacts. The choice of approach should be determined by
me
t &S preparers based on the approach that would.provide the most clear, concise evaluation for
decision makers and reviewers. The summary information on possible impacts and mitigation
measures is usually prepared in tabular form and included in the executive summary. Examples of
ft)rpats that can be used are found in standard_environmental assessment technology texts, agency
maiiibate, EAs, EISs, and similar documents.
5.4.4 SUMMARY DISCUSSIONS
IIIIIIH ..... IIIL
CECJ and EPA NEPA guidelines describe the expected general ...... .contents, ....... of; the ...... section ...... called [[[
"Environmental Consequences." In addition to identifying, quantifying, and comparing the impacts
of each alternative, 40 CER 1502.16 specifies that discussions will include "..any adverse
P^ffiiSM, Exacts which cannot be avoided should the proposal be, implemented, the relationship
between- short-term uses of man's environment and the maintenance and enhancement of long-term
productivity, and any irreversible or irretrievable commitments of resources which would be involved
in .the proposal should it be implemented."
Over the last 20 years, these three topics have been included as a separate chapters) in draft EISs
along with chapters called cumulative impacts, adverse effects which cannot be avoided, or residual
impacts and mitigation. No matter what format is used with these topics, they often receive only
cursory treatment. Such a practice is unfortunate because these long-term, larger scale issues are
those that affect overall environmental quality and amenities. The important point is not the location
of these topics in the document, but the need to present data, and analytical procedures used to qualify
these concerns.
nil i in i iiiiiiiini i iii
A section called cumulative impacts can be addressed in several ways. Some EISs consider
cumulative impact sections to be summaries of all residual impacts for each alternative. They may
also inciude'any synergistic effects among impacts. A second, and more helpful, approach to
cumulative impacts reflects a broad view of environmental quality and suggests how impacts of the
proposed project or alternatives contribute to the overall environmental quality of the locale, in the
immediate future and over a longer time. In this approach, the impacts of the new source project are
considered m relation to the impacts associated with projects approved, but not constructed; projects
,, jfglP*, considered for approval; or planned projects. This "accumulating" impacts approach to
cumulative impacts is particularly instructive when no single project is a major cause of a problem,'
but contributes incrementally to a growing problem
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5-16
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EIA Guidelines for Mining
Impact
All of these summary topics focus on broad views and long time lines in a attempt to put project
impacts in perspective. . The data requests from EPA to applicants must specify the environmental
setting and consequences data needed to qualify and quantify the potential impacts and put each
potential impact in perspective in terms of local, regional and perhaps State or national environmental
quality. •
5.5 DETERMINE MITIGATING MEASURES
Initial efforts to meet requirements under NEPA emphasized the identification of mitigation measures
for all potential impacts conceivably associated with a project or its alternatives. Current practices
emphasize avoiding and minimising potential impacts before a NEPA document is prepared. This is
accomplished by refining the proposed project and alternatives during siting, feasibility, and design
processes. The goal is to propose project alternatives with as few significant impacts as possible.
CEQ NEPA regulations define mitigation (40 CFR 1508.20) to include:
• Avoiding the impact altogether by not taking a certain action or parts of an action
* Minimizing impacts by limiting the degree or magnitude of the action and its
implementation
• Rectifying the impact by repairing, rehabilitating, or restoring the affected environment
• Reducing or eliminating the impact over time by preservation and maintenance operations
during the life of the action v • '
• Compensating for the impact by replacing or providing substitute resources or
environments.
This listing of mitigation measures has been interpreted as a hierarchy with "avoiding impacts" as the
best mitigation and "compensating" for a loss as the least desirable (but preferable to loss without
compensation). This hierarchy reinforces the present approach of trying to avoid or minimize
potential impacts during project siting and design. The goal is to have the most environmentally
sound project and alternatives to carry into the impact assessment process of NEPA.
Even with the best project siting and design, there will be environmental impacts associated with each
of the alternatives. For the impacts, especially for the impacts judged to be significant impacts,
mitigation measures need to be suggested.
The first source of possible mitigation measures should be those offered hi an applicant's EID. Each
mitigation measure should be described in enough detail so that its environmental consequences can
be evaluated and any residual impacts clearly identified.
5_17 September 1994
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Impact Analysis
EIA Guidelines for Mining
ive typically reflects choices among tradeoffs. The tradeoffs can include
, pollution control technologies, costs, or other features. Typically the tradeoffs
Sj"|ii5fplex for new source facilities with dfcsimilar beneficial and detrimental impacts among the
3S|: il| ill Il&ays shojii Ascribe the process that led lp, and the rationale far,, .the,
selection of the preferred alternative. The analysis should be deemed complete if:
Tie alternatives brought forward for analysis are all reasonable
=;=:£=: • All possible refinements and modifications for environmental protection have been
^I="::=; • Any residual impacts and consequences of mitigating those impacts have been evaluated.
II!~ •"
of the many laws, regulations, executive orders, and policies identified hi Chapter 6 should be
•jjsssssaa a*, the Consultation and Coordination section of an EIS. The applicant should provide a
ji9' ^^£^{2yj{fe£ and gptipjis uj3er easfe o£|^jriiti|tiiess lie appicar^nmded
environmental setting and environmental consequences materials should include sufficient data on the
_ _ liiiiBjj i i i !, i _ , ,
envtfotim&tt: issues raised by these laws, regulations, and orders to identify and analyze the potential
Impacts. • ' ' ". '. '.
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5-18 September 1994
I gj ; , ' • i .
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E1A Guidelines for Mining Statutory Framework
6. STATUTORY FRAMEWORK
Mining operations are subject to a complex web of Federal, State, and local requirements. Many of
these require permits before the mining operations commence, while many simply require
consultations, mandate the submission of various reports, and/or establish specific prohibitions or
performance-based standards. • Among the Federal statutes that are potentially applicable are those
shown in Exhibit 6-1. Also shown are the agency with primary responsibility for implementing or
administering the statute and the types of requirements that are imposed on those subject to various
statutory provisions.
The following sections describe the purposes and broad goals of thes,e statutes. The discussion for
each statute also provides an overview of the requirements and programs that are implemented by the
respective implementing agencies.
6.1 CLEAN WATER ACT
The objective of the Clean Water Act is to "restore and maintain the chemical, physical, and
biological integrity of the Nation's waters" (§101(a)). This is to be accomplished through the control
of both point and nonpoint sources of pollution (§101(a)(7». A number of interrelated provisions of
the Act* establish the structure by which the goals of the Act are to be achieved. Within this overall
structure, a variety of Federal and State programs are implemented to meet the Act's requirements.
Under §303, States are responsible for establishing water quality standards and criteria for waters
under their jurisdictions: these are the beneficial uses that various waters are to support and the
numeric (and narrative) criteria that must be achieved to allow these uses to be met. Water quality
standards and criteria serve as a basis both for identifying waters that do not meet their designated
.uses and for developing effluent limits in permitted discharges. EPA also establishes nonbinding
numeric water quality criteria as guidance; when States fail to adopt sufficient water quality standards,
EPA may do so. .
Under §402 of the Act, all point source discharges (see below) of pollutants to navigable waters of the
United States must be permitted under the National Pollutant Discharge Elimination System. (NPDES).
Effluent limits in NPDES permits may be technology- or water quality-based. For various categories
of industries, EPA establishes National technology-based effluent limitation guidelines pursuant to
§§301, 306, and 307.
The term "navigable wcters" or "waters of the U.S." includes all waters within the territorial seas
(i.e., within the three-mile contiguous zone around the United States). Waters of the United States
need not be navigable in fact (see U.S. v. Ashland Oil, 504 F2d 1317 (6th Cir. 1974)), and may be
6-1 September 1994
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! Statutory Framework
EIA Guidelines for Mining
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-------
Guidelines for Mining
Statutory Framework
D Mining Operations (Continued)
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Statutory Framework
EIA Guidelines for Mining
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Guidelines for Mining
Statutory Framework
Mining Operations (Continued)
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Statutory Framework
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September 1994
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Guidelines for Mining Statutory Framework
- .. Point Sources Under fire dean Water Act
The term "point source" means any discernible, confined, and discrete conveyances-including
but not limited to any pnie, ditch, channel, tunnel* conduit, well, discrete fissure, container,
rolling stock, concentrated animal feeding operation, orvessei or other floating craft from which
pollutants are or may be discharged" fCWA §502(14)}. For purposes of the [CWA], the term
"point source" includes a landfill leachate collection system. 1987 Water Quality Act, PL 100-
4, §507. The definition has been codified at 40 CFR 122,2. " - A
• f- J- o
M the preamble for a. storm water rulemaldng {55-FR 47997; November 19,199Q),"EPA cited
court decisions mat bear on the definition (Sierra Club v. Abston Construction Cony any, 620
F.2d (5flj dr. 1980)): *. » , Nothing in me [Clean Waterl Act relieves [dischargers] from
liability simpfy-because operators did. not construct mose conveyances, so long as they are
reasonably likely to be the means by which pollutants are ultimately deposited into a navigable
body of water. Conveyance of pollution formed either as a result of natural erosion or by
material means, and which constitute a component of a»» - drainage system, may fit the
statutory definMon and thereby subject the operators to liability under the Act." Overall* EPA
concluded that it intended to *.. ». embrace the broadest possible definition of point source
consistent with me legislative intent of the CWA and court interpretations to include any
Identifiable conveyance from which pollutants might enter the waters of the United States.8
- Further, EPA noted that facilities themselves had the burden of determining whether an
application should be submitted lor a point source (and, by implication, of determining whether
a discharge was from a point source) and advised facilities to submit an application or consult
with permitting authorities in cases of uncertainty. It should be noted mat Federal courts have
spoken to the issue of point sources at mine sites? for example, in Kennecott Copper Corp. v.
EPA* 612 F.2d 1232 (1O Ofc. 1979), the court was asked to rule on whether certain discharges
were subject to 40 CFR Part 440. One of the court's conclusions was that whether certain of
Kennecott's facilities were point sources was a determination *to,be made In the lost instance hi
the context of a permit proceeding."
intermittent or seasonal. In at least one case, a discharge which was traced into and through
groundwater was considered a discharge to waters of the United States (see Quivera Mining Co. v.
U.S. EPA, 15 ELR 20530 (10th Or. 1985)).
EPA's NPDES regulations [40 CFR 122.21(1)] require prospective dischargers (in States wirnout an
approved NPDES program) to submit information to the EPA Region, prior to beginning on-site
construction, that will allow a determination by EPA of whether the facility is a new source. The
criteria for this determination are in 40 CFR 122.29. The .Region must then issue a public notice of
the determination. If the facility is determined to be a new source, the applicant must comply with
the environmental review requirements of 40 CFR Part 6 Subpart F. In preparing a draft new source
NPDES permit, the administrative record on which the draft permit is based must include the
environmental information document prepared by the applicant, the environmental assessment (and, if
applicable, the FNSI) prepared by EPA, and the environmental impact statement (EIS) or supplement,
September 1994
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iiiliivlliipiillilliipililiiiiillliiiiliiiiiiliiiiiiil'ijlijii;!1',!
Statutory Framework , . EIA Guidelines 'for Mining
124:,?(b)(6M.^ 'fa addition, public 'notice for a'draft''new source. NPDES
or which an EIS must be prepared cannot take place-until the draft EIS is issued [40 CFR •
Parj 124.10(b)].
' • •
!3a^^ • ;
••
EPA has established National technology-based effluent limitation guidelines for coal mining and
preparation plants (40 CFR Part 434) ami ore mining and dressing (40 CFR Part 440). National
effluent limits are based on three levels of technologies. First, Best Practicable Control Technology
Qirrendy Available (BPT) limits are based on the best existing performance (^|
plants of various sizes, ages, and unit processes hi the industry. Limits based on the Best Available
Technology Economically Achievable (BAT) control toxic pollutants (i.e., 126 chemical substances
identified by Congress) and nonconventional pollutants (any pollutant other than toxic and
conventional, POD, TSS, oil and'grease, fecal col!fbrm£ indpH] poUutiEDte)! §AT~llmits generally
represent the best existing performance hi the industry. .Finally, new source performance standards
III"™ "are based on the Best Available Demonstrated Technology (BADT), since new plants can install the
J_M —^ ^_^ egjcjenl production processes and'wastewater treatment technologies. Exhibits 6-2
« || ' H" ij'.. ' I '!• . », T,,'l| , "I , ••!'•!„ • ' f,! „ ,, ,! • ill'li, !•„ '• '">i, , j, , , , ,'" • ,
through 6-4 present the new source performance standards for coal raining and preparation plants and
ore mining and dressing facilities.
In general, standards have been established for "mine drainage" and mill/preparation plant discharges.
For coal mining, there also are standards for post-mining areas (i.e., reclamation areas prior to bond
release). For coal mining, mine drainage generally includes all point source discharges other than
those from haul and access roads, rail lines, conveyor areas, equipment storage and maintenance
yards, and coal handling buildings and structures (discharges/runoff from these areas are subject to
storm water permitting, as described below). For metal .mining, the discharges to which mine
drainage limitations apply have proven somewhat more difficult to delineate; Exhibit 6-5 provides
examples of point source discharges that are subject to mine drainage limits (and examples of those
that are subject to storm water permitting).
The National effluent limitations consist of marmnim concentrations of individual pollutants that
be present in specific discharges, as well as various conditions and exemptions; in some cases, the
effluent limitation allows no discharge. Typically, only a limited number of the pollutants that are
likely or known to be present are limited in the National standards, since the technologies on which
the limits are based prove effective in treating/removing other pollutants as well. Permit writers must
use Best Professional Judgment to develop technology-based limits for any other pollutants of
concern, and discharges, for which there are no National effluent limitations. In addition, when
technology-based effluent limits will not ensure compliance with applicable water quality standards for
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Guidelines for Mining
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Exhibit 6-5. Examples, of Discharges From Ore Mining and Dressing Facilities
That Are Subject to 40 CFR Part 440 or to Storm Water Permitting
40 CFR Fart 440 effluent limitation: guidelines,
:'' i:--::":;.: i':'':Snbjert:;td- storm-water permitting
- : t;: fact subject to40 CFRPart 440) :•-.
Mane drainage Snots
Land application area ' .
Crusher area ' '
Spent ore piles ', surge piles, ore stockpiles, waste
rock/overburden piles
Pumped and unpumped drainage and mine water from
pits/underground mines
Seeps/French drams' . .
Onsite haul roads, if constructed of waste rock or
spent ore or if waste water subject to mine drainage
limns is used for dust control
Tailings dams/dikes when constructed of waste
rock/tailings '
Unreclaimed disturbed areas
Mill discharges limits (including zero
discharge limits)
Land application area'
Crusher area' • •
Spent ore piles ', surge piles, waste rock/overburden
piles
Seeps/French drains '
Tailings impoundment/pile
Heap leach runoff/seepage • -
Pregnant, barren, overflow, and polishing ponds
Product storage areas (e.g., concentrate pile)
Topsoil piles
Haul roads not on active mining area
Onsite haul roads not constructed of waste rock or
spent ore (unless wastewater subject to mine
-drainage limits is used for dust control)
Tailings dams/dikes when not constructed of waste
rock/tailings '
Concentration/mill building/site (if discharge is storm
water only, with no contact with piles)
Reclaimed areas released from reclamation bonds prior
to 12/17/90
Partially/inadequately reclaimed areas or areas not
released from reclamation bond
Most ancillary areas (e.g., chemical and explosives
storage, power plant, equipment/truck maintenance
and wash areas, etc.)
NOTE:
1 Point source discharges from these areas .are subject to 40 CFR Pan 440 effluent limitation guidelines for (a)
mills if process fluids are present or (b) mine drainage if process Quids are not
Section §402(p)(2)(B) (added by the Water Quality Act of 1987) required that point source discharges
of storm water associated with industrial activity be permitted by October 1, 1992. Pursuant to this
requirement, .EPA's storm water program requires mat all point 'source discharges of storm water
associated with industrial activity, including storm water discharges from mining activity, be
permitted under the NPDES program. Storm water is defined at 40 CFR 122.26(b)(13) as "storm
water runoff, snow melt runoff, and surface runoff and drainage." Storm -water associated with
industrial activity is defined at §122.26(b)(14) as "the discharge from any conveyance which is used
for collecting and conveying storm water and which is directly related to manufacturing, processing,
or raw materials storage areas at an industrial plant. . . ." It also includes discharges from "areas
6-13
September 1994
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Framework
Jljj ; ' ' ' , , 11 _,,! .Jill 1 , ,
EIA Guidelines for Mining
L :! ' ' ' , f, ;
where industrial activity has taken place in the past and significant materials remain and are exposed
.. L " .I ' .' - . . ' •
to storm water/
Certain storm water discharges from mine sites, whether active or inactive, are not subject to NPDES
[[[ ! .................................................. permitting: storm wafer, that ...... is ..... not ...... contaminated ...... by contact with or that has 'not come into .contact
^•w»»:i ...... with any overburden, raw material, intermediate products, finished products, byproducts, or waste
| .................................... products located on the site of the ..... operation -is 'not subject to
' ....... Act. Also, inactive sites where there is no identifiable owner/operator are not subject to permitting
SS-HBHHf ffiSoer ..... the ..... ^orm ..... ^ater rule (however, it is not clear that any sites are actually excluded by virtue of
"" . ........ ,ll I . . i ' '
. „ , . ,|l I . . |i '
this, since there is presumably an owner of all 'lands on which sites may be located). Finally, sites on
Federal lands where claims have been established under the Mining Law of 1872 and where only
, |! i . ', ..... IB "IS • • ' ,' -,i !' ...... ; •' ' ' ,. ' ~ ... ! • ,• ,'. , J
nominal claim-holding activities are being undertaken are not subject to permitting. However, it is
..................... 1 ..... ! .......... ::" ............... ;:™ ................................ " ^^^tjE^^pTQgR^wiIl address cjajn^ ....... wn^ ...... ^ ^ me case ^ ...... ^^ ...... mere ...... fe ...... a ...... discharge of .......
............. ' [[[ j«! ....... : .............................................. J! .............. ! ..... : ......................... i ........... ;i ........... • .................... s:?- ............... : ....... : ......................................... • ............... : .................................... • ...................... ; ......................... •: ........................... : .................................... [[[ : [[[ : [[[ • ...... ; ............................................. r ............... .................... i! ........... :s ........ ..................... ......... : .............................. » .......... ' .............. i .................. "
contaminated storm water from mines abandoned by a previous claimant. Finally, NPDES permits
are not required for discharges of contaminated storm water from coal mines that have been released
btfi ....... 85 ..... iSffl ...... wttiln ..... sa ...... ..... oMLftm ...... ?pplicable
or after December 17, 1990. ......
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There ...... are ...... no ...... New ..... Source Performance Standards for storm water discharges, so the issuance of an
Ni?DES permit for storm water discharges (or the coverage by an existing permit of a new or
previously iinpermitted discharge) would not trigger NEPA. !
Section 404 of the Clean Water Act addresses the placement of dredged or fill material into waters of
Itie fj.S: and has become die principal' tool in the preservation of wetland ecosystems. "Jurisdictional'
wetlands" are those subject to regulation under Section 404. Jurisdictional wetlands are those that
|Blgg|uijitai£ aufijrig for Section 404 'is divided between'the Arary Corps- of'Engineers" (Corps)" and
EP4- Section 404(a) establishes the requirement for the Corps to issue permits for discharges of
dredged or till materials into waters of the United States at specific disposal sites. Disposal sites are
to bj:; specified for each permit using the §4O4(bXl) guidelmes; the guidelines were established by
EPA in conjunction with the Corps. Further, §404(c) gives EPA the authority to veto any of the
permits issued by the Corps under §404. In practice, EPA rarely exercises its veto power as it
typically reviews and provides comments on §404 permits prior to their issuance, and any disputes are
resolved then.
Section 404(e) establishes that the Corps may issue general permits on a State, regional, or National
, bgis, foj jglfS0™8 °f activities that the Secretary deems similar in nature, cause only
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EIA Guidelines for M"»"g Statutory Framework
comment; the pennies must be based on the §404(b)(l) guidelines and establish conditions that apply
to the authorized activity. Exceptions to §404 requirements are established in §404(f) and
conditionally include the construction of temporary roads for moving mining equipment.
The process of issuing a §404 permit begins with a permit application. The application typically
contains information describing the project and the project area; wetlands to be disturbed and the
extent; and, mitigation plans. Upon receipt of the application, the Corps issues a public notice
describing the proposed activity and establishing a deadline for public comment. Although a public
hearing is not normally held, one may be scheduled at the request of concerned citizens. Following
the comment period (typically 30 days), the Corps evaluates the application based on requirements of
the Clean Water Act. In the final stages, the Corps prepares an environmental assessment and issues
a statement of finding. A permit is then issued or denied based on the finding. It is at this time that
EPA may exercise its veto authority.
Enforcement authority is divided between the two agencies; the Corps provides enforcement action for
operations discharging'in violation of an approved permit while EPA has authority over any operation
discharging dredged or fill materials without a permit. Within EPA, the Office of Wetlands
Protection addresses wetland issues through two divisions. The Regulatory Activities Division
develops policy and regulations, and administers the statutory requirements including appeals and
determinations. The Wetlands Strategies and State Programs Division works to expand protection
and further scientific knowledge of these ecosystem types through coordination efforts with other
Federal and State agencies (Want 1990).
6.2 CLEAN AIR ACT
The Clean Air Act (CAA) (42 U.S.C. §§7401-7626) requires EPA to develop ambient air quality
standards as well as standards for hazardous air pollutants. The Act also imposes strict performance
standards applicable to new or modified sources of air pollution, a stringent approval process for new
sources of pollution in both attainment and non-attainment areas, and emission controls on motor
vehicles.
Under §109, EPA has established national primary and secondary ambient air quality standards for six
"criteria" pollutants. These are known as the National Ambient Air Quality Standards (NAAQSs).
The NAAQSs set maximum concentrations hi ambient air for lead, nitrogen oxides, sulfur dioxide,
carbon monoxide, suspended particulate matter of less than 10 microns in diameter, and ozone.
States and local authorities have the responsibility for bringing their regions into compliance with
NAAQSs or more strict standards they may adopt. This is accomplished through the development
and implementation of State Implementation Plans (SIPs), which are EPA-approved .plans that set
forth the pollution control requirements applicable to the various sources addressed by each SIP.
6-15 . September 1994
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Statutory Framework
EIA Guidelines for Mining
|!l'l ..... tinder §111, EPA has promulgated New ...... Source ..... Performance ..... Standards ..... (NSPSs) applicable to
;=:= metallic mineral-ittocessing plants (40 CFR Part ,60, SubDart ffi- ^,'lSSSSSS, ,£!§?! ,E
of^quipment fhtt produces metallic mineral concentrates from ore; metallic mineral,
commences with the mining of the ore." However, all underground processing facilities
exempt from the NSPSs. Also, NSPS particulate emission concentration standards only apply to
emissions. NSPSs require operations to contain stack-emitted particulate matter in excess of
|.Q5 grams per dry standard cubic meter (dscm). In addition, stack emissions must not exhibit
i^mti i p | HI , „ |
. ,
i^™ " , 'P i HI • in
greater man 7 percent opacity, unless the stack emissions are discharged from an affected facility
ging a wet scrubbing emission control device. However, on or after 60 days following the
achievement of the maTinum production rate (but no later than 180 days after initial startup),
operations must limit all process fugitive emissions (meaning fugitive dust created during operation
j^i^HM^J^S!!^ ..... m ..... iSfSi ..... S ....... «ffE5t,,,,?pacity' ' '
,; ..........
; '" i , i , .
In, addition to the NSPSs, Prevention of Significant Deterioration (PSD) provisions are intended to
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ensure that NAAQS are not exceeded in those areas that are in attainment for NAAQSs. Under this
program, new sources are subject to extensive study requirements if they will emit (after controls are
applied) specified quantities of certain pollutants.
State programs to meet orexceed Federal NAAQSs are generally maintained through permit programs
that limit' the release of airborne pollutants from industrial and land-disturbing activities. Fugitive
'IffcjSScions from mining activities may be regulated through these permit programs (usually by
requiring dust suppression management activities).
. ii n
As indicated above, only six criteria pollutants are currently regulated by NAAQSs. Several other
Ii:Jll^SfS ££, ,332^2! ,S2!S N.2S22?!, .SSSSiSS, SSJfeSfe!0! SSSSSflpS ^Pollutants (NESHAPs)
NESHAPs address health concerns that are considered too localized to be inchidol under the scope of
NAAQSs. Prior to the passage of me Clean Air Amendments of 1990, the EPA had promulgated
NESHAPs for seven pollutants: arsenic, asbestos, benzene, beryllium, mercury, vinyl chloride, and
"!! fadionudides (40 CFR Part 61).
BJjfft 2S — ,-S«&£&SS3SS& S£l2aS S&SSlSPy revised the existing statutory provisions of the
i^CAA; Tte Amendinents require that| States develop air emission permit programs for major sources
3S5S,2S 2HIJ2S S—21 2S! ,S2?2SaPy e^P30? *B au- toxics (i.e:, NESHAPs) program to '
'"IS^SS i§9 specific compounds. Under the Amendments, Cpngess requked ^EPA to .establish
stringent, tedinplogy-based standards for a variety of hazardous air pollutants, including cyanide
compounds. In. November of 1993, EPA published a list of source categories and a schedule for
fortfae selected sources. Among the mining-related industry groups that have been
5 sojirces of hazardous air pollutants are the ferrous and non-ferrous metals processing
;, and the minerals products processing industry (58 FR 63952; 12/3/93J. Under the
6-16
September 1994
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ETA. Guidelines for Mining . Statutory Framework
amended air toxics program, if a source emits more than 10 tons per year of a single hazardous air
pollutant or more than 25 tons per year of a combination of hazardous air pollutants, the source is
considered a "major source." Major sources are required to use the Maximum Available Control
Technology (MACT) to control the release of the pollutants (CAA §112). The CAA Amendments
also intensify the requirements applicable to nonattainment areas.
63 RESOURCE CONSERVATION AND RECOVERY ACT
The Solid Waste'Disposal Act was amended in 1976 with the passage of the Resource Conservation
and Recovery Act (RCRA)(42 U.S.C. §§6901-6992k). Under Subtitle C of RCRA, EPA has
established requirements for managing hazardous wastes from their generation through their storage,
transportation, treatment, and ultimate disposal. Hazardous wastes include specific wastes that are
listed as such under 40 CFR §261 Subpart D as well as other wastes that exhibit one or more EPA-
defined "characteristics," including reactivity, corrosivity, and toxicity. Other solid wastes (which
can be solid, liquid, or gaseous) that are not hazardous wastes are subject to Subtitle D, under which
EPA establishes criteria for State management programs, approves State programs, and can provide
funding for State implementation. EPA has promulgated specific criteria for municipal solid wastes
and more general criteria for all nonhazardous solid wastes.
The scope of RCRA as it applies to mining waste was amended in 1980 when Congress passed the
Bevill Amendment, RCRA §3001(b)(3)(A). The Bevill Amendment states that "solid waste from the
extraction, beneficiation, and processing of ores and minerals" is excluded from the definition of
hazardous waste under Subtitle C of RCRA (40 CFR §261.4(b)(7)). The exemption was conditional
upon EPA's completion of studies required by RCRA Section 8002(f) and (p) on the environmental
and health consequences of the disposal and use of these wastes. EPA then conducted separate studies
of extraction and beneficiation wastes (roughly, mining and milling wastes) and processing wastes
(smelting and refining wastes). EPA submitted the results of die first study in the 1985 Report to
Congress: Wastes from the Extraction and Beneficiation of Metallic Ores, Phosphate Rock, Asbestos,
Overburden From Uranium Mining, and Oil Shale (EPA, 1985). In July 1986, EPA made a
regulatory determination that regulation of extraction and beneficiation wastes as hazardous wastes
under Subtitle C was not warranted (51 FR 24496; July 3, 1986). EPA found that a wide variety of
existing Federal and State programs already addressed many of the risks posed by extraction and .
beneficiation wastes. To address gaps in existing programs, EPA indicated that these wastes should
be controlled under a Subtitle D program specific to mining wastes.
EPA reported its findings on mineral processing wastes from the studies required by the Bevill
Amendment in the 1990 Report to Congress: Special Wastes From Mineral Processing (EPA, 1990).
This report covered 20 specific mineral processing wastes. In June 1991, EPA issued a regulatory
determination (56 FR 27300; June 13, 1990) stating that regulation of these 20 mineral processing
wastes as hazardous wastes under RCRA Subtitle C is inappropriate or infeasible. Eighteen of the
6-17 September 1994
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Statutory Framework
EIA Guidelines for Mining
wastes are subject to applicable State requirements. The remaining two wastes (phosphogypsum and
phosphoric add process waste water) are currently being evaluated under the authority of the Toxic
SufS,tai^e?l £2552! ^S ffSCA) to^investigate pollution prevention alternatives. Five specific wastes
F*\ ffl**,** hazardous wastes and must be managed as such; other than these and the 20 wastes
exempted in 1991, mineral processing wastes are subject to regulation as hazardous waste if they
exhibit one or more hazardous waste characteristics.
EPA interprets the exclusion from hazardous waste regulation to encompass only those wastes that are
uniquely related to the extraction and beneficiation of ores and minerals. Thus, the exclusion does
aot apply to pastes ..... *itt ..... nay ..... t» ..... §enaated # a mine site ..... but ...... Oat ...... are ...... not, ..... unjquely associated with
mfapng. For example, waste solvents are listed as a hazardous waste under 40 QgR, §261 .3 1
(Hazardous '^Hastes frpni Nonspecific Sources). They are generated at mining sites as a result of
cleaning metals parts. Because this activity (and this waste) is not uniquely associated with extraction
beneficiatio° operations, such solvents must be managed as are any other hazardous wastes,
to ft, *$&* f equirements m 4° CFR Vaits 260 through 271, or State requirements if the
..... j* ...... autho nzg ..... to ....... hnDtenent ....... the ..... RCRA ....... Subtitle ...... C program. In practice, most, mine sites generate
relatively small ff111!168 of hazardous wastes. There are a few large coal and noncoal mines,
however, that generate large quantities and thus may be regulated as hazardous waste treatment,
storage, or disposal facilities. In these cases, the units in which exempt wastes are managed may be
subject to the requirements of 40 CFR §264.101, which require corrective action at certain solid
waste management units at regulated facilities. .
"sfacf ..... ,
numer o
]Ru1^^
to
........ ..... ,,,,^ ...... (OSW) ...... has ....... undertaken ...... a ................................. '
5^ programs and to enhance EPA's understandmg of the mining
|i ...... ...... environmental ingacts. .............. To ....... identi^'and'^fbcus^discussipn on the key
technical and programmatic issues of concern, ipA developed staff-level approaches to regulating
mining wastes under RCRA Subtitle D that were widely reviewed and discussed. EPA also
established a Policy Dialogue Committee under the Federal Advisory Committees Act to facilitate
discussions with other Federal agencies, States, industry, and public interest groups. Grant funding
vns iwvided to the Western <5ovemors' Association to support a Mine Waste Task Force, which has
fostered the refinement of State programs that regulate mining operations, allowed coordinated
discussions among States of mining-related issues, and commissioned a number of technical studies.
Gran^ funding also has been provided to several States for developing and enhancing mining-related
programs and to educational institutions for technical investigations.
OSW
continued its investigation of the. mining industry. EPA is currently preparing detailed
profiles of a number of mining industry sectors. These profiles are intended to represent current
extraction and beneficiation operations and environmental management practices, and applicable
Federal and State regulatory programs.
6-18
September 1994
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ELiL Guidelines for Mining . Statutory Framework
In addition, OSW visited a number of mine sites and prepared comprehensive reports on the
operational, environmental, and regulatory characteristics of the sites. Together with the profiles,
reports on visits to mines in specific industry sectors are being compiled into Technical Resource
Documents. OSW also has compiled data from State regulatory agencies on waste characteristics,
releases, and environmental effects; prepared detailed summaries of over 50 mining-related sites on
the Superfund National Priorities List (NPL); and examined a number of specific waste'management
practices and technologies, including several currently available pollution prevention practices
technologies. EPA has also conducted studies of State mining-related regulatory programs and their
implementation. Finally, EPA has undertaken a number of technical studies, including investigations
of prediction techniques for acid generation potential, tailings dam design, closure and reclamation of
cyanide heap leach facilities, and other topics. (Profiles and technical studies, currently in draft form,
were used extensively in preparing these guidelines).
6.4 .ENDANGERED SPECIES ACT
The Endangered Species Act (ESA) (16 U.S.C. §§1531-1544) provides a means whereby ecosystenii
supporting threatened or endangered species may be conserved and provides a program for the
conservation of such species. Under the ESA, the Secretary of the Interior or the Secretary of :
Commerce, depending on their program responsibilities pursuant to the provisions of Reorganization
Plan No. 4 of 1970, must determine whether any species is endangered or threatened due to habitat
destruction, overutilization, disease of predation, the inadequacy of existing regulatory mechanisms,
or other natural or manmade factors. When the Secretary determines that a species is endangered or
threatened, the Secretary must issue regulations deemed necessary and advisable for the conservation
of the species. In addition, to the extent prudent and determinable, she or he must designate the
critical habitat of the species. .
Section 7 of the ESA requires Federal agencies to ensure that all federally associated activities within
the United States do not have adverse impacts on the continued existence of threatened or endangered
species or on critical habitat that are important in conserving those species. Agencies undertaking a
Federal action must consult with the U.S. Fish and Wildlife Service (USFWS), which maintains
current lists of species that have been designated as threatened or endangered, to determine the
potential impacts a project may have on protected species. The National Marine Fisheries Service
undertakes the consultation function for marine and anadromous fish species while the USFWS is
responsible for terrestrial (and avian), wetland and fresh-water species.
The USFWS has established a system of informal and formal consultation procedures, and these must
be undertaken as appropriate in preparing an EA or EIS. Many States also have programs to identify
and protect threatened or endangered species other than Federally listed species. As noted in Chapter
2, 40 CFR 6.605(3) requires that an EIS be prepared if "any major part of a new source will have
significant adverse effect on the habitat" of a Federally or State-listed threatened or endangered
6-19 September 1994
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Statutory Framework
EIA Guidelines for Mining
I" i ! ' '"I I
species, li Federally listed threatened or endangered species may be located within the project area
*ray, be abetted by the project, a detailed endangered species assessment (Biological
[ Jgay be prepared independently or concurrently with the EIS and included as an
States may have similar requirements for detailed biological assessments as well.
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[[[ . ...... • ...... „
NATIONAL HISTORIC PRESERVATION ACT
" ' ! ill I "1 'ti ' ' ' i "
...... ilililill ..... IIIH^^^^^^ ..... II 111 ..... Illllilllllllllllil ..... Iff,!
The National Historic Preservation Act (NHPA) (16 U.S.C. §§470 et seq.) establishes Federal
programs to further flw efforts of private agencies and individuals in preserving the historical and
..... sahonzeg ....... fee ...... .estabjlshmeni ....... ofjhe ...... National ....... Register'
culttfal ...... .......
of Historic Places. J| establishes an Advisory Council oh Historic Preservation authorized.to review
and comment upon activities licensed by -the Federal government that have an effect upon sites listed
on me National Register of Historic Places or that are eligible to be listed The NHPA establishes a
National Trust Fund to administer grants for historic preservation. It authorizes the development of
regulations to require Federal agencies to consider the effects Of Federal-assisted activities on
properties included in, or eligible for, the National Register of Historic Places. It also authorizes
tt?guiations iiiaddress|n|||i State historical preservation programs. State preservation programs can be
approved where Armenmm ....... specified criteria. Additionally, Native; AmOT«m tribes may •'
assume ** fimctiorns ^ ^^ Hkto^cal Preservation Officers over tribal lands where the tribes meet
rmnfmrnn requirements. Under the Act, Federal agencies assume the responsibility for preserving
historical properties owned or controlled by the agencies.
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of amendments to the NHPA in 1980 codify portions of Executive Order 11593 (Protection
and Enhancement of the Cultural Environment—16 U,S.C. §470). These amendments require an
inventory of Federal resources and Federal agency programs that protect historic resources, and
authorize Federal agencies to charge Federal permittees and licensees reasonable costs for protection
activities. '
'
Where mining activities involve a proposed Federal action or federally assisted undertaking, or
re^u!re a license from a Federal or independent agency, and such activities affect any district, site,
biiiMing, structure, or object that is included in or eligible for inclusion hi the National Register, the
fEg 2 Hceosee 2S £« —A.dISorv Council on Historic Preservation, a reasonable
—i:! Jffi{2i2& £ 22225 i—,iregard to ** undertaking. Such agencies or licensees are also obligated
to consult .with State and Native American Historic Preservation Officers responsible for
implementing approved State programs.
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As noted in Chapter 2, 40 CFR 6.605(0X4)' ~~™1™l^u^^ ^JWTO"jJroES pennit"!"" •'
thal ^ j*vc "significant direct and adverse effec| on a property listed in or eligible for listing in the
National Register of Historic Places" triggers the preparation of an EIS. Many proposed mining
operations are located in areas where mining has occurred hi the past. Particularly in the west and
1 1
6-20
p
••••^ IIIIIIIIIIIIIIIIIIIIH Illlllllllllllllllllllll IIIIIIII 111 1111 Illlllllllllllllllllllll IIIIIIII IIIIIIII III Illllilllllllllllil IIIIIII IIIIIIIIIIIIIIII 11(111 IIIIIIII 1 1 Illllllllllllllllllllllll 1
" ' III III 1 >' 111 '
1 ,„ ' ' ;,
September 1994
i i iiiiii in in i in iiiii in 111IIIII iiiiiiiiiiiiiii i n ill in in ill iiiiiiiiiiiiiiiiii iiiii
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EIA Guidelines for Mining • • Statutory Framework
Alaska, States and localities are viewing the artifacts of past mining (e.g., headframes, mill buildings,
even waste rock piles) as valuable evidence of their heritage. Since modern mining operations can
obliterate any remnants of historic operations, care must be taken to identify any valuable cultural
resources and mitigate any unavoidable impacts. Innovative approaches are often called for and
implemented. In Cripple Creek, Colorado, for example, a mining operation wished to recover gold
from turn-of-the-centuiy waste rock piles. -As mitigation for removing this evidence of the area's past
mining, the operator replaced the piles with waste rock from their modern pit. In addition, they will
provide interpretative signs in the area for the public. -i
6.6 COASTAL ZONE MANAGEMENT ACT
The Coastal Zone Management Act's (CZMA) (16 U.S.C. §§1451-1464) seeks to "preserve, protect,
develop, and where possible, restore or enhance the resources of the Nation's coastal zone for this
and future generations." To achieve these goals, the Act provides for financial and technical
assistance and Federal guidance to States and territories for the conservation and management of
coastal resources.
Under die CZMA, Federal grants are used to encourage coastal States to develop a coastal zone
management program (CMP). The CMPs specify permissible land and water uses and require
participating States to specify how they will implement their management programs. In developing
CMPs, States must consider such criteria as ecological, cultural, historic and aesthetic values as well
•as economic development needs. Applicants for Federal licenses or permits must submit consistency
certifications indicating that their activities comply with CMP requirements. In addition, activities of
Federal agencies that directly affect the coastal zone must be consistent with approved State CMPs to
the maximum extent practicable. The CZMA also establishes the National Estuarine Reserve System,
which fosters the proper management and continued research of areas designated as national estuarine
reserves.
To the extent that mining activities are federally licensed or permitted, applicants must certify that
such activities are consistent with applicable CMPs. .
6.7 EXECUTIVE ORDERS 11988 AND 11990
Executive Orders 11988 (Floodplain Management) and 11990 (Protection of Wetlands) apply to
executive agencies that acquire, manage or dispose of Federal lands or facilities; construct or finance
construction on such lands; or conduct Federal activities or programs affecting land use. Under E.O.
11988, such agencies are required to "... avoid to the extent possible the long- and short-term
adverse impacts associated with the occupancy and modification of floodplain and to avoid direct and
indirect support of floodplain development wherever there is a practicable alternative. . ." within the
100-year flood elevation. This requires that alternatives to avoid development in a floodplain be
g_2i September 1994
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'I ! Statutory Framework
EIA Guidelines for Mining
considered and that environmental impacts be assessed. If development requires siting in a
floodplain, action must be taken to modify or design the facility in a way to avoid damage by floods.
'
'Eao. ......... MSI ....... s
possible the long-
• • •
short-term adverse impacts associated with the destruction or modification of
•
wetlands and to avoid direct or indirect support of new construction in wetlands wherever there is a
practicable alternative. .." When constructing a new facility, actions that minimize the destruction,
loss, or degradation of wetlands, and actions to preserve and enhance the natural and beneficial value
of wetlands are required. If there is no practicable alternative to wetland construction projects,
proposed actions must include measures to minimize harm. Construction in wetlands also falls under
of the Clean Water Act, administered by the U.S. Corps of Engineers.
m m
The armland Protection Policy Act (FPPA) (P.L. 97-98) seeks to
the conversion of
farmland to non-agricultural uses. It requires mat, to the extent practicable, Federal programs be
.compatible with agricultural land uses. The Act requires that in conducting agency actions Federal
agencies follow established criteria for considering and taking into account any adverse effects such
actions may have on farmland. Where adverse effects are anticipated. Federal agencies must consider
alternatives that will mitigate any harmful impacts. Under the Act, the U.S. Soil Conservation
Service (SCS) is required to be contacted and asked to identify whether a proposed facility will affect
any lands classified as prime and unique farmlands. However, beyond considering potential adverse
effects and alternatives to agency action, the Act does not provide the basis for actions challenging
IL 11 11 ihinlllil
programs affecting farmlands.
1 'I " ' J i " • '
RIVERS AND HARBORS ACT OF 1899
I ! " . ' ' • • - ' • • •
The Rivers and Harbors Act (RHA) (33 U.S.C. §§401-413> was originally enacted to regulate
obstnKtions to navigation and to prohibit the unpermitted dumping or discharging of any refuse into a
navigable water of the United States. The Act also provides authority to regulate the disposal of
dredgings in navigable waters. The provisions of §407 forbid any discharge of any refuse matter of
any kind or description whatever other than that flowing from streets and sewers in a liquid state.
Under §403, a permit^is required from the U.S. Army Corps o£Ejgineers for the construction of any
structure in or over navigable waters of the United States. Sectionp403 is usually combined with §404
of the(Clean Water Actl which addresses the discharges of fill to all waters of the United States.
Federal
63
I i i i i '
Since the passage of the Clean Water Act, the waste discharge-permitting fiuiction of the RHA has
28 P10^13111 under §402 of the|CWA. Nevertheless, some" provisions of the '
RHA, primarily Sections 403, 404, and 407, could still be used to enforce single-instance waste
navigation and anchorage.
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September 1994
w^^^^ , iiri'iiiii (iiiH^^^^^^^^^^^ i'v^^^
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EIA. Guidelines for Mining . Statutory Framework
6.10 SURFACE MINING CONTROL AND RECLAMATION ACT
The Surface Mining Control and Reclamation Act (SMCRA) addresses all elements of surface coal
operations and the surface effects of underground coal mining. The major component of SMCRA
relevant to new mining operations is Title V, which establishes a regulatory and permit program for
coal mines operating after 1977. SMCRA Title IV primarily addresses the Abandoned Mined Lands
(AML) Program, under which coal mine sites that were abandoned prior to 1977 are reclaimed.
SMCRA provides for delegation of program implementation authority to States, with State programs
overseen by the Office of Surface Mining Reclamation and Enforcement (OSM) and direct OSM
implementation in nondelegated States. To date, OSM has delegated primacy to 23 States. In
addition, three Native American tribes administer their own AML programs. OSM administers
SMCRA requirements in 13 States (most of which have no current coal production) and on all other
Native American lands. .
6.10.1 PERMTTTING PROGRAM FOR ACTIVE COAL MINING OPERATIONS
SMCRA requires permits to be issued for all active mining operations. In 30 CFR Parts 816 and
817, OSM has promulgated specific design, operating, and performance standards to ensure that
statutory performance standards are met. Special performance standards were established for: auger
mining; anthracite mines in Pennsylvania; operations in alluvial valley floors; operations in prime
farmlands; mountaintop removal;, special bituminous mines in Wyoming; coal preparation plants not
located within the permit area of a mine; and in situ processing. Some of the significant standards
covering surface and underground operations include:
• Surface Resources
Disturbed areas must be returned in a timely manner to conditions that support the land
.use(s) of the site prior to mining or to a "higher and better use." Land uses include
industrial, agricultural, fish and wildlife habitat, or combinations of land uses.
Backfilling and grading to achieve approximate original contour (AOC); AOC includes
elimination of highwalls, spoil piles, and depressions. Exceptions to AOC requirements
are permitted for mountaintop removal operations and mines that are considered to
operate hi thick or thin overburden conditions.
Exposed coal seams and combustible, toxic, or acid-forming materials must be covered
• - with a minimum of four feet of suitable material.
Reclamation/revegetation requirements include that a permanent, diverse and effective
vegetation cover of native plants be established that will support the postmining land
uses.
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Statutory Framework
EIA Guidelines for Mining
hi1'1! I II
* Water Resources
Mining should be conducted to minimize disturbance to the prevailing hydrologic
b|knc^, tp prevent long-term adverse impacts. Changes in quality and quantity of
ground and surface water must be minimized. Protection of the hydrologic system
requires that runoff from all disturbed areas (including those that have been regraded
and seeded) pass through a sedimentation pond prior to discharge. Sediment ponds
must be designed to retain at least the 10-year 24-hour precipitation event. Effluent
limitations have been established under the Clean Water Act, as discussed in Section
6.1 above.
1 » i
- jpn The groundwater recharge capacity of reclaimed lands must be restored and backfilled'
materials must be placed to minimize impacts to flow and quality of the aquifer.
- Alluvial valley floors west of the 100th meridian must be restored to their full
hydrologic function, including gradient, shape, capillary and perched water zones, and
moisture-holding capacity.
I * n
Illlll IIIH Inn i i m i i i ii i i i in i i i i n i i nn 11 in m ui <
_ Permits can be issued only if a mine can be successfully reclaimed. Along with permit applications,
• applicants must submit reclamation plans that include approaches to addressing all environment risks
identified in the application. Permit applications must be denied if the operator (or corporate
other site in the country, unabated violations of SMCRA or other environmental
affiliates) has, at
laws. In addition, permits can be denied or revoked if applicants or permittees have shown a
consistent pattern of violations, again at any site. The Comprehensive National Energy Policy Act of
1992 provided for an^era^dmj&cm die 'permit prohibition process' at SMCRA" §510(c). ' 'This'
iiiiiiiiiiiiinnnnniiiiiiiinininn iiiiiiii iininiinnni iiniinn
| . ' .... | | i • ,i' •»" , HI • , , • ,r ' , i,1 i' , ',',, . ', i' ' , i ,,|| j,, •
exemption specifically iapplies to authorized reininuig sites where vjplatipns of permit conditions occur
due to "unanticipated events." The exemption does not preclude the permitting authority from taking
other enforcement actions, however.
i, 1
SMCRA specifically requires that discharges to surface waters be in compliance with applicable State
^and Ifcdera] wate^ quality regulations and the coal mining effluent -guidelines at 40 CFR Part 434.
Several of the design reqmreinents under 30 CFR Part 816 also pertain to controlling discharges from
active mining areas. Permittees are specifically required to design and install sediment/siltation
control measjues that represent the "Best Technology Currently Available (BTCA)." For sediment
control, BTCA originally consisted of controlling discharges from disturbed areas through
sedimentation ponds. This uniform approach was challenged and BTCA determmatipns are now made
on a case-by-case basis.
il iiiiiii n in n mill n iii||iiiiiiiil|iiiiiiiiiiilliii
SMCRA requires reclamation bonds for all sites. The basic requirement is a bond for the full cost of
site reclamation, although "OSM can approve alternative bonding approaches if they are deemed
adequate. Alternative approaches such as fixed amounts per acre disturbed have been adopted by
some, States.
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6-24
September 1994
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n - In
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EJA Guidelines for Mining Statutory Framework
In practice, reclamation plans and bonding requirements have emphasized land restoration (i.e.,
recontouring and revegetation) rather than water quality issues (except for impacts from erosion).
Following reclamation and full bond release, any point source discharges of pollutants remain subject
to NPDES permitting. However, NPDES permits have not generally been required following
reclamation and bond release (i.e., after discharges are not subject to effluent guidelines). The
NPDES storm water program has followed this lead: sites that have been reclaimed after SMCRA's
enactment are not subject to the program. Lusome cases, operators have forfeited bonds that were
inadequate to reclaim sites (and to address water quality). The responsible party for any remaining
discharges is a matter of some contention at the present time; under the storm water program, the
owner of the site would be responsible for obtaining a permit for point source discharges of
contaminated storm water.
A limited exception to EPA's 40 CFR Part 434 effluent guidelines was provided in the Water Quality
Act of 1987, which allows modifications to the National technology-based limits in cases where
remining abandoned sites will result in the potential for improvement of water quality. Where such
exemptions are granted, technology-based limits are based on the permit writer's best professional
judgment. Limits on pH, iron, and manganese cannot exceed the levels discharged prior to remining;
discharges also cannot violate applicable water quality standards and criteria under §303 of the Clean
Water Act. Pennsylvania is notable for having used this provision to encourage remining of problem
sites, and other States are increasingly using or considering the provision.
It should be noted that certain provisions of SMCRA and the Clean Water Act may provide
disincentives to remining abandoned coal sites. For example, neither SMCRA standards nor the
effluent limitation guidelines established under the Clean Water Act distinguish between remining
previously abandoned sites and mining undisturbed land (except as noted above). To the extent that
there is a greater potential for noncompliance at remining sites (e.g., because of greater complexity or
unpredictability of the hydrogeologic regime), the "permit block" provisions of SMCRA (§510(c))
could be a disincentive to remining: failure to comply with an NPDES permit can prevent die
operator from obtaining future SMCRA permits. The relative stringency of water quality standards,
particularly forpH, also may prevent operators from remining sites, since permits must provide for
attainment of water quality standards and criteria, notwithstanding any prior nonattainment. (To the
extent that water quality standards and criteria act as a disincentive to remining, this may increase as
numeric criteria are established for an increased number of toxic pollutants hi response to the 1987
amendments to §303.)
6.10.2 ABANDONED MINE LANDS PROGRAM
Title IV of SMCRA established the Abandoned .Mine Lands (AML) Program to provide for
reclamation of mine sites abandoned prior to 1977 (the date of enactment). The program was
subsequently amended to allow the expenditure of funding to reclaim post-1977 operations where an
6-25 September 1994
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1 iiiiiiiiiii iiiiiiiiiiii iii iiiiiiiiiii iifi iiin^^^ iiiiiiiii 'iiiipn
Statntoiy Framework ; EIA Guidelines for Mining
I ! : if 1 ; : ! - ' : i; ! ! : :
abandonment occurred between 1977 and the date of State program approval and the
reclamation/abatement bond was not sufficient; or where a surety provider became insolvent and "
available funds were not sufficient to reclaim the site. The AML program is supported by the
Abandoned Mine Reclamation Fund. The fund receives reclamation fees paid by active mining
operations: for lignite coal, the contribution to the fund is IOC per ton; for other coal, the fee is 150
per ton of coal from underground ^^ ^j |^ per.ton ,,g|,,,,s^ac^rnine coal. The fund is currently '
authorized to collect fees through the year 2004. '
6.11 MINING LAW OF 1872
™' ~ ..... ' .....
...... ...... , ..... ....... 22 ....... 2;2£,; ......... ,11, ....... .....
United States can explore and purchase mineral deposits and occupy and purchase the lands on which
such claims are located. The basic provision of the law provides that:
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Except as otherwise provided, all valuable mineral deposits hi lands belonging to the
U.S . ........ g ......... g ....... shall ...... Jg ...... fteg ..... and ...... open to exploration and purchase, and the lands in which they
1 iigg ..... igSSsfi ...... SSSS3&&* ..... and-puidiase, by citizens of the, U.S. . •. . under regulations •
prescribed by law, and according to the local customs or rules of miners hi the several
mining districts, so far as the same are applicable and not inconsistent with the laws of the
U.S. • ' >.,.,, ...... ;,
!» . • . • ' ! ,. • '" I , ' :•••'.
e Mining Law establishes the basic standards for the location, recordation, and patenting of mining
..Claims, cneral, ....... Persons ....... «[e ...... authorized ..... to ...... enter ..... Federal ....... lands ....... and ...... establisJi ...... gr ...... locale, ..... i ...... cjajm ..... to a
IS* ,5°.w, ,§, SISSl/SojS, JSSlSSd Somber, as
............... SSSm ..... 1 ..... illi ..... ii§ ...... 1&&SSSS& ....... JSS??, ....... &5i ....... SEES ........ !,?I5s ........ FS-oided ...... Hlltl ...... 1LM), the
fns: ..... a j»ss«Kigrxgt ..... to ^.laml fi« i£urposes_ rf mine^ devdogmait and ,1161631161;
e ...... clSn ...... fsmall ....... amounts ....... p| devdppment work'is done or small fees are paid. Upon proving
that a valuable mineral deposit has been discovered (this proof must meet regulatory standards), claim
holders may -patent the claim and purchase Ae land for riom^ sums. Except as specifically
authorized by law (e.g., certam mholdmgs), land management agencies have no further jurisdiction
ove£ j^d kads- MffSi t*??05' whether patented or not, are fully recognized private interests
* 55EE1!5! ...... S ...... SSlES! ..... IP^Y^te, P10?6^ subject . to Fifth
'
....... ..... ...... ..... iij ..... a ............. ..... , ...... ...... ...... ..... , .
....... 'Amendment jixotectira .against tal^gs by the United States without just compensation. .' The standards
set in the Mining law may be supplemented by local%law not hi conflict with the Mining Law or State
YMW*
law.
, .
yarious^ws have resoicted the minerals that are subject, to location, under the Mining
Law; restrictions were generally not retroactive but were subject to valid existing rights. "Locatable"
minerals subject to location "of claims undgr the Mining Law now include most metallic mhierals
(except uranium) and some nonmetallic minerals. In addition, certain Federal lands have been or may
to mineral development, subject to valid existing rights (these include the National Parks
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EL4 Guidelines for Mining Statutory Framework
and National Monuments, among, other lands). In addition, only "public domain" lands are generally
open to mineral location under the Mining Law.
Only since 1976 have claimants been required to record claims with BLM. Through the end of fiscal
year 1991, more than 2,700,000 claiiris had been accepted for recording by BLM. Of these, more
than 1,500,000 had been abandoned, relinquished, or rejected, leaving more than 1,100,000
unpatented claims on Federal .lands. The number of claims on which significant prospecting or
mining occurred prior to 1976 is simply unknown, since there were no reporting (and few other)
requirements at the time.
6.12 FEDERAL LAND POLICY MANAGEMENT ACT
The Federal Land Policy Management Act (FLPMA) (43 U.S.C. §§1701-1782) provides the Bureau
of Land Management with authority for public land planning and management/ and governs such
disparate land use activities as range management, rights-of-way and other easements, withdrawals,
exchanges, acquisitions, trespass, and many others. FLPMA declares it to be the policy of the United
States to retain lands in public ownership (i.e., rather than "disposing" of the lands by transferring
ownership to private parties) and to manage them for purposes of multiple use and sustained yield.
Under §202, BLM must develop and maintain plans for the use of tracts or areas of the. public lands.
To the extent feasible, BLM must coordinate its land use planning with other Federal, State, and local
agencies. BLM also must provide for compliance with "applicable" pollution control laws (including
Federal and State air, water, and noise standards and implementation plans) in the development and
revision of land use plans. The overall protective standard is provided in §302(b), under which BLM
is to take any necessary action, including regulation, to prevent "unnecessary or undue degradation"
of public lands. Subject to this and several more limited exceptions, nothing hi FLPMA "shall in any
way amend the Mining Law of 1872 or impair the rights of any locators of claims under that Act,
including, but not limited to, rights of ingress and egress" (§302(b)).
BLM regulations (43 CFR Group 3800) impose a number of broad requirements upon operations on
mining claims on BLM-managed lands, but contain few specific technical standards.' The basic
compliance standard is that operations must be conducted so as to prevent unnecessary or undue
degradation of the lands or their resources, including environmental resources and the mineral
resources themselves. According to 43 CFR §3809.0-5(k), "unnecessary or undue degradation"
means surface disturbance greater than what would normally result when an activity is being
accomplished by a prudent operator in usual, customary, and proficient operations of similar character
and taking into consideration the effects of operations on other resources and land uses, including
those resources and uses outside the area of operations. Failure to initiate and complete reasonable
mitigation measures, including reclamation of disturbed areas, may constitute unnecessary or undue
degradation. Finally, failure to comply with applicable environmental protection statutes and
regulations constitutes unnecessary and undue degradation.
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Statutory Framework
EIA Guidelines for Mining
's implementing regulations pertaining to development of mining claims include three levels of
review:
Casual use—for which no notification or approval is necessary
r" ! ~ ! : " : " ; ' :' : : "" ' "" : ,u : : ' i i ! ' :
Notice-level—for cumulative annual disturbances total less than five, acres. Operators must
notify BLM officials (and commit to reclamation), but no approval is required.
Consultation may be required if access routes are to be constructed.
Approval-level—for disturbances exceeding 5 acres hi a calendar year or hi certain
specified areas (wilderness areas, wild and scenic rivers, .critical, .habitat, areas of the
DeseS Conserotion Areg. Operators must obtain BLM approval (within
gf - pjan of Operations for such operations. ' • "
be taken to prevent undue and
te ...... and ...... &e.proj»sed operation, deluding measures
salvaging topsoil for later use, erosion and runoff control, toxic
":'l!i|l|ll :i':"jii|ij I'll .'SIIIS11-! HI .|, i|L< ifi • f , , i .. , , , „,. , |,,f, , , „,, „ ,T ,„ , ' ,
il, and reegetation (where
require operators to furnish bonds (site-specific or blanket) or cash
" f jii '' ! ='! J i"" i" ' , i,'''"'', i : •••',• : " iii," "* ' - i. . ' , , •• •*.,
deposits, with-the amount left.to die responsible official (policy now calls for full reclamation bonding
for cyanide and other chemical leaching operations, and a similar policy is anticipated to be issued hi
• for potentiallv acid-generating mines). Following approval of a plan of operation, BLM may
an to ensure that the approved plan is being followed. Failure to follow approved
f^i.^^^^ £?£|>«ations, or to reclaim lands; may result hi a notice of noncompliance, which hi turn can
may be modified at BLM's .request or at the... operator's behest. . Significant
of
are reviewed ...... by BLM "hi e context of the requirement to prevent
e for 'reasonable reclamation^ ........ (|3809.1^(a)). Wubin
tbe plan
» cnan
Plan
EsZ re^uired fot review; that the pjmramot ..... be ...... approved until
EPA; dr that the plan cannot be approved, until BLM complies
Endangered Species Act or National Historic Preservation Act or consults with other surface
managmg agencies. (Should cultural resources be discovered during an inventory, BLM is
responsible for any costs of salvage that may be necessary.)
, = y2£3!!i fiflisgEEi.Pj3!! °! PI?*3!!?!!? |°I piodjf|ca||o:n),> BLM must ojnduct .an, .enyjroninen|al '
i£^^^^O^ sup|)!eii5iO. this EA| is used to ..assess the adequacy of proposed .mitigation measures
^ti& reclamation procedures to^pjev^unnej^sary and undue degradation.. The EA then leads to a
I^JjjjJ3S| ^^.S^Sg liili S?H °r: ^l°M llE^iSEl S,,!2 fclS3^?.,^30,?1?,3^
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EIA Guidelines for Mining. "" Statutory Framework
Record of Decision. If the proposed operation is to be issued a new source NPDES permit and is in
a State where EPA is the permitting authority, or if in other cases where EPA has significant
environmental concerns, EPA typically becomes a cooperating agency in the NEPA process.
There are a number of issues related to plans of operations and BLM regulatory oversight that bear
noting. For example, plans of operations themselves become the "permit" to which operators must
adhere. These are often enormous multi-volume documents that reflect the uncertainties of mining:
they often note multiple contingencies in the event that specific conditions are found or develop.
Detailed descriptions of planned operations under each contingency are not generally feasible (and are
certainly not economic). As a result, plans provide appropriate caveats that additional plans,
consultations, studies, or modifications will be made if necessary. It is not practical to modify plans
of operations with every such change, and even when plans are formally modified, they often address
only the modification, not the entire operation. Thus, a mine that evolves over time, as most do,
comes to resemble the original plan less and less, and determining exactly which modification
addresses a particular mine component can be extremely difficult. In addition, BLM administration of
its regulations is very decentralized, with State offices and local resource area offices generally
responsible. This recognizes the site- and region-specific nature of the mining industry, and its
environmental impacts, but has led to inconsistency in several areas, including the level of
"significance" that triggers preparation of an environmental impact statement. Environmental impact
assessments (whether in EAs or EISs) follow the same pattern as plans of operations: they often
address the plan or modification at hand, not necessarily the entire mining operation as it has grown
and evolved over time. Finally, BLM considers itself extremely constrained by the Mining Law;
there is no provision for BLM disapproval of proposed plans of operations, only the prevention of
unnecessary and undue degradation of public lands.
6.13 NATIONAL PARK SYSTEM MINING REGULATION ACT
The National Park System Mining Regulation Act (also known as the Mining hi the Parks Act, or
MPA) (16 U.S.C. §§1901-1912) reconciles the recreational purpose of the National Park System with
mining activities affecting park lands. The Act subjects mining activities within the National Park
System to such regulations as deemed necessary by the Secretary of the Interior. It also required that
all mining claims within the park system be recorded by September, 1977, or become void.
The National Park Service has extensive regulations governing exercise of valid existing mineral
rights (36 CFR Part 9 Subpart A). The regulations restrict water use, limit access, and require
complete reclamation. They also require that operators obtain an access permit and approval of a
plan of operations prior to beginning any activity. A plan of operations requires specific site and
operations information, and may require the operator to submit a detailed environmental report.
Operators must comply with any applicable Federal, State, and local laws or regulations.
4
6_29 September 1994
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; IP ;i ; ; ) ; i •; ; ;
Statutory Framework
EIA Guidelines for Mining
1? MULTIPLE USE AND SUSTAINED YIELD ACT; NATIONAL
FOREST MANAGEMENT ACT
The Organic Act of 1897 (16 U.S.C. §§473-482, 551) has governed the Forest Service's activities
Sge fhe SSliSSf, ^y8 of National Forest management. The Act delegated broad' authority over
visually all forms of use hi the National Forest System. It also provides for continued State
jurisdiction over National Forest lands. Finally, it declares that forests shall remain open to
* prospecting, location, and development under applicable laws, and that waters within the boundaries
of the National Forests may be used for domestic mining ami milling, among other uses.
The Multiple Use and Sustained Yield Act of 1960 (MUSYA) (16 U.S.C. §§528-531) establishes that
the National Forest System is to be managed for outdoor recreation, ranee, timber, watershed, and
I IIIIIIIIBIIIIIIIIIIIIIIIIIIIIII '!" ''l I I I II i , i in a i ' '
• and wildlife purposes, and that these purposes are supplemental to the purposes for which the
forests were .established as set forth in the Forest Service Organic Legislation (16 U.S.C.
1§475,477, 478, 481, 551). MUSYA provides that the renewable surface resources of the national
are tQ,be administered for multiple use and sustained yield of products and services. Nothing
":^—:i& MUSYA J8 ^ea^' to affect the use or administration of the mineral resources of the national
forest lands. (16 U.S.C. §528). Section 530 of the MUSYA authorizes the Forest Service to
IBB^I I ' I I II I . * I i I I I 11 I I I III | I I
cooperate with State and local governments in managing the National Forests. MUSYA is
implemented by the Secretary o| —^i^^^ —^ Nat.onaj porest Management Act of 1976 provides
the .Forest Service with authorities and responsibilities similar to those provided to BLM by FLPMA.
It establishes a planning process for National Forests that hi many ways parallels the process
gt&Iished under FLPMA. for BLM lands.
1 ' i
Ililtli 'I "I iilllli '
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25 ..... £2 ..... 22 ...... 22
few
,
IgSfic technical standards. In all cases where the land's surface is to be disturbed, operators must
ijiii ................................... I i ^^ i I II f
file a notice of intent. For significant disturbances (i.e., where mechanized equipment or explosives
.............. .................... •• ...... Jll | I II III III II llll ............... I ....................... ................... ami [[[ limill! ..... I .................................. ••"* ................ *C ..... m ..... [[[ ' .............................. ". .,
are to be used), ....... operators ..... must submit ..... a proposed plan of operations. Forest Service regulations
ing plans of operations and then* review and approval, reclamation standards, and
review are similar to thosetdescribed "fm gy ...... ............... £jj |BLM'si'iiregulations, they
|i
require compliance with the Clean Water Act and other environmental statutes and regulations.
Ull 111
MINERAL LEASING ACT; MINERAL LEASING ACT FOR ACQUIRED LANDS
iiiiiiiii
|Minena Leashig Act of 1920 (MLA) (30 U.S.C. §§181-287) and the Mineral Leasing Act for
Lands (1947) (30 U.S.C §§351-359) created a leasing system for coal, oil, gas, phosphate,
lid pertain other fuel and chemical minerals ("leasable" minerals) on Federal lands. In addition,
Sectpn 402 of Reorganization Plan No. 3 of _ 1946 (and other authorities) au&orizes leases for
minerals on certam ks : (e .g., some acquured lands, as opposed to public domaui lands).
-------
EIA Guidelines for Mining , Statutory Framework
mineral development. The Department of the Interior has promulgated extensive regulations
governing various aspects of leases. BLM may issue competitive, noncompelitive, and preference
right leases that set the terms, including environmental terms, under which mineral development can
take place. Prior to lease issuance, BLM must consult with the appropriate surface managing agency
(e.g., the Forest Service), and for acquired lands must have the written consent of the other agency.
Regulations require compliance with Federal and State water and air quality standards, and failure to
comply witn lease terms can result in lease suspension or forfeiture. At the end of fiscal year 1991, a,
total of 69 nonenergy mineral leases (more than 49,000 acres) were in effect; hi addition, there were
475 coal leases in effect, covering nearly 700,000 acres of public domain and acquired land.
6.16 COMPREHENSIVE ENVIRONMENTAL RESPONSE, COMPENSATION, AND
LIABILITY ACT
The Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) (42
U.S.C. §§9601-9675) established the Superfund program to deal with releases and threatened releases
of hazardous substances to the environment. CERCLA provides funding and enforcement authority
for Federal and State clean-up programs at thousands of sites throughout the United States that are
contaminated due to the release of specified hazardous substances. The statute establishes notification
requirements for releases of hazardous substances in reportable quantities (RQs), provides abatement
and response authorities for situations where a substance or pollutant may present an imminent and
substantial danger to the public health or welfare, requires the development of a National Contingency
Plan (NCP) designed to provide for consistent and coordinated responses (both removal and remedial)
to hazardous substance discharges, and creates a Hazardous Substance Response Trust Fund
(Superfund) to pay for emergency removal actions and long-term remediations at abandoned sites
where liable parties cannot be identified. CERCLA establishes that owners and operators of
contaminated sites, as well as waste generators and others who were responsible for waste disposal
and waste transportation are subject to strict, joint, and several liability for response costs and natural
resources damages. The statute also establishes site cleanup standards.
Over 52 mining- and mineral processing-related sites are currently on the NPL, including some of the
largest and most complex of all NPL sites. The cleanup standards applied to specific NPL sites are
determined on a site-specific basis, following detailed studies of the site, the potential and actual risks,
and possible remedial actions. Because the United States is the land owner at several of the mining-
related NPL sites, Federal agencies are responsible persons in some cases..
It should also be noted that several Federal courts have addressed the issue of whether mining wastes
are "hazardous substances" under CERCLA, and thus whether mining sites where releases of mining
wastes occur are subject to CERCLA removal or remedial actions. The basic question is whether the
exemption of mining wastes from regulation as hazardous wastes under RCRA excludes them from
the definition of "hazardous substance" in §104(14). In Eagle Picher Industries v. EPA (245 U.S.
6-31 September 1994
-------
I IIIIIHI lilii'll Ill11'' liliil 1L. •- •- —
Statutoiy Framework
EIA Guidelines for Mining
. D.C. 196, 759 F.2d 922 (D.C. Cir. 1985), it was determined that mining wastes exempt from
waste Regulation ..... w,e,E ...... H!§5! ..... §£ ..... CERCLA ...... definition ...... of hazardous ....... substances. There has
been additional judicial consideration of this issue, with the decisions generally consistent with the
Eagle Picker decision.
I . ' i • .
I I II II |l|llll|ll 111 111 I ill ill IH (IIIIIIH 111 II 111 I I 111 , 1111 111 1(11 II I III 1 1 lllllIH 1
Issuance of an N^P permit for a discharges) from a new source mming operation can exclude the
operator from potential CERCLA liability. New operations are often located in historic mining
districts, where CERCLA action may be ongoing or could occur in the future. . In such cases, the
ievfeWCT'4c$liij?e ^P^iaNy cautious that the project will not further degrade water quality
(mcluding sediment) and that water quality-based InTUte/requirements are included in the NPDES
permit. Further^ prior to operation of me new source, adequate baseline data should be available to
"23$ ...... Hill ....... mmbnize. ....... any uncertainty
to the sources of pollutant levels (PRPs versus the non-liable new operator).
6.17
PLANNING AND COMMUNITY RIGHT-TO-KNOW ACT
The Emergency Planning and Community Right-to-Know Act (EPCRA) (42 U.S.C. §§11001-11050)
requires States to establish emergency response rommissions and emergency planning districts as well
as local emergency planning committees. These planning groups must prepare and review emergency
plans. The Act ako gqunes that owners and opentan of facilities who must su|Mn|t_materials .safety
__ .i__ « .. - . , ^ Health ^^ (OSHA) must
these hazardous substances to the local ...... emergency ..... planning ...... conraittee, ...... the ...... State ...... emergency response
commission, and the local fire department. Mining operations must report on chemical storage and
use, and on spills or releases, to these entities.
EPCRA also requires feculties mat
report
, ........ Piprocess ....... certain ..... listed ...... toxic ...... chemicals to
eased ..... to ..... the ..... environment ...... on ..... an annual basis,. These data
comprise the Toxics Release Inventory, or TRI. TRI reporting requirements apply to manufacturing
fecmtics m Standard Industrial CJassfficatipns (SIC) Codes 20 through 39. Mining operations are not
whfairt these SIC codes and thus are not subject to TRI reporting. However, it should be noted that
i«* ~t „». i j *—-. _, of feciiities required to report releases are currently being
...... ...... .......
expanded or considered for expansion by EPA.
i
6.18 WELD AND SCENIC RIVERS ACT
If .
The TjVild and Scenic Rivers Act of 1968 (16 U.S.C. 1273 et seq.) provides that «[c]ertain selected
rivers . . . shall be preserved in a free flowing condition, and that they and then- immediate
*aivifoliments ska1} ^ protected for the benefit and enjoyment of present and future generations.;'
Section 7 of the Act prohibits the issuance of a license for construction of any water resources project
that \yould have a direct adverse effect on rivers (or reaches of rivers) that have been selected on the
lillliNllliL '(niiillili IIIIIIH
'
6-32
September 1994
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EIA Guidelines for Mining ' _ _ Statutory Framework
basis of their remarkable scenic, recreational, geologic, fish and wildlife, historic, cultural, or other
similar values for the National Wild and Scenic Rivers System.
The System includes rivers and streams placed in the System by acts of Congress and rivers that have
been studied and deemed to be suitable for inclusion. Any potential impacts on rivers and streams in
the System must be considered, and direct adverse effects on the values for which the river was
selected for the System must be prevented.
States also have their own systems for protecting rivers and streams or portions thereof. While EPA
has no legal requirement to' consider State-protected wild and scenic rivers and streams, any potential
impacts to such areas should nevertheless be considered and addressed.
6.19 FISH AND WILDLIFE COORDINATION ACT
The Fish and Wildlife Coordination Act of 1934 (16 U.S.C. 661 et seq., P.L. 85-624) authorizes the
Secretary of the Interior to provide assistance to, and cooperate with, Federal, State, and public or
private agencies, and organizations in the development, protection, rearing, and stocking of all species
of wildlife, resources thereof, and their habitat. The majority of the Act is associated with the
coordination of wildlife conservation and other features of water-resource development programs.
6.20 FISH AND WILDLIFE CONSERVATION ACT
The Fish and Wildlife Coordination Act of 1980 (16 U.S;C. 2901 et seq.) encourages Federal
agencies to conserve and promote conservation of nongame fish and wildlife and their habitats to the
extent possible within each agency's statutory responsibilities. The Act places no
affirmative requirements on Federal agencies.
6.21 MIGRATORY BIRD PROTECTION TREATY ACT
The Migratory Bird Protection Treaty Act (16 U.S.C. 703-711) prohibits the killing, capturing, or
transporting of protected migratory birds, their nests, and eggs. Consultations with the Fish and
Wildlife Service are encouraged if project activities could directly or indirectly harm migratory birds.
6-33 September 1994.
-------
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EIA Guidelines for Mining . . References
7. REFERENCES
Adamus, P.R., EJ. Clairain, Jr., R.D. Smith, and R.E. Young. 1987. Wetlands Evaluation
Technique (WEI); Volume U: Methodology. Operational Draft Technical Report Y-87-_, U.S.
Army Corps of Engineer Waterways Experiment Station, Vicksburg, MS.
. Ahsan, M.Q., et al. 1989. "Detoxification of Cyanide in Heap Leach Piles Using Hydrogen
Peroxide." In World Gold, proceedings of the First Joint SME/Australian Institute of Mining
and Metallurgy Meeting. R. Bhappu and R. Ibardin (editors).
Alaska Department of Environmental Conservation. 1986. A Water Use Assessment of Selected
Alaska Stream Basins Affected by Gold Placer Mining. Prepared by Dames & Moore, Arctic
Hydrologic Consultants, Stephen R. Braund and Associates, L.A. Peterson and Associates, and
Hellenthal and Associates. . •
Alaska Department of Environmental Conservation.. 1987 (March). Placer" Mining Demonstration
Grant Project Design Handbook (prepared by L. A. Peterson & Associates, Inc.). Fairbanks, .
AK.
Alaska Miners Association. 1986. Placer Mining - A Systems Approach. Short Course, Alaska
Miners Association Eleventh Annual Convention, October 29-30, 1986. Anchorage, Alaska.
Altringer, P. B., R.H. Lien, and K.R. Gardner. 1991. Biological arid Chemical Selenium Removal
From Precious Metals Solutions. Proceedings of the Symposium on Environmental
Management for the 1990s, Denver, Colorado, February 25-28.
Argall, G.O., Jr. 1987 (December). "The New California Gold Rush." Engineering & Mining
Journal' 30-37. -
Arizona BADCT Guidance Document for the Mining Category, Draft Guidance Document. 1990.
Arizona Revised Statute 49-243 B.I., For Permitted Facilities Utilizing BADCT.
ASARCO. 1991 (February 4). Ray Unit Tailing Impoundment Alternative Analysis. Appendix
11.19. Submitted to EPA Water Management Division Region K Wetlands Program.
Beard, R.R. 1987 (March). "Treating Ores by Amalgamation." Circular No. 27. Phoenix, AZ:
Department of Mines and Mineral Resources.
Beard, R.R. 1990 (October). The Primary Copper Industry of Arizona in 1989. State of Arizona
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Biswas, A.K., and W.G. Davenport. 1976. Extractive Metallurgy of Copper. Pergamon
International Library, International Series on Materials Science and Technology Vol 20
Chapter2. '
Boyle, R.W. 1979. The Geochemistry of Gold and Its Deposits. Canada Geological Survey Bulletin
280. Canadian Publishing Centre. Hull, Quebec, Canada. 584 pp.
7-J September 1994
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EIA Guidelines for Mining
Bradham, W. S., and F. T. Caruccio. 1990. A Comparative Study of Tailings Analysis using Acid/
Base Accounting, Cells, Columns and Soxhelets. Proceeding of the 1990 Mming and
Reclamation Conference and Exhibition, Charleston, WV.
Brady etal. 1994. EvaluationofAcid^aseAccounting to Predict the Quality of Drainage at Surface .
Coal Mines in Pennsylvania, U.S^A. In the Proceedings of the International Land Reclamation
and Mine Drainage Conference and Third International Conference on the Abatement of Acidic
Drainage,' April' 24r29.
British Columbia AMD fask Force! 19891 "A^RockDn^ag"e Draft Tedudcal Guide, y~J~^"}-
and U. Report 66002/2. Prepared for the British Columbia AMD Task Force by SRK, Inc.
British Columbia A||D Task Fpjces 1990 (August). Monitoring Add Mine Drainage. Prepared by
E. Robertson in association with Steffen Robertson and Kirsten (B.C.) Inc. Bitech Publishing,
Richmond, British Columbia. , ' ' \]
Britton, S.G., ,19923. Mine Exploitation, in SME Mining Engineering Handbook, 2nd Edition (H.L.
Hartman, ed.). Society for Mining, Metallurgy and Exploration, Inc. Littleton, CO.
Britton, S.G. and G.T. Lineberry. 1992b. "Uj^rgnu^Mn^D^lppment," in SME Mining
Engineering Handbook, 2nd Edition (ZLL. Hartman, ed.). Society for Mining, Metallurgy and
Exploration, Inc. Littleton, CO. ' ' ' ^
Brodie, M. J., L. M. Broughton, and Dr. A. MacG. Robertson. 1991. A Conceptual Rock
" ' ' ^i^Cjeasification System for Waste Management and a Laboratory Method for ARD Prediction
1 •• |l«jRnom Rock^ files. IB Second International Conference on the Abatement of'Acidic Drainage.
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Quebec. ' . '
Broughton, L. M. and Dr. A. MacG. Robertson. 1,992. AqdR^Drajnage From Mines - Where •
Are WjeJJQjv., §tefFej|t Roberteon, and Kirsten, Vancouver, British Columbia. Internal Draft
Paper. ' ' ' " ' ' ^ •
Bruynesteyn, A. and R. Hackl.' 1982. "Evaluation of Acid Production Potential of Mming Waste
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California Mining Association. 1991. Mine Waste Management. Edited and Authored by Ian
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7-2
September 1994
"£=5 ! ii!""!i: U
iiiiinwiiiiiiwnw^^ iiiiiiiiiiiiniw|innn i
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EIA. Guidelines for Mining ' • References
California Regional Water Quality Control Board. 1993 (January 19). Personal communication
between Richard Humphreys and Joe Kissing, Science Applications International Corporation.
Falls Church, VA.
Clark, W.B. 1970. Gold Districts of California. California Division of Mines and Geology,
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Coastech Research Inc. 1989.- Investigation of Prediction Techniques for Add Mine Drainage.
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Cohen, Ronald R.H. and Staub, Margaret W. 1992 (December). Technical Manual for the Design
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Colorado Department of Natural Resources. 1992 (March). Guidelines for Cyanide Leaching
Projects. Mined Land Reclamation Division.
Cravotta, F. T. et al. 1990. Effectiveness of the Addition of Alkaline Materials at Surface Mines in
Preventing or Abating Add Mine Drainage: Parti. Theoretical Considerations. ID.
Proceedings of the 1990 Mioning and Reclamation Conference and Exhibition, April 23-26.
Gumming, A.B. (Chairman of Editorial Board). 1973. SME Mining Engineering Handbook. Society
of Mining Engineers, AIME. New York, New York.
Dadgar, A. 1989. -Extraction of Gold from Refractory Concentrates: Cyanide Leach vs. Bromide
Process." Presented at the Metallurgical Society Annual Meeting. Las Vegas, NV. February
27-Marcti 2, 1989,
Day. 1994. Evaluation of Add Generating Rock and Add Consuming Rock Mixing to Prevent Add
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29. .
Devuyst, E.A., et al. 1990 (September). Inco's Cyanide Destruction Technology. Preprint No. 90-
406. Littleton, CO: Society For Mining, Metallurgy, and Exploration, Inc.
Dietz et al. 1994. Evaluation of Acidic Mine Drainage Treatment in Constructed Wetland Systems.
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Doe Run Company. 1990 (February). Fletcher Project: Application for Metallic Minerals Waste
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1, 1990. Littleton, CO: Society for Mining, Metallurgy and Exploration, Inc.
7.3 September 1994
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-_ : . EIA Guidelines for Mining
•lllM IIIIIII IIIIIIIH « IIIIIII III III ll|ll l|llllllllllllll|lllllll 111 11111,1 II Illlllllll l|lllllll||l Illllllllll IIII II 111 I II III lllllllll III II lllllllll III 111(111|11111 lllllllll I lllll| IIIIIII 111 lllll|lllll IIIIIII 111 I II IIIIIII I lllllllll II III III IIIIIII 11111)1)1 IIIIIII I 111 I lllllllll 111 II l ll||l
Dunca^D.andC.Walden. 1975. Prediction of Acid Generation Potential. Report to Water
Pollution Control Directorate, Environmental Protection Service, Environment Canada
! 4- - " ' '
Durkin,T.V. 1990. Neutralization of Spent Ore from Cyanide Heap Leach Gold Mine Facilities in
Me Black Hills ofSouth Dakota -Current Practices and Requirements. AIME's Proceedings of
the 4th Western Regional Conference on Precious Metals and the Environment,'Lead. South
Dakota.
„ -^- —aan
\Redamation Program: 19774983. MN Dept. Nat. Res., Division of Minerals, St. Paul, ML
Egeretal. 1994. Metal Removal in Wetland Treatment Systems. In the Proceedings of the
, International Land Reclamation and. Mine Drainage Conference and Third International
I gm« mill ii|iii|i||iii iiiiin i fiXJSfK 8? *k* Abatement of Acidic Drainage, April 24-29.
iiiiiiiiii 11 iiiiiii nil iiiiiiiiiiiii iiiiii i i|iiiii i iiiiiii 11 ' " i i i i i i
Engineering'andMining Journal. 1990 (January). "Technology Turns Southwest Waste mto Ore "
YfiL 1S.1* PP. 41-44. . .
' ' i , i '' ' ' !
Environmental LaW Institute, 1992 (November). State Regulation of Mining Waste: Current State of
«• me Art. • . , ,. :
1 ' .,(?., " i , : ' ,'-!, ' i I ' ' :
fast, John L. 1988 (June). "Carbons-in-Pulp Pioneering at the Carlton Mill." Engineering &
• . • • * . 6
SSSyyi. ^.^ M- Erickson. 1988. Pre-Mine Prediction of Add Mine Drainage. In:
Dredged Material and Mine Tailings. Edited by Dr. Wffiem Salomons and Professor oT
ylnch Forstner. Copyright by Spnnger-Verlag. Berlin, Heidelberg.
Ferguson, K.D., and K., A. Morin. 1991. The Prediction of Add Rock Drainage - Lessons From
^J2*556 & Second International Conference on the Abatement of Acidic Drainage
C*}nferen<* Proceedings, Volumes 1 - 4, September 16, 17, and 18, Montreal, Quebec '
F6it»P- 19?° ...... ^art*>: ............... "*** ..... Sacer ...... Gold
^erstenau»M. C., (editor). 1976. Flotation, Volume 2. New York: Society of Mining Engineers.
- 1992' u^^ Mining: Mechanical Extraction Methods, 'in
2nd Edition (HA. Hanma^ ed.). Society for Mining
SSfEr and Exploration, Inc. Littleton, CO.
............ 1986; ................ ^^ ...... 1±,^±: ....... W:H: .........
.RL^8Q (Pe^mber). "Operating A Commercial-Scale Bioleach Reactor at the Congress
Gold Property.'' Mining Engineering.
. 1983. Determination of Add Generation Rates in
Conference of Water Pollution
7=4 September 1994
i i i ,
i
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EIA Guidelines for Mining . References.
\
Harrelson, C.C., C.L. Rawlins, and J.P. Potyondy. 1994. Stream Channel Reference Sites: An
Illustrated Guide to Field Technique.. U.S. Department of Agriculture, U.S. Forest Service,
Fort Collins, Colorado.
Harty, D.M. and P.M. Terlecky. 1984a (February). "Existing Wastewater Recycle Practices at
Alaskan Placer Gold Mines", Frontier Technical Associates, Memorandum to B.M. Jarrett,
U.S. EPA, Effluent Guidelines Division.
Harty, D.M. and P.M. Terlecky. 1984b (February). "Water Use Rates at Alaskan Placer Gold
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U.S. Environmental Protection Agency. 1988b. Economic Impact Analysis of Final Effluent
,. GitideUnes and Standards for the Gold Placer Mining Industry. Office of Water Regulations
and Standards. Washington, DC. " .
iiiiiiiii
U.S. Environmental ....... Protection ..... Agency. 1989a. Final Report: Copper Dump Leaching and
...... Mcmagement Practices that Minimize the Potential for Environmental Releases. Prepared by ' '
....... ..... ....... - ........ ...... ...... ____-_. ...... _.._. ....... ___ ...... ___, ...... „ ................ _____ [[[
PEI Aijsocliiitesi ....... j
Washington, DC.
^ ...... ____-_. ...... _.._. ....... ___ ...... ___, ...... „
U.S. Environmental Protection Agency. 1989b. Rapid Reassessment Protocols for Use in Streams
ana Rtvers.
PA/440/4-89/001. Washington, DC.
U.S. Environmental Protection Agency. 1989c. Ecological Assessment of Hazardous Waste Sites: A
"'-- ______
:,U.S.j Ejmroi|nen|i| gro|ec||gnaAgency. 1990 (January). Performance of Current Sediment Control
" Construction Sites. Metropolitan Washington Council of Governments.
;= 1990 (AprD)!
=! , = ^ , U.S.
Inventory of Current Practices. Washington, DC.
Ejrvjronmental Protectian Agency, Office oflUseaxch and^Deydppmeit^ 19921'' Draft.
Generation From Non-Coal Mining Waste: Notes of July 1992 Workshop.
for the Environmental Monitoring Systems Laboratory, Las Vegas,'Nevada 89193- '
U.S. Environmental Protection Agency, Office of Research and Development. 1993 .(May 20).
Personal cojnnumication between Ed Heithmar, U.S. EPA Office of Research and Development,
-------
EIA Guidelines for Mining References
U.S. Environmental Protection Agency. 1994. Workshop on the Use ofSulfate Reducing Bacteria.
for Treating Mine Drainage from Metals Mines. Cincinnati, OH, February 23-24, 1994.
U.S. General Accounting Office. 1991(June). Mineral Resources: Increased Attention Being Given to
Cyanide Operations. Report to the Chairman, Subcommittee on Mining and Natural Resources,
Committee on Interior and Insular Affairs, House of Representatives. GAO/RCED-91-145.
U.S. Soil Conservation Service. 1975. Procedure for Computing Sheet and Rill Erosion on Project
Area. Technical Release No. 51.
United States Steel. 1973. The Making, Shaping, and Treating of Steel (H.E. McGannon, editor).
Herbick and Held, Pittsburgh, PA.
University of California at Berkeley. 1988 (July). Mining Waste Study, final Report. Prepared for
the California State Legislature. Berkeley, CA.
University of Nevada - Reno. 1993 (January 13). Personal communication between den Miller and
Joseph Rissing, Science Applications International Corporation. Falls Church, VA.
van Zyl, D J.A., I.P.G. Hutchison, and J.E. Kiel (editors). 1988. Introduction to Evaluation,
Design and Operation of Precious Metal Heap Leaching. Projects. Society for Mining,
* .Metallurgy, and Exploration, Inc. Littleton, CO. .
Want, W.L. 1990. Laws of Wetlands Regulations. Clark Boardman Company, Ltd. New York,
NY. -
Weiss, N.L. (editor). 1985. SME Mineral Processing Handbook, Volume .2. New York: Society
of Mining Engineers. . * . .
White, William W. et al. 1994. Chemical Predicative Modeling of Add Mine Drainage. From Waste
Rock: Model Development and Comparison of Modeled Output to Experimental Data. In the
Proceedings of the International Land Reclamation and Mine Drainage Conference and Third
International Conference on the Abatement of Acidic Drainage, April 24-29.
Whiteway, P. (editor). 1990. "Mining Explained: A Guide To Prospecting and Mining." The
Northern Miner.
The Wildlife Society, 1980. WiIdlife Management Techniques Manual. Fourth Edition: Revised.
Sanford D. Schemnitz (editor). Washington, D.C.
Williams, R. David. 1994. The Bureau of Land Management Add Rock Drainage Policy An
Evolution in Environmental Protection. In the Proceedings of the International Land
Reclamation and Mine Drainage Conference and Third International Conference on the
Abatement of Acidic Drainage, April 24-29.
Wyoming Department of Environmental Quality, Land Quality Division. 1991. In Situ Mining State
Decision Document for Everest Minerals Highland Uranium, WDEQ/LQD Permit No. 603-A2.
7-15 September 1994
-------
I ' I
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-------
SECTION 6
GLOSSARY
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-------
GLOSSARY
-
do not
which, thefcie, an EA • . E °n fc human "vuo.meM and for
ENVIRONMENT IMPACT ASSESSMENT- Environmental impact assessment is
pflL2S*TiatlC' re]foducible' a™1 interdisciplinary consideration of the potential
effects of a proposed action and its reasonable alternatives on the physical, biological
-------
of activities related to projects, plans, programs or policies. Involvement of the public
and interested parties is important to obtaining complete information on impacts and
'ensunng sound results.
Jl ' ' , . ',•','''
EIA has a variety of names in different settings. It may be a formal document or
dispersed in different parts of other documents. In more recent training materials,
, , I , i, ESSJA h,32 SlEPPP6** anv distinction between the term environmental assessment (EA)
and environmental impact assessment (EIA) to simplify discussion. However the
original Sourcebook from which Section 1 is drawn may use US terminology, that is
3EA |J2E |fee, IlIlM assessment of whether a. fujl EM |§ needed, andi EIS for an
environmental impact statement or full EIA document. You may also see the original
use the |erm eQyy-onjnentai assessment (EA) for pie process and
environmental impact assessment (EIA) used to refer to the document.
SK .ASSESSMET ~
TlSfc assessment deals with risks
feat anse in or are transmitted through the airz water_j soil or biological food chains to
man,
and' interested parties.
l,i: ................. II ..... a ................................ ...... „!: ................................. f,
task that depends on the application of human
....... JfeSffiSSSpg ....... the ....... significance -of the potential impacts to the affected
" [[[
— mpartmejital models that estimate fee relative distribution of pollutants
OTmpartments (e.g., air, sol, water, sediment, biota). These
based ....... on ...... the ...... tendency of a chemical to escape from one chemical phase into
gg, NO ;SJG|gFICANT IMfACT (FNSI) — A document briefly presenting fee
; jeasons why a proposed g^gon jfifa not have a significant effect on fee environment and
iB^anEXAwiU ngl ^prepared.
njeda; ..... Xknown as
fiS ..... transfers ....... ochemicals ..... among
exposures from multiple environmental
Most multi-compartment models consist of linked, suigle-medium models,
i piay simulate fee physical and chemical processes feat drive fee transport of
icals across air/water, air/snii anH water/soil mterfaces. The dala.requirements for
understanding of intermedia
sucn models are
processes is still embryonic.
effects are those caused by an action that are later in time or
in distance; but that are still .reasonably foreseeable (e.g., development
iJH^ Illlllll
arenas as a result of road building for logging purposes.
-------
NON-GOVERNMENTAL ORGANIZATION *
U.S. ENVIRONMENTAL ASSESSMENT (EA) - Li the U S
U.S. ENVIRONMENTAL IMPACT STATEMENT fPJ^ T« th- TT c ™ .
-------
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-------
SECTION 7
ENVIRONMENTAL IMPACT ASSESSMENT
RESOURCES ON THE INTERNET AND ON
COMPACT DISC
-------
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-------
7. INTERNET SITES AND INTERACTIVE CD-ROMS FOR REFERENCE
In addition to the written hard copy materials presented within this resource manual and referred to hi
the student texts, reviewers may take advantage of a burdgeoning number of on-line internet services
related to Environmental Impact Assessment and an interactive CD-ROM with both resource materials,
a self-study case study to prepare an environmental impact assessment and also to provide logical and '
ordered prompts in the review or preparation of any future EIA. EPA capacity building materials
are now available off the EPA website at www.epa.gov/oeca/ofa.
7.1 Sample Internet Site References Related to Environmental Impact Assessment
1. AUSTRALIAN EIA NETWORK - ENVIRONMENTAL IMPACT ASSESSMENT"
(EIA) IN AUSTRALIA - COMMONWEALTH
http://www.erin.gov.au/portfolio/epg/eianet/eia/eia_com.html
2. BRITISH COLUMBIA ENVIRONMENTAL ASSESSMENT OFFICE
http://www.eao.gov.bc.ca/
3. CANADIAN ENVIRONMENTAL ASSESSMENT AGENCY
http://www.ceaa.gc.ca:80/agency/agency_e.htm
4. CffiSIN HOME PAGE
http://www.ciesin.org/
5. DEPARTMENT OF ENERGY ENVIRONMENTAL POLICY AND GUIDANCE -
RISK ASSESSMENT (US)
http://tis-nt.eh.doe.gov/oepa/guidance/risk.htm
6. DEPARTMENT OF ENVIRONMENT - ENVIRONMENTAL GUIDELINES
(MALAYSIA)
http://www.jas.sains.my/doe/r_guide.html
7. DIRECTORY OF ENVIRONMENTAL RESOURCES ON THE INTERNET
http://www.envirosw.com/
8. ECOLOGICAL MONITORING AND ASSESSMENT NETWORK (ENVIRONMENT
CANADA)
http://www.cciw.ca/eman-temp/intro.html
9. EIA (ENVIRONMENTAL IMPACT ASSESSMENT) CENTRE, UNIVERSITY OF
MANCHESTER
http://www.ids.ac.uk/eldis/data/d021/e02168.html
10. EIA: ENVIRONMENTAL IMPACT ASSESSMENT IN A TRANSBOUNDARY
CONTEXT - PRINCIPLES AND CHALLENGES FOR A COORDINATED NORDIC
APPLICATION OF THE ESPOO CONVENTION, BY STIG ROAR HUSBY
http://odin.dep.no/eia/paper/srh980516.html
11. EIS (ENVIRONMENTAL IMPACT STATEMENT) DATABASE
http://envirosense.com/ofaview/one_search.html
12. ENVIRONMENTAL IMPACT ANALYSIS DATA LINKS
http://h2o.usgs.gov/public/eap/env_data.html
13. EUROPEAN ENVIRONMENT AGENCY
http://www.eea.dk/default.htm
14. GEO-1,THE COMPLETE REPORT: TABLE OF CONTENTS - LIST OF FIGURES
- LIST OF TABLES
http://www.grida.no/prog/gIobal/geol/ch/toc.htmMgs
15. GEO INFO SYSTEMS RESOURCE PAGE
7-1
-------
f
I http://www.geoinfosysteins.com/resource.htm
16. ffiEE-SSrr (ELECTRICAL AND ELECTRONIC ENGINEERS - SOCIETY ON
•111 iiiii ••iiiiiii ill ill
17.
FOR IMPACT ASSESSMENT
//ndsuext.nodak.edu/iaia/
FOR THE SYSTEMS SCIENCES HOMEPAGE
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19.
ISEM (INTERNATIONAL SOCIETY FOR ECOLOGICAL MODELING)
http://ecomod.tamu.edu/%7Eecomod7isem.html
20. THE PERRY-CASTANEDA LIBRARY MAP COLLECTION
, i i http://wwvv.lib.utexas.edu/Libs/PCL/Map_collection/map_sites/map_sites.ht
|™^ ACT (TJSA) ; \ \
: ; http://ceq.eh.doe.gov/nepa/nepanet.htm
S5S2& ASOCIAL AND ENVIRONMENTAL ASSESSMENT BULLETIN
http://home.echo-on.net/~lisa/bulletin.html
==33. THEWATERSHED MANAGEMENT COUNCIL
http://glinda.cnrs.humboldt.edu/wmc
1^4. \ US EPA, OFFICE OF FEDERAL ACTIVITIES
=-:=littp://es.epa.gov/oeca/of
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Eteractive CD-Rom: References:
USEPA has produced two compact discs that are either available separately or combined into a
single CD in version 4 issued in 1998. The two component programs are:
= liYgonmental Impact Assessment Resource Guide (EARG): The EARG is an interactive
allows participants to walk through information on the EIA process from project
'Initiation to post-decision analysis. The outline of its contents follows in this section.
iiiii aiiiiiiH^^^^ J
- Environmental Impact Assessment Interactive Case Study: Chuitna, Alaska: This interactive
CD-ROM enables the user to wajk through the complete EIA process for a proposed project in
Chuitna, Alaska and develop their own EIA. The CD-ROM covers the project's initiation,
Sping, generation and analysis of alternatives, decision-making, and post-decision analysis.
ebook feature of the program Is geared toward both si^tudy is well as anprbyidhig
;tooll As an ongoing ...... tool] ....... the" ..... noteBook' ..... leature ..... of ""the ..... programenables ....... SieuseTto ...................
as a, prompt to assist in fine development or review or any EIA shice thejr can
be cleared and saved under different file names. An outline of the program's contents follows
in this section..
—;. Copies" can be obtained from:
of Federal Activities
U.S. Environmental Protection Agency
MC 2251-A
^^ llflil llllll
I
1200 Pennsylvania Avenue NW
Washington D.C. 20460
-------
ENVIRONMENTAL .ASSESSMENT RESOURCE GUIDE (EARG)
The focus of the EARG software is generally an Environmental Assessment (EA) process
for project level decisions.
There are six steps in the HA process: 1) Initiation, 2) Scoping, 3) Generation of
Alternatives, 4) Assessment, 5) Decision-Making and 6) Post Decision Analysis (Follow up
project monitoring).
INITIATION involves the review of the environmental information packet provided by
those proposing the project, determination of the extensiveness of the project, assembly of an
interdisciplinary team, and development of a public involvement strategy.
• SCOPING involves the identification of reasonable issues and concerns, consultation
within and among governmental departments, and scoping meetings that involve the public.
GENERATION OF ALTERNATIVES involves the identification of alternative ways to
meet the basic purpose of and need for the project.
ASSESSMENT involves an inventory of existing environmental conditions, assessment of
the potential environmental impact of the project, and determination of the steps required to
minimize the environmental damage.
DECISION-MAKING involves making the decision based on the Final EA documentation
and formally documenting the decision publicly.
POST- DECISION ANALYSIS involves the evaluation of scientific, technical,
procedural, and administrative issues during and after implementation of the proposed'action and
performance of base-line compliance, environmental effects, and mitigation monitoring.
(For ease in navigating on the computer through EARG use the structural outline that follows the
Chuitna case study description).
CHUITNA CASE STUDY
The Diamond Chuitna Coal Case Study is based on an actual Environmental Impact
Statement (EIS) conducted by Region 10, USEPA in the late 1980's and is designed to provide a
computer tutorial experience in simulating the development of a complex project proposal that
required the preparation of an EIS.
The proposed project involves the development of a coal mine in Beluga Region of
Alaska, USA. Throughout the software program, the user plays the role of the Project Manager
and is responsible for making plans and decisions. The program will be most meaningful if the
user has already worked through EARG.
7-3
-------
! " ' I '' !
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CD-ROM: ENVIRONMENTAL
ASSESSMENT RESOURCE GUIDE (EARG)
=;i::z ::"': ..... :::,,,; ....... :::;::: ...... ™," ...... :::::::;: OUTLINE OF CONTENTS
r.:« ....... , ........... l INTRODUCTION
:•-- • - i & ASffiffiEs
ft'pnmD, Glossary
igs PIans]& Programs
. References
lilllii' Ill IHB^^^^^^^^^^^^^^
"onrnentalnformatinPacket
f^^^J^pject Responsibilities
jlic Involvement Strategies
° ' M,
>, FJanning Records
B. Tools
ii'li.l'Tli'illLJllllllllllillillli'i'li'iBii l":lli "IIHillilWihJII
i=^^^ Issues
1. EA and Project Planning
., , ; ,., ;,;,,,,,! , .; , y ,; 2. Goordjriatioji.witli Other, Laws
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........ lillM^ ..... Ill ..... 11!
1. Needs
, .,2r:Tools
^ r^ri'lr:;!^'!. Issues
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• Project Information
Early Planning
7-4
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3. Public Involvement
B. Tools (Scoping meeting)
C.Issues
D. Linkages
E. References
V. GENERATION OF ALTERNATIVES
A. Needs
B. Tools
C. Issues
D. Linkages
E. References
F. Describing the Environmental Setting
Geology, Topography, Soils, Groundwater Resources, Surface Water Resources,
Terrestrial Communities, Aquatic Communities, Sensitive Areas, Air Quality, Land
Use, Demography, Sound Levels, Infrastructure Services, Transportation, Cultural
Resources, Project Economics.
VI. ASSESSMENT
A. Affected Environment
1. Needs
2. Tools
3. Issues
4. Linkages
5. References
6. General Site Information (12 items, most illustrated)
B. Impact Identification
1. Needs (17 illustrated items)
2. Tools
a. Site Visits
b. Use of Checklists
c. Checklist Example
d. Matrix
e. Networks
f. Other Tools (GIS)
3.Issues
a. Boundaries
b. Predicting Impacts
c. Assessing Cumulative Impacts
d. Defined Endpoints
4. Linkages
5. References
C. Impact Analysis and Prediction
1. Needs
2. Tools
- - 7-5
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II I III II
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3,Issues
4, Linkages
5. References
D. Determination of Significance
!'""! Seeds
2. Tools
3: Issues
4: Linkages
5, References
6. Categories of Mitigation
a. Avoidance
b. Minimization
c. Rectification
d. Reduction
e. Compensation
'F. Documentation
LNe^ds
2. Tools ™"™'"
3. Issues
4. Linkages
5. References
6. EIA, Elements
G. Small Projects
1, Small Project EIAs
2. Environmental Audits
H. World Bank Mitigation Tables
Ch. 8: Agricultural and Rural Development, Rural Development, Agroindustry,
Dams and Reservoirs, Fisheries, Floo3 Protection, N*atural Forest Management,
i •"''i™, j'i'ij' 's> i! I] • jr.™•IfflffiSSi?i?v^0^mei^^nf *^ore^a^°.?',fr^s^0™an<^.•P1-3^^,6,1? Hy,^?9^.^^
™ 'l'"1""1' '""' ^^'^"'"'.Jii^eland Management Rural roact'sT'
Cff. 9: Population, Health, Transport, Development, Water and Sewer, Roads and
Highways, Inland Navigation, Ports and Harbors, Housing Projects, Solid Waste,
Tourism, Wastewater.
QL !i!:"/~O
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D. Linkages
E. References
F. Alternatives (Matrix)
VIII. POST-DECISION ANALYSIS
A. Needs
B. Tools
C. Issues
D. Linkages
7-7
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riii""!1:
I
CD-ROM: EIA CASE STUDY: CHUITNA, ALASKA
d , ,;
:: : ::= ! OUTLINE OF CONTENTS
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5. Determination of Significance
a. Introduction
b. Criteria for Significance
c. Magnitude/Likelihood
d. Confidence in Prediction Values
e. Assumptions/Limitations
6. Mitigation
a. Introduction
b. Reclamation Plan
c. Categories of Mitigation
d. Terrestrial Habitat
e. Test Your Knowledge
7. Documentation
E. DECISION-MAKING
1. Introduction
2. Review Proposed Tradeoffs
3. Identify Preferred Alternative
4. Comparing Housing/Airstrip Options
5. Record of Decision
6. Status of Report
F. POST-DECISION ANALYSIS
1. Introduction
2. Important Impacts
3. Categories of Mitigation
4. Monitoring Requirements
7-9
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Example Internet Site References Related
to
Environemental Impact Assessment
SOCIAL ANDENVIRONMENTAL ASSESSMENT BULLETIN
http://home.echo-on.net/~hsa/bulletin.html
ENVIRONMENTAL IMPACT ANALYSIS DATA LINKS
http://h2o.usgs.gov/public/eap/envjiata.ntml
ISEM (INTERNATIONAL SOCIETY FOR ECOLOGICAL MODELING)
http://ecomod.tamu.edu/%7Eecomod/isem.html
INTERNATIONAL SOCIETY FOR THE SYSTEMS SCIENCES HOMEPAGE
http ://www. sysval. org/isss/
INTERNATIONAL ASSOCIATION FOR IMPACT ASSESSMENT
http://ndsuext.nodak.edu/iaia/
IEEE SSIT HOME PAGE
http://wvm4.ncsu.edu/unity/users/5y5herkert/index.html
DOE ENVIRONMENTAL POLICY AND GUIDANCE - RISK ASSESSMENT (US)
http://tis-nt.eh.doe.gov/oepa/guidance/risk.htm
CANADIAN ENVIRONMENTAL ASSESSMENT AGENCY)
http://www.ceaa.gc.ca:80/agency/agency_e.htm
BRITISH COLUMBIA ENVIRONMENTAL ASSESSMENT OFFICE (EAO)
http://www.eao.gov.bc.ca/
ECOLOGICAL MONITORING AND ASSESSMENT NETWORK (ENVIRONMENT
CANADA)
http://www.cciw.ca/eman-temp/intro.html
THE WATERSHED MANAGEMENT COUNCIL
http ://glinda. cnrs.humboldt. edu/wmc
DIRECTORY OF ENVIRONMENTAL RESOURCES ON THE INTERNET
http://www.envirosw.com/
CIESIN HOME PAGE (Not able to be contacted during test run)
http://www.ciesin.org/
7-11
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" I
EUROPEAN ENVIRONMENT AGENCY
IIIIIIVB http://www.eea.dk/default.htm
ii in iii innn Hi iiiiiiiivi ifn'my
I
EIA:ENVIRO3S!MENTAL IMPACT ASSESSMENT IN A TRANSBOUNDARY CONTEXT -
; ; PRINCIPLES AND CHALLENGES FOR A CQOJ^MATED NORDIC APPLICATION OF
THEESPpO CONyENTION, BY STIGROARHUSBY
htto:7/odin.dep.no/eia/paper/srh980516.html
•MlANCHESJgk [
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ApSTRALIANEIANETWOEK - ENVIRONMENTAL IMPACT ASSESSMENT (EIA) IN
AUSTRALIA - COMMONWEALTH
=—^
nttp://www.jas.sains.my/doe/r_guide.ntml -
AP-RELATED
S THE PEj^Y-CMTAlfeDALrBRAJlYMAP COLLECTION,
^ ' ^ ^ ' ^ ^ .
.edi^
INFO SYSTEMS RESOURCE PAGE
--
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