United States Environmental
Protection Agency
Office of Land and
Emergency Management
Directive Mo. 9285.2-14
October 2020
Superfund
Best Practices to Prevent
Releases from
Impoundments at
Abandoned Mine Sites whiEle
Conducting CERCLA
Response Actions
www.epa.gov/aboutepa/about-office-land-and-emergency-management
www.epa.gov/superfund/abandoned-mine-lands
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NOTICE AND DISCLAIMER
This document presents best practices and approaches to reduce the threat of, or prevent, a proposed
Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) activity from
causing a breach or failure of impoundments at abandoned mine sites. These best practices are based
predominantly on current U.S. federal and state practices and standards for management of operating
impoundments but have been adapted to the conditions found at abandoned mine impoundments.
This document is not intended to provide approaches on how to remediate and close abandoned mine
impoundments nor does it provide information on the design, construction, and inspection of active
impoundments. This document does not address how to respond to natural events that could cause
abandoned mine impoundment failure; it only addresses field activities associated with U.S.
Environmental Protection Agency (EPA) CERCLA response actions.
This document provides considerations and recommendations and does not impose legally binding
requirements, nor does it confer legal rights, impose legal obligations, implement any statutory or
regulatory provisions, or change or substitute for any statutory or regulatory provisions. It is important
that users of this document also refer to applicable regulations, policies, and guidance documents.
The best practices presented in this document and in other documents referenced are intended to serve as
technical resources for EPA working on CERCLA sites with abandoned mine impoundments. Mention of
specific products does not constitute endorsement or promotion of those products.
This document was prepared by Tetra Tech, Inc. (Tetra Tech) for EPA under Superfund Technical
Assessment and Response Team (START) contract EP-S5-13-01.
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ACKNOWLEDGEMENTS
EPA would like to acknowledge and thank the following individuals and organizations who contributed
to the development and review of this document:
U.S. Environmental Protection Agency
Shahid Mahmud, National Mining Team Leader
Kirby Biggs, National Optimization Coordinator
Patrick Kelly, Office of Resource Conservation and Recovery
Jim Bove, Office of General Counsel
Elizabeth Berg, Office of General Counsel
Ed Hathaway, Remedial Project Manager, Region 1
Bonnie Gross, Associate Director, Region 3 (retired)
Gary Baumgarten, Remedial Project Manager, Region 6
Joy Jenkins, Remedial Project Manager, Region 8
James Hanley, Remedial Project Manager, Region 8
John Hillenbrand, Regional Mining Coordinator, Region 9
Dan Shane, On-Scene Coordinator, Region 9 (retired)
Ken Marcy, Site Assessment Manager, Region 10
Ed Moreen, Remedial Project Manager, Region 10
Beth Sheldrake, Emergency Management Branch Chief, Region 10
Patty McGrath, Mining Advisor, EPA Region 10
Tim Grier, EPA Office of Emergency Management (retired)
Technical Reviewers
Jay Hawkins, Office of Surface Mining Reclamation and Enforcement
John Craynon, National Academy of Sciences, Virginia Tech
Anne Marie Palmieri, Alaska Department of Environmental Conservation
Paul Krabacher, U.S. Department of the Interior, Bureau of Land Management
Scott Ludwig, U.S. Department of Agriculture, U.S. Forest Service
John Stanton, U.S. Army Corps of Engineers
John Hartley, U.S. Army Corps of Engineers
Cory Kroger, U.S. Army Corps of Engineers
Steve Butler, U.S. Army Corps of Engineers
Marilyn Long, Texas Commission on Environmental Quality
Bob Seal, U.S. Geological Survey
Houston Kempton, Earthworks
Montana Department of Environmental Quality
National Mining Association
Association of State Dam Safety Officials
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TABLE OF CONTENTS
NOTICE AND DISCLAIMER i
ACKNOWLEDGEMENTS ii
TABLE OF CONTENTS iii
ACRONYMS AND ABBREVIATIONS v
1.0 INTRODUCTION 1
1.1 Background 3
1.2 Primary Resources 4
1.3 Document Organization 5
2.0 CONDUCT INITIAL IMPOUNDMENT CONDITION ASSESSMENT 6
2.1 Develop an Impoundment Conceptual Site Model 6
2.1.1 Review Available Documents and Data 7
2.1.2 Conduct a Site Visit and Visual Assessment 9
2.1.3 Make an Imminent Risk Determination and Decide if a Geotechnical Analysis
Is Needed 11
3.0 PERFORM STRUCTURAL STABILITY AND SAFETY ANALYSIS 13
3.1 Assemble a Qualified Investigation Team 13
3.2 Plan and Conduct an Impoundment Geotechnical Investigation 14
3.2.1 Conduct a Data Gap Analysis and Additional Site Visits 14
3.2.2 Develop a Geotechnical Investigation Plan 15
3.2.3 Analyze the Risks of the Proposed Geotechnical Investigations 20
3.2.4 Develop a Contingency, Notification, and Emergency Action Plan for the Proposed
Intrusive Geotechnical Activity 23
3.2.5 Analyze the Geotechnical Data 26
3.3 Determine the Hazard Potential Classification 27
3.4 Evaluate the Hydraulic and Hydrologic Capacity 28
3.5 Estimate the Factors of Safety 28
3.5.1 Determine Slope Stability 29
3.5.2 Determine the Factors of Safety 29
3.6 Assign a Condition Rating 30
3.7 Develop an Impoundment Structural Stability and Safety Report 31
4.0 MITIGATION MEASURES TAKEN PRIOR TO PROCEEDING WITH THE PROPOSED
ACTIVITY 33
5.0 BIBLIOGRAPHY 35
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EXHIBITS
Exhibit 1. Condition Assessment Decision Logic 7
Exhibit 2. Drone Use in Initial Impoundment Condition Assessments 9
Exhibit 3. Information Sources for Performing Impoundment Inspections 15
Exhibit 4. Resources for Impoundment Drilling 19
Exhibit 5. Federal Energy Regulatory Commission Drilling Program Plan Required Content 19
Exhibit 6. Examples of Drilling-Related Potential Failure Modes 21
Exhibit 7. Example FMEA Risk Categorization Matrix 22
Exhibit 8. Common Field and Laboratory Soil Test Methods 26
APPENDICES
APPENDIX A. BEST PRACTICES SITE VISIT CHECKLISTS A-l
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ACRONYMS AND ABBREVIATIONS
§ Section
AML
Abandoned mine land
ASDSO
Association of State Dam Safety Officials
ASTM
American Society for Testing and Materials
BOR
Bureau of Reclamation
CERCLA
Comprehensive Environmental Response, Compensation, and Liability Act
CFR
Code of Federal Regulations
CNEAP
Contingency, notification, and emergency action plan
CPT
Cone penetrometer testing
CSM
Conceptual site model
DHS
U.S. Department of Homeland Security
DPT
Direct push technology
EC
Engineering control
EPA
U.S. Environmental Protection Agency
EPRP
Emergency preparedness and response plan
ETA
Event tree analysis
FEMA
Federal Emergency Management Agency
FERC
Federal Energy Regulatory Commission
FHWA
Federal Highways Administration
FMEA
Failure modes and effects analysis
FOS
Factors of safety
GBC
Government of British Columbia
GPR
Ground penetrating radar
H&H
Hydraulic and hydrologic
HSA
Hollow stem auger
ICMM
International Council on Mining and Metals
IDF
Inflow design flood
InSAR
Interferometric synthetic-aperture radar
LEA
Limit equilibrium analysis
LIDAR
Light detection and ranging
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ACRONYMS AND ABBREVIATIONS (CONTINUED)
MAC Mining Association of Canada
MCE Maximum credible earthquake
MDE Maximum design earthquake
MSHA Mine Safety and Health Administration
NCP National Contingency Plan
NID National Inventory of Dams
NOAA National Oceanic and Atmospheric Administration
OSC On-Scene Coordinator
OSMRE Office of Surface Mining, Reclamation, and Enforcement
PE Professional Engineer
PFM Potential failure mode
PG Professional Geologist
PGA Peak ground acceleration
PH Professional Hydrologist
PMF Probable maximum flood
QA/QC Quality assurance/quality control
RPM Remedial project manager
SEE Safety evaluation earthquake
SPT Standard penetration test
START Superfund Technical Assessment and Response Team
Tetra Tech Tetra Tech, Inc.
TSF Tailings storage facility
UNEP United Nations Environment Programme
UNESCO United Nations Educational, Scientific and Cultural Organization
USACE U.S. Army Corps of Engineers
USFS U.S. Forest Service
USGS U.S. Geological Survey
USSD U.S. Society on Dams
WISE World Information Service on Energy
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1.0 INTRODUCTION
Under the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA), the
U.S. Environmental Protection Agency (EPA) performs a range of activities at abandoned mine
land (AML) sites. CERCLA authorities may be used to respond to releases or threatened releases of
hazardous substances, as well as pollutants or contaminants, into the environment, "which may present an
imminent and substantial danger to the public health or welfare" (40 Code of Federal Regulations [CFR]
Section [§] 300.130). The National Oil and Hazardous Substances Pollution Contingency Plan, more
commonly called the National Contingency Plan (NCP), is EPA's blueprint for carrying out CERCLA
response actions. The adoption of any of the best practices noted in this document cannot be inconsistent
with the NCP. While this best practices document was prepared for use by EPA, federal land management
agencies such as the U.S. Department of the Interior and the U.S. Forest Service, also have authority to
implement CERCLA actions on federal lands. EPA regions and their site support partners and contractors
should follow the best practices laid out in this document when carrying out CERCLA removal, remedial,
and site investigation activities at Superfund sites with abandoned mine impoundments.
This best practices document presents approaches to prevent a failure1 at abandoned2 mine
impoundments3 that result in a sudden release of fluid and liquefiable mine waste4 from a proposed
CERCLA activity. The application of these best practices depends on site-specific conditions that, in
limited cases, may warrant the use of alternative technologies and approaches to those described in this
document. The key activities for assessing and mitigating the potential impacts of such releases from a
proposed CERCLA action at an abandoned mine impoundment include:
Conducting an initial impoundment condition assessment, including development of a conceptual
site model (CSM), of whether the proposed CERCLA action has the potential to cause a failure or
breach at an abandoned mine impoundment;
Determining the need to collect additional geotechnical data;
Developing a drilling and excavation plan;
Performing a failure modes and effects analysis (FMEA) of the proposed invasive activity;
Developing or revising contingency, notification, and emergency action plans (CNEAP);
1 "Failure" as used in this document refers to situations where impoundments or impoundment structures fail, releasing contained
waste. Failure modes include overtopping, slope instability, earthquakes, seepage, structural inadequacies (such as pipe leaks or
collapses), and foundation conditions.
2 "Abandoned" as used in this document refers to situations where impoundments are no longer actively managed, maintained, or
regulated as waste management units. In some cases, abandoned mine impoundments may be located on property with owners,
operators, or claimants.
3 'Impoundment" as used in this document refers collectively to the whole impoundment structure, including any impounded
waste and associated impoundment structures, such as dams, berms, liners, and spillways. Impoundments in this document are
limited to abandoned above-ground tailings, storm water, and process water impoundments at former mine sites.
4 "Fluid and liquefiable mine waste" as used in this document includes impounded water, impounded process waste and waters,
process solutions, high moisture content tailings, and other mine wastes disposed of in an abandoned impoundment. It should be
noted that there may be varying degrees of saturation of wastes within an abandoned impoundment.
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Collecting data by minimally invasive and invasive (drilling and pit excavation) methods5;
Determining impoundment hazard potential, factors of safety (FOS) and condition ratings; and
Mitigating identified impoundment failure risks that do not meet FOS prior to conducting a
proposed activity.
Use of the approaches described in this document may not be necessary if an abandoned mine
impoundment no longer holds liquids or saturated wastes and poses no known risk of failure based on
existing records, site evaluations, and monitoring data. However, investigating and remediating wastes
present within such abandoned mine impoundments may be appropriate under existing CERCLA
authorities since wastes may remain in a saturated state even after an impoundment has been breached or
dewatered and can suddenly flow downgradient under hydraulic or seismic conditions.
Abandoned mine impoundments are typically constructed of concrete, tailings, or other earthen material,
such as rock, waste rock or unconsolidated overburden. The fine grain size of mill tailings compared to
the coarse, heterogeneous grain size of waste rock means that tailings impoundments may tend to be
saturated and anoxic whereas waste rock piles tend to be unsaturated and oxic. Abandoned tailings
impoundments themselves may have been used to dispose of other materials in addition to tailings, such
as waste rock, processing and water treatment sludge, process waste waters and sewage treatment wastes.
This document does not address the prevention of breaches or failures at abandoned man-made
infrastructure that store fluids below ground. This document also does not address the potential for failure
of concrete tailings impoundments and dams. Concrete tailings impoundments and dams are rare and
should be evaluated for potential failure on a case-by-case basis, referring to appropriate concrete dam
structural stability evaluation guidelines (USACE 1995, 2005, 2007; BOR and USACE 2015; and
FERC 2016b).
This document does not provide best practices for conducting abandoned mine impoundment remediation
activities. Such actions are highly diverse and site-specific, and they are addressed through existing EPA,
state, and other agency guidance. Remediation activities require detailed planning and execution, the best
practices for which are beyond the scope and intent of this document.
When investigating and mitigating the threat of sudden releases at abandoned mine impoundments with
complex structural, geotechnical, and geochemical issues, some degree of uncertainty will remain.
Application of the best practices described in this document will reduce both risk and uncertainty but will
never eliminate them.
The bibliography at the end of this best practices document (Section 5.0) includes documents cited in the
text and relevant to abandoned mine impoundment failure prevention. General information about wastes
found at abandoned mines can be found in EPA's Abandoned Mine Site Characterization and Cleanup
Handbook (EPA 2000).
5 "Minimally invasive methods" refers to work that does not disturb the impoundment or that minimally disturbs the
impoundment, such as measuring or sampling using existing wells, boreholes, or other safely accessible surface openings, and
water elevation measuring and sampling. "Invasive methods" refers to work that disturbs the impoundment or its structures, such
as drilling, using heavy equipment, excavating, blasting, grading, and dewatering.
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1.1 Background
Mining produces waste rock, ore and protore containing the valued commodity or commodities.
Overburden and waste rock (rock that contains lower levels of mineralization) are removed during mining
to gain access to the ore. Mine tailings are the waste materials that remain after processing the ore to
remove the valuable metals, minerals, or other material. Water and chemicals are generally added during
ore processing, which results in tailings that are in a slurry form. The physical and chemical attributes of
the tailings are directly dependent on the mineralogical composition of the ore, the process of size
reduction and extraction and to what extent the tailings have been dewatered. Impoundments and tailings
storage facilities (TSF) were historically constructed by using natural basins and by building dams of
tailings, waste rock or other earthen materials behind which tailings slurries were impounded
(Richmond 1991; Taggart 1944).
When mining operations ceased, impoundments holding tailings or other mining wastes were often not
adequately closed or maintained and no longer inspected. Even after operations cease, these abandoned
mine impoundments commonly continue to capture and retain precipitation and runoff. As a result,
abandoned mine impoundments and associated dams may be in a deteriorated condition and have
decreased structural integrity, compromising their ability to impound wastes safely. In addition,
abandoned mine impoundments and associated dams may not have been designed, constructed, and
operated to meet modern engineering design and construction standards.
There is limited information about impoundment failures at abandoned mines. However, the Lava Cap
Mine Superfund site dam failure in 1996 is one illustrative example of the effects of such a possible
failure (EPA 2008). Downstream impacts from breached or failed impoundments at operating mines can
also provide insight into the types of environmental, infrastructure, and human health risks should
abandoned mine impoundments be breached or fail. Notable tailings dam failures at operating mines
occurred at the Corrego do Feijao iron ore mine near Brumadinho, Minas Gerais, Brazil in 2019; the
Cieneguita Mine in Chihuahua, Mexico, in 2018; the Hpakant Mine in Myanmar and Germano Mine in
Minas Gerais, Brazil, in 2015; the Mount Polley Mine in British Columbia, Canada, and Buenavista del
Cobre Mine in Cananea, Sonora, Mexico, in 2014; and the Church Rock uranium mill tailings pond
failure near Gallup, New Mexico, in 1979. Additional notable impoundment failures are listed in the U.S.
Department of Interior, Bureau of Reclamation's (BOR) Reclamation Consequence Estimating
Methodology: Dam Failure and Flood Event Case History Compilation (BOR 2015a) and on the World
Information Service on Energy (WISE) Uranium Project website.6
Reviews of past tailings impoundment failures have identified numerous causes of failure, the majority
of which can be attributed to a few common factors for which data exist. The United Nations
Environment Programme (UNEP) reported that of over 200 tailings dam failures between 1915 and 2015,
the most commonly known and documented failure modes were overtopping, slope instability,
earthquakes, seepage, structural inadequacies, and foundation conditions (UNEP 2017). Often, the
underlying cause was a failure to construct or operate to the design intent. The associated deficiencies can
remain long into the post-operation period. Following the Mount Polley Mine impoundment failure in
2014 in British Columbia, Canada, the Mining Association of Canada (MAC) prepared updated guidance
documents on the design, operation, and maintenance of tailings impoundments and evaluated the causes
of failure of such impoundments. These documents provide excellent information on how tailings
0 http://www.wise-uraiiium.org/mdaf.html
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impoundments are designed, constructed, and maintained and include sound technical background useful
for evaluating risks at abandoned mine impoundments (see MAC 2017).
Both federal and state guidance and regulations exist for evaluating the structural integrity of operating
earthen and rock dams and their impoundments. These guides and regulations contain well established
engineering methods to assess the stability of these units. These regulations and guidance materials are,
for the most part, intended for the inspection and evaluation of operating dams, but may also be used for
the inspection and evaluation of impoundments at reclaimed, closed, or abandoned mines. The regulatory
status of an impoundment at an abandoned mine is important and should be verified with the appropriate
state or federal agency. In addition, relevant engineering design information or inspection reports for
older dams and impoundments provide useful information for engineering stability evaluations. In cases
where little or no data about the foundation and design of an impoundment and dam are available,
significant time has passed since existing data were collected, or site conditions have changed since initial
data were collected, it may be necessary to perform geotechnical investigations to collect data that support
updated risk and stability assessments of the facilities.
This document compiles the technical resources and approaches that are the best practices for conducting
stability and safety evaluations of abandoned mine impoundments and their associated dams. These best
practices should be used to evaluate whether an abandoned mine impoundment has sufficient structural
integrity to withstand invasive CERCLA activities without causing a sudden, uncontrolled release.
1.2 Primary Resources
This best practices document includes information drawn from published standards of practice and
guidelines for stability assessments and hazard potential evaluations of operating impoundments. While
the conditions at abandoned mine impoundments may differ from operating impoundments, the best
practices for assessing their safety, stability, and hazards are similar.
Published sources and experts were consulted to compile the best approaches in this document, including
(1) national and international technical resources and publications; (2) lessons learned from tailings dam
failures; and (3) technical contributions from expert professionals with relevant dam safety experience.
Individual experts from the following entities were consulted during the development of this report:
U.S. Army Corp of Engineers (USACE)
U.S. Department of the Interior:
o Office of Surface Mining, Reclamation, and Enforcement (OSMRE)
o U.S. Geological Survey (USGS)
o Bureau of Reclamation (BOR)
U.S. Environmental Protection Agency (EPA)
U.S. Department of Labor, Mine Safety and Health Administration (MSHA)
Federal Energy Regulatory Commission (FERC)
U.S. Department of Homeland Security, Federal Emergency Management Agency (FEMA).
U.S. Department of Agriculture, U.S. Forest Service (USFS)
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Association of State Dam Safety Officials (ASDSO)
Mining Association of Canada (MAC)
International Commission on Large Dams
1.3 Document Organization
This document is organized into five sections and an appendix.
Section 1.0 introduces the document and provides an overview of the best practices and
approaches presented in this document.
Section 2.0 describes the elements of conducting an initial impoundment condition assessment.
Section 3.0 describes the process for performing or overseeing an impoundment structural
stability analysis and preparing a structural stability and safety report.
Section 4.0 discusses interim mitigation actions, such as dewatering the impoundment, prior to
conducting CERCLA activities.
Section 5.0 provides a bibliography with references for material used in the development of this
document, as well as additional resources. Where available, website addresses are provided for
additional informative materials.
Appendix A provides checklists for the best practices described in this document and for
conducting impoundment safety assessments.
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2.0 CONDUCT INITIAL IMPOUNDMENT CONDITION ASSESSMENT
When EPA proposes a CERCLA activity that has the potential to adversely affect impoundment stability,
an initial impoundment condition assessment is performed to identify if the abandoned mine
impoundment shows signs of imminent failure. There are a range of CERCLA activities that have the
potential to adversely affect abandoned mine impoundments. Such activities include well installation,
removal of wastes at or adjacent to an impoundment, placement of heavy construction equipment near or
on an impoundment, heavy trucks causing vibrations, and reclamation or closure of adjacent waste units.
The initial assessment is not a formal structural stability determination; rather, it is used to determine if
further studies are necessary. The initial assessment is not necessary if it is known that fluids or
liquefiable wastes are not currently impounded.
The initial impoundment condition assessment begins with creating a CSM of the impoundment to
understand the characteristics of the dam and impounded materials by (1) reviewing available documents
and data; (2) conducting a site visit to gather data to update the CSM; and (3) making an initial imminent
or unacceptable failure risk determination and deciding if further invasive geotechnical analyses should
be conducted.
2.1 Develop an Impoundment Conceptual Site Model
Creating or updating an abandoned mine impoundment CSM with data and information specific to the
impoundment will better integrate and improve the evaluation of impoundment information, as well as
identify key data gaps, to assess impoundment conditions and resolve uncertainties regarding the potential
for impoundment failure. It is important that the abandoned mine impoundment CSM includes
(1) information on the physical structure of the impoundment; (2) the physical properties of wastes or
other impounded materials; and (3) the regional and local geology, seismicity, meteorology, and
hydrology. Use of graphical CSM depictions (for example, cross-sections of the dam and impoundment
structures and three-dimensional visualizations) is considered a best practice for understanding and
communicating information related to impoundment physical structures, drainage features, surface areas,
cross-sectional areas, and the condition of related features. The impoundment CSM is distinct for mining
site features, but it can also be informed and supplemented by the environmentally focused site CSM
prepared for CERCLA site cleanup efforts.
The CSM integrates information on dam and impoundment structure and waste characteristics with
geotechnical, hydrogeologic, hydrologic, hydraulic, seismic, and geochemical data to assess the potential
risk of a sudden, uncontrolled impoundment failure as a result of proposed CERCLA activities. Given the
specialized focus on the geotechnical, hydrogeologic, hydrologic, hydraulic, seismic, and geochemical
conditions, the impoundment condition assessment is not intended to equate with any traditional site
assessment, remedial investigation, or other characterization stage in the CERCLA site cleanup process.
The problem statement developed as the basis for creating the impoundment CSM is:
What is the stability condition of the impoundment and dam and what are its potential failure modes?
Data gaps identified during the evaluation of the impoundment CSM are used to focus data/information
collection, which leads to a greater understanding of structural stability and helps facilitate site
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decision-making. A decision logic is useful in helping to prioritize data collection for the CSM. Exhibit 1
represents a decision logic for determining whether there is an imminent risk of failure and whether it is
necessary to conduct an impoundment structural stability and safety analysis.
The following subsections present key elements of an abandoned mine impoundment condition
assessment that are conducted to develop a comprehensive impoundment CSM, thereby reducing
uncertainties in determining whether an imminent or unacceptable risk of failure exists.
2.1.1 Review Available Documents and Data
In some design cases, abandoned mine
impoundment monitoring and prior structural
integrity investigations may have been
performed. A comprehensive review of
existing impoundment structure-related
documents should be conducted to confirm
the physical status of the impoundment of
concern. In particular, review of state agency
documents, which may include assessments
of the structural condition of the
impoundment or rating of its condition,
would be highly beneficial to development of
the impoundment CSM.
At this stage of the condition assessment, it is
important to confirm whether geotechnical
information is available relative to the
design, construction, and operational
performance of the impoundment. For
example, is there documentation of the
characteristics of the material underlying the
dam foundation, is the base of an
impoundment dam keyed into bedrock, and is
there information on dam construction
material and design, construction quality
assurance/quality control (QA/QC), and
operational and closure monitoring? It is a
best practice to compare design information
to as-built diagrams (if they exist) to identify
design deviations. If such information is
available, the investigation team may use it
as an important element in assessing
impoundment conditions.
Structures identified as dams by states
are listed in the National Inventory of
Exhibit 1. Condition Assessment Decision Logic
No need for
geotechnical
investigation
Is there an imminent
risk of possible failure?
Take action to
address risk
Conduct
contingencies,
notifications and
emergency actions
No need to complete
geotechnical
investigation
Perform a
geotechnical
investigation to
assess stability
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Dams (NID) and assigned a NID number. Each NID dam is given a hazard classification (high,
significant, or low) that is based on the size of the dam and the potential for life loss and economic
damage should it fail. It is best practice to consult with state dam safety officials to determine whether an
impoundment dam is listed in the NID.
Visual assessment of the impoundment alone will not provide enough information to assess a unit's
structural stability. Documents and data to consider for review include:
Documentation of the general history of the mine and impoundments.
Regulatory status of the impoundment, including the NID hazard classification, if available.
Historical site layout and topographic maps.
Records of past releases, breaches, or failures.
Engineering specifications packages and construction QA/QC data (impoundment design and as-
built drawings).
Historical site investigation reports:
o State dam inspection and studies of structural stability, hazards, or condition ratings;
o Archived state, U.S. Bureau of Mines, and MSHA reports;
o Geotechnical and laboratory studies of the impoundment dam and impounded waste;
o Structural ratings during impoundment operation;
o Hydrology and hydraulic studies;
o Past environmental studies by federal, state, or local authorities;
o Geological or geochemical studies; and
o Historical operations, maintenance, and closure performance reports (including tailings
deposition records from the operating phase).
Historical instrumentation records (including inflow and suspended solids deposition rates,
deformation, pore water pressure, piezometer data, inclinometer reports, and surface monument
survey data, if available).
Aerial photos and satellite imagery.
Topographic, seismic hazard, and flood maps.
Soil boring and sampling results, laboratory test results, and cone penetration (or penetrometer)
testing (CPT) data (particularly lithologic logs of borings).
Maps showing nearby residences, businesses, agriculture, water supply wells, wetlands, streams,
rivers, ponds, and lakes;
Available structural or geotechnical modeling of the abandoned mine impoundments.
National Oceanic and Atmospheric Administration (NOAA) historical precipitation records.
Published journal articles, published master's or doctoral theses or other academic publications
evaluating dams or impoundments at the site.
Interviews with past operators.
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Review of historical data and analysis of prior site studies will typically help determine the composition
of surface impoundment liquids and wastes, provide information on impoundment design, and confirm
whether there had been impoundment failures. In cases where historical data from instrumentation do not
exist, are incomplete, or cannot be located, consultation with local, state, tribal, or federal officials and
state mining associations is paramount to ensure that relevant studies and prior actions at the site have
been identified and that conditions at the site are understood. Consultation with state agencies (for
example, the state dam safety division and the state mine land reclamation department) are also valuable
for obtaining information on any previously identified safety issue. Federal land management agencies
may also possess prior studies on the uses and conditions of impoundments at sites located on federal or
tribal lands or at mixed-ownership sites (sites located on both public and private lands). Consultations
with local government agency officials, as well as with nearby community residents, retired miners, mine
historians, and landowners, often yield relevant information about the site.
2.1.2 Conduct a Site Visit and Visual Assessment
The next step in an initial condition assessment is to conduct a site visit and visual assessment of the
abandoned mine impoundment. The visual assessment is performed during a site visit to gather
information to update the impoundment CSM. The visual assessment is key to confirming the conditions
of the impoundment and evaluating whether the proposed CERCLA actions could have an adverse impact
on the impoundment. A site visit has multiple purposes, including to (1) determine whether the
impoundment shows visual signs of imminent failure and, if so, recommend any appropriate mitigation
actions; (2) orient the investigation team to current conditions at the site and surrounding environment;
(3) estimate the type and nature of materials contained (or suspected to be contained) in the
impoundment; (4) assess the general condition
of the impoundment structures; (5) assess
whether the impoundment is likely to be
adversely affected by a proposed CERCLA
activity; (6) determine whether invasive
geotechnical studies would be helpful to assess
the structural stability of the impoundment;
(7) evaluate whether any immediate mitigation
actions might improve surface impoundment
and dam stability; and (8) determine, if
possible, why the impoundment no longer
retains liquids or wastes. To support these
findings, a site visit identifies any obvious
locations of distress, malfunctions of the
impoundment and appurtenant structures (such
as outlet structures), and evidence of hydraulic
management structures passing through the
impoundment (MAC 2011). Exhibit 2 provides
a discussion of using UAS for conducting
initial impoundment condition assessments.7
7 UAS use will be consistent with Agency Policy and Office of Land and Emergency Management UAS procedures.
Exhibit 2. Unmanned Aerial Systems Use in Initial
Impoundment Condition Assessments
A best practice is to use Unmanned Aerial Systems (UAS) to
gather baseline information about an abandoned mine
impoundment and the surrounding area. UAS can be effectively
used to visually survey site conditions to document potential
seepages, mine drainage, slope stability issues, and
impoundments structures. They can also provide imagery for
base maps, baseline conditions, potential safety hazards, and
field work planning. Information or data from UAS may also be
used as input into three-dimensional models and the conceptual
site model. Advantages of drone use includes:
Rapid deployment and data collection.
Ability to survey large areas.
Lower cost than other aerial imagery.
Finer scale aerial imagery than conventional aircraft.
Access to areas that are unsafe or unhealthy to people.
Documents current conditions from vantages unavailable at
ground level.
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Initial condition assessment and site visit documentation on each impoundment should include (see
FEMA 2015b):
1. A description of the impoundment, including location, type of construction, size, shape,
infrastructure, and age.
2. An assessment of the type and condition of impounded wastes; for example, slurry tailings, paste
tailings, dry tailings, tailings mixed with waste rock, or other wastes.
3. An estimate of the volume of impounded wastes (liquid, solid, and fluid-saturated) and the
remaining volume capacity of the impoundment, including consideration of freeboard for
flood management.
4. The status and condition of hydrologic structures; for example, spillways, drains, overflow
structures, outlet conduits, pumps, and relief wells.
5. Visual evidence of former hydrologic conditions and features, including water levels,
inflow/run-on locations, and outflow/runoff features.
6. The location, type, and condition of any monitoring instrumentation.
7. The weather conditions at the time of the site visit, including recent precipitation or storm
water inflow.
8. An estimate of the volume of sedimentation (for example, soils, silts, and sands from run-on)
if present.
9. Measurements of the impoundment slopes and geometry; for example, approximate grade, height,
length, crest width, and bench widths (particularly when as-built designs are absent).
10. Observations and evidence of the following impoundment conditions:
a. Settlement or slumping
b. Recent or frequent standing water (as visually indicated on embankment crests)
c. Visual evidence of movement
d. Overtopping
e. Erosion
f. Seepage or leakage (sometimes indicated by wetland vegetation)
g. Cracking
h. Rutting of surface soils
i. Deterioration
j. Presence of woody vegetation on embankments
k. Rodent burrows or activity on embankments
1. Unauthorized use (industrial or recreational) or vandalism
m. Upstream and downstream slopes and embankment crest condition
11. An assessment of the spillway and outfall structures to evaluate the adequacy of the hazard
potential rating design flow and whether there is sufficient storage within the impoundment to
avoid overtopping during a major storm event.
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12. Documentation or other evidence of adjacent or nearby underground mine workings.
13. A description of the watershed, including the location of the impoundment within the watershed,
topography, size of the catchment basin, and confirmation of reviewed runoff and infiltration
characteristics and downstream fluvial systems (for example, wetlands, streams, rivers, ponds,
and lakes).
14. A description of the impact of seasonal weather events; for example, estimated snow melt
loading, freeze-thaw events, and severe storm events.
15. The condition of upstream and downstream slopes, as well as the embankment crest.
16. The location of downstream areas of potential impact in the event of a release; for example, water
intake structures, residences, farms, schools, hospitals, daycare centers, businesses, and any other
at-risk infrastructure, and sensitive ecological features located along the flow path of a release
within at least 5 miles downstream of the impoundment.
17. Descriptions of each photo or video taken, including subject, date, time, direction of view, photo
number, geo-referencing, and photographer name.
Based on the information collected, the investigation team should evaluate whether the impoundment is
subject to imminent risk of failure. The following section further describes the steps in making such a
determination and the actions that should follow.
2.1.3 Make an Imminent Risk Determination and Decide if a Geotechnical Analysis
Is Needed
The goal of the site visit and visual assessment is to make an initial determination of whether an imminent
risk of failure exists or whether additional geotechnical data are needed to assess the risk of failure. The
key findings of the initial impoundment condition assessment (both the information/data review and the
site visit/visual assessment) should present answers to the following questions:
1. Are conditions such that there is a plausible risk of imminent dam failure or is there evidence of
deteriorating conditions that might, without intervention, lead to dam or impoundment failure?
2. Is the dam currently impounding liquids or liqueflable wastes?
3. Do the proposed CERCLA actions have the potential to cause a sudden, uncontrolled release?
4. Are the natural and physical attributes of the impoundment and its wastes adequately known to
assess whether an impoundment failure may occur as a result of CERCLA actions?
The answer to the first question should include an estimated failure risk category of immediate, urgent,
moderate-to-high, low-to-moderate, or low priority (BOR 2011). Immediate or urgent failure risk
categories should be supported by evidence of imminent failure or rapidly deteriorating conditions. If the
initial conditions assessment reveals evidence of imminent failure or rapidly deteriorating conditions that,
without intervention, would likely lead to failure, then the project manager should immediately notify the
appropriate management, local, state, tribal, and federal officials and implement necessary emergency
actions to mitigate the potential failure. No further actions at the site should be implemented until a
structural stability and safety analysis is performed by a qualified team or immediate action is taken to
reduce the risk of failure. During preparation of responses to a potential imminent failure, communication
with all interested parties should be maintained on a regular basis. Implementation of a CERCLA
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response to reduce the threat of an imminent failure should not be inconsistent with the NCP. FEMA's
Federal Guidelines for Dam Safety: Emergency Action Planning for Dams (FEMA 2013a) and the U.S.
Department of Homeland Security's (DHS) Dam Sector Crisis Management Handbook (DHS 2008)
should also be consulted prior to taking action.
If the initial conditions assessment does not identify an immediate or urgent failure risk category, then it
is necessary to determine whether additional data are needed. It is unlikely that geotechnical data will be
available to support a reliable estimate of an abandoned mine impoundment's structural stability. Under
such circumstances, performance of intrusive geotechnical investigations should be considered to collect
additional data as part of a structural stability and safety analysis (see Section 3.0).
A geotechnical investigation may not be recommended if (1) the document review and visual assessment
find that the impoundment is no longer capable of impounding liquids; (2) saturated wastes no longer
exist in the impoundment; or (3) the proposed CERCLA activities would not adversely affect the
impoundment's structural stability. However, if a geotechnical investigation is found to be unnecessary,
do not assume that the site no longer poses other human health and environmental concerns from the
contaminated waste materials. Abandoned mine impoundments not retaining fluids may still have the
potential to fail. Such a failure may not cause a sudden release but may still cause a release of wastes and
potentially hazardous substances.
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3.0 PERFORM STRUCTURAL STABILITY AND SAFETY ANALYSIS
When the initial impoundment condition assessment finds that the proposed CERCLA activities could
adversely affect an abandoned mine impoundment that is impounding fluids or potentially liquefiable
wastes, it is a best practice to evaluate whether the impoundment and dam are structurally sound enough
to withstand the effects of proposed invasive geotechnical studies. Abandoned mine impoundment
stability is determined under static, seismic, and liquefaction conditions. In the absence of existing data
and information, geotechnical investigations are the primary means of gathering data to support a
structural stability and safety analysis. While various terms are used to describe these geotechnical
investigations and analyses, this document refers to them as an impoundment structural stability and
safety analysis.
Structural stability and safety analyses are performed using best practices based on established methods.
FEMA, MSHA, and USACE have guidelines on how to conduct structural stability analyses of existing
earth and rock-fill dams (FEMA 2004; MSHA 2009; USACE 2002, 2003, 2004, 2014a, 2014b, 2014c).
ASDSO also has guidelines on how to conduct a dam safety inspection (ASDSO 2005; FEMA 2004).
This section includes the following subsections:
Section 3.1: Assemble a Qualified Investigation Team
Section 3.2: Plan and Conduct an Impoundment Geotechnical Investigation
Section 3.3: Determine the Hazard Potential Classification
Section 3.4: Evaluate the Hydraulic and Hydrologic Capacity
Section 3.5: Estimate the Factors of Safety
Section 3.6: Assign a Condition Rating
Section 3.7: Develop an Impoundment Structural Stability and Safety Report
3.1 Assemble a Qualified Investigation Team
Specialized knowledge, training, and experience are required to perform structural stability and safety
analyses of abandoned mine impoundments. Therefore, it is important that the qualifications of the
impoundment investigation team be confirmed before a structural stability and safety analysis is
undertaken. The specific makeup of the team is dependent on site conditions and state-specific
professional qualifications for conducting structural stability determinations of earth or rock-fill dams and
impoundments. Leading roles and common expertise requirements of investigation team members may
include the following.
Lead Geotechnical Engineer with a Professional Engineer (PE) license in the state of study and 10 or
more years of experience in dam structural stability studies (static, seismic, and liquefaction analyses) of
earth and rock-fill embankments. The lead geotechnical engineer typically signs the final geotechnical
investigation report and stamps it with a PE seal. A second geotechnical engineer with PE license may be
included on the investigation team, depending on the level of involvement of the lead geotechnical
engineer.
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Hydrologist with a Professional Hydrologist (PH) license in the state of study and 10 or more years of
experience in assessing site hydrology and hydrogeology.
Mining Geologist with a Professional Geologist (PG) license in the state of study and 10 or more years of
experience in the evaluation of impoundments.
Hydrologic Engineer with a PE license in the state of study and 10 or more years of experience
evaluating stream hydrographs and assessing precipitation impacts on catchment basins and generation.
Site visits should have no less than two professionals to assure that conditions can be cross verified in the
field. It is a best practice that the team consult with state dam safety officials for guidance on
state-specific planning for impoundment safety studies and to inform whether team personnel have the
recommended and applicable requisite academic training, licensure, and qualifications to
perform activities in that state.
When an agency or other responsible organization does not have the internal qualifications or expertise to
form a qualified team or does not have the proper equipment to conduct investigation activities,
outsourcing the structural stability and safety analysis may be appropriate. In this case, the information in
this section can be used to support efforts to oversee the contractor(s) or other agency performing
the investigation.
3.2 Plan and Conduct an Impoundment Geotechnical Investigation
The primary purpose of an impoundment geotechnical investigation is to collect samples and conduct
in situ measurements of impoundment construction materials and impounded wastes for geotechnical
analysis and to install instrumentation to monitor conditions before, during, and after CERCLA actions as
required by an approved Sampling and Analysis Plan/Quality Assurance Project Plan (SAP/QAPP). The
technologies and methods to be used in the geotechnical investigation should be selected based on site-
specific data and conditions and only after analyzing the risks of performing invasive activities.
This section includes the following subsections:
Section 3.2.1: Conduct a Data Gap Analysis and Second Site Visit
Section 3.2.2: Develop a Geotechnical Investigation Plan
Section 3.2.3: Analyze the Risks of the Proposed Geotechnical Investigations
Section 3.2.4: Develop a Contingency, Notification, and Emergency Action Plan for the
Proposed Intrusive Geotechnical Activity
Section 3.2.5: Analyze the Geotechnical Data
3.2.1 Conduct a Data Gap Analysis and Additional Site Visits
The investigation team should conduct a data gap analysis of the CSM and additional site visits, as
appropriate, to confirm the information noted in the initial condition assessment and to determine where
and how geotechnical investigations will be performed. Abandoned mine impoundment site visit
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checklists guide information collection and observations for more thorough inspections and to support
investigation planning (see Appendix A).
Investigation team personnel should also collect and document any other helpful information to better
evaluate the structural stability of the surface impoundment. Exhibit 3 provides several sources of
information for conducting site visits. In addition to the sources in Exhibit 3, ASDSO may have
information sources and recommendations for conducting impoundment site visits.
Exhibit 3. Information Sources for Performing Impoundment Inspections
USACE. 2014. "Chapter 13: Reporting Evidence of Distress in Civil Works Structures." Engineering and
Design: Safety of Dams - Policy and Procedures. ER1110-2-1156. March 31.
www.publications.usace.army.mil/Portals/76/Publications/EngineerRegulations/ER_1110-2-1156.pdf.
ASDSO. 2016. "Module: Documenting and Reporting Findings from a Dam Safety Inspection." Training Aids
for Dam Safety, https://www.hsdl.org/?view&did=759064.
ASDSO online dam inspection guidance and training seminars.
Bureau of Reclamation. 1995. Safety Evaluation of Existing Dams Manual. Denver, Colorado: Bureau of
Reclamation.
Results of the site visits and the data gap analysis may indicate a rationale to perform a
geotechnical investigation to obtain data to support the structural stability and safety analysis. If the
data support a determination to collect additional geotechnical data, a geotechnical investigation plan
should be developed.
3.2.2 Develop a Geotechnical Investigation Plan
It is important to design a geotechnical investigation work plan that can be effectively and safely executed
by the field personnel and contractor(s) performing the work. A first step in developing a plan is to
determine if there are minimally invasive methods (such as geophysical methods) that could provide
relevant information in evaluating the stability of an abandoned mine impoundment. If such approaches
are not viable, then the use of invasive methods (such as drilling or excavation) may be appropriate.
Common geotechnical technologies and approaches include:
Geophysical Surveys. Typically, minimally invasive, geophysical surveys include methods of
collecting remote sensing-type data to detect and map subsurface features and conditions.
Geophysical survey methods, such as ground penetrating radar (GPR), electromagnetometry,
magnetometry, and resistivity, can be performed at the ground surface and are viewed as
minimally invasive. Satellite-based remote sensing technologies (for example, interferometric
synthetic-aperture radar [InSAR] and light detection and ranging [LIDAR]), which are also not
invasive, can provide an assessment of past deformations if adequate historical data are available.
Other surface geophysical methods, such as seismic reflection, may be deployed using vibratory
or sonic technologies, which, while considered minimally invasive, may disrupt unstable
unconsolidated materials. Geophysical surveys are often used to minimize invasive exploration
methods, such as drilling and excavation, but some drilling is often required to confirm and
calibrate geophysical survey results. Geophysical surveys can also identify critical locations for
the placement of drill holes.
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Drilling (Boring or Coring) and Sounding. Considered to be the primary sample collection and
in situ testing method for geotechnical analysis, drilling is performed to (1) confirm the presence,
depth, and hydraulic head of impounded water or liquids; (2) obtain discrete or continuous in situ
measurements of subsurface conditions for correlation with geotechnical parameters of interest;
(3) collect samples to establish the physical and geochemical characteristics of impounded waste
and dam materials of construction; (4) collect samples for analysis to determine the physical
characteristics of the underlying geology; and (5) collect samples to determine groundwater
geochemistry. There are a variety of drilling methods available that provide flexibility in
investigation design and allow for the installation of instrumentation (such as piezometers and
inclinometers) and in situ testing (such as standard penetration test [SPT] and permeability
testing). Drilling tools and technologies can also accommodate variable site conditions. Drilling is
typically considered an invasive activity because it has the potential to result in impoundment
instability and failure.
Excavation. Subsurface excavation is used to dig test pits and test trenches to provide access for
obtaining visual confirmation, collecting samples, and conducting in situ field testing. Excavation
may be an appropriate primary geotechnical investigation method in certain circumstances, such
as confirming foundation materials and how or if a dam's foundation is keyed into bedrock.
Excavation is considered an invasive activity; therefore, planned excavation activities should be
evaluated for their potential to result in impoundment instability or failure.
Field Testing, Instrumentation, and Monitoring. A variety of specialty instruments and
methods are used for testing material, fluid, and physical properties. Field testing methods and
instruments include groundwater monitoring wells; hydraulic pressure testing in boreholes;
seepage measurement using weirs, flow meters, and flumes; thermistors for measuring
groundwater temperature variations; and extensometers and inclinometers for measuring material
displacement and deformation. Most of these methods are minimally invasive unless deployed by
creating boreholes or excavations.
The geotechnical investigation work plan should assess the site conditions and risks to ensure that
investigation activities can be safely performed. Low strength or saturated material may not be able to
support personnel or equipment. Tailings can also lose strength because of the vibratory stress from
drilling or excavating, resulting in a threat to equipment and personnel. If internal erosion is suspected,
the work plan should also consider the potential for voids beneath the tailings surface. Environmental
factors should also be taken into account during the planning for field analysis as exposure of reduced
material can result in geochemical changes in mine drainage release. In addition, erosion of stockpiles
created during excavation or exposure of buried decant structures could impact surface water and
sediment quality. Health monitoring and safety planning and practices, along with environmental
protection controls, should be part of any plan.
The selection of geotechnical investigation methods and instruments is a significant aspect of
geotechnical investigation work planning. Typically, geotechnical investigations involve drilling and
excavation, both of which are considered invasive activities. To complete the geotechnical investigation
plan, the geotechnical team should select the drilling and excavation technologies most appropriate for the
data requirements and amenable to site conditions, including site access, slope, and ground stability. A
combination of techniques may be required to characterize abandoned dams and impoundments. Many
small, lightweight drill rigs and excavators can be deployed on tracks and adjustable platforms to work on
less stable ground and on steep slopes. However, significant care is required in selecting the appropriate
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drilling rig or excavator to safely accommodate site-specific conditions. It is important to acknowledge
that drilling and excavation may have different types of risks associated with their use.
3.2.2.1 Drilling Methods and Instruments
The most common geotechnical drilling methods are traditional auger drilling, hydraulic rotary drilling,
and the use of direct push technology (DPT). Specific instruments may be deployed with different drilling
techniques. Common drilling and testing methods8 for abandoned mine impoundment geotechnical
investigations include:
Hollow Stem Auger (HSA) Drilling. This method is generally fast, especially in shallow
applications, in soft unconsolidated material, or in weak weathered bedrock. HSA drilling is
effective for collecting samples to characterize soils, unconsolidated overburden, and tailings
associated with earthen dams and impoundments. A conventional and cost-effective drilling
method, HSA drilling uses a rotating HSA to convey cuttings to the surface via auger flights on
the outside of the casing. Grab samples can be obtained from cuttings or sampling tools deployed
inside the hollow auger flights. The large openings formed during HSA drilling allow access to
the bottom of the borehole after the pilot bit is removed without withdrawing the auger drill
string. The auger acts as a temporary casing during drilling to facilitate sampling soils and
unconsolidated material and installing monitoring wells. HSA drilling produces coarse cuttings
that can be readily observed and characterized; thus, HSA drilling is the most common method of
drilling for geotechnical investigations. Advantages for this method are that HSA drilling does
not use downhole liquids to facilitate drilling and does not grind rock or soil to fine particle sizes.
A disadvantage is that HSA drilling cannot penetrate many types of hard rock. Continuous
sampling for geotechnical investigations is described in American Society for Testing and
Materials (ASTM) International Standard D6151 (ASTM 2008). FERC considers HSA drilling a
preferred method for drilling in impoundments (FERC 2016a).
Continuous Flight Auger Drilling. This method uses a spiral auger that is advanced into the
ground via rotation and then lifted out. Soil is driven to the surface or the blades are removed and
the soil remaining on the blades is collected for analysis. Soil removed by continuous flight
augers is considered disturbed. If enough clay or binding material is present in the formation, the
hole will remain open when the augers are removed. Dry or saturated sands and other caving
formations may be problematic for this technique.
Fluid (Mud) Rotary Drilling. This method is commonly used to drill through hard or
comparably unweathered rock that cannot be drilled using augers. This drilling method is
typically used for assessing the geotechnical characteristics of rock materials beneath
impoundments. The technology can use a variety of drill bit types (for example,
diamond-impregnated, carbide core barrel, or tri-cone roller) and uses a mud/bentonite-based
fluid to cool and clean the bit, capture and carry cuttings up the annular space to the ground
surface, and help prevent cave-in of open boreholes. Disadvantages of this method for
impoundment drilling are that a mud pit or tank is necessary to capture, clean, and circulate
drilling fluids, and pumping fluids into impoundment waste or dams may cause instability. Since
drilling fluid is used, this method also has a potential for hydraulic fracturing. Drill bits used in
8 Additional information about the risks of drilling is noted in FERC's Guidelines for Drilling in and near Embankment Dams
and Their Foundations 2016a.
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this method grind up the subsurface materials, which then becomes coated with drilling fluid,
making proper characterization of the materials difficult. USACE (2014c) notes that the use of
fluid drilling should be limited only to locations where there is high confidence that it will not
cause hydraulic fracturing. However, fluid rotary is the preferred method for SPTs for
liquefaction (ASTM D6066), where it is recommended to keep the hole full of fluid during the
test to stabilize sands. Drill bits, sampling tools, and drill rods should be raised and lowered
slowly so as not to induce increased positive or negative fluid pressures.
Air Rotary Drilling. This method utilizes compressed air to lift the cuttings up the borehole and
to cool the bit. Air rotary drilling is used when possible for environmental monitoring because no
drilling fluids are introduced into the formation. This method is feasible only in consolidated or
semi-consolidated formations.
Sonic Drilling. This method has the appearance of rotary drilling, but it uses a vibratory drill bit
that physically vibrates up and down in addition to being pushed down and rotated. These three
combined forces allow drilling to proceed rapidly through most geological formations, including
most types of rock. The vibratory action causes the surrounding soil particles to liquify thereby
allowing penetration. Sonic drilling and coring may be accomplished without the use of any
drilling fluids.
Direct Push Technology. DPT can provide valuable in situ data and information about tailings
and unconsolidated earthen materials in an impoundment. Discrete soil sampling devices, such as
Shelby tubes and continuous liner soil samplers, can be affixed to a DPT drilling rod to obtain
samples for laboratory analysis. CPT, flat plate dilatometer test, and SPT (ASTM D1586-11)
equipment can also be affixed to a DPT drilling rod and advanced into the subsurface to collect
real-time, in situ geotechnical data. Advantages to DPT technologies include the use of lighter,
more mobile drill rigs, less subsurface impact, and real-time, fast results. Disadvantages are that
DPT tools cannot penetrate solid rock or very stiff and dense soils and can be difficult to advance
in rocky substrates. ASTM International Standard D5778 outlines standard procedures for
measuring the point resistance during penetration of subsurface soils (ASTM 2012a). Instruments
used to monitor water pressure in soil or rock, such as vibrating wire piezometers or other
piezometers, can be installed using DPT.
Cone Penetrating (or Penetrometer) Testing. This test method consists of pushing (typically
using DPT) an instrumented cone into the ground at a controlled rate (controlled between 1.5 to
2.5 centimeters per second). CPT piezocone, inclinometer, seismic geophone, resistivity,
electrical conductivity, dielectric, and temperature sensors may be used to measure geotechnical
properties of impoundments in real time as the cone is advanced through the material to be
measured. CPT is useful in pore pressure measurements and is an essential tool to assess the
potential for wastes to liquefy. Pile load tests can be conducted with CPT equipment measures to
determine end bearing and side friction (ASTM Standard D3441) (ASTM 2016c).
Decisions about drilling methods and technologies should consider the goals of the drilling program,
including safety, data requirements, access, strata type, surface slope stability, and other factors such as
drill rig capability, cost per foot, and availability and experience of the drilling crew. Slope, ground
stability, and physical accessibility commonly limit the size and type of the drill rig that can be deployed.
These issues may also prevent vertical drilling from directly on top of the impoundment or dam. Under
such circumstances, other drilling methods, such as horizontal or directional drilling, may be considered.
In addition, some track-mounted, walking, and all-terrain "spider" rigs can drill on steeper slopes.
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When planning a geotechnical investigation, it is valuable to select drilling locations and directional
drilling azimuths and inclinations to adequately characterize impoundment materials of construction
while avoiding buried impoundment infrastructure, such as drain pipes and liners. Instrumentation types
and their installation requirements also inform the drilling plan. As noted earlier, geophysical surveys can
also identify critical locations for the placement of drill holes.
Simple horizontal drilling (or drilling inclined from vertical) should not be confused with horizontal
directional or angular drilling, which is a steerable, trenchless method of installing underground pipe,
conduit, or cable in a shallow arc along a prescribed bore path through soils (not rock). Horizontal drilling
may be an effective method for drilling from the sides of impoundments or to obtain a cross-sectional
analysis of impounded waste.
If not properly designed, drilling and sampling may contribute to structural failures. The methods used to
collect samples is a site-specific determination made by a qualified geotechnical engineer. Exhibit 4
provides two important resources for drilling programs in impoundments.
Exhibit 4. Resources for Impoundment Drilling
U.S. Army Corps of Engineers. 2014. "Drilling in Earth Embankment Dams and Levees." ER-1110-1-1807.
http://www.publications.usace.army.mil/Portals/76/Publications/EngineerRegulations/ER_1110-1-1807.pdf.
Federal Energy Regulatory Commission. 2016. "Guidelines for Drilling in and near Embankment Dams and
Their Foundations." Division of Dam Safety and Inspections. Version 3.1. June.
https://www.ferc.gov/sites/default/files/2020-04/guidelines.pdf.
Borings should be advanced to depths adequate for defining impounded waste, impoundment materials of
construction, and natural substrate. Borings should be advanced at the top and bottom of slopes if
possible. The number of borings required depends on the continuity and homogeneity of the soil and
waste conditions and the extent of the possible issues of concern. Accurate surveying and an
understanding of the local structural geology, lithology, and impoundment design help support planning
efforts so that drilling will not contribute to a failure or adversely affect infrastructure. Driller experience,
including knowledge of local geology and drilling conditions, also increases the likelihood of a successful
drilling program. Exhibit 5 provides a list of
the contents for a FERC drilling program
plan for drilling in or near embankment
dams and foundations (FERC 2016a).
While it is considered a best practice to use
non-fluid drilling methods whenever
possible, the choice of a specific drilling
method at a site depends on that site's
geotechnical characteristics. While drilling
with fluids raises concerns, it should not be
automatically rejected if drilling can be
accomplished without causing structural
stability issues. Therefore, prior to any
drilling using fluids, the proposed drilling
plan should be reviewed and approved by a
Exhibit 5. Federal Energy Regulatory Commission
Drilling Program Plan Required Content
1. Provide the name and a description of project.
2. Describe the purpose of the site-disturbing activity.
3. Describe the proposed site-exploration activity (including coring
locations, depths, in situ testing, and instrument installation).
4. Describe and show anticipated site conditions.
5. Describe the proposed equipment, methods, and processes.
6. Identify the project personnel and qualifications/experience.
7. Identify and describe the potential risks from invasive activities and
a risk management plan.
8. Identify a communication plan with names and phone numbers.
9. Provide an overall schedule and duration of drilling activities.
Source: Federal Energy Regulatory Commission. 2016. "Guidelines for
Drilling in and near Embankment Dams and Their Foundations." Division of
Dam Safety and Inspections. Version 3.1. June.
https://www.ferc.gov/sites/default/files/2020-04/guidelines.pdf.
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licensed geotechnical engineer who has experience with fluid drilling into embankments to avoid the risk
of hydrofracture or other failure modes.
USACE (2014c) recommends drilling be performed by drill rig operators with working knowledge of
USACE and state drilling guidelines and with a minimum of 5 years of experience drilling with the
equipment and following drilling program plan procedures. All drilling operations on abandoned mine
impoundments should be conducted in the presence of a licensed PE or PG who will be responsible for
monitoring the integrity of the impoundment during these invasive activities.
3.2.2.2 Excavation Methods
The excavation method used for geotechnical investigations will vary by site and strategic approaches to
excavation, including the use of shoring, which may be required to assist in characterizing abandoned
mine impoundments. Excavators vary significantly in size, weight, and length of excavation reach. Many
excavators are deployed on all-terrain tires or tracks and adjustable platforms to enable work on the side
of steep slopes.
Depending on the depth of excavation and worker access for sampling and testing activities, there may be
potential health and safety risks associated with excavation efforts that should be addressed during
geotechnical investigation planning and included in an approved Health and Safety Plan (HASP). Risks of
cave-ins and slope failure may be mitigated using sloping, benching, shoring, and other techniques.
Specialists familiar with the technical and regulatory requirements associated with excavation in unstable
terrain and confined-space environments should be included in the planning efforts.
3.2.3 Analyze the Risks of the Proposed Geotechnical Investigations
Because drilling and excavation are invasive activities, it is recommended that a risk analysis (sometimes
referred to as the drilling/excavation plan) for the geotechnical investigation be conducted. The risk
analysis should identify the potential failure modes (PFM), the triggering events associated with the
drilling or excavation plans, and the likelihood of a sudden, uncontrolled release of impounded liquids or
wastes event, the severity of its consequences, and any potentially affected receptors.
Failure risk assessments and FMEAs are two risk analysis methods that can be used to evaluate whether a
proposed geotechnical investigation could cause a failure of the abandoned mine impoundment (BOR and
USACE 2015; FERC 2016b; USACE 2014b). Because PFMs vary for each proposed invasive method
and for each abandoned mine impoundment, a risk analysis can involve different levels of detail when
assessing how a proposed invasive method may impact an abandoned mine impoundment. A FMEA is
generally more detailed and formal than a failure risk assessment and is used when the risks are likely to
be high and when the risk analysis indicates more extensive examination may be warranted. The risk
analysis can be either qualitative or quantitative. The determination of whether the risk analysis will be
qualitative or quantitative should be based on the professional judgment of the planning team, considering
potential consequences and available information. While the results of a FMEA are typically documented
in a separate FMEA report, a failure risk assessment may be incorporated as a section or appendix in the
drilling plan.
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Risk analysis results should be provided to responsible
personnel in each organization that will be involved in
drilling or excavation to ensure that each organization is
fully aware of the risks and consequences and that work
proceeds collaboratively to mitigate and manage those
risks. Suggested mitigation measures are identified to
manage the risk of failure and impacts by reducing the
likelihood of occurrence or the severity of the
consequence or both. Exhibit 6 provides some examples
of PFMs from drilling that may contribute to
impoundment failure; similar PFMs exist for excavation.
A FMEA typically requires participation of a
multi-disciplinary team with diverse knowledge of mining
and civil engineering; impoundment design and mechanics; environmental site investigation and
remediation; geology and hydrogeology; emergency action planning and response; general mine site
safety; and other expertise as relevant to the impoundment or site conditions. The scale of the FMEA
effort should be proportional to the diversity and degree of potential drilling-related risks associated with
the current conditions of the impoundment.
A worksheet may be used to guide and document the FMEA effort and typically contains the
following elements:
Identifying and numbering task and components.
Identifying PFMs.
Identifying triggering events.
Identifying potential failure consequences and assigning a severity rating from negligible to high.
Potential failure consequences range from no significant economic, environmental, or human
impact at the low end of the spectrum to loss of life at the high end of the spectrum (BOR 2008).
Assessing the confidence in the risk analysis as low, medium, or high. The confidence level of the
failure risk analysis can indicate whether additional evaluation is necessary to predict both the
risk and mitigation measures to reduce risk.
Identifying worker and health safety risks.
Identifying mitigation measures.
A FMEA provides a hierarchy of risks posed by each PFM. A risk matrix is typically used to present the
likelihood of a failure occurring with the consequences of the failure to identify the highest priority tasks
or components requiring mitigations. Exhibit 7 provides an example of a FMEA risk categorization
matrix, which can be modified for project and stakeholder needs as warranted.
Exhibit 6. Examples of Drilling-Related
Potential Failure Modes
Drilling vibration liquefying soil or other material
workings blockages.
Failure of soil, rock, or waste material under
drilling equipment.
Piping of impounded water around drill
steel/augers in unconsolidated material.
Rapid changes in hydraulic head pressure.
Rupture of drains causing liquefied waste to
escape via drain pipes.
Weight of drilling or construction equipment.
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Exhibit 7. Example FMEA Risk Categorization Matrix
Failure Likelihood
Unlikely
Low
Moderate
High
<1>
k
_3
LL.
O
Ui
3
a-
O)
V)
£
O
o
Low
Negligible
Note:
FMEA Failure modes and effects analysis
Source: Bureau of Reclamation. 2008. "Leadville Mine Drainage Tunnel Risk Assessment:
Leadville Mine and Drainage Tunnel Project, Colorado, Great Plains Region." November.
https://www.usbr.gov/gp/ecao/leadville/combined_risk_assessment.pdf.
The colors in Exhibit 7 indicate the hierarchy of risk as follows:
Red - Extreme risk
Orange - High risk
Yellow - Moderate risk
Green - Tolerable risk
Blue - Well within tolerable limits
Activities that present a high or moderate failure likelihood of an uncontrolled release should not be
undertaken unless there is certainty that the consequences are negligible or can be controlled through
effective contingency measures. Recommended mitigation actions are developed based on the level of
risk starting with high (red) and working down to unlikely (green or blue). Site-specific conditions are
used to adjust the ranking of risk determinations because, in some cases, the severity of consequences
may make even a negligible likelihood of consequences unacceptable.
While described in this document as best practices for drilling and excavation risk analysis, FMEAs and
risk assessments are not the only methods of failure, reliability, or dependability risk analysis. Other risk
analysis methods include (1) preliminary hazard analyses and functional failure analyses, which may be
effective for identifying PFMs; (2) common cause analyses, which allow for the evaluation of risks posed
by multiple, concurrent failure modes; and (3) event tree analyses (ETA), which can be used to identify
all failure sequences, including assessing probabilities and consequences of outcomes that follow an
initiating event. ETAs can also be used to test the PFMs for specific actions or events potentially affecting
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the impoundment system (Kaplan and others 1999). Additional information on how to assess risks at
dams are noted by BOR and USACE (2015), USACE (2014b), and FERC (2016b).
Uncertainty will be associated with missing information, measurement inaccuracy, and human error used
to assess PFM-related risks. An appropriate level of conservatism should generally be considered based
on the level of uncertainty for each PFM analysis.
3.2.4 Develop a Contingency, Notification, and Emergency Action Plan for the Proposed
Intrusive Geotechnical Activity
It is a best practice that a carefully developed Contingency, Notification, and Emergency Action Plan
(CNEAP) be prepared or updated for all proposed invasive activities supporting a geotechnical
investigation, particularly for drilling and excavation. The CNEAP is more commonly known as an
Emergency Preparedness and Response Plan (EPRP) in the mining industry. The CNEAP (or similar
documentation) serves as the key document for comprehensive contingency, notifications, and emergency
action planning for planned site activities. The CNEAP has three elements: a contingency plan, a
notification plan, and an emergency action plan.
The CNEAP is a high-level plan that coordinates site activities with local and regional response teams in
the event of a potential failure. The CNEAP should be based on activity specific risk analysis, adaptive
management processes related to the activity, and activity related risk mitigation procedures. The CNEAP
should also assess how long it may take to reach receptors should a sudden release occur.
The CNEAP evaluates if there are risks from the geochemical nature of the impounded liquids and
wastes. In some circumstances, these liquids or wastes may present specific risks if released and may
require special worker health and safety training to address those risks. Another important element of the
CNEAP is the hazard potential classification of the abandoned mine impoundment since such
classification indicates the potential severity of the failure of the impoundment. The CNEAP should also
consider how the placement of heavy equipment could adversely affect the bearing capacity of the
impoundment surface and pose a threat to worker safety.
It is best practice to have all other site documents that address related topics defer to and reference the
CNEAP, including site cleanup-related work plans, such as field sampling plans, quality assurance project
plans, remedial designs, technical specifications for drilling and construction, monitoring plans, project
management plans, and health and safety plans. Development or modifications to the CNEAP should be
directly supported by the results of the risk analysis performed to identify and manage risks associated
with the proposed geotechnical study. Conditions at the time of the risk analysis should be confirmed
during contingency and emergency action planning and again when geotechnical studies are being
initiated. All site personnel should be familiar with and be tested on the contents of the CNEAP before
work is initiated to ensure that emergency action procedures are understood and followed.
Adaptive management planning principles are a best practice to apply when developing the CNEAP.
Comprehensive monitoring and data collection help field managers adapt their knowledge of site
conditions in an iterative learning process while enhancing their understanding of the risks. All site
personnel should be familiar with the contents of the CNEAP before work is initiated to ensure that
adaptive management principles are considered across the project.
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3.2.4.1 Contingency Plan
Contingency plans typically focus on the types of emergencies that could occur, the potential impacts of
such an emergency, and the existing engineering controls (EC) and other actions that should be
implemented to mitigate or partially mitigate the consequences of such an emergency. ECs should be in
place for proposed invasive geotechnical activities, but will also pertain to other site activities, such as
abatement of water pollution, erosion protection, and sedimentation control. Contingency plans assess
how the site will manage impacts from extreme events, such as high rainfall occurrences or earthquakes,
and estimate how long it may take for a release to reach critical infrastructure or population centers
depending on the type of release (saturated tailings or precipitation/impounded water enhanced mudflow),
the likely impacts of a release, and the notification team response time.
While this document identifies some best practices for preventing impoundment failures, it does not
provide an exhaustive treatment of this topic. Contingency plans for invasive activities to be conducted at
abandoned mine impoundments include the following elements:
Providing a list of training or qualifications required for personnel responsible for leading and
supporting notifications and emergency action efforts.
Planning and documenting contingencies to control and mitigate minor uncontrolled releases of
liquids or liquefied impoundment waste that do not pose significant risk to human health or
the environment.
Developing or updating a breach or failure analysis completed to the level appropriate for the
triggering event.
Planning and documenting approaches to mitigate an impoundment failure, including
o Calculating the maximum potential impoundment liquid and waste volumes;
o Mapping inundation assuming various failure scenarios;
o Calculating the time it would take to reach receptors assuming various failure scenarios;
o Evaluating the site infrastructure's ability to contain the maximum potential waste volume;
o Characterizing, testing, and analyzing the abandoned mine impoundments;
o Considering safeguards to implement should a failure occur (for example, buttressing,
channelization, use of geotextiles to reduce erosion, or other stability safeguards);
o Evaluating the suitability of the site's footprint and topography for increasing containment
capacity; and
o Recommending solutions for containment capacity increases (for example, the expansion of
existing containment ponds or downstream dams).
Installing monuments or deflection sensors to monitor potential movement in the dam face or
impoundment walls.
Monitoring changes in impoundment discharge rates and water quality at discharge points or dam
toe during and after invasive activities.
Using the risk analysis to inform mitigation measures and as the basis for developing instructions
related to contingencies and emergency response action requirements and procedures.
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3.2.4.2 Notification Plan
It is a best practice to develop a comprehensive notification plan that addresses all future activities at a
site with known or potential risks of an impoundment failure. Notifications may vary depending on the
type of emergency at the site. It is important that notification plans for possible impoundment failures
include notifications for responders and downstream receptors, such as names and contact information.
Site personnel should be familiar with the site CNEAP (or similar documentation) and have reliable
telecommunication capabilities to support immediate notifications (for example, satellite phones in
remote areas without cell phone coverage).
3.2.4.3 Emergency A ction Plan
Emergency action plans may include the following content (based partially on FEMA 2013a):
A list of possible events that could cause an impoundment failure or breach. For each possible
event, emergency actions are specified, including the responsible personnel, resources, and
equipment required.
A notification tree identifying what emergency response agencies will be called in the event of an
impoundment failure.
Site personnel mustering plan and designated locations to ensure protection of human health and
safety in the event of a release or pending release.
Updated maps that depict site roads, features, infrastructure, and areas of sensitive and hazardous
or dangerous environments, including protected areas and steep or heavily forested topography.
Maps should also indicate areas of likely inundation.
An inventory of chemicals and fuels stored on site so that responders will know how to neutralize
or clean up such chemicals or fuel in the event of a sudden release. It is recommended that all
hazardous material storage, equipment storage, offices, and other important infrastructure be
located out of the area of impact from any impoundment failure.
How to address specific risks related to the geochemical nature of impounded liquids or wastes.
Inspection forms, plan views, and associated details, including corrective and maintenance action
procedures, for pertinent features such as detention ponds.
Procedures to ensure that off-site first responders tour a site before high-risk work is started to
increase their preparedness to respond in the event of a serious incident and to provide off-site
responders notice of such high-risk work activities.
Contact informational training for emergency responders.
A list of experts or service vendors for specialty technologies to be used for high-risk activities,
as well as notification procedures to ensure that such vendors are on call or on site (as applicable)
to assist with their technologies during such high-risk activities.
To be effective, emergency action plans should be tested regularly (through exercises or drills) and
updated, including the incorporation of lessons learned.
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3.2.5 Analyze the Geotechnical Data
The results of the geotechnical field and laboratory tests listed in Exhibit 8 can be used to validate or
modify the geotechnical parameters. Geotechnical parameters are used to provide the quantitative basis
for evaluating the structural stability of an abandoned mine impoundment and their vulnerability to PFMs
under applied loadings (for example, the undrained strength of the weakest soil layer of concern).
Laboratory results from invasive geotechnical activities, minimally invasive survey data, observations
from site visits, and data from instrumentation can be used by the investigation team to complete
structural stability and safety analysis, including determining the hazard potential classification, condition
rating, and FOS.
Exhibit 8. Common Field and Laboratory Soil Test Methods1
Test Method Name
Method Number
Purpose
Field Tests
Standard Penetration Test (SPT) and
Split-Barrel Sampling of Soils
ASTM D1586
Provides a disturbed soil sample for moisture content
determination, identification and classification, and
laboratory tests.
Standard Test Method for Mechanical
Cone Penetration Test of Soil
ASTM 3441
Test method for determining end bearing and side friction,
the components of penetration resistance.
Electronic Friction Cone and Piezocone
Penetration Testing of Soils
ASTM D5778
Rapid evaluation of stratigraphy, including heterogeneity, to
estimate soil classification and correlate with soil
engineering properties.
Pocket Penetrometer
ASTM WK27337
(Under
development)
Rapid quantification of soil compressive strength.
Field Vane Shear Test in Saturated
Fine-Grained Soils
ASTM D2573
Evaluation of rapid loading strength for total stress analysis
of saturated fine-grained clays and silts, mine tailings, and
organic muck.
Laboratory Tests
Particle-Size Analysis of Soils
ASTM D422
(Withdrawn in
2016, pending
update)
Quantitative determination of the distribution of particle
sizes in soils.
Liquid Limit, Plastic Limit, and Plasticity
Index of Soils (Atterberg Limits)
ASTM D4318
Characterization of the fine-grained fractions of soils to
specify the fine-grained fraction of construction materials.
Soil Density (Unit Weight)
ASTM D7263
Determination of dry or bulk density to evaluate the degree
of materials compaction.
Direct Shear Test of Soils under
Consolidated Drained Conditions
ASTM D3080
Determination of the consolidated drained shear strength of
soil in direct shear.
Moisture Content of Soil and Rock by
Mass
ASTM D2216
Determination of water content to correlate soil behavior
and index properties, such as liquidity index, derived in
conjunction with ASTM D4318.
Laboratory Compaction Characteristics
of Soil Using Standard Effort
ASTM D698
Low-energy compaction test determination of soil
moisture-density relationship; generally, at a higher
optimum moisture content.
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Exhibit 8. Common Field and Laboratory Soil Test Methods1
Test Method Name
Method Number
Purpose
Laboratory Compaction Characteristics
of Soil Using Modified Effort
ASTM D1557
High-energy compaction test determination of soil
moisture-density relationship; generally, at a lower optimum
moisture content.
Unconfined Compressive Strength of
Cohesive Soils
ASTM D2166
Determination of unconfined compressive strength of
cohesive soil in undisturbed, remolded, or compacted
conditions.
Unconfined Compressive Strength and
Elastic Moduli of Intact Rock Core
ASTM D7012C
(Replaces D2938-
95)
Determination of unconfined compressive strength and
elasticity of intact rock under varying states of stress and
temperatures.
Consolidated Undrained Triaxial
Compression Test for Cohesive Soils
ASTM D4767
Determination of the consolidated undrained shear strength
of soil under changed conditions.
Consolidated Undrained Direct Simple
Shear Testing of Fine Grain Soils
ASTM D6528
Determination of shear strength under constant volume
conditions equivalent to undrained conditions for a
saturated specimen.
Miniature Vane Shear Test for Saturated
Fine-Grained Clayey Soil
ASTM D4648
Rapid estimation of undrained shear strength of
undisturbed, remolded, or reconstituted fine-grained soils.
One-Dimensional Consolidation
Properties of Soils Using Incremental
Loading
ASTM D2435
Estimation of the magnitude and rate of both differential
and total settlement of a structure or earthen fill.
One-Dimensional Consolidation
Properties of Saturated Cohesive Soils
Using Controlled-Strain Loading
ASTM D4186
Estimation of one-dimensional settlements, rates of
settlement associated with the dissipation of excess
pore-water pressure, and rates of fluid transport because of
hydraulic gradients.
Notes:
1 These "soil test methods" are recommend methods for impoundment geotechnical investigations. The lead geotechnical engineer
will choose which of these tests are appropriate based on site-specific conditions.
ASTM American Society for Testing and Materials
3.3 Determine the Hazard Potential Classification
It is a best practice that the investigation team should determine the hazard potential classification for
each abandoned mine impoundment under study. Hazard potential is an independent metric from the
condition and risk probability of a breach or failure of an abandoned mine impoundment. Hazard potential
classifications are not designed to evaluate the specific physical condition or structural stability of an
impoundment; rather, they are a rating of potential for harm (that is, the inferred consequence) should the
impoundment fail. Many states have developed and adopted their own hazard potential classification
criteria, but for national consistency, this best practices document relies on FEMA hazard potential
guidelines (FEMA 2004; USACE 2014b). If the dam is listed in the NID, it will have an assigned hazard
classification based on the size of the dam and the potential for life loss and economic damage should
it fail.
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Three hazard potential classifications describe the potential risk of sudden fluid or liquefiable releases
from abandoned mine impoundments:
High Hazard Potential failure results in probable loss of human life. High hazard potential
impoundments are typically located in areas with nearby populations.
Significant Hazard Potential failure results in no probable loss of human life, but can cause
economic loss, environment damage,9 disruption of lifeline facilities, or affect other concerns.
Significant hazard potential impoundments are often located in predominantly rural or
agricultural areas, but could be located in areas with population and significant infrastructure.
Low Hazard Potential failure results in no probable loss of human life and low economic or
environmental losses. Losses are principally limited to the owner's property.
3.4 Evaluate the Hydraulic and Hydrologic Capacity
Hydraulic and hydrologic (H&H) evaluations provide important inputs into determining FOS and the
condition rating. As part of the H&H evaluation, the impoundment, dam, impounded material, and
spillways are evaluated to determine whether there is sufficient storage within the impoundment to avoid
overtopping the dam during major storm events given outfall flow capabilities. This effort includes
evaluating the ability of the impoundment to safely accommodate the inflow design flood (IDF) according
to the appropriate IDF per the hazard potential classification of the impoundment (FEMA 2013b). To
make such a determination, analysis should conclude that impoundment decant structures and other water
conveyance features have not degraded over time. To accomplish this type of study, it may be helpful to
calculate surface water flow rates as part of an abandoned mine site water balance and to assess what the
estimated inflow to an impoundment may be. For additional information regarding threats of overtopping
an impoundment, see FEMA's Technical Manual: Overtopping Protection for Dams (FEMA 2015a). If
the tailings structure is categorized as a dam by the state, the structure may be required to safely pass the
probable maximum flood (PMF).
3.5 Estimate the Factors of Safety
The FOS is the ratio of the forces tending to resist the failure of a structure or slope compared with the
forces tending to cause a failure (as determined by accepted engineering practice). Federal agencies and
many states have developed minimum FOS requirements for earth and rock-fill dams. This document is
adopting USACE and FEMA FOS for use at abandoned mine impoundments and is based on USACE's
Engineering and Design: Slope Stability (USACE 2003) and FEMA's Federal Guidelines for Dam
Safety: Earthquake Analyses and Design of Dams (FEMA 2005). Impoundment FOS are the results of an
H&H evaluation and a slope stability analysis of the material present in the abandoned mine
impoundment.
9 In terms of environmental damage, knowledge of the geochemical characteristics of the tailings is important.
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3.5.1 Determine Slope Stability
A slope stability analysis is a two-dimensional limit equilibrium analysis (LEA) and is performed to
estimate the ratio of shear strength to the shear stress required for equilibrium. Slope stability analyses are
commonly conducted using computer-based geotechnical software using limit equilibrium methods.
Slope stability models are commonly used in conjunction with finite element seepage models to define
pore water conditions. Evaluation of the dam or impoundment construction method can also provide input
in the slope stability analysis if such information is available. The geotechnical software used to conduct
two-dimensional LEA typically requires the following model inputs:
Embankment construction method
Slope geometry
Soil shear strength
Pore pressure conditions
Soil properties
Loading conditions
3.5.2 Determine the Factors of Safety
Using data and inputs from the slope stability analysis and the H&H evaluation, the investigation team or
qualified contractor should determine three FOS for each impoundment: static, seismic, and liquefaction.
Static FOS. Static refers to the FOS under static loading conditions that can reasonably be
anticipated to occur during the lifetime of the tailings dam. Static loading conditions are those
that occur when a slope is in equilibrium, meaning that the load is at rest or is applied with
constant velocity (shear strength is a function of normal stress as governed by mass and gravity).
The calculated static FOS for earthen dams, such as tailings impoundments under the long-term,
maximum storage pool loading condition, should equal or exceed 1.50 (see Table 3-1 in
USACE 2003). The rapid drawdown loading condition typically does not apply to abandoned
waste impoundments unless active dewatering occurs because, to satisfy the conditions of the
loading condition, a release of the impoundment has likely already occurred with subsequent loss
of the reservoir and impounded material (USACE 2003).
Seismic FOS. Seismic refers to the FOS determined using analysis under earthquake conditions
for a seismic loading event, typically based on USGS seismic hazard maps1" for the area where
the abandoned mine impoundment is located. This seismic analysis is a pseudo-static analysis that
approximates a seismic event by applying an additional static load; it is used to predict whether
an impoundment would remain stable during an earthquake. While conducting seismic analyses,
it is important to consider the appropriate loading conditions, such as maximum storage pool
level and existing silt load. While pseudo-static analysis is considered appropriate for many
applications, dynamic seismic analysis or deformation modeling may be appropriate for high-risk
structures. In determining the appropriate peak ground acceleration (PGA), the maximum
credible earthquake (MCE), the maximum design earthquake (MDE), or safety evaluation
10 https://eartliquake.usgs.gov/liazards/liazmaps/
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earthquake (SEE), refer to FEMA's Federal Guidelines for Dam Safety Earthquake Analyses and
Design for Dams (FEMA 2005) and BORs "Design Standards No. 13. Embankment Dams:
Chapter 13: Seismic Analysis and Design' (BOR 2015b). For certain high-risk sites, more
stringent probabilistic intervals may be appropriate. The calculated pseudo-static seismic FOS
should equal or exceed 1.00 (FEMA 2005).
Liquefaction FOS. Liquefaction refers to the FOS determined using analysis under liquefaction
conditions. Liquefaction is a phenomenon that typically occurs in loose saturated or partially
saturated soils where the effective stress of the soils reduces to zero, corresponding to a total loss
of shear strength of the soil. The most common occurrence of liquefaction is in loose soils,
typically sands. The liquefaction FOS determination is used to determine if a dam would remain
stable if the soils of the embankment or its foundation were to experience liquefaction. The
calculated liquefaction FOS should equal or exceed 1.20 (FEMA 2005). If results indicate that the
FOS is greater than 1 but less than 1.2, it may be useful to conduct deformation modeling to
determine if deformation under the maximum design earthquake case is tolerable. The mining
industry often refers to this analysis as a post-seismic analysis.
There may be circumstances where analyses conclude that the tailings may not liquefy; however, this
conclusion does not necessarily mean that wastes will not flow upon failure. It may be useful to conduct
additional studies (using CPT or other methods) to determine if flow can occur even if the wastes may not
liquefy. ASDSO has developed online webinars to educate users on how to conduct static and seismic
stability studies.11
3.6 Assign a Condition Rating
After the FOS have been determined and a hazard potential classification is assigned, the investigation
team should assign a condition rating of the abandoned mine impoundment. Condition ratings are a
subjective rating based on the site visit findings, geotechnical investigation results, hazard potential
classification, FOS analysis, and professional judgment. Based on NID database definitions, condition
assessments include the following ratings (USACE 2016):
Satisfactory. No existing or potential safety deficiencies are recognized. Acceptable performance
is expected under all applicable loading conditions (static, seismic, and liquefaction) in
accordance with the applicable criteria. Minor maintenance items may be required.
Fair. Acceptable performance is expected under all required loading conditions (static, seismic,
and liquefaction) in accordance with the applicable safety regulatory criteria. Deficiencies may
exist that require additional action and secondary studies or investigations.
Poor. The impoundment has a safety deficiency for any required loading condition (static,
seismic, and liquefaction) in accordance with the applicable impoundment safety regulatory
criteria. Additional action is necessary.
Unsatisfactory. An impoundment safety deficiency considered unsafe is recognized that requires
immediate or emergency actions for problem resolution. Remedial project managers (RPM),
on-scene coordinators (OSC), or site managers should be immediately notified after a site visit if
11 https://leamiiigcenter.danisafety.org/on-demaiid-webinars
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impoundment conditions warrant corrective actions or when an impoundment is found to be rated
unsatisfactory or poor so that corrective actions can be taken in a timely manner. In addition,
short- or long-term corrective measures necessary to safeguard the structural stability of the
impoundment should be identified and the appropriate local and state officials notified.
3.7 Develop an Impoundment Structural Stability and Safety Report
Based on the results of the stability and safety analysis, the site investigation team and qualified
contractors should prepare an impoundment structural stability and safety report. The report contains
findings, conclusions, and recommendations derived from:
Document review;
Initial impoundment condition and failure assessment and site visit;
Instrumentation or monitoring results;
Geotechnical investigations and laboratory testing as applicable; and
Structural stability and safety analyses, including:
o Hazard potential classification;
o FOS estimation for static, seismic, and liquefaction conditions; and
o Condition rating.
The report typically will include a discussion of the following topics:
H&H capacity of the impoundment, including an evaluation of the surface water contributory
area and IDF.
Soil, groundwater, surface water, geology, geohydrology, and waste characteristics, including
data on site climate, geology, geotechnical, seismicity, hydrogeology, and hydrology accumulated
since the impoundment was constructed or last inspected.
Determination of the degree of dam face erosion as a primary concern during overtopping,
including analysis of surface cover, material properties, and depth and duration of overtopping.
A history of the performance of the impoundment through analysis of data from monitoring
instruments (if available) and review of available operating records.
Location of areas of potential downstream impact, such as schools, hospitals, or other critical
infrastructure within at least 5 miles downgradient of the impoundment.
Location with respect to federally designated flood plains.
Location of federal and tribal lands.
Conditions at the time of the impoundment assessment and recent precipitation.
Results and findings of the structural stability and safety analysis, including the data collected,
reviewed, and analyzed. Does the impoundment meet minimum FOS?
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Based on the impoundment investigation team's field observations and evaluation of other relevant data,
the report will contain findings and recommendations, including:
Overall determination of the hazard potential classification of each impoundment; and
Overall condition rating based on structural adequacy and stability of the impoundment structures
under all credible loading conditions through a review of static, seismic, and liquefaction FOS
and an assessment of the H&H capacity of the impoundments.
If an impoundment is found to meet or exceed recommended minimum FOS and there are no other
reasons to take any other actions to reduce risks associated with the impoundment, then it is appropriate to
proceed with the proposed CERCLA activity. A PE's signature and state-specific certification
engineering seal are typically required on the impoundment structural stability and safety report.
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4.0 MITIGATION MEASURES TAKEN PRIOR TO PROCEEDING WITH
THE PROPOSED ACTIVITY
When an impoundment's condition is rated as poor or unsatisfactory or the impoundment does not meet
the required minimum FOS, the impoundment structural stability and safety report should recommend
appropriate risk reduction measures. The timing of the mitigation will be a site-specific decision. Some
mitigation measures may be appropriate as part of the investigation phase to allow for the safe
implementation of the investigations. Many mitigation measures would be included in the alternatives
developed for the response action or require an independent response action (either removal or remedial)
depending upon whether the CERCLA threshold for action is triggered. If a determination is made that a
CERCLA action is not warranted, those responsible for the impoundment from an ownership and
regulatory oversight perspective, as well as local planning agencies, should be provided with the
completed stability assessment.
Should an action be recommended, there are a variety of risk reduction approaches, including buttressing,
adding height to the dam, compaction, use of alternative capacity, use of geotextiles, and reducing or
eliminating inflow. Before implementing any of these approaches, it is a best practice to subject them to a
risk analysis to ensure that they will not cause sudden releases. All these approaches will have
site-specific capital and operating costs that should be considered in planning a risk reduction measure.
This best practices document only mentions several common impoundment mitigation approaches, but
the correct approach is a site-specific determination. The BOR (2011) and the Montana Department of
Natural Resources and Conservation (MDNRC) and FEMA (2016) provide examples of mitigation
measures at impoundments.
One of the more rapid mitigation measures is dewatering an impoundment to reduce risks of excess
ponded water above the mine waste and to reduce the high moisture contents of the mine waste. The
BOR (2011) approach to dewatering standing water in an impoundment includes:
1. Pumping out impounded water (which may incur maintenance and treatment costs);
2. Constructing diversion ditches to prevent surface run-on; and
3. Using sprinklers or evaporators to spray impounded water into the air to speed evaporation
(where climatic conditions allow).
Dewatering may also include pore water management, such as installation or maintenance of wick drains
or passive horizontal drains. Dewatering may require treatment of the impoundment liquids based on
testing of those liquids. Reducing the water level in an abandoned tailings impoundment may cause a
rapid drawdown condition that can become a structural threat to the dam or impoundment slopes.
Structural failures may occur when the potentiometric surface of the impoundment pool is lowered at a
rate significantly higher than the excess pore water pressure within the impoundment walls can dissipate.
Other failure modes that may occur because of dewatering include internal dam erosion, significant dam
face erosion with the potential to expose weak material, and saturation of foundation material.
An engineering evaluation should be conducted to identify a safe drawdown rate. Factors to consider
include climatic conditions, the structural stability of the impoundment, and the receiving water flow and
chemistry. Caution should be exercised during dewatering efforts to reduce impacts to the integrity of the
impoundment and to decrease the risk of failure. A FMEA should be performed on selected dewatering
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approaches before implementation to identify any risks of mine waste release that might occur during
dewatering efforts (BOR 2011; USACE 2004).
Another common mitigation method is to construct diversion ditches around the perimeter of a surface
impoundment to intercept and manage surface run-on and, thus, reduce water infiltration reporting into
the impoundment. USACE, BOR, and state regulations should be reviewed to determine if specific design
standards have been issued for these types of diversions. Diversion construction near spillways may also
include a PMF and precipitation analysis. For example, MSHA guidelines require that diversion ditches
have an appropriate configuration and elevation around the impoundment, which is determined on a
case-by-case basis. MSHA guidelines also dictate that the channels provide flow capacity for a 100-year,
24-hour storm event and include long-term protection against erosion and deterioration (BOR 2011;
MSHA 2009; USACE 2004).
An additional mitigation method is buttressing or reinforcing. Reinforcement may include installing toe
drains, improving or adding spillways, and regrading slopes. Buttressing uses rock armoring or a
compacted earth buttress of slopes as an additional form of slope protection that has been relied on
extensively in dam safety.
Consideration of the use of geosynthetic (geotextiles, geogrids, geonets, geomembranes, and
geocomposites) and other materials for embankment reinforcement should also be considered although
the limited understanding of their long-term performance should be recognized.
In some situations, a combination of these risk reduction measures could be useful, such as reinforcement
with partial or full dewatering.
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5.0 BIBLIOGRAPHY
Anderson, N., and A. Ismail. 2016. "A Generalized Protocol for Selecting Appropriate Geophysical
Techniques." Federal Highways Administration, Interstate Technical Group on Abandoned
Underground Mines - An Interactive Forum. University of Missouri-Rolla. Accessed February.
https://www.fhwa.dot.gov/engineering/geotech/hazards/mine/workshops/ktwkshp/ky0307.cfm.
American Society for Testing and Materials (ASTM) International. 2006. Standard Guide for Selection of
Drilling Methods for Environmental Site Characterization. ASTM D6286-98. West
Conshohocken, Pennsylvania. https://www.astm.org/Standards/D6286.htm.
ASTM. 2007. Standard Test Method for Particle-Size Analysis of Soils. ASTM D422.
http: //www. astm.org/Standards/D422.
ASTM. 2008. Standard Practice for Using Hollow-Stem Augers for Geotechnical Exploration and Soil
Sampling. ASTM D6151-08. West Conshohocken, Pennsylvania.
http://www.astm.org/Standards/D6151 .htm.
ASTM. 2010a. Standard Practice for Sonic Drilling for Site Characterization and the Installation of
Subsurface Monitoring Devices. ASTM D6914-04. West Conshohocken, Pennsylvania,
http: //www. astm. org/Standards/D 6914. htm.
ASTM. 2010b. Standard Test Methods for Laboratory Determination of Water (Moisture) Content of Soil
and Rock by Mass. ASTM D2216. West Conshohocken, Pennsylvania,
http: //www .astm ,org/Standards/D2216 .htm.
ASTM. 201 la. Standard Test Method for Direct Shear Test of Soils Under Consolidated Drained
Conditions. ASTM D3080. West Conshohocken, Pennsylvania,
http: //www. astm ,org/Standards/D3 080 .htm.
ASTM. 201 lb. Standard Practice for Determining the Normalized Penetration Resistance of Sands for
Evaluation of Liquefaction Potential. ASTM D6066-11. West Conshohocken, Pennsylvania,
https ://www.astm ,org/Standards/D6066 .htm.
ASTM. 2012a. Standard Test Method for Electronic Friction Cone and Piezocone Penetration Testing of
Soils. ASTM D5778-12. West Conshohocken, Pennsylvania,
https: //www .astm ,org/Standards/D5 778 .htm.
ASTM. 2012b. Standard Guide for Use of Direct Rotary Drilling with Water-Based Drilling Fluid for
Geoenvironmental Exploration and the Installation of Subsurface Water-Quality Monitoring
Devices. ASTM D5783-95(2012). West Conshohocken, Pennsylvania,
https: //www .astm ,org/Standards/D5 783 .htm.
ASTM. 2012c. Standard Guide for Use of Direct Rotary Wireline Casing Advancement Drilling Methods
for Geoenvironmental Exploration and Installation of Subsurface Water-Quality Monitoring
Devices. ASTM D5876-95(2012). West Conshohocken, Pennsylvania,
https: //www .astm .org/Standards/D5 876 .htm.
Best Practices to Prevent Releases from Impoundments at Abandoned Mine Sites
while Conducting CERCLA Response Actions
35
-------
ASTM. 2012d. Standard Guide for Use of Direct Air-Rotary Drilling for Geoenvironmental Exploration
and the Installation of Subsurface Water-Quality Monitoring Devices. D5782-95(2012). West
Conshohocken, Pennsylvania. http://www.astm.org/Standards/D5782.htm.
ASTM. 2013a. Standard Guide for Use of Cable-Tool Drilling and Sampling Methods for
Geoenvironmental Exploration and Installation of Subsurface Water- Quality Monitoring
Devices. D5875M-13. West Conshohocken, Pennsylvania,
http: //www .astm ,org/Standards/D5 875 .htm.
ASTM. 2013b. Standard Guide for Use of Dual-Wall Reverse-Circulation Drilling for Geoenvironmental
Exploration and the Installation of Subsurface Water- Quality Monitoring Devices. ASTM
D5781/D5781M-13. West Conshohocken, Pennsylvania.
http://www.astm.org/Standards/D5781 .htm.
ASTM. 2013c. Standard Guide for Use of Casing Advancement Drilling Methods for Geoenvironmental
Exploration and Installation of Subsurface Water- Quality Monitoring Devices. ASTM
D5872/D5872M-13. West Conshohocken, Pennsylvania,
http: //www .astm ,org/Standards/D5 872 .htm.
ASTM. 2014. Standard Practice for Rock Core Drilling and Sampling of Rock for Site Exploration.
ASTM D2113. West Conshohocken, Pennsylvania. https://www.astm.org/Standards/D2113.htm.
ASTM. 2015. Standard Guide for Direct Push Soil Sampling for Environmental Site Characterizations.
ASTM D6282M. West Conshohocken, Pennsylvania.
http://www.astm.org/Standards/D6282.htm.
ASTM. 2016a. New Test Method for Pocket Penetrometer Test - Under Development. ASTM WK27337.
West Conshohocken, Pennsylvania.
http://www.astm org/DATABASE. CART/WORKITEMSAVK273 3 7 .htm.
ASTM. 2016b. Standard Test Methods for Laboratory Miniature Vane Shear Test for Saturated
Fine-Grained Clayey Soil. ASTM D4648/D4648M-16. West Conshohocken, Pennsylvania,
https: //www .astm ,org/Standards/D4648 .htm.
ASTM. 2016c. Standard Test Method for Mechanical Cone Penetration Testing of Soils. ASTM
D3441-16. West Conshohocken, Pennsylvania. http://www.astm.org/Standards/D3441.htm.
Association of State Dam Safety Officials (ASDSO). 2005. Owner-Responsible Periodic Inspection
Guidance. December.
ASDSO. 2007. Developing Emergency Action Plans Using the NRCS Sample EAP "Tillable Form"
Template. September.
https://damsafety.org/sites/default/files/EAPWG%20Final%20EAP%20Template%20Fact%20Sh
eet_0.pdf.
ASDSO. 2016a. "Module: Inspection of Embankment Dams." Training Aids for Dam Safety,
https: //www .hsdl .org/?view&did=759056.
ASDSO. 2016b. "Module: Evaluation of Hydraulic Adequacy." Training Aids for Dam Safety.
http://damfailures.org/wp-content/uploads/2015/06/Evaluation-of-Hydraulic-Adequacy.pdf.
Best Practices to Prevent Releases from Impoundments at Abandoned Mine Sites
while Conducting CERCLA Response Actions
36
-------
ASDSO. 2016c. "Module: Documenting and Reporting Findings from a Dam Safety Inspection."
Training Aids for Dam Safety, https://www.hsdl.org/?view&did=759064.
Aubertin, J.M., and B. Bussiere. 2013. "On the Use ofWaste Rock Inclusions to Improve the
Performance of Tailings Impoundments/' Proceedings of the 18th International Conference on
Soil Mechanics and Geotechnical Engineering.
http://www.cfms-sols.org/sites/default/files/Actes/735-738.pdf.
Barrera, S. 2005. "Aspects to be Considered in Dynamic Stability Analysis.'' Proceedings of the 8th
International Seminar on Paste and Thickened Tailings. April.
Barrick Australia Limited. 2013. Final Hydrogeological Assessment, Cowal Gold Mine, Extension
Modification. September.
http://evolutionmining.com.au/wp-content/uploads/2015/08/Appendix-A-Hydrogeological-
Assessment.pdf.
Bureau of Reclamation (BOR). 1990. Earth Manual, Part II. Third Edition. Denver, Colorado: Bureau of
Reclamation.
BOR. 1995. Safety Evaluation of Existing Dams Manual. Denver, Colorado: Bureau of Reclamation.
BOR. 1998. Earth Manual, Part I. Third Edition. Denver, Colorado: Bureau of Reclamation.
https://www.usbr.gov/tsc/techreferences/mands/mands-pdfs/earth.pdf.
BOR. 1999. "Standard Penetration Test: Drillers/Operators Guide." Report Number DSO- 98-17. Denver,
Colorado: Bureau of Reclamation.
BOR. 2008. "Leadville Mine Drainage Tunnel Risk Assessment: Leadville Mine and Drainage Tunnel
Project, Colorado, Great Plains Region."
https://www.usbr.gov/gp/ecao/leadville/combined_risk_assessment.pdf.
BOR. 2010. Guidelines for Drilling and Sampling in Embankment Dams. Denver, Colorado: Bureau of
Reclamation.
BOR. 2011. "Dam Safety Public Protection Guidelines: A Risk Framework to Support Dam Safety
Decision-Making." Interim. Denver, Colorado: Bureau of Reclamation. August.
https://www.usbr.gov/ssle/damsafety/documents/PPG201108.pdf.
BOR. 2012. "Design Standards No. 13. Embankment Dams: Chapter 12: Foundation and Earth Materials
Investigation. Phase 4 (Final)." Reclamation, Managing Water in the West. July.
https://www.usbr.gov/tsc/techreferences/designstandards-datacollectionguides/finalds-pdfs/DS13-
12.pdf.
BOR. 2015a. "RCEM - Reclamation Consequences Estimating Methodology: Dam Failure and Flood
Event Case History Compilation." Interim. Reclamation, Managing Water in the West.
https://www.usbr.gov/ssle/damsafety/documents/RCEM-CaseHistories2015.pdf.
Best Practices to Prevent Releases from Impoundments at Abandoned Mine Sites
while Conducting CERCLA Response Actions
37
-------
BOR. 2015b. "Design Standards No. 13. Embankment Dams. Chapter 13: Seismic Analysis and Design."
Phase 4 (Final). Reclamation, Managing Water in the West. May.
https://www.usbr.gov/tsc/techreferences/designstandards-datacollectionguides/finalds-pdfs/DS13-
13.pdf.
BOR and U.S Army Corps of Engineers (USACE). 2015. "Best Practices in Dam and Levee Safety Risk
Analysis." Version 4.0. July.
https://www.usbr.gov/ssle/damsafety/risk/BestPractices/Chapters/l-BestPracticesCover.pdf.
Caldwell, J.A., and A. Robertson. 1986. "Geotechnical Stability Considerations in the Design and
Reclamation of Tailings Impoundments/' International Symposium on Geotechnical Stability in
Surface Mining. Calgary. November.
https://www.rgc.ca/files/publications/caldwelll986eremedialactivitiesaridareas.pdf.
California Environmental Protection Agency, Department of Toxic Substances Control. 1998. Abandoned
Mine Lands Preliminary Assessment Handbook. January.
https://semspub.epa.gov/work/01/28632.pdf.
Chambers, D.M., and B. Higman. 2011. "Long Term Risks of Tailings Dam Failure.'' October,
http ://ofmpub .epa.gov/eims/eimscomm .getfile ?p_download_id=513583.
Colorado Division of Mineral and Geology. 2002. Best Practices in Abandoned Mine Land Reclamation.
http://cusp.ws/wp-content/uploads/2014/05/CO_DMG_BMPs_AML_Reclamation.pdf.
Colorado Division of Reclamation Mining. 2004. "Summary of Minutes, Mined Land Reclamation Board
Meeting." November.
Conservation Authorities Geoscience Group. 2013. "Hydrogeological Assessment Submissions,
Conservation Authority Guidelines to Support Development Applications." June.
https://www.lsrca.on.ca/Shared%20Documents/permits/hydrogeological%20_guidelines.pdf7pdf
=Hydrogeological-Guide lines.
Danihelka, P. 2008. "Safety Guidelines and Good Practices for Tailings Management Facilities."
Conference of the Parties to the Convention on the Transboundary Accidents, UNECE, Geneva.
November.
www.unece.org/fileadmin/DAM/env/teia/VCoP/Presentations/13SAFETY_GUIDANCE_TAILI
NG_DAMS_Geneva_2008 .pdf.
Davies, M.P. 2002. "Tailings Impoundment Failures: Are Geotechnical Engineers Listening?" Waste
GEO Technics. September. http://www.pebblescience.org/pdfs/Dam_failuresDavies2002.pdf.
EPA Victoria, Australia. 2006. "Environmental Auditing, Hydrogeological Assessment (Groundwater
Quality) Guidelines." September.
https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&ved=2ahUKEwjD08Gl
oKXsAhUQgp4KHZORBiUQFjACegQIARAC&url=https%3A%2F%2Fwww.epa.vic.gov.au%2
F-
%2Fmedia%2Fepa%2Ffiles%2Fpublications%2F668.pdf&usg=AOvVawOwRZ7FOLaUkdDfOxi
KRIti.
Best Practices to Prevent Releases from Impoundments at Abandoned Mine Sites
while Conducting CERCLA Response Actions
38
-------
Federal Emergency Management Agency (FEMA). 2004. "Federal Guidelines for Dam Safety: Hazard
Potential Classification System for Dams". April.
www.fema.gov/media-library-data/20130726-1516-20490-795 l/fema-333.pdf.
FEMA. 2005. "Federal Guidelines for Dam Safety: Earthquake Analyses and Design of Dams." May.
https://www.resolutionmineeis.us/sites/default/files/references/fema-dam-safety-earthquake-
analyses-2005 .pdf.
FEMA. 2006. "Catalog of FEMA Dam Safety Resources." August.
https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&ved=2ahUKEwjlw-
PLoaXsAhWT9Z4KHYleAgQQFjAAegQIAhAC&url=https%3A%2F%2Fwww.hsdl.org%2F%
3Fview%26did%3D16411&usg=AOvVaw2b5b6WF9C-g_nAxl535ar2.
FEMA. 2013a. "Federal Guidelines for Dam Safety: Emergency Action Planning for Dams." FEMA 64.
July.
www.fema.gov/media-library-
data/5b20db599c212f77fd5e85d256f471a3/EAP+Federal+Guidelines_FEMA+P-64.pdf.
FEMA. 2013b. "Selecting and Accommodating Inflow Design Floods for Dams." FEMA P-94. August,
https: //www .hsdl .org/?view&did=757389.
FEMA. 2015a. "Technical Manual: Overtopping Protection for Dams." FEMA P-1015. May.
http://damfailures.org/wp-content/uploads/2015/06/Technical-Manual_Overtopping-Protection-
for-Dams.pdf.
FEMA. 2015b. "Evaluation and Monitoring of Seepage and Internal Erosion. Interagency Committee on
Dam Safety (ICODS)." FEMA P-1032. May.
https://damsafety.org/sites/default/files/files/FEMA%20TM%20EvalMonitorSeepageInternalEros
n%20P 1032-2015.pdf.
Federal Energy Regulatory Commission (FERC). 2016a. "Guidelines for Drilling in and near
Embankment Dams and Their Foundations." Division of Dam Safety and Inspections.
Version 3.1. June, https://www.ferc.gov/sites/default/files/2020-04/guidelines.pdf.
FERC. 2016b. "Risk Informed Decision Making (RIDM): Risk Guidelines for Dam Safety." Version 4.1.
https://www.ferc.gov/sites/default/files/2020-04/Risk-Guidelines-for-Dam-Safety.pdf.
Federal Highways Administration (FHWA). 2002. "Subsurface Investigations: Geotechnical Site
Characterization." FHWA-NHI-01-031. May.
https://www.fhwa.dot.gov/engineering/geotech/pubs/012546.pdf.
FHWA. 2016. "Abandoned Underground Mines Program." Bridges and Structures: Geotechnical
Hazards. Accessed January, www.fhwa.dot.gov/engineering/geotech/hazards/mine/.
Government of British Columbia (GBC). 2015a. "Report on Mount Polley Tailings Storage Facility
Breach." January.
https://www.mountpolleyreviewpanel.ca/sites/default/files/report/ReportonMountPolleyTailingsS
torageFacilityBreach.pdf.
Best Practices to Prevent Releases from Impoundments at Abandoned Mine Sites
while Conducting CERCLA Response Actions
39
-------
GBC. 2015b. "Report on Mount Polley Tailings Storage Facility Breach, Appendix B: Supporting
Information/' January.
https://www.mountpolleyreviewpanel.ca/sites/default/files/report/AppendixB_SupportingInforma
tion.pdf.
GBC. 2015c. "Report on Mount Polley Tailings Storage Facility Breach, Appendix G: Water Balance.
January."'
https://www.mountpolleyreviewpanel.ca/sites/default/files/report/AppendixG_WaterBalance.pdf.
GBC. 2015d. "Report on Mount Polley Tailings Storage Facility Breach, Appendix H: Breach Analysis.
January."
https://www.mountpolleyreviewpanel.ca/ sites/default/files/report/AppendixH_BreachAnalysis .pd
f.
GBC. 2015e. "Report on Mount Polley Tailings Storage Facility Breach, Appendix I: B.C. Tailings Dam
Failure Frequency and Portfolio Risk." January.
https://www.mountpolleyreviewpanel.ca/sites/default/files/report/AppendixI_BCTDFFrequencya
ndPortfolioRisk.pdf.
Government of Western Australia, Department of Minerals and Energy. 1999. "Guidelines on the Safe
Design and Operating Standards for Tailings Storage." May.
Hammack, R., J. Sams, G. Veloski, and T. Ackman. 2007. "Airborne Surveys Identify Environmental
Problems on Mined Lands." U.S. Department of Energy, National Energy Technology
Laboratory.
Hydrometrics, Inc. 2010. "Data Compilation Report for the Black Pine Mine, Granite County, Montana."
International Council of Mining and Metals (ICMM). Undated. "A Practical Guide to Catchment-Based
Water Management for the Mining and Metals Industry."
https://www.icmm.com/website/publications/pdfs/water/practical-guide-catchment-based-water-
management_en.
ICMM. 2008. "Planning for Integrated Mine Closure: Toolkit."
https://extractiveshub.org/servefile/getFile/id/972.
International Network for Acid Prevention. 2009. "Global Acid Rock Drainage Guide (GARD Guide)."
www.gardguide .com.
Jamiolkowski, M., W.D. Carrier, R.J. Chandler, K. Hoeg, W. Swierczynski, and W. Wolski. 2010. "First
Za Chieh-Moh Distinguished Lecture: The Geotechnical Problems of the Second Largest Copper
Tailings Pond at Zelazny Most, Poland." Geotechnical Engineering Journal of the SEAGS &
AGSSEA. Volume 41, Number 1. March.
Kaplan, S., and others. 1999. New Tools for Failure and Risk Analysis: Anticipatory Failure
Determination (AFD) and the Theory of Scenario Structuring. Osaka, Japan: Idea
International, Inc.
Best Practices to Prevent Releases from Impoundments at Abandoned Mine Sites
while Conducting CERCLA Response Actions
40
-------
Mayes, W.M., and A.P. Jarvis. 2012. "Prioritisation of Abandoned Non-Coal Mine Impacts on the
Environment." Bristol, United Kingdom: Environment Agency.
https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/290872/schol 11 lb
uvi-e-e.pdf.
Michael, P., and L. Chavel. 2008. "Environmental Risks Associated with Coal Refuse Impoundment
Reclamation."
https://www.arcc.osmre.gov/resources/docs/2008-PMichael-
EnvironRisksCoalRefuseImpoundment.pdf.
Michael, P.R., M.W. Richmond, S.J. Self, J.M. Shapaka, and J.F. Mack. 2015. "Preventing Coal Waste
Impoundment Breakthroughs into Underground Mines: How Well Area We Doing?" SME
Annual Meeting. February.
https://www.arcc.osmre.gov/resources/docs/2015-
PMichaelSMEPreventingCoalWasteImpoundmentBreakthroughs.pdf.
Mine Safety and Health Administration (MSHA). 2009. "Engineering and Design Manual: Coal Refuse
Disposal Facilities." May.
https ://arlweb .msha.gov/Impoundments/DesignManual/2009ImpoundmentDesignManual .pdf.
Mining & Energy Technical Services Pty, Ltd. 2012. "Appendix E-l: Tailings Storage Facility
Management Plan - McArthur River Mine Phase 3 Development Project." January.
https://ntepa.nt.gov.au/ data/assets/pdf_file/0011/287777/Appendix-El-Tailings-Storage-
Facility-TSF-Management-Plan.pdf.
Mining Association of Canada (MAC). 2011. Developing an Operation, Maintenance, and Surveillance
Manual for Tailing and Water Management Facilities.
MAC. 2019. A Guide to the Management of Tailings Facilities. Version 3.1. March 18.
https://mining.ca/our-focus/tailings-management/tailings-guide/.
Montana Department of Natural Resources and Conservation (MDNRC) and FEMA. 2016. "Dam Owner
Emergency Intervention Toolbox." Prepared by Gannett Fleming, Inc. July.
http://dnrc.mt.gov/divisions/water/operations/dam-safety/cool-tools-for-dam-
safety/MDNRCDam OwnerEmergencyInterventionToolbox_Final.pdf.
Neves Correia dos Santos, R., L.M. Mello Saraiva Caldeira, and J.P. Bilee Serra. 2011. "FMEA of a
Tailings Dam." Georisk. Assessment and Management of Risk for Engineered Systems and
Geohazards. DOI: 10.1080/17499518.2011.615751.
http://dx.doi.org/10.1080/17499518.2011.615751.
Nobis Engineering, Inc. 2009. "Conceptual Site Model - Technical Memorandum, Ely Copper Mine
Superfund Site, Vershire, Vermont." July.
Office of Surface Mining, Reclamation, and Enforcement (OSMRE). 2016a. "National Mine Map
Repository." Accessed January. http://mmr.osmre.gov/MultiPub.aspx.
OSMRE. 2016b. "Hydrology Equipment." Accessed January.
www.arcc.osmre.gov/about/techDisciplines/hydrology/equipment.shtm.
Best Practices to Prevent Releases from Impoundments at Abandoned Mine Sites
while Conducting CERCLA Response Actions
41
-------
OSMRE. 2016c. "National and Regional Technology Transfer Teams." Accessed January,
www.osmre .gov/programs/tdt/teams. shtm.
Pennsylvania Department of Environmental Protection. 1998. "Coal Mine Drainage Prediction and
Pollution Prevention in Pennsylvania."
http://files.dep.state.pa.us/Mining/BureauOfMiningPrograms/BMPPortalFiles/Coal_Mine_Draina
ge_Prediction_and_Pollution_Prevention_in_Pennsylvania.pdf.
Rademeyer, B. 2007. "The Influence of Environmental Impacts on Tailings Impoundment Design." July.
http://repository.up.ac.za/bitstream/handle/2263/25815/00front.pdf?sequence=l.
Renken, K, D.M. Mchania, and E.F. Yanful. 2005. "Geosynthetics Research and Applications in the
Mining and Mineral Processing Environment." Proceedings of the North American Geosynthetics
Society (NAGS) Geosynthetic Institute (GSI), Las Vegas, Nevada. December 14-16.
https://www.geosynthetica.com/Uploads/RenkenMchainaYanful.pdf.
Richmond, T. 1991. "A History of Mineral Concentration: A History of Tailings." Proceedings American
Society of Mining and Reclamation. Pages 369 through 388.
http://www.asmr.us/Portals/0/Documents/Conference-Proceedings/1991/0369-Richmond.pdf.
Robertson GeoConsultants Inc. and BGC Engineering Inc. 2006. "Geotechnical Risk Assessment for
Galore Creek (FMEA)." Report No. 097003. March.
Robertson, P.K. 2013. "The James K. Mitchel Lecture: Interpretation of In-Situ Tests - Some Insights."
Geotechnical and Geophysical Site Characterization 4.
Soderberg, R.L., and R.A. Busch. 1977. "Design Guide for Metal and Nonmetal Tailings Disposal."
United States Department of the Interior, Bureau of Mines.
http://babel.hathitrust.org/cgi/pt?id=mdp.39015078453738;view=lup;seq=3.
SRA International, Inc. 2009. "Mine Tailings and Coal Impoundments: Strengthening Security,
Emergency Preparedness and Response." October.
Strachan, C., and J. Caldwell. 2010. "New Directions in Tailings Management." Edited by the Organizing
Committee of the 14th International Conference on Tailings and Mine Waste.
Taggart, A. 1944. Handbook of Mineral Dressing: Ores and Industrial Minerals. New York: John Wiley
and Sons.
Tetra Tech, Inc. 2015. "Attachment C: Contingency, Notifications, and Emergency Action Planning."
Draft Final. Version 5.
United Nations Educational, Scientific and Cultural Organization (UNESCO). 1982. "Ground-Water
Models." http://unesdoc.unesco.org/images/0004/000489/048909eo.pdf.
United Nations Environment Programme (UNEP). 2001. "Tailings Dams. Risk of Dangerous
Occurrences." Bulletin 121. http://www.unep.fr/shared/publications/pdf/2891-TailingsDams.pdf.
Best Practices to Prevent Releases from Impoundments at Abandoned Mine Sites
while Conducting CERCLA Response Actions
42
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UNEP. 2017. Mine Tailings Storage: Safety Is No Accident. A Rapid Response Assessment. Edited by C.
Roche, K. Thygesen, and E. Baker. ISBN: 978-82-7701-170-7.
https://www.grida.n0/publications/3 83.
UNEP and ICMM. 2005. "Good Practice in Emergency Preparedness and Response." September.
https://www.icmm.com/en-gb/publications/health-and-safety/good-practice-in-emergency-
preparedness-and-response.
URS Corporation. 2007. "Red Dog Mine Closure and Reclamation Plan: SD C6: Seepage Analysis
Report, Red Dog Tailings Main Dam, Future Raises to Closure." February.
http://dnr.alaska.gov/mlw/mining/largemine/reddog/publicnotice/pdf/sdc6.pdf.
U.S. Army Corps of Engineers (USACE). 1995. "Engineering and Design: Gravity Dam Design."
EM 1110-2-2200. June 30.
https://www.publications.usace.army.mil/Portals/76/Publications/EngineerManuals/EM_1110-2-
2200.pdf.
USACE. 2001. "Geotechnical Investigations." EM-1110-1-1804. January 1.
http://www.publications.usace.army.mil/Portals/76/Publications/EngineerManuals/EM_1110-l-
1804.pdf.
USACE. 2002. "Engineering and Design: Structural Deformation Surveying." EM 1110-2-1009. June 1.
www.publications.usace.army.mil/Portals/76/Publications/EngineerManuals/EM_1110-2-
1009.pdf.
USACE. 2003. "Engineering and Design: Slope Stability." EM 1110-1-1902. October 31.
www.publications.usace.army.mil/Portals/76/Publications/EngineerManuals/EM_1110-2-
1902.pdf.
USACE. 2004. "Engineering and Design: General Design and Construction Considerations for Earth and
Rock-Fill Dams." EM 1110-2-2300. July 30.
www.publications.usace.army.mil/Portals/76/Publications/EngineerManuals/EM_1110-2-
2300.pdf.
USACE. 2005. "Stability Analysis of Concrete Structures." EM 1110-2-2100. December.
https://www.publications.usace.army.mil/portals/76/publications/engineermanuals/em_1110-2-
2100.pdf.
USACE. 2007. "Earthquake Design and Evaluation of Concrete Hydraulic Structures." EM 1110-2-6053.
May 1.
https://www.publications.usace.army.mil/Portals/76/Publications/EngineerManuals/EM_1110-2-
6053.pdf.
USACE. 2012. "Environmental Quality: Conceptual Site Models." EM 200-1-12. December 28.
https://fdocuments.us/document/em-200-l-12.html.
USACE. 2014a. "Recommended Guidelines for Safety Inspections of Dams." ER 1110-2-106.
Best Practices to Prevent Releases from Impoundments at Abandoned Mine Sites
while Conducting CERCLA Response Actions
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USACE. 2014b. "Engineering and Design: Safety of Dams - Policy and Procedures." ER 1110-2-1156.
March 31.
www.publications.usace.army.mil/Portals/76/Publications/EngineerRegulations/ER_1110-2-
1156.pdf.
USACE. 2014c. "Drilling in Earth Embankment Dams and Levees." ER-1110-1-1807. December 31.
http: //www .publications .usace. army .mil/Portals/7 6/Publications/EngineerRegulations/ER_ 1110-
l-1807.pdf.
USACE. 2016. "CorpsMap: National Inventory of Dams." Accessed February, http://nid.usace.army.mil/.
U.S. Department of Homeland Security (DHS). 2015. Dams Sector Crisis Management Handbook.
Developed jointly by Dams Sector Specific Agency, Dams Sector Coordinating Council, Dams
Sector Government Coordinating Council, Critical Infrastructure Partnership Advisory Council.
https://www.cisa.gov/sites/default/files/publications/dams-crisis-management-handbook-2015-
508.pdf.
U.S. Environmental Protection Agency (EPA). 1988. "Guidance for Conducting Remedial Investigations
and Feasibility Studies under CERCLA.' October,
https ://rais. ornl .gov/documents/GUID ANCE. PDF.
EPA. 1993. "Subsurface Characterization and Monitoring Techniques: Desk Reference Guide, Volume 1:
Solids and Ground Water Appendices A and B.' May.
https://nepis.epa.gov/Exe/ZyPDF.cgi/30004L8E.PDF?Dockey=30004L8E.PDF.
EPA. 2000. "Abandoned Mine Site Characterization and Cleanup Handbook." August.
https://www.epa.gov/sites/production/files/2015-09/documents/2000_08_pdfs_amscch.pdf.
EPA. 2001. "Performing Quality Flow Measurements at Mine Sites." September,
www.earthwardconsulting.com/library/600r01043complete.pdf.
EPA. 2003. "EPA and Hard Rock Mining: A Source Book for Industry in the Northwest and Alaska."
January. https://nepis.epa.gov/Exe/ZyPDF.cgi/P1004J4W.PDF?Dockey=P 1004J4W.PDF.
EPA. 2005. "Groundwater Sampling and Monitoring with Direct Push Technologies." August.
https://nepis.epa.gov/Exe/ZyPDF.cgi/20017GL0.PDF?Dockey=20017GL0.PDF.
EPA. 2006. "Guidance on Systematic Planning Using the Data Quality Objectives Process." February.
www.epa.gov/sites/production/files/documents/guidance_systematic_planning_dqo_process.pdf.
EPA. 2008. "Interim Record of Decision, Lava Cap Mine Superfund Site Groundwater Operable Unit
(OU2), Nevada County, California." September, https://semspub.epa.gov/work/09/1146780.pdf.
EPA. 2011. "Environmental Cleanup Best Management Practices: Effective Use of the Project Life Cycle
Conceptual Site Model." Quick Reference Fact Sheet. Office of Superfund Remediation and
Technology Innovation. July.
www.clu-in.org/download/remed/csm-life-cycle-fact-sheet-final.pdf.
EPA. 2012. "Formosa Mine Superfund Site: Final OU1 Remedial Investigation Report."
https://semspub.epa.gov/work/10/651451 .pdf.
Best Practices to Prevent Releases from Impoundments at Abandoned Mine Sites
while Conducting CERCLA Response Actions
44
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EPA. 2014. "Reference Guide to Treatment Technologies for Mining-Influenced Water." EPA 542-R-14-
001. March,
www.clu-
in.org/download/issues/mining/Reference_Guide_to_Treatment_Technologies_for_MIW.pdf.
EPA. 2015a. "Red and Bonita/Gold King Operational Plan." Draft. May 22.
www.epa.gov/sites/production/files/2015-10/documents/15 73 798 .pdf.
EPA. 2015b. "Memorandum: Transmittal of EPA Internal Gold King Mine Review Report." August 24.
www.epa.gov/sites/production/files/2015-
08/documcnts/nc\\gold_king_m inc_mcmodatcd_rcdactcd.pdf.
EPA. 2015c. "Memorandum: Interim Guidance for Continuation of Work and Development of
Comprehensive List of Superfund Mining and Mineral Processing Sites". September 4.
www.epa.gov/sites/production/files/2015-
09/documents/interimguidanceforworkatminesites_9_4_l 5 .pdf.
EPA. 2015d. "Memorandum: Review of Regional and Area Contingency Plans for Downstream
Notifications." September 4.
www.epa.gov/sites/production/files/2015-
09/documents/reviewofdownstreamnotificationplans9_4_2015 .pdf.
EPA. 2015e. "Post-Gold King Mine Release Incident: Conceptual Monitoring Plan for Surface Water,
Sediments, and Biology." Draft. September.
www.epa.gov/sites/production/files/2015-09/documents/post-
gkm_draft_conceptual_monitoring_plan_9_l 7_2015 .pdf.
EPA. 2015f. "Technical Memorandum: Focused Technical Review of Probe Hole Dewatering
Characterization Plan and 30-60 Percent Draft Design Plans for Level 1 Adit Rehabilitation,
Standard Mine, Gunnison National Forest, Colorado." October.
EPA. 2016a. "Coal Combustion Residuals Impoundment Assessment Reports." Accessed January.
https://www.epa.gov/sites/production/files/2016-
06/documents/ccr_impoundmnt_asesmnt_rprts.pdf.
EPA. 2016b. "Guideline Template for Hydrogeological Review/Technical Assessment Report." Accessed
January.
http://www.epa.ie/pubs/reports/enforcement/templates/Guideline%20Template%20Report%20for
%20reporting%20compliance%20with%20the%20EO%20(Groundwater)%20Regulations%2020
10.pdf.
EPA. 2016c. "Field Sampling Procedures for Region 9." Accessed January.
www.epa.gov/quality/field-sampling-procedures-region-9.
U.S. Geological Survey (USGS). 201 la. "Review and Interpretation of Previous Work and New Data on
the Hydrogeology of the Schwartzwalder Uranium Mine and Vicinity, Jefferson County,
Colorado." U.S. Geological Survey Open-File Report 2011-1092.
http://pubs.usgs.gov/of/2011/1092/pdf/OFl l-1092.pdf.
Best Practices to Prevent Releases from Impoundments at Abandoned Mine Sites
while Conducting CERCLA Response Actions
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USGS. 201 lb. Water Budgets and Groundwater Volumes for Abandoned Underground Mines in the
Western Middle Anthracite Coalfield, Schuylkill, Columbia, and Northumberland Counties,
Pennsylvania Preliminary Estimates with Identification of Data Needs: U.S. Geological Survey
Scientific Investigations Report 2010-5261.
http://pubs.usgs.gov/sir/2010/526 l/support/sir2010-5261 .pdf.
USGS. 2016b. "Bibliography of Geophysical Methods for Characterizing Mine Waste." Accessed
January, http://crustal.usgs.gov/projects/minewaste/geophysics_mine_pubs.html.
USGS. 2016c. "Geophysical Technology Transfer (G2T)." Accessed January.
http://water.usgs.gov/ogw/bgas/g2t.html.
U.S. Society on Dams (USSD). 2015. "Managing Risk and Uncertainty: Ensuring a Sustainable Future
for Dams, Levees, and Reservoirs." 35th Annual USSD Conference. April.
https://www.ussdams.org/wp-content/uploads/2016/05/Abstracts_2015 .pdf.
Wildemeersrch, S., S. Brouyere, P. Orban, J. Couturier, C. Dingelstadt, and A. Dassargues. 2010.
"Application of the Hybrid Finite Element Mixing Cell Method to an Abandoned Coalfield in
Belgium." Journal of Hydrology. Volume 392, Issues 3-4.
http://orbi.ulg.ac.be/bitstream/2268/69485Zl/HYDROL9216_Accepted_Manuscript.pdf.
World Information Service on Energy (WISE). 2016. "Uranium Project: Chronology of Major Tailings
Dam Failures (from I960);' Accessed January, www.wise-uranium.org/mdaf.html.
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APPENDIX A. BEST PRACTICES SITE VISIT CHECKLISTS
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Sample Impoundment Condition, Stability, and Safety Checklist
Item
Activity Description
Completed*
(Yes / No / NA)
1. CONDUCT INITIAL IMPOUNDMENT CONDITION ASSESSMENT AND
2. DEVELOP IMPOUNDMENT CONCEPTUAL SITE MODEL
2a
Identify, obtain and review available site documents and data
2b
Conduct a site visit and visual assessment including use of UAS where
appropriate
2c
Make initial determination of risk of failure priority (Check One):**
~ immediate dUrgent ~moderate to high priority
~ Low to moderate priority Q Low priority
2d
If 2c is Imminent, recommend interim risk mitigation measures
3. PERFORM STRUCTURAL STABILITY AND SAFETY ANALYSIS
3a
Assemble qualified investigation team
3b
Perform data gap analysis and impoundment inspection (Use separate
Surface Impoundment Dam Inspection Checklist)
3c
Develop geotechnical investigation plan
3d
Analyze risks of investigation plans using Failure Mode and Effects
Analysis (FMEA) or other risk assessment technique
3e
Develop Contingency, Notifications and Emergency Action Plan (CNEAP)
3f
Evaluate impoundment geotechnical characteristics
3g
Review and analyze geotechnical investigation data
4. DETERMINE HAZARD POTENTIAL CLASSIFICATION (CHECK ONE)
4a
Impoundment Name:
~High ~Significant QLow
5. CALCULATE FACTORS OF SAFETY (FOS) - ENTER FOS CALCULATED VALUE
5a
Impoundment Name:
Static Seismic Liquefaction
6. DEVELOP CONDITION RATING (CHECK ONE)
6a
Impoundment Name:
~Satisfactory QFair QPoor ~Unsatisfactory
7. DEVELOP SURFACE IMPOUNDMENT STRUCTURAL STABILITY AND SAFETY REPORT
8. DETERMINE IF RISK REDUCTION MEASURES ARE NECESSARY
8a
Identify risk reduction measures
8b
Perform or modify FMEA on selected measures
8c
Develop or modify CNEAP (where appropriate)
9. ASSESS AND MITIGATE RISKS FROM PROPOSED MITIGATION
10. TAKE MITIGATION MEASURES BEFORE PROCEEDING WITH THE PROPOSED ACTIVITY
* Explain any No and NA answers; provide documentation and references for Yes answers.
** If the initial determination results in an imminent risk, conduct interim risk reduction/mitigation
measures.
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Sample Surface Impoundment Site Visit Form
Site Name:
Date:
Unit Name:
Operator's Name:
Unit I.D.:
Hazard Potential Classification:
Name:
~ High ~ Significant DLow
Check the appropriate box below. Provide comments when appropriate. If not applicable or not available, record 'N/A'. Any
unusual conditions or construction practices that should be noted in the comments section. For large diked embankments,
separate checklists may be used for different embankment areas. If separate forms are used, identify approximate area that
the form applies to in comments.
YES NO YES NO
1. Tailings saturation depth (in ft. above MSL)?
Feet
18. Sloughing or bulging on slopes?
2. Pool elevation (in ft. above MSL)?
Feet
19. Major erosion or slope deterioration?
3. Decant inlet elevation (in ft. above MSL)?
Feet
20. Decant Pipes:
4. Open channel spillway elevation (in ft. above
MSL)?
Feet
Is water entering inlet, but not exiting
outlet?
5. Lowest dam crest elevation (in ft. above MSL)?
Feet
Is water exiting outlet, but not entering
inlet?
6. If instrumentation is present, are
readings recorded?
Is water exiting outlet flowing clear?
7. Overall, does the impoundment appear stable
(if no, describe below)?
21. Seepage (specify location, if seepage
carries fines, and approximate
seepage rate below):
8. Foundation characteristics adequate (visual
evidence)?
From underdrain?
9. Trees growing on, or rodent burrows in,
embankment? (Indicate diameter below)
At isolated points on embankment
slopes?
10. Cracks or scarps on crest?
At natural hillside in the embankment
area?
11.1s there significant settlement along the crest?
Over widespread areas?
12. Are decant trash racks clear and in place?
From downstream foundation area?
13. Depressions or sinkholes in tailings
surface or whirlpool in the pool area?
'Boils' beneath stream or ponded water?
14. Clogged spillways, groin, or diversion ditches?
Around the outside of the decant pipe?
15. Are spillway or ditch linings deteriorated?
22. Surface movements in valley bottom or
on hillside?
16. Are outlets of decant or underdrains blocked?
23. Water against downstream toe?
17. Cracks or scarps on slopes?
24. Were photos taken during the dam
inspection?
Major adverse changes in these items could cause instability and should be reported for further
evaluation. Adverse conditions noted in these items should normally be described (extent,
location, volume, etc.) in the space below and on the back of this sheet.
Comments:
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SAMPLE SURFACE IMPOUNDMENT SITE VISIT FORM
Impoundment #
Name of Site Visitor(s):
Date
Impoundment Name
Impoundment Company
EPA Region
State Agency (Field Office) Address
Estimated volume of impoundment:
Yes No
Is impoundment currently being maintained?
Is water or liquid waste currently present?
IMPOUNDMENT TYPE OF CONSTRUCTION
Downstream
Upstream
Centerline
IMPOUNDMENT FUNCTION:
Nearest Downstream Town: Name
Distance of town from the impoundment
Impoundment Location:
Longitude Degrees Minutes Seconds
Latitude Degrees Minutes Seconds
State County
Who owns the impoundment?
Is this a PRP lead site?
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EVALUATE HYDRAULIC AND HYDROLOGIC (H&H) CAPACITY
Are there data (or visual evidence) that the impoundment is able to safely accommodate the
inflow design flood (IDF) according to the appropriate IDF per the Hazard Potential
Classification of the impoundment (FEMA 2013b).
Yes: No:
Is there evidence of prior overtopping? Yes: No:
Best Practices to Prevent Releases from Impoundments at Abandoned Mine Sites
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HAZARD POTENTIAL (In the event the impoundment should fail, the following
would occur):
LOW HAZARD POTENTIAL: Dams assigned the low hazard potential classification
are those where failure results in no probable loss of human life and low economic and/or
environmental losses. Losses are principally limited to the owner's property.
SIGNIFICANT HAZARD POTENTIAL: Dams assigned the significant
hazard potential classification are those dams where failure results in no probable loss of human
life but can cause economic loss, environmental damage, disruption of lifeline facilities, or can
impact other concerns. Significant hazard potential classification dams are often located in
predominantly rural or agricultural areas but could be located in areas with population and
significant infrastructure.
HIGH HAZARD POTENTIAL: Dams assigned the high hazard potential
classification are those where failure will probably cause loss of human life.
DESCRIBE REASONING FOR HAZARD RATING CHOSEN:
Best Practices to Prevent Releases from Impoundments at Abandoned Mine Sites
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CONFIGURATION:
Water or SIW
original
ground.
IMPOUNDMENT
CROSS-VALLEY
IMPOUNDMENT
Water or SIW
original
ground
Height
DIKED
Water or SIW
original ground
INCISED
Water or SIW
Cross-Valley
Side-Hill
Diked
Incised (form completion optional)
Combination Incised/Diked
Embankment Height feet
Current Freeboard feet
Embankment Material
Pool Area acres
Best Practices for Preventing Sudden, Uncontrolled Releases
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TYPE OF OUTLET (Mark all that apply)
Open Channel Spillway
Trapezoidal Spillway
Rectangular Spillway
Irregular Spillway
Piped Outlet
Spillway depth
Spillway bottom width
Spillway top width
Piped outlet inside diameter
Piped Outlet Material
Corrugated metal
Welded steel
Concrete
Plastic (HDPE, PVC, etc.)
Other (specify)
Is water flowing through the outlet? YES NO
No Outlet
Other Type of Outlet (specify)
Are there geotechnical soils data available to conduct FOS?
TRAPEZOIDAL
TRIANGULAR
Top Width
< ~
Xi
Depth
Botto
RECTANGULAR
i
Depth
Width
PIPED OUTLET
Top Width
< ~
?
Depth
IRREGULAR
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Has there ever been a failure at this site? YES NO
If So, When?
If So, Please Describe:
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Has there ever been significant seepages at this site? YES NO
If So, When?
If So, Please Describe:
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Has there ever been any measures undertaken to monitor/lower phreatic water table
levels based on past seepages or breaches at this site? YES NO
If So, Which Method (e.g., piezometers, gw pumping)?
If So, Please Describe:
Best Practices to Prevent Releases from Impoundments at Abandoned Mine Sites
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