IC 9508 

INFORMATION CIRCULAR/2008 

The Application of Major Hazard 

Risk Assessment (MHRA) to 

Eliminate Multiple Fatality 

Occurrences in the U.S. Minerals 

Industry 

Department of Health and Human Services

Centers for Disease Control and Prevention

National Institute for Occupational Safety and Health
 

Information Circular 9508 

The Application of Major Hazard Risk Assessment (MHRA) to 

Eliminate Multiple Fatality Occurrences in the US Minerals Industry 

By A. Iannacchione, F. Varley and T. Brady 

DEPARTMENT OF HEALTH AND HUMAN SERVICES 

Centers for Disease Control and Prevention 

National Institute for Occupational Safety and Health 

Spokane Research Laboratory 

Spokane, WA 

October 2008 
 

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DHHS (NIOSH) Publication No. 2009–104 

October 2008 

SAFER • HEALTHIER • PEOPLETM 

ii 
Table of Contents 

Abstract ..........................................................................................................................................1 

Executive Summary.......................................................................................................................2 

Acknowledgement..........................................................................................................................3 

1.0 - Introduction...........................................................................................................................3 

1.1 – Trends in Managing Major Mining Hazards ................................................................4 

2.0 – Minerals Industry Risk Management.................................................................................5 

2.1 – The US Experience ...........................................................................................................5 

2.2 – The Australian Experience ..............................................................................................6 

2.3 – Has the Risk Management Framework Worked to Reduce Miner Injuries? ............7 

2.4 – The Minerals Industry Safety and Health Centre (MISHC)........................................8 

3.0 – Risk Assessment and Analysis Techniques and Tools ......................................................9 

3.1 – Risk Assessment Techniques ...........................................................................................9 

3.2 – Risk Analysis Techniques and Tools ............................................................................11 

4.0 – Elements of an MHRA .......................................................................................................17 

4.1 – Risk Assessment Design (Scoping) ................................................................................17 

4.2 – Risk Assessment Team ...................................................................................................17 

4.3 – Risk Assessment..............................................................................................................18 

4.4 – Effectiveness of Controls................................................................................................20 

4.5 – Audit and Review ...........................................................................................................22 

5.0 - MHRA Pilot Studies at US Underground Mining Operations .......................................23 

5.1 – Rock Reinforcement Process Risk Assessment Case Study .......................................24 

5.3 – Spontaneous Combustion Causing Fire/Explosion Risk Assessment Case Study....33 

5.4 – Underground Workshop Fire Risk Assessment Case Study ......................................40 

5.5 – Water Inundation Risk Assessment Case Study..........................................................49 

5.6 – Escapeway Egress Blockage Risk Assessment Case Study.........................................58 

5.7 – Natural Gas Ingress Risk Assessment Case Study ......................................................67 

5.8 – Conveyor Belt Fire Risk Assessment Case Study........................................................77 

5.9 – Longwall Gate Entry Track Fire Risk Assessment Case Study.................................87 

5.10 –Change of Mining Method Risk Assessment Case Study ..........................................95 

6.0 – Lessons Leaned .................................................................................................................110 

6.1 - The Scoping Document.................................................................................................110 

6.2 - The Risk Assessment Team..........................................................................................110 

6.3 – Important Risk Assessment Tools and Techniques...................................................111 

6.4 - The Risk Assessment Team Outputs (Identified Controls).......................................112 

6.5 – Documentation..............................................................................................................112 

7.0 – Success of Risk Assessment Case Studies.......................................................................114 

7.1 – Existing Risk Management Culture............................................................................114 

7.2 – Risk Assessment Design ...............................................................................................115 

7.3 – Risk Assessment Team .................................................................................................115 

7.4 - The Risk Assessment Process.......................................................................................116 

7.5 – The Extent of Existing Controls..................................................................................116 

7.6 – The Quality of New Ideas.............................................................................................117 

8.0 – Future Use of the MHRA Process in Mining .................................................................118 

9.0 – References .........................................................................................................................121 

APPENDIX B – Action Plan of New Ideas..............................................................................127 

iii 
APPENDIX C – Risk Register..................................................................................................128 

APPENDIX D - Risk Management Culture and Self-Assessment........................................129 

Illustrations 

Figure 1 - Cumulative multiple fatalities over the last 10 years in the US Minerals Industry.......4 

Figure 2 - Principal risk management framework used in Australia..............................................7 

Figure 3 - The running three-year underground mine fatality rates for Australia and the US. ......8 

Figure 4 - An example of a WRAC risk ranking form.................................................................11 

Figure 5 - The Preliminary Hazard Analysis (PHA) Form. .........................................................12 

Figure 6 – Item-by-item risk assessment worksheet for FMEA...................................................13 

Figure 7 - Process analysis form for a HAZOP............................................................................14 

Figure 8 - Bow Tie Analysis (BTA) method................................................................................15 

Figure 9 - Example MHRA team structure (MISHC, 2007). .......................................................18 

Figure 10 - Drill used to install rock reinforcement. ....................................................................26 

Figure 11 - Photograph of shock cords similar to the ones used at the study site........................31 

Figure 12 - Bleederless ventilation system used at the study mine to control spontaneous 

combustion. ...................................................................................................................................34 

Figure 13 - Distribution of prevention controls and recovery measures for the spontaneous 

combustion causing fire/explosion risk assessments.....................................................................37 

Figure 14 - Map showing the location of the maintenance pit with respect to track haulage, 

ventilation stoppings, and intake shaft. .........................................................................................40 

Figure 15 - Distribution of prevention controls and recovery measures for the underground 

workshop fire risk assessment.......................................................................................................45 

Figure 16 - Location of Mines Ea and Eb and adjacent water-filled abandoned mine and 

water/gas filled adits......................................................................................................................49 

Figure 17 - Location of geographic boundaries of the risk assessment. Thick lines define the 

boundaries between the abandoned mines and the current projections for Mines Ea and Eb.......51 

Figure 18 - Graphical depiction of the BTA used in the inundation risk assessment. .................53 

Figure 19 - Techniques used to find the location of water-filled old mine workings. .................54 

Figure 20 - Distribution of prevention controls and recovery measures for the water inundation 

risk assessment. .............................................................................................................................57 

Figure 21 - Escapeways, roof falls and recent roof cracks found at the mine..............................58 

Figure 22 - Six segments of the mine's escapeway system. .........................................................60 

Figure 23 - Roof Fall Risk Index (RFRI) measured in the mine's escapeways............................61 

Figure 24 - Distribution of prevention controls and recovery measures for the escapeway egress 

blockage fire risk assessment. .......................................................................................................66 

Figure 25 - Mine Ga layout showing the location of active faces, the slope and panels within one 

active level.....................................................................................................................................67 

Figure 26 - The risk assessment team created this schematic to illustrate the hazards and 

pathways related to the study mines..............................................................................................69 

Figure 27 - Detailed view of the ventilation circuit used at Mine Ga. .........................................70 

Figure 28 - BTA for mining into an existing oil/gas well top event. Potential causes are listed on
 

the left side of the bow tie with potential recovery measures on the right....................................71 

Figure 29 - Distribution of prevention controls and recovery measures for the natural gas 

inundation risk assessment. ...........................................................................................................76 

iv 
Figure 30 - Mine H layout showing the location of the conveyor belt and working faces. .........77 

Figure 31 - Segments of the conveyor belt system.......................................................................78 

Figure 32 - Conditions within the cribbed area of conveyor belt Segment #2.............................82 

Figure 33 - Distribution of prevention controls and recovery measures for the conveyor belt fire 

risk assessment. .............................................................................................................................86 

Figure 34 - Site conditions at Mine I showing the 3-entry development panel with direction of
 

air flow...........................................................................................................................................87 

Figure 35 - Distribution of prevention controls and recovery measures for the longwall gate 

entry track fire risk assessment......................................................................................................90 

Figure 36 - Diagram of Captive Cut-and-Fill mining method......................................................95 

Figure 37 – A flow chart of the basic stope proposal and mine planning process. ....................105 

Figure 38 - Distribution of prevention controls and recovery measures for the captive cut-andfill change of mining method risk assessment.............................................................................109 

Figure 39 - Percentage of the total controls by category............................................................112 

Figure 40 - Steps along the path to an improved safety culture. ................................................132 

Tables 

Table 1 - Hazard types associated with multiple fatality events in the US Minerals Industry, 

1997-2007........................................................................................................................................5 

Table 2 - A generalized risk matrix used in many qualitative risk analysis techniques.................9 

Table 3 - Examples of variable scales used to determine the maximum reasonable consequence 

associated with different kinds of unwanted events......................................................................12 

Table 4 - Examples of variable scales used to determine the likelihood of occurrence for 

different kinds of unwanted events................................................................................................12 

Table 5 - Examples of variable scales used to define the effects of exposure on risk..................15 

Table 6 - A method to determine the total exposure using a 5 x 5 matrix....................................16 

Table 7 - Estimation of overall likelihood by combining the estimates of likelihood and total 

exposure.........................................................................................................................................16 

Table 8 - The combinations of maximum reasonable consequence and the likelihood of the 

maximum reasonable consequence to establish the most likely consequence level. ....................16 

Table 9 - 5 x 5 risk ranking matrix. ..............................................................................................16 

Table 10 - Categorizing the location and magnitude of the worst hazards using the energy 

approach. .......................................................................................................................................19 

Table 11 - Control categories based on risk reduction effectiveness. ..........................................20 

Table 12 - Characteristics of the 10 MHRA case study sites. ......................................................23 

Table 13 - WRAC of the initial steps in the rock reinforcement process.....................................26 

Table 14 - A 5x5 risk matrix used to rank risk in the rock reinforcement process WRAC..........27 

Table 15 - New ideas for preventing rock reinforcement selection and installation failures. ......27 

Table 16 – Potential heat sources and conditions of the atmosphere in the gob needed to cause a 

fire or an explosion........................................................................................................................35 

Table 17 - Existing key prevention controls for the spontaneous combustion risk assessment. ..36 

Table 18 – Existing key recovery measures for the spontaneous combustion risk assessment....37 

Table 19 - New ideas for mitigating risk of spontaneous combustion. ........................................38 

Table 20 - Fire hazards consisting of potential heat and fuel sources. .........................................41 

v 
Table 21 - Preliminary Hazard Assessment (PHA) form for the underground workshop fire risk 

assessment case study....................................................................................................................42 

Table 22 – Existing key prevention controls for the underground workshop fire risk assessment.
 

.......................................................................................................................................................43 

Table 23 - Existing key recovery measures for the underground workshop fire risk assessment.
 

.......................................................................................................................................................46 

Table 24 - New ideas for an underground workshop fire risk assessment. ..................................47 

Table 25 - Consequences of different inundation mechanisms. ...................................................52 

Table 26 - Summary of existing prevention controls and recovery measures for a potential mine 

inundation......................................................................................................................................55 

Table 27 - New ideas proposed by the risk assessment team for preventing or recovery from an 

inundation at Mines Ea and Eb......................................................................................................56 

Table 28 – Fire hazards consisting of potential fuel and ignition sources....................................60 

Table 29 - Risk ranking of potential threats grouped by escapeway segment..............................62 

Table 30 - A 4 by 5 risk matrix for ranking the potential threats. ................................................62 

Table 31 - Existing prevention controls and recovery measures for a loss of emergency 

escapeway at Mine F. ....................................................................................................................63 

Table 32 - New ideas proposed for preventing or recovery from a loss of emergency escapeway 

at Mine F........................................................................................................................................65 

Table 33 – Existing key prevention controls for the natural gas ingress risk assessment (left side 

of the BTA)....................................................................................................................................72 

Table 34 – Existing key recovery measures for the natural gas ingress risk assessment (right side 

of the bow tie)................................................................................................................................73 

Table 35 - New ideas for mitigating risk of natural gas ingress...................................................74 

Table 36 - Characteristics of eight conveyor belt segments. ........................................................79 

Table 37 - Fuel and heat sources along the conveyor belt............................................................79 

Table 38 – Potential unwanted events for the entire conveyor belt system..................................80 

Table 39 – Three-dimensional risk ranking method used at Mine H. ..........................................81 

Table 40 – The highest priority risks identified by the WRAC....................................................81 

Table 41 - Summary of existing prevention controls and recovery measures from a potential 

conveyor belt fire...........................................................................................................................83 

Table 42 – New ideas proposed by the risk assessment team for preventing or recovery from a 

conveyor belt fire at Mine H. ........................................................................................................84 

Table 43 - Fuel and heat sources found within a longwall track entry.........................................88 

Table 44 - Important longwall track entry characteristics considered in the risk assessment......89 

Table 45 - List of acceptable and unacceptable consequences from a longwall track fire...........89 

Table 46 - New prevention control and recovery measure ideas for the longwall track fire event 

organized by category. .................................................................................................................93 

Table 47 - Hazards associated with captive cut-and-fill mining. .................................................98 

Table 48 - Priority listing of potential unwanted events associated with phases in the captive cutand-fill stoping method at Mine J..................................................................................................99 

Table 49 - Risk Matrix used by cooperating mining company...................................................101 

Table 50 - Highest ranked unwanted events associated with captive cut-and-fill stoping.........101 

Table 51 - Highest priority risks capable of producing a multiple-fatality event.......................102 

Table 52 - Priority existing prevention controls and recovery measures for equipment fires in the 

stope and stope access drift. ........................................................................................................102 

vi 
Table 53 - New prevention control and recovery measure ideas for the equipment fire in the 

intake drift event..........................................................................................................................105 

Table 54 - New prevention control ideas for stope design and mine planning. .........................107 

Table 55 - An assessment of the adequacy / success of the ten MHRA case studies.................114 

Table 56 - Left side BTA for Mine I. .........................................................................................123 

Table 57 - Right side BTA for Mine I. .......................................................................................125 

vii 
UNIT OF MEASURE ABBREVIATIONS USED IN THIS REPORT 

F degrees Farenheight 

ft feet 

ft/s feet per second 

hr(s) hour(s) 

in inch 

lb(s) pound(s) 

min minute 

ppm parts per million 

viii 
 

The Application of Major Hazard Risk Assessment (MHRA) to Eliminate Multiple 

Fatality Occurrences in the US Minerals Industry 

By A. Iannacchione, F. Varley and T. Brady 

NIOSH 

Abstract 

Major Hazard Risk Assessment (MHRA)1

1

 Also referred to as Principal or Catastrophic Hazard Risk Assessment. 

1 

is used to help prevent major hazards, e.g., fire, 

explosion, wind-blast, outbursts, spontaneous combustion, roof instability and chemical and 

hazardous substances, etc., from injuring miners. The structured process associated with MHRA 

helps to characterize the major hazards and evaluate engineering, management and work process 

factors that impact how a mine mitigates its highest risk. The National Institute for Occupational 

Safety and Health (NIOSH) studied the application of this technique to US mining conditions 

through a field-oriented pilot project. Risk assessment teams used in the pilot project were 

primarily composed of mining company personnel. Ten case studies were performed over a 

wide cross-section of mines. These mines were representative of the important mining 

commodities in the US minerals industry, i.e. coal, metal, non-metal, and aggregate. Also, the 

sizes of the mines ranged from small to large and were located across the country. 

The ten case studies demonstrate that most US mines have the capability to successfully 

implement an MHRA and that the MHRA methodology produced additional prevention controls 

and recovery measures to lessen the risk associated with a select population of major mining 

hazards. The basic ingredient for a successful MHRA is the desire to become more proactive in 

dealing with the risks associated with events that can cause multiple fatalities. A successful 

outcome is marked by a thorough examination of existing prevention controls and recovery 

measures. When pressed to consider more controls to further mitigate the risk, a well-staffed 

risk assessment team was able to identify additional controls. For these mining operations, it 

was important to add additional controls, even if they were not required by existing mining 

regulations, to lower the risks associated with the major hazards under consideration. If a mining 

operation is not willing to commit its best people to an MHRA or will not provide them with 

sufficient time to see the process through to its conclusion, the MHRA output may prove to be 

useless. Additionally, if a mining operation is not prepared to discuss its major hazards in an 

open and honest fashion and to present the findings of the risk assessment in a written report, the 

MHRA output will be unclear, and attempts to monitor or audit important controls may not be 

possible. A MHRA is most effective when the mining operation possesses 1) a proper 

understanding of its hazards, 2) experience with informal and basic-formal risk assessment 

techniques, 3) proper facilities, machinery and equipment, 4) suitable systems and procedures 

that represent industry Best Practice, 5) appropriate organizational support with adequate staff, 

communications and training, 6) a formal and thorough plan for emergency response, and 7) a 
safety risk management approach that is promoted and supported at all levels of the organization. 

Executive Summary 

Major Hazard Risk Assessment (MHRA) is a process used to evaluate hazards that can cause 

great harm to a mining operation and its workers if they are not adequately controlled. NIOSH 

evaluated the MHRA process at ten mining operations. The general consensus was that the 

MHRA process provided information considered beneficial for a safer work environment. Three 

of the ten case studies are rated as performing a more-than-adequate risk assessment, five as 

adequate, and two as less-than-adequate. The degree of success was influenced by the existing 

risk management culture at the mining operation, the design of the risk assessment, the 

performance of the risk assessment team, the character of the risk assessment process, the extent 

of the existing controls, and the quality of the new ideas. Lessons learned focused on improving 

the scoping document, the need to adequately train the risk assessment team, the important risk 

assessment tools and techniques, methods to assess the quality and character of the risk 

assessment team outputs, and the significance of the documentation process. 

Fundamental to successful utilization of risk assessment in the MHRA process is company 

support to form a team with the capability and intentions to address all hazards. It is critical that 

the risk assessment be designed to capture the strengths of the MHRA approach in order for it to 

be successful. The strengths of the MHRA approach are its ability to 

1.	 set clear direction to solve specific high-risk problems, 

2.	 focus on priority concerns, 

3.	 establish involvement and commitment from a wide cross-section of the mine’s 

work force, 

4.	 decrease potential losses for mining operations, 

5.	 help to build teams to solve major mining issues, 

6.	 go beyond merely complying with existing mining standards and regulations, and 

7.	 focus upper management attention on issues existing at the operational level. 

Conversely, the MHRA approach is unlikely to prove successful if the following issues or 

concerns take precedence during a risk assessment: 

1.	 inappropriate focus on changes within the existing way the mine conducts 

business, 

2.	 time taken away from activities directly related to production, 

3.	 focus on additional time constraints being placed on a mining operation’s “best 

people,” 

4.	 the cost of implementing new prevention controls and recovery measures, 

5.	 inappropriate alteration of a mining operation’s priorities, 

6. need for there to be an existing risk management structure to build upon, and 

7. need for an openness in management / labor communications. 

This NIOSH pilot project demonstrated that US mines have the capability to successfully 

implement an MHRA and that the basic requirement for a successful MHRA is the desire to 

become more proactive in reducing risks associated with events that can cause multiple fatalities. 

An MHRA can be most effective when the mining operation possesses a proper understanding of 

2 
 

its hazards, has some experience with risk assessment techniques, uses systems and procedures 

that represent industry best, or attains wide organizational support for the MHRA activity. 

The power in the MHRA process comes from the risk assessment team as it examines new ideas 

that will help to further reduce risk. These new ideas are presented to management in the form 

of an Action Plan. This Action Plan is contained within a written document that summarizes the 

risk assessment team’s actions and is presented to management. The Action Plan also suggests 

that management assign a responsible person to evaluate each of these new potential controls and 

recovery measures in a more in-depth manner. Management can then select the new ideas most 

appropriate for their mine. 

Acknowledgement 

The authors would like to thank each of the companies that participated in the pilot project. It is 

not easy for companies to allow persons outside their organization to examine hazards within 

their mining operations. The companies involved did this without reservation and for that we are 

grateful. We would also like to thank NIOSH management for their support and encouragement. 

Lastly, we wish to recognize the guidance and efforts of Professor Jim Joy2

2

 Minerals Industry Safety and Health Centre, University of Queensland, Australia 

3 

in facilitating the 

MRHAs. He was forever teaching and all were his interested students. 

1.0 - Introduction 

The reoccurrence of multiple fatality events in the US Minerals Industry supports the need for 

improvements in the way major hazards are identified, assessed and managed. Many solutions to 

reduce mining disasters have been proposed including additional regulations, improved training, 

more reliable equipment, and better technology. In December of 2006, the National Mining 

Association’s Mine Safety Technology and Training Commission stated that a new paradigm for 

ensuring safety in underground mines was needed. The Commission recommended that the 

industry consider a systematic and comprehensive risk management approach (Grayson et al., 

2006). In March of 2007 during a congressional hearing, the NMA announced its support of a 

risk assessment based approach for the mining industry (Watzman, 2007). In another 

congressional hearing, Davitt McAteer asked that Best Practices be prepared which could be 

used to hold mine operators to a higher standard of care, i.e. risk assessment and risk control 

(McAteer, 2007). 

The elimination of multiple fatality events is arguably one of the most important safety issues 

facing the US Minerals Industry. Ten case studies are presented that use a range of practices to 

lower the risk from site-specific major hazards. These practices ranged from standard to those 

that are leading the industry. This paper evaluates how the use of Major Hazard Risk 

Assessment (MHRA) might help to eliminate multiple fatality events. The MHRA process was 

developed by the Australian mining industry over the last decade as a means of mitigating 

catastrophic hazards from its mining operations. 

 

Most case studies were viewed as successful by the quality of the barriers, controls and recovery 

measures produced during the risk assessment and the responses of the individual risk 
assessment teams. However, some unsuccessful outcomes were also observed. Of particular 

importance was the need to communicate risk management principles to both management and 

labor, the knowledge of the hazards possessed by the team used to conduct the risk assessment, 

and the ability of the existing and proposed prevention controls and recovery measures to go 

beyond simply complying with existing government standards and regulations. This report 

should be viewed as a guidance document to provide the industry with information and tools 

needed to implement a successful MHRA program. 

1.1 – Trends in Managing Major Mining Hazards 

A proven way to manage the many hazards associated with mining is to characterize the risk they 

present and put into place controls that will lower these risks to acceptable levels. Typically risk 

acceptability is characterized by managing risk to as-low-as is reasonably achievable (ALARA) 

or as-low-as is reasonably practicable (ALARP). An industry’s ability to manage risk is often 

measured by its injury and illness rates. If rates are falling and lower than those of other 

developed countries or comparable to other similar high-hazard industries, then that industry is 

considered to have demonstrated a proficiency in managing hazards. One way to examine the 

US Minerals Industry’s proficiency in managing its risks is to examine multiple fatality trends. 

Over the last 10 years, there have been 18 multiple fatality events in the US, fatally injuring 67 

miners (Figure 1). CumulativeMultiple Fatalities ... 

70 

60 

50 

40 

30 

20 

10 

0 

Jan-97 Jan-98 Jan-99 Jan-00 Jan-01 Jan-02 Jan-03 Jan-04 Jan-05 Jan-06 Jan-07 

Date 

Figure 1 - Cumulative multiple fatalities over the last 10 years in the US Minerals Industry. 

Sixteen of the 18 multiple fatality events occurred in coal mines and 15 at underground 

operations. The most frequent event type is strata instabilities with 8 events fatally injuring 21 

miners (Table 1). Explosions were involved in fewer events, 4, but had the highest number of 

fatalities, 33. Powered haulage, fire, heat strain, equipment failure and slip or falls of persons are 

other examples of major hazards in the US Minerals Industry. These data suggest that major 

hazards exist in our nation’s mines capable of causing multiple fatality events. They also support 

the need for additional actions to lesson the impact of these hazards on miner safety. 

4 
 

 

Table 1 - Hazard types associated with multiple fatality events in the US Minerals Industry, 

1997-2007. 

Hazard Type Events Fatalities 

Strata Instabilities 8 21 

Explosions 4 33 

Powered Haulage 2 4 

Fire 1 2 

Equipment Failure 1 2 

Heat Strain 1 2 

Slip or Fall of Person 1 3 

2.0 – Minerals Industry Risk Management 

Risk management systems have been used in many industries to manage inherent hazards in their 

business. In fact, some countries mandate risk management approaches in their minerals 

industries. Others, like the US, produce technically detailed regulations, often reacting to a 

particular disaster, with the purpose of prescribing specific industry actions. By evaluating these 

different approaches to risk management, an assessment can be made of the impact of the risk 

management framework on miner injuries. 

2.1 – The US Experience 

Prescriptive mining standards rely on existing normalized rules, largely based on past-experience 

and current Best Practices, to mandate safety standards. These standards can produce lengthy 

and detailed regulations. Changing technology and mining conditions require the regulations to 

be constantly reviewed and, on occasion, modified. However, prescriptive standards are 

sometimes incapable of dealing with hazards associated with specialized and dynamic mining 

conditions. They can also produce a culture of compliance that does not necessarily emphasize 

leading practice. The above process could potentially lead to a reactive approach towards 

hazards. 

Alternatively, regulatory standards with a General Duty Clause3

3

 In commonwealth countries including the UK, Canada, Australia, and New Zealand, a similar clause is often found 

in regulation referred to as the Duty-of-Care. 

5 

require employers, suppliers and 

employees to provide, design for and adhere to reasonable activities ensuring that workers are 

protected. Many industries, e.g. nuclear, petrochemical, environmental, have used structured risk 

management approaches to develop proactive approaches in managing their risks. In these 

industries, safety plans often focus on a local site’s approach toward assessing risks and 

mitigating these risks through targeted controls. 

The experience of these industries provides an opportunity to examine how a risk management 

approach may help to eliminate major hazards in US mineral industries. In addition, many of the 
commonwealth countries, e.g. United Kingdom, Canada, Australia, New Zealand, have used risk 

management as their guiding principles for current mining standards. Perhaps the country that 

has had the most extensive transition, from a prescriptive-based health and safety philosophy to a 

more proactive, duty-of-care philosophy, is Australia. 

2.2 – The Australian Experience 

In Australia, the minerals industry began its movement towards risk-based management systems 

in the mid-1990s, shortly after the Moura coal mine explosion fatally injured 11 miners 

(Hopkins, 2000). Later in 1996, the Gretley coal mine inundation reinforced the drive for 

change. As a result, industry began using risk analysis methods to mitigate certain key hazards, 

e.g. fires, explosions, inundations, spontaneous combustions, etc. Later, the various regulatory 

bodies in Australia began to mandate safety management plans for principal hazards. In New 

South Wales, the Chief Inspector of Coal Mines (NSWDPI, 1997) published a risk management 

handbook that offers a process to anticipate and prevent circumstances which may result in 

occupational injury or death. Queensland followed (QDME, 1998 and QMC, 1999) with its own 

standard. In Western Australia, where the largest concentration of metal mining occurs, duty-ofcare legislation was enacted in 1994; however, risk management approaches saw less application 

until recently (CMEWA, 2003). Most of these regulations require mines to perform some form 

of risk assessment on a regular basis to address the possibility of unwanted events such as 

spontaneous combustion, gas outbursts, explosions, air blasts, inundations and roof falls. In 

addition, mine managers are generally expected to demonstrate competency in risk-based 

management systems through training and certification. As is evident from this discussion, the 

Australian Minerals Industry performs MHRA, in part, because it is mandated. 

In response to these different approaches to duty-of-care regulations, an Australian Standard on 

Risk Management (Standards Australia, 2004) was established, providing an important risk 

management framework (Figure 2). First, hazards are identified by the location, nature and 

magnitude of energies present within a mine. The risks these hazards present are then identified 

and assessed. Next, the mine operator decides whether to eliminate, mitigate or tolerate these 

mining hazards. Typically it is most effective to eliminate hazards early in the life of a mine 

when design activities are the most prevalent. Mitigation actions can consist of equipment, 

materials, rules, methods, competencies, labels or other mechanisms to control hazards. If a 

hazard is tolerated then administrative controls, specialized training or recover measures are used 

to minimize losses. As these actions are taken, their performance must be monitored. This is 

typically done on a regularly scheduled basis and changes are made to the process as needed. 

6 
Take Action

Decide to 

Tolerate

Decide to 

Eliminate

Monitor for 

Change

Monitor 

Performance

Decide to 

Mitigate

Assess the 

Risks

Identify the 

Risks

Take Action 

Decide to 

Eliminate 

Monitor for 

Change 

Monitor 

Performance 

Assess the 

Risks 

Identify the 

Risks 

Decide to 

Tolerate 

Decide to 

Mitigate 

Figure 2 - Principal risk management framework used in Australia (Standards Australia, 2004). 

2.3 – Has the Risk Management Framework Worked to Reduce Miner Injuries? 

In Australian underground coal mining, following an increasing fatality rate in the early 90s, 

there has been a marked decrease in these same rates over the last 10 years with a dramatic drop 

in the last three years ( 

Figure 3). Unfortunately the fatality rate for US underground coal mining has not seen this same 

drop. In underground Australian metalliferous mining, a significant decrease only occurred in 

the last 5 years. Also, the US metal/non-metal underground mining fatality rate, once well above 

the level for US underground coal, is now consistently lower than coal. It is also worth noting 

that there has not been a coal mine multiple fatality event in Australia since the Gretley 

inundation in 1996; however, there have been two multiple fatality events in metalliferous mines 

(Bronzewing and North Parks) during this same time frame. The general downward trends in 

Australian underground mining fatality rates are, in part, attributed to the introduction and 

acceptance of risk-based management systems. It should be noted that the Australian experience 

also demonstrates the need for continual improvement and government oversight in response to 

improperly managed risk-based management systems (Freeman, 2007). 

7 
Fatality per million hours worked 

0.00 

0.10 

0.20 

0.30 

0.40 

0.50 

1990 1992 1994 1996 1998 2000 2002 2004 2006 

Year 

Australia Underground Coal US Underground Coal 

US Underground Metal/nonmetal Australia Underground Metalliferous 

Figure 3 - The running three-year underground mine fatality rates for Australia and the US. 

2.4 – The Minerals Industry Safety and Health Centre (MISHC) 

To assist in evaluating the MHRA approach, NIOSH sought help from a leading Australian 

institution involved in implementing mineral industry risk management programs. Several major 

companies and the government of Queensland help to form the Minerals Industry Safety & 

Health Centre (MISHC) at the University of Queensland in 1998. This centre conducts research 

and education as well as develops industry resources on risk management topics. MISHC has 

developed a Minerals Industry Risk Management (MIRM) model for achieving “safe 

production” (Joy, 2006), requiring managers to be knowledgeable about hazards inherent in their 

operations and to follow a logical framework to define effective barriers or controls. The MHRA 

approach used in the ten NIOSH case studies follows the approach taught by MISHC and is 

indicative of the approach used by most Australian mining companies to manage hazards with 

multiple fatality potential. MISHC is also responsible for maintaining the Minerals Industry 

Risk Management Gateway or MIRMGATE (www.mirmgate.com). This site was found to be a 

good source for Best Practice hazard management guidelines, lessons learned and innovations. 

8 
 

3.0 – Risk Assessment and Analysis Techniques and Tools 

Risks are determined in terms of the likelihood that an uncontrolled event will occur and the 

consequences of that event occurring. 

Risk = Likelihood of occurrence × consequence 

The above relationship is used in both qualitative and quantitative risk analysis methods. A 

quantitative risk analysis method is a probabilistic estimation of risk where risk is calculated as a 

continuous series from high to low. A qualitative risk analysis method is a basic estimation 

where risks are typically ranked from high to low. Qualitative methods rely on a risk matrix 

similar to that demonstrated in Table 2 where qualitative categories are defined, i.e. low-to-high, 

unlikely-to-likely, etc. 

Table 2 - A generalized risk matrix used in many qualitative risk analysis techniques. 

Likelihood of Occurrence 

High value Medium value Low value 

Consequ

ence 

High value High risk 

Moderate risk 

Low risk 

Medium value 

Low value 

Risk assessment and analysis techniques and tools consist of a systematic, logical set of actions 

used to identify hazards, assess risk, and implement controls to mitigate high-risk conditions. 

These techniques and tools can be described by their levels of formality, the types of analysis 

performed, and the work processes they are attempting to address. 

3.1 – Risk Assessment Techniques 

The most fundamental risk assessment activity, called an informal risk assessment, occurs when 

workers are asked to think about the hazards in the workplace before work commences, 

determine what could go wrong, and report or fix the hazards. More formal risk management 

activities require structured procedures, often focusing on work processes that involve multiple 

levels of an organization. These activities are practiced at some mines and are typically 

organized by an operations safety official and developed with the help of individuals familiar 

with the work practice in question. Higher level risk management activities focus on major 

mining hazards or on major changes in the mining operations involving the entire organization, 

such as reopening a mine, moving to a new location within the mine, and utilizing a new mining 

technique or process. 

3.1.1 – Informal Risk Assessment Techniques 

Most informal risk assessment techniques consist of multiple steps where the worker is asked to 

look for hazards, determine the significance of the hazard, and take some action to mitigate the 

risk. Many systems have been proposed and are widely used in mining. Examples include, but 

are not limited to: 

9 
•	 Stop-Look-Analyze-Manage (SLAM) asks workers to stop and consider the work 

process before it is started, examine the work environment, analyze the work 

process, and manage the risk, 

•	 Take-Two for Safety calls for persons to take 2 minutes to think through a job before 

it starts, 

•	 Five-Point Safety System compels employees to take responsibility for the safety 

within workplace, 

•	 Take Time, Take Charge requires miners to stop, think, assess and respond to 

hazards in their workplace. 

3.1.2 – Basic-formal risk assessment techniques 

Basic-formal risk assessment techniques are characterized by the requirement to follow a 

structured process that occurs prior to performing specific higher risk work activities. These 

techniques also require documentation that allows management to monitor and audit individual 

risk assessment activities. The most commonly used basic-formal risk assessment technique is 

the Job Safety Analysis (JSA). A JSA typically leads to development of Standard Operating 

Proceducres (SOP) that define how to best approach a task considering the hazards identified in 

the JSA. 

A JSA is a technique used to identify, analyze and record the specific steps involved in 

performing a work activity that could have hazards associated with it. JSAs are typically 

performed on work processes with the highest risk for a workplace injury or illness. It is 

essential that all actual or potential safety and health hazards associated with each task are 

identified and that actions or procedures for performing each step that will eliminate or reduce 

the hazard are documented and recorded. Other techniques similar to JSAs include Job Hazard 

Analysis (JHA), Critical Task Analysis (CTA), and Job Hazard Breakdown (JHB). 

An SOP is a set of instructions that act as a directive, covering those features of operations that 

lend themselves to a standardized procedure. An SOP is typically a set of instructions or steps a 

worker follows to complete a job safely and in a way that maximizes operational and production 

requirements. SOPs can be written for work processes by the individual or group performing the 

activity, by someone with expertise in the work process, or by the person who supervises the 

work process. 

3.1.3 – Advanced-formal risk assessment techniques 

Advanced-formal risk assessment techniques require the use of a structured approach that 

incorporates one or more risk analysis tools (see Section 3.2) and produces a documented 

assessment of the risk associated with unwanted events. MHRA, the subject of this 

investigation, is an advanced-formal risk assessment technique. An MHRA can focus on a single 

major hazard, all the relevant major hazards, or an important change of mining method at a 

mining site. One study demonstrates the complexity that a change of mining method can bring 

to the risk assessment. In this case, a full week of effort from a large team was needed with 

multiple risk analysis tools. All other MHRAs studied are focused on a single hazard and were 

completed in 1 to 3 days. 

10 
 

 

3.2 – Risk Analysis Techniques and Tools 

When conducting an MHRA several risk analysis techniques and tools may be needed. A brief 

description of the most common tools follows. 

3.2.1 – Workplace Risk Assessment and Control (WRAC) 

The Workplace Risk Assessment and Control (WRAC) tool is a broad-brush risk ranking 

approach, allowing the user to focus on the highest risk. As applied to a MHRA, this structured 

preliminary analysis begins by breaking down the mining process associated with the potential 

major hazards at the mine in some logical manner. This is often accomplished using a flow chart 

or process mapping technique where the potential major hazards of each step in a work process 

are identified. The mining process could be a breakdown of a major project or a geographical 

breakdown of the underground mine. JSAs and SOPs can be used as a framework for the 

WRAC analysis. 

After preliminary analysis, the team then considers each breakdown segment of the mining 

process and identifies the potential unwanted events associated with the identified hazards 

(Figure 4). The likelihood and consequence of each stage are determined using some variation 

of a risk matrix, followed by a risk rating calculation. 

Part of mine, phase of 

mining, etc. 

Potential unwanted 

event 

Consequence 

Likelihood

Risk rating 

↕

Figure 4 - An example of a WRAC risk ranking form. 

Prior to ranking the hazard, the team must come to an agreement on how to categorize the 

consequences for consistency purposes. Consequences should be considered as either the 

maximum likely or the maximum potential consequence. For example, while the maximum 

potential consequence of a slip/fall is a fatality, the maximum likely consequence is a severe 

injury. Variable scales are often used when determining the maximum reasonable consequence 

associated with different kinds of unwanted events. Table 3 provides some examples of the 

maximum reasonable consequence for safety, equipment, production and environmental risks. 

This table also provides a scale for determining the maximum reasonable consequence of a 

specialized safety event, in this case a mine fire. 

11 
 

 

 

 

 

 

Table 3 - Examples of variable scales used to determine the maximum reasonable consequence 

associated with different kinds of unwanted events. 

Safety Equipment Production Environment Mine Fire 

1 Multiple fatalities > $ 5 M 1Week > $ 5 M Huge fire 

2 1 Fatality $ 1 M 1 Day $ 1 M Major fire 

3 Major lost-time injury 

(LTI) 

$200 K 1 Shift $200 K Moderate fire 

4 Avg LTI (4-5 days) $50 K 1 Hour $50 K Small fire 

5 Minor injury (1 day or less) < $ 10 K <1 Minute < $ 10 K Smoldering 

LTI = lost time injuries 

M = million 

K = thousand 

The ranking of likelihood will be influenced by the choice of consequences. There is no correct 

choice, but there is a need to be consistent in the application of ranking across the exercise. 

Examples of variable scales used to determine the likelihood of different kinds of unwanted 

events is given in Table 4. 

Table 4 - Examples of variable scales used to determine the likelihood of occurrence for different 

kinds of unwanted events. 

Based on Maximum Reasonable Consequence Based on the Events / Year 

1 Common Highly likely Expected > 10 

2 It has happened Likely High 1 to 10 

3 Possible Possible Moderate 0.1 to 1 

4 Unlikely Unlikely Low 0.01 to 0.1 

5 Almost impossible Very unlikely Not Likely < 0.01 

3.2.2 – Preliminary Hazard Analysis 

The Preliminary Hazard Analysis (PHA) is another broad-brush risk ranking approach. Like the 

WRAC, this tool identies all potential hazards and unwanted events that may lead to miner 

injuries and ranks the identified events according to their severity. Its main purpose is to identify 

those unwanted events that should be subjected to further, more detailed risk analysis. Once the 

potential unwanted events are risk ranked by the team, they can be prioritized so that the highest 

risk unwanted event is listed first and so on. The technique or form for the PHA method is 

shown in Figure 5. 

# Description of potential unwanted 

event 

Total Exposure Likelihood Most Likely 

Consequence 

Risk 

Rank 

1 

2 

3 

4 

Etc. 

Figure 5 - The Preliminary Hazard Analysis (PHA) Form. 

12 
 

3.2.3 – Failure Modes, Effects and Analysis (FMEA), also FMECA 

Generally, an FMEA is used to determine where failures can occur within hardware and process 

systems and to assess the impact of such failures. For each item, the failure modes of individual 

items are determined, effects on other items and systems are recognized, criticality is ranked, and 

the control is identified (Figure 6). 

Item Failure 

Mode 

Effects on Likelihood 

(L) 

Consequence 

(C) 

Criticality 

(LxC) Other Control 

items System 

↕

Figure 6 – Item-by-item risk assessment worksheet for FMEA. 

Robertson and Shaw (2003) provide an example of the application of the FMEA approach where 

the risks to the environment, workers and the public associated with the closure of a mine were 

identified. This was accomplished by developing a FMEA worksheet for potential unwanted 

events post-closure of the mine. 

3.2.4 – Fault / Logic Tree Analysis (FTA/LTA) and Event / Decision Tree Analysis (ETA/DTA) 

The Fault and Logic Tree Analysis are systematic, logical developments of many contributing 

factors to one unwanted event. The FTA evaluates the one unwanted event while the LTA 

evaluates a wanted outcome. With both tools it is necessary to first clearly define the top event, 

followed by an analysis of the major potential contributing factors. Each contributing factor is 

broken down into discrete parts. A logic tree can be used to test the analysis with the use of 

“and/or” gates. Factors can be ranked from major to lesser. The product of the analysis is a 

deductive list of potential hazards. This tool is well-suited to quantitative risk analysis 

techniques when probabilities for each factor can be assigned. 

Systems engineering and operations research approaches use a decision tree (or tree diagram) to 

help examine the decision. Event and decision tree analysis (ETA or DTA) uses graphical 

models to examine the consequence of decisions. A decision tree is used to identify the strategy 

most likely to produce a desired outcome. In the tree structures, leaves represent classifications 

and branches represent conjunctions of features that lead to those classifications. These tools are 

appropriate for establishing lines of assurance and determining their success and failure in 

preventing accidents. 

13 
 

 

 

 

3.2.5 – Hazard and Operability Studies (HAZOP) 

Hazard and Operability Studies or HAZOPs have been used extensively in the chemical 

industries to examine what impact deviations can have on a process. The basic assumption when 

performing a HAZOP is that normal and standard conditions are safe and hazards occur only 

when there is a deviation from normal conditions. A HAZOP can be conducted during any stage 

of a project although it is most beneficial during the later stages of design. Typically a process 

or instrumentation diagram is used to trace the properties of materials or products through a plant 

by breaking down the process node by node (Figure 7). The properties can be flow, level, 

pressure, concentration or temperature. What-if guidewords are used to identify possible 

deviations. A HAZOP typically lacks a risk calculation. 

Process Unit:_________________________________________________________________ 

Node: ________________ Process Parameter: _____________________________ 

Guide Deviation Consequence Causes Suggested Action 

↕

Figure 7 - Process analysis form for a HAZOP. 

3.2.6 – Bow Tie Analysis 

The Bow Tie Analysis (BTA) was developed by Shell Oil in the 1980s as part of its Tripod 

package of concepts and tools for managing occupational health and safety in its business. The 

“Top Event” in the BTA is a statement about the initiating event that might lead to the major 

consequence (Figure 8). Threats (also referred to as potential causes) are discussed and controls 

examined that could mitigate the hazard (left side of the bow tie). Next, the consequences (also 

referred to as the potential outcomes) of the initiating unwanted event are identified and recovery 

control measures examined to reduce or minimize the loss (right side of the bow tie). 

14 
PREVENTION

RECOVERY

Potential 

causes

Potential 

outcome

Control 

measures

Recovery 

measures

Threat Consequence

Threat

Threat

Consequence

Consequence 

Top unwanted 

event

PREVENTION 

RECOVERY 

Potential 

causes 

Potential 

outcome 

Control 

measures 

Recovery 

measures 

Threat Consequence 

Threat 

Threat 

Consequence 

Consequence 

Top unwanted 

event 

Figure 8 - Bow Tie Analysis (BTA) method. 

 

Together, the prevention controls and recovery measures identified represent a comprehensive 

list of actions required to adequately control the hazard. Often these actions are assigned to 

individuals and controlled by the management planning and monitoring tool known as a risk 

register. A risk register provides for continuity in the way an organization deals with risks even 

as changes occur in management. 

3.2.7 – Work Process Flow Chart 

All mining processes have supplies, inputs, processes and outputs. Mining processes are sets of 

activities that produce a desired outcome. Many of these activities can be thought of as loops. If 

the outputs are wrong then adjustments are made to the inputs or the process. Defining these 

work processes in a step-by-step manner produces a flow chart that can be used in risk 

management. Flow charts are meant to describe a large, sometimes complex, process as small 

elements. Hazards are easier to identify and characterize with this type of systemic approach. 

3.2.8 – Exposure and Risk 

When miners are exposed to variable contact with hazards, it is often useful to determine the 

influence of exposure associated with different work processes or at particular work sites. An 

example of the variable scales used to define the effects of exposure on risk is given in Table 5. 

Table 5 - Examples of variable scales used to define the effects of exposure on risk. 

Exposure (% of workforce) Frequency of exposure 

1 Most > 50% Continuous 

2 Many – 30% Several times/day 

3 Several – 10% Once a day 

4 A few – 5% Weekly 

5 Very few < 1% Monthly 

15 
 

There are many ways to account for exposure when performing a risk analysis. One example is 

provided in Table 6. Here, the total exposure is estimated by combining the effects of the 

frequency of individual miner exposure versus the exposure to the total workforce. 

Table 6 - A method to determine the total exposure using a 5 x 5 matrix. 

TOTAL EXPOSURE 

Frequency of exposure (Table 5) 

1 2 3 4 5 

Continuous Several x/day 1/day 1/week 1/month 

Exposure

(Table 5) 

1 Most > 50% A A B C D 

2 Many – 30% A B C D E 

3 Several – 10% A C D E E 

4 A few – 5% B D E E E 

5 Very few < 1% C D E E E 

Once the total exposure level has been estimated, this value can be used to determine the overall 

likelihood (Table 7) and consequence (Table 8) of potential unwanted events occurring. 

Table 7 - Estimation of overall likelihood by combining the estimates of likelihood and total 

exposure. 

LIKELIHOOD OF AN Total exposure (Table 6) 

EVENT A B C D E 

Likelihood(Table 5) 

Common A A A B C 

Has happened A B B C D 

Possible B C C D E 

Unlikely C D D E E 

Very unlikely D E E E E 

Table 8 - The combinations of maximum reasonable consequence and the likelihood of the 

maximum reasonable consequence to establish the most likely consequence level. 

MOST LIKELY 

CONSEQUENCE 

Likelihood of the Consequence (Table 4) 

Highly likely Likely Possible Unlikely Very unlikely 

Maximum 

Reasonable 

Consequence 

(Table 3)

Multi-fatality A A B C D 

1 fatality A A B C D 

Serious LTI B B C D E 

Avg LTI C C D E E 

Minor LTI D D E E E 

The total probability and consequence of the potential unwanted event are then determined using 

a 5 x 5 risk ranking matrix (Table 9). 

Table 9 - 5 x 5 risk ranking matrix. 

RISK RANK Overall Likelihood (Table 7) 

A B C D E 

Overall 

Consequence 

(Table 8) 

A 1 2 3 7 11 

B 3 5 8 12 16 

C 6 9 13 17 20 

D 10 14 18 21 23 

E 15 19 22 24 25 

16 
4.0 – Elements of an MHRA 

The elements of the MHRA approach used in the case studies are established and published by 

MISHC (www.mishc.uq.edu.au). During these studies, MISHC personnel assisted NIOSH in 

conducting the MHRA. Training on the MHRA process was given to participants when possible. 

A risk assessment scope and the potential team participants were most often identified during 

these training sessions. 

4.1 – Risk Assessment Design (Scoping) 

The risk assessment design or scope is best defined prior to the MHRA exercise. Major hazards 

to be discussed, decisions on risk assessment team membership, and time allotment for the 

activity are best addressed with a scoping document. This document provides an opportunity to 

break down the MHRA process into reviewable parts containing the following information: 

1.	 An objective statement that identifies potential major hazards of interest to the 

mining operation, 

2.	 The boundaries of the mining system or work process, 

3.	 The risk analysis methods and risk assessment tools, 

4.	 The names of potential team members, 

5.	 The time and dates of the MHRA, 

6.	 The location of the MHRA, 

7.	 Determination of the potential data requirements, i.e. in-house safety statistics, 

MSHA data related to the hazard(s), and similar assessments from the MIRMgate 

website (www.mirmgate.com), 

8.	 The use of experts from outside the mining operation, and 

9.	 The types of documents that will be produced. 

4.2 – Risk Assessment Team 

A fundamental part of an MHRA is the risk assessment team. This team must include an 

appropriate cross-section of knowledgeable persons familiar with the hazards to be investigated 

(Figure 9). The team must be capable of identifying all relevant hazards, unwanted events and 

possible controls. The process leader is the facilitator who has the appropriate qualifications, 

knowledge and experience. The facilitator is responsible for following a quality risk assessment 

process designed to meet the risk assessment scope and is responsible for making sure the team 

and the process remain focused on a quality output. It is important for the facilitator to act as a 

teacher and coach without dominating the discussion while making sure to avoid conflict and 

imbalance in involvement of team members. Open ended questions are often used to elicit 

participation from the group. 

It is also important to consider non-management/labor entities for team participation. Miners 

responsible for performing tasks that are part of the work processes under review can validate 

information and provide insight, perspective and ideas that are invaluable to a quality output. 

These team members are also helpful in communicating adherence to existing prevention 

controls and recovery measures and in embracing changes brought about by the application of 

new ideas. 

17 
Experience

Base

Operation 

Supervisor

Labor

Expert

Manager

Maintenance 

Supervisor

Engineer

Facilitator

Labor

Experience 

Base 

Operation 

Supervisor 

Labor 

Expert 

Manager 

Maintenance 

Supervisor 

Engineer 

Facilitator 

Labor 

Figure 9 - Example MHRA team structure (MISHC, 2007). 

The individuals assigned to the MHRA should fully dedicate their time to this effort during the 

assessment. It is very important for team members to receive instruction on the MHRA approach 

prior to the risk assessment. The time allotted for the MHRA should be determined by the 

complexity of the topic. A focused topic could be done in one day, while more complex topics 

or a site-wide MHRA could take 3 to 5 days. The venue for the activity is also important. The 

location should be quiet, free from disruptions, with tables set in a U-shaped pattern to promote 

discussions and equality among members. 

4.3 – Risk Assessment 

Five basic steps make up the MHRA process: 

1. Identify and characterize major potential mining hazards, 

2. Rank potential unwanted events, 

3. Determine important existing prevention controls and recovery measures, 

4. Identify new prevention controls and recovery measures, and 

5. Discuss implementation, monitoring and auditing issues. 

4.3.1 – Identify and Characterize Major Potential Mining Hazards 

The first step is to identify all relevant hazards or possible problems that could lead to a potential 

multiple fatality event. If the list is incomplete, the risk assessment will be inadequate. The 

types of hazard that should be identified are best thought of as uncontrolled releases of energy 

that have the potential to cause significant harm (Standards Australia, 2004). The energy 

approach is used to think about what could go wrong specifically at a mining operation. If an 

accident can be thought of as an uncontrolled release of energy, then it follows that the risk of an 

accident is higher when the energy is large. An exact measure of energy is not needed, only 

18 
recognition that it can do serious harm. Potential energies inherent in many mines are contained 

within the roof and rib of the underground mine, the highwall of the surface mine, the chemical 

energy in toxic or explosive gases, and the fluid energy of water above or adjacent to the mine 

workings. The process of mining also brings large-scale energy into the mining environment, i.e. 

the mechanical energy in mobile and processing equipment, the shocking energy in electrical 

equipment, the air and hydraulic pressure in fluid systems, etc. Energy that is not completely 

controlled leads to some level of risk, depending on the likelihood of release and the 

consequences should the energy be released. When the unwanted release occurs, it can cause 

serious injuries. Table 10 is used to list typical sources of energy and to characterize their 

possible locations and magnitudes. 

Table 10 - Categorizing the location and magnitude of the worst hazards using the energy 

approach. 

Hazard (Energy approach) Location Magnitude (worst case) 

4.3.2 – Rank Potential Unwanted Events 

After a comprehensive list of hazards is identified and characterized, a broad-brush risk 

assessment tool such as the WRAC or PHA is used to risk rank the potential unwanted events. 

Depending on the topic, the individual hazards should be broken down using a process mapping 

technique or by the geographic location within the mine. For each step in the work process or 

for each geographic location within the mine, a likelihood of occurrence and a consequence for 

each potential hazard are determined. It should be noted that in some MHRA case studies, 

likelihood is ignored because the consequences of the unwanted event are deemed significant. 

For all field studies, a qualitative risk ranking procedure is used, integrating some variation of 

the risk matrix shown in Table 2. At the conclusion of this step, the team has successfully 

ranked the risk. The highest rank risks are almost always unacceptable and the lowest rank risks 

are often acceptable. 

4.3.3 – Determine Important Existing Prevention Controls and Recovery Measures 

Additional risk assessment tools are used to help determine what prevention controls and 

recovery measures are currently being used. In most cases, the BTA or the work process flow 

chart are excellent tools to conduct detailed analysis of the highest ranked risks. At the end of 

this step, a detailed list of all existing prevention controls and recovery measures for the hazard 

in question are documented so they can be monitored and audited on some regular basis. 

4.3.4 - Identify New Prevention Controls and Recovery Measures 

The same process that identifies existing prevention controls and recovery measures is used to 

identify new prevention controls and recovery measures. This is a crucial step since it 

potentially produces a list of actions to be investigated that are capable of further reduction of 

risks at an underground mine site. It is important for management to consider the merits of each 

19 
new idea suggested by the risk assessment team. Typically, these new ideas are presented in the 

form of an action plan. 

4.3.5 - Discuss Implementation, Monitoring and Auditing issues 

A document is produced at the conclusion of the MHRA that focuses on a description of the 

hazards examined, the ranks of the potential risks, and a summary of both existing and new 

prevention controls and recovery measures. The document does not rank the new ideas nor 

should it attempt to define a specific course of action or recommend a specific design solution 

for management. A post-risk assessment presentation by the team to management is made to 

gain acceptance and understanding of the MHRA outcomes. Two key responses from 

management are needed. First, management needs to make sure that all existing prevention 

controls and recovery measures identified by the risk assessment team are monitored, audited, or 

investigated to ensure that unacceptable risks are controlled. Second, all suggested new ideas 

should be, at a minimum, investigated. 

4.4 – Effectiveness of Controls 

The important output of the risk assessment team is the list of existing and new controls. 

Assessing the quality of this output can only be accomplished when the effectiveness of these 

controls is understood. In this study, the controls were categorized using a hierarchy framework 

(Table 11) used by MISHC personnel. When a hazard is eliminated, the risks associated with the 

hazard are also eliminated. This should always be the first action of the risk assessment team – 

to investigate how to eliminate the hazard. However, this is usually difficult to do, since a 

hazard can owe its origin to many different factors. Some of these factors are poorly understood, 

while others may represent a condition of business that is perceived to be difficult to change. 

Table 11 - Control categories based on risk reduction effectiveness. 

Control Category Based on 

Hierarchy Framework 

Major Control 

Issues 

Potential for Human 

Error 

Risk Reduction 

Effectiveness 

Eliminate Hazard (EH) Economic/strategic Doesn’t exist Complete 

Minimize/Substitute Hazard (MH) Engineering Human error plays a 

minor role High Physical Barriers (PB) 

Warning Devices (WD) Assessing Human error is possible Medium 

Procedures (P) Administrative and 

work processes 

Human error can play 

an important role Low Personnel Skills and Training (PST) 

If it is not possible to eliminate the hazard, attempts must be made to mitigate the potential 

effects of the hazard. Mitigation consists of actions to minimize the hazards (MH), most often 

with engineering methods, or to implement physical barriers (PB) capable of separating the 

hazard from the worker or the work process. Warning devices (WD) are often used to assess the 

performance of engineering controls (MH) and physical barriers (PB) or to prompt a change in 

administrative or work processes. Controls that are largely focused on operational and work 

process issues consist of procedures (P) and personnel skills and training (PST). Procedures (P) 

can often rely on the personnel skills and training (PST) of the worker. The reliance on worker 

behavior increases the potential for human error and reduces the risk reduction effectiveness 

when compared to mitigation efforts (Table 11). If controls fail to prevent the unwanted event or 

are not possible, then the hazard is tacitly tolerated and recovery measures are put into place to 

20 
minimize losses. It is then appropriate to consider the hazard as a real threat and not just a 

potential threat. Recovery measures can include all control categories listed in Table 11. 

Analyses of the ten case studies presented in this report require an evaluation of the controls 

identified by the risk assessment teams. These controls are the principal output of the MHRA. 

To accommodate this analysis, every identified control was assigned to one of the categories 

listed in Table 11. The characteristics of each category are given below: 

Eliminate Hazard (EH) – The characteristics of this category are self-evident – 

elimination of the hazard under consideration. This can also be done with changes in 

equipment, changes to the mining process or method, or changes in the location of the 

hazard which eliminate personnel exposure. 

Minimize or Substitue Hazard (MH) – The characteristics of this category consist mainly 

of engineering controls, i.e., improved ventilation, fire fighting equipment, backup 

systems, fire suppression systems, use of an event simulator, enhanced information about 

the hazard, improved construction / drilling / exploration techniques, electrical 

component performance characteristics and fault protection, designing to standards, 

improved equipment (values, brakes, tubing, etc.), available medical and rescue teams, 

etc. 

Physical Barriers (PB) – The characteristics of this category are focused on physical 

barriers that separate the hazard from the worker, i.e., roof rock reinforcement, equipment 

skirting and guarding, sealing, rock dusting, refuge chambers, shielding, barriers, walls, 

special containers, heat wraps, self-rescuers, personal protective gear, etc. 

Warning Devices (WD) – This category is primarily concerned with systems that monitor 

environmental / equipment conditions, i.e., gas monitors, PEDs, sampling pumps, gages, 

extensometers, tags, indicators, microseismic monitors, bag samples, alarms, sirens, 

certain kinds of communication systems, etc. 

Procedures (P) – The characteristics of this category concentrate on processes conducted 

by workers and management, i.e., policies, inspections, checks, documentation, methods, 

roles, definition, restrictions, audits, purchases, investigations, standards, trigger action 

response plans (TARP), duties, work orders, updates specifications, process 

requirements, etc. 

Personnel Skills and Training (PST) – The characteristics of this category center on 

training needs, personnel needs, required competency, testing, estimate consequences, 

reinforcing skills, mentoring, communication, expertise, behavior controls, operator 

errors, operator sensors, inspection quality, observation of conditions, introductions, 

clarification, etc. 

An MHRA risk assessment team should strive for the high end of the hierarchy of controls. 

Some attempt must be made to at least consider how the hazard might be eliminated. This is 

often most easily accomplished in the early stages of a mining project’s life cycle. Most often, 

21 
the controls identified during the MHRA attempt to mitigate the hazard or to tolerate the hazard 

by putting into place recovery measures that will minimize losses. The team should be cautious 

of an over-reliance on warning devices that require manual readings, administrative procedures, 

and the personnel skills and training of the work force. In general, an MHRA should strive to go 

beyond the standards and regulations requirements for mining. 

4.5 – Audit and Review 

After an MHRA, a re-assessment of the site’s hazards and an evaluation of the implemented risk 

mitigation program should be done on a regular basis by skilled and experienced personnel. It is 

also appropriate to audit and review the MHRA when rapid changes occur in some relevant work 

process or operational factor, i.e. design, construction, etc. In these cases, the audit and review 

can focus on the part or condition that is actually undergoing the change. An audit and review 

should, at minimum, determine the status of the risk management plan and make 

recommendations for improving potential deficiencies in the plan. Tools, such as a risk register, 

are sometimes used to help with auditing and reviewing important controls at a mining operation. 

22 
 

 

5.0 - MHRA Pilot Studies at US Underground Mining Operations 

Ten case studies were performed at a wide cross-section of underground mines (Table 12). The 

mines make up important sectors of the US minerals industry, i.e. coal, metal, nonmetal and 

aggregate. The sizes of the mines ranged from small (< 50 miners) to large (>450 miners). 

Important mining states were represented in the pilot project including Pennsylvania, Ohio, West 

Virginia, Colorado, Montana, New Mexico and Alaska. 

Table 12 - Characteristics of the 10 MHRA case study sites. 

ID Section Size Duration, 

days 

Commodity Risk Assessment Topic 

A 5.1 Large 1.5 Metal Rock reinforcement process 

B 5.2 Small 0.3 Stone Unplanned detonation of a production blast 

C 5.3 Large 2 Coal Spontaneous combustion causing fire/explosion 

D 5.4 Large 2 Coal Underground workshop fire 

E 5.5 Small 1 Coal Water inundation 

F 5.6 Small 1 Stone Escapeway egress blockage 

G 5.7 Medium 2 Nonmetal Natural gas ingress 

H 5.8 Medium 3 Coal Conveyor belt fire 

I 5.9 Large 2 Coal Longwall gate entry track fire 

J 5.10 Large 4 Metal Captive cut and fill change of mining method 

These case studies document the MHRA performed at underground mines and discuss how risks 

for multiple fatality events were potentially reduced by reinforcing existing practices and 

processes and by adding new prevention controls and recovery measures. The common 

objective of these MHRAs is to 1) identify potential hazards that could cause a multiple fatality 

event, 2) determine which unwanted events pose the greatest threat for the mine, and 3) identify 

a potential plan to prevent the threat or recover from the consequence of the event happening. 

The controls typically consist of a broad spectrum of prevention, monitoring, first response, and 

emergency response techniques and help to move an operation from a reactive to a proactive 

approach towards safety. 

Cooperating mining operations were typically selected after they first participated in a 3-day 

Workshop on Minerals Industry Risk Management. This workshop was organized by NIOSH 

and taught by Professor Jim Joy of the University of Queensland, the primary MISHC participant 

in the pilot project. Two workshops occurred, August 3-5, 2006, in Spokane, Washington, and 

December 18-20, 2006, in Pittsburgh, Pennsylvania. In many cases, the cooperating mining 

operations selected the hazard to be examined during the case study during, or shortly after 

attending, the above workshops. 

23 
5.1 – Rock Reinforcement Process Risk Assessment Case Study 

Mine A is a relatively new operation located in a remote area. This operation is using a 

mechanized cut-and-fill method to mine a vein deposit. After the ore is blasted and mucked at 

underground faces, it is trucked to a surface processing facility for gold recovery using gravity, 

chemical and pyro-metallurgical processes. 

Representatives from the mine’s parent company attended a NIOSH-sponsored MHRA training 

course where two risk assessment scoping topics were identified. 

5.1.1 - Risk Assessment Scope 

Two risk assessment scopes were originally proposed: 

•	 Mine Fire Risk Assessment - 1) review hazards associated with the potential for an 

equipment fire in the intake air stream, 2) evaluate strategies and techniques for early 

detection of the hazard, and 3) evaluate the escape and emergency response plan for a 

major fire at this mine. 

•	 Dissolved Oxygen Plant Risk Assessment - 1) review hazards associated with the 

dissolved oxygen plant, 2) evaluate strategies and techniques for early detection of the 

hazard, and 3) evaluate the escape and emergency response plan for the major hazard and 

impact on other site facilities. 

5.1.2 – Risk Assessment Team 

Two teams were formed by the cooperator and were designated to spend one day on each topic. 

The first team represented underground mine operations and included: 

 Mine manager 

Mobile maintenance foreman 

Miner 

Mine operations trainer 

 Safety coordinator 

 Safety/human resources manager 

NIOSH observer 

Facilitator – MISHC (University of Queensland) 

The second team included processing plant personnel: 

Assistant mine manager 

Processing plant safety trainer 

 Maintenance engineer 

 Maintenance foreman 

 Maintenance superintendent 

 Plant labourer 

Mechanic 

Electrician 

NIOSH observers 

Facilitator – MISHC (University of Queensland) 

24 
Both teams had representatives from a wide cross-section of the mine. Each team pursued an 

independent risk assessment. 

5.1.3 - Structure of the Risk Assessment: 

After the initial meeting of the mine’s appointed risk assessment team, it became apparent that 

the team lacked adequate training in fundamental risk management principles and were 

unfamiliar with risk assessment techniques and tools. In addition, the risk assessment team did 

not have the necessary expertise to sufficiently analyze the process identified in the risk 

assessment scope. Without an understanding of risk assessment techniques and tools and a lack 

of knowledge about the processes to be analyzed, it was decided that an MHRA could not be 

performed on the suggested topics. The team decided instead to focus on a general hazard 

identification and job/process mapping discussion aimed at introducing risk assessment 

techniques to the operations. 

To maximize the training potential associated with this case study, half of each day was 

dedicated to instruction/training and the other half to developing a JSA for a key process. The 

underground and surface teams were made up of management, front line supervisors, 

tradespersons, engineers and labor. The development of JSAs reinforced the concepts of 

controlling energies through design of appropriate work processes. 

5.1.4 – New Risk Assessment Topics: 

After the instructional aspects of the risk assessment were completed, both teams identified a 

critical safety process that could be mapped and examined by the WRAC tool. The underground 

operations team decided to examine the process associated with the selection and installation of 

rock reinforcement. The process plant operations team selected repair of a frequently failing 

slurry pump. Neither of these potential hazards represented a high-consequence event that might 

lead to a multiple fatality accident, but they did represent problems relevant and instructive to the 

case study participants. 

5.1.4.1 - Rock Reinforcement Process: 

Mine A uses an automated drill to install rock reinforcement (Figure 10). The underground 

operations team was able to rapidly describe the steps in the selection and installation of rock 

reinforcement, as follows: 

1. Scale 

2. Select bolt size and type 

3. Select bolt pattern 

4. Stock machine with supplies 

5. Move machine into heading and set-up 

6. Drill back hole 

7. Insert bolt 

8. Anchor wire mesh screen (repeat steps 6, 7 and 8 until ring is complete) 

9. Advance to next ring (start at step 6) 

25 
Figure 10 - Drill used to install rock reinforcement. 

The team then attempted to identify the hazards for each step in the rock reinforcement process 

and rank the associated risks. This was accomplished with a WRAC. Every potential unwanted 

event was examined and their Maximum Reasonable Consequence (MRC) and likelihood of 

occurrence were determined. Due to time constraints, only hazards associated with steps 1 

through 5 were examined during the exercise. These steps included scaling (step 1), the 

selection of bolts and patterns by the miner (steps 2 and 3), and the set-up (steps 4 and 5) of the 

machine by the miner, i.e. choosing drill bit sizes, etc. (Table 13). Risks were ranked using a 

5x5 matrix (Table 14). 

Table 13 - WRAC of the initial steps in the rock reinforcement process. 

Step in Process Unwanted Event MRC Likelihood Rank 

1. Scale fresh ground Person in poor position C 4 9 

Bar too heavy C 2 17 

Ground not scaled B 4 5 

Poor quality scaling B 4 5 

2. Select bolt type & size Wrong bolt selected for conditions B 4 5 

Correct bolt unavailable, substitute bolt 

inadequate for pattern 

A 4 2 

Short bolts installed intentionally B 4 5 

3. Select Pattern Wrong pattern selected for conditions B 4 5 

4. Stock Machine Improper lifting of materials C 3 13 

5. Machine Set-up Incorrect bit size selected for bolt B 4 5 

Machine positioned too far forward B 3 8 

Moving energized cable by hand B 1 16 

26 
 

 

 

 

Table 14 - A 5x5 risk matrix used to rank risk in the rock reinforcement process WRAC. 

Likelihood of Occurrence 

Maximum 

Reasonable 

Consequence 

5-Common 

(>1/week) 

4-Likely 

(1/month) 

3-Moderate 

(1/year) 

2-Unlikely 

(1/several years) 

1-Very Unlikely 

(almost never) 

A-Multiple Fatality 1 2 4 7 11 

B-Fatality 3 5 8 12 16 

C-Lost-time Injury 6 9 13 17 20 

D-Reportable Injury 10 14 18 21 23 

E-First Aid Injury 15 19 22 24 25 

The results of this partial WRAC were then subjected to a Bow Tie Analysis (Figure 8). The 

highest unwanted events from the WRAC (Table 13) formed the center of the bow tie. The 

reliance on the judgement of the miner to manage these five critical steps was identified as a key 

vulnerability by the risk assessment team. 

The risk assessment team then identified existing and new controls to manage these top 

unwanted events, i.e. the left side of the BTA. For example, the team identified the use of long 

(14-ft) scaling bars and the training and experience of the miners as the existing controls. In 

addition, several new controls were suggested by the team to increase the training effort 

associated with the rock reinforcement process (Table 15). In particular, the risk assessment 

team recommended that front line supervisors should monitor the rock reinforcement process by 

the miners on a daily basis. 

Table 15 - New ideas for preventing rock reinforcement selection and installation failures. 

New prevention ideas 

NI1 Improve training and monitoring of miners in selection of bolts and patterns 

NI2 Improve training and monitoring of miners in proper set-up of machine 

NI3 Improve training of miners in use of scaling bars, only use 14-ft bars 

NI4 Improve training in lifting and keep material storage area clean 

NI = New Ideas 

Time constraints prohibited a complete analysis of the remaining steps in the rock reinforcement 

cycle. It was understood that the group would continue the risk assessment on their own, 

examining the other steps in the rock reinforcement process in a similar manner. At the end of 

this process, a complete list of existing controls and recovery measures would be compiled and 

the new ideas examined to produce a Rock Reinforcement JSA. This JSA would be used to 

support the training of those involved in the rock reinforcement process and monitor their 

performance. 

5.1.4.2 - Slurry Pump Repair Process: 

After the morning training session the surface operations team mapped the process for repairing 

the slurry pump: 

1. Notify control room 

2. Lockout pump valves 

3. Secure connecting values 

4. Bleed-off system pressure 

27 
5. Remove pump housing 

6. Replace failed components 

7. Reinstall housing 

8. Remove locks and open valves 

9. Restart 

The team struggled with identifying the steps in this process and it became clear there were 

multiple methods being used to secure the valves and drain the pressure from the pump systems. 

Once there was general agreement on the steps in the process, discussions on the hazards 

associated with steps 1 through 4 were initiated. However, a continued lack of consensus 

concerning proper procedures to control the hazards in these steps limited progress within the 

allotted time. The team recognized the repair process as an elevated risk activity because of its 

high likelihood of occurrence. The team also agreed that the mine should develop an SOP for 

this reoccurring activity or investigate alternative equipment that would not require such frequent 

repairs. Despite this recognition, the team did not feel empowered to effect this change without 

further approval from management. 

5.1.5 - Discuss Implementation, Monitoring and Auditing Issues: 

The overall acceptance and understanding of the risk assessment process by the team at this mine 

was limited. The team selected was energetic and eager to learn the subject but had limited 

exposure to risk assessment practices and as such does not utilize low level risk assessment tools, 

such as JSAs or SOPs, in their mining processes. 

The management team at Mine A was short on staff and expressed a reluctance to take on 

additional administrative burdens associated with the MHRA process. The limited time 

available for the MHRA exercise was largely due to existing workload obstacles. This is a new 

mining operation with a relatively high turnover rate where site-specific experience is in 

relatively short supply. In its current state, it is difficult to see how management could supply 

the necessary guidance to implement, monitor and audit a formal risk management approach 

such as an MHRA. 

Lastly, it was not clear that labor and management were communicating at a level necessary to 

foster the exchange of ideas in a frank and productive fashion required for an MHRA. While 

there was a cordial labor-management relationship and communication was good for day-to-day 

operational issues, there seemed to be a rigid separation between labor and management in the 

strategic decision-making processes. Future involvement of the workforce in development of 

JSAs and SOPs may help to improve this relationship and better position the mine for effective 

major hazard management planning. 

28 
5.2 – Unplanned Detonation of a Production Blast Risk Assessment Case Study 

Mine B is an underground limestone mine using the room-and-pillar mining method. Rooms are 

typically 35 ft wide by 20 ft high. The production faces are drilled with a V-cut pattern 13 ft 

deep and filled with ANFO. Blasting caps and primers are inserted into each hole and connected 

to a specific timing delay. Typically the faces are drilled and loaded early in the shift. Faces 

prepared in this manner are barricaded and ready to connect to the blasters via prima cord at the 

shift’s end. Leaving the face fully charged represents a hazard for miners working near these 

areas. 

A team of company and external personnel took part in a systematic discussion about the 

explosives hazards. The team focused on work processes associated with blast hole loading and 

detonation and specific products used in the blasting process. The cooperating company 

identified the unplanned detonation hazard after attending the previously discussed NIOSH 

sponsored workshop on Minerals Industry Risk Management. 

5.2.1 - Risk Assessment Scope 

The objective of the risk assessment was to 1) review hazards associated with unplanned 

blasthole detonations prior to scheduled face shots at Mine B, and 2) evaluate strategies and 

techniques to mitigate the risk. 

5.2.2 - Risk Assessment Team 

The team was made up of persons employed at the mine, technical representatives of the local 

explosives supplier, and an observer and facilitator. More specifically, the team members 

included: 

Two management representatives 

One engineer 

 One miner 

One underground mine foreman 

Two external explosives experts 

 NIOSH observer 

Facilitator – MISHC (University of Queensland) 

5.2.3 – Risk Assessment 

A formal risk assessment method was not completed, nor was it needed to solve the unplanned 

detonation events. The risk assessment was largely accomplished through focused discussions of 

the hazards and potential controls. The entire process took approximately 2 hours. For the 

purposes of this analysis, the various discussion segments were placed into the steps associated 

with the MHRA process (see below). 

5.2.3.1 – Step 1, Identify and Characterize Unplanned Detonation Mining Hazards 

The primary safety risk identified was the unplanned detonation of a production face while 

29 
 

mining personnel were present. The risks were the greatest when the blast holes were loaded 

with explosives and all the blasting caps were connected together. The risks were increased by 

the length of time the face sat in this condition. At this mine site, that length of time ranged from 

4 to 6 hours. The team agreed that the risks could be significantly reduced if the length of time 

between setting up the face for a blast and actually blasting the face was shortened. 

The discussions began with a representative of the mining operation describing the work 

processes used in setting up a development face for a production blast. This was followed by a 

technical presentation from representatives of the explosive manufacturer. The focus of this 

discussion was on the products used in the blasting process. 

5.2.3.2 – Step 2, Rank Potential Unwanted Events 

Numerous potential threats were identified capable of causing a spontaneous ignition event: 

1.	 Lightning strike on the surface above the underground mine – Understandably, blasts are 

not attempted in surface operations when lightning occurs. However, in underground 

mines, blasting procedures are not generally altered when lightning exists on the surface. 

Recently, unplanned detonations have occurred when lightning strikes were observed 

near the blasting area (Anon, 2005). Also, the association of lightning with the Sago 

Mine Disaster in January, 2006 (Gates et al., 2007), has provided a potential example 

where electrical currents may pass deep within the earth’s strata in conjunction with 

surface lightning strikes. At Mine B, there were no procedures that altered the blasting 

practices during weather that produced lightning strikes. 

2.	 Rock fall hitting base charge detonator and the strike initiates an electric spark – A rock 

falling from the mine’s roof and directly impacting a base charge detonator could initiate 

an electric spark and cause an unwanted detonation of the explosives. At Mine B, 

precautions are taken to remove all loose material from the roof prior to loading the blast 

holes. Both mechanical and hand-scaling techniques are used. 

3.	 Shovel or other tools impacting the detonator – This is a similar problem to the roof 

rocks hitting the base charge detonator. The potential for this type of impact detonation 

was considered to be very low. 

4.	 Static electric charge - Most electric detonators have protective systems built in at the 

manufacturing stage to eliminate unplanned detonations. However, when static electricity 

is known to be a severe problem, such as in dry or dusty conditions, then particular care 

is needed to prevent an accidental discharge to a circuit. Sometimes mining operations 

require the miner to wear conducting footwear as a precaution. No special gear was worn 

at the Mine B site. 

5.	 Snap and shoot – Several accidents have occurred in the last fifteen years related to snap 

and shoot4

. 

4

 Snap and shoot is sometimes also called stretch and shoot; snap, slap and shoot; or whip, snap and shoot. 

30 

Holmberg and Salomonsson (2002) identified five accidents in which a 

shock tube might have been unintentionally stretched to breakage. It was believed that in 

some instances this caused the tubes to initiate. For example, if a vehicle ran over a blast 

hole with a shock tube, it is possible that the tube could be entangled in the vehicle and 

be caused to snap and shoot. 

The snap and shoot threat was considered to be the most likely scenario for an ignition of a 
face loaded with explosives at the Mine B site. Although the other four threats were all 

potentially possible, the team felt there were sufficient barriers and controls currently in place 

to minimize their likelihood. Therefore, the focus of the team was to examine what might be 

done to reduce the snap and shot threat. 

5.2.3.3 – Step 3, Determine Important Existing Prevention Controls and Recovery Measures 

The existing work process associated with the snap and shot threat was to: 

1.	 Place the blast caps and ANFO into the blast holes early in the shift 

2.	 Tie the blasting caps and shock cord (Figure 11) in place early in the shift, and 

3.	 Connect these items to the detonation system at the end of the shift, just prior to blasting. 

The time between 2 and 3 was between 4 and 6 hours. During that time, there existed an 

opportunity for an unplanned detonation through the snap and shoot mechanism. 

Figure 11 - Photograph of shock cords similar to the ones used at the study site. 

5.2.3.4 - Step 4, Identify New Prevention Controls and Recovery Measures 

The team discussed two options to reduce the risk for snap and shoot: 

1.	 Use the current work procedure to load and blast the face and attempt to decrease the 

likelihood of unplanned detonation through new prevention controls and recovery 

measures. 

2.	 Change the work procedure to tie on the caps just before the blast, thereby eliminating the 

threat of premature ignition (EH). 

As the team discussed the hazard in more detail, it became apparent that a formal risk analysis 

technique was not needed to identify an appropriate safety solution. The team agreed to 

recommend altering work procedures so that final blast set-ups were done at the end of shift 

(option 2). In many ways this process followed an informal fault tree analysis where the process 

was altered to eliminate paths to the top event. 

31 
5.2.3.5 – Step 5, Discuss Implementation, Monitoring and Auditing Issues 

Finally, the changed steps were reviewed to identify any new risks. No significant new risks 

were identified so the team agreed to recommend that the procedure be changed. The entire 

process took less than 2 hours to complete. 

The team made a single effective recommendation, as follows: 

The blast caps should not be snapped in place when the face is loaded and tied in early in 

the shift. During the morning blast setup work, the blast caps should be located near the 

face but at least 2 feet from the setup. The shot firer should return at the end of shift, 

when he normally inspects the blast setup, and tie-in the caps at that point. The shot firer 

should subsequently inspect the set-up and, if appropriate, proceed with the usual final 

blast setup and detonation. This recommendation should be part of a Standard Operating 

Procedure for connecting the detonation systems to loaded blast holes at this operation. 

This case study did not apply a formal risk assessment method but rather undertook a structured 

discussion of the hazard. In this case study, new controls were not needed since altering the 

work procedure eliminated the hazard and hence the risk. This informal risk assessment process 

appeared to be an effective and valued process by the team members. 

32 
5.3 – Spontaneous Combustion Causing Fire/Explosion Risk Assessment Case Study 

Mine C is a deep longwall coal mine with the potential for spontaneous combustion. The mine 

uses a bleederless ventilation system in its longwall panels to help reduce the potential for 

spontaneous combustion. Spontaneous combustion can occur in coalbeds with physical and 

chemical characteristics that allow the coal to oxidize at relatively low temperatures. This can 

set into motion a chain of events where additional oxidation causes temperatures to rise to a point 

where a flame will occur. A primary ingredient for this reaction is oxygen. If oxygen is not 

present, the oxidation process cannot occur. Bleederless ventilation systems have been 

extensively used in many parts of the world as a spontaneous combustion control measure (Smith 

et al., 1994). These systems are designed to reduce oxygen contents in areas where the coal has 

been extracted through isolation from a mine’s ventilation system. Smith et al. (1994) reported 

the two areas that provided the most risk for spontaneous combustion are those around the seals 

and directly behind the longwall shield supports. MSHA’s regulations covering bleederless 

ventilation systems are found in Federal Code of Regulations under Part 30, Section 75.334 (f). 

The bleederless ventilation system at Mine C uses seals at gate entry cross-cuts to separate 

ventilating air from the gob. The mine’s greatest concern is the potential for spontaneous 

combustion in the gob area behind the active longwall face. A risk assessment was performed to 

investigate major hazard potentials and evaluate controls to mitigate the potential for a 

spontaneous combustion event. 

5.3.1 - Risk Assessment Scope 

The scope of the risk assessment was originally designed to utilize a WRAC to review the 

hazards and a BTA to identify existing and new prevention controls and recovery measures from 

the spontaneous combustion hazard. Mine management did not attend a NIOSH-sponsored 

MHRA training course prior to the site study. At the start of the Risk Assessment, the team was 

briefed on risk management principles. Reference materials on sources of spontaneous 

combustion were used to provide a detailed list of relevant energies in need of control. 

Unfortunately, the risk assessment was limited to a single day. 

5.3.2 - Risk Assessment Team 

The team consisted of mine site personnel directly involved in monitoring and responding to a 

spontaneous combustion event, a NIOSH observer, and a facilitator from MISHC. One member 

of the general workforce was represented on the risk assessment team. Team members were as 

follows: 

Mine operations manager 

Technical services manager 

General mine foreman 

Safety manager (partial) 

Fireboss (labor) 

NIOSH observer 

Facilitator – MISHC (University of Queensland) 

33 
5.3.3 - Risk Assessment 

MSHA statistics show that spontaneous combustion accounted for 17% of the ignition sources 

for the 87 reportable fires occurring at underground coal mines between 1990 and 2000. The 

potential for the spontaneous combustion hazard increasing the risk of fire and explosion was a 

primary concern at the case study mine. In the past, the mine has routinely sealed gob areas. No 

reportable fires have occurred at the mine according the MSHA database. However, 

spontaneous combustion events have occurred at nearby mines operating in the same seam. 

Currently, Mine C uses a modified “U” ventilation system where the air is brought up the 

headgate entries, across the face, and down the tailgate entry (Figure 12). In the future, the 

operator is planning to change the manner in which the gob will be sealed. The plan is to 

temporarily retain bleeder headings around the gobs while development continues inby the panel. 

As a result of this change and the historical occurrence of this hazard in adjacent mines, the mine 

decided to examine risks related to spontaneous combustion in the active panel gob. 

Figure 12 - Bleederless ventilation system used at the study mine to control spontaneous 

combustion. 

Following a briefing on the principles of risk management and the tools to be used, the facilitator 

led the team through a structured process involving the following steps: 

34 
 

 

 

1.	 Recognizing and characterizing hazards 

2.	 Selecting top unwanted events (informal risk ranking) 

3.	 Identifying existing prevention controls and recovery measures with the BTA (partial list) 

4.	 Identifying new prevention controls and recovery measure ideas with the BTA (partial 

list) 

5.	 Implementation, monitoring and auditing issues. 

Because of the time constraints, it was not possible to formally risk rank the top unwanted events 

or to fully develop the list of existing or new prevention controls and recovery measures. 

5.3.3.1 – Step 1, Identify and Characterize Spontaneous Combustion Hazards in the Active Panel 

Gob 

Spontaneous combustion hazards within current and planned longwall panels are influenced by 

potential heat sources and conditions of the atmosphere in the gob (Table 16). The type of heat 

sources in or near the gob in Mine C included oxidation of the broken coal, hot works in the gate 

entries or along the longwall face, sparks from roof bolts failing as the strata collapsed in the 

gob, and heating of an overlying coalbed from an igneous intrusion. Conditions of the 

atmosphere in the gob needed to cause a fire or an explosion include availability of oxygen from 

the longwall face ventilation and hydrocarbons from the mined coalbed or from the overlying 

sandstone and coalbed. 

Table 16 – Potential heat sources and conditions of the atmosphere in the gob needed to cause a 

fire or an explosion. 

Heat Sources Gob Atmospheres 

Coal oxidation (spontaneous combustion) Oxygen available from face ventilation 

Welding/cutting (hot works) Hydrocarbon liberation from coal 

Roof bolt sparks during gob caving Gas migration from sandstone main roof 

Heat in upper coal due to igneous intrusions Gas migration from the upper coalbed as caving occurs 

5.3.3.2 – Step 2, Rank Potential Unwanted Events 

Time constraints prohibited the risk assessment team from a thorough discussion of all potential 

unwanted events that could lead to a fire or explosion. The team identified three main categories 

of events that could potentially produce spontaneous combustion in the gob of an active longwall 

panel: 

1.	 Air (oxygen) flow into the gob through 

a.	 Headings / cross-cuts (including barometric pressure change effects) 

b.	 Gob boreholes 

c.	 Longwall shield supports 

d.	 Leaky seals 

2.	 Methane / hydrocarbon buildup in the gob to ignitable levels (5 to 15 %) through 

a.	 Gas migration from overlying coalbed into gob 

b.	 Gas migration from overlying sandstone into gob 

3.	 Heat source in gob where broken coal in gob from caving upper seam increases oxidation 

rates 

35 
 

 

 

 

 

 

 

 

 

 

The team selected these unwanted events based on the degree to which the most workers might 

be exposed and on the historical information concerning past spontaneous combustion episodes. 

In the absence of any formal risk ranking method such as the WRAC or the PHA, the risk 

assessment team informally agreed that all unwanted events were of high consequence to the 

mining operation. 

5.3.3.3 – Step 3, Determine Important Existing Prevention Controls and Recovery Measures 

A BTA was performed on only the four events under the air flow into the gob category due to 

time limitations. The risk assessment team discussed potential connections between the hazards 

listed in Table 16 and the mining operations. The team then went on to identify 17 existing 

prevention controls (Table 17). 

Table 17 - Existing key prevention controls for the spontaneous combustion risk assessment. 

TOP EVENT => Air (Oxygen) Flow into the Gob 

Through headings / 

cross-cuts (including 

barometric pressure 

change effects) 

PC1 Forced Air Ventilation that causes positive pressure on gob (MH) 

PC2 High-quality seal design with ring grouting to improve seal effectiveness and 

reduce roof-to-floor convergence (PB) 

PC3 Location of seals to avoid leakage pathways (MH) 

PC4 Seals checked and maintained by fire boss weekly (P) 

PC5 Monitoring pressure balance across seals weekly (WD) 

PC6 Atmosphere behind seals tested weekly, gas tested by experienced person (WD) 

PC7 Gob vent borehole gasses tested weekly, gas tested by experienced person (WD) 

Through gob boreholes 

(including barometric 

pressure effects) 

PC8 Forced air ventilation causes vent holes to only breathe out (MH) 

PC9 Gob hole is sealed when panel is complete and sealed (PB) 

PC10 Gob holes can be shut in if oxygen >10% (P) 

PC11 Check valve & flame arrestors assure no flow down holes into the gob (MH) 

Through longwall 

shield supports 

PC12 Curtains on shields at start up (PB) 

PC13 Monitoring of gob to verify it is tight (P) 

PC14 Real time gas monitoring at tailgate to detect heating (WD) 

PC15 Seals installed in gates to reduce flow into gob area from gates (MH) 

Through leaky seals PC16 Seals tested weekly with smoke tube and repaired as needed (P) 

PC17 Flexible foam packs used for construction and repair (MH) 

As above: see PC2 

TOP EVENT => Methane / hydrocarbon build up in the gob to ignitable levels (5 to 15 %) 

Gas migration from overlying 

coalbed into gob 

Not addressed due to time constraints 

Gas migration from overlying 

sandstone into gob 

Not addressed due to time constraints 

TOP EVENT => Heat source in gob 

Broken coal in gob from caving 

upper seam increasing 

oxidation rates 

Not addressed due to time constraints 

PC – Prevention Controls 

MH – Minimize Hazard 

PB – Physical Barrier 

WD – Warning Devices 

P – Procedures 

PST – Personnel Skills and Training 

The 17 prevention controls were distributed between the minimize hazards (MH), physical 

36 
 

 

 

 

 

barriers (PB), warning devices (WD), and procedures (P) control categories (Figure 13). 

Eliminating the hazard (EH) could only be done by not mining the coalbed with conventional 

mining techniques, since this coal is prone to spontaneous combustion. Many of the controls 

were required by MSHA regulations while others were considered to be Best Practice at this 

mine site. 

0 

1 

2 

3 

4 

5 

6 

7 

Number 

EH MH PB WD P PST 

Prevention Controls Recovery measures New Ideas 

Figure 13 - Distribution of prevention controls and recovery measures for the spontaneous 

combustion causing fire/explosion risk assessments. 

The team identified 11 recovery measures designed to mitigate the consequence of a spontaneous 

combustion event (Table 18). Discussions concentrated on monitoring and initial evacuation 

responses (Table 18). These existing recovery measures are mostly aimed at complying with 

MSHA standards and regulations for coal mines with spontaneous combustion hazards. Many 

should be documented in the mine’s ventilation plan. A common theme of the discussions of 

these controls was the dependence on a few individuals to ensure compliance, where 72% of the 

recovery measures (Figure 13) were either warning devices (WD) or procedures (P). Formal 

auditing methods were not always used for critical controls. The mine management at Mine C 

has experience in reacting to heating events and seems to rely on leadership skills rather than 

formal procedures for directing response. 

Table 18 – Existing key recovery measures for the spontaneous combustion risk assessment. 

Early Detection 

Advancing 

spontaneous 

combustion in the 

gob 

RM1 Weekly bag sampling at seals every 1000 ft along seal line/perimeter (WD) 

RM2 An on-site Gas Chromatograph with backup at other mines in the valley (WD) 

RM3 Written Action Levels/Trigger Points; (WD) 

 Level 1: >5ppm H2 AND >100 ppm CO triggers 

 If O2 > 5% resample ASAP 

 If O2 <5% resample within 24 hrs 

Level 2: >5ppm H2 AND >100 ppm CO on resample triggers

 If O2 > 10% resample every 4 hrs 

 If O2 <10% resample within 8 hrs 

Level 3: >5% H2 OR >350 ppm CO OR rising CO/CO2 ratio

 AND if O2>10% resample every 3 hrs and notify MSHA 

37 
 

 

 

Level 4: >1500 ppm CO OR HC>4% AND O2>10% then

 evacuate all non-essential persons from mine and call MSHA 

Fire detected in 

the gob and initial 

response 

(communicate gob 

fire to miners and 

specify the correct 

egress path) 

RM4 Mine dispatch and shift foreman are instructed to evacuate mine by phone (P) 

RM5 Alarms at belt feeders and mine pager system that indicate need to egress in both this 

mine and the overlying seam (WD) 

RM6 Persons entering remote areas are required to notify dispatch prior to entering. 

Dispatch keeps written record of personnel locations and entry/exit time (P) 

RM7 Shift foreman aware of persons assigned to tasks in remote areas (P) 

Evacuation 

Rapid egress from 

the mine required 

RM8 Regular Emergency Response training of all underground personnel (PST) 

RM9 Live training to practice egress during likely event scenarios (PST) 

Explosion Prevention 

Fire event 

escalates to 

explosion 

RM10 Rock dusting of mine exceeds minimum standards (MH) 

RM11 Pre-framing of fire seals across longwall gate roads and staging of materials nearby 

for rapid sealing of involved area (P) 

RM – Recovery Measures 

MH – Minimize Hazard 

PB – Physical Barrier 

WD – Warning Devices 

P – Procedures 

PST – Personnel Skills and Training 

5.3.3.4 - Step 4, Identify New Prevention Controls and Recovery Measures 

As part of the BTA, new prevention control and recovery measure ideas were identified by the 

team. However, the limited time available with the mine staff and the need to begin the process 

with basic training in the risk management process limited the extent to which the exercise could 

be completed. The team identified one new prevention control and two new recovery measure 

ideas (Table 19). Mine management agreed to review these new ideas and decide if they should 

be implemented. 

Table 19 - New ideas for mitigating risk of spontaneous combustion. 

Prevention Controls 

NI1 Improve rock dusting of gob perimeter such as bottom dusting (PB) 

Recovery Measures 

NI2 Investigate stench gas or other methods of increasing the likelihood that personnel in remote areas get the 

message to egress (WD) 

NI3 Develop a detailed vendor list for materials, equipment and expertise for use in a spontaneous combustion 

emergency response (P) 

NI – New Ideas 

PB – Physical Barrier 

WD – Warning Devices 

P – Procedures 

5.3.3.5 – Step 5, Discussion of Implementation, Monitoring and Auditing Issues 

The team identified 17 existing controls for prevention of spontaneous combustion in the gob; 

most (8) can be considered engineering controls (MH and PB), 4 are manual monitoring controls 

(WD), and 5 are process controls. The 6 response measures are primarily administrative (P and 

PST) with 4 manual monitoring (WD) and one engineering control (MH). 

38 
Influencing the number and type of controls identified is the mine’s general avoidance of formal 

procedures other than those mandated by regulations. Mine management expressed a preference 

for flexibility in actions taken based on information collected through the multiple manual 

monitoring controls and the experience of the staff. 

The overall acceptance and understanding of the risk assessment process by the team at Mine C 

was limited. The team selected was energetic and knowledgeable in the subject hazard but had 

limited exposure to risk assessment practices. The mine does not utilize informal risk 

assessment tools such as JSAs or SOPs in its mining processes. The management team at this 

mine carries multiple responsibilities and expressed a reluctance to take on more administrative 

burdens. This existing workload obstacle was evident in the limited time available for the 

exercise. 

One issue with implementing the risk management principles is the willingness of the team to 

rely on manual monitoring of the hazard and to defer most actions to the judgment of a few staff 

members. While these experienced staff members would likely act appropriately in monitoring 

for hazards, this system exposes the mine to delays should events begin when key staff are not 

accessible. 

One other aspect of risk management not completely addressed by the team was that the formal 

response plans end with evacuation of the mine and notification of MSHA. While it was clear 

that the mine would indeed take actions to combat the fire and recover the mine, these response 

plans would be developed by key staff spontaneously in reaction to unfolding events. In these 

respects the outcomes of this exercise may be the product of a cultural acceptance of relatively 

high levels of risk at Mine C. 

39 
5.4 – Underground Workshop Fire Risk Assessment Case Study 

Mine D is a large longwall coal mine with over 600 salaried and hourly employees. The mine 

has an underground workshop located close to the bottom of the intake shaft (Figure 14). The 

workshop is basically a heading containing a pit large enough to allow maintenance work under 

a locomotive. Other workshop-related tasks are also performed in the immediate area such as 

battery charging. An underground workshop fire is considered to be a major hazard since it 

could potentially disrupt normal escapeway egress routes via the intake air shaft. 

Track haulage Intake 

Shaft 

VentilationVentilation 

stoppings
 Maintenance Pit 

Figure 14 - Map showing the location of the maintenance pit with respect to track haulage, 

ventilation stoppings, and intake shaft. 

The risk assessment project theme was identified at the NIOSH-sponsored workshop on Minerals 

Industry Risk Management and further developed through discussion between management 

personnel and NIOSH representatives. 

5.4.1 - Risk Assessment Scope 

The objective of this risk assessment was to 1) review fire hazards in the underground workshop 

located close to the mine’s intake shaft, and 2) evaluate strategies and techniques to mitigate the 

risks. 

5.4.2 - Risk Assessment Team 

The team was made up of persons employed at the mine and by the mine’s parent company, two 

external fire prevention experts, a NIOSH observer, and a facilitator from MISHC. More 

40 
specifically, the team members included the following: 

Four representatives from the company’s safety program 

A general maintenance mine foreman 

A continuous improvement coordinator 

A fire brigade supervisor 

Two external fire prevention experts (NIOSH / Insurance Company) 

NIOSH observer 

Facilitator – MISHC (University of Queensland) 

5.4.3 – Risk Assessment 

The Risk Assessment involved facilitation of a team of personnel through a structured process of 

the following steps: 

1. Hazard descriptions 

2. Preliminary Hazard Analysis (PHA) method introduction and risk ranking 

3. Potential unwanted event identification using PHA 

4. Bow Tie Analysis (BTA) method introduction 

5. Causes and prevention controls discussion using BTA 

6. Consequences and loss reduction controls discussion using BTA 

7. Repeat of Steps 5 and 6 for all high ranked potential unwanted events identified in Step 3. 

5.4.3.1 – Step 1, Identify and Characterize Fire Hazards in the Underground Workshop at the 

Bottom of the Intake Shaft 

The first step in the risk assessment involved identifying and understanding the hazards related to 

a fire in the underground workshop. The team brainstormed the potential heat and fuel sources 

that might be either available in the workshop or related to the maintenance functions performed 

in the workshop (Table 20). 

Table 20 - Fire hazards consisting of potential heat and fuel sources. 

Heat Sources Fuel sources 

Electrical power Oils/grease 

Welding/cutting (hot works) Paper/trash 

Grinding Coal 

Portable heaters Diesel fuel 

Batteries Solvents 

Hot engines/surfaces Plastic 

Exhaust/DPM Wood 

Spontaneous Combustion from oily rags Hoses 

Compressors Acetylene 

 Hydrogen (batteries) 

After discussing the above hazards, the team used its knowledge of the underground workshop 

design and operation to undertake a Preliminary Hazard Analysis (PHA). The PHA identified a 

list of fire-related hazards within and near the maintenance area and then prioritized these 

hazards through a risk ranking process. 

41 
 

 

 

 

 

5.4.3.2 – Step 2, Rank Potential Unwanted Events 

The risk assessment team identified 24 potential incidents/accidents related to an underground 

workshop fire (Table 21). The PHA risk analysis tool was selected to risk rank the potential 

incidents/accidents. A discussion of the PHA technique can be found in Section 3.2.2. 

Table 21 - Preliminary Hazard Assessment (PHA) form for the underground workshop fire risk 

assessment case study. 

Potential incident/accident Exposure 

(Table 6) 

Overall 

Likelihood 

(Table 7) 

Max. 

Reasonable 

Consequence 

(Table 3) 

Most Likely 

Consequence 

(Table 8) 

Risk 

Rank 

(Table 

9) 

1 Pressurized/atomized hydraulic oil from 

equipment sprays on heat source causing fire 

A B B B 5 

2 Short circuit in battery cells leads to fire D C B B 8 

3 Fire in garbage storage A C C B 8 

4 Exhaust DPM filter fire when filter withdrawn 

from engine 

B B D C 9 

5 Hydrogen explosion during repairs leads to 

fire 

E E D A 11 

6 Auto battery fault when charging leads to 

fire/explosion 

D D D B 12 

7 Spontaneous from oil rags/trash A C D C 13 

8 Overheated compressor B C D C 13 

9 Welding methods cause fire D C C C 13 

10 Hot slag contacts combustible leads to fire C C C C 13 

11 New rescuers ignites when hit by/run over in a 

workshop 

A D B C 17 

12 Short circuit/fault on diesel equipment A D C C 17 

13 Diesel equipment overheats A D C C 17 

14 Diesel fuel is vaporized by heat and ignited by 

fault/short 

A E B C 20 

15 Damaged and worn electrical equipment leads 

to fire 

D C D E 22 

16 Extension cord/wire run over/damaged leads 

to a fire 

D C E E 22 

17 Overheated brakes on equipment B D E E 24 

18 Broken light fault A D E E 24 

19 Grinding sparks lead to fire D D D E 24 

20 Heater fault/circuit B D E E 24 

21 O2 problem leads to more susceptible 

conditions for fire 

C D B E 24 

22 Transformer fault leads to fire A D E E 24 

23 Contaminants onto electric heaters B D E E 24 

24 Arch welding cable short/fault leads to a fire C D D E 24 

The team decided to focus on the top four ranked risks from the PHA analysis. These potential 

incidents/accidents are: 

1. Pressurized/atomized hydraulic oil from equipment sprays on heat source causing fire 

2. Short circuit in battery cell leads to fire 

3. Fire in garbage storage 

4. Exhaust DPM filter fire when filter withdrawn from engine. 

42 
 

 

 

 

 

 

In addition, once the team began to discuss existing prevention controls and recovery measures, a 

decision was made to add another potential incident/accident: 

5. Pool of oil from a failed pump ignites in the maintenance pit and leads to a mine fire. 

5.4.3.3 – Step 3, Determine Important Existing Prevention Controls and Recovery Measures 

A BTA was performed on each of the four top ranked risks from the PHA with one additional 

risk added after the PHA by the team. For many of the top ranked incidents, multiple potential 

causes were possible. For example, the pressurized/atomized hydraulic oil from equipment 

sprays on heat source incident contained seven different potential causes: 

1.	 Worn hydraulic hose or coupler failure and pressure release 

2.	 Hot work damages hose 

3.	 Unknowing removal of the hose under pressure (towed in or running) 

4.	 Hose pinched during installation or wrong hose installed on equipment and pressure 

release 

5.	 Poor hose location exposes failures to heat sources on the equipment 

6.	 Overheated brakes ignite oil spray 

7.	 Lights fault when oil sprays and fire starts. 

In all, 14 unique, potential causes were identified and a BTA was performed on each. These 14 

causes occupied the top event circle of the BTA (Figure 8). From the 14 BTAs, 34 existing 

prevention controls were identified (Table 22). 

Table 22 – Existing key prevention controls for the underground workshop fire risk assessment. 

TOP EVENT => Hydraulic oil leak/spray and ignites 

1. Worn hydraulic hose 

or coupler failure and 

pressure release 

PC1 Hydraulic hose and couplings are designed to Standard (MH) 

PC2 Hoses are to be run away from hot areas or a barrier is located between hoses 

and hot spots (PB) 

PC3 The mine has a standard for 4 braided hoses and fittings that is currently being 

put in place (P) 

PC4 There is a specification on preventive maintenance program done on 

equipment that checks hoses and couplings (P) 

PC5 Inspections of equipment are done before work that looks for damaged or 

badly located or worn hoses (PST) 

PC6 When locomotive is shut down, the hydraulic pressure bleeds from the system 

(MH) 

PC7 Gage in the cab indicates pressure in hydraulics (WD) 

2. Hot works damages 

hose 

PC8 Procedures exist to do welding and cutting work in the workshop (P) 

PC9 Welding and cutting is not done on running (hydraulics are pressurized) 

equipment (P) 

PC10 In the rare case where welding and cutting works are done in proximity to 

hydraulic, the hydraulic lines are shielded (PB) 

PC11 Area of hot work and equipment is cooled by water hose after welding (P) 

3. Unknowing removal 

of the hose under 

pressure (towed in or 

running) 

PC12 Person should shut down and verify no hydraulic pressure before working on 

equipment (PST) 

PC13 Even if equipment is shut down, persons should check pressure gage before 

working on equipment (PST) 

PC14 Should be tag/note left on equipment if it has a problem (e.g. Needed to be 

towed in/pressurized) (WD) 

43 
 

 

 

 

 

 

 

 

PC15 Completed work is recorded on Work Orders (P) 

4. Hose pinched during 

installation or wrong 

hose installed on 

equipment and pressure 

release 

PC16 Persons clean and inspect work after completion to identify issues such as 

pinched/damaged hoses (PST) 

PC17 Mine hose sizes are standardized (MH) 

PC18 Mine also gives standard specification for hose lengths to minimize the 

numbers of hose lengths (MH) 

PC19 Hoses are available in workshop or warehouse (P) 

PC20 There is a follow-up process to address the need for an incorrect (too long) 

hose with Work Order (P) 

5. Poor hose location 

exposes failures to heat 

sources on equipment 

As Above: See PC2 to PC5 

6. Overheated brakes 

ignite oil spray 

PC21 If brakes are locked, then machine is not dragged to workshop (P) 

PC22 If partial brake fails (not locked), then machine is not dragged to workshop (P) 

7. Lights fault when oil 

sprays and fire starts 

PC23 Pit lights are designed to reduce hot surface/oil ignition exposure (MH) 

TOP EVENT => Short circuit in battery cell leads to fire 

8. Dirty battery, battery 

fatigue, low water 

PC24 Weekly inspection of equipment, check batteries and clean if required (P) 

PC25 Battery is also inspected by bottom attendants (P) 

PC26 Battery is also inspected in workshop before or after work and cleaned if 

required (P) 

9. Battery age PC27 Batteries are dated and replaced if date and cell status indicates (P) 

10. Improper charging PC28 Operators park and charge loco batteries in station (P) 

PC29 Battery attendees and mechanics also put locos at stations to charge (P) 

PC30 Battery should be fully charge and cooled for 8 hours (P) 

TOP EVENT => Fire in garbage storage 

11. Spontaneous 

combustion in garbage 

storage 

PC31 Garbage is changed out every 5 days at least (P) 

PC32 Hot items (>302 F) do not go into garbage (P) 

PC33 Items are put into garbage in bags (PB) 

TOP EVENT => Exhaust DPM filter fire when withdraw from engine 

12. Hot materials enter 

DPM from catalyst, etc. 

PC34 Reduce excess idling to lower hot materials entering DPM from catalyst (P) 

TOP EVENT => Pool of oil from a failed pump ignites in the maintenance pit and leads to a fire 

13. Oil pump fails due to damage 

or seal failure 

No current controls 

14. Welding/cutting near pit 

ignites oil pool in pit 

No current controls 

PC – Prevention Controls 

MH – Minimize Hazard 

PB – Physical Barrier 

WD – Warning Devices 

P – Procedures 

PST – Personnel Skills and Training 

Based on the analysis that was done by the team, existing controls can be placed into one of the 

six categories described in Section 4.4. Twenty-seven percent of the key existing prevention 

controls (Figure 15) involve the design of equipment, i.e. minimize hazards (MH) and physical 

barriers (PB). For example, hydraulic hose and couplings are designed to standards with hoses 

located away from hot surfaces or barriers placed between hoses and hot spots. The mine has 

standards for four braided hoses and the size and lengths of hoses. In addition, pit lighting 

systems are designed to reduce hot surfaces and lower ignition potential. The diesel particulate 

modules are designed to reduce hot material risks. 

44 
0 

2 

4 

6 

8 

10 

12 

14 

16 

18 

20 

Number 

EH MH PB WD P PST 

Prevention Controls Recovery measures New Ideas 

Figure 15 - Distribution of prevention controls and recovery measures for the underground 

workshop fire risk assessment. 

Six percent of the existing prevention controls were classified as warning devices (WD). For 

example, each locomotive cab has a hydraulic pressure gauge to help identify that all pressure is 

bled from the system prior to maintenance activity (PM7). Also, equipment needing repairs is 

tagged and the condition of the hydraulic system (pressurized) is noted (PM14). 

Sixty-eight percent of all existing prevention controls consist of procedures (P) and personnel 

skills and training (PST) that focused on maintenance and operational issues. Preventive 

maintenance checks are regularly done on hoses and couplings and on the location of hoses with 

respect to hot surfaces. Battery maintenance is also very important, with inspection and cleaning 

on a weekly basis. In addition, the shaft bottom attendant is required to inspect batteries on a 

regular basis. If equipment brakes are locked and cannot be released, the machine is hauled, not 

dragged, to the workshop. Each locomotive operator is required to inspect equipment prior to 

operation. They are trained to look for damaged, badly located or pinched hoses. They are also 

required to tag equipment if a problem is found. Maintenance personnel are required to shut 

down equipment and verify that no hydraulic pressure exists on the equipment prior to 

commencing work and to completing a work order. Batteries are replaced when their expiration 

date is reached. Locomotive operators park and charge batteries at designated stations and allow 

batteries to fully charge and cool for 8 hours. 

Welding/cutting/grinding (hot works) and housekeeping are recognized as extremely important 

key controls for preventing workshop fires. SOPs exist for hot works in the workshop area. Hot 

work areas are cooled with water and hot works are never attempted on running or pressurized 

equipment. Housekeeping issues centered on placing oily rags in sealed bags prior to placing the 

bags in garbage storage areas. Garbage is changed out at least every 5 days and hot surfaces 

(>300 ̊ F) do not go into garbage. 

Existing key recovery measures were also identified as part of the BTA. In the case of the 

underground workshop fire, the recovery measure was essentially the same for all 13 potential 

causes. Thirteen key recovery measures were identified for an underground workshop fire 

45 
 

 

 

(Table 23). The distribution of the control categories is shown in Figure 15. 

Table 23 - Existing key recovery measures for the underground workshop fire risk assessment. 

TOP EVENT => Fire in the workshop area, i.e., on the locomotive in garbage retainer, in the pit 

Fuel source comes in 

contact with heat source 

RM1 Persons will try to shut off equipment in cab locations to stop hydraulic fluid 

spray (note: when equipment is in operation there must be an operator in the 

cab) (PST) 

RM2 Persons would used hand-held, readily accessible fire extinguishers to fight fire 

(20 lbs) (PST) 

RM3 Persons are trained to use hand-held fire equipment every year including 

hands-on exercises (PST) 

RM4 Fire suppression on a machine can be manually and automatically activated 

(will also shut down machine) (MH) 

Small fire starts RM5 Notify surface clerk of fire (P) 

RM6 Live water hoses are available for use (MH) 

Fire persists or grows RM7 Surface clerk gathers information and notifies state/federal regulatory agencies 

and shift management (minimum 5 min to take action) (P) 

RM8 Workshop has fire sprinklers activated by overhead fire sensors (MH) 

RM9 Mine has an underground and surface fire brigade (PST) 

RM10 Other fire fighting equipment is also located atop of shaft, as well as 8-10 

headings away (P) 

RM11 There are W65 CO units and SCSRs on the mobile equipment and at 

designated locations near the workshop to aid in emergency egress (PB) 

RM12 Firefighters have PS5100 and PA100, etc., to fight large fire (MH) 

Fire develops into major 

fire requiring 

emergency egress 

RM13 A major fire in the mine requires mine evacuation and the shift foreman will 

decide on the evacuation route considering fire location (P) 

RM – Recovery Measures 

MH – Minimize Hazard 

PB – Physical Barrier 

WD – Warning Devices 

P – Procedures 

PST – Personnel Skills and Training 

The key components to the existing recovery measures are fire fighting and emergency egress 

from the mine. Hand-held fire extinguishers (20 lbs) are readily accessible on all equipment and 

within the workshop area (MH). Miners are trained to use hand-held fire equipment every year 

including hands-on exercises (PST). Most mobile equipment repaired in the workshop has 

automatic fire suppression capability (MH). The workshop has been fitted with a sprinkler 

system, activated by overhead fire sensors. Live water hoses are available for use in the 

workshop area. Additional fire fighting equipment is located at the top of the nearby intake 

shaft, as well as 8-10 cross-cuts from the workshop (MH). Large fires can be fought with 

PS5100, PA100, etc., fire fighting equipment. 

Workshop personnel are trained to immediately notify the surface clerk of fire (PST). The 

surface clerk gathers information, notifies shift management, and calls federal and state 

regulatory officials (minimum 5 min to take action). The mine has both an underground and 

surface fire brigade. If an emergency egress is necessary, miners are trained to don W65s and 

SCSRs and escape from the mine through primary or alternate escapeways (PST). 

46 
 

 

 

 

 

 

5.4.3.4 - Step 4, Identify New Prevention Controls and Recovery Measures 

As part of the BTA, 14 new prevention control and recovery measure ideas were identified by 

the team during the risk assessment to further reduce the workshop fire risks at the mine (Table 

24). Nine of the ideas are prevention controls and five are recovery measures. 

Table 24 - New ideas for an underground workshop fire risk assessment. 

New 

prevention 

control 

ideas 

NI1 Reinforce the need to shut down equipment and inspect equipment prior to welding and 

cutting (P) 

NI2 Reinforce need to shield hydraulic systems near the source if hot work must be done on 

operating equipment (P) 

NI3 Remove all heat sources from the area of equipment to avoid ignition of any hydraulic 

pressure leaks (P) 

NI4 Investigate ways of being more systematic and thorough about equipment repair needs and 

status before or when equipment is taken to the workshop (P) 

NI5 Use the behavior controls in this risk assessment to focus the Safety Behavior Observations 

(SBO) program/activities in workshop (PST) 

NI6 Reinforce need to ensure that lights and covers in pit are in good condition (P) 

NI7 Add pit inspection to fire boss’s job duties and consider inspection/monitoring by workshop 

personnel too. Make sure that these inspections examine for pooled oil in the pit. Add the 

requirement to inspect pit for pooled oil to pre-welding/cutting/grinding (any hot work) job 

preparation (P) 

NI8 Investigate modifying motors designed so they will not operate in low voltage (thereby they 

should be fully charged) (MH) 

NI9 Investigate changes that will allow battery removal and installing only fully charged 

batteries (MH) 

NI10 Investigate adding a 150-lb wheeled dry chemical fire extinguisher (MH) 

New 

recovery 

measure 

ideas 

NI11 Identify what the workshop personnel should do if hand-held fire extinguishers are not 

adequate (get other equipment or egress, breathing apparatuses, and include info in training) 

(PST) 

NI12 Decide whether doors in stoppings should be opened, allowing smoke into return (note that 

this would greatly increase airflow in workshop, note water line in return may be cut, note 

also idea to install water screen pipes in the return entry if doors are to be open) (PB) 

NI13 Consider the installation of a water source on the intake inside of the workshop (MH) 

NI14 Investigate getting a suitable foam system for pit to put out oil pool fire (MH) 

NI – New Ideas 

MH – Minimize Hazard 

PB – Physical Barrier 

WD – Warning Devices 

P – Procedures 

PST – Personnel Skills and Training 

The 14 new ideas can be divided into design, operating procedures and fire/emergency response 

issues. Two design ideas were identified. The team recommended that management investigate 

1) modifying motor designs so they will not operate at low-voltage (MH) and 2) modify chargers 

to prohibit battery removal without a full charge (MH). In both these situations, the low-voltage 

condition of the battery increases the likelihood of overheating which increases the potential for 

a fire. Both of these new ideas would limit the potential use of low-voltage batteries. 

Numerous new ideas were presented that focus on operating procedures. Two ideas focus on 

reinforcing the need to shut down equipment and inspect equipment prior to maintenance work 

and to ensure that lights and covers in the pit are in good condition (PST). Prior to working on 

47 
equipment, workers should remove all heat sources from the area to avoid ignition of any 

hydraulic pressure leaks. This could be accomplished with an SOP. The team also 

recommended that some kind of notification system be investigated to systematically identify the 

repair needs and their status before, or when, equipment is taken into the workshop (P). This 

could increase the workshop personnel’s awareness of potential hazardous conditions. The team 

also suggested that the fire boss and workshop personnel inspect the pit regularly for oil and 

other flammable materials (P). This inspection should also be done by the workshop personnel 

prior to hot work activity. Lastly, the team recommended that a Safety Behavior Observation 

(SBO) program/activity be initiated for the workshop (PST). The mine operator has personnel 

skilled in this approach. 

Several new ideas focused on emergency response issues. The team recommended that 

workshop personnel understand emergency response procedures and discuss specific fire 

scenarios during the training exercise. For example, workshop personnel should understand 

what impact opening the ventilation door in the return air stopping at the far end of the pit might 

have on a small fire (PB). This could be an issue since a water line is located in the return 

airway and might be useful in fighting a maintenance pit fire. Also, if hand-held extinguishers 

fail to put out a small fire, should workshop personnel obtain additional fire fighting equipment, 

don breathing apparatus, or evacuate the fire site and egress from the mine (PST)? The team also 

suggested that fire fighting capabilities (MH) in the maintenance pit be increased by adding one 

or more of the following items: 1) a 150-lb wheeled dry chemical fire extinguisher, 2) a portable 

foam generator, or 3) a water source on the intake side of the maintenance pit. 

5.4.3.5 – Step 5, Discuss Implementation, Monitoring and Auditing Issues 

The information provided in the risk assessment seemed accurate and the team functioned 

adequately, although the lack of participation from labor may have limited the team’s composite 

knowledge of the fire hazards in the maintenance pit. However, the addition of outside fire 

experts helped to bolster the team’s knowledge of fire prevention issues. The team had a strong 

focus on monitoring, administrative controls and training when identifying existing and new 

prevention controls and recovery measures (Figure 15). This will require the mine to vigilantly 

monitor and audit these controls. In this case study, the risk assessment did not recommend 

ways to eliminate the fire hazards from the workshop area. For example, was it possible to 

relocate the shop to an area that would effectively eliminate hazards? The exercise was 

successful in developing a range of new ideas that could produce quality barriers, controls and 

recovery measures that would further reduce the risk of a workshop fire. 

48 
5.5 – Water Inundation Risk Assessment Case Study 

Mines Ea and Eb are operating near an abandoned mine and adits that present a threat of 

inundation (Figure 16). The abandoned mine and adits are in the same seam and their workings 

are partially flooded. The abandoned mine flooded area is large with an estimated water head of 

approximately 30 ft at Mine Ea and 80 ft at Mine Eb. The abandoned mine was extracted using 

the room-and-pillar method, creating a significant water reservoir. The adits are to the east of 

Mine Eb and have two parallel entries, several hundred feet long and connected by cross-cuts. 

These potential water reservoirs are relatively small and may contain dangerous gases. 

All of these old mine workings are potentially filled with water and represent a significant 

hazard. Inundation hazards present risks for the mining operation. The mine has put into place 

many Best Practice controls to prevent an unwanted inundation event. The hazard is 

complicated by potential inaccuracies of existing abandoned mine maps and the lack of maps for 

the adits. 

Sealed

Sealed

Abandon Mine

Adits

Mine Ea

Mine-Eb

-

Sealed 

Sealed 

Abandon Mine 

Adits 

Mine-Ea 

Mine-Eb 

Figure 16 - Location of Mines Ea and Eb and adjacent water-filled abandoned mine and 

water/gas filled adits. 

The two mines are underground room-and-pillar coal mines with entries less than 48 inches high 

by 18 feet wide. These mines have been able to maintain a modest size footprint by periodically 

sealing mining sections as activity in the area ceases. Each mine employs approximately 35 

miners and operates a single auger type continuous mining machine. Current working faces are 

mostly located down-dip from the abandoned mine. The operator attended the NIOSHsponsored workshop on Minerals Industry Risk Management and identified the mine inundation 

hazard as the most significant risk. 

49 
5.5.1 - Risk Assessment Scope 

The objective of this risk assessment was to 1) identify hazards associated with the potential for 

an inundation at Mines Ea and Eb, 2) evaluate strategies and techniques to lessen the risk 

associated with an inundation, and 3) develop an action plan for new ideas. The mine operator 

was also interested in developing an inundation management plan. The mine has examined the 

possibility of pumping out all water from the abandoned mine but deemed it to be impractical 

due to the size of the water body. Elimination of the hazard was therefore not considered by the 

risk assessment team. Numerous controls, both required and in addition to MSHA regulations, 

are currently used at both mines. The mine was interested in examining additional controls to 

further lower the risk of inundation. 

5.5.2 - Risk Assessment Team 

The team was made up of persons employed at Mines Ea and Eb, as well as from the parent 

company and a NIOSH representative, as follows: 

 Two management representatives 

Two shift foremen 

One Miner 

One Engineer 

One Geologist 

NIOSH observer 

Facilitator – MISHC (University of Queensland) 

5.5.3 – Risk Assessment 

All five steps of the MHRA approach were followed and are discussed in detail below. 

5.5.3.1 – Step 1, Identify and Characterize Inundation Mining Hazards 

The first step in the risk assessment involved identifying potential inundation issues around the 

current and planned mining operations. Jobs (1987) identified seven inundation sources and the 

number of accidents associated with each source in British collieries during the period 1851 to 

1970: 

1. Contact with surface water – pond, river, canal or stream (9) 

2. Contact with surface unconsolidated deposits – glacial or organic (8) 

3. Strata water entering the mine workings (2) 

4. Shaft sinking (4) 

5. Clearing old shafts (14) 

6. Contact with abandoned old workings (162), and 

7. Failure of an underground dam, seal or leakage of a borehole (9). 

Significantly, 78% of the accidents were associated with contact with abandoned old workings. 

The team discussed the different sources of inundation and determined four potential hazards 

existing at Mines Ea and Eb: 

50 
1. Water from the up-dip abandoned mine, 

2. Water and gases from the adjacent adits, 

3. Water from surface creeks, and 

4. Water from surface drainage. 

Water from the abandoned mine is a potential hazard, with approximately 30 to 80 ft of water 

head. These flooded workings are in the same seam as Mines Ea and Eb and are generally at the 

same or higher elevations. There are also small adits open to the surface along the coal seam 

outcrop containing either water and/or gases typically found in old mine openings. These adits 

generally consist of two headings connected by cross-cuts and driven from the coalbed outcrop a 

few hundred feet into the hillside. The maximum adit water head is estimated to be 5 ft. There 

are no plans or maps in existence to help locate these entries in relation to Mine Eb. 

Surface creeks run over Mine Ea. The streams have relatively low volumes of water and no 

water from the surface has been detected in the mine. There is also intermittent drainage from 

surface water. Recently a 100-year rainfall event entered the box-cut of Mine Eb and flooded its 

working faces. Subsequently the box-cut design was changed to reduce the 100-year rain event 

impact. The risk assessment team considered the surface creeks and surface drainage hazards to 

be minor and decided to focus on the water hazards from the abandoned mine and adjacent adits. 

The risk assessment geographic boundaries are defined by the outline of the current and future 

face developments adjacent to the abandoned mine and adits (Figure 17). Three segments define 

these boundaries: 

Segment 1 represents Mine Ea’s current and future face developments close to the 

projected boundary of the abandoned mine, 

Segment 2 is for Mine Eb’s current and future face developments close to the boundary 

of the abandoned mine, 

Segment 3 is representative of the boundary between Mine Eb’s future face developments 

and the potential location of adits. 

These three segments are the geographic focus of the risk assessment team. 

51 

Mine-Eb

Segment 2

Abandon Mine

Adits

Mine-Ea

Segment 3

Segment 1

Mine-Eb 

Segment 2 

Abandon Mine 

Adits 

Mine-Ea 

Segment 3 

Segment 1 

Figure 17 - Location of geographic boundaries of the risk assessment. Thick lines define the 

boundaries between the abandoned mines and the current projections for Mines Ea and Eb. 
 

5.5.3.2 – Step 2, Rank Potential Unwanted Events 

With step 1 complete, the team determined six possible mechanisms for water to enter the active 

mines from the abandoned mine and adits (Table 25). These possible mechanics were all 

examined for their ability to produce an inundation event with high consequence. 

•	 Two of the mechanisms are associated with the active mines penetrating the abandoned 

mine and adits. The negative consequence of these events would be very high. 

•	 A third mechanism saw in-seam horizontal drilling activity as a means of creating a 

possible avenue for water and gas flow. The consequence of this potential unwanted 

event is thought to be moderate since the drill hole is relatively small and the drills are 

fitted with packers and shut-off valves capable of isolating the borehole water from the 

mine. 

•	 A fourth mechanism has moderate volumes of water entering the active mines through 

isolated areas of excessive roof-to-floor convergence. These areas are capable of locally 

increasing water flow rates. Here again the consequence is considered to be moderate 

since the water volumes are not expected to be significant. 

•	 The final two mechanisms had relatively small quantities of water flowing along geologic 

structures within or adjacent to the mined coalbed. A study by Moebs and Sames (1989) 

characterized the water flows rates along a potential geologic discontinuity that produced 

a connection between a water-filled abandoned mine and an active mine workings. These 

water flow rates represented a concern for the mine operator, but were unlikely to result 

in a catastrophic release of water. Therefore, the consequence of these events is 

considered to be low. 

Table 25 - Consequences of different inundation mechanisms. 

# Mechanism for inundation Consequence 

1 Water violently enters the mine under pressure through a relatively large opening 

caused by mining directly into the abandoned mine along Segment 1 High 

2 Water violently enters the mine under pressure through a relatively large opening 

caused by mining directly into the abandoned mine along Segment 2 High 

3 

Considerable quantity of water and/or mine gases enter the mine under relatively 

low pressure through an opening caused by mining directly into adits along 

Segment 3 

High 

4 High-pressure, low-volume water enters the mine through the in-seam horizontal 

drill holes Moderate 

5 Moderate water volumes enter the mine through zones of fractured rocks caused 

by excessive roof-to-floor convergence 

Low 

6 Relatively small volumes of water enter the mine along permeable rock layers 

and geologic structures in the coal and its adjacent strata Low 

7 Relatively small volumes of water enter the mine through the cleat structures 

within the coal seam Low 

In this study, it was possible to ignore the likelihood of an inundation event because the 

consequences are indisputably significant. Therefore the team decided to forego ranking the risk 

using a risk matrix. Instead the risks were ranked solely on their consequence. 

52 
5.5.3.3 – Step 3, Determine Important Existing Prevention Controls and Recovery Measures 

A BTA was used to determine important existing and new prevention controls and recovery 

measures. The high-consequence events listed in Table 25 were combined to read “water 

inundation occurs from adjacent old mine workings” and placed within the central node of the 

BTA (Figure 18). Three threats and three consequences were identified by the team and 

discussions of existing and new prevention controls and recovery measures followed. The 

threats were: 1) didn’t know old mine workings were there; 2) dangerous gases in the adits; and 

3) mined into old workings due to mining error. The consequence of mining into an old mine 

workings were: 1) increased water flow into active mining area; 2) minor water inrush; and 3) 

major inrush blocks normal egress routes. 

Potential causes

Potential outcome

Prevention 

controls

Recovery 

measures

didn’t know 

old mine 

workings 

were there

increased 

water flow into 

active mining 

area

dangerous 

gases in the 

adits

mined into 

old workings 

due to 

mining error

minor water 

inrush

major inrush 

blocks normal 

egress routes

ter 

inun ation 

 from 

adjac nt old 

orkings 

Wa

d

occurs

e

mine w

Potential causes 

Potential outcome 

Prevention 

controls 

Recovery 

measures 

didn’t know 

old mine 

workings 

were there 

increased 

water flow into 

active mining 

area 

dangerous 

gases in the 

adits 

mined into 

old workings 

due to 

mining error 

minor water 

inrush 

major inrush 

blocks normal 

egress routes 

Water 

inundation 

occurs from 

adjacent old 

mine workings 

Figure 18 - Graphical depiction of the BTA used in the inundation risk assessment. 

The mine operator is using several Best Practice techniques to aid in preventing the unwanted 

event. The techniques are listed below and are used in many different scenarios, principally to 

help verify the location of old mine workings. These techniques were often used as priority 

prevention controls during discussions of specific threats and consequences. For the purposes of 

this study, the four techniques were combined into one prevention control aimed at verifying the 

location of old mine workings. 

• Technique 1 - Discussions with miners familiar with the abandoned mine in question: 

The abandoned mine was in operation until 1967. There are miners available who have 

knowledge of this recently abandoned mine plan and are used to help verify the accuracy of 

existing mine maps. On the other hand, adits were developed long ago and no records or miners 

exist with knowledge of these mines. 

• Technique 2 - Surface seismic reflections capable of detecting underground mine voids: 

Several surface seismic reflection lines have been run over areas that were relatively far from the 

active mine but where additional information about the location of the abandoned mine was 

desired (Figure 19). 

53 
• Technique 3 - Surface geophysical resistivity surveys capable of detecting water-filled 

mine entries: Resistivity surveys have been completed, probing for water-filled entries along the 

boundaries of the abandoned mine (Figure 19). 

• Technique 4 - Surveyed boreholes both from the surface (vertical) and underground 

(horizontal) to pinpoint the location of old mine workings: Boreholes are used to confirm the 

location of old mine workings. Surface boreholes have helped to establish the elevation of the 

water pool in the abandoned mine and to find adits. These holes are capable of removing water 

from the abandoned mine and present a safe way to ventilate gases from the adits. Horizontal 

drill holes are a much more effective means of locating old works but require the underground 

mine to be in proximity to the old mine workings. Both mines have used this technology (Figure 

19). Typically, the boreholes are drilled from the inby end of a development section. These 

boreholes either probe the coalbed ahead of the working faces or examine the coalbed to be 

mined by future development sections. Typically, horizontal boreholes are used if further 

clarification is required or when mining occurs closer than 200 ft from a known old mine 

workings. 

Current mCurrent mine 

development section 

Previous 

mine 

development
 

sections Abandon Mine

Main entries Main entries 

Portal 

Figure 19 - Techniques used to find the location of water-filled old mine workings at Mine Ea. 

Besides the four techniques to verify the location of old mine workings (PC1), the team 

identified six other existing prevention controls (Table 26). Five controls were aimed at 

54 
 

 

 

 

lessening the risk of mining into old workings because their locations were not known. These 

controls focused on verifying the true location of the old mine workings (PC1), identifying a 

200-ft barrier around these old mine workings to account for inaccurate data or interpretations 

(PC2), in-seam probe drilling when faces were thought to be less than 200 ft away (PC3), 

ensuring communications to all necessary personnel (PC4), and observing unusual conditions 

that might signal that old mine workings were close by (PC5). The sixth control was specific to 

adits, where vertical boreholes are sometimes used to ventilate potentially dangerous gases along 

Segment 3 (PC6). The seventh control is used to lessen the chances of a mining error occurring 

by requiring mining crews to perform daily survey checks and compare them to mine projections 

(PC7). 

Table 26 - Summary of existing prevention controls and recovery measures for a potential mine 

inundation. 

Existing prevention controls 

Threat 1 – Didn’t 

know old mine 

workings were 

there 

PC1 Use the four identified techniques to assist in validating the location of old 

mine workings (MH) 

PC2 Identify a 200-ft barrier of solid coal around the known position of old mine 

workings, place its position on mine maps, and communicate this 

information to the workforce (PB) 

PC3 In-seam horizontal drilling is required if the active mining faces are within 

200 ft of the known location of old mine workings (MH) 

PC4 Communicate the information about efforts to validate the location of old 

mine workings and their known locations to miners (PST) 

PC5 Workers observe certain conditions that might indicate that a water-filled old 

mine workings is close, i.e. enhanced water making its way through the coal 

seam at the working face or the smell that standing water sometimes gives 

off, and communicate these conditions to their foremen and others (PST) 

Threat 2 – 

Dangerous gases 

in the adits 

PC6 Vertical boreholes are used to ventilate potentially dangerous gases from 

adits in Segment 3 (MH) 

Threat 3 – Mined 

into old workings 

due to error 

PC7 Mining crews are required to perform daily survey checks and compare to 

mine projections (P) 

Existing recovery measures 

Consequence 1 – 

Increased water 

flow into active 

mining area 

RM1 Operator will call others underground on hand-held radios to alert them of 

changing conditions and give evacuation instructions (P) 

Consequence 2 – 

minor inrush 

RM2 Follow existing Emergency Response Plan to evacuate the mine (PST) 

Consequence 3 – 

major inrush 

blocks normal 

egress routes 

RM3 Follow existing Emergency Response Plan to evacuate the mine; however, 

exception could occur, i.e. miners in Mine Ea may decide to move to the 

highest elevation, potentially north along the mains, to escape inrush as it 

moves from the faces down-dip to the portal; and miners in Mine Eb may 

need to alter egress routes as they escape up-dip toward the portals and away 

from the flooding faces. (PST) 

PC – Prevention Controls 

RM – Recovery Measures 

MH – Minimize Hazard 

PB – Physical Barrier 

WD – Warning Devices 

P – Procedures 

PST – Personnel Skills and Training 

55 
 

 

Three existing recovery measures were also identified. If mining conditions noticeably change 

or an inundation occurs, workers communicate information and evacuation instructions through 

hand-held radios (RM1). When water inrush conditions occur, the miners are to evacuate 

according to the Emergency Response Plan (RM2). Finally, if a major inrush were to occur, it 

could possibly block normal egress routes. Miners may consider alternate egress routes as 

outlined in RM3. 

5.5.3.4 – Step 4, Identify New Prevention Controls and Recovery Measures 

Five new ideas were identified by the team to further reduce the inundation risks at the mine 

(Table 27). These ideas were listed as part of an Action Plan with the ideas inserted and space 

left for derivation of specific actions, timing and resources. Four of the five were potential 

recovery measures. The only new prevention control formalizes the process of using water/smell 

conditions to look for or to identify potential inundation conditions (NI1). The team thought it 

important to have calculations of potential flooding rates for both mines (NI2). This information 

could be used to further evaluate the inundation hazards and could be used when considering NI4 

and 5. The team believed that an important way to minimize losses was to restrict access to 

certain areas of the mine during key time intervals (NI3). Restricted access should be considered 

when mining in areas near the abandoned mine and adits, i.e. along Segments 1, 2 and 3. The 

team spent considerable time discussing how egress from the faces would be influenced by the 

size and location of the inrush event. It was not possible to sufficiently analyze this issue during 

the risk assessment and make adjustments to the Emergency Response Plan (NI4). For example, 

it may not be possible for the miners to use existing escapeways if the inundation event occurred 

along Segment 1. In this case, water would enter the face and run down-dip along the main 

entries, forcing miners up-dip toward the working faces along the main entry. Other scenarios 

were also discussed with some having the miners wait in less hazardous areas until the threat 

subsides or they are rescued. The team thought it important that techniques be investigated (NI5) 

to communicate, locate and rescue trapped miners underground (e.g. tapping, signals, phones, 

surface access, emergency supply skid, etc.). 

Table 27 - New ideas proposed by the risk assessment team for preventing or recovery from an 

inundation at Mines Ea and Eb. 

New prevention control 

ideas 

NI1 Formalize water/smell conditions to look for or to identify possible inundation, 

as well as action to be taken in those conditions, and introduce to personnel (P) 

NI2 Calculate rates of flooding for both mines to estimate the consequences of an 

inundation on egress routes and communicate to the miners (PST) 

New recovery measure 

ideas 

NI3 Restrict access to certain areas of the mine, i.e., no one in return entry when 

mining in areas near the abandoned mine and adits. ( Segments 1, 2 and 3) (P) 

NI4 Develop the Emergency Response Plan beyond MSHA requirements to address 

specific mine issues (P) 

NI5 Investigate methods and actions that should be undertaken if persons are 

trapped underground due to flooding (e.g. tapping, signals, phones, surface 

access, emergency supply skid, etc.) (PST) 

NI – New Ideas 

MH – Minimize Hazard 

PB – Physical Barrier 

WD – Warning Devices 

P – Procedures 

PST – Personnel Skills and Training 

56 
5.5.3.5 – Step 5, Discuss Implementation, Monitoring and Auditing Issues 

Assuming that the information provided in the risk assessment was accurate, completion of the 

Action Plan and an increased focus on monitoring and auditing of the key identified controls 

would appear to provide an opportunity to effectively reduce the risk of fatalities related to 

inundation at Mines Ea and Eb. The risk assessment showed that the mine relied extensively on 

prevention controls (PC) that reduce the risk of water inundation from mining into the abandoned 

mine (Figure 20). The figure also shows a somewhat limited number of existing recovery 

measures (RM) identified by the risk assessment team. Four of the five new ideas addressed 

recovery measures, demonstrating the team’s interest in improving the way the mining operation 

should respond to an actual inundation event. All of the new ideas were controls classified as 

procedures (P) and personnel skills and training (PST) (Figure 20). 

57 

0 

1 

2 

3 

4 

EH MH PB WD P PST 

Number 

Prevention Controls Recovery measures New Ideas 

Figure 20 - Distribution of prevention controls and recovery measures for the water inundation 

risk assessment. 
Portal 1 

Highwall 

Portal 2 

5.6 – Escapeway Egress Blockage Risk Assessment Case Study

Mine F is an underground limestone mine experiencing unstable ground conditions that 

potentially threaten the use of its alternate escapeways. The general conditions found at the mine 

are shown in Figure 21. The part of the mine relevant to this study was mined over 40 years ago 

using the room-and-pillar technique. Large rooms were driven 45 ft wide and 30 ft high 

perpendicular to a highwall in an adjacent quarry and off-set cross-cuts of the same size were 

mined typically on 90-ft centers. The parallel Primary and Alternate Escapeways run southeast 

from Portals No.1 and 2 to inby portions of the mine. In January 1994, a roof collapse occurred 

in an area adjacent to the Alternate Escapeway about 250 ft from Portal No.2. Between January 

1994 and December 2006, other roof falls have occurred to the southwest of the Alternate 

Escapeway, resulting in a large restricted area. Management has responded to this roof 

instability hazard through Best Practice controls, including roof monitoring, supplemental 

standing support, and tensioned cable bolts in the Alternate Escapeway adjacent to the restricted 

area. 

Surface Quarry 

Primary 

Escapeway
 

Alternate 

Escapeway
 

Jan. 94 

Roof Fall
 

Restricted 

Area
 

Feb. 07 

Roof 

Cracks
 

Jan. 07 Roof Fall 

and Associated 

Roof Cracks

Figure 21 - Escapeways, roof falls and recent roof cracks found at the mine. 

Recently, roof conditions in the escapeways showed signs of deterioration. Of particular concern 

are the January, 2007, roof fall and the January/February, 2007, appearance of intermittent, en 

echelon roof cracks (Figure 21). One of these roof cracks is especially troublesome because it 

extends across the Alternate Escapeway and into the Primary Escapeway, signaling an elevated 

risk. 

58 
5.6.1 – Risk Assessment Scope 

The objective of this risk assessment is to 1) identify hazards that could affect egress through the 

mine’s escapeways, 2) determine what unwanted events pose the greatest threat to mine workers 

escaping from the mine, 3) review the existing prevention controls and recovery measures, and 

4) recommend new ideas to prevent, or recover from, potential disruption of escapeway egress. 

The initial MHRA steps consist of scoping document generation, scoping team selection, and 

assessment framework identification. 

The risk assessment team agreed to frame the assessment by limiting it to the Primary and 

Alternate Escapeways when egress was disrupted by a roof collapse or fire hazard. Normal 

ventilation operating conditions were considered, which means the fan at the ventilation shaft is 

either exhausting or blowing into the mine. During exhaust conditions both escapeways are in 

fresh air, while under blowing conditions the escapeways will be in return air. Hazards and risks 

were considered in relation to their probability of occurring within five years. 

5.6.2 - Risk Assessment Team 

The scoping team consisted of the following persons: 

 Mine Supervisor 

 Mine Engineer 

Rock Mechanics Engineer 

Miner 

 Safety Officer 

Subject matter experts (Strata Control, Ventilation, Mining Regulation and Mine Evacuation)

 Facilitator – NIOSH 

5.6.3 – Risk Assessment 

First, major hazards associated with egress through Primary and Alternate Escapeways during an 

emergency at the mine were reviewed. Consequences associated with the unwanted event were 

investigated and the likelihood of the event occurring was estimated. Threats that disrupt egress 

through the escapeway were analyzed and ranked using a risk matrix technique. Finally, existing 

and new controls and recovery measures were identified. 

5.6.3.1 – Step 1, Identify and Characterize Major Potential Mining Hazards 

Hazards that affect egress through the mine’s escapeways are identified by first dividing the 

escapeway system into logical segments and then analyzing the various types of hazards. For the 

purposes of this analysis, the description of a metal/nonmetal escapeway follows from the 

definitions cited in the Code of Federal Regulations, Part 30, Section 57.11050 (CFR, 2005). 

The escapeway system at the study mine can be subdivided into six segments (Figure 22). 

59 
Portal 1 

Highwall 

Portal 2 

Surface Quarry 

1
 

3 2 

4 

LEGEND 

5 Primary escapeway 

Alternate escapeway 

6 Segment number 6
 

Figure 22 - Six segments of the mine's escapeway system. 

The two kinds of hazards investigated in this study are fire and roof collapse. Fire hazards are 

identified by considering potential fuel and ignition sources. The results are summarized in 

Table 28. 

Table 28 – Fire hazards consisting of potential fuel and ignition sources. 

Diesel equipment – truck, front end loader, backhoe, grader, crane, scoops and other smaller 

Fuels 

pieces of diesel equipment 

Fuel Storage – diesel tanks and other flammable materials 

Electrical – Mine carts, transformers, substations and power lines 

Other Equipment and Storage – conveyor belt, natural gas pipe line, wood, PVC pipe, and other 

minor amounts of material 

Ignition/

heat 

sources 

Overheating of diesel equipment, electrical equipment and electrical cabling 

Welding and cutting operations 

Lightning 

Roof instability hazards are considered only in terms of their potential to block egress through 

escapeways. Small roof falls that can result in injuries were therefore excluded from the 

analysis, since they do not block egress. A NIOSH-developed tool, called the Roof Fall Risk 

Index (RFRI), was used to systematically identify roof fall hazards in the escapeways. The RFRI 

is a hazard assessment technique that maps the spatial distribution of stability conditions. The 

RFRI focuses on the character and intensity of defects associated with specific roof conditions 

(Iannacchione et al., 2006; Iannacchione et al., 2007). Ideally, values approaching 0 represent 

safer roof conditions, while an RFRI approaching 100 represents a serious roof fall hazard. The 

RFRI values for the mine’s escapeway system are shown in Figure 23. Higher values indicate 

increasing risk of roof collapse in the absence of additional roof stabilization efforts. For 

60 
example, the relative roof fall risk in Segment 1 of the Primary Escapeway is potentially lower 

than in Section 2 because this section contains roof bolts, wire mesh and narrower entry spans. 

Portal 1 

Highwall 

Portal 2 

Surface Quarry 

RFRI measurement 

areas 

Figure 23 - Roof Fall Risk Index (RFRI) measured in the mine's escapeways. 

5.6.3.2 – Step 2, Rank the Potential Unwanted Events 

As the team became familiar with the escapeway routes, current ground conditions, and 

ventilation and operational requirements, the risk for a potential unwanted event in each segment 

was determined. The risks associated with unwanted events were rated using the WRAC method 

which considers the likelihood and consequences of each event. 

The scoping team identified 28 potential threats based on the defined list of hazards (Table 29). 

Each potential threat was risk ranked using a qualitative risk analysis method and a 4 by 5 risk 

matrix (Table 30). Lower numbers indicate a higher risk. The likelihood of an event was 

subjectively assessed by considering the probability of the event occurring in the next five years. 

The consequences of an event were assessed by considering its potential impact on the ability to 

evacuate the mine in case of an emergency. This included consideration of blockage of 

escapeway routes and the spread of toxic fumes or smoke. Both exhaust and blowing ventilation 

scenarios were considered. The inability to use either escapeway for egress from the mine 

during an emergency was considered to be the highest impact consequence. 

61 
 

 

 

 

 

 

 

 

 

 

 

Table 29 - Risk ranking of potential threats grouped by escapeway segment. 

Escapeway 

Segment Potential Threats Consequence (impact) 

Likelihood (next 

5 years) 

Risk 

ranking 

1 

Equipment fire – fan exhausting High Unlikely 7 

Equipment fire – fan blowing Moderate Unlikely 8 

Roof collapse High Very Unlikely 11 

Diesel storage fire – fan exhausting High Very Unlikely 11 

Diesel storage fire – fan blowing Moderate Very Unlikely 16 

2 

Roof collapse High Likely 4 

Equipment fire - fan exhausting High Very Unlikely 11 

Equipment fire – fan blowing High Very Unlikely 11 

Electrical cable fire Low Very Unlikely 18 

3 

Equipment fire – fan exhausting High Unlikely 7 

Equipment fire – fan blowing Moderate Unlikely 12 

Charging station fire – fan exhausting High Likely 4 

Charging station fire – fan blowing Moderate Likely 8 

Transformer fire – fan exhausting Low Unlikely 16 

Transformer fire – fan blowing Low Unlikely 16 

Natural gas leak explosion High Very Unlikely 11 

Flammable storage cabinet catches fire Low Very Unlikely 20 

Roof collapse High Very Likely 2 

4 

Equipment fire – fan exhausting High Very Unlikely 11 

Equipment fire – fan blowing High Very Unlikely 11 

Roof collapse Moderate Very Likely 5 

5 

Equipment fire – fan exhausting High Unlikely 7 

Equipment fire – fan blowing Moderate Unlikely 12 

Roof collapse Moderate Unlikely 12 

Transformer catches fire Low Very Unlikely 20 

6 

Equipment fire during travel – fan exhausting Low Very Unlikely 18 

Equipment fire during travel – fan blowing Low Very Unlikely 18 

Roof collapse Low Unlikely 16 

Table 30 - A 4 by 5 risk matrix for ranking the potential threats. 

Consequence Likelihood (event occurs in next 5 years) 

Certain Very Likely Likely Unlikely Very Unlikely 

High Impact 1 2 4 7 11 

Moderate impact 3 5 8 12 16 

Low impact 6 9 13 17 20 

No impact 10 14 18 21 23 

The top four potential threats identified through the WRAC are: 

1. Roof collapse in Primary Escapeway of Segment 3 

2. Charging station fire in Primary Escapeway of Segment 3 

3. Roof collapse in Alternate Escapeway of Segment 2 

4. Roof collapse in Alternate Escapeway of Segment 4 

62 
 

 

 

 

5.6.3.3 – Step 3, Determine Important Existing Prevention Controls and Recovery Measures 

The team discussed the nature and quality of the prevention controls as part of the BTA. The 

outcomes of the BTA are presented in Appendix B. Eleven key prevention controls currently in 

place are identified and listed in Table 31. Controls for roof collapse hazard used in portions of 

the Primary and Alternate Escapeways consisted of 6- and 8-ft grouted bolts placed on 5-ft 

centers (PC1). This support occurs through most, but not all, of the Primary Escapeway and only 

within the first 200 ft of Portal 2 in the Alternate Escapeway. Typically the mine is completely 

scaled every 3 to 6 months, but scaling of individual loose rock occurs as needed (PC2). 

Periodic observations of roof conditions are made by the mine supervisor, mine engineer and 

miners on a regular basis (PC3). Both multipoint roof sag extensometers and roof-to-floor 

convergence sensors have been used in the Alternate Escapeway to assess stability conditions 

(PC5). Over 100, 30-ft long, 60-ton capacity cable bolts have been installed and tensioned to 20 

tons as a means of adding support to a section of Alternate Escapeway roof near the restricted 

area (PC6). These cables were installed at a 30 ̊ angle from vertical to help prevent roof 

instabilities associated with prominent joints. Finally, three massive breaker wall standing 

supports, 45 ft wide by 30 ft high, were installed in cross-cuts between the Alternate Escapeway 

and the restricted area (PC7). Fire hazard controls consist of weekly battery checks (PC4). 

Table 31 - Existing prevention controls and recovery measures for a loss of emergency 

escapeway at Mine F. 

Existing prevention controls 

Threat 1 – Roof collapse in 

Primary Escapeway Segment 3 

PC1 Primary support – 6- and 8-ft grouted bolts (PB) 

PC2 Scale roof and ribs every 3 to 6 months, or as needed (P) 

PC3 Periodic observation of roof conditions (PST) 

Threat 2 – Charging station fire in 

Primary Escapeway Segment 3 

PC4 Battery water levels and terminals are checked weekly (P) 

Threat 3: Roof collapse in 

Alternate Escapeway Segment 2 

PC5 Monitoring with multipoint extensometers (WD) 

PC6 Cable bolt support with steel screen (PB) 

PC7 Breaker wall standing support (PB) 

As above: see PC3 

Threat 4 – Roof collapse in 

Alternate Escapeway Segment 4 

PC8 Monitor microseismic emissions from the mine (just begun) WD) 

As above: see PC2 & PC3 

Existing recovery measures 

Consequence 1 – Roof collapse 

blocks the Primary Escapeway 

RM1 Escapeway must be cleared and re-supported or a new escapeway 

designated (PB) 

Consequence 2 – Charging Station 

Fire in Primary Escapeway 

RM2 Station partially enclosed by a block wall & metal roof (PB) 

RM3 Scoop has fire suppression system (MH) 

RM4 Fire extinguishers are present, although current policy is to 

evacuate rather than fight fire (PST) 

RM5 Main office coordinates communication via radio (P) 

RM6 Use radios to communicate fire alarm to all underground (WD) 

RM7 Sound the siren (WD) 

RM8 Lifelines exist in part of the Primary Escapeway (PST) 

Consequences 3 and 4 - Roof fall 

blocks Alternate Escapeway 

As above: see RM1 

PC – Prevention Controls 

RM – Recovery Measures 

MH – Minimize Hazard 

PB – Physical Barrier 

WD – Warning Devices 

P – Procedures 

PST – Personnel Skills and Training 

63 
The team identified nine existing recovery measures. The only recovery measure for a large roof 

collapse capable of blocking the Primary or Alternate Escapeways is to clean up the fall material 

and re-support the entry or develop a new Primary or Alternate Escapeway (RM1). Seven 

recovery measures for a fire in the charging station area were identified. A cinder block wall and 

metal roof have been built and could partially contain a charging station fire (RM2). Several 

pieces of diesel equipment have fire suppression systems (RM3). Fire extinguishers are present 

in this area, although current policy is to evacuate rather than fight the fire (RM4). In the event 

of an evacuation, radio communication, directed by the mine office, would be used to 

communicate a fire alarm (RM5). All miners and persons accompanying visitors are issued 

radios that can be used to communicate a fire alarm (RM6). A site-wide siren is also available at 

the main office that can be heard by all personnel outside the mine (RM7). Lastly, lifelines exist 

in part of the Primary Escapeway (RM8). 

5.6.3.4 – Step 4, Identify New Prevention Controls and Recovery Measures 

Fifteen new ideas were identified by the team (Table 32). New prevention controls are aimed at 

either the roof collapse or fire hazard. For the roof collapse hazards, new controls are divided 

into three groups: administrative, monitoring and engineering. An administrative control in the 

form of a policy could restrict personnel access to the Alternate Escapeway except in an 

emergency situation (NI1). A number of monitoring controls were discussed including: a 

regularly scheduled visual observation plan of roof conditions (NI2); installation of additional 

roof and crack monitors (NI3); repair and replacement of 12-year-old multipoint sag 

extensometer (NI4); and a trigger action response plan (TARP) for monitors (NI5). New ideas 

for preventing roof collapse hazards include a supplemental rock reinforcement program for 

Segment 3 of the Primary Escapeway (NI6). This should be done after additional monitoring has 

gathered sufficient information. A design should also be considered for stabilizing Segment 4 of 

the Alternate Escapeway (NI7). The purpose of this design would be to protect the growth of 

roof falls in the restricted area from weakening the roof in the Alternate Escapeway. The new 

control for the fire hazard was to place the charging station outside the mine (NI8). 

64 
Table 32 - New ideas proposed for preventing or recovery from a loss of emergency escapeway 

at Mine F. 

New prevention 

control ideas 

NI1 Develop a policy to restrict access except in an emergency situation (P) 

NI2 Immediately implement a regularly scheduled roof conditions visual 

observation plan (P) 

NI3 Design and install a monitoring system for roof crack and roof sag detection 

(WD) 

NI4 Repair/replace existing multipoint extensometers (WD) 

NI5 Develop a trigger action response plan (TARP) for roof movement that will 

initiate additional rock reinforcement installation (P) 

NI6 Design a method of stabilizing the roof within Segment 3 of the Primary 

Escapeway based on the information gathered from the roof monitoring 

program (PB) 

NI7 Consider stabilizing the adjacent Alternate Escapeway (Segment 4) to act as 

a buffer for securing this area (PB) 

NI8 Place charging station outside mine (EH) 

NI9 Consider using the ventilation shaft as an Alternate Escape route (P) 

NI10 Consider installing refuge chambers in the active work areas (PB) 

New recovery 

measure ideas 

NI11 Install backup generator for communication system (MH) 

NI12 Install fire detection/suppression systems on large diesel equipment (MH) 

NI13 All personnel and visitors to wear SCSRs (training needed) (PST) 

NI14 Close down charging station when the general public is underground (P) 

NI15 Finish installing lifeline in all escapeways (PST) 

NI – New Ideas 

EH – Eliminate Hazard 

MH – Minimize Hazard 

PB – Physical Barrier 

WD – Warning Devices 

P – Procedures 

PST – Personnel Skills and Training 

Several new recovery measure ideas were identified by the team. To mitigate the impact of a 

roof collapse, the existing ventilation shaft could be used as an Alternate Escapeway (NI9). 

Also, a rescue chamber could be installed in active work areas (NI10). New ideas to help 

recover from the fire hazard included using a backup generator for the communication system 

(NI11). It was also suggested that additional fire detection/suppression systems be installed on 

large diesel equipment (NI12). Elevated Personal Protective Equipment requirements were 

discussed with the goal of all personnel and visitors carrying SCSRs underground and receiving 

training on their use (NI13). Finally, the team suggested limiting the use of the charging station 

(NI14) and installing lifelines throughout all the escapeways (NI15). 

5.6.3.5 – Step 5, Discuss Implementation, Monitoring and Auditing Issues 

The mine’s existing prevention controls and recovery measures were identified and should be 

monitored and audited. New potential control and recovery measures were produced in the form 

of an Action Plan for consideration by management. The Action Plan, with the ideas inserted, 

contained spaces for resources and timing of each idea. The plan was delivered to management 

for prioritization and implementation. Some of the new ideas are somewhat vague in that they 

broadly called for new designs. No attempt was made by the team to prioritize the new ideas, 

with the team deciding that it was inappropriate to select a specific design as part of the MHRA 

65 
process. Detailed designs are not easily accomplished in an MHRA exercise. Management will 

need to weigh the various ideas and determine what activities are best suited for their particular 

circumstances. 

The team seemed to agree that it was not possible to eliminate the roof fall hazard at this site. 

The only recourse was to decide to mitigate or tolerate the hazard. Activities to control the 

escapeway fire hazard were handled with well-defined actions, while activities to control roof 

falls relied on designs or actions that were not easily defined. Most of the new control ideas 

were classified as procedures (P), although new ideas were proposed in all control categories 

(Figure 24). The one control that eliminated the hazard (EH) was associated with the new idea 

to move the battery charging station out of the underground environment. 

66 

6 

5 

4 

3 

2 

1 

0 

Number 

EH MH PB WD P PST 

Prevention Controls Recovery measures New Ideas 

Figure 24 - Distribution of prevention controls and recovery measures for the escapeway egress 

blockage fire risk assessment. 
5.7 – Natural Gas Ingress Risk Assessment Case Study 

This case study involves two mines (Mines Ga and Gb) operating in an evaporate deposit at 

depths ranging from 400 to 1,500 ft using continuous miners to develop a room-and-pillar 

mining layout. Figure 25 shows one level within Mine Ga, depicting main entries and 

production panels. The panels are mined with a higher extraction ratio. After initial crushing, the 

mined ore is moved to shafts by conveyors and hoisted to the surface. Several thousand feet 

below the mining levels lies a widespread nature gas and oil producing formation. This 

formation has been extensively drilled within and in proximity to the study mines for many 

decades to recover the natural gas and oil. The mine is aware of the current and past drilling. 

Significant precautions have been undertaken to reduce the likelihood that gas or oil from the 

reservoir below the mine does not enter the mine workings. However, because the consequences 

could be so significant, this mining operation has decided to review issues related to natural gas 

ingress using a systematic risk assessment method. 

67 

Slope

Panels

Active 

faces

Slope 

Panels 

Active 

faces 

Figure 25 - Mine Ga layout showing the location of active faces, the slope and panels within one 

active level. 
5.7.1 - Risk Assessment Scope 

The objective of this risk assessment was to: 

1.	 Review hazards associated with the potential for a natural gas inundation of the active 

mining area, 

2.	 Evaluate strategies and techniques for management of the hazards, and 

3.	 Provide information to help develop an inundation risk management plan for this mine. 

The risk assessment project was scoped during discussion with the study mine’s management 

and NIOSH personnel. The mine’s personnel did not attend the NIOSH-sponsored Minerals 

Industry Risk Management Seminar. 

5.7.2 - Risk Assessment Team 

The risk assessment team was made up of persons familiar with the mine’s operation and work at 

the mine in various capacities, as well as an external facilitator and two NIOSH observers, as 

follows: 

Manager of mines 

Chief mine engineer 

Manager of engineering 

Manager of safety 

Manager of operations 

Relief electrical supervisor 

Two NIOSH Observers 

Facilitator – MISHC (University of Queensland) 

No representatives from labor participated in the risk assessment. 

5.7.3 – Risk Assessment 

The Risk Assessment involved facilitation of a team of personnel through a structured process 

involving the following steps: 

1.	 Hazard description 

2.	 Pathways identification 

3.	 Potential unwanted event identification 

4.	 Bow Tie Analysis method introduction 

5.	 Causes and prevention controls discussion 

6.	 Consequences and loss reduction controls discussion 

7.	 Repeat of Steps 5 and 6 for all the unwanted events identified in Step 3. 

Two days were dedicated to the risk assessment. 

68 
5.7.3.1 – Step 1, Identify and Characterize Major Potential Mining Hazards 

The first step in the risk assessment involved identifying and understanding the hazard related to 

natural gas and oil around the current and planned mining operations. The primary inundation 

hazard was seen to be the natural gas reservoir located approximately 10,000 feet below the 

surface, as well as the gas in any natural or man-made conduits from below. There was also a 

hazard related to gas being piped on the surface or in proximity to the mines. 

Pathways from the gas reservoir and gas wells into the mine were identified by the team (Figure 

26) as follows: 

• Up the inside of the drill pipe 

• Up the drill hole but outside the casing 

• Up/along faults 

• Up/along igneous intrusions such as dikes 

• Up through permeable ground along fractures or cleats 

• Up collapsed breccia pipes 

• Down to mine workings from wells damaged by subsidence 

W 

E 

L 

L 

400’ 

Subsidence 

Pathway thru 

fractures & cleats 

Intrusion 

Fault 

Breccia 

Natural Gas & Oil in Permian Basin at 10,000’ 

Figure 26 - The risk assessment team created this schematic to illustrate the hazards and 

pathways related to the study mines. 

The team noted that the strata at the study mines can produce sparks during production with the 

cutting machine. Also, there is no intrinsically safe mining equipment at either mine. The mines 

are currently classified by MSHA as Class IV. Therefore, should natural gas enter the mine, heat 

sources could be readily available to cause an ignition. 

The mine has protocols for different gas methane levels detected by hand-held units: 

At 0.5% ventilate and retest; requires notification of supervisor. 

At 1.0% ventilate, shut down equipment, notify supervisor, power off in the panel. 

At 2.0% ventilate, shut down equipment, remove personnel, and notify supervisor. 

69 
The monitors are intended for methane but will respond to natural gas, though it was not clear 

whether the monitors have been calibrated to the natural gas. If an explosion occurred, the 

related over-pressure conditions would probably destroy the brattice (cloth) stoppings. This 

could disrupt the mine’s ventilation and hinder egress from the mines. Both mines have series 

ventilation where the exhaust from one panel becomes the intake air to the next panel. Figure 27 

shows the nature of Mine Ga’s ventilation system where air travels in one long circuit through all 

the active advancing faces and production panels. If a gas ingress event occurs, the fresh air 

intake downstream from the gas entry point could be compromised and adversely affect egress 

from the mine. In addition, barricading may not work for this type of event, since miners will 

need to get out of the mine quickly due to the explosive potential of released gas. 

SLOPE 

c 

c 

c 

c

c 

c 

Figure 27 - Detailed view of the ventilation circuit used at Mine Ga. 

The team identified that ingress of natural gas into the mine workings could have all or some of 

the following consequences: 

•	 Oxygen displacement 

•	 2–15% hydrocarbon (methane mostly) explosive range atmospheres 

•	 Large prolonged ignition 

•	 Multiple fatalities 

•	 Major mine damage 

•	 Classification of mine to an MSHA gassy mine, which could potentially result in the 

closure of the mine due to higher operating cost for permissible equipment. 

5.7.3.2 – Step 2, Rank the Potential Unwanted Events 

The risk assessment team identified that any ingress event could be catastrophic to the mine and, 

potentially, mine personnel. It was therefore necessary to analyze all potential unwanted events 

and not to attempt to rank these events since all of them could potentially produce catastrophic 

70 
consequences. In this case study, it was not necessary to perform a WRAC or a PHA to rank the 

unwanted events. 

The team identified a list of potential unwanted events for further consideration where natural 

gas ingress was caused by: 

1.	 Mining into an existing oil/gas well 

2.	 Mining into old workings that contain gas from pathways or another source 

3.	 Mining into fault / dike / breccia pipe which contains gas 

4.	 Surface drillers accidentally fracturing a well in a way that creates a pathway for gas into 

mine workings 

5.	 A sudden collapse in an old mined area leading to a puff or blast of gas into mine 

workings 

6.	 Gas leaks into mine workings from an oil/gas well through strata 

7.	 Gas leaks into mine workings from faults or dikes 

8.	 Gas leaks into mine workings from breccia pipes 

9.	 Gas leaks into mine workings through permeable ground 

10. Gas leaks into mine workings from subsidence around well area 

11. A gas line on the surface rupturing and the gas being sucked into mine surface ventilation 

intake (note that the fans are underground). 

5.7.3.3 – Step 3, Determine Important Existing Prevention Controls and Recovery Measures 

The BTA approach was used to consider each of the above events. For example, the No. 1 

potential unwanted event “Mining into an existing oil/gas well” forms the top event in the center 

of the bow tie of Figure 28. For each potential cause on the left side of the bow tie, the risk 

assessment team identifies both existing and new key prevention controls. Next, the right side of 

the bow tie is acted on and existing and new potential recovery measures are identified. This 

process is repeated for each of the potential unwanted events. 

71 

Potential causes

Potential recovery measures

Early 

detection

Explosion 

prevention

Evacuation

Prevention 

controls

Recovery 

measures

Unmapped 

well

Operator 

error

Well mapped 

but location 

wrong

Mapped but 

plotted 

wrong

Mining into an 

ex oil/gas 

ll

isting

we

Potential causes 

Potential recovery measures 

Early 

detection 

Explosion 

prevention 

Evacuation 

Prevention 

controls 

Recovery 

measures 

Unmapped 

well 

Operator 

error 

Well mapped 

but location 

wrong 

Mapped but 

plotted 

wrong 

Mining into an 

existing oil/gas 

well 

Figure 28 - BTA for mining into an existing oil/gas well top event. Potential causes are listed on 

the left side of the bow tie with potential recovery measures on the right. 
 

 

 

 

 

 

 

 

Based on the analysis that was done by the team, 33 key existing controls were identified as 

being in place throughout relevant phases of the mining operations (Table 33). As such, these 

controls should be reinforced, monitored and audited with priority. Controls focused on 

reducing potential well misidentification, reducing operator errors, developing more accurate 

geologic information of discontinuities that could transmit oil and gas, and ventilating abandoned 

areas of the mine that might contain oil and gas. BTAs were needed for only the first four 

potential unwanted events. Previously identified controls adequately covered the remaining 

potential unwanted events. 

Table 33 – Existing key prevention controls for the natural gas ingress risk assessment (left side 

of the BTA). 

Top Event => (1) Mining into an existing oil/gas well 

Cause Existing controls to prevent the unwanted event 

Unmapped 

well 

PC1 Physically checks surface well location, i.e. topographic, aerial, recon, etc. (P) 

PC2 Check well location against well location supplied by the State (P) 

PC3 Monitor for new application for drilling (APD) (P) 

PC4 Check on the ground for old well location by locating old bricks, oil seeps, etc (P) 

PC5 Develop and update oil and gas map database (P) 

Well mapped 

but location 

wrong 

PC6 Draw a 1,320-ft circle around oil wells and a 2,640-ft circle around gas wells (PB) 

PC7 Resurvey all locations on mine property (GPS survey) and compare to mine survey to 

reduce likelihood of wrong location on map. (P) 

PC8 Quality Software (CAD and Geographic) check to compare each answer (P) 

PC9 Third party check of data and map location (P) 

Mapped but 

plotted wrong 

PC10 Check ongoing surveys (P) 

PC11 Keep elevation of all mine workings in mine panels (P) 

PC12 Use of best technology and survey every shot with triple flop of scope (P) 

Operator error PC13 Plot oil and gas locations in critical mining areas on escape maps located in dinner hole 

(P) 

PC14 Locate oil and gas wells with plot lease boundaries on foreman regular work area maps 

(P) 

PC15 Panels are surveyed every 125 feet to fix locations (P) 

PC16 Updated maps are given every work day to foremen and operators (P) 

PC17 Work expectations are discussed and clarified every day (P) 

PC18 Shift bosses have access to maps underground (P) 

PC19 Foreman gives each operator his personal map on surface at start of shift (P) 

PC20 Operator error would be identified by shift foremen monitoring mine work to ensure that 

well location is known and operator is following mine plan and matches survey location 

(PST) 

PC21 Operator error (depending on the nature of the inappropriate behavior) would be dealt 

with by known disciplinary procedure (verbal, written communication, days off, fired) 

(PST) 

As above: see PC6 

Top Event => (2) Mining into old workings 

PC22 Old mines in area are naturally ventilated (MH) 

PC23 Existing operations are unsealed (MH) 

PC24 The mine uses the information from BLM data on closed mines and also maintains good 

data on its own captive old mines (PB) 

PC25 The mine uses a 100-ft buffer between old and new mines included in all plans (PB) 

PC26 There is positive air pressure from ventilation for active mining areas causing gas to 

migrate toward old workings, unless old workings have a higher pressure (MH) 

72 
 

 

 

 

 

Top Event => (3) Mining into a fault / dyke or breccia pipe 

PC27 Breccia pipes and dikes have been mapped and located but all faults have not. The area is 

geologically stable so there are not too many faults. The ore horizon is some twelve 

different horizons over a 400-foot depth. Some horizons are economic but some are not 

(P) 

PC28 Gas inrush hazard would be considered to be a slow leak type of event and not a major 

inrush of gas (MH) 

PC29 The mine has past experience with mining into breccias area with an active oil seep (PST) 

Top Event => (4) Drillers accidentally hydra-fracturing a well in a way that creates a pathway from gas into 

mine workings 

PC30 Some drillers notify State Oil Conservation District (OCD) and some companies call the 

mine (PST) 

PC31 Some events are mandated to be reported by the OCD (State) but that requirement only 

affects ~ ten % of the land. Most land is owned by BLM. (P) 

PC32 A permit to drill is required which allows the mine to publicly comment on the drilling 

application (P) 

PC – Prevention Controls 

EH – Eliminate Hazard 

MH – Minimize Hazard 

PB – Physical Barrier 

WD – Warning Devices 

P – Procedures 

PST – Personnel Skills and Training 

Based on the analysis that was done by the team, 15 key recovery measures controls were 

identified (Table 34). These recovery measures fit into three categories: early detection, 

explosive prevention, and evacuation. Early detection relies on supervisors monitoring the 

working environment. Explosion prevention requires numerous actions to de-energize the mine 

or alter ventilation. Evacuation is focused on communicating instructions to the workforce and 

assisting in the movement of workers out of the mine with breathing equipment. A BTA was 

only needed for the first potential unwanted events. All other unwanted events produced the 

same set of recovery measures. 

Table 34 – Existing key recovery measures for the natural gas ingress risk assessment (right side 

of the bow tie). 

Top Event => gas inrush occurs 

Early 

detection 

RM1 The mine has ongoing gas detection for O2 and CH4 for operators and O2, CO and CH4 for all 

supervisors (WD) 

Explosion 

prevention 

RM2 If major inrush of gas occurs the expectation is that all equipment power will be shut off 

(miner can trip power to transformer from mining machine), supervisors are notified and all 

other equipment would be shut down (P) 

RM3 Power can be shut off to rest of mine except hoist by the electrical power supplier (P) 

RM4 Mine power can be shut down by surface personnel (P) 

RM5 Ventilation fans are underground and can be shut off or reversed (MH) 

Evacuation RM6 Current evacuation plans call for mine workers to utilize diesel equipment to get to shaft 

through the intake auxiliary escape route (PST) 

RM7 Escape and emergency egress is practiced every six months (PST) 

RM8 Other U/G personnel not in the immediate vicinity of gas inrush would be notified by one of 

three ways: page phone system, word of mouth, or flashing lights on belts (WD) 

RM9 The hoistman is the key communication person (P) 

RM10 Workers when they call in are directed to which egress pathway to take (P) 

73 
 

 

 

 

 

RM11 The person calls his supervisor who may or may not know which way to escape. Supervisor 

may or may not be in communication with hoistman (P) 

RM12 At both mines power of hoist is totally isolated from mine power (MH) 

RM13 There are refuge chambers at each mine fed by compressed air from surface with enough 

food, water and air for 80 people (PB) 

RM14 There are caches of SCSR breathing apparatuses located at each mine (one hour units) (PB) 

RM15 Miners carry the ten-minute Ocenco oxygen in addition the W65 CO units (PB) 

RM – Recovery Measures 

EH – Eliminate Hazard 

MH – Minimize Hazard 

PB – Physical Barrier 

WD – Warning Devices 

P – Procedures 

PST – Personnel Skills and Training 

5.7.3.4 – Step 4, Identify New Prevention Controls and Recovery Measures 

New ideas were identified by the team during the risk assessment to further reduce the ingress 

risks at the mine (Table 35). Three new prevention controls were focused on identifying well 

location (NI1 to NI3). Three ideas dealt with the potential for natural gas to be retained in 

abandoned panels (NI4 to NI6). Management will need to weigh the advantages of sealing old 

works as recommended in NI6 against the current conflicting prevention controls (PC22 and 23) 

where the old works are not sealed. Three other ideas attempt to influence the practices of future 

drilling operations near the mines (NI7 to NI9). Seven new recovery measure ideas were 

developed by the risk assessment team. Three ideas focused on improving early detection of 

natural gas ingress (NI10 to NI12). Two ideas dealt with explosion prevention (NI13 and NI14) 

and two with evacuation issues (NI15 and NI16). 

Table 35 - New ideas for mitigating risk of natural gas ingress. 

Prevention Controls 

NI1 Check the mine survey every 2000–3000 feet of advance (P) 

NI2 Reinforce the need to turn on the AutoCAD layers to show well locations (PST) 

NI3 Identify well locations before any new panel is planned or mined (P) 

NI4 Consider drilling from either surface or underground to classify, locate and determine gas pressure of old 

mines suspected to be in the area of active mining. There is a possibility that some existing extracted panels 

ventilated by the mines might have some accumulation of gas. The critical panels are the panels which are 

20 to 30 years old. (MH) 

NI5 Consider drilling and investigating existing extracted panels which are greater than some value in time (to be 

established by mine personnel based upon experience) (MH) 

NI6 Seal old mine workings to keep any accumulated gas in the old workings area even if a fall of ground 

occurred in the old workings (PB) 

NI7 Increase efforts to eliminate drilling from surface mine property in close proximity of mine and get drillers 

to utilize directional drilling (EH) 

NI8 Influence the drillers or third parties to get drillers to utilize better drilling methodologies (MH) 

NI9 Increase mine awareness of any drilling problems by either a cooperative effort with drilling companies, 

OCD (State), BLM (Federal), or combination of all the above. This needs to include gathering and 

communicating vital information on drill location, well type, and all other relevant data (P) 

74 
 

 

 

Recovery Measures 

NI10 Use new communication system to add selected gas monitoring locations at various places in the mine (WD) 

NI11 Add new monitoring sensor to new communication system at all intake shafts or all shafts to shut down fans 

if gas leak detected. (Mine personnel will determine gas trips applying experience, consequences, and all 

possibilities to determine trigger values on all gas monitors at the location that must be monitored. Trigger 

values may be different depending on location and impact to and possible consequence) (WD) 

NI12 Investigate the use of sampling pump technology to test atmosphere closer to face than the current 

continuous miner operator by placing sensor technology on CM cutter head. Same preset values are present 

for triggering action items for the gas values at 0.5%, 1% and 2% gas (WD) 

NI13 Examine the use of blast doors or isolation doors underground to reduce ignition consequences and isolate 

any event to that section of the mine (PB) 

NI14 Consider methods for automatically dropping power in the section where gas inrush occurs (MH) 

NI15 Consider the role of the initial event communicator and that person’s capability and critical decisionmaking, and include in the Emergency Response Plan (ERP). At one of the mines, there is an additional 

need because there is no cager, just a hoistman (P) 

NI16 Consider all the factors and develop understanding of all tradeoffs of egress options for series ventilation 

and the inexperience of the new mine workers. At the present time, even though both mines are connected, 

the company has not practiced egress from one mine to another (PST) 

NI – New Ideas 

EH – Eliminate Hazard 

MH – Minimize Hazard 

PB – Physical Barrier 

WD – Warning Devices 

P – Procedures 

PST – Personnel Skills and Training 

These ideas for new potential prevention controls and recovery measures should be addressed 

through the development of an Action Plan. Assuming that the information provided in the risk 

assessment was accurate, completion of the Action Plan and an increased focus on monitoring 

and auditing of the key identified controls would appear to provide an opportunity to effectively 

reduce the risk of fatalities related to gas ingress at the case study mines. 

5.7.3.5 – Step 5, Discuss Implementation, Monitoring and Auditing Issues 

The risk assessment team had a wide range of expertise familiar with the natural gas ingress 

hazards and the associated risks to the mining operation and underground workforce. The team 

was well-represented by key management personnel who had the authority, responsibility and 

experience necessary to support an MHRA. The team acted as a cohesive unit who cared deeply 

about all the employees at the mine but also as visionary people who could think outside the 

normal everyday existence at the mine. All scenarios were evaluated and completely discussed 

by all mine personnel until everyone involved in the exercise felt the matter had been completely 

evaluated. However, the team lacked representation from labor and outside expertise. 

The list of key existing prevention controls and recovery measures demonstrates that the mining 

operation has spent considerable energies thinking about this major hazard. But it is equally 

apparent from the large number of solid new ideas that more could be done. Some of the ideas 

were very practical and had a high potential for being implemented. Others seemed more 

difficult and involved the actions of outside government agencies. While it is less likely that 

these ideas could be implemented by the local mining operations, it is possible that others agents 

75 
in the company could help. This could be an example where units lower in an organization’s 

structure influence the actions of units higher in the organization’s structure through the MHRA 

process. 

At Mine G, there is a strong reliance on prevention controls (PC) classified as procedures (P) 

(Figure 29). The high reliance on procedures increases the potential for human error to play an 

important role. The new ideas were more evenly spread over the different control categories. 

76 

Number 

25 

20 

15 

10 

5 

0 

EH MH PB WD P PST 

Prevention Controls Recovery measures New Ideas 

Figure 29 - Distribution of prevention controls and recovery measures for the natural gas 

inundation risk assessment. 
5.8 – Conveyor Belt Fire Risk Assessment Case Study

Mine H is an underground room and pillar coal mine with rooms 48 to 54 inches high by 18 feet 

wide. The mine employs approximately 100 miners and operates three mining units with typical 

equipment such as continuous miners, shuttle cars and a conveyor belt system extending from 

three different working faces to the surface (Figure 30). The operator did attend a NIOSHsponsored training class but had expressed a desire to participate in the pilot project. 

Working 

Faces

Sealed
 Sealed
 

Conveyor 

Belt 

Working 

Faces
 H Mine 

Portal 

Figure 30 - Mine H layout showing the location of the conveyor belt and working faces. 

5.8.1 - Risk Assessment Scope

The objective of this risk assessment is to 1) review major hazards associated with fire potential 

on underground conveyor belts at the mine, 2) evaluate fire prevention strategies, early detection 

techniques, primary fire suppression systems, fire fighting techniques, and mine evacuation 

procedures in the context of these hazards, and 3) develop a major hazard management plan for 

this mine site. The mine uses belt air to partially ventilate the working faces. Some controls 

required by MSHA regulations are: 1) intake air monitor at the outby end of each section, 2) 

Carbon Monoxide (CO) monitors at specific intervals along the belt, and 3) a fixed fire 

protection, water deluge system at each drive set to trigger at 165° F. The mine was interested in 

examining additional controls to lower the risk of fire on its underground conveyor belt system. 

77 
5.8.2 - The Risk Assessment Team 

The risk assessment team was made up of persons employed at Mine H as well as from its parent 

company. The team members included: 

Mine superintendent 

Shift foreman 

Two miners - underground and outside supply 

Engineer 

Electrician 

Director of Safety 

Two subject matter experts 

Facilitator – MISHC (University of Queensland) 

5.8.3 - Risk Assessment 

This risk assessment case study followed the MHRA approach as outlined earlier but used a 

three-dimensional risk matrix instead of the more common 5 x 5 risk matrix. 

5.8.3.1 - Step 1, Identify and Characterize Major Potential Mining Hazards 

This exercise began by establishing the current design of the mine’s conveyor system and 

identifying risks that should be considered related to belt fire hazards. The conveyor belt system 

was broken down into segments for individual consideration. The considered segments 

consisted of individual section belts and their associated feeders and drive units (Figure 31). 

78 

4

Portal

1

3 5

6

7

8

2

2

Feeder

D1

Belt segment

D5

D2

D3

D6

D8

D7

D4

F1

F2

F3

Belt drive

Feeder 

D1 

Belt segment 

4 

Portal 

D5 

D2 

D3 

D6 

D8 

D7 

D4 

F1 

F2 

F3 

1 

3 5 

6 

7 

8 

2 

2 

Belt drive 

Figure 31 - Segments of the conveyor belt system. 

Eight individual conveyor belt segments were identified with the following characteristics (Table 

36). 
 

 

 

 

Table 36 - Characteristics of eight conveyor belt segments. 

Segments Characteristics 

1 3,100 ft of 42-inch-wide belt from portal to drive D1 with an air velocity of 490 ft/s, 

2 5,375 ft of 36-inch-wide belt from drive D1 to drive D2 and containing cribbed area with an air 

velocity of 170 ft/s, 

3 900 ft of 36-inch-wide belt from drive D2 to drive D3, 

4 700 ft of 36-inch-wide belt from drive D3 to drive D4, 

5 1,200 ft of 36-inch-wide belt from drive D4 to feeder F1 with an air velocity of 120 ft/s, 

6 4,580 ft of 36-inch-wide belt from drive D1 to drive D7 and containing drives D5 and D6 with an 

air velocity of 220 ft/s, 

7 1,820 ft of 36-inch-wide belt from drive D6 to feeder F2 and containing drive D8 with an air 

velocity of 90 ft/s, 

8 910 ft of 36-inch-wide belt from drive D7 to feeder F3 with an air velocity of 220 ft/s. 

The team then listed the types of related hazards that should be considered in the assessment. 

Fuel and heat sources are identified in Table 37. 

Table 37 - Fuel and heat sources along the conveyor belt. 

Fuels Heat sources 

Coal dust Electricity 

Timber Friction (rollers, belt, bearings, etc.) 

Grease Welding 

Paper 

Rubber (belt) 

Hydraulic Fluid 

Insulation on wires 

Plastic pipe 

Canvas 

Methane (at conveyor dump points) 

5.8.3.2 - Step 2, Rank Potential Unwanted Events 

Once the conveyor segments and hazards had been listed, the team was ready to identify the 

potential unwanted events for the entire conveyor belt system. The list of potential unwanted 

events was ranked for risk using a WRAC. The team considered each conveyor segment and 

each fire threat individually in order to systematically identify potential unwanted events. Fortyone different potential unwanted events were identified Table 38. 

79 
5

 

10 

15 

 

20

25 

 

 

30 

 

35

 

40 

Table 38 – Potential unwanted events for the entire conveyor belt system 

# Location Unwanted Event 

1 Feeder Bearing failure causes fire in coal dust 

2 Feeder Electrical short causes fire in coal dust 

3 Feeder Friction, hot motors that are above normal operating temperature set fire to wood cribs 

4 Feeder Drive chain heat sets fire to oil/grease/coal build-up and sets fire to the drive chain 

Feeder Rocks/metal bits in feeder cause sparks leading to a fire 

6 Feeder Rescuer contents exposed to air when broken in feeder, starting an exothermic fire 

7 Section Belt Tail roller failure (back from face) generates heat and ignites coal dust/grease 

8 Section Belt Misaligned belt generates friction (when it stops) and starts fire 

9 Section Belt Belt clearance problems cause rubbing and fire 

Section Belt Structure (e.g. tail piece) rub on belt causing fire 

11 Section Belt Structure/metal (e.g. rollers and structure) friction causes fire 

12 Section Belt Belt causes electricity fault on belt, (Jabcos) 110V causes fire 

13 Section Belt Electrical fault on HV crossovers for various purposes causing fire 

14 Section Belt Belt box failure /fault causes fire 

Section Belt Welding on belt structure leads to fire 

16 Section Belt Improper installation of main belt structure (hangers) leads to friction and fire 

17 Section Belt Structural failure (hung belt failure) leads to spillage/damage/friction and fire 

18 Drive Electrical fault in drive causing heat and fire 

19 Drive Scrapers wear to a point where they are metal-to-metal causing friction and fire 

Drive Misalignment of scraper causes build-up that leads to friction, heat and fire 

21 Drive Misalignment of belt causes “strings” that get heated up and catch fire 

22 Drive Welding at drive causes fire 

23 Drive Floor heave misaligns drive causing friction, heat and fire 

24 Drive Malfunction on the slip (belt control error) unit causes heat and fire 

Drive Batteries fault while driving a mantrip and catch fire 

26 Drive Bearing faults at drive generate heat and fire 

27 Drive HV box fault on belt cause fire 

28 Drive Rock from roof falls into drive area causing friction and fire 

29 Drive Hydraulic brake slip generates heat and if fluid leak then fire 

Special Fire starts in cribbed area of Segment #2 due to typical belt fire reasons (more spillage, 

harder to inspect, harder to clean) 

31 Special Float dust/trash around air locks on belt leads to fire or NOT hot spots 

32 Special Belt fire in Segment #1 has major impact on inby ventilation 

33 Special Belt fire in Segment #6 affects ventilation intake undercasts, compromising supply inby 

34 Special Section #7 transfer point roof conditions leads to rock/friction/fire 

Special Fire at undercast, Section #1 changes ventilation 

36 Special Fire at overcast, Section #1 changes ventilation 

Unusual Fuel sources 

37 

38 

39 

41 

Feeder Greasy rags, paper, housekeeping problems cause fire 

Section Belt Unnecessary fuels (greasy rag/poor housekeeping leads, coal, timber, etc.) to fire 

Drive Housekeeping problems lead to fire 

Drive Canvas fire starts 

Drive Oil sump for chain catches fire on drive 

The team applied a three-dimensional, subjective risk matrix (Table 39) to identify priority 

unwanted conveyor fire events for further consideration. This method involved selecting, for 

each identified unwanted event, the possible Maximum Reasonable Consequence (MRC) of that 

event, the Most Likely Consequences (MLC) of that event, and the likelihood of that event 

80 
 

 

 

 

occurring. The subjective ranks for each event were then defined. Table 40 shows the 12 

highest risk unwanted events. 

Table 39 – Three-dimensional risk ranking method used at Mine H. 

CONSEQUENCE 

MATRIX Most Likely Consequence (MLC) 

Maximum 

Reasonable 

Consequence (MCR) 

MFF** Almost MFF Serious Fire Minor Fire No Fire 

MFF A A B C D 

Single fatality fire A A B C D 

Serious LTI*

 A B C D E 

Avg LTI B C D E E 

Minor LTI C D E E E 

RISK RANK 

MATRIX Likelihood of Occurrence 

From the above 

Consequence Matrix 

5 - Common 

(>1 per 

week) 

4 - Likely (1 

per month) 

3 – Moderate 

(1 per year) 

2 -

Unlikely (1 

per several 

years) 

1 - Very 

Unlikely 

(almost 

never) 

A 1 2 4 7 11 

B 3 5 8 12 16 

C 6 9 13 17 20 

D 10 14 18 21 23 

E 15 19 22 24 25 

LTI* = lost-time injury 

MFF** = multiple fatality fire 

Table 40 – The highest priority risks identified by the WRAC. 

# Unwanted Event MRC MLC C L R 

1 Fire starts in cribbed area of Segment #2 due to typical belt fire 

reasons (more spillage, harder to inspect, harder to clean) 5 4 A 4 2 

2 Float dust/trash around air locks on belt leads to fire or NOT hot 

spots 5 3 B 4 5 

3 Belt fire in Segment #1 has major impact on inby ventilation 5 3 B 4 5 

4 Fire at overcast, Section #1 changes ventilation 5 3 B 4 5 

5 Electrical fault on HV crossovers for various purposes causing fire 5 3 B 3 8 

6 Large structural belt failure leads to spillage/damage/friction and fire 5 3 B 3 8 

7 Floor heave misaligns drive causing friction, heat and fire 5 3 B 3 8 

8 Malfunction on the slip (belt control error) unit causes heat and fire 5 3 B 3 8 

9 Belt fire in Segment #6 affects ventilation intake undercasts, 

compromising supply inby 5 3 B 3 8 

10 Fire at undercast, Section #1 changes ventilation 5 3 B 3 8 

11 Structure (e.g. tail piece) rub on belt causing fire 5 2 C 4 9 

12 Structure/metal (e.g. rollers and structure) friction causes fire 5 2 C 4 9 

The highest ranked risk from the WRAC was a fire starting in the cribbed area of conveyor belt 

Segment No. 2 (Figure 32). Because a fire at this location represents the highest risk to the 

mine, more time was dedicated to discussing controls for this unwanted event. 

81 
Roof fall

Belt conveyor / 

Secondary Escapeway

Primary 

Escapeway

Air flow 

direction

Stoppings

Cribbed area

Roof fall 

Belt conveyor / 

Secondary Escapeway 

Primary 

Escapeway 

Air flow 

direction 

Stoppings 

Cribbed area 

Figure 32 - Conditions within the cribbed area of conveyor belt Segment #2. 

The cribs were placed in this area to help prevent the convergence of the roof and floor. Several 

roof falls had occurred in adjacent entries and a relatively large area was being subjected to 

excessive pressure that was attempting to force the entry closed. Under these conditions, a 

standard control practice is to support the entry with standing structures to resist the roof-to-floor 

closure. Wood cribs are often used for this purpose. Drawbacks for this control include: 1) 

reduced access to the area, 2) increased air velocity as the cross-sectional area of the entry is 

effectively reduced, and 3) elevated sources of fuel (wood) to the area. 

5.8.3.3 - Step 3, Determine Important Existing Prevention Controls and Recovery Measures 

The highest risk unwanted events (top events) identified by the WRAC were selected for a much 

more detailed analysis using the BTA. The BTA analyzed the control measures intended to 

prevent the unwanted event and all consequences leading to the unwanted initiating event. The 

results of the Mine H BTA are provided in Appendix B. 

The key controls identified by the process as currently in place throughout the underground belt 

conveyor system are listed in Table 41. Fourteen existing prevention controls were identified 

and grouped into two categories. The conveyor construction controls are required by mining 

regulations or are considered Best Practices. The conveyor maintenance controls focus on 

preventive maintenance issues and good housekeeping. 

82 
 

 

 

 

 

Table 41 - Summary of existing prevention controls and recovery measures from a potential 

conveyor belt fire. 

Existing prevention controls 

Conveyor 

construction 

PC1 The conveyor is designed for the load, speed, etc. (MH) 

PC2 The conveyor is hung straight/correctly (MH) 

PC3 High-voltage cable crossovers are hung high over the conveyor (P) 

PC4 High-voltage cables run in a pipe to protect cable (PB) 

PC5 Drives are set to put dripping onto the outby belt (MH) 

PC6 Skirting and bins at transfer points that decrease spillage (PB) 

PC7 “Land mines, mouse traps, rabbit holes” that shut down the belt if excessive spillage 

is detected at transfer points (WD) 

PC8 Canvas at drives designed to hang clear of the machinery (P) 

Conveyor 

maintenance 

PC9 Mechanics inspect/repair each drive every day (P) 

PC10 Belt maintenance personnel keep all belts tracking correctly (PST) 

PC11 If a problem is found (drive seals, rollers, etc.) repairs are done (PST) 

PC12 Spills are cleaned up on back shifts (P) 

PC13 A designated person is assigned to fill drives with oil (P) 

PC14 All oil spills are cleaned up (P) 

Existing recovery measures 

Fire 

identification 

and 

communication 

RM1 Persons in the area should detect fire at feeder and other points (PST) 

RM2 CO monitors around feeders and other points are set at 5 ppm alert and 10 ppm alarm 

with audio that warns surface of possible fire (tested weekly) WD 

RM3 Persons are trained to contact the control room person if there is a suspected or actual 

fire (PST) 

RM4 If a fire is suspected, the control room person shuts off the belt and starts calling the 

sections to alert all miners (P) 

RM5 Persons in sections would notice the stationary belts or hear the phone warning 

and/or alarm (PST) 

RM6 Persons are trained to contact supervisor(s) and surface attendant(s) to clarify the 

problem (PST) 

RM7 Persons would fight the smaller fire outby (intake side) (PST) 

RM8 Persons fighting the fire would let surface attendant know if fire is beyond fighting 

(P) 

RM9 Surface attendant would let all underground know if it is time to evacuate (P) 

RM10 New employees are introduced to the mine and emergency procedures and persons 

understand procedures (PST) 

Fire fighting 

capacity 

RM11 Fixed fire suppression and fire hoses are available at the feeder and drives (MH) 

RM12 Every section and belt drive has a fire hose cart for quick delivery of hoses to fire 

location (every 15 water pipe joints there is a tap) (MH) 

Emergency 

escape 

RM13 All persons have self-rescuers (1-hr maximum) to help them get to fresh air and ride 

out (PB) 

RM14 All persons know how to get to fresh air (PST) 

RM15 More than one intake egress is available for escape (MH) 

RM16 Mine practices escapeway drill and fire fighting drill regularly (mock drill) (P) 

PC – Prevention Controls 

RM – Recovery Measures 

EH – Eliminate Hazard 

MH – Minimize Hazard 

PB – Physical Barrier 

WD – Warning Devices 

P – Procedures 

PST – Personnel Skills and Training 

83 
 

Sixteen existing recovery measures focused on fire identification and communication, fire 

fighting capacity, and emergency escape controls were identified. Here again these controls 

represent a combination of complying with mining regulations and Best Practices. 

5.8.3.4 - Step 4, Identify New Prevention Controls and Recovery Measures 

As the risk assessment team identified existing prevention controls and recovery measures 

associated with a conveyor belt fire, new ideas were proposed to help further reduce risk. 

Thirteen new ideas were identified, six related to prevention control and seven related to 

recovery measures (Table 42). 

Table 42 – New ideas proposed by the risk assessment team for preventing or recovery from a 

conveyor belt fire at Mine H. 

New prevention 

control ideas 

NI1 Conveyor Monitoring / Inspection - combine the role of examining and cleaning 

the belt (P) 

NI2 Investigate infra-red cameras and thermometers to detect hot spots (WD) 

NI3 Conveyor Cleaning – install a water valve outby the cribbed area, have weekly 

wash downs (P) 

NI4 Install a knee wall to deflect water and collect fines (MH) 

NI5 Use hydraulic jacks rather than wooden cribs as supplemental support when roofto-floor convergence is a problem. Consult NIOSH “STOP” program for 

assistance (MH) 

NI6 Conveyor Construction – survey and mark drives for conveyor hanging, plan HV 

crossovers, and cut bottoms in new drive areas (MH) 

NI7 Conveyor maintenance - ensure splices are square, complete an SOP for splice 

inspection (P) 

NI8 Self-Rescuers – communicate the related fire source risk and provide locations 

on equipment for rescuers (PST) 

New recovery 

measure ideas 

NI9 Fire Fighting Plan – review the fire fighting plan to ensure the key actions are 

understood, developing a control room check list for actions; define the MSHA 

interaction and consider an emergency info “sticker” for personnel (P) 

NI10 Fire Identification - supplement CO monitoring with smoke monitoring in belt 

headings (WD) 

NI11 Fire Communication - investigate technology to notify persons to leave the mine 

(WD) 

NI12 Fire Fighting Capacity - analyze fire fighting capability and hang ribbons on belt 

line for fire taps and hose locations (P) 

84 

Two new prevention control ideas (1 and 2) focused on the #1 ranked risk – fire along the 

conveyor belt in the cribbed section of Segment #2. The combination of using infra-red cameras 

and thermometers to detect hot spots and better control of coal fines were viewed as significant 

controls to further mitigate risk. New idea 3 focused on eliminating the wood fuel supply from 

future sites where roof-to-floor convergence might occur. The NIOSH program STOP (Support 

Technology Optimization Program) is a design tool that can be used to help investigate different 

supplemental support options (http://www.cdc.gov/niosh/mining/products/product99.htm). New 

idea 4 focused on future conveyor construction, proposing to eliminate many of the hazards 

through better construction techniques. New idea 5 relies on an SOP to ensure that cable splices 

are done to standards. New idea 6 deals with a relatively rare phenomenon – an SCSR 

mistakenly entering the conveyor belt feeder. This has happened only once at this mine, but the 

incident resulted in a hot fire that lasted for many minutes. 
NI13 Fire Escape – train all to use optional alternate (3rd emergency egress) (PST) 

NI14 Specific to the Cribbed Area in Segment #2- install additional phone and fire 

suppression over the conveyor belt in this area (MH) 

NI15 Fire Event Simulation - use event simulation to test response to fire (MH) 

NI – New Ideas 

EH – Eliminate Hazard 

MH – Minimize Hazard 

PB – Physical Barrier 

WD – Warning Devices 

P – Procedures 

PST – Personnel Skills and Training 

The seven new recovery measure ideas covered a range of emergency response issues associated 

with detecting a fire (NI8), communicating its occurrence and location (NI9), fighting the fire 

(NI10), and escaping safely from the mine (NI11). The team had one new idea (NI12) specific 

to the cribbed area in Segment #2. New ideas 7 and 13 focused on improving the existing fire 

fighting plan through a control room checklist and event simulations. 

5.8.3.5 - Step 5, Discuss Implementation, Monitoring and Auditing Issues 

The existing prevention controls and recovery measures are obviously keys to reducing the risk 

of a conveyor belt fire and, therefore, should be reinforced, monitored and audited with priority. 

The new ideas were compiled into an Action Plan with the recommendation that each item be 

evaluated within a specific time frame and a decision made by management as to which would 

be implemented by the mine. Lastly, a presentation was made by the risk assessment team to 

mine management stressing the above points. 

The existing and new prevention control and recovery measures identified with the BTA fell 

largely within the mitigation and tolerance range of hierarchy responses to the identified hazards. 

The team did not identify any controls that would have eliminated the hazard entirely. If this 

mining process were not used at this mine, many of the risks analyzed would have been 

diminished; as one example, using belt air to ventilate the working faces is responsible for many 

of the mine’s conveyor belt fire high-consequence events. It is difficult for an MHRA to 

consider hazard elimination when the mine is mature and the action of hazard elimination might 

produce other unfavorable mining conditions. The high-voltage power cables crossing the 

conveyor belt line is another example of the difficulty in hazard elimination actions. Here 

actions focused on ways of mitigating or tolerating the risks associated with this hazard. 

A number of the existing controls discussed by this risk assessment team identified mitigation 

techniques (MH and PB, see Figure 33). Also, five new ideas were classified as controls to 

minimize hazards (MH), where some technology would independently aid in preventing a fire or 

minimizing the resultant losses if a fire were to occur. If a fire occurred and recovery measures 

(RM) were needed, there was a high reliance on procedures (P) and personnel skills and training 

(PST) (Figure 33). 

85 
0 

1 

2 

3 

4 

5 

6 

7 

8 

Number 

EH MH PB WD P PST 

Prevention Controls Recovery measures New Ideas 

Figure 33 - Distribution of prevention controls and recovery measures for the conveyor belt fire 

risk assessment. 

86 
5.9 – Longwall Gate Entry Track Fire Risk Assessment Case Study 

Mine I is a large underground longwall coal mine. The mine employs over 400 miners and 

operates three longwall and six continuous miner sections. The mine has track transportation 

throughout main headings and into development panels (Figure 34). The three-heading longwall 

development panel has one entry that has rails installed to the face area. This heading is also an 

intake for the fresh air ventilation to the working face and is the primary escapeway for miners. 

The belt entry contains the conveyor belt with a neutral split of air. The return entry contains the 

exhausted air from the working face and is this section’s secondary escapeway. The major 

hazard evaluated at this site is a fire on the track entry of a longwall development panel, where 

smoke from the face travels to the working face obstructing egress through the primary 

escapeway. 

Main headings 

Longwall development panel 

Expanded sect panded section 

Return entry 

D D D 

Track entryck entry Track 

D D 

Belt entrBelt entry Belt 

Figure 34 - Site conditions at Mine I showing the 3-entry development panel with direction of air 

flow. 

5.9.1 - Risk Assessment Scope 

The mine decided to review the risk related to fire hazards in the track entry of a longwall 

development panel considering the operation of relevant equipment and other variables. The 

operator did attend a NIOSH-sponsored training class and had expressed a desire to participate in 

the pilot project. The project objectives were scoped at the training session. 

87 
5.9.2 - The Risk Assessment Team 

The team was made up of persons employed at Mine I as well as from the parent company and 

contained the following representatives from the workforce: 

 Assistant mine superintendent 

Master mechanic 

Safety supervisor 

Fire prevention manager 

Corporate manager of fire prevention and mine rescue 

Motorman (labor) 

Miner operator (labor) 

Two subject matter experts 

NIOSH Observer 

Facilitator – MISHC (University of Queensland) 

5.9.3 - Risk Assessment 

The longwall track entry fire risk assessment did not use all five steps of the MHRA. A formal 

risk ranking of all potential unwanted events was not performed. This is partly due to the short 

time frame allotted for this activity and the desire to focus on a robust examination of prevention 

controls and recovery measures. It is also likely due to the potential difficulty in determining 

difference in the likelihood of occurrence of identified unwanted events. 

5.9.3.1 - Step 1, Identify and Characterize Major Potential Mining Hazards 

The first step in the risk assessment involved identifying and understanding the hazards related to 

a fire in the track heading. The team brainstormed the potential heat sources and fuel sources 

that might be available mid-panel to create a fire (Table 43). 

Table 43 - Fuel and heat sources found within a longwall track entry. 

Fuel sources Heat sources 

Materials on flat cars Locomotive and mantrip motors 

Some flammables on the locomotive, 

paint, coal dust, grease, oil, hoses, 

batteries, garbage 

Locomotive Batteries 

Stores in cross-cuts High-voltage equipment, power cables 

Coal Welding and cutting

 Compressors 

 Rock dusters 

The team then decided to review risks related to a fire due to any source listed in Table 43 and 

located mid-panel within a track entry (intake air) in a development panel. It also agreed to the 

potential important characteristics listed in Table 44. 

88 
 

Table 44 - Important longwall track entry characteristics to be considered in the risk assessment. 

Track entry characteristics 

1 Any variables or variations in development panel, e.g. dips 

2 Equipment, primarily battery operated locomotives, portal buses (mantrips), rock dusters and compressors 

3 Smoke conditions at the face would be dependent on the location of the fire, i.e. fire outby the face and 

near the main entry would fill both the fresh air intake and the track entry intakes with smoke, while a fire 

close to the face and far from the mains would only fill the track entry intake with smoke 

4 Welding/cutting (hot work) activities sometimes occurred in the track entry intake 

5 High-voltage cables were located in the track entry intake 

5.9.3.2 - Step 2, Rank Potential Unwanted Events 

After discussing and ensuring understanding of the above hazards, the team decided it did not 

have sufficient time or information to explore a risk ranking exercise with the WRAC tool. 

Instead, the team focused on identifying a list of ten consequences of a longwall track fire (Table 

45). 

Table 45 - List of acceptable and unacceptable consequences from a longwall track fire. 

 Consequence Risk rank 

1 Loss of power to panel and face ventilation lost 

Acceptable 

2 Communication line is lost 

3 Roof fall in heading due to heat 

4 Discharge water line cut 

5 Compressed air line lost 

6 A small fire becomes a big fire 

Unacceptable 

7 Persons affected by smoke at face 

8 Person trapped by smoke 

9 Persons trapped or overcome (can’t escape) 

10 Fire ignites gas in panel 

The team decided to combine the important characteristics of a longwall development track entry 

(Table 44) with the list of high-consequence unwanted events (Table 45) to rank the risk of a 

longwall track entry fire. The four highest risks are listed below: 

1. Fire on a locomotive or portal bus (mantrips) 

2. Electrical high-voltage fire 

3. Welding or cutting fire (hot works) 

4. Rock duster battery vehicle / compressor fire 

5.9.3.3 - Step 3, Determine Important Existing Prevention Controls and Recovery Measures 

The BTA method was used by the team to review and discuss the current controls in place to 

reduce risks related to the four high-consequence hypothetical fire events listed above. The 

complete BTA analysis is shown in Appendix A. This risk assessment compiled an extensive list 

of priority existing controls for event prevention and consequence minimization. Fifty-five 

existing key prevention controls (PC) and thirty-four existing key recovery measures are listed. 

Over 60% of the existing prevention controls were directed at the fire on a locomotive or portal 

bus potential unwanted event, demonstrating the mine’s high concern with this risk. 

89 
An analysis of the 89 existing prevention controls and recovery measures provides a unique 

opportunity to examine the characteristics of the controls used by this mining operation. The 

character and effectiveness of controls was discussed under the topic of the hierarchy of effective 

controls (Section 4.4). The hazards unique to this risk assessment were associated with the use 

of a three-entry longwall gate entry design. The track entry was a designated fresh air entry. If a 

fire occurred in this entry, smoke would eventually make its way to the working face. The 

hazards associated with using track air to ventilate the working faces are the key component of 

this risk assessment. Therefore, if the need to use the track air current to ventilate the working 

face is eliminated then the hazard (EH) is eliminated. The most effective control, hazard 

elimination, was not discussed during this risk assessment. 

All of the 89 controls fall in the other control categories: minimize hazards (MH), physical 

barriers (PB), warning devices (WD), procedures (P), and personnel skills and training (PST) 

(Figure 35). At this mining operation, there is a reliance on procedures (P) to mitigate the risks 

associated with the longwall gate entry track fires. Fifty-four percent of the existing prevention 

controls and recovery measures were classified as procedures (P). The rest of the controls were 

distributed, somewhat evenly, among the remaining categories. Most of the prevention controls 

that were categorized as minimizing the hazard (MH) are focused on the machines being 

designed and built to specifications that incorporate distinct safety features, i.e. enclosed 

compartments, fuses, breakers, de-energizing capabilities, etc. Also, more warning devices 

(WD) are used as recovery measures than prevention controls. 

35 

30 

25 

20 

15 

10 

5 

0 

Number 

EH MH PB WD P PST 

Prevention Controls Recovery measures New Ideas 

Figure 35 - Distribution of prevention controls and recovery measures for the longwall gate 

entry track fire risk assessment. 

Many of the existing controls could be grouped by the issues they addressed. For example, the 

controls associated with the locomotives and portal buses can be grouped by design issues, 

maintenance issues and operational issues, as detailed below. 

Locomotive and Portal Bus Design Issues: The locomotives and portal buses are 

designed to standards with fuses, breakers and resistors. Many locomotive cables are 

protected in conduits. Radio-controlled communication is available on the locomotive to 

obtain assistance/advice about abnormal operations. Battery charging issues are 

minimized because the locomotives are always charging the batteries when in contact 

with a trolley wire in main headings. Also a gage indicating charge level is located in 

90 
operator compartments. Resistors are closed-in, blocking trash and other fuels from these 

heat sources. Fans are installed on some locomotives aiding in additional cooling. A red 

light indicator tells the operator when the brakes are on. Normal braking is electrical so 

overheating of the other brake is unlikely. All locos are fitted with heat sensors and 

manually initiated fixed fire suppression and hand-helds (20 lbs). Fire extinguishers are 

located within easy reach of the locomotive operator. 

Locomotive and Portal Bus Maintenance Issues: All locomotive and portal buses are 

subjected to weekly maintenance checks. Mine personnel inspect new equipment and 

rebuilds before they are used. In addition, a state electrical inspector certifies that all 

major rebuilds are completed to standards. Battery maintenance includes cleaning, 

watering, checking for dead cells, etc. and all battery rebuilds are done to a mine 

specification. Fixed and hand-held fire equipment used on this equipment are checked 

regularly. Weekly inspections are completed to check for faults or discharge in the fire 

alarm system. Finally, a certified contractor does the maintenance inspection on fire 

suppression system every six months. 

Locomotive and Portal Bus Operations Issues: Locomotive loads are always at least 10 

ft from heat sources and only hydraulic oil and wood fuel sources are transported. Load 

guidelines are applied at the mine to avoid oversized/shifting loads that might derail the 

locomotive. Any explosives are hauled separate from all other supplies and transported 

in specialized containers. Operators receive special training and are required to perform 

pre-operation checks, i.e. test brakes, tram, check batteries and fire extinguishers. Safe 

Work Instruction and Best Practice teams sometimes observe pre-operations inspections. 

Operators are trained to open breakers and take plugs off batteries if there is a short, and 

if that does not work then the main lead is disconnected. Operators are aware of hot 

resistors and will stop operations and let resistors cool if overheated. Operators will 

smell for brake heat and look for abnormal operation, e.g. low power. Abnormal 

operation is reported to the supervisor and the maintenance shop. Supervisors know the 

capability of individual motor operators and they select competent operators for 

heavy/difficult loads. Operators are trained in the use of hand-held fire extinguishers 

every 2 years. 

The rock duster and air compressor also had specific existing controls. 

Rock dusters and air compressor issues: the Rock dusters and air compressor are 

designed to standard and inspected before underground use. Dedicated crews take care of 

charging and inspecting this equipment, including an operator being in the area during 

operation. There is a weekly electrical check of the equipment by the maintenance 

department. The rock dusters and air compressors have fixed, automatic and manually 

operated fire suppression systems directed at the battery areas. There are weekly 

inspections to see if the fire suppression system is faulted and if an alarm occurs, does it 

discharged. A certified contractor does the maintenance inspection on the fire 

suppression system every 6 months. All rock dusters and air compressors have a 

mounted hand-held fire extinguisher. Locomotive operators check the oil level in 

compressors. 

91 
Within the longwall gate entry environment, several other important issues are highlighted by the 

quality of the existing controls applied to them, as follows. 

Track Issues: Rail maintenance program requires a given area of track to be inspected 

every shift. All tracks are installed and maintained to standards. The mine examiner 

examines the track during the pre-shift examination. Locomotive operators report any 

track issues to their supervisor. 

High-Voltage Electrical Apparatus Issues: High-voltage cables are shielded and some 

are guarded and are located in rib/roof corner, reducing likelihood of damage. Circuit 

breakers/GFCI/pilot circuits are installed to protect the system form overload and fault 

fires. Monthly tests are done and recorded on these devices and on the jackets and 

insulation. Cabling is hung to regulatory requirements. The high-voltage system is 

designed to de-energize quickly (GFCI, etc.). 

Housekeeping Issues: Each shift is responsible for cleaning up trash in their area. Trash 

is bagged and put on empty car. The locomotive operators pick up trash in outby areas 

around tracks. 

Cutting and Welding: The mine has strict procedures for cutting and welding 

underground. Qualified persons must be present when cutting or welding to make 

methane gas checks and checking the area before they leave. Hand-held detectors are 

part of welding equipment used underground. Fire protection and rock dust is included in 

the welding and cutting procedure. Where possible a charged water line is also taken to 

the cutting or welding area. 

Several important issues related to existing recovery measure were identified by the risk 

assessment team. 

Gas Monitoring Issues: There is a real time continuously monitoring system that detects 

carbon monoxide (CO). Measurement points are located every 2500 feet in track 

heading. This system is linked to the underground bunker and outside surface hoist 

house where it is continuously monitored by a designated person. The system alarms at 5 

ppm CO (alert) + 10 ppm CO (alarm). In addition, the system has a malfunction alarm. 

A designated person reacts to the alarms by 1) notifying shift foreman and other persons 

in affected area with both underground radios and telephones, and 2) checking CO 

detector. Also, there is a CO alarm at the conveyor tail (10 ppm CO) in the panel. 

Fire Fighting Training Issues: Locomotive operators are trained in fire fighting every 

two years. Persons are trained that an air line can be charged to a two-inch water line to 

provide fire fighting water to the track heading. There is also a return water line that can 

supply water to fight a fire until air pressure to the face is lost. The mine has a designated 

Responsible Person (RP) who is notified when a fire occurs. All persons evacuate the 

mine if a big fire is identified. RP makes decisions about actions to be taken 

underground to fight fire, change ventilation, etc. 

92 
 

 

 

Emergency Egress Issues: Persons on face are trained to put on M20 self-rescuers, leave 

the panel if dense smoke is in the intake and meet at the power center, grab an extra 

SCSR, tag together, go to return, and use lifeline in return to egress the section. The M20 

has a 20-minute supply of oxygen. There is a cache of 1-hour SCSRs at the load center 

and on mobile equipment, and caches are located 5700 feet in the intake track entry and 

5700 feet in the return but staggered every 2850 feet down panel (staggered). Lifelines 

lead to caches and there are two cones on line to alert that a door or SCSR cache is 

present. There is a practice egress using the escapeways every quarter (alternating 

between the intake and return entries). Caches are located in cross-cuts with doors in 

stoppings. Persons are trained to take an extra SCSR. Per MSHA requirements 

barricading materials have been located in panels and persons have been made familiar 

with methods of building barricades. There are trained and qualified mines rescue teams 

available to attempt underground rescue. The Mine Emergency Response Plan includes 

external and internal communication, external medical services, family notification, 

security, etc. 

5.9.3.4 - Step 4, Identify New Prevention Controls and Recovery Measures 

Fourteen new ideas were identified by the team during the risk assessment to further reduce the 

longwall track fire risks at the mine (Table 46). The particular BTA that was responsible for 

each new idea is provided in Appendix A (Table 56 and Table 57). Seven new ideas address 

prevention control measures and seven recovery measures. The hierarchy control categories for 

the new ideas are also dominated by procedure (P) controls (Figure 35). 

Table 46 - New prevention control and recovery measure ideas for the longwall track fire event 

organized by category. NOTE that the new idea numbers (NI) correspond to the new ideas listed 

in the BTA for the risk assessment (Table 56 and Table 57). 

Design NI7 Investigate changing or modifying loco resistors to perform under load without 

overheating (MH) 

NI9 Investigate whether fixed fire suppression can be located over/at compressor (PB) 

NI10 Put one joint of fire hose on loco to be carried on the track jeep at all times (P) 

Maintenance NI1 Reinforce and follow the requirements of the maintenance program for batteries, consider 

checklists/verification that it is being followed (P) 

NI3 Add checking gauge accuracy in the battery maintenance program (WD) 

Operations NI2 Investigate defining a specific percentage battery charge that is minimum to enter panel 

(P) 

NI4 Investigate whether there is an identifiable level of complexity/experience for major 

loads, thereby creating a list of heavy load operators (P) 

NI5 Reinforce the need, during pre-operation inspection, to remove any baking soda that has 

been used to absorb water on batteries so that it doesn’t become a conductor (P) 

NI6 Add checking inside the loco resistor area (lift lid) for any combustibles to pre-operation 

inspections (NOTE that dust can get into resister compartment) (P) 

NI8 Make operators aware that, if possible, when there is a small fire or smoke from a 

loco/mantrip/rock duster there may be an opportunity to reduce/stop smoke to the face by 

putting equipment into a switch/spur track and open man-door into the return heading to 

short circuit into the return (P) 

93 
Fire and 

Emergency 

Response 

NI11 Add clarification to ER training, re: egress in light smoke – i.e. if light smoke in intake 

use transportation to exit as far as possible* then cross to return to egress [* smoke is too 

dense to see ahead] (P) 

NI12 Make sure the caches are located in cross-cuts with doors in stoppings (P) 

NI13 Reinforce the need to put self-rescuer or, if closer by, don SCSR as soon as any smoke is 

detected (issue: may get worse and easier/safer to don the SCSR now) (PST) 

NI14 A method should be developed to access stopping doors at caches to check if intake is 

fresh air so that a person can remain attached to lifeline and/or team. The method should 

be included in 90-day ER training. (P) 

NI – New Ideas 

EH – Eliminate Hazard 

MH – Minimize Hazard 

PB – Physical Barrier 

WD – Warning Devices 

P – Procedures 

PST – Personnel Skills and Training 

5.9.3.5 - Step 5, Discuss Implementation, Monitoring and Auditing Issues 

Assuming that the information provided in the risk assessment is accurate, an increased focus on 

monitoring and auditing of the key identified controls would appear to provide an opportunity to 

effectively reduce the risk of fatalities related to underground fire in the track entry at Mine I. 

The risk assessment team identified 89 existing controls and 14 new ideas. Procedures dominate 

both the existing and new prevention controls and recovery measures for this mine site. 

Procedures are known to have a potential for human error. This requires a thorough examination 

and audit effort. This mining operation will address these needs through a Safe Work Instruction 

program and Best Practice teams that periodically observe the quality of many existing controls. 

At the end of the risk assessment, the 14 ideas for new potential controls and recovery measures 

were submitted to mine management in the form of an Action Plan (Appendix B). The Action 

Plan lists each new idea and contains additional columns to identify who will investigate the 

idea, when the investigation will be completed, and what specific action will be required. 

94 
5.10 –Change of Mining Method Risk Assessment Case Study 

A risk assessment was performed at an underground metal mine (Mine J) to investigate major 

hazard potentials associated with the management of change. Mine J operates in a steep, near 

vertical, ore body with the captive (raise access) cut-and-fill stoping method (Figure 36). In this 

method, the ore is mined by successive flat slices, working upward. After each slice is blasted 

down, all broken ore is removed, and the stope is filled with waste up to within a few feet of the 

back (roof) before the next slice is taken out. The term captive implies that access to the stope is 

solely through vertical access raises that are confined to that stope. During production, one of 

these raises can contain ore. This method requires three miners per stope. 

The scope of the risk assessment was limited to those events that would have the potential to 

fatally injure the miners working in the captive stopes. The primary change related to the move 

from mechanized (drift access) cut-and-fill to captive stoping is considered to be 1) the 

occasional limitations on escape from the work area to a single ladder-way in the access raise, 

and 2) the occasional requirement of miners to work under unsupported brows. Also, the captive 

cut-and-fill stoping method relies more on miner hand-work and less on mechanized equipment 

than the previous mining method. Members of the mine staff attended a NIOSH-sponsored 

MHRA training course and expressed an interest in participating in the study. 

Breast-down brow

Entrance to 

ore raise

Stope access 

development

Cribbing

Entrance to 

access raise

Raise-up 

slot

Access 

raise

Stope

Backfill 

production 

drifts

Ore raise

Production drift 

development Breast-down brow 

Entrance to 

ore raise 

Stope access 

development 

Cribbing 

Entrance to 

access raise 

Raise-up 

slot 

Access 

raise 

Stope 

Backfill 

production 

drifts 

Ore raise 

Production drift 

development 

Figure 36 - Diagram of Captive Cut-and-Fill mining method. 

The captive cut-and-fill stoping method is a complex practice that has been widely used around 

the world to skillfully respond to changing conditions within the ore body. The widths of the 

mining space can shrink and expand in concert with the ore thickness. In the last few decades 

some mining operations have used a more mechanized stoping method with tire-mounted jumbo95 
 

boom style face drills to blast the mine opening and load-haul-dump (LHD) vehicles to 

efficiently move the muck (broken ore) out of the production stope. The design of the stope is 

highly dependent on the size and maneuverability of the mobile equipment. When the ore body 

falls below a certain thickness, mechanized stoping can become inefficient. This is the case with 

Mine J. 

While the captive cut-and-fill stoping method lacks large mobile mechanized equipment, there is 

still a strong reliance on a wide range of mining equipment. Every stope has a complement of 

electric slushers5

5

 A slusher is a blade or bucket that drags the broken ore within the production drift to the dump point at the top of 

the ore raise. 

 air tugger6,

6

 A tugger is a small, semi-portable hoist, powered by compressed air or electricity, to raise supplies and equipment 

within the access raise. 

jackleg drill and a mucker.7

7

 A mucker is the device that loads the broken rock out of the ore raise and into haul trucks for transportation out of 

the mine. 

96 

, There is also a wide range of electric 

fans, tools, lights, and phones that require a transformer and hundreds of feet of wire. 

Compressed air and water are also brought into the stope. In addition, each stope is serviced by 

diesel haul trucks and tractors and an explosives magazine. 

5.10.1 - Risk Assessment Scope 

The scope of this risk assessment is to identify the major hazards and risk potential associated 

with the change of mining method to captive cut-and-fill stoping and to evaluate existing 

prevention controls and recovery measures for adequacy in controlling identified risks. A 

change of mining method risk assessment represents the most complex MHRA because it can 

consist of a number of smaller related risk assessments. Each hazard examined identified 

existing prevention and response actions that were considered as important to maintain. Further 

discussions of what other actions might be undertaken to further reduce the likelihood of the 

subject event occurring and to improve response should it occur were also documented for 

management review of the concepts developed. In some cases a work process flow chart of the 

specific portion of the mining cycle being examined was developed so that the group could 

consider where prevention and early response actions could best be placed. A significant amount 

of time must be spent considering the new mining process, and the composition of the risk 

assessment team will change as different hazards require specialized knowledge bases. The 

output is information to assist Mine J in the development of the approach to captive cut-and-fill 

mining so that risks are managed to a level that is acceptable. 

5.10.2 - The Risk Assessment Team 

The risk assessment team was made up of persons employed at Mine J, as well as from its parent 

company. The initial team members included: 

Maintenance superintendent 

Maintenance foreman 

General foreman 

Shift foreman 
Two captive stope miners 

Rock mechanics engineer 

Safety coordinator 

Director of safety 

NIOSH matter experts 

NIOSH observer 

Facilitator – MISHC (University of Queensland) 

The risk assessment team composition changed as the team focused on additional hazards or 

different work processes. 

5.10.3 - Risk Assessment 

The structure of the risk assessment methods used was a multiple layered approach beginning 

with a semi-quantitative risk ranking exercise, using a WRAC, to prioritize hazards for further 

examination. The eight highest priority risks were then examined in more detail utilizing the 

BTA and work process flow chart methods. This risk assessment required that any hazard 

suspected to be associated with the new mining method needed to be evaluated. 

5.10.3.1 - Step 1, Identify and Characterize Major Potential Mining Hazards 

For a change of mining method risk assessment, there is a potential for numerous major hazards. 

Some of these hazards exist within the current mining method, others are specific to the new 

mining method and, as such, may be new to the mine. In this case, the hazards can only be 

identified and characterized after the mining process has been segmented into distinct phases. 

This first operation was completed by the first team over the course of one day where the captive 

cut-and-fill stoping method was broken down into 11 phases with an internal loop for the 

repetitive portions of the cycle (Phase 6 to 10). 

1.	 Stope access development 

2.	 Vertical raise preparation (two raises per stope) 

3.	 Vertical raise-up slot (locally referred to as a beanhole) 

a.	 Jackleg raise mining 

b.	 Longhole raise 

4.	 Preparation for ore production by lining the vertical raise with wood cribbing 

5.	 Production drift development 

a.	 First connecting vertical raises (I-drift) 

b.	 Develop drift to its full horizontal length of ~ 200 ft (sill drift) 

6.	 Raise-up a slot in the production drift 

7.	 Place and decant sand fill in production drift, and relocate equipment 

8.	 Breast-down the brow along the production drift 

9.	 Extend cribbing in vertical raises in preparation of placing sand fill in the 

production drift 

10.	 Reset equipment for next raise-up of the production drift [return to Phase 6 to 

repeat 6 to 10 for 200 ft vertically (~20 cuts)] 

11.	 Remove equipment from stope. 

97 
 

 

 

 

 

Next the team listed the types of related hazards that should be considered (Table 47). 

Table 47 - Hazards associated with captive cut-and-fill mining. 

Potential hazards Where When 

1 Ground fall Production drift Production from drift, raise-up slot, 

breast-down 

2 Inrush of previously 

place sand fill 

Production drift, access raise, 

stope access drift 

Placing and decanting sand fill and 

relocating equipment 

3 Electrocution Stope and stope access drift Energizing, splicing, moving, etc. 

electric wires 

4 Air pressure Stope access drift, access raise 

and production drift 

Connecting air lines, pumping sand 

fill and operating drills 

5 Water pressure Stope access drift, access raise 

and production drift 

Connecting water lines, pumping 

sand fill and operating drills 

6 Diesel / hydraulics Stope access drift Hydraulic failure leads to fire on 

diesel equipment 

7 Explosives Production drift, breast-down, 

raise-up slot, dynamite magazine, 

transporting in access raise 

Transportation, placing in blastholes, 

pre-detonation and explosives that 

failed to detonate. 

8 Falls (drawpoints 

gravity) 

Ore raise and access raise 

openings 

When moving through or 

approaching access or ore raises 

9 Equipment temperature Stope and stope access drift Overheating of diesel engines or 

electric motors 

10 Slusher or tugger cable 

tension 

Production drift Overstressed or over worn cables 

used during slusher or tugger 

activities 

11 Slusher setup and 

anchor 

Production drift Production from drift, raise-up slot, 

breast-down 

12 Mechanical energy of 

equipment 

Stope and stope access drift When operation or preparing to 

operate diesel, electric, hydraulic or 

compressed air equipment 

13 Dangerous gasses Raise-up slot, production drift Formation gases released during 

drilling or blasting or dangerous 

gases associated with diesel 

particulate, blasting or fires 

14 Slip / trip Stope and stope access drift Moving over uneven and rocky 

surfaces or tripping over equipment 

Once the mining phases and hazards were identified, the team was ready to apply risk analysis 

methods. 

5.10.3.2 - Step 2, Rank Potential Unwanted Events 

The team considered each mining phase and each hazard individually in order to systematically 

identify potential unwanted events. The WRAC produces information about the mining phases 

and specific unwanted events. Eighty-three potential unwanted events were identified (Table 

48). Every mining phase contained at least one and most had many events. The number and 

significance of these events attest to both the complexity of the problem and the collective 

knowledge of the team. 

98 
 

 

 

 

Table 48 - Priority listing of potential unwanted events associated with phases in the captive cutand-fill stoping method at Mine J. 

Mining phases Potential Unwanted Event 

Methane due to drilling into pocket 

Cable bolts come out before grouting 

Loss of long hole steel causes impalement 

Drilling into a miss hole with explosives causes explosion 

Major fall of ground while bolting 

Stope access Blast into diamond drill hole 

development (1) Manual handling of electric cables 

Mucking into a misfire causes explosion 

Fall of ground between supports 

Equipment fire 

Crushed by mobile equipment 

Explosion occurs from manually handling explosives 

Raise preparation (2) Improper location under roof causes fall 

Initial raise Drill into water / gas source causes falls 

development - jackleg Miss hole hit by drilling in bean hole causes explosion 

(3a) Rockfall in bean hole w / jackleg 

Initial raise Longhole breaks through into lower level where people are working 

development - long 

hole (3b) Longhole blasting breaks through into where people are working 

Welding chutes (truck) 

Electrocution occurs when welding due to water exposure 

Lining the vertical 

raises with wood 

cribbing (4) 

Rigging failure causes release of tension 

Timber failure occurs 

Person crushed against ribs when positioning equipment 

Person with less than adequate familiarity accesses stope area 

Person hit by material falling down skip shaft 

Fire in the intake sends smoke into stope 

Miss holes in I drift explode when drilling 

Electrical shock due to damage during blasting 

Gasses encountered re-entering area after blast 

Production drift 

development - I drift 

(5a) 

Fall of ground during first couple rounds 

Person falls into chute when mining nearby 

Person knocked back into chute by blow pipe 

Equipment fire in the intake while person is in I drift / sill 

Person hit by rock fall while accessing unsupported ground to set up slusher 

Persons not familiar with jacklegs operate that equipment 

Person falls into holes due to incorrect covers 

Production drift 

development - sill 

drift (5b) 

Electrical fault occurs when plugged into wrong power source 

Person hit by parts of mucker if hits rib 

Equipment fire at face 

Protruding ground support when operating mucker 

99 
 

 

 

 

 

 

 

 

 

 

Raise-up slot (6) 

Hang-ups cause cave-in or drill injuries 

Rock bursts (strain bursting) during raise development 

Gasses cause exposure to bad air after access to raise-up 

Water air pressure release hits person 

Loss of floor (muck / staging) pulls person in 

Loss of floor occurs in new raise-up due bulkhead or mucking out 

poor location of eye leads allows equipment to fall in raise 

Fall from height 

Person injured due to skip problems having impact on man access 

Miss holes after raise-up causes unsupported ground 

Persons exposed to unsupported ground in crossing over muck pile 

Damage to ground support while slabbing 

Person hit by roof fall when trying to support raise-up 

Failure to decant causes crib failure later in mining 

Person gets stuck, sinks or asphyxiates while accessing fill area to repair line 

Release of pressure when line plugs 

Place and decant sand Miner filling sand fill falls into raise when cribbing fails 

fill (7) Decant into ore pass causes muck to blow out 

Person working alone when sand filling 

Decant water causes failure in another area as it runs out of stope 

Person falls off timber while filling down manway or into fill 

Loss of control of timbers causes crushing 

Lining the raise-up 

with wood cribbing 

(8) 

Person falls into chute 

Person hit by timber when dropped down man access / bean hole 

Rigging failure occurs when relocating equipment and persons hit 

Person falls off timber >10' 

Person falls into beanholes when installing timber sets 

Early initiation of blast occurs when person in manway due to safety fuse 

Brow rounds blows rock onto manway 

Unexpected geologic structure causes ground problem 

Offset / jogs in stope causes stresses and other problems 

Breast-down the brow 

(9) 

Mistimed blast in reef causes impact in other area of mine through to another level 

People in other level when mining blasts / accesses area 

Survey error leads to mining out in another level not as planned 

Hanging walls burst / slab out 

High stress occurs in pillars affecting stope ground / access 

Access sand filled stope and collapse occurs 

Inadequate crown pillar size leads to collapse when another level accessed 

Reset equipment for 

next stope (10) 

Electric shock occurs in set equipment when setting up 

Equipment not set in right location and / or set insecurely 

Persons injured relocating slusher under its own power (not hooked up correctly) 

Remove equipment Cable failure lowering equipment causes accident 

from stope (11) Failure of chain fall causes persons to be hit by equipment 

Once all phases of captive cut-and-fill stoping are considered, each unwanted event is risk 

ranked using the cooperating company’s risk matrix (Table 49). 

100 
 

 

 

 

Table 49 - Risk Matrix used by cooperating mining company. 

Likelihood of Occurrence 

1 – Highly 

unlikely 

2 – Not 

expected 

3 – Slight 

potential 

4- Moderate 

potential 

5 – Highly 

likely 

Consequence 

1 - Immaterial (I) I-1 I-2 I-3 I-4 I-5 

2 - Low consequence (LC) LC-1 LC-2 LC-3 LC-4 LC-5 

3 - Moderate consequence (MC) MC-1 MC-2 MC-3 MC-4 MC-5 

4 – High consequence (HC) HC-1 HC-2 HC-3 HC-4 HC-5 

5 - Disaster (D) D-1 D-2 D-3 D-4 D-5 

The risks are calculated by the product of the likelihood times the consequence, and they range 

from a high of 20 to a low of 3. The highest priority risks identified by the WRAC process are 

listed in Table 50. 

Table 50 - Highest ranked risks potential unwanted events associated with captive cut-and-fill 

stoping. 

Potential unwanted event L C R 

Explosion occurs manually handling explosives 5 HC 20 

Person hit by roof fall when trying to support raise-up 5 HC 20 

Crushed by mobile equipment 4 HC 16 

Person falls into holes due to incorrect covers 4 HC 16 

Person falls into beanholes when installing timber sets 4 HC 16 

Person falls off timber while filling down manway or into fill 4 HC 16 

Fall of ground between supports 5 MC 15 

Equipment fire 3 D 15 

Damage to ground support while slabbing 5 MC 15 

Improper location under roof causes fall 3 D 15 

Rockfall in beanhole w / jackleg 5 MC 15 

Person with less than adequate familiarity accesses stope area 5 MC 15 

Equipment fire in the intake while person is in I drift / sill 3 D 15 

Person hit by rock fall while accessing unsupported ground to set up slusher 5 MC 15 

Persons not familiar with jacklegs operate that equipment 5 MC 15 

Equipment fire at face 3 D 15 

Mucker operator hit by protruding ground support 5 MC 15 

Person hit by material falling down skip shaft 5 MC 15 

Fire in the intake sends smoke into stope 3 D 15 

Decant water causes failure in another area as it runs out of stope 5 MC 15 

Hanging walls burst / slab out 3 D 15 

High stress occurs in pillars affecting stope ground / access 3 D 15 

Access sand filled stope and collapse occurs 3 D 15 

Inadequate crown pillar size leads to collapse when another level is accessed 3 D 15 

L = Likelihood 

C = Consequence 

R = Ranking 

Many of these events had similarities and the facilitator recognized that the list of events, 

requiring detailed analysis, needed to be reduced. Therefore, the group agreed to use maximum 

likely consequence and set the highest risk level at a multiple fatality potential (consequence = 

disaster, Table 49 and Table 50). A decision was then made to group the highest ranked 

101 
 

 

 

 

potential unwanted events into smaller, more generalized, events. Table 51 lists the four highest 

priority risks identified by the team that could result in a multiple-fatality event. 

Table 51 - Highest priority risks capable of producing a multiple-fatality event. 

Detailed analysis using the BTA 

1 Equipment fire in intake airway with persons in the stope at the face 

Detailed analysis using the work process flow chart 

2 Unfavorable location of the footwall lateral drift causes unstable ground condition in the access drifts 

3 Stope geometry is poorly defined by diamond drilling causing mining into sand fill drifts 

4 High stress conditions are poorly defined by geotechnical modeling causing rock bursts 

5.10.3.3 - Step 3, Determine Important Existing Prevention Controls and Recovery Measures 

One of the risks was analyzed with the BTA and three with a work process flow chart. The 

process took about 5 hours for a large, diverse group after 2 hrs of training in the principles of 

risk assessment and management. Through these approaches, the team identified an extensive 

list of existing prevention controls and recovery measures. Most of the controls listed represent 

the mines internal Best Practices. A common theme of discussions of these controls was the 

dependence on a few individuals to ensure compliance, with no formal auditing methods for 

some critical controls. 

Potential Unwanted Event 1 - Equipment fire in intake airway with persons in the stope at the 

face: The team identified the locomotive in the intake drift of the mine and haul trucks operating 

in the stope area and muckers operating in the stope area as the three primary sources of a fire 

with the potential for major consequences. The team identified 49 existing equipment fire 

prevention controls (Table 52). Thirty-one apply to all existing equipment, 12 are specific to 

locomotives, and 6 pertain to haul trucks and muckers. A total of 8 hours was spent examining 

the equipment fire hazards and controls. 

Table 52 - Priority existing prevention controls and recovery measures for equipment fires in the 

stope and stope access drift. 

General equipment fire 

PC1 Scheduled preventative maintenance on equipment is done every 250 hours, including hose 

inspection and change out (P) 

PC2 All work is done by mechanics (P) 

PC3 Hoses are four-braid, higher standard on locomotives, haul trucks and muckers (PB) 

PC4 Hose routing issues, such as damage that is found in inspection or maintenance, should 

lead to rerouting of hoses to correct the problem. Corrections should occur such as 

relocation, shielding, guarding, etc. (PB) 

PC5 The supply fuel lines are hard over the engine area, secured and located in a low location 

so any minor fuel leaks will not drip on hot surfaces (MH) 

PC6 Any return fuel lines are soft but four-braid hoses are used and located away from heat 

sources (MH) 

PC7 Heat wraps are located on hot surfaces of locomotives, haul trucks and muckers (PB) 

PC8 Wires are in looms to keep them in place and protect them from damage (PB) 

PC9 The electrics are maintained by trained personnel ( 2 levels) (PST) 

PC10 Locomotives, haul trucks and muckers should have circuit breakers (MH) 

PC11 New locomotives, all haul trucks and muckers should have wet brakes (MH) 

PC12 Mobile equipment operators are trained to the SOPs and other levels of operator are trained 

too (PST) 

102 
 

 

 

 

 

 

PC13 Daily operator inspections are made on locomotives, haul trucks and muckers to identify 

damage, leaks, flammable materials, etc. Operators are trained in the use of a Yellow Card 

for inspection. (P) 

PC14 Vehicles should have hydraulic pressure and temperature indicators that tell the operator 

about operating conditions and abnormalities (WD) 

PC15 Vehicles should shut down if they are overheated (MH) 

PC16 Preventative maintenance should include a power wash (P) 

PC17 Speed is controlled on all equipment by a hard barrier blocking the use of 4th gear (MH) 

RM1 Fire suppression systems are on all locomotives, haul trucks and muckers, activated by 

operator in the cab (MH) 

RM2 5-lb hand-held fire extinguishers are located in equipment cabs, with operators trained 

annually (P) 

RM3 A fire in the intake should require immediate evacuation of the mine (P) 

RM4 Fire emergency procedures should cover dispatch activating a computerized warning 

system (stench), using the radio and phone system to warn miners in the stopes about the 

fire (WD) 

RM5 All persons are trained in fire emergency procedures. Persons are trained to, on receipt of a 

fire warning, 1. Get out of the mine 2. If not possible go to refuge and stay in refuge until 

released, and 3. If cannot access refuge then barricade. (PST) 

RM6 All persons should have a CO chemical self-rescuer that can operate for an hour at 1% CO 

to help facilitate escape or access to the refuge (PB) 

RM7 There is a refuge chamber installed within 10 to 15 minutes travel from the stope, marked 

well (including air supply, communications, water, etc. for several people) (PB) 

RM8 Any required barricading in the stope is done with material and compressed air supply is 

available if not damaged (PB) 

RM9 Water supply in the stope is used to provide some protection in a fire (MH) 

RM10 There is a reliable (24/7) air compressor operating on the surface that can replace 

underground compressed air, activated by a manual control on the surface (MH) 

RM11 There is a brass-in and brass-out system to ensure that persons underground are accounted 

for (P) 

RM12 The mine has a looped leaky feeder system designed so that if it has a break due to a fire it 

still works (MH) 

RM13 There is a trained mines rescue team (MH) 

RM14 There is an ambulance and paramedics available in the surrounding area (MH) 

Locomotives 

PC18 The locomotive should shut down if it overheats (MH) 

PC19 Pressure failure should lead to total brake application on the locomotives (MH) 

PC20 Hydrostatic braking should provide an opportunity to use retard braking as an alternative to 

mechanical braking (MH) 

PC21 The locomotive, haul trucks and muckers have an air pressure gauge that tells the operator 

about operating conditions and abnormalities (WD) 

PC22 The locomotive is fuelled only on the surface unless there is a breakdown / fuel problem 

underground (MH) 

PC23 Engines are shielded from “blow in” materials / debris (PB) 

PC24 The fuel rail car is double walled (PB) 

RM15 There is fire suppression on the fuel rail car (MH) 

PC25 The cab should always separate the fuel rail car from the diesel engine (P) 

PC26 Special operational controls are in place when fuel is transported into the mine, including 

two specialized locomotive operators (P) 

PC27 There is a master switch on the locomotive to shut it off in an emergency but it is not easy 

to access (MH) 

RM16 Vehicle operators are trained to communicate a fire problem to the surface using a personal 

radio (PST) 

103 
 

 Haul trucks or muckers 

PC28 Supervisors should check two pieces of equipment per shift to ensure daily operator 

inspections have been done (P) 

PC29 Fuelling is done underground with quick disconnects for fuelling to decrease risk of 

vehicles driving away with hose in fuelling location (MH) 

PC30 Back pressure is indicated in the cab to tell the operator when the DPM is blocked by 

indicating pressure in the “red” sector of the gauge. The operator is trained to call 

maintenance in this situation (PST) 

PC31 A hot work8

 system is in place (P) 

PC32 There is a phone near where the two-yard mucker operates so that absence on the mucker is 

acceptable (WD) 

As above: see PC35 & RM43 

8

 Hot works = welding, cutting, grinding, etc. 

104 

PC – Prevention Controls 

RM – Recovery Measures 

EH – Eliminate Hazard 

MH – Minimize Hazard 

PB – Physical Barrier 

WD – Warning Devices 

P – Procedures 

PST – Personnel Skills and Training 

Potential Unwanted Events 2, 3 and 4 – Major ground failure due to inadequate mine design 

with crew working in the stope trapped or fatally injured: Three of the high-risk events 

(numbers 2, 3 and 4, Table 51) were determined to be primarily related to failures in the stope 

design process. At this mine, a stope proposal is produced for every proposed stope prior to 

mining. The stope proposal contains detailed mining and operational information. The team 

decided to evaluate the stope design process. The team also determined that it needed to be 

reorganized to contain more staff with mine planning experience. 

The existing stope planning process was mapped in detail, noting the points where decisions 

affecting the high-risk events occur and promoting an orderly discussion of the hazards. The 

primary output of the exercise was to recommend that a new step (Figure 37, step 3B) be 

inserted in the planning process to evaluate geo-mechanical issues in the Long Term Planning 

process (LTP). In addition, points of failure in the execution of the existing process steps were 

examined and, when the impact of failure was an increased risk of the subject event occurring, 

solutions and means of monitoring for compliance were developed as potential new controls. 
1 - FWL 

Activities 

• Probe hole drilling 

• Surface information 

• Geologic information 

Output 

Information on: 

• Reserve and 

geomechanical 

properties of existing 

pillars 

• Gases and water 

2 – Diamond Drilling 

Activities 

• Hole locations 

• Drilling 

• Information gathering 

• Interpretation 

Output 

Information on: 

• Assay 

• Ore body structures 

3a – Geologic Modeling
 

Activities
 

• Digital database 

• 3D developments 

• Geostatistical 

information 

• Dilution models 

3b – LTP 

Activities 

• Whole mine ground 

stress information 

105 

Output 

3D image of the ore body 

4 – Stope Proposal 

Development 

Information from all 

activities 

• Ore body geometry 

• Geomechanical 

• Ventilation 

• LTP 

Output 

• Stope proposal 

– Mining plan 

– Operations 

Map 

Figure 37 – A flow chart of the basic stope proposal and mine planning process. 

5.10.3.4 - Step 4, Identify New Prevention Controls and Recovery Measures 

Potential Unwanted Event 1 - Equipment fire in intake airway with persons in the stope at the 

face: After considering these existing controls the team identified additional steps to both 

prevent a fire from occurring and increase the likelihood that miners in the captive stopes will 

survive. These additional controls suggested by the team are identified in the following list 

(Table 53), again as either general or equipment-specific precautions. 

Table 53 - New prevention control and recovery measure ideas for the equipment fire in the 

intake drift event. 

Equipment fire in the intake entry 

NI1 Document the locomotive, haul truck and mucker hose specification (four-braid) and 

locations standards so they continue to be applied consistently (P) 

NI2 Check to ensure that that the improvements on hose routing on all mobile equipment and 

other modifications resulting from found damage are gathered to apply to other equipment 

when they are maintained (P) 

NI3 Add a final inspection by maintenance after preventative or other maintenance to ensure 

engine / brake area is clear of debris (P) 

NI4 Consider the use of a heat gun to check the operating temperature of the brakes (P) 

NI5 Document the locomotive, haul truck and mucker fuel hose specifications (hard and soft) 

and locations standards so they continue to be applied (P) 

NI6 Check to make sure the positive lead is protected with a fuse and master switch (P) 

NI7 Document the locomotive, haul truck and mucker electrical cable / wire specifications and 

locations standards so they continue to be applied (P) 

NI8 Ensure that work done on under 25V, and related training, does not compromise fire 

exposure (P) 

NI9 Add a final inspection by maintenance after preventative or other maintenance to ensure 

engine / brake area is clear of debris (P) 

NI10 Check Diesel Particulate Matter (DPM) filters to clearly identify design and maintenance 

requirements (P) 
NI11 A hot work system should be set up at the mine (P) 

NI12 Review the welding / cutting SOP at other mines and apply to this mine (audit current 

situation versus new SOP) (P) 

NI13 Define the required welding competency and train / “ticket” welders / cutters (PST) 

NI14 Make sure all persons have been appropriately fire trained (PST) 

NI15 Test whether the refuges can be found in a smoky situation and consider ideas such as 

lanyards and lasers to help miners find the refuge (note that muck bays may be 

inadvertently accessed too) (PST) 

NI16 Put CO shut off, PED shut off, or an E stop in the stope to shut down the section ventilation 

fan in a fire situation (WD) 

NI17 Investigate automation of surface compressor supply to underground should underground 

compressor fail or be compromised (MH) 

NI18 Investigate ways to effectively barricade in the stope (PST) 

NI19 Investigate ways to supply more air into the stope (MH) 

NI20 Investigate a second top egress to improve survivability if fire traps people in the stope 

(MH) 

NI21 Add the use of stope water supply for fire events as a part of training for dealing with a fire 

if trapped in the stope to Emergency Training (PST) 

Locomo

tives 

NI22 Make sure inspection checks are done on locomotives as well as rubber tired equipment (P) 

NI23 Reinforce the need to review the risks related to underground fuel bays located in intakes 

entries (PST) 

NI24 Check to ensure that there is automatic fire suppression on all locomotives (P) 

Haul trucks or 

muckers 

NI25 Investigate the application of Wiggins fuelling hardware in underground fuelling locations 

(MH) 

NI26 Reinforce the need to shut down muckers when the operator is not on the machine (P) 

NI27 Investigate the ability to isolate a vehicle fire in the lateral footwall area (MH) 

NI28 Vehicle operators in the lateral footwall / stope access area should be made familiar with 

the refuge location and related actions required during a fire (where to go to barricade) 

(PST) 

NI – New Ideas 

EH – Eliminate Hazard 

MH – Minimize Hazard 

PB – Physical Barrier 

WD – Warning Devices 

P – Procedures 

PST – Personnel Skills and Training 

It is worth noting that most of the 25 new control measures are either directed to improve 

response to a fire to mitigate consequences or they increase the likelihood that existing good 

practices are followed uniformly through more rigorous audit systems and documenting of 

practices. Five of the new controls concern improving the ability of miners to secure refuge 

from smoke and maintain a reliable supply of emergency air. While the mine has refuge 

chambers and well-developed emergency plans, this exercise was the first detailed examination 

by the miners as to how they would secure a refuge from smoke should they find themselves 

trapped within the stope. Part of this detailed examination was a hard look at the vulnerability of 

the existing measures to damage from the event and formulation of a “plan B.” The value of the 

process was achieved by having the miners mentally work through what steps they could take to 

react to problems. Innovative solutions were suggested and the gaps in protections needing 

further effort by mine staff were identified. 

Also of note is the relative rank of the controls with regard to the typical hierarchy. Existing 

controls are a mix of engineering, 41%, administrative, 57% and monitoring, 2%, with none 

106 
 

 

 

 

 

 

 

 

directed at eliminating the hazard of combustible fuel and oils due to the mining method’s 

dependence on diesel equipment. In the new controls the mix is engineering, 24%, 

administrative, 52%, and monitoring, 24%. One new response control is directed at eliminating 

the primary hazard of a single egress from the stope by suggesting a second egress out the top of 

the stope to an independent airway. 

Potential Unwanted Events 2, 3 and 4 – Major ground failure due to inadequate mine design 

with crew working in the stope trapped or fatally injured: The left-half of the BTA was 

performed, concentrating on modifications to the mine planning and design process to prevent an 

occurrence of a major ground failure. The consequences side of these high-hazard events was 

not examined due to time constraints and the low likelihood that response actions would alter the 

outcome of these rapidly developing catastrophic events. Twenty-four new prevention controls 

were identified (Table 54) that spanned the four distinct planning phases identified in Figure 37. 

Table 54 - New prevention control ideas for stope design and mine planning. 

1 – Improving 

Mine Planning 

Footwall 

Lateral 

Locations 

NI29 Make Long Range Planning (LRP) more systems oriented, i.e. ventilation, utilities, mine 

method, service life, egress, etc. (MH) 

NI30 Purchase additional survey equipment (P) 

NI31 Audit that survey is being done (P) 

NI32 Communicate that job isn't done until surveyed (P) 

2 – Definition 

by Diamond 

Drilling (DD) 

NI33 Draft formal policy with exception requirements (P) 

NI34 Support concept that more development and probing provides more information and 

flexibility to this stage and increases chance of success (P) 

NI35 Receive timely Vulcan input in order for geologists to see changes in 3D model (P) 

NI36 Cross-train and temp hire for high logging demand periods (PST) 

NI37 Log info at hole when drilling bad ground (P) 

NI38 Increase amount of information collected from directional drill core near ore zone (P) 

NI39 Audit that layout design is followed (P) 

3a – Geo 

Modeling 

NI40 Improve retention of technical expertise including mine site experience (P) 

NI41 Investigate use of survey-based volume reconciliation (P) 

NI42 Continue focus on reconciliation process between face and mill (P) 

3b – Stress 

Control 

Planning (new 

in the model) 

NI43 Ground stress considerations need to be incorporated into long range and life of mine 

planning as well as stope proposal (P) 

NI44 Investigate and apply methods that gather useful ground stress information during mining 

for mapping (P) 

NI45 Gather stress info from instrumentation and map to aid planning (P) 

NI46 Look at other similar mining operations re: overall ground stress potentials (P) 

4 – Stope 

Proposal 

Development 

NI47 Consider stope proposal and face mine planning system at other operations to help 

develop their approach (P) 

NI48 Mentor new miners after stope school by placing with experienced miners in stope to learn 

plan (PST) 

NI49 Develop a standard that requires mining to minimum width to ore before widening for 

raise access (P) 

NI50 Establish expert captive stope prep and development crew (PST) 

NI51 Use 3D design images to introduce production people to the new mine method and area 

(PST) 

NI52 Use input from production to walk through 3D info and develop final plan with detail by 

step of mining process (P) 

NI53 Reinforce importance of scheduling services and equipment (P) 

107 
The 24 newly identified controls are made up of administrative, 64%, engineering ,24%, and 

monitoring, 12%. The newly added step in the planning process emphasizes engineering 

controls. The end product of the proposed changes would be to put in place a mechanism to 

remove the potential for exposure to the high-risk hazards. 

5.10.3.5 - Step 5, Discuss Implementation, Monitoring and Auditing Issues 

The overall acceptance and understanding of the risk assessment process by the teams at this 

mine was very good. The teams selected were energetic and knowledgeable in the subjects. 

Communication between team members during the process was thorough and members actively 

challenged each other’s paradigms. All of these factors had a positive effect on the outcome of 

the process which developed a large number of suggestions for improvement embraced by 

management. 

One issue encountered was the amount of time necessary to educate team members on the 

process. In this group, none had any exposure to formal risk management practices. As a result 

a half-day was required to train the team members. As risk management is applied to more areas 

of the mine operations, a significant training burden will occur. 

A second issue encountered was the tendency of the team to try to solve every issue that arose 

rather than identify issues and move on. A skilled facilitator was required to keep the team on 

task. The facilitator was also challenged with recognizing team members who had difficulty 

expressing their thoughts and assisting them in better describing their ideas for consideration by 

the team. Without a skilled facilitator the productivity of the exercises would have been 

severely limited. 

Perhaps the greatest issue was the tendency of the team to seek out procedures (P) and personnel 

skills and training (PST) or low level engineering controls rather than beginning with controls 

that could eliminate the hazard (Figure 38). In this respect the outcomes of these exercises may 

not be true Best Practices but the product of a cultural acceptance of relatively high levels of risk. 

The facilitator expressed that he intruded further into the process than he normally would in 

attempts to move the group up the hierarchy of control. A commonly repeated phrase “that’s just 

part of mining” was not challenged by the question “why does it have to be?” from the group. In 

this aspect of risk management it may take some time before the industry learns the relative 

importance of the hierarchy of control. 

108 
0 

5 

10 

15 

20 

25 

30 

35 

40 

Number 

EH MH PB WD P PST 

Prevention Controls Recovery measures New Ideas 

Figure 38 - Distribution of prevention controls and recovery measures for the captive cut-andfill change of mining method risk assessment. 

109 
6.0 – Lessons Leaned 

In general, the ten case studies showed that the MHRA process provided information considered 

beneficial for a safer work environment. The MHRA process can be used to enhance the safety 

requirements that exist in current regulations or standard operating procedures. This report is not 

intended to be nor should it be misconstrued as advocating more stringent regulations. It does 

demonstrate that portions of the mining industry are capable of utilizing the MHRA process and 

could benefit from its application. 

The ten case study examples provide insight as to how the MHRA approach might be used to 

mitigate the risk from major hazards in US underground mines. Significant threats were 

identified as well as an inventory of existing controls and recovery measures specific to each 

threat. Generally new ideas were presented in the form of an action plan (Appendix B) or a risk 

register (Appendix C) for management consideration. All this was accomplished in a structured, 

group-oriented activity designed to produce a written report. 

6.1 - The Scoping Document 

The risk design or scoping document needs to identify an issue of great importance to the mine. 

These issues were often referred to by the mining personnel as “issues that keep me up at night.” 

As this comment indicates, the risk assessment team should be aware that a frank and open 

discussion of the hazards is necessary. In the 10 case studies, significant issues were identified 

and analyzed. However, in one case study (Mine A) the risk assessment team did not feel 

empowered to address the hazard identified in the scoping document. At case study Mine C, the 

risk assessment team did not see a compelling need to address the spontaneous combustion threat 

more than had already occurred at the mine. It is possible that both these issues could have been 

addressed if the management of the mining operations had clearly identified the hazards under 

consideration as major threats and communicated its desire to the risk assessment team to find 

ways to lower the risks associated with these hazards. 

6.2 - The Risk Assessment Team 

The mines selected their own personnel to participate in their respective MHRA. The makeup 

and size of each mine’s MHRA team was based upon the type and size of the risk assessment 

topic as shown in Table 12. Some teams were quite large as in the case of Mines J and D and 

some teams were relatively small as in the case of Mine B. The risk assessment team needed the 

following important characteristics to function effectively: knowledge, diversity, a skilled 

facilitator, outside experts, training and time. 

Knowledge - The case studies demonstrated the need for the risk assessment team to contain key 

mining operation personnel knowledgeable of the hazard under consideration and familiar with 

all aspects of the operation. This knowledge should go beyond current regulations and mine 

practices and should focus on comprehending the root cause of hazards. Innovative solutions 

depend on this level of knowledge. 

110 
Diversity - The diversity of the risk assessment team increased its breath of knowledge and 

operational perspective. In some cases, the miner familiar with the work process under 

discussion had a unique perspective that was not always apparent to the professional or 

management team members. Case study Mines G, H, I and J were observed to have excellent 

diversity which may have helped the team identify such extensive lists of controls. 

A Skilled Facilitator - The facilitator must be well-trained and skilled in the MHRA process. 

The facilitator is required to always know where the risk assessment team is heading and keeping 

it on task, and must also deal with dominant personalities and make sure that all voices are heard. 

It is important for the risk assessment team to have knowledge of the hierarchy of controls 

concept. It is the facilitator’s responsibility to make sure the team has this knowledge. 

Outside Experts - The risk assessment team should contain outside experts that have expertise 

beyond that contained at the mine site concerning the hazard under consideration. Typically 

outside experts are external to the normal decision-making group at the mining operation. They 

can consist of technical representatives from manufacturers, consultants familiar with the mining 

operation, or content experts from academia and government. 

Training - The risk assessment team must have a working knowledge of risk assessment tools 

and techniques. This can be accomplished prior to or during the actual risk assessment. 

However, time used for training should not limit the time needed to conduct the MHRA. 

Time - The risk assessment team must have sufficient time to adequately address its tasks. Case 

study Mines A and C did not have sufficient time to adequately perform the MHRA exercise. 

Part of this was due to the need to provide the risk assessment team members with some 

fundamental training in the basic concepts of risk management. 

6.3 – Important Risk Assessment Tools and Techniques 

Risk assessment tools and techniques were used during several steps in the MHRA exercise. 

During Step 1, when the major potential hazards were being identified and characterized, flow 

charts were often used. These flow charts were especially useful in dissecting work processes. 

In other cases, when examining operational issues covering the mine site, it was necessary to 

segment the mine in a logical manner. 

During Step 2 of the MHRA exercise, when risks were ranked, the WRAC and PHA were used. 

If the consequences of a potential unwanted event are high, it may not be necessary to risk rank 

the potential unwanted events using a WRAC or PHA. Regardless of the method used, it was 

critical for the risk assessment team to develop a complete list of potential unwanted events 

associated with the major hazard under consideration and determine which deserved the effort of 

an MHRA. 

After the risk ranking process, the team focused on determining important existing prevention 

controls and recovery measures (Step 3) and identifying new prevention controls and recovery 

measures (Step 4). In all case studies with the exception of Mine B, a BTA was used. A BTA 

111 
was required for each potential threat. The BTA was the most used risk assessment technique 

during this pilot project. 

6.4 - The Risk Assessment Team Outputs (Identified Controls) 

The main output of the risk assessment team is the existing and new prevention controls and 

recovery measures that lower the risk associated with the hazards under consideration. In total, 

451 controls were listed during the ten case studies. The minimum was 1 (Mine B) and 

maximum was 103 (Mine I). There is no correlation between the number of controls and the 

success of the MHRA. At Mine B, one new idea was identified and it eliminated the hazard. No 

other controls were needed. In general, procedure (P) controls (44% of total) were used the most 

by the 10 risk assessment teams and hazard elimination (EH) the least (less than 1% of the total 

controls) (Figure 39). The other control categories ranged from 19% for minimize hazards (MH) 

to 9% for warning devices (WD). 

0% 

10% 

20% 

30% 

40% 

50% 

Percentage 

EH MH PB WD P PST 

Figure 39 - Percentage of the total controls by category. 

The MHRA process requires that hazard elimination be considered as a primary means to reduce 

risks. In practice, it is often difficult for the risk assessment teams to discuss whether to accept 

or eliminate the hazard under consideration. This may be partly caused by the team’s lack of 

participants responsible for making these kinds of decisions or partly due to the perceived 

MHRA objectives. Once a mine is operational, hazard elimination becomes more difficult and is 

best considered when management specifically requests it and this request is included in the 

scoping document. A total of three new ideas from three different case studies were classified as 

hazards elimination. Therefore, seven of the case studies did not consider hazards elimination as 

a potential control. 

MHRA controls rely extensively on the use of regulated standards and company Best Practices. 

In some cases it was difficult to determine if the risk assessment teams were aware of the 

differences between existing practices and Best Practice. Outside experts were helpful in 

identifying controls, barriers or work processes that represented leading industry practices. 

6.5 – Documentation 

A written document is critical to the MHRA process and, at a minimum, should contain 1) a list 

of existing prevention controls and recovery measures that can be monitored and audited, and 2) 

112 
a lists of new ideas for further consideration by management. Management must assign persons 

to be accountable for existing and newly adopted controls and respond to the team with the 

reasons for their actions, especially if the assigned persons decide not to act on any 

recommendation. It is not known if the existing controls were being monitored or audited at the 

case study mines or if the new ideas were evaluated by management. There was one occasion 

when management, after reviewing the list of new ideas, asked the risk assessment team to rank 

their new ideas. The team did not feel that it had enough data or enough time to adequately 

accomplish this task. There is also a possibility that a consensus would have been difficult to 

achieve. 

113 
 

 

 

7.0 – Success of Risk Assessment Case Studies 

A number of key points were recognized from the ten case studies. These key points help to 

define the degree of success each case study realized in performing an MHRA and provided an 

opportunity to understand its strength and weaknesses. To help evaluate the degree of success, 

the MHRA case study exercises were divided into six categories. Each category represents an 

important aspect of the MHRA exercises. The NIOSH observers compiled information on each 

case study and made a determination as to how each performed. The six categories are: existing 

risk management culture, risk assessment design, risk assessment team, risk assessment process, 

quantity of existing controls, and quality of new ideas. For each of the ten case studies, the 

demonstrated degree of success was defined in a relative sense as more-than-adequate, adequate, 

or less-than-adequate (Table 55). This evaluation was based on an analysis of the risk 

assessments team performance and the quality and character of the identified and proposed 

controls. Three of the ten case studies are rated as performing a more-than-adequate risk 

assessment, five as adequate, and two as less-than-adequate. A method for self-assessment of 

mining operations risk management culture is provided in Appendix D. 

Table 55 - An assessment of the adequacy / success of the ten MHRA case studies. 

Case 

study 

mine 

Existing risk 

management 

culture 

Risk 

assessment 

design 

Risk 

assessment 

team 

Risk 

assessment 

process 

Extent of 

existing 

controls 

Quality 

of new 

ideas 

Overall 

Mine A L L A NA NA NA L 

Mine B L A M NA NA M A 

Mine C L A A L L L L 

Mine D A A A A A A A 

Mine E L A A A M A A 

Mine F L A M A A A A 

Mine G A A A A M A A 

Mine H A A M M M M M 

Mine I A A M M M M M 

Mine J M A M M M M M 

A – Adequate 

M – More-than-adequate 

L – Less-than-adequate 

NA – Not available or did not occur 

7.1 – Existing Risk Management Culture 

The existing risk management culture of a mining operation impacts the potential for a 

successful MHRA. One way to measure the suitability of an operational culture for MHRA is to 

identify the degree to which risk assessment techniques have been previously embraced by the 

mine. Risk assessment techniques are discussed in Section 3.1 and can be summarized in the 

order of increasing complexity as 1) informal, 2) basic-formal, and 3) high-level formal. 

Informal risk assessment techniques, i.e. multiple step approaches where workers are 

asked to look for hazards, determine the significance of the hazard, and take some action 

to mitigate the risk. Examples include SLAM, Take-Two for Safety, etc. At the case 

study mines, informal risk assessment techniques were already in use at some mines and 

not evident at others. 

114 
Basic-formal risk assessment techniques, such as Standard Operating Procedures (SOP) 

and Job Safety Analysis (JSA), establish official procedures and practices for important 

work practices at the mining operation. 

High-level formal risk assessment techniques are structured approaches that incorporate 

risk analysis tools, such as the HAZOP, FTA, etc., and produce a document that assesses 

risks. Several mines indicated that these techniques may have been used by the company 

in the past. Most of the case study mines were not using high-level formal risk 

assessment techniques. 

It is assumed that mines already using informal and basic-formal risk assessment techniques 

appeared to be in a better position to successfully undertake an MHRA. Undertaking an MHRA 

could represent a significant change in the way the organization functions. Therefore, it may be 

more appropriate for mining operations to first begin to implement informal or basic-formal risk 

assessments before attempting an MHRA. Most case study operations had indicated some use of 

basic-formal risk assessments techniques in the past, but the quality of these applications was 

difficult to determine. One clue to recognizing an operation’s reliance on these tools was to 

determine if there was an SOP that defined how other SOPs would be developed, recorded and 

managed. One case study operation had such an SOP. Of the ten case study mines, five were 

observed to have either an adequate or more-than-adequate risk assessment operation culture. 

The other five were assessed as less-than-adequate in that no risk assessment techniques were 

evident. 

7.2 – Risk Assessment Design 

The risk assessment design was best executed when the mining operation representatives took 

MHRA training and prior to the actual MHRA exercise. If training was not possible, extra effort 

was placed on making sure that as many persons as possible had an opportunity to comment on 

the risk assessment design document prior to the actual MHRA. The key here is feedback. 

Remember, the hazard the risk assessment design addresses should be of great importance to the 

mining organization. The phase “this is the issue that keeps us up at night” was often used by 

participants to describe the hazard under consideration by the MHRA. 

 

In all but one of the case studies, the risk assessment design was considered adequate. The case 

study classified as having a less-than-adequate risk assessment design was based on the need to 

change the design once the MHRA began. 

7.3 – Risk Assessment Team 

Team selection is a critical component of a successful MHRA. Members of a risk assessment 

team should be picked carefully, making sure that they are 1) knowledgeable about the hazards 

under consideration, 2) not overly committed to a particular way of business or work process, 

and (3) able to express their opinions within a group setting and in the presence of supervisors. 

All of case study risk assessments were staffed with members that fit these characteristics. 

However, because most teams struggled with hazards elimination as a potential control, these 

115 
teams might have benefited from additional persons with the authority and responsibility to 

address the significant issues associated with hazard elimination. 

Diversity is an important aspect of a successful risk assessment team. Solutions to major hazards 

can come from persons at all levels within a mining operation. This is why labor should be 

represented as equal participants within the risk assessment team. Both management and labor 

representatives should be 1) knowledgeable about the hazard under consideration, and 2) familiar 

with the associated work processes. Team members from labor were usually active in group 

discussions and very aware of work process details that only come from actually performing the 

tasks. In several of the case studies, members of the general workforce were key components of 

the risk assessment team. They also can help to communicate the findings of the MHRA to the 

general workforce. This was observed to be a powerful tool for implementing the outcomes of 

the MHRA. 

Another desired aspect of a risk assessment team is the use of outside experts, i.e. outside the 

mining operation. These experts should have special knowledge about the major hazard under 

consideration that is not currently available on the company’s team. This expertise can come 

from government, academia, manufacturing or consulting agents. These outside experts will 

help to eliminate attitudes like, “this is the way we have always done it.” Five of the risk 

assessment teams were viewed as more-than-adequate because they used outside experts on their 

team. 

Lastly, training is essential for the risk assessment team members. This can be accomplished 

prior to the MHRA or it can occur during the MHRA. In fact, every MHRA exercise 

incorporated training. This must be factored into time needed to complete the MHRA. 

7.4 - The Risk Assessment Process 

When designing an MHRA, it is important to recognize that the team has flexibility in deviating 

from the general structure. Very few of the case studies followed every step in the MHRA 

process (see Section 4.0 for more details). In several cases, the consequence of the event was 

viewed as significant and no further discussions of event likelihood were warranted (Mines F, H 

and I). In one case, a thoughtful discussion of an existing work process revealed that a relatively 

simple change to the process effectively eliminated the hazard (Mine B). This MHRA reached 

its objective during the first step in its process. In another case, the risk assessment process 

could not be adequately addressed because the risk assessment design had been altered and there 

was insufficient time to complete the MHRA (Mine A). In a third case, the one classified as 

less-than-adequate (Table 55), the risk assessment process was abandoned by the risk assessment 

team (Mine C). Of course, flexibility within the procedure has the potential to produce a wide 

range of responses. Deviation from a formal risk assessment plan should be under the guidance 

of a skilled facilitator without a stake in the outcome of the process. 

7.5 – The Extent of Existing Controls 

An MHRA is undertaken when a mining operation seeks to move beyond simply reacting to 

standards and regulations and desires to develop a more proactive approach to dealing with its 

116 
major hazards. The extent of the controls for a particular hazard can be viewed as a measure of 

the successful application of an MHRA. If the list of controls mirrors that which is required by 

standards or regulations, then the outcome of the MHRA should be considered less-thanadequate. The list of controls is defined in two ways: those prevention controls and recovery 

measures currently in place within the mining operation, and the new ideas that help to further 

mitigate the risks associated with the hazards. The existing controls are the subject of this 

section, while the new controls are covered in Section 7.6. 

The extent of existing prevention controls and recovery measures for the ten case study mines 

varied widely. Two case studies did not sufficiently analyze to determine their adequacy. One 

case study was viewed as less-than-adequate from a risk management perspective since the 

existing controls were completely defined by those required by MSHA regulations. The other 

seven case studies had either adequate or more-than-adequate existing prevention controls and 

recovery measures. The more-than-adequate classification was defined by the depth and breath 

of the controls listed by the risk assessment team. 

7.6 – The Quality of New Ideas 

One of the most important outputs from an MHRA is the new ideas generated by the team to 

further mitigate the risk associated with the major hazard under consideration. A risk assessment 

team should always be expected to produce additional prevention controls and recovery 

measures beyond the existing mandated standards. That is the main purpose for conducting the 

MHRA. Failure to produce such results indicates problems with the team composition or the 

scope of the task. When a team does not search for new ideas, it will fail to suggest actions that 

will lower risks. Two case studies were unable to produce new ideas – one because it was 

unable to complete the risk assessment process; the other because it did not feel a need. The 

other eight case studies produced new ideas that seemed to have merit and deserved to be 

investigated further by the mining operation. 

Distinguishing between an adequate versus more-than-adequate quality of new ideas was 

accomplished by an assessment of their quantity and character. One way to assess the character 

of new ideas is to determine their place in the hierarchy of the control (Section 4.4). The most 

effective controls eliminate or minimize the hazards. Mine B produced one new idea during the 

initial discussion period that effectively eliminated the hazard. This is without question the most 

effective form of control. Next, physical barriers are used to separate the worker from the 

hazard. Less effective controls rely on warning devices requiring manual response and 

administrative procedures. The least effective controls rely on personnel skills and training that 

contain many opportunities for human error. The most successful controls emphasize hazard 

elimination, as was the case for Mine B. An effective MHRA contains a balanced collection of 

controls. The case studies listed as more-than-adequate (Mines H, I and J) had this balance, 

while those viewed as adequate relied more on the less effective hierarchy controls. 

117 
8.0 – Future Use of the MHRA Process in Mining 

In this report, an MHRA methodology was investigated through a NIOSH pilot project that 

conducted field trials at ten case study mines. The tools and techniques used in the Australian 

Minerals Industry to conduct an MHRA were reviewed and summarized. Detailed information 

from the ten case study mines was reported and analyzed. The lessons learned from the case 

study were examined and the relative success of the MHRA process for mitigating risks was 

determined. 

While this concept is relatively new to the US mining community, it is not new to other US 

industries with major hazards, i.e., nuclear, petrochemical, aerospace, etc. – nor is it new to many 

other major mining countries where legislation mandates that sound risk management principles 

be utilized. Certainly considerable national and international expertise exists today to help those 

that are interested in becoming more proactive in dealing with their major hazards. These efforts 

could be strengthened with an accepted framework for conducting an MHRA and facilitated with 

appropriate training and instructional guidelines and resources. 

All mines have the potential for major hazards that can fatally injure miners and threaten the 

well-being of the mining operations. It therefore seems prudent for all mines to consider MHRA 

as a means to proactively address safety threats to their mining operations. This is seen as a 

means of going beyond merely complying with existing mining regulations, by systematically 

examining hazards capable of producing significant consequences. MHRA is also needed where 

a significant change is planned to equipment, machinery, procedures, or manner of working. 

Mine management needs to lead the planning, organizing, controlling and motivating efforts in 

support of the MHRA approach. Management must understand that an MHRA can produce a 

design recommendation but should not attempt to produce the actual engineering design. In 

most cases, the teams did not have the right make-up for engineering design work. Suppliers of 

goods and services and regulatory agencies are also an important partner and can assist in the 

risk assessment team. Labor should be given the opportunity to participate in the process and 

take an active role in implementing change. One means of evaluating if an organization and its 

management are ready for the MHRA process is through a self-assessment of its current 

management practices. Appendix D provides a means for an organization to identify how it 

addresses risk and hazards in a qualitative format. MHRA is best applied in organizations that 

have moved beyond reactive management of hazards and have mastered basic-formal risk 

assessment processes. 

An MHRA can be very effective if used early in a project’s life cycle, when systems and work 

processes are being designed, and should be considered in conjunction with other risk assessment 

activities, i.e. financial, environmental, etc. Treating a hazard early in the life cycle, when 

systems are being designed and equipment specified, can be done more efficiently and 

effectively than later in the cycle, when most work processes revolve around maintaining 

existing designs. 

It is critical that the risk assessment be designed to exploit the strengths of the MHRA approach 

and to avoid its weaknesses. The strengths of the MHRA approach are its ability to 

118 
1.	 set clear direction to solve specific high-risk problems, 

2.	 focus on priority concerns, 

3.	 get involvement and commitment from a wide cross-section of the mine’s work force, 

4.	 decrease potential losses for a mining operations, 

5.	 help to build teams to solve major mining issues, 

6.	 go beyond merely complying with existing mining standards and regulations, and 

7.	 focus upper management attention on issues existing at the operational level (this is 

where the written documentation can be very helpful). 

The weaknesses or threats of the MHRA approach are its need to 

1.	 focus on changes within the existing way the mine conducts business, 

2.	 take time away from activities directly related to production, 

3.	 put additional time constraints on a mining operation’s “best people,” 

4.	 introduce the cost of implementing new prevention controls and recovery measures, 

5.	 potentially alter a mining operation’s priorities, 

6. need for there to be an existing risk management structure to build upon, and 

7. need for an openness in management / labor communications. 

In general, the ten case studies demonstrate that most US mines have the capability to 

successfully implement an MHRA and that the MHRA methodology produced additional 

prevention controls and recovery measures to lessen the risk associated with a select population 

of major mining hazards. The basic ingredient for a successful MHRA is the desire to become 

more proactive in dealing with the risks associated with events that can cause multiple fatalities. 

If a mining operation does not commit sufficient time or is not willing to utilize its most 

experienced personnel to this effort, it is unlikely to produce a successful outcome. A successful 

outcome is marked by a thorough examination of existing prevention controls and recovery 

measures and the generation of new ideas to further mitigate the risks associated with the major 

hazards under consideration. It is also essential for a mining operation to be receptive to a 

written report that discusses key existing controls and identifies who will investigate the risk 

assessment team’s list of new ideas. 

All mines arguably have major hazards with the potential to produce multiple fatality events. 

The ten case studies demonstrate that most mines currently go beyond the minimum 

requirements for mitigating the risks associated with major hazards. When pressed to consider 

more controls to further mitigate the risk, a well-staffed risk assessment team was able to identify 

additional controls. For these mining operations, it was important to add additional controls, 

even if they were not required by existing mining regulations, to lower the risks associated with 

the major hazards under consideration. These operations realize that the negative consequences 

associated with these potential unwanted events require additional actions and that current 

regulations do not totally protect their miners from all the specialized site-specific hazards 

shaped by local characteristics. The MHRA methodology represents a structured approach that 

helps mining operations develop additional controls aimed at mitigating the risk associated with 

their most significant hazards. 

While all mines have major hazards, not all mines are prepared to utilize an MHRA. If a mining 

operation is not willing to commit its best people to an MHRA or will not provide them with 

119 
 

sufficient time to see the process through to its conclusion, the MHRA output may prove to be 

useless. Additionally, if a mining operation is not prepared to discuss its major hazards in an 

open and honest fashion and to present the findings of the risk assessment in a written report, the 

MHRA output will be unclear, and attempts to monitor or audit important controls may not be 

possible. 

An MHRA can be most effective when the mining operation possesses 1) a proper understanding 

of its hazards, 2) experience with informal and basic-formal risk assessment techniques, 3) 

proper facilities, machinery and equipment, 4) suitable systems and procedures that represent 

industry Best Practice, 5) appropriate organizational support with adequate staff, 

communications and training, 6) a formal and thorough plan for emergency response, and 7) a 

safety risk management approach that is promoted and supported at all levels of the organization. 

120 
9.0 – References 

Anon, 2005, “An Unplanned Detonation of a Blast Hole Occurred at a Surface Coal Mine in 

Indiana,” Mine Safety and Health Administration, Safety Hazard Alerts webpage, June 10, 2005. 

CFR, 2005, “Escapeways,” Code of Federal Regulations, Part 30, Section 57.11050. 

CMEWA, 2003, “Review of the Mine Safety Inspection Act of 1994,” Chamber of Miners and 

Energy, Western Australia. 

Freeman, M. “Observations on Mine Safety Management from Review of Major OHS 

Prosecutions and Investigations”, NSW Department of Primary Industries, Sydney, 2007 

Gates, R.A., R.L. Phillips, J.E. Urosek, C.R. Stephan, R.T. Stoltz, D.J Swentosky, G.W. Harris, 

J.R. O’Donnell, Jr., and R.A. Dresch, 2007, “Fatal Underground Coal Mine Explosion, January 

2, 2006, Sago Mine, Wolf Run Mining Company, Tallmansville, Upshur County, West 

Virginia,” Report of Investigation, Mine Safety and Health Administration, May 9, 2007, 189 p. 

Grayson, L., A. Bumbico, S. Cohn, A. Donahue, J. Harvey, J. Kohler, T. Novak, C. Roberts, and 

H. Webb, 2006, “Improving Mine Safety Technology and Training: Establishing U.S. Global 

Leadership,” Mine Safety Technology and Training Commission, National Mining Association, 

193 p. 

Holmberg, R. and D. Salomonsson, 2002, “Snap, Slap and Shoot – A Possible Cause for 

Premature Ignition of Shock Tube,” International Society of Explosive Engineers, 2002 General 

Proceedings Collection - Volume II, pp. 91-103. 

Hopkins, A., 2000, A Culture of Denial: Sociological Similarities between the Moura and 

Gretley Mine Disasters,” Journal of Occupational Health and Safety Australia and New Zealand, 

Vol. 16, No. 1, 2000, pp. 29.36. 

Iannacchione, A.T., G.S. Esterhuizen, S. Schilling, and T. Goodwin 2006, Field Verification of 

the Roof Fall Risk Index: A Method to Assess Strata Conditions, Proceedings of the 25th 

International Conference on Ground Control in Mining, Morgantown, WV, Aug., pp.128-137. 

Iannacchione, A.T., G.S. Esterhuizen, L.J. Prosser, and T.S. Bajpayee, 2007, Technique to 

Assess Hazards in Underground Stone Mines: The Roof Fall Risk Index (RFRI), Mining 

Engineering, Vol. 59, No. 1, pp. 49-57. 

Jobs, B., 1987, Inrushes at British Collieries: 1851 to 1970, Colliery Guardian, Vol. 235, No. 5 

and 6, May and June, pp. 192-9 and 232-5. 

Joy, J., 2006, Minerals Industry Risk Management Framework, Minerals Industry Safety and 

Health Centre, University of Queensland, 83 p. 

121 
McAteer, D., 2007, Testimony Before the Committee on Education and Labor, United States 

House of Representatives, April 21, 2007. 

Moebs N.N. and G.P. Sames, 1989, Leakage Across a Bituminous Coal Mine Barrier, USBM RI 

9280, 17 p. 

NSWDPI, 1997, Risk Management Handbook for the Mining Industry: How to conduct a risk 

assessment of mine operations and equipment and how to manage risk, New South Wales 

Department of Primary Industries, MDG 1010, May 1997, 95 p. 

QDME, 1998, Recognised Standard for Mine Safety Management Systems, Queensland 

Department of Mines and Energy, Safety and Health Division, Coal Operations Branch, January, 

1999, 6 p. 

QMC, 1999, Information Paper – Safety and Health Management for Queensland Mines and 

Quarries, Queensland Department of Mines and Energy and the Queensland Mining Council, 

Brisbane, Australia, 25 p. 

Robertson, A. MacG. and S. Shaw, 2003, Risk Management for Major Geotechnical Structures 

on Mines, in Proceedings of Computer Application in the Mineral Industry, CAMI, Calgary, 

Alberta, CA, Sept. 8-10, 2003, 18 p. 

Smith, A.C, W.P. Diamond, T.P. Mucho and J.A. Organiscak, 1994, Bleederless Ventilation 

Systems as a Spontaneous Combustion Control Measure in U.S. Coal Mines, US Bureau of 

Mines IC 9377, pp. 1-43. 

Standards Australia, 2004, Risk Management, AS/NZS 4360:2004, Sydney, Australia, 26 p. 

Watzman, B, 2007, On Protecting the Health and Safety of America’s Mine Workers Testimony 

of Bruce Watzman, Vice President of Safety and Health, National Mining Association, Before 

the Committee on Education and Labor, United States House of Representatives, March 28, 

2007, 6 p. 

122 
 

 

 

 

APPENDIX A – Example of a Bow Tie Analysis (BTA). 

In the paper, parts of a BTA were often provided to demonstrate the application of this risk 

analysis technique. Table 56 and Table 57 are exhibits of a fully completed BTA. 

Table 56 - Left side BTA for Mine I. 

Causes Prevention Control Measures 

Top Event = Fire on Locomotive or mantrip 

1 - Short circuit PC1 Maintenance, weekly checks of loco (general inspection) [P] 

PC2 Pre-operation check by operator (brakes, trams, etc.) [P] 

PC3 Operator is experienced enough to recognize abnormal operation [PST] 

PC4 Locomotives have fuses and breakers [MH] 

PC5 Some cables are protected in conduits [PB] 

PC6 Operators training [PST] 

PC7 Radio communication is available to get assistance/advice, re abnormal operations [PST] 

PC8 Abnormal operation is reported to supervisor and maintenance shop [P] 

PC9 Locomotive designed to standard [MH] 

PC10 State electrical inspector inspects any loco that has had major rebuild [P] 

PC11 Mine personnel inspect new equipment and rebuild before it is used [P] 

2 – Overheated 

battery (water, 

load, charge) 

PC12 Maintenance batter is cleaned, watered, checked for dead cells as part of a battery 

maintenance program (contractors and others) [P] 

PC13 Supervisors know motor operator and they select competent operators for heavy/difficult 

loads [PST] 

PC14 Pre-operation check by operator – battery OK (water levels, clean, etc.) [P] 

PC15 Operator is experienced enough to recognize abnormal operations (low power) [PST] 

PC16 Battery is charged when trolley wires and gage indicate charge level [WD] 

NI1 Reinforce and follow the requirements of the maintenance program or batteries, consider 

checklists/verification procedure that it is being followed [P] 

NI2 Investigate defining a specific percentage battery charge that is minimum to enter panel 

[P] 

NI3 Add checking gage accuracy in the battery maintenance program [WD] 

NI4 Investigate whether there is an identifiable level of complexity/experience for major loads, 

thereby a list of heavy load operators [P] 

3 – Battery short 

circuit 

PC17 Maintenance battery is cleaned, watered, checked for dead cells as part of a battery 

maintenance program (contractors and others) [P] 

PC18 Pre-operation check by operator – battery OK/ obvious damage [P] 

PC19 Safe Work Instruction and Best Practice Teams sometimes observe pre-op inspections on 

Locomotives [P] 

PC20 Operator is trained to open breakers (2) and take plugs off batteries if there is a short. If 

that doesn’t work, main lead is disconnected [P] 

PC21 Battery rebuilds are done to mine specification [P] 

As above: see PC4 and PC9 

NI5 Reinforce the need to remove any baking soda that has been used to absorb water or 

batteries so that it doesn’t become a conductor (during pre-operation inspection) [P] 

4 – Resistor 

overheating and 

trash on loco hot 

spots burns 

PC22 Resistors are designed to standards and government inspected [MH] 

PC23 Additional fans installed on some locomotives to provide additional cooling [MH] 

PC24 Operator is aware of hot resistors because braking will be reduced and other locomotive is 

then used to brake [PST] 

PC25 Operator stops machinery and lets resistors cool if overheated (breaking reduced) [PST] 

PC26 Resistors are closed in so trash in area is unlikely [MH] 

NI6 Add checking inside the resistor area (lift lid) for any combustibles to pre-operation 

inspection (NOTE that dust can get into resistor compartment) [P] 

123 
 

 

 

 

 

NI7 Investigate changing or modifying resistors to perform under load without overheating 

[MH] 

5 - Brake lockup, 

left on or applied 

due to bleed off, 

causing failure and 

brake fluid/grease 

fire (mantrip) 

PC27 Design to standard/inspected [MH] 

PC28 Pro-operation test brakes before operating equipment [P] 

PC29 Maintenance – brakes are fixed as required [P] 

PC30 Normal braking is electrical so overheating of other brake is unlikely [MH] 

PC31 Operator smells brake heat if park brake left on [PST] 

PC32 There is a red light to indicate brakes are on [WD] 

6 - Fire occurs with 

explosive/oil on 

locomotive 

PC33 Loads are about 10 ft from locomotive heat sources (hydraulic oil/wood equal fuels) [PB] 

PC34 Any explosives are transported in specialized container and hauled separately [PB] 

Top Event = Fire with High-Voltage System 

1 - HV line hit by 

derail/impact form 

load 

PC35 Rail maintenance program where each shift is given an area of track to install and maintain 

(to standards for track installation) [P] 

PC36 There is a pre-shift examination by the mine examiner [P] 

PC37 Locomotive operators report any track issues to supervisor [P] 

PC38 Load guidelines are applied at the mine to avoid oversized/shifting loads that might derail 

the locomotive [P] 

PC39 HV shielded cable, located in rib/roof corner reduces likelihood of damage, there is also 

some guarding [PB] 

PC40 HV circuit breakers/GFCI/pilot circuits protect system from overload/fault/fires and are 

tested and recorded on a monthly basis [MH] 

PC41 HV hung to regulatory requirements [P] 

PC42 Examiner inspects the area including HV [P] 

Top Event = Fire due to welding/cutting 

1 - Trash/loose coal 

in area ignited by 

welding/cutting 

PC43 Each shift is responsible for cleaning up trash in an area [P] 

PC44 Trash is bagged and put on empty car [P] 

PC45 Locomotive operators pick up trash on outby areas around tracks [P] 

2 - Damaged/faulty 

torches or hoses 

lead to fire 

(practices) 

PC46 Mine has strict procedures for cutting and welding underground [P] 

PC47 Qualified person must be present to make CH4 checks including checking area before they 

leave [P] 

PC48 Fire protection and rock dust is included in the procedure [P] 

PC49 Where possible a water line (charged) is also taken to the area [P] 

3 - CH4 blowers 

ignited by 

welding/cutting 

As above: see PC49 about qualified person and CH4 monitoring 

Top Event = Fire on rock duster battery car 

1 - Rock duster 

battery packs 

battery shorts/faults 

PC50 Rock dusters are designed to standard and inspected before underground use [MH] 

PC51 Dedicated crew takes care of charging and inspecting equipment, including operator being 

in the area during operation [P] 

PC52 There is a weekly electrical check of the stone dusting equipment by maintenance [P] 

2 - Compressor 

overheats 

PC53 Compressors are designed to standard and inspected before underground use [MH] 

PC54 There is a weekly electrical check of the compressor equipment by maintenance [P] 

PC55 Operators check oil in compressors [P] 

PC – Prevention Controls 

NI – New Ideas 

MH – Minimize Hazard 

PB – Physical Barrier 

WD – Warning Devices 

P – Procedures 

PST – Personnel Skills and Training 

124 
 

 

 

 

 

 

 

 

Table 57 - Right side BTA for Mine I. 

Consequences Recovery Measures 

Top Event = Fire starts on the Locomotive/mantrip 

Small fire becomes 

big fire (lost assets) 

RM1 All locomotives are fitted with heat sensors and manually initiated fixed fire suppression 

and hand-helds (20 lbs) [WD] 

RM2 Hand helds are located so they can be easily accessed in a fire at battery/brakes/etc. [P] 

RM3 Operators are trained re: hand-held/charged system every 2 years [PST] 

RM4 Fixed and hand-helds are checked regularly [P] 

RM5 Pre-operation checks including making sure hand-held is charged and pinned [P] 

RM6 Persons are trained that an air line can be charged to a two-inch water line to provide fire 

fighting water to the track heading [PST] 

RM7 There is also a return water line that can supply water to fight a fire until air pressure to 

face is lost [MH] 

RM8 There is a real time continuously monitoring system that detects CO located every 2500 

feet in track heading [WD] 

RM9 System is linked to the underground bunker and outside surface hoist house that is 

continuously monitored by a person [P] 

RM10 System alarms at 5 ppm CO (alert) + 10 ppm CO (alarm). System also has a malfunction 

alarm [WD] 

RM11 Person reacts to alarms by notifying shift foreman and persons in area using radio or 

telephone. That person goes to check area with CO detector. [P] 

RM12 There is a CO alarm at the conveyor tail (10 ppm CO) in the panel [WD] 

RM13 The mine has a designated Responsible Persons (RP) who is notified if a fire (small) is 

identified and appropriate other notifications are formalized [P] 

RM14 All persons evacuate the mine if a big fire is identified [P] 

RM15 RP makes decisions about actions to be taken underground to fight fire, change 

ventilation, etc. [P] 

NI8 Make operators aware that, if possible, when there is a small fire or smoke from a 

locomotive/mantrip/rock duster there may be an opportunity to reduce/stop smoke to the 

face by putting equipment into a switch/spur track and open man-door into the return 

heading to short circuit into the return [P] 

Top Event = Fire caused by high-voltage 

Small fire becomes 

big fire (lost assets) 

RM16 Jackets and insulation are fire resistant [PB] 

RM17 System is designed to de-energize quickly (GFCI, etc.) [MH] 

RM18 HV cable hung in a manner (location) so it is not exposed to materials that can come from 

a short, high-temperature heat source [P] 

As above: see RM6 to RM15 

Top Event = Rock duster/compressor fire 

A - Small fire 

becomes big fire 

(lost assets) 

RM19 Equipment has fixed, automatic and manually operated fire suppression on the battery 

areas and mounted hand-helds [PB] 

RM20 Operators are trained every 2 years [PST] 

RM21 Certified contractor does maintenance inspection on the fire suppression system every 6 

months [P] 

RM22 There are weekly inspections to see if system is faulted and if it alarms if faulted or 

discharged [P] 

As above: see RM6 to RM15 

NI9 Investigate whether fixed fire suppression can be located over/at compressor [PB] 

Top Event = Cutting/welding fire 

Small fire becomes 

big fire (lost assets) 

RM23 Hand-helds are part of welding equipment used underground [P] 

RM24 Area will be rock dusted before welding [MH] 

As above: see RM6 to RM15 

NI10 Put one joint of fire hose to be carried on the track jeep at all times [P] 

125 
 

 

 

 

 

 

Top Event = BIG FIRE 

Miners affected by 

smoke at the face 

See previous re: phones, conveyor shut down warning, CO alarms, visible smoke/smell re: warn of 

fire 

RM25 Supervisor maybe present with portable gas monitor to deal with CO level [WD] 

RM26 Persons on face are trained to put on M20* self-rescuers, leave the panel if dense smoke 

is in intake, meet at the power center, grab an extra SCSR, tag together, go to return, and 

use lifeline in return to egress the section (M20 O2 20-minute supply). [P] 

RM27 There is a cache of 1 hour SCSRs at the load center on mobile equipment and caches are 

located 5700 feet in the intake track entry and 5700 feet in the return (staggered every 

2850 feet down panel) [PB] 

RM28 Lifelines lead to caches and there are two cones on line to alert that a door or SCSR cache 

is present [P] 

RM29 There is a practice return egress escape every quarter (intake twice per year and return 

twice per year) [P] 

RM30 Caches are located in cross-cuts with doors in stoppings [PB] 

RM31 Persons are trained to take an extra SCSR [PST] 

RM32 Per MSHA requirements barricading materials have been located in panels and persons 

have been made familiar with methods of building barricades (escape, escape, escape...) 

[PB] 

RM33 There are trained and qualified mine rescues teams available to attempt underground 

rescue [PST] 

RM34 Mine ER Plan includes external and internal communication, external medical services, 

family notification, security, etc. [P] 

NI11 Add clarification to ER training , re: egress in light smoke – i.e. if light smoke in intake 

use transportation to exit as far as possible* then cross to return to egress (* smoke is too 

dense to see ahead) [P] 

NI12 Make sure the caches are located in cross-cuts with doors in stoppings [P] 

NI13 Reinforce the need to put self-rescuer or, if closer by, SCSR on as soon as any smoke is 

detected (issue: smoke may get worse and easier/safer to don SCSR now) [PST] 

NI14 A method should be developed to access stopping doors at caches to check if intake is 

fresh air so that a person can remain attached to lifeline and/or team. The method should 

be included in 90-day ER training. [P] 

RM – Recovery Measures 

NI – New Ideas 

MH – Minimize Hazard 

PB – Physical Barrier 

WD – Warning Devices 

P – Procedures 

PST – Personnel Skills and Training 

126 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

APPENDIX B – Action Plan of New Ideas. 

Identified Potential New Controls Specific Required 

Actions Responsibility Due date 

Design 

Investigate changing or modifying loco resistors to 

perform under load without overheating 

Investigate whether fixed fire suppression can be 

located over/at compressor 

Put one joint of fire hose on loco to be carried on the 

track jeep at all times 

Maintenance 

Reinforce and follow the requirements of the 

maintenance program for batteries, consider that 

checklists/verification procedures are being followed 

Add checking gauge accuracy in the battery 

maintenance program 

Operations 

Investigate defining a specific percentage battery 

charge that is minimum to enter panel 

Investigate whether there is an identifiable level of 

complexity/experience for major loads, thereby 

creating a list of heavy load operators 

Reinforce the need, during pre-operation inspection, 

to remove any baking soda that has been used to 

absorb water or batteries so that it doesn’t become a 

conductor 

Add checking inside the loco resistor area (lift lid) 

for any combustibles to pre-operation inspections 

Make operators aware that, if possible, when there is 

a small fire or smoke from a loco/mantrip/rock duster 

there may be an opportunity to reduce/stop smoke to 

the face by putting equipment into a switch/spur 

track and open man-door into the return heading to 

short circuit into the return 

Fire and Emergency Response

Add clarification to ER training, re: egress in light 

smoke – i.e. if light smoke in intake use 

transportation to exit as far as possible* then cross to 

return to egress [* smoke is too dense to see ahead] 

Make sure the caches are located in cross-cuts with 

doors in stoppings 

Reinforce the need to put self-rescuer or, if closer by, 

SCSR on as soon as any smoke is detected (issue: 

smoke may get worse and easier/safer to don SCSR 

now) 

A method should be developed to access stopping 

doors at caches to check if intake is fresh air so that a 

person can remain attached to lifeline and/or team. 

The method should be included in 90-day ER 

training. 

127 
APPENDIX C – Risk Register 

Hazard/Risk Register Template9

9 Adapted from MIHAP No 3 Planning NSW Hazard Identification, Risk Assessment and Risk Control 

128 

Project No: Section of Facility: Date: Page: 

Description of Scenario: Team Leader: 

Team Members: 

Reference Documents: 

Minutes By: 

Item 

No 

Initiating 

Event 

Description of Potential Consequences (including magnitude 

and Effects) 

Existing Control Measures Description 

of 

Likelihood 

of Potential 

Effects 

(On/off 

site) and 

Likelihood 

Rating 

Risk 

Ranking 

Actions 

Type 

And 

Magnitude 

Description of Potential Effects(on site and off) 

and consequence Rating 

Description Critical 

Control? 

SMS 

Ref 

Performance 

Std NO 

COP 

Data 

Sheet People Biophysical 

Environment 

Property Economic 

Impact 
APPENDIX D - Risk Management Culture and Self-Assessment 

Organizational Progress in Risk Management A number of leading authors on the subject of risk management culture have identified the changing nature of an organization as it 

progresses along its journey of embracing the principles of managed risk. Hudson, Clemmer and Joy have all discussed a 5-stage model to identify an organization’s starting point and gauge the degree of change necessary to effectively implement higher order risk management principles. Measuring where an organization fits in this model is a subjective exercise that evaluates a variety of 

management systems for their relative degree of resiliency. The lowest rung on the ladder or first step in the journey is an organization described as vulnerable, non-caring or pathological. Such 

an organization would view the minimum legal requirements as a significant burden and would be unlikely to pursue formal risk management systems due to the additional obligations of time and resources required. On the other end of the spectrum, the highest 

order organization is described as resilient, fully integrated, or generative. None of the leading practitioners of risk management feel 

they have yet reached this level as an organization. The middle of the journey or ladder is the zone where most mining operations find themselves. A Self-Assessment Tool The following self-evaluation is intended to provide mine managers with a tool to identify the strengths and weaknesses in their 

organization and changes needed for successful implementation of an MHRA. For each category select the description that best fits your mine: Informal Risk Management Systems: 

1. Workers inspect their own workplace, correct as needed, no documentation unless required by law 2. Workers inspect their own workplace, correct as needed, document findings, records retained for review 3. Workers inspect their own workplace, correct as needed, document findings, records retained for review, supervisors randomly 

audit during shift 

4. Workers inspect their own workplace, correct as needed, document findings, records retained for review, supervisors audit 

during shift 

5. Workers inspect their own workplace, correct as needed, document findings, supervisors audit during shift, records reviewed 

by mine management and follow-up actions pursued. 

129 
Task/Job Training Systems: 

1. Peer to peer (Hands-On) task training, no formal documented work practices 2. Peer to peer training based on written work practices that are updated as needed 3. Formal training program using dedicated trainers and written work practices that are updated as needed 4. Formal training program using dedicated trainers and written work practices that are reviewed regularly and the performance 

of the trainers routinely audited. Mine management assigns responsibility for action items 

5. Formal training program using dedicated trainers and written work practices that are reviewed regularly and the performance 

of the trainers routinely audited by local and corporate safety departments. Mine management reports on action items to corporate safety management 

Accident Investigations and Analysis: 

1. The front line or safety supervisor investigates reportable accidents and gives the reports to the safety department for 

processing 

2. The front line or safety supervisor investigates all accidents, including near misses and gives the reports to the safety 

department for processing 

3. A team investigates all reportable accidents and provides a report to management 4. A team investigates all accidents including near misses and provides a report to management. Management assigns 

responsibility for action items 

5. A team investigates all accidents including near misses and provides a report to management. Management assigns 

responsibility for action items. 

Hazard (Fire, Gasses, Dusts, Ground) Monitoring Systems: 

1. Monitoring systems meet minimum legal requirements, reporting as required by law 2. Mostly manual monitoring systems of common hazards with information recorded as required. Action levels require reporting 

to Supervisors for response decisions 

3. Mix of automatic and manual monitoring systems with information recorded and monitored by supervisors in line with formal 

response procedures 

4. Mostly automatic monitoring systems with real time monitoring by supervision and pre-determined automatic responses. 

System performance audited routinely 

5. Mostly automatic monitoring systems with real time monitoring by supervision and pre-determined automatic responses. 

System performance audited routinely. Parameters monitored include potential but not yet regulated hazards to health and safety. 

130 
Monitoring of Behavior: 

1. No monitoring of behavior with respect to safety is done other than what is required by law 

2. Informal behavior monitoring programs have been introduced on some topics. Review of compliance occurs during 

incident/accident investigations 

3. Some behavior monitoring occurs through formal systems and training on selected topics. Investigations of incidents and 

accidents compare behaviors to expectations 

4. Expectations on behavior are well-defined, communicated, formally monitored and periodically reviewed on priority topics. 

Feedback on expectations and compliance obstacles from the workforce is sought and incorporated into expectations 

5. Expectations on behavior are well-defined, communicated, formally monitored and periodically reviewed by all workers on all 

topics. All levels of the workforce serve as monitors and enforcers of expectations. 

Auditing of Expectations: 

1. No auditing of safety performance occur other than by MSHA or State inspectors 2. Auditing is part of accident/incident investigations 3. The safety department conducts a periodic audit for compliance with the rules, MSHA and internal 4. Auditing is done by all levels of management to check for compliance with existing rules and to identify priority issues 5. A formal site-wide monitoring system is in place to both review practices and verify work systems are performing as identified 

in site-specific risk assessments. The site-wide systems are periodically audited by others. 

Culture: 

1. We do what we have to, sometimes we get caught 2. We do the best we can, discipline those who don’t 3. We put every effort into complying with the law every day. We change systems when we have trouble with compliance. We 

get few citations 

4. The front line managers lead the safety department in identifying problems and solutions. MSHA isn’t much of a problem 

because we always do more 

5. All levels of the organization promote safety as the first priority. Regulators look at us as an example of how to manage 

hazards. Proposed new rules are already a way of doing business here. 

131 
Evaluation and Paths to Progress:

Add the numbers of each selected response for your score to determine where you stand with suggestions on paths to improvement:7-10 Vulnerable: Accept the need for change. Embrace informal risk assessment tools. Follow accidents and incidents with investigations that produce JSAs to prevent a reoccurrence. 11-17 Reactive: Understand human error and accept that most of it is unintentional. Formalize standard procedures and minimize 

reliance on administrative controls. Expand investigations beyond serious incidents. 

18-24 Compliance Driven: Emphasize quality and competency of training over time. Pursue formal risk assessments on topics which 

have not yet been a problem. Increase internal monitoring to ensure conformance. Increase consulting within all levels of theworkforce for acceptable solutions. 26-31 Proactive: Fully integrate risk management into all decision systems and projects. Shift focus on eliminating rather than managing hazards. Drive controls up the hierarchy. Open communications within the organization. Seek out 3rd-party auditing. 

32- 35 Resilient: You apparently don’t need this document. The steps along this path are like the steps along a journey. This journey is one of building a strong culture of safety (Figure 40). 

132 

Reactive

Proactive

Reactive

Proactive

Way we do 

Tune the business 

system Prevent 

thru incidents 

Compliant

Resilient

Vulnerable

Reactive 

CompliantCompliant 

Proactive 

Resilient 

Vulnerable Vulnerable 

Prevent a ownership before they Accept si that similar 

incidents occur 

happen 

incident 

Figure 40 - Steps along the path to an improved safety culture. 
Delivering on the Nation’s promise:

safety and health at work for all people

through research and prevention

To receive NIOSH documents or more information about

occupational safety and health topics, contact NIOSH at

1–800–CDC–INFO (1–800–232–4636)

TTY: 1–888–232–6348

e-mail: cdcinfo@cdc.gov

or visit the NIOSH Web site at www.cdc.gov/niosh. 

For a monthly update on news at NIOSH, subscribe to

NIOSH eNews by visiting www.cdc.gov/niosh/eNews. 

DHHS (NIOSH) Publication No. 2009-104 

SAFER • HEALTHIER • PEOPLETM