Using Major Hazard Risk Assessment to Appraise and Manage

Escapeway Instability Issues: A Case Study

Anthony T. Iannacchione, Principal Research Engineer 

Gabriel S. Esterhuizen, Sr. Research Fellow

Stephen C. Tadolini, Principal Research Engineer 

NIOSH-Pittsburgh Research Laboratory 

Pittsburgh, PA

ABSTRACT 

A Major Hazard Risk Assessment (MHRA) was developed in 

Australia after a series of mine disasters in the 1990’s. A MHRA is 

used to help prevent major hazards, i.e. fire, explosion, wind-blast, 

outbursts, spontaneous combustion, roof instability and chemical 

and hazardous substances, from injuring miners. A MHRA is a 

structured process that identifies the characteristics of major 

hazards, assesses and ranks the risk they present, and evaluates 

engineering and administrative controls to mitigate them. These 

controls typically consists of a broad spectrum of prevention, 

monitoring, first response, and emergency response techniques and 

helps to move an operation from a reactive to a proactive approach 

towards safety. 

This paper documents a MHRA performed at an underground 

mine where strata instabilities and fire hazards may threaten the 

condition of its escapeways. The objective of this MHRA is to 1) 

identify what hazards could affect the egress through the mine’s 

escapeways, 2) determine what unwanted events pose the greatest 

threat for the mine, and 3) recommend a plan to prevent or recover 

from the potential disruption of egress through the escapeway. The 

plan provides information on the key existing controls that should 

be monitored and audited, and makes recommendation of new 

potential controls to further reduce related risks. By documenting 

the use of MHRA to this specific ground control issue, this paper 

provides a framework for others to judge the merits of this 

approach and to help design and perform these activities. 

INTRODUCTION 

Recent mining disasters have focused attention on the need to 

improve how major hazards, the kind that are associated with 

multiple fatalities in underground mines, are assessed and managed. 

The Australia minerals industry began their movement towards 

risk-based management systems in the mid-1990’s, shortly after the 

Moura coal mine explosion in 1994 fatally injured 11 miners 

(Hopkins, 2000). As a result, industry began using risk analysis 

methods to mitigate certain key hazards. 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 

it own standard. These regulations require mines to perform Major 

Hazard Risk Assessments (MHRAs) on a regular basis to address 

the possibility of unwanted events like spontaneous combustion, 

gas outbursts, explosions, air blasts, inundations and roof falls. The 

Australian underground mining industry now is realizing some of 

the lowest fatality injury rates in the world, even lower than that of 

the U.S. (table 1).

Table 1. Average fatality rates for underground mining in U.S. 

and Australia from 2004 to 2006 based on the number 

of fatal injuries per 1 million hours worked. 

Commodity Avg. fatality rate 

U.S. Coal 0.25 

Metal/nonmetal 0.14 

Australia Coal 0.04 

Metalliferous 0.07 

 The National Institute for Occupational Safety 

and Health (NIOSH) has undertaken a pilot project to evaluate 

MHRA potential for US mines through a series of case studies 

across several mining sectors. The purpose is to validate the use of 

this technique and to identify obstacles to its successful 

implementation in the U.S. mining industry. This case study 

examines the roof instability hazard and provides an example as to 

how MHRA could help to mitigate risk. 

The general conditions found at the study site are shown in 

figure 1. The part of the mine that comprises the study area was 

mined over 40 years ago using the room-and-pillar technique. 

Large rooms were driven 45 ft (13.7 m) wide and 30 ft (9.1 m) high 

perpendicular to a highwall in an adjacent quarry and off-set crosscuts of the same size were mined typically on 90 ft (27.4 m) 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 (76.2 m) 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 shown in figure 1. 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. 
 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 1).

Portal 1 Highwall

Portal 2 

Surface Quarry

Primary 

Escapeway

AlternateAlternate 

Escapeway

Jan. 94 

Roof Fall

RestrictedRestricted 

Are a

Feb. 07 

Roof 

Cra cks

Jan. 07 Roof Jan. 07 Roof Fa ll 

and Associated and Associated 

Roof Cracks

Figure 1. Escapeways, roof falls and recent roof cracks found 

at the mine. 

 One of these roof cracks is 

especially troublesome because it extends across the Alternate 

Escapeway and into the Primary Escapeway, signaling an elevated 

risk. 

 The objective of the MHRA is to: 

1. Identify hazards that could affect egress through the mine’s 

escapeways, 

2. Determine what unwanted events pose the greatest threat for 

the mine, and 

3. Recommend a plan to prevent, or recover from, potential 

disruption of escapeway egress. 

INITIAL STEPS OF THE ESCAPEWAY EGRESS 

RISK ASSESSMENT 

 The initial MHRA steps consist of scoping document 

generation, scoping team selection and assessment framework 

identification. 

 The Scoping Document: A scoping document identifies the 

MHRA tasks. First, major hazards associated with egress through 

Primary and Alternate Escapeways during an emergency at mine 

should be reviewed. Consequences associated with the unwanted 

event are investigated and the likelihood of the event occurring 

should be estimated. Threats that disrupt egress through the 

escapeway are to be analyzed and ranked using a risk matrix 

technique. Finally, existing and new controls and recovery 

measures will be identified. 

 The Scoping Team: The scoping team consisted of the 

following persons: 

Mine Representatives

Mine Manager 

Mine Engineer 

Rock Mechanics Engineer

Miner

Safety Officer 

Facilitators (Risk Assessment Experts)

Experts (Field of Expertise)

Ground Control Engineers

Ventilation Engineer 

Mining Regulation Specialist 

Mine Evacuation Specialist 



The Assessment Framework: The Scoping 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. A time period of five years was used for 

considering hazards and risks.

IDENTIFY HAZARDS THAT AFFECT EGRESS

UGH THE MINE’S ESCAPEWAYS

 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.

 Segments of the Escapeway System: 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 are subdivided into six segments (figure 2). 

Portal 1 Highwall

Portal 2

Surface Quarry

1 3 2 4

LEGE ND

5 Primary escapeway

Alternate escapeway

6Segment number 6

Figure 2. Six segments of the mine’s escapeway system. 
Hazards: A hazard is a source of potential harm with the 

potential to cause loss -- an uncontrolled exchange of energy 

(Standards Australia, 2004). 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 2. 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. 

Table 2. Fire hazards consisting of potential fuel and ignition 

sources. 

Fuels 

Diesel equipment – truck, front end loader, backhoe, 

grader, crane, scoops and other smaller 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 

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 3. Higher values indicate increasing risk of roof collapse in 

the absence of additional roof stabilization efforts. For example, 

the relative roof fall risk in Segment 1 of the Primary Escapeway is 

potentially lower than Section 2 because this section contains roof 

bolts, wire mesh and narrower entry spans. 

Portal 1

Highwa ll Portal 2

Po

al hw ig H

Portal 1

tal 2 

e QfS yrrauacru

eRFRI m asur

saear

tenme

Surface Quarry

RFRI measurement 

areas

Figure 3. Roof fall risk index (RFRI) measured in the mine’s 

escapeways. 

DETERMINE WHICH UNWANTED EVENTS POSE 

THE GREATEST THREAT 

The hazard assessment followed a structured process which 

relies extensively on qualitative risk analysis methods. After the 

scoping team is familiar with the escapeway routes, current ground 

conditions, ventilation and operational requirements, the risk for a 

potential unwanted event in each segment are determined. The risk 

associated with unwanted events are rated using the Broad Brush 

Risk Assessment (BBRA) method which considers the likelihood 

and consequences of each event. 

Table 3. Roof and rib hazards capable of blocking 

escapeway egress. 

Hazards Roof falls

 Rib instability 

Degree of hazards Roof Fall Risk Index (RFRI) variations 

Rock reinforcement and room spans 

variations 

Broad Brush Risk Assessment: The scoping team identified 28

potential unwanted events based on the defined list of hazards 

(tables 2 and 3). Each potential unwanted event was risk-ranked 

using a qualitative risk analysis method (table 4).

Table 4. A 4 by 5 risk matrix for ranking the unwanted events. 

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 

 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. 

The results of the risk rating exercise are summarized in table 5. 

Table 5. Risk ranking of unwanted events grouped by escapeway segment. 

Escapeway 

Segment Potential unwanted event Consequence 

(impact) 

Likelihood (next 5 

years) Risk ranking 

Equipment fire – fan exhausting High Unlikely 7 

1 

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 

Roof collapse High Likely 4 

2 Equipment fire - fan exhausting High Very Unlikely 11 

Equipment fire – fan blowing High Very Unlikely 11 

Electrical Cable fire Low Very Unlikely 18 

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 

3 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 

Equipment fire – fan exhausting High Very Unlikely 11 

4 Equipment fire – fan blowing High Very Unlikely 11 

Roof collapse Moderate Very Likely 5 

Equipment fire – fan exhausting High Unlikely 7 

5 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 

EVALUATING THE CONTROLS AND RECOVERY

MEASURES FOR THE TOP UNWANTED EVENTS

The top four unwanted events identified through the BBRA are 

selected for further analysis. 

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 

The Bow Tie Analysis (BTA) is an excellent method for 

identifying both existing and new control and recovery measures 

for these highest risk events. 

The Bow Tie Analysis 

The BTA was developed by Shell Oil in the 1980’s as part of 

their Tripod package of concepts and tools for managing 

occupational health and safety in their business. It is important to 

note that the “Top Event” in the BTA is not the full event 

considered in the BBRA but rather a statement about the initiating 

event that might lead to the major consequence (figure 4). 

PREVENTION 

RECOVERY Potential 

causes 

Potential 

outcome 

Control 

measures 

Recovery 

measures 

Threat Consequence 

Threat 

Threat 

Consequence 

Consequence 

PREVENTION

RECOVERY Potential 

causes

Potential 

outcome

Control 

measures

Recovery

measures

Top unwanted 

event 

T

Threat Consequence

Threat

Threat

Consequence

Consequence

op unwanted

event

Figure 4. Bow Tie Analysis method. 
The team discussed the nature and quality of the prevention 

controls as part of the BTA. Threats (also referred to as potential 

causes) were 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 were identified and recovery control measures examined to 

reduce or minimize the loss (right side of the bow-tie). The 

outcomes of the bowtie analysis are presented in table 6 and 

summarized below: 

Table 6. Controls and recovery measures for top unwanted events that impact escapeway egress. 

Top Event Î Escapeway egress is partially or totally blocked Control measures 

Threat 1 - Roof collapse 

in Primary Escapeway 

Segment 3 

Primary support – 6 and 8 ft (1.8 and 2.4 m) grouted bolts 

Scale roof and ribs every 3 to 6 months, or as needed 

Random observation of roof conditions 

NEW IDEAS(1): Immediately implement a regularly scheduled roof conditions visual 

observation plan 

NEW IDEAS(2): Design and install a monitoring system for roof crack and roof sag 

detection 

NEW IDEAS(3): Design a method of stabilizing the roof in this area based on the 

information gathered from the roof monitoring program 

NEW IDEAS(4): Consider stabilizing the adjacent Alternate Escapeway (Segment 4) to act 

as a buffer for securing this area 

Threat 2 - Charging 

station fire in Primary 

Escapeway Segment 3 

Battery water levels and terminals are checked weekly 

NEW IDEAS(5): Place charging station outside mine 

Threat 3: Roof collapse in 

Alternate Escapeway 

Segment 2 

Monitoring with multipoint extensometers 

Cable bolt support with steel screen 

Observation of roof conditions 

Breaker wall standing support 

NEW IDEAS(6): Develop a trigger action response plan (TARP) for roof movement that 

will initiate additional rock reinforcement installation 

NEW IDEAS(7): Repair/replace existing multipoint extensometers 

Threat 4 - Roof collapse 

in Alternate Escapeway 

Segment 4 

Scale roof and ribs every 3 to 6 months, or as needed 

Random observation of roof conditions 

Monitor microseismic emissions from the mine (just begun) 

NEW IDEAS(2): see above 

NEW IDEAS(3): see above 

NEW IDEAS(8): Develop a policy to restrict access except in an emergency situation 

Recovery measures 

Consequence 1 – Roof 

collapse blocks the 

Primary Escapeway 

NEW IDEAS(9): Consider installing refuge chambers in the active work areas 

NEW IDEAS(10): Consider using the ventilation shaft as an Alternate Escape route 

Consequence 2 – 

Charging Station Fire in 

Primary Escapeway 

Station is partially enclosed by a cinder block wall and metal roof 

Scoop has fire suppression system 

Fire extinguishers are present, although current policy is to evacuate rather than fight fire 

Main office is contacted via radio 

Use radios to communicate fire alarm to everyone underground 

Sound the siren 

Life lines exist in part of the Primary Escapeway 

NEW IDEAS(11): Install backup generator for communication system 

NEW IDEAS(12): Install fire detection/suppression systems on large diesel equipment 

NEW IDEAS(13): All personnel and visitors to wear SCSRs (training needed) 

NEW IDEAS(14): Close down charging station when the general public is underground 

NEW IDEAS(15): Finish installing life line in all escapeways 

Consequence 3 - Roof 

collapse blocks the 

Alternate Escapeway 

NEW IDEAS(9 & 10): see above 

Consequence 4 - Roof 

collapse blocks Alternate 

Escapeway 

NEW IDEAS(9 & 10): see above 

a. Existing prevention control measures: The following are 

the key controls, currently in place, for the highest risks 

unwanted events. These existing control measures should 

be reinforced, monitored and audited with priority. 

Controls for roof collapse hazards consisted of 6 and 8 ft 

(1.8 and 2.4 m) grouted bolts on 5 ft (1.5 m) centers; 

scaling every 3 to 6 months or as needed; periodic 

observation of roof conditions, roof monitoring; cable bolt 

support with wire mesh; and breaker wall standing support 

between the Alternate Escapeway and the restricted area. 

Fire hazard controls consists of weekly battery checks. 
b. Existing recovery measures: The existing recovery 

measures for a large roof collapse, capable of blocking the 

Primary or Alternate Escapeways consist of developing 

new escapeway routes or rehabilitating the roof fall area. If 

a fire occurred in the charging station area, a cinder block 

wall and metal roof could partially contain the fire. Fire 

extinguishers are present in this area, although current 

policy is to evacuate rather than fight the fire. Several 

pieces of diesel equipment have fire suppression systems. 

In the event of an evacuation, radio communication, 

directed by the mine office, would be used to communicate 

a fire alarm. A site wide siren is also available. Lastly, life 

lines exist in part of the Primary Escapeway. 

c. Potential new prevention controls: Fifteen new control 

ideas were identified. These new 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. A number of monitoring controls 

were discussed including: a regularly scheduled visual 

observation plan of roof conditions; installation of 

additional roof and crack monitors and a trigger action 

response plan (TARP) for monitors. New ideas for 

preventing roof collapse hazards include a supplemental 

rock reinforcement program for segment 3 of the Primary 

Escapeway and a stabilization design for segment 4 of the 

Alternate Escapeway. The new control for the fire hazard 

was to place the charging station outside the mine. 

d. Potential new recovery measures: Several new recovery 

measures were identified. To mitigate the impact of a roof 

collapse, the existing ventilation shaft could be used as an 

Alternate Escapeway. Also, a rescue chamber could be 

installed in active work areas. New ideas to help recover 

from the fire hazard included using a backup generator for 

the communication system; installation of additional fire 

detection/suppression systems; elevated Personal Protective 

Equipment requirements; limited charging station use; and 

install life lines in all escapeways. 

Action Plan: These new control and recovery measure ideas 

should be addressed through the development of an Action Plan. 

The Action Plan with the ideas inserted and space left for 

derivation of specific actions, timing and resourcing is provided in 

table 7. 

Table 7. Example of an action plan for the new ideas developed by the scoping team. 

Identified Potential New Controls Specific Required 

Actions Responsibility Due date 

1) Immediately implement a regularly scheduled roof conditions 

visual observation plan 

2) Design and install a monitoring system for roof crack and roof 

sag detection 

3) Design a method of stabilizing the roof in this area based on 

the information gathered from the roof monitoring program 

4) Consider stabilizing the adjacent Alternate Escapeway 

(Segment 4) to act as a buffer for securing this area 

5) Place charging station outside mine 

6) Develop a trigger action response plan (TARP) for roof 

movement that will initiate additional rock reinforcement 

installation 

7) Repair/replace existing multipoint extensometers 

8) Develop a policy to restrict access except in an emergency 

situation 

9) Consider installing refuge chambers in the active work areas 

10) Consider using the ventilation shaft as an Alternate Escape 

route 

11) Install backup generator for communication system 

13) Install fire detection/suppression systems on large diesel 

equipment 

14) Close down charging station when the general public is 

underground 

15) Finish installing life line in all escapeways 

DISCUSSION 

The attributes of this process are many. It helps to utilize the 

strengths of a team of experts familiar with the hazards being 

addressed. Risk analysis methods are used to focus the team on the 

highest ranked risk and to analyze these risks in a structured 

manner. The mine’s current control and recovery measures are 

identified so that they can be monitored and audited. New potential 

control and recovery measures are produced for consideration by 

management. These new ideas are easily listed in the form of an 

action plan. The plan can then be delivered to management for 

prioritization and implementation. 

A weakness in this approach has to do with the expectation that 

a specific design will be a direct outcome of the activity. Detailed 

designs are not easily accomplished in a MHRA exercise. 
SUMMARY 

This paper provided a case study example as to how the MHRA 

approach, as practiced in Australia, might be used to mitigate the 

risk of roof instability and fire hazards in US underground mines. 

The major threats to escapeway egress are identified as well as an 

inventory of existing controls and recovery measures specific to 

each threat. New ideas are presented in an action plan for 

management consideration. All this is accomplished in a structured, 

group-oriented activity designed to produce a written report. 

MHRA promotes a more proactive approach to dealing with a 

mine’s major hazards. 

REFERENCES 

CFR (2005). Escapeways,” Code of Federal Regulations, Part 30, 

Section 57.11050. 

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 

16(1):29-36. 

Iannacchione, A.T., Esterhuizen, G.S., Schilling, S. and Goodwin, 

T. (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., Esterhuizen, G.S., Prosser, L.J. and Bajpayee, 

T.S. (2007). Technique to Assess Hazards in Underground Stone 

Mines: The Roof Fall Risk Index (RFRI). Min Eng 59(1):49-57. 

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. 

Standards Australia (2004). Risk Management. Standards 

Australia/Standards New Zealand, Sydney, AS/NZS - 4350:2004.