Iannacchione, A.

Mark, C.

 

Major Hazard Risk Assessment Applied to Pillar Recovery Operations 

A.T. Iannacchione, Associate Professor
 

University of Pittsburgh
 

Pittsburgh, PA
 

Chris Mark, Principal Research Engineer
 

NIOSH Pittsburgh Research Laboratory
 

Pittsburgh, PA
 

ABSTRACT 

Recent fatal injuries occurring during pillar retreat coal mining 

call for better identification of the hazards and recognition of risks. 

Ground control hazards associated with room-and-pillar retreat 

mining tend to intensify with depth, requiring extra precautions in 

the form of additional controls. In many locations these activities 

are further complicated by local complexities often associated 

with unique or novel circumstances, such as over-mining or undermining. 

One technique recently studied by NIOSH, Major Hazard Risk 

Assessment (MHRA), may help mine operators to mitigate the 

risks associated with pillar recovery operations. The approach was 

trialed at two underground coal mines in southern West Virginia 

that are currently practicing pillar recovery. The first step in the 

MHRA process involved reviewing the segments or parts of the 

pillar extraction mining system and identifying associated hazards 

and threats to the operation. Some of the high risk hazards at these 

two sites included: 

•		Rock fall during pillar extraction covers equipment and injury 

occurs during recovery operations, 

•		Rock fall above the roof bolt horizon, potentially injuring 

workers and/or requiring recovery action, 

•		Rib fall under deep cover, potentially injuring workers, and; 

•		Strata instabilities associated with subsidence of the 

interburden due to simultaneously mining two seams in close 

vertical proximity to one another. 

The mines’ risk assessment teams then considered each threat 

individually in order to systematically identify potential unwanted 

events. The top unwanted events were examined individually using 

structured risk analysis tools. The output from the process includes 

a list of priority existing controls for monitoring and auditing, and a 

second list of potential new controls. These controls consisted of: 

•		Examples of best practices, 

•		Enhanced communication, 

•		Implementing standard operating procedures (SOP), 

•		Protocols for emergency response actions, 

•		Effective layouts, 

•		Efficient monitoring, and; 

•		Successful audits. 

This paper documents the process as it unfolded at the two 

mines, and analyzes the strengths and weaknesses of the MHRA 

technique as it applies to pillar recovery operations. 

This work was part of a larger NIOSH research project. 

NIOSH was responsible for: 1) facilitating the risk assessment 

process known as Major Hazard Risk Assessment (MHRA), 2) 

documenting the risk assessment process, and 3) providing mine 

management with a written draft summary of the risk assessment 

process. The results of the risk assessment represent the thoughts 

and opinions of the individual risk assessment teams and should 

in no way be construed as an endorsement of the risk assessment 

output by NIOSH or the University of Pittsburgh. 

INTRODUCTION 

Recent fatal injuries occurring during pillar retreat coal mining 

call for a better identification of the hazards and a recognition of the 

associated risks. Ground control hazards associated with room-andpillar retreat mining tend to intensify with depth, requiring extra 

precautions in the form of additional controls. In many locations, 

these activities are further complicated by local complexities often 

associated with unique or novel circumstances, such as over-mining 

or under-mining. In this study, two sites were chosen where pillar 

recovery at depth was occurring. 

SITE CHARACTERISTICS OF MINE A 

Mine A has been active for over 30 years and most of the 

virgin coal has been mined using the longwall method. In 2006, 

operations shifted to mining the remaining isolated pockets of coal, 

not minable by the longwall method. Some of these pockets consist 

of large barrier pillars adjacent to the mines’ main entry system. 

The barrier pillar studied in this paper is located in the southern 

portion of the mine along the main entry system that travels from 

south to north. The barrier pillar is approximately 480-ft wide and 

several thousand feet long (Figure 1a). Overburden ranges from 

greater than 400 ft over the northern end of the barrier to greater 

than 1,200 ft over the southern end (Figure 1b). Lastly, a coalbed 

lays approximately 190 ft above the study panel and is partially 

mined (Figure 1c). 
Figure 1. a) View of study barrier pillar, b) overburden above 

study area, and c) location of overlying mine workings. 

SITE CHARACTERISTICS OF MINE B 

Mine B often extracts coal under ridge tops where the 

overburden is sometimes greater than 1,000 ft (Figure 2). To date, 

the coal has been mined using the room-and-pillar method. Rooms 

are typically 19- to 20-ft wide and pillar centers range from 70 

to 90 ft. The mining height is approximately 6 ft. Recently the 

mine began to use full extraction mining methods concentrated 

in production panels located adjacent to its main entry systems 

(Figure 2). Underground conditions are further complicated 

by multiple-seam mining. The study mine is the lowest minable 

coalbed within the geologic section. Above it there are a 

significant number of mineable coalbeds. Approximately 80 ft 

and 160 ft above the study mine lay a dozen mining operations, 

most abandoned. The diverse arrangements of rooms, pillars, 

and gob (areas where the coal pillars have been extracted) 

have added to the already complex pillar loading conditions. 

Projected 

mine 

workings 

Overburden 

> 1,000-ft

Mine 

workings
 N 

Previous 

pillar 

sections 

Figure 2. Site characteristics of Mine B: current and projected 

mine workings, previous pillar sections, and overburden greater 

than 1,000 ft. 

RISK ASSESSMENT OBJECTIVES 

The ground control issues associated with retreat mining deep 

cover coal warrant the study of additional means to prevent worker 

injuries. One approach that has gained some favor in other mining 

countries (Anon, 1997; Iannacchione et al., 2008) is Major Hazard 

Risk Assessment (MHRA). In this approach, mining operations 

focus on hazards that can cause significant risk to the mine and its 

workers. To investigate the mine’s hazards, the risk assessment 

team identifies potential hazards and ranks these hazards by their 

likelihood of occurrence and consequence to safe operations of the 

mine. The risk assessment team provides a list of priority existing 

controls for monitoring and auditing, as well as a list of potential 

new controls to further reduce related risks. 

RISK ASSESSMENT TEAM 

The risk assessment teams at both study sites were made up of 

persons employed at the mines (Table 1). 

Table 1. Composition of risk assessment teams at Mine A 

and B. 

Mine A Mine B

Mine Superintendent Owner 

Chief Mine Engineer General Manager 

Mine Engineer Mine Superintendent 

Safety Department Mine Foreman 

MRS Operator Day Shift Foreman
 

Safety Manager
 

Mine Superintendent from a 

another mine 

NIOSH contributions, Facilitator and Ground Control Expert 

THE MHRA PROCESS 

To accomplish the risk assessment objectives stated above, 

a process known as Major Hazard Risk Assessment (MHRA) 

was undertaken at both study sites. The MHRA process was 

developed by Dr. J. Joy (Joy, 2004 and Joy, 2006) at the University 

of Queensland’s Minerals Industry Safety and Health Centre 

(MISHC). MHRA consists of multiple steps that culminate in an 

inventory of existing prevention controls and recovery measures 

and an Action Plan for evaluating new ideas developed by the risk 

assessment team. For a more detailed description of the MHRA 

process, consult NIOSH IC 9508 (Iannacchione, et al., 2008). 

This paper describes the steps used in this study to accomplish the 

project objectives. 

Step 1 - Parts of the Pillar Retreat Process 

Before any controls are identified, the risk assessment team 

must thoroughly understand the process they are going to evaluate. 

In this study, the parts of the pillar retreat process are attained 

by analyzing all associated procedures, methods, and actions. 

Typically, pillar retreat systems have four distinct activities: 

engineering / approval, construction, development mining, and 
retreat mining. Each of these activities could be evaluated with 

the MHRA process. For complex operations like pillar recovery, 

identifying all the important parts and/or actions can require from 

a few hours to more than a day of the risk assessment team’s time. 

This study focused on two of these activities: development and 

retreat mining. The discussion below only represents a summary of 

the most significant actions for each study site. 

Mine A Process Summary 

Numerous actions are involved in developing rooms and 

crosscuts within a large barrier pillar. Typically rooms are 18 

ft wide but can be as wide as 20 ft. Two distinct layouts were 

proposed: a 5-entry development and a 6-entry development. The 

5-entry layout begins development mining from the south end of 

the barrier pillar where an overlying mine has previously been 

developed. Pillars will be mined on 90 by 90-ft centers with the 

exception of one-row of pillars on the west side of the development 

where 65 by 90-ft centers will be used (Figure 3). Pillars in the 

5-entry development area are not to be extracted because of 

mining in the overlying coalbed (coal-gob interface). The 6-entry 

development is proposed to have 105 by 65-ft centers (Figure 3). 

This layout will be used for the remainder of the barrier pillar. At 

the north end of the barrier pillar, several entries are to punch out 

into the adjacent sub-mains. The barrier pillar, when developed, 

will contain two, much smaller, remnant barrier pillars (Figure 

3). On the east side, the new barrier pillar width ranges from 76 

to 90 ft. On the west side, the barrier width ranges from 59 to 62 

ft along the 6-entry development and 62 to 73 ft along the 5-entry 

development.

Longwall panel 

No Second Mining 

Mains 

2 East Barrier Pillar 

6-Entry 

5-Entry 

Figure 3. Detailed layout map of the Barrier Pillar, Mine A. 3 West Submains N 

Retreat mining will commence after the entire barrier pillar has 

been developed. Two rows of pillars are left to protect the bleeders 

at the north end of the barrier pillar. Cable handling issues require 

that the section be mined from right to left. Blowing ventilation 

with check curtains are used to force the fresh air to the heading 

where the mining machine and Mobile Roof Supports (MRS) are 

positioned (i.e. Room No. 1, Figure 4). 

1 - Room Num ber 

L - Leave 

C - Check Curtain 

- Regulator lR 

ll - Stopping 

- Conveyor Belt 

- Breaker Post 

- Pillar Center Line 

Figure 4. Initial pillar extraction layout at the north end of the 

barrier pillar near the Sub-main. 

Prior to extracting the first pillar, a star cable bolt pattern is 

installed in every intersection, starting 4 rows outby the sub-mains. 

Two rows of breaker posts are installed, 4 in-a-row, just inby the 

pillar to be mined. Due to the right handed nature of the power 

cable and connectors, the first cut into a pillar is always taken to 

the left (Figure 5), allowing the miner operator to be positioned 

next to solid coal. Mine management determines the depth of the 

lift and marks each cut position on the coal block and provides the 

depth information to the miner operator. The miner operator uses 

markings on the continuous mining machine to measure depth of 

the cut. Eight breaker posts (Position A, Figure 5) are installed 

after mining is completed inby. Two cribs may be used in lieu of 

breaker posts. The MRS units are installed in locations B (Figure 

5) prior to mining lift No. 1. MRS units are moved to location C 

(Figure 5) prior to mining lift Nos. 3 and 4 and are advanced in 

like manner for each subsequent lift. Thin fenders of coal are 

sometimes left between lifts. The miner operator has the option to 

mine these fenders on the way out of the lift. Some operators use 

these fenders as an early warning device to determine high rates 

of roof-to-floor convergence. After all lifts are taken, the miner is 

moved to the next heading to the left of its original position and the 

process is repeated. 

Mine B Process Summary 

Mine B is in the process of developing production panels to 

the east of a main entry development (Figure 6). Each panel is 

developed to its full length and connected into the bleeder entries 

at its inby end. After the panels are developed, full extraction pillar 

mining begins at the inby end of the panel and continues outby until 

it reaches the main entry developments. 

Initially, contract surveyors identify pillar centers and set 

spads. Headings are advanced in a three cut sequence. Crosscuts 

are turned in two ways: 1 one turn from the No. 4 entry and 2 

two turns from the No. 3 and No. 5 headings. These entries have 

slightly wider diagonals because of the rounded pillar corners 

to accommodate the turning continuous miner. The primary roof 

support consists of 5-ft, fully-grouted bolts. Typically, the sum 

of the intersection diagonals is 58 to 60 ft. If the intersection 

diagonals exceed 62 ft, 4 cribs are set per intersection. If the 

intersection diagonals exceed 64 ft, 8 cribs are set per intersection. 

All developments will be stopped 200 ft from the known locations 

of old workings. A blowing mine ventilation system is used as a 

means of creating positive pressure in the working sections. At the 

face, an exhausting face ventilation system is used. 

Retreat mining commences at the completion of development 

mining. Star cable bolt patterns are installed in all intersection 

except when massive sandstone is present. The depth of the mining 

cuts is controlled by markings on the continuous miner. The section 

is mined left to right. The Foreman marks all cuts, fenders, and 

stumps with strips of red spray paint on the roof and rib of the 

pillar. Typically a strip of thick coal is left in the center of the 
M R S A B r e a k e r 

U n it s p o s t 

B 

1 

C 

B 2 

P r e v io u s ly 

M in e d 

Lif t s 

P u s h o u t 

M R S 

U n it s 

Figure 5. Deep cut full extraction pillar recovery plan for twinning large coal blocks using two pairs of MRS. 

Belt Entries Bleeder 

Entries 

Figure 6. Detailed view of the projected production panels where pillar recovery will occur. 
 

pillar. The final cuts are taken from the crosscut, outlining a final 

stump with minimum cut-to-corner distances of 8 ft. Eight breaker 

posts are set, 4 per row, prior to mining. The MRSs are set within 

the breaker post array and flush with the pillar edge (Figure 7). The 

breaker posts are set within the entries of all outby blocks prior to 

moving to the next pillar row. A 2-ft-thick fender is left between 

pillar extraction cuts to keep small rocks off the continuous miner. 

Only one MRS is depressurized at a time and leapfrogs past the 

adjacent pressurized MRS. When backing out of a section, the 

MRS is depressurized and moved to a position half way back from 

the tip of the set MRS and re-pressurized. Three coal haulage cars 

(buggies) are used to quickly remove the coal from the continuous 

miner, minimizing the miner’s time in the cuts. 

A 

A 

A’

A’

B’

B’

B 

B 

Scale, ft 

GOB 

1 2 

13 

12 

10 

11 

9 

7 8 

5 

3 

6 

4 

0 10 

70’

19’

13’

40’

8’

Leave 

90’

Figure 7. Cut sequence used to fully extract 90 by 70-ft pillars. Note the location of the 8 by 8-ft final stump. 

Step 2 - A Comprehensive List of Hazards 

Due to time constraints, the teams decided to limit their 

consideration of hazards to those associated with ground control 

and not to consider ventilation issues such as fires and explosions. 

The risk assessment teams identified the big energies as stresses, 

pressure, gravity, gas, and water. They also recognized eight 

associated hazards (Table 2). 

Table 2. List of general ground control hazards associated 

with pillar retreat mining. 

Energy Hazards 

Stresses Bumps Pillar instability 

Pressure Air blast from gob 

caving event Support failure 

Gravity Roof falls Rib instabilities 

Gas and Water CO, CO2, CH4 

from adjacent gob 

Water from 

overlying 

abandoned mine 

Step 3 - Risk Ranking Potential Unwanted Events 

Once the pillar retreat mining segments or parts and the 

associated hazards are identified, the team is ready to apply the 

risk assessment methods. This step has the risk assessment team 

develop a list of potential unwanted events. A risk ranking is 

then performed using a broad-brush risk assessment tool, such 

as the Workplace Risk Assessment and Control (WRAC) or the 

Preliminary Hazard Analysis (PHA), to identify the unwanted 

events that presented that greatest risk. 

Mine A’s Most Significant Potential Unwanted Events 

Mine A identified 25 potential unwanted events (Table 3). Risk 

numbers (R) were assigned using risk matrix technique and ranged 

in value from 2 to 25 (Anon., 1997). The lower the number, the 

greater the risk to the mining operation. The risk rankings are 

grouped into five categories: very low (VL), low (L), medium (M), 

high (H), and very high (VH). There are three potential unwanted 

events that are in the high and very high risk categories (# 7, #16, 

and #22, Table 3). 

Mine B’s Most Significant Potential Unwanted Events 

Mine B identified 12 potential unwanted events (Table 4). Risk 

numbers ranged from 4 to 20. There are three potential unwanted 

events that are in the high risk category (#1, #4, and #12, Table 4). 

Step 4 - Determine All Existing Prevention Controls and 

Recovery Measures 

For each of the potential unwanted events listed as high above, 

the risk assessment team uses some risk analysis tool to identify 

existing prevention controls and recovery measures. In this study, 

the Bow-Tie Method (BTM) was used. The following are a 

summary of each mine’s key prevention controls and recovery 
measures used during pillar retreat mining. These controls and 

measures represent a potential partial list of Best Practices for other 

deep cover pillar retreat mining. 

Mine A’s Existing Prevention Controls and Recovery Measures 

The limited time available for the risk assessment exercise did 

not allow the team to completely address the issue of recovering 

from the priority unwanted events. However, two of the highest 

risk potential unwanted events were examined. Table 5 is presented 

to demonstrate what consequence and recovery measure might be 

associated with two priority unwanted events. The major point of 

this activity is to consider: 1) how the mining operation could react 

to a potential unwanted event while mining the barrier pillar, and 2) 

identify impediments to this reaction when the potential unwanted 

event is placed at different locations within the section. 

Table 3. Mine A’s completed PHA form showing the risk ranking of the 25 potential unwanted events. 

# Potential Unwanted Event L C R# RR 

1 Floor hooves and delays development mining 1 1 25 VL 

2 Floor hooves and compromises ventilation 1 1 25 VL 

3 Floor hooves catastrophically 2 3 17 L 

4 Floor hooves and blocks travel 1 3 20 L 

5 Rib instability injures miner 4 2 14 M 

6 Rock falls between bolts injuring miner 4 2 14 M 

7 Rock falls from above the roof bolt horizon covers continuous miner requiring recovery actions 2 5 7 H 

8 Large roof fall collapse traps miner 3.5 3 11 M 

9 Large roof fall outby the pillar line injuries miners 1 4 16 L 

10 Poor or delayed roof caving(i.e., cantilevered roof) and causes coal pillar failure 1 3 20 L 

11 Main roof doesn’t cave and causes coal pillar failure 3.5 3 11 M 

12 Windblast generated by large caving event injuries miners 1 3 20 L 

13 Barrier pillar fails injuring 1 1 25 VL 

14 Chain pillars in mains fail disrupting transportation throughout the mine 1 1 25 VL 

15 Development pillar fails at face injuring miner 2 4 12 M 

16 Development pillar fails several rows outby disrupting travel 3 4 8 H 

17 Water from overlying mine enters section and damages floor 5 1 15 M 

18 Water from overlying mine inundates section 1 2 23 VL 

19 Barrier pillar gob combines with adjacent longwall panel gob because of pillar collapse allowing 

gob gas into the face 1 1 25 VL 

20 Differential subsidence in the workings of the new overlying mine is caused by the current 

mining of the barrier pillar. 3 2 18 VL 

21 Damage to currently barrier pillar from overlying stress caused by multiple seam interactions 4 2 14 M 

22 Active subsidence occurs when overlying mining dynamically interacts with the mining of the 

barrier pillar 5 4.5 2 VH 

23 Miner injures back from handling heavy materials 3 2 18 L 

24 Continuous miners excavates rib bolts and strikes/injures miner 1 3 20 L 

25 Massive dynamic failure of barrier pillar 1 5 11 M 

L = Likelihood of Occurrence R = Risk number (based on L x C) 

C = Consequence of the Event RR = Risk Rank 

Mine B’s Existing Prevention Controls and Recovery Measures 

The limited time available for the risk assessment exercise did 

not allow the team to completely address the issue of recovering 

from the priority unwanted events. However, one of the highest 

risk potential unwanted events, roof falls, was examined. Table 6 

is presented to demonstrate what prevention controls and recovery 

measure might be associated with two priority unwanted events. 

Step 5 - Determine New Prevention Controls and Recovery 

Measures 

One of the most important outcomes of any risk assessment is 

the identification of potential new controls that might help to 

mitigate the risk associated with the recognized hazards. The two 

risk assessment teams at the study mines identified 14 new potential 

controls and 2 new recovery measures (Table 7). These new ideas 

were submitted to management in the form of an Action Plan. The 
Table 4. Mine B completed PHA form showing the risk ranking of the 12 potential unwanted events. 

# Potential Unwanted Event L C R# RR 

1 Rock falls on equipment requiring recovery 2 2 5 H 

2 Rock fall on equipment retrieval unit(wire rope damaged) 4 5 20 L 

3 Coal bump injures miner 4 2 8 M 

4 Rib fall injures miner 2 2 4 H 

5 Water inundation associated with a rock fall(water from upper seam) 4 5 20 L 

6 Miner injured while running during a pillar fall 3 4 12 M 

7 Material handling injury from lifting heavy equipment 4 4 16 L 

8 Large roof cave causes gas emission problem interrupting ventilation 3 5 15 M 

9 Large roof cave causes air blast injuring miners 2 4 8 M 

10 Weighting or pressure on pillars cause rock instability 2 4 8 M 

11 Roof support fails injuring miner 4 3 12 M 

12 Rock falls on miner 2 2 4 H 

L = Likelihood of Occurrence R = Risk number (based on L x C) 

C = Consequence of the Event RR = Risk Rank 

Table 5. Summary of Mine A’s existing potential controls and recovery measures. 

Dynamic Interaction Caused by Active 

Subsidence Roof Falls above the Roof Bolt Horizon 

Appropriate mine plan - The timing between Effective layouts - Pillars are not mined under the 

mining the Barrier Pillar and the overlying overlying old workings or when overburden is greater than 

mine are managed. 1,200-ft. 

Efficient monitoring - Numerous monitoring activities are 

Effective mine design - The plan to mine the used including test holes, strobe lights and gages on the 

r

Barrier Pillar requires the barrier, development 

and extraction pillars to be sized in accordance 

MRSs and Geologic Shift Reports. 

Safe pillar extraction process - Ground support near the t

with the recommended Stability Factor pillar line follows best practice with two sets of MRS Units 

evention Con ols 

determined from NIOSH’s Analysis of Retreat and intersection cable bolting systems. Several procedural 

Mining Pillar Stability, or ARMPS, method. controls are used to keep miners out of the areas with 

These factors are based on the assumption known hazards. Section workers are trained to monitor the 

Existing Pr

that the mine is not bump prone. The risk MRS and if a unit goes to yield, they are instructed to pull 

assessment team members were not aware of out and reset the unit. Pillar stumps are at least 10 by 10-ft 

any past bump incident at the mine. in dimension and are marked to maintain their minimum 

size. 

Stability while mining - In addition to 

the primary support system used during 

development mining, the Barrier Pillar has 2 

rows of 6 by 8-inch wood posts on 2 to 4-ft 

spacing to control minor levels of dynamic 

interaction. 

Successful audits - Workers are trained to be aware of the 

red and yellow zone markings. The mine’s Safety and 

Health Team audits the performance of section crew to 

make sure that safety and health policies and procedures 

are being adhered to. 

Recovery

Measures 

Two entries have standing supports (6 by 8 posts on 2 to 4-ft spacing) 

Anchors and other hardware for the Miner Retriever are on the section 

Nitrous oxide for first aid 

Transportation for quick evacuation 

Air bags on section for lifting / moving heavy material, i.e. broken rock, etc. 
 

 

 

ideas presented in Table 7 might also be of value for other deep 

cover retreat mining operations. 

Table 6. Summary of Mine B’s existing potential controls and recovery measures. 

Roof Falls on Miner 

e ols 

Supplemental support in the form of a star bolt pattern is installed in the recovery area 

Test holes are drilled at the beginning of each shift and at intervals not to exceed 40-ft thereafter 

Test holes are examined to gather additional information on rock characteristics 

Workers observe roof conditions 

Examinations of working places, i.e. by Foreman and continuous miner operator (20-min intervals) 

Measure entry widths to ensure they are approximately 19-ft 

Measure cut-widths and marked on the rib and roof 

Cuts are made at no more than 45-deg angles from headings and are no more than the width of the miner head. 

vention Contr

The continuous miner moves straight in and backs straight out 

Personnel placement is such that all workers are positioned outby, with the exception of the continuous miner 

operator, and those required to watch conditions. In particular, the MRS operator watches for continuous miner 

isting PrEx

operator at the outby intersection 

The continuous miner pump motor is turned off when setting timber or MRS to increase workers ability to hear 

rock noise 

MRSs are positioned to add stability to the area and pressures are monitored 

The continuous miners can reboot quickly (< 1.5-min) after shutdown assisting in quick relocation 

Recovery Measures 

Communication at the primary intake and feeder or power center are available for calling out to dispatcher 

If workers are injured, contact MSHA immediately, otherwise contact MSHA one hour after a roof fall 

Mine B has a SOP for “Clean-Up Procedures for Rock Falls” 

There is an EMT on most sections 

First response kits are available (O2

 bottles, blood pressure, airway, EMT equipment) 

Supervisors get 5-hr of extra first aid training 

Emergency stretcher on every section 

10-ton lifting Jack and bar on every section 

An equipment retrieval unit is located in the surface yard and can be deployed to the section quickly 

DISCUSSION: A DEEP COVER RETREAT MINING RISK 

MANAGEMENT PLAN
 

A significant advantage of the MHRA technique is the listing of 

the mine’s prevention controls and recovery measures. These lists 

represent a partial inventory of Best Practices for deep cover retreat 

mining. The MHRA exercise demonstrates the value of focusing an 

operation’s attention on specific hazards. It also helps to reinforce 

the existing prevention controls and recovery measures used by 

the mining operation and brain-storm new ideas that might help to 

lower the risk. 

A significant limitation of the MHRA technique centers on its 

inability to determine how well controls are actually applied. For 

example, the majority of the controls identified by the two risk 

assessment teams consist of procedures that rely on personnel skills 

and training. These kinds of controls often require administrative 

procedures and clear work processes. They have the potential 

for significant human error and can be only marginally effective 

in reducing risks. In these cases, regular audits and reviews are 

needed to provide assurances to mine management that the controls 

are being applied to some operational standard. 

Clearly, the MHRA exercise alone will not assure the risks are 

mitigated. It is recommended that all the actions defined by the 

MHRA process be incorporated into some kind of deep cover 

retreat mining Risk Management Plan (RMP). The RMP should be 

a component of the mine’s overall safety and health management 

system. It should represent a management process by which 

hazards are identified and risks are continually and systematically 

assessed, and either eliminated or controlled, from design through 

to abandonment of the mining section. In this example, the RMP 

would be solely focused on the deep cover retreat pillar risks. In 

practice, all RMP’s could be linked to the mines overall RMP for 

all known major hazards. 

A RMP would only be adequate if individuals who have roles 

relating to the outlined activities have the responsibility and 

authority to carry out these actions. It is also important to note that 

mine management has the overall responsibility, implementation, 

and coordination for the actions described above. As is the case 

with all safety and health management systems, communications 

of the plan to relevant parts of the workforce will help to ensure 

that all personnel with responsibilities under the plan are informed. 

This requires targeted, regularly scheduled, training. It also 

requires that the plan be monitored and some kind of audit process 

will be established. 
 

 

Table 7. New ideas lowering the risk associated with the priority unwanted events. 

Control Type New Ideas 

Reinforce MRS proper placement during cut(lift) extraction, i.e., move one MRS at a time 

Evaluate personnel placement issues to assure that only necessary personnel enter high risk areas 

on the pillar line 

Section Foreman watches the mining of the final cut from a remote location and sounds an air horn 

if unstable conditions are observed 

Measure intersection diagonals to make sure entry spans are within acceptable standards 

Locate dips in the coalbed, i.e., points of highs and lows 

Place geologic and rock damage information on maps, i.e., fractures, roof falls, rib damage, 

intersection spans, etc., and attempt to develop risk maps prior to mining 

Study the advantages of installing cable trays on continuous miners, allowing the continuous miner 

Prevention controls 

to be re-handed to optimize the position of the miner operator 

Integrate information collected from other areas into current pre-retreat/daily safety training, i.e., 

geologic map, etc. Make training more specific to the panel or section being mined. Post this 

information in the dinner hole 

Each roof bolter collects roof rock type information and engineer puts this information on a mine 

map 

Incorporate personnel placement during pillaring, i.e., where not to be (the ‘red-zone’ concept) into 

an SOP 

Consider clipping corners of outby pillars to facilitate taking lifts from the crosscut 

Formalize the orientation and placement of future mining to control subsidence damage in the future 

mining of the overlying mine 

Investigate using tell-tails for ground stability characterization, i.e., roof fall and squeeze warning 

Determine the length of time needed to minimize dynamic interaction from undermining 

Recovery measures Investigate air bags on section for lifting / moving heavy material, i.e., broken rock, etc. 

Check on MSHA requirements for notification when continuous miner is trapped in a pillar cut 

SUMMARY AND CONCLUSIONS 

This NIOSH sponsored study was undertaken to evaluate the 

use of the MHRA technique to develop potential improvements 

in the way pillar retreat mines plan and mine deep cover coal. 

The MHRA’s strength lies in its capacity to systematically 

evaluate complex mining processes and their associated hazards 

that present significant consequence to the operation. A list of 

potential unwanted events is developed and risk ranked. The 

mining operation’s most knowledgeable personnel then focus on 

identifying a list of all existing prevention controls and recovery 

measures associated with each high risk potential unwanted event. 

During this process new ideas are identified and presented to mine 

management in the form of an Action Plan that should be evaluated 

further. 

Several important facts were observed by the authors as a result 

of these two MHRA exercises. Mining operations benefit from 

activities that help them focus on potential unwanted events. Many 

low probability events, like the ones discussed in this study, rarely 

happen, but when they do, they can have significant consequences. 

Discussing all existing prevention controls and recovery measures 

helps to re-focus the operation, making sure that all the necessary 

systems are being applied to monitor and audit these most 

important actions. Because it is difficult to quantify the impact of 

actions in the reduction of risk, the most proactive RMP continually 

apply more robust prevention controls. They also apply additional 

measures that will help them quickly recovery from these events 

with little consequence to the mining operations and its miners. 

The MHRA process shows potential in helping to lessen risk 

associated with deep cover pillar retreat mining operations. 

DISCLAIMER 

This work was part of a larger NIOSH research project. NIOSH 

was responsible for: 1) facilitating the risk assessment process 

known as Major Hazard Risk Assessment (MHRA), 2) documenting 

the risk assessment process, and 3) providing mine management 

with a written draft summary of the risk assessment process. The 

findings and conclusions in this report have not been formally 

disseminated by the National Institute for Occupational Safety and 

Health or the University of Pittsburgh and should not be construed 

to represent agency determination or policy. 

REFERENCES 

Anon, (1997), “Risk Management Handbook for the Mining 

Industry: How to Conduct a Risk Assessment of Mine 

Operations and Equipment and How to Manage the Risk”, 

MDG 1010, May 1997, 95 p. 

Joy, J., (2004), “Occupational Safety Risk Management in 

Australian Mining,” Occupational Medicine; vol. 54, pp. 311– 

315. 
Joy, J., (2006), “Minerals Industry Risk Management Framework,” Iannacchione, A., F. Varley, and T. Brady, (2008), “The Application 

Minerals Industry Safety and Health Centre, University of of Major Hazard Risk Assessment (MHRA) to Eliminate 

Queensland, 83 p. Multiple Fatality Occurrences in the US Minerals Industry,” 

NIOSH Information Circular 9508, October 2008, 132 p.