RISK ASSESSMENT FOR CONTINUOUS MINER-RELATED FATAL INCIDENTS IN US UNDERGROUND MINING

The paper presents the results of research aimed at developing a risk assessment pro-

cess that can be used to more thoroughly characterize risks associated with continuous

miner-related fatal incidents in U.S. underground mining. The assessment is based on

historical data obtained from Mine Safety and Health Administration (MSHA) investi-

gation reports, which includes 30 fatal incidents that occurred from 1995 through 2006.

The risk assessment process used in this research involves three basic steps: (i) identi-

fication of the risks; (ii) risk analysis; and (iii) risk evaluation. The Preliminary Hazard

Assessment (PHA) method is used in identifying and quantifying risks. Risk levels are

then developed using a pre-established risk matrix that ranks them according to proba-

bility and severity. The resulting assigned risk value can then be used to prioritize risk

control/mitigating strategies. A total of four hazards were identified. The hazard “Fa-

ilure of victim to respect equipment working area” was both the most severe and frequ-

ent and it fell into the category of “very high” risk. Therefore, the largest portion of the

available resources should be allocated to prevent and control this hazard.

1. Introduction

Continuous Miners (CMs) are excavating machines designed to extract a variety of mi-

nerals by underground mining. For example, in underground room and pillar mining

49

VLADISLAV KECOJEVICThe Pennsylvania State University, 154 Hosler Building, University Park, PA 16802-5000, USA,

ZAINALABIDIN MD NORThe Pennsylvania State University, University Park, PA 16802-5000, USA

DRAGAN KOMLJENOVICHydro-Québec; Montreal, Quebec, Canada

WILLIAM GROVESThe Pennsylvania State University, University Park, PA 16802-5000, USA.

R.LARRY GRAYSONThe Pennsylvania State University, University Park, PA 16802-5000, USA.

RISK ASSESSMENT FOR CONTINUOUS MINER-RELATEDFATAL INCIDENTS IN U.S. UNDERGROUND MINING

The International Journal of

Mineral Resources Engineering, Vol. 13, No.2 (2008) 49-60

© At›l›m University Press

methods, they are the primary machines for mineral recovery through driving entries,

cross-cuts and pillar recovery. Even in longwall mining, they are required for driving

entries and crosscuts. CMs are used for the recovery of several minerals such as coal,

salt and potash. A CM drives into the heading face (“sumps”) with its cutter head raised,

and then uses a shearing action to cut down (“shear”) the mineral being mined, which is

then transported to the outby end of the machine through an on-board chain conveyor.

Figure 1 shows an example of a continuous miner.

Fig. 1. Continuous miner machine (image courtesy of Joy Mining Machinery).

Historically, underground mining has been one of the most hazardous work envi-

ronments in many countries around the world. Although progress has been made - over

the last century the number of U.S. mining fatalities, fatality incidence rates, and injuri-

es have decreased - the number and severity of mining incidents and injuries remains

unacceptably high. According to MSHA records, for the time period from 1995 through

2006, there were a total of 914 mining fatalities.1 The highest number is attributed to the

general category of Equipment - a total of 516. The proportion of total mine fatalities att-

ributable to the Equipment category ranged from 39 percent in 1999 to 86 percent in

1997. In the same period, there were a total of 30 continuous miner-related fatalities –

the highest number of all underground mining equipment. These data clearly indicate the

need to develop effective intervention strategies to further reduce fatal incidents in the

U.S. mining industry.

Risk management is a well-known loss control methodology that has been applied

by many industries including chemical, oil and natural gas, nuclear, military, aviation,

environment and aerospace. These industries consider risk management as an integral

part of their daily business. A number of “generic” risk assessment and management

standards and guidelines are available.2-5 Several countries have started to develop risk

assessment approaches for mining. The U.K. guidance document describes procedures

for carrying out Risk Assessment at Surface Mining operations.6 The Minerals Council

of Australia was the initiator of a project seeking to improve risk assessment in the Aust-

ralian minerals industry. The University of Queensland, Minerals Industry Safety and

Health Centre (MISHC) produced a guideline which aims to provide advice on risk as-

sessment within the Australian mining industry.7 The Minerals Industry Cooperation Ini-

50

V. Kecojevic, Z. Md Nor, D. Komljenovic, W. Groves, R. L. Grayson

tiative (MICI) project at the University of Queensland, Australia, launched a new web-

site called MIRMgate to improve the way mining, minerals processing and quarrying in-

dustries access hazard related information using Internet technology.8,9 In South Africa

the mining industry has established a Hazard Identification and Risk Assessment Prog-

ram to identify and record significant risks.10 While the development of risk manage-

ment programs for other industries, or for mining operations in other countries provides

valuable reference information, experience has shown that a simple transfer of proces-

ses is not effective due to characteristics related to specific industries and local conditi-

ons. The best practices related to risk assessment and management are documented in

both national and international standards. These references may be either generic2-4 or

industry specific.11-13 All these standards stress the need for specifically tailoring the risk

assessment and management approach in accordance with characteristics related to spe-

cific industries and local conditions.

There have been many attempts to understand the fundamental causes of injury in-

cidents related to mining equipment.14-29 However, these studies do not systematically

identify, quantify and evaluate risks related to operating or being near continuous miner.

Therefore, the main objective of this research was to develop a risk assessment process,

which is a part of an overall risk management program, that can be used by industry pro-

fessionals and health- and safety- related governmental agencies to more thoroughly

characterize risks associated with continuous miner-related fatalities.

2. Methodology

This research study is based on historical fatality data for the period from 1995 through

2006. Data on continuous miner-related fatalities were obtained from the MSHA inves-

tigation reports, which are publicly accessible from the MSHA web site.1 Almost 300

pages of investigation reports were examined. A typical report is approximately ten-pa-

ges long and contains the age and work experience of the victim, a description of the in-

cident investigation, discussion, root cause analysis, and conclusions.

As noted previously, risk assessment is a part of an overall risk management pro-

cess (Figure 2). It is a formal method of defining the potential risk(s) and is used to ans-

wer the following questions: 1) What can go wrong - where and when can it go wrong?

2) How and why can it go wrong? 3) What is the likelihood that it would go wrong? and

4) What are the consequences? The ultimate goal is to examine the potential risks so

that they can be controlled. According to Brauer,30 Haimes,31 and various internationally

recognized standards,2-4 the risk assessment process involves three steps 1) risk identifi-

cation, 2) risk analysis, and 3) risk evaluation.

The Preliminary Hazard Analysis (PHA) method was selected for this study based

on the nature of the information available from MSHA investigation reports, and the abi-

lity of PHA to assist in preventing fatal incidents that occur in identical and repeatable

systems like mining. This method is usually applied early in the design stages. However,

it can be used at any time throughout the life of the mine as a tool in a continuous safety

improvement program.

51

Risk Assessment For Continuous Miner - Related Fatal Incidents In U.S. Under Ground Mining

Fig. 2. Stages of a holistic risk management process.4

According to Kates and Kasperson,32 risk is a hazard measurement, taking into con-

sideration its likelihood and consequences. In the current study, the first step consists of

identifying the situations that have the potential to cause a fatality i.e. identifying ha-

zards associated with operating or being near a continuous miner. Hazard is defined as

something with the potential to cause harm.2,4 Hazard is also known as “immediate ca-

use” or “symptom” in the Heinrich incident dominos sequence.33 The Committee on Un-

derground Coal Mine Safety defined hazard as an unsafe situation in mines. 34 This de-

finition was further developed by Ramani35 to include unsafe acts. In this study, hazard

is defined as the immediate cause of the fatality. MSHA defines immediate cause as a

causal factor that if eliminated, would have either prevented the incident or mitigated its

consequences. The Hazard Inventory Table containing all identified hazards was compi-

led and shown in Section 3 of this paper. This table can be updated each time a new ha-

zard is identified.

Risk analysis is the second stage of the risk assessment process. It may be perfor-

med quantitatively, semi-quantitatively or qualitatively. According to Joy,36 if the seve-

rity (consequence) of the loss can be measured objectively and the likelihood (probabi-

lity) of the event can be determined from the historical data, then a quantitative risk as-

sessment can be performed. If the severity and likelihood cannot be specified but can be

estimated based on judgment or opinion, then a qualitative or semi-quantitative risk as-

sessment can be performed. In this study, quantitative risk analysis was considered to be

appropriate. The risk (R) associated with a particular activity is judged by estimating

both the probability (Pr) and the severity (S), in relative terms such as “low”, “medium”,

“high”, or “very high”. This way of expressing the risk is adequate for many types of

evaluation, allowing a structured approach to be adopted in situations where more quan-

titative methods would be difficult to implement. In the context of this study, probabi-

lity is considered as the likelihood that the hazard will cause a fatality in a future year,

52


and is calculated as the number of years in the study period in which a fatality was att-

ributed to a given hazard divided by the total number of years. Severity was judged from

the total number of fatalities associated with the hazard in the twelve-year study period.

The proposed severity and probability classifications are shown in Tables 1 and 2, res-

pectively, while Table 3 shows the resulting Risk Assessment Matrix.

Table 1. Severity Classification

Severity Definition

High Associated with more than 12 fatalities in the examined years

Medium Associate with 6-12 fatalities in the examined years

Low Associated with less than 6 fatalities in the examined years

Table 2. Probability Classification

Probability Definition

Almost certain Fatal incident will occur with a probability of Pr = 1.00

Very likely Fatal incident will occur with a probability of 0.50 ≤ Pr < 1.00

Likely Fatal incident will occur with a probability of 0.16 ≤ Pr < 0.50

Possible Fatal incident will occur with a probability of Pr < 0.16

Table 3. Risk Assessment Matrix

Risk evaluation is the final step in the risk assessment process and focuses on the

decisions required to address the analyzed risks. Brauer30 suggested that this step con-

sists of two components: risk aversion and risk acceptance. Risk aversion involves esti-

mating how well risk can be reduced or avoided through various strategies such as be-

havioural principles and technological advances as recommended by Kecojevic and Ra-

domsky.22 Risk acceptance involves creating standards for deciding what risks are ac-

ceptable for miners, companies, or society. However, setting a standard is a complicated

task as an acceptable level of risk may differ for each group. In the underground coal mi-

ne Commission report it was proposed that the only acceptable levels were zero fataliti-

es and zero serious injuries.37 It is appropriate that those levels be applied for the mining

industry as a whole. However, the main objective of this research was to develop a risk

assessment process that can be used to more thoroughly characterize risks associated

with continuous miner-related fatalities, and therefore, no attempt was made to define

acceptable levels of risk.

The first step of risk evaluation is to assign the identified hazards to the Risk As-

sessment Matrix (Table 3). These hazards are used to quantify and rank risks which ha-

53


ve to be addressed and in what order to prioritize control efforts. Risks in the highest pri-

ority cells are located in the upper left part of the Table, while risks in the lowest priority

cells are in the lower right corner. At the end of the risk assessment process, risks are

ranked according to their probability and severity in a relative manner rather than in an

absolute form. This will help to avoid underestimating or overestimating risks involved

in this assessment. The resulting relative risk ranking is sufficient to prioritize resource

allocations and control strategies.

3. Results and Discussion

According to MSHA records, there were 30 fatal incidents attributed to the continuous

miner between 1995 and 2006.1 It was determined that one fatality report was already

included in the “shuttle car” subcategory and, therefore, it is excluded from the “conti-

nuous miner” subcategory. Figure 3 shows the distribution of continuous miner-related

fatalities for the study period. The highest number of fatalities (8) was recorded in 1997,

while no fatality was recorded in 1998, 2005 and 2006.

Fig. 3. Distribution of continuous miner related-fatalities between 1995 and 2006

A total of four hazards were identified in the Hazard Inventory Table (Table 4). Ca-

ses in which victims failed to remain at a safe location or at a safe distance away from

the machine, or were standing or walking between the coal rib and machine while it was

in motion, were classified as “Failure of victims to respect the equipment working area.”

This hazard contributed to more than one third of all fatalities. A significant number of

fatalities were related to a roof fall during coal extraction. The fatal incidents occurred

when victims placed themselves in a hazardous area described in the roof control plan

as “the red zone”, unsafe extraction methods were being used, and adequate roof exa-

minations were not conducted prior to mining. These fatalities were classified as “Fa-

ilure to identify adverse site/geological conditions”. This hazard contributed to 10 fata-

lities. These are the two most dangerous conditions, contributing to almost 80 percent

54


of the continuous miner related fatalities. Fatal incidents which occurred during the

machine repair, assembling or dismantling were classified as “Failure to follow adequ-

ate maintenance procedure”. Examining the investigation reports, it was found that, for

instance, the victim came in contact with the rotating cutter head of the continuous mi-

ner as a result of work being performed on the machine prior to ensuring that the mac-

hine was properly de-energized, or, the boom of the continuous-mining machine was

not blocked against motion before maintenance work was performed. Finally, the fatal

incidents occurred because of the failure of continuous machine to operate properly is

classified as “Failure of mechanical components”. Hazards such as “Failure to follow

adequate maintenance procedure” and “Failure of mechanical components” contributed

to four and three fatalities, respectively. A total of 22 fatal incidents or almost 75 per-

cent occurred during the tramming and the process of mining the coal. All fatal incidents

related to the continuous miner occurred in underground mining – 29 in coal mines and

one in a trona mine. Figure 4 shows an example of hazards related to “Failure of victim

to respect equipment working area” and “Failure to follow an adequate maintenance

procedure”.

Table 4. Hazard Inventory Table – Continuous Miner

Hazard Year Total

‘95 ‘96 ‘97 ‘98 ‘99 ‘00 ‘01 ‘02 ‘03 ‘04 ‘05 ‘06

1 Failure of victim to respect equipment working area 1 0 0 0 1 2 2 2 2 3 0 0 13

2 Failure to identify adverse site/geological conditions 0 0 7 0 0 0 0 3 0 0 0 0 10

3 Failure to follow adequate maintenance procedure 2 1 0 0 0 1 0 0 0 0 0 0 4

4 Failure of mechanical components 0 1 1 0 0 0 0 0 1 0 0 0 3

Total 3 2 8 0 1 3 2 5 3 3 0 0 30

Fig. 4. The hazards “Failure of victims to respect equipment working area” and

“Failure to follow adequate maintenance procedure” (source of drawings: MSHA1).

The identified hazards, probability and severity are shown in Table 5. It can be no-

ted that “Failure of victim to respect equipment working area” has both the highest pro-

bability (Pr = 0.58) and severity (S = 13) for the continuous miner. The hazard “Failure

to identify adverse site/geological conditions” was with the lowest probability in the

Risk Matrix (Pr = 0.17) – it occurred in two years over the study period. However, this

hazard contributed to a significant number of fatalities (S = 10).

55


Table 5. Probability and Severity related to Hazards Inventory Table – Continuous Miner

Hazards Probability Severity

1 Failure of victim to respect equipment working area 0.58 13

2 Failure to identify adverse site/geological conditions 0.17 10

3 Failure to follow adequate maintenance procedure 0.25 4

4 Failure of mechanical components 0.25 3

The completed Risk Assessment Matrix for the continuous miner is shown in Tab-

le 6. There is no hazard classified as “almost certain” in probability category. One ha-

zard is categorized as “very likely” and three as “likely”. There is also one hazard cate-

gorized as “high” in the severity category, one as “medium” and two as “low”. It can be

noted that the combination of probability and severity makes the hazard “Failure of vic-

tim to respect equipment working area” fall in the “very high” risk category, and the re-

maining three hazards are placed in the “medium” risk category.

Table 6. Risk Assessment Matrix Table for Continuous Miners

It can be noted that “Failure of victim to respect equipment working area” was the

hazard falling into the category of “very high” risk. The Risk Assessment Matrix indi-

cates that the highest priority should be given to control this hazard. Its existence is very

likely, and it can contribute to a high number of fatalities. There are three hazards pla-

ced in the “medium” risk category. Extra available resources can be allocated to avoid

or mitigate these three hazards. Although having a lower probability of occurrence, they

contribute to fatalities. Ignoring these hazards could also increase their probability of oc-

currence and severity in the future. Further, when seeking continuous improvement of

safety with limited resources, once appropriate control interventions are taken to prevent

the highest priority risks, then the focus will shift to the next highest priority.

Hazards identified in this study are a symptom of failures in the safety system in-

volving continuous miners in the U.S. mining operations. Generally, an incident resul-

ting in injury or fatality is multi-causal, hence it is imperative that all hazards associated

with operating or being near a piece of equipment be identified and understood. Howe-

ver, in a previous study by Levens38 it was noted that only the immediate circumstances

associated with an incident were listed in MSHA reports, and no discussion of the pre-

ceding events leading to the incidents was provided. Further, significant variability in the

format and level of detail provided in incident investigation reports for the period exa-

56


mined in this study was noted; therefore, only the most immediate contributors to a fa-

tality could be considered for analysis. This is a limitation of the data used in this study

which serves to emphasize the need for 1) additional research to better characterize the

“root cause” of the fatalities, and 2) a systematic and thorough approach to incident in-

vestigation.

4. Conclusions

Risk assessment is a recognized, useful and effective methodology to identify, quantify

and evaluate risks. In this study, risks of operating or being near the continuous miner

were examined.

The hazard “Failure of victim to respect equipment working area” was both the

most severe and frequent and it fell into the category of “very high” risk. Therefore, the

largest portion of the available resources should be allocated to prevent and control this

hazard. Additional resources can be allocated to avoid or mitigate hazards located in the

lower probability and severity cells of the Risk Matrix. Although having a lower proba-

bility of occurrence, they contribute to fatalities. Ignoring these hazards could also inc-

rease their frequency and severity in the future.

Since risk assessment is just a part of an entire risk management process, future re-

search efforts should also include risk control, and implementing and maintaining cont-

rol measures, in a proactive, preventive way. Risk management is most effective when

applied to injuries and near misses, which seek to avoid catastrophic outcome (fataliti-

es). Near misses are not reported to MSHA, but all injuries are, and thus should be a

high-priority focus for application of risk management methodology. Therefore, risk ma-

nagement of equipment-related injuries would be desirable research in the future.

Acknowledgement

This paper is a part of a detailed study on Risk Assessment of Equipment Related Fata-

lities in Mining sponsored by the Western U.S. Mining Safety and Health Training and

Translation Center. We gratefully acknowledge the financial contribution from this Cen-

ter.

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Documents

RISK ASSESSMENT FOR CONTINUOUS MINER-RELATED FATAL INCIDENTS IN US UNDERGROUND MINING