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| An example of the outcome of a
Cavity Auto-scanning Laser Survey (CALS) that will provide a
threedimensional ?wire-frame? image of any void encountered when
mining the Geita Hill ore body, and will enable mining to proceed
safely. |
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| Ian Wallace, Mining Engineer, Geita mine,
Tanzania. |
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| A ?tag board? system has been developed to
control access to the ?hill? and personnel without a Geita Hill Void
Awareness pass are not permitted to enter the hill area. |
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| Rejean Prevereault, Safety Manager at Morila
in Mali. |
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Case studies
East and West Africa |
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| 7.4 Mining Geita Hill – drawing on international
best practice |
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The most significant risk identified during the
planning of the open pit mining operation of the Geita Hill ore
reserve, which is scheduled to commence in February 2004, is the
existence of old underground workings within the pit shell.
Underground mining of this ore reserve started in the 1930s and
continued until the official closure of the original mine during the
late 1960s.
Says Ian Wallace, a mining engineer responsible for mining through
the old workings at Geita Hill, ?Records of these operations are
sometimes unreliable or inaccurate. More recently, the orebody has
been mined informally by local artisanal miners ? and there are no
records at all for these excavations. In many cases the extent of
these mined-out areas or voids exceeds 50,000 m3 ? and all
have a significant potential impact on the planned mining operations
and are a source of potential danger to personnel and equipment.?
In planning for mining under these circumstances, Geita employed the
best methods and people available for the job. Ian himself has
had extensive experience at Kalgoorlie Consolidated Gold Mines, at
the Super pit in Western Australia, where similar circumstances were
faced when large-scale open pit mining commenced.
?In an attempt to identify the extent and position of voids prior to
the commencement of mining, an underground survey of the historic
excavations within Geita Hill was commissioned. This survey is
making use of cavity monitoring survey (CMS) equipment, which is
among the latest technology in this field. The CMS consists of a
motorised laser rangefinder which is attached to a long, fibre glass
boom. The end of the boom with the rangefinder is then inserted into
the void. The rangefinder rotates around the end of the boom
measuring the inside dimensions and orientation of the void. The
data is transferred via a cable to a data logger where it is stored
for post processing.
?Once mining commences, the primary method used to identify
high-risk areas within the pit will be probe drilling. Typically a
probe hole will be drilled to a maximum down-hole depth of 25 metres
below the current working bench. Reverse circulation (RC) grade
control, exploration and blast hole drilling, which are undertaken
during the normal course of operation of the mine, will also assist
in defining the presence of underground excavations. Surface
subsidence or expression of voids will assist in identifying the
presence of underground workings before drilling of any sort
commences.?
Where underground workings are identified and the safe ground area
established, the area will be delineated using coloured flagging
tape on the current mining bench. A two-colour system will be used
to differentiate between areas with high and moderate levels of
risk. Entry into the demarcated areas will be strictly controlled.
?The volume of each void will be established making use of a cavity
autoscanning laser survey (CALS) device,? continues Ian. ?This is
deployed down a drill hole and the results of this survey provide a
three-dimensional image of the void. These images are then used to
establish safe ground conditions, rock-fill volumes and a true
orientation of the void. Once identified, a holing between the void
and the surface working will be established by developing a rise,
from the pit floor into the void. This rise will then be used as a
rock pass, through which waste rock will be tipped in an effort to
fill the void below." |
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| 7.5 Behaviour-based approach to safety at Morila
in Mali |
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The Morila gold mine in Mali, a joint venture
between AngloGold and Randgold Resources which is managed by
AngloGold, has since inception experienced a range of safety issues.
This was particularly the case as the mine was undergoing
construction and ramping up to full production, and when a large
number of the people on site were employed by contractor companies.
But, since the implementation of the new safety strategy in 2003,
the company?s safety performance has improved markedly. For example,
the Lost Time Injury Frequency Rate has decreased to 3.78 per
million man hours in 2003, from 6.27 in 2002.
To address the early disappointing safety performance, mine
management first undertook a survey of the safety climate and
culture at the mine. This survey indicated that: |
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Employees felt that while
the strategies, targets and goals were evident, they were
limited to senior employees; |
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Some managers showed
commitment some of the time; |
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Leaders did not involve
employees at all levels through empowerment, recognition and
consultation; |
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Although the safety plan
was defined, this existed in isolation and lacked support; and |
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The role of the individual
in the system was not adequately defined or communicated. |
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Says Rejean Prevereault, Safety Manager at Morila,
?One of the problems we have encountered is what we call a
fatalistic ?management is responsible for safety? attitude.
?Our new campaign started in 2003 with a total refocus on safety and
an increased personal and more visible involvement in the process by
mine management as well as the appointment of a dedicated Safety
Manager. We also increased our focus on safety awareness, audits and
training, and planned for increased involvement by the union safety
representatives, coupled with the cultural awareness programme.
Finally, with the help of external expertise, we started
implementing a behaviour-based safety (BBS) programme in September
2003.
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| Four-phase
programme |
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Phase 1 Mindset
survey, including interpretation and feedback; |
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Phase 2 Leader
behaviour alignment, which involves the steering team
and identification of champions, skills coaching and relationship
building; |
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Phase 3 Implementation
of self-directed motivation in the safety process; and
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Phase 4 Monitoring
and measuring progress (at the end of 2004). |
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| Looking forward,
Morila aims to improve still further. Supervisors and employees
will continue to be expected to lead by example, to improve
communication and understanding, to promote the development of
local safety personnel and to expand an awareness of safety into
the home. |
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?We believe that this programme will contribute substantially
towards increasing communication at all levels at Morila, and
further reducing accidents (by more than 50% in two years). By
changing the mindset in relation to safety, we hope to effectively
and efficiently focus, create synergies and align workforce energy
and commitment to optimise productive and safe behaviour and
responsibility. We involved a wide range of stakeholders, including
the general manager, heads of departments, line supervisors, safety
representatives, unions, employees, contractors, head office and
external experts.?
Important components here have been the introduction of the
?Brother?s keeper? campaign where employees are encouraged to stop
unsafe actions by fellow employees or stop work if they feel unsafe
and the positive involvement of people in AngloGold?s Zero Tolerance
approach. To implement the Zero Tolerance approach, employees are
first trained in respect of safety regulations; then the safety
rules are applied, with continuing education on why it is important
to apply this rule; third, employees who do not respect the rules
are disciplined.
?We have the full support of management, the safety representatives
and the unions for this approach.? |
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