Report: APP CMHS Project 4




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2.4.3. Risk Management

There is some use made of the Job Safety Analysis process of identifying hazards and implementing risk controls.

A risk management protocol is being applied to mines and consists of a simple methodology:

  • identify the hazard

  • rank the risk using probability x consequence x frequency, and based on some established nominal values

  • develop a safety management action plan to manage the risks

  • develop monitoring and review parameters

  • conduct a periodic review.

Case Example

There is a high risk rating of accidents due to inundation in Indian mines due to several factors; such as presence of old water logged workings, Inaccurate mine survey plan, improper survey instruments, inundation from surface, collapse of pillars due to fires, old galleries not shown on plan and breaching of flood protection dams. Hence a model Safety Management plan for inundation is to be developed. The steps involved in preparation of the Safety Management Plan (SMP) for Inundation are:

Step 1: Identification of the mechanism in which the inundation can occur.

Step 2: Calculate the risk rating as per the model suggested in Table 10. The calculated risk rating is shown in Table 12.

Step 3: Review of the existing control to reduce the risk and identify the new controls.

Step 4: Device the procedures for implementing the controls

Step 5: Identification of the responsibilities for the control procedures.

Table 12 Risk rating for inundation (DGMS)

Mechanism

Conseq.

Exposure

Probab.

Risk

Pillar failure due to fire allows connection with surface water body

5

10

7

350

Failure of river bank during heavy rain

5

10

7

350

Failure of drift dam 10 to 11 Seam

5

10

7

350

Surface flooding or water body enters through goaf or mine entries

5

5

7

175

Barriers against flooded old workings failing under hydrostatic pressure

5

10

3

150

Accidental holing into old flooded workings

5

5

2

50

Failure of river bank due to damage from mine subsidence

5

10

1

50

Pillar failure or creep allows goaf formation to connect with water body/aquifer

5

10

0.5

25

Roof fall in development workings taps overlying aquifer or water accumulation

5

1.5

2

15

Workings intersect geological structure providing water flow channel

1

2

1

2

Workings intersect open boreholes

0.1

2

7

1.4

Goaf development/cracking to surface due to mining

0.1

2

2

0.4

Workings intersect aquifer

0.1

1.5

0.5

0.075



In the exercise, Steps 3, 4 and 5 are done for the three highest risk rated inundation hazards i.e.

  • Pillar failure due to the fire and connection of underground workings with the flooded rivulet flowing in the surface

  • Failure of river bank due to the heavy rain

  • Failure of the water dam or seam parting in underground connecting the workings with water logged areas.

The details of the existing controls and the possible new controls for each of the above risks due to inundation of water are shown in Table 13.

The next step after identifying the new controls for reducing the risk of the hazard happening is to prepare the action plan defining the action/procedure for implementing the controls and assigning time frames and responsibilities.

Table 13 Controls for inundation (DGMS)

High risk hazard

Current controls

Possible new controls

Pillar failure due to fire and inundation from surface river (Risk rating: 350 out of maximum 500)

Borehole filling with concrete of roadways around pillar beneath river.

Install subsidence monitoring stations around area

No more mining under river

Define extent of fire and effect of remedial work by monitoring temperature and goaf gas.

Daily inspection of surface area for subsidence effects

Construct culvert drain over river bed

Filling cracks in river bed with grout

River diversion to new course unaffected by underlying workings

Monitoring and recording of u/g water levels

Re-line original river bed with concrete and re-divert river to original course

Pumping to maintain required water levels

Formal development of Emergency Evacuation Plan

Water Danger Plan with warning level specified as standing order

Provision of emergency dewatering pump system

Standing order for emergency mine evacuation (with water level trigger)

Training of workforce in inundation management plan

Failure of river bank due to heavy rain
(Risk rating: 350 out of maximum 500)

Inspection by Manager

Increase bank to comply with statutory specs (3mabove HFL)

Top of bank constructed 1.5m above HFL

Engineering appraisal to test strength and identify critical sections of bank

Some sections reinforced with concrete wall

Increase concrete reinforcement

Maintenance of bank to maintain dimensions

Widen the bank and reinforce key areas

24 hour watch during monsoon period

Desilting of river bed at upstream side

Additional lighting for observation at key sites

Training of workforce in inundation management plan

Overflow provision with old river course during heavy rain

Flood flow alarms

Inflow of water from underground workings
(Risk rating: 350 out of maximum 500)

Water Danger Plan 10 Seam with warning level specified

Evaluate possible sites to construct back-up or alternative dams

Monitoring and recording of water levels in all the Seams

Barrier pillars to protect dam marked on plans for mining in lower seams

Standing order for emergency mine evacuation (with water level trigger

Formal development of Emergency Evacuation Plan

Review Water Danger Plans

Provision of emergency dewatering pump system

Simulated evacuation exercises




This procedure also meets the basic requirements prescribed in the ILO code for hazard identification and risk assessment.


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