Questions the Agency gets asked, with answers.

Update 12 March 2019

Background

Tragedy background:

  • At 3.44pm on Friday 19 November 2010 there was an underground explosion at the Pike River mine. Two men in the mine drift managed to escape. The 29 men deeper in the mine are believed to have died immediately, or shortly afterwards.
  • There were three more explosions within the mine before it was sealed nine days later. There is currently no access to the mine. The remains of the 29 men who lost their lives have not been recovered.
  • Families of the Pike River miners have been working for more than eight years now to find out what happened to their men, a journey that has been very difficult and for a long time completely unsupported and unrecognised.
  • The area of the drift (access tunnel) beyond the area known as “Pit Bottom in Stone” was driven in coal measures and the area of the roof fall was previously on fire. 

Agency set up:

Te Kāhui Whakamana Rua Tekau mā Iwa - Pike River Recovery Agency was established on 31 January 2018.   We are planning for a safe, manned re-entry and recovery of the drift access tunnel, to try and find out what happened in order to prevent any further tragedies of this nature and to promote accountability for this tragedy; to give the families closure; and where possible, retrieve any remains found in the drift.

Frequently asked questions:

How are you planning to re-enter the Pike River Mine drift?
Single entry – that is, a safe, manned re-entry of the approximately 2300 metre drift access tunnel in fresh air, via the current portal, with suitable safety controls in place. 

Who made that decision?
The Pike River Recovery Agency made a recommendation to the Minister Responsible for Pike River Re-entry Hon Andrew Little.  The Chief Operating Officer for the Agency (who is also the statutory Site Senior Executive and Mine Manager for the mine) and the Chief Executive of the Agency both certified that the recommended plan was technically feasible, could be achieved safely, and met the requirements of the Health and Safety at Work Act 2015, the Health and Safety at Work (Mining Operations and Quarrying Operations) Regulations 2016, and other relevant legislation. 
The Minister approved the plan for re-entry and recovery of the drift based on the recommended single entry approach.

How can anyone guarantee safety?
By assessing the risks, and implementing the controls required to mitigate or lessen the likelihood of those risks occurring, we believe it’s highly likely we can get to the stage where, on balance, it’s safe to re-enter the mine.  People work safely in underground coal mines around the world.  No-one wants anyone further to be injured or killed at Pike River.  Safety is paramount.

What about a second means of egress for the recovery?
One of the options we were considering included a new small tunnel to intersect with the main drift in the vicinity of Pit Bottom in Stone.  However the complexity and associated risk involved in its development outweighed any benefit.  This issue is discussed more fully in “Report – Pike River Mine Drift Re-entry and Recovery dated 31 Oct 18”.

Isn’t there a requirement for an underground mine to have a second means of egress? 
The Health and Safety at Work Act (Mining Operations and Quarrying Operations) Regulations 2016 require that by 2024 that will be mandatory.  While it would be good to have a second means of egress, it’s down to the level of risk that is acceptable.  The complexity and associated risk with the option to build a new small tunnel to provide a second means of egress outweighed any benefit. 

Breaching the seal:
How do you breach the seal – isn’t it covered in concrete?
As part of the original specification for the 30m seal, a set of man doors were built into the wall so the seal was “reversible”. The plan for breaching the seal is to use a concrete cutting specialist to cut through around 800mm of concrete around the perimeter of the man door until the man door is exposed. Another 1m x 1m hole will be cut out to allow for the ventilation ducting to pass through. Once this and all requirements under the ventilation plan are completed, manned re-entry can take place.

Ventilation Plans:
Why don’t you enter the mine with respiratory gear?
The mine drift atmosphere is currently around 98% nitrogen.  We could go in with breathing apparatus, but it carries a higher risk. We may need to use breathing apparatus to examine the area at the very end of the drift – that is yet to be determined.

Recovery where the nitrogen is replaced by air seems risky. You risk creating an explosive mixture.  Why not keep the nitrogen in the mine and enter with breathing apparatus? 
Recreating an explosive mixture: By using nitrogen we eliminate this risk. The mine atmosphere was previously around 96% methane.  The plan we are following vents the methane out by opening boreholes in the mine workings. While doing this we pump nitrogen in at the entrance behind the sealed wall. Once the methane has been replaced with nitrogen, which is an inert gas (non-explosive), we follow the same process taking the nitrogen out and bringing fresh air into the point within the drift that we require it. This way we don’t get an explosive mixture of methane and air.  The mine drift atmosphere is currently around 98% nitrogen. 
Breathing apparatus: We have previously considered using breathing apparatus. This however would create additional risk and potentially compromise the forensic examination. We may need to use breathing apparatus to examine the area at the very end of the drift – that is yet to be determined.

How is the nitrogen produced?
The Agency has hired a nitrogen producing plant, which filters nitrogen from fresh air, compressing it to be piped at about 98% pure nitrogen into the Pike River Mine. 

 

Photo of the nitrogen plant

The nitrogen producing plant at the Pike River Mine

 

Will the nitrogen displace methane in the mine workings area, as well as in the drift?
Methane will continue to be emitted at a rate of around 65 litres/second, and will vent through boreholes in the mine workings area, when displaced by nitrogen. When re-entry begins, the drift will be in fresh air, and nitrogen will be pumped through boreholes into the mine workings and through the roof fall, where the nitrogen will then be vented out of a borehole.

With a nitrogen rich atmosphere, does manned entry require personnel to wear self-contained breathing apparatus to enter the drift?
No. Our plan is to replace the nitrogen in the drift with fresh air up to a point just before the roof (rock) fall.  We may need to use breathing apparatus to examine the area at the very end of the drift – that is yet to be determined.

We’ve heard you’re going to flush out the methane, then pump the mine full of nitrogen to make it inert, before introducing fresh air.  What prevents methane from continuing to be produced in the mine?
The drift access tunnel is largely cut from stone, the mine workings are in coal which will continue to emit methane, and that’s why we will continue to pump nitrogen through the top of the mine where the mine workings are, and over the area where the roof fall occurred, to keep the mine atmosphere inert.  Methane will continue to be produced from the coal in the mine, but in small quantities that can be managed well with the nitrogen present from the roof fall up through the mine workings.

How are you going to investigate the area before the roof fall if it’s in nitrogen and you’re committed to entering in fresh air?  
If for any reason breathing apparatus is required to investigate the last few hundred metres between Pit Bottom in Stone and the roof fall, that will be considered.

Why can’t you put fresh air up to the roof fall? 
The roof fall occurred inbye the Hawera Fault (just before the mine workings) in an area of the drift that was built in coal measures (at the edge of the coal seam).  The fall has previously been on fire and consequently has the potential for spontaneous combustion.  Because fresh air and methane create a potentially explosive mixture, it is essential therefore that fresh air (oxygen) is kept away from the roof fall.  This will be achieved by a constant flow of nitrogen, introduced from the mine workings, over the roof fall, and vented through designated boreholes.  The roof fall itself will be constantly monitored for any signs of spontaneous combustion and the atmosphere monitored to ensure that it remains inert.

I want to understand in detail how you’re planning to ventilate the mine with fresh air? 
The two volumes of the Agency’s Ventilation and Gas Management Plan and Final Ventilation Report are on our website, search “ventilation” at www.pikeriverrecovery.govt.nz(external link).

What is a venturi?  What does it do?
A venturi is a piece of equipment (pictured) which works to extract gases from the borehole it is attached to.  Here’s the one the Agency procured, which was fabricated at Gray Brothers Engineering in Greymouth.

General:  

What preparatory work has been required to get to this stage?

  • Key milestones:
    • 30 April – 3 May                Initial Technical Expert Alliance workshop
    • 13 – 14 June                       Further detailed planning session (ventilation & geotech)
    • 8 – 9 August                      Detailed task analysis
    • 10 – 21 September           Risk assessment phase 1
    • 1 – 2 October                    Risk assessment phase 2
    • 16 October                        Final risk review phase 3 (decision)
    • 31 October                        Final report to Minister               
                                                  Cabinet paper prepared
    • 1 November                      Lodge cabinet paper
    • 7 or 12 November           Cabinet meeting
    • 14 November                   Minister decides on single entry option for re-entry
    • 19 November                   Pike River anniversary
    • 12 December                   Nitrogen purge commences
    • 7 January 2019                Drilling of 3 boreholes commence
    • February  2019                Nitrogen lines to boreholes complete
    •                                            Final detailed ventilation plan delivered
    •                                           Drilling of additional boreholes complete
    • March 2019                     Installation of remote emergency door complete

Now the Agency is finalising the Re-Entry Plan and supporting documentation which will soon be submitted to WorkSafe for review.

Other preparatory work includes:

  • Recruitment of mine workers; project officer; statutory appointment holders
  • Nitrogen Plant sourced, shipped and commissioned
  • Track upgrading
  • Nitrogen lines laid (9km through extremely rugged terrain)
  • Emergency management exercises
  • Mines Rescue training
  • Refurbishment of helicopter landing pads
  • Surveys of bridges and other key infrastructure
  • Tendering for helicopters, drilling and large mining equipment
  • Borehole camera video shoots (yet to be completed)
  • Upgrading compressor for venturi operations
  • Laying pipeline for compressed air to venturi (underway)
  • Introduction into service – all equipment to be used (yet to be completed)
  • Venturi designed, fabricated and yet to be installed
  • Upgrading gas sampling system – yet to be finalised

Why has it taken so long? 
The Agency has always said the project would be event-driven, not time-driven.  Through until November 2018 the focus of the Agency has been on ensuring the Mine is compliant; and developing plans and supporting documentation for approval by the Minister.  Since then focus has been on ensuring that elements supporting that plan including the regulatory requirements are fully developed.  This has included recruitment of additional staff, contractors and sourcing of critical equipment, while maintaining a legally compliant mine.  The critical path toward re-entry includes the sourcing arrival and induction of specialist equipment from Australia.

What equipment has been sourced from Australia? 
The Agency is leasing the following specialist equipment:  Two loaders with attachments (buckets/forks/jib/main basket/trailer), a driftrunner, a QDS drill rig, an Airtrack drill rig, and a refuge chamber.  All of this equipment is compliant for use in underground coal mines.

Why was it only available there? 
There is no compliant underground coal mining equipment available in New Zealand.

Will the Agency’s planning and safety assessments be subject to independent review? 
The Agency has had multiple experts working collectively on its plans and assessments, which have been independently reviewed along the way.  WorkSafe will also undertake an independent review of the Agency’s Re-entry Plan and Ventilation Plan.

Where is the rock or roof fall located in the mine drift? 
The roof fall is around 2300m in from the portal and believed to be up to 50m long.

Why don’t you use drones to re-enter the mine? 
We have considered the use of drones in the recovery plan. However to date we haven’t been able to find any drones that are certified as intrinsically safe for underground coal mining. 

Who’s on the team to go into the mine?  
We have yet to determine who will be in the re-entry teams.  The first priority is to make sure the mine drift is safe for re-entry. All people involved in the re-entry will be trained in working underground.

Are you planning for the next phase to re-enter the mine proper past the roof fall? 
Our remit is for a safe, manned re-entry of the drift access tunnel, to investigate the area to try and discover what happened, and to recover any remains found.  And afterwards, to rehabilitate the area.  Any decisions beyond that will be up to the Government.

How much will the re-entry and recovery cost? 
The current cost estimate for the project using the preferred approach is $36 million.  There are still some significant ‘unknowns’ such as the physical state and stability of the drift, prevailing weather conditions. Operating methods will be subject to continuous review in response to the conditions and risks that are actually encountered as work goes ahead.

Forensics:  
Are Police going underground – how will the forensics be carried out?
The Police role is to complete a forensic scene examination of as much of the drift as is safely possible, as well as any functions required on behalf of the Coroner. 
Police, the PRRA, WorkSafe NZ and their respective experts have agreed that the safest option for Police staff is for the drift to be fully recovered before Police consider deploying into the drift, rather than a staged approach.  
However Police will adopt an agile approach in the event of a critical find, such as the discovery of human remains.  This means that, in certain circumstances, Police will consider deploying staff into the drift before it is fully recovered.  Should this situation arise then Police will consult with the PRRA and independent experts to assess and understand the stability of the mine and the underground emergency management measures at that point.  Police will only deploy staff into the drift if we consider it safe to do so.

What are the chances you’ll recover bodies? 
The last known location of the men placed them in the mine workings beyond the roof fall, so it is less likely that we will recover human remains.  
Approximately 1600m of the drift has been examined using robots and camera footage, and about 600m is unexplored. Given it was shift change at the time of the explosion, with men going in and out, there is a possibility of remains being in the drift. 
As part of the detailed forensic examination, any human remains that are found will be treated and recovered with care and respect. 

In terms of recovering evidence, what pieces of equipment do you expect to bring out?
Whatever items are identified as being of interest, where we are able to bring them out.  If something is a particularly big and heavy piece of equipment, it might mean dismantling it and bringing parts out.

Can’t you just start up that equipment and drive it out?  Put new batteries in if needed.
Underground coal mine equipment runs on compressed air, no batteries are used underground.  It’s unlikely they would just restart after eight years of not being in use. 

In terms of other forensic clues, what else could be in there? 
We want to look at everything.  The New Zealand Police are developing the forensic search plan which includes all of the underground equipment, as well as any items of interest in the drift.

Following the recovery of forensic evidence to the roof fall, is it likely that information learned will inform any future direction as to entering the mine workings?
The mandate of the agency is to re-enter and recover the drift.  This includes the area of Pit Bottom in Stone and up to the roof (rock) fall.  Any future decision to re-enter the mine workings is a matter for the Government.

A glossary of mining terms from the Royal Commission on the Pike River Mine Tragedy is available on the Pike River Recovery Agency website.

Updated 301118

How are you planning to re-enter the Pike River Mine drift?
Single entry – that is, a safe, manned re-entry of the approximately 2300 metre drift access tunnel in fresh air, via the current portal, with suitable safety controls in place. 

Who made that decision?
The Pike River Recovery Agency made a recommendation to the Minister Responsible for Pike River Re-entry Hon Andrew Little.
The Chief Operating Officer for the Agency (who is also the statutory Site Senior Executive and Mine Manager for the mine) and the Chief Executive of the Agency both certified that the recommended plan was technically feasible, could be achieved safely, and met the requirements of the Health and Safety at Work Act 2015, the Health and Safety at Work (Mining Operations and Quarrying Operations) Regulations 2016, and other relevant legislation. 
The Minister approved the plan for re-entry and recovery of the drift based on the recommended single entry approach.

How can anyone guarantee safety?
By assessing the risks, and implementing the controls required to mitigate or lessen the likelihood of those risks occurring, we believe it’s highly likely we can get to the stage where, on balance, it’s safe to re-enter the mine.  People work safely in underground coal mines around the world.  No-one wants anyone further to be injured or killed at Pike River.  Safety is paramount.

What about a second means of egress for the recovery?
One of the options we were considering included a new small tunnel to intersect with the main drift in the vicinity of Pit Bottom in Stone.  However the complexity and associated risk involved in its development outweighed any benefit.  This issue is discussed more fully in “Report – Pike River Mine Drift Re-entry and Recovery dated 31 Oct 18”.

Isn’t there a requirement for an underground mine to have a second means of egress?
The Health and Safety at Work Act (Mining Operations and Quarrying Operations) Regulations 2016 require that by 2024 that will be mandatory.  While we would like to have a second means of egress, it’s down to the level of risk that is acceptable. 

Why don’t you enter the mine with respiratory gear/breathing apparatus?
The mine atmosphere is currently around 96% methane.  We could go in with breathing apparatus, but it carries a higher risk, and we would only be able to look around.  That is not completing our task to recover the drift and it would make efforts to try and find what happened very difficult.  For instance, we wouldn’t be able to bring out essential equipment that needs to be examined.

Recovery where the nitrogen is replaced by air seems risky. You risk creating an explosive mixture.  Why not keep the nitrogen in the mine and enter with breathing apparatus? 

  • Recreating an explosive mixture: By using nitrogen we eliminate this risk. The mine is currently around 96% methane.  The plan is to vent the methane out by opening the boreholes in the mine workings and at the far end of the tunnel. While doing this we pump nitrogen in at the entrance behind the sealed wall. Once the methane has been replaced with nitrogen, which is an inert gas (non-explosive), we follow the same process taking the nitrogen out and bringing fresh air into the point within the drift that we require it. This way we don’t get an explosive mixture of methane and air.
  • Breathing apparatus:  We have previously considered using breathing apparatus. This however would only allow limited reconnaissance rather than the detailed forensic examination of the drift and Pit Bottom In Stone which is a key objective of the operation. Also the risks associated with continuously working in breathing apparatus increase over time. 

Will the nitrogen displace methane in the mine workings area, as well as in the drift?  
Yes, nitrogen will displace methane in both the mine workings and the drift.

Following the recovery of forensic evidence at the site of the roof fall, is it likely that information learned will inform any future direction as to entering the mine workings?
The mandate of the agency is to re-enter and recover the drift.  This includes the area of Pit Bottom in Stone and up to the roof (rock) fall.  The forensics examination could inform any future decision to re-entering the mine workings - but that is a matter for the Government.

With a nitrogen rich atmosphere, does manned entry require personnel to wear self-contained breathing apparatus to enter the drift?
No. Our plan is to replace the nitrogen in the drift with fresh air up to a point just before the roof (rock) fall.  We may need to use breathing apparatus to examine the area at the very end of the drift – that is yet to be determined.

Where is the rock or roof fall located in the mine drift?
The roof fall is around 2300m in from the portal and believed to be up to 50m long.

Why don’t you use drones to re-enter the mine?
We have considered the use of drones in the recovery plan. However to date we haven’t been able to find any drones that are certified as intrinsically safe for underground coal mining or any that could operate in around 96% methane-enriched environment. 

Who’s on the team to go into the mine? 
We have yet to determine who will be in the re-entry teams.  First priority is to make sure the mine drift is safe for re-entry. All people involved in the re-entry will be trained in working underground.

Are you planning for the next phase to re-enter the mine proper past the roof fall?
Our remit is for a safe, manned re-entry of the drift access tunnel, to investigate the area to try and discover what happened, and to recover any remains found.  And afterwards, to rehabilitate the area.  Any decisions beyond that will be up to the Government. 

How much will the re-entry and recovery cost?
The current cost estimate for the project using the preferred approach is $36 million.
There are still some significant ‘unknowns’ such as the physical state and stability of the drift and prevailing weather conditions, and operating methods will be subject to continuous review in response to the conditions and risks that are actually encountered as work goes ahead.

We’ve heard you’re going to flush out the methane, then pump the mine full of nitrogen to make it inert, before introducing fresh air.  What prevents methane from continuing to be produced in the mine?
The drift access tunnel is largely cut from stone, the mine workings are in coal which will continue to emit methane, and that’s why we will continue to pump nitrogen through the top of the mine where the mine workings are, and over the area where the roof fall occurred, to keep the mine atmosphere inert.  Methane will continue to be produced from the coal in the mine, but in small quantities that can be managed well with the nitrogen present from the roof fall up through the mine workings.

How are you going to investigate the area before the roof fall if it’s in nitrogen and you’re committed to entering in fresh air?
If for any reason breathing apparatus is required to investigate the last few hundred metres between Pit Bottom in Stone and the roof fall, that will be considered.

Why can’t you put fresh air up to the roof fall?
That area of the drift has coal (the vast majority of the drift is built in stone), and has previously been on fire. Fresh air could reignite a fire because it can react with coal or any methane emitted from coal in the roof fall area. So we need to keep fresh air away, and maintain the atmosphere over the roof fall in nitrogen. 

Forensics:

  • Forensics Planning is well underway – led by NZ Police.
  • It is a crime scene, we have to treat it as such. 
  • We’ll be bringing out any equipment that needs to be analysed, where that is possible. 
  • We’ll be prepared for whatever we find, including human remains. 

Are Police going underground – how will the forensics be carried out?
Police have said they are committed to ensuring a thorough scene examination is completed, in line with scene examination protocols, when re-entry to the mine is achieved. 

When you say it’s a crime scene, what do you mean?
Twenty-nine men were killed in that mine.  Nobody has yet been able to determine definitively how and that happened.  We’re working on re-entering this mine so we can try and find some answers.

What are the chances you’ll recover bodies?
The last known location of the men placed them in the mine workings beyond the roof fall, so it is less likely that we will recover human remains.  
Approximately 1600m of the drift has been examined using robots and camera footage, and about 600m is unexplored. Given it was shift change at the time of the explosion, with men going in and out, there is a possibility of remains being in the drift.
As part of the detailed forensic examination, any human remains that are found will be treated and recovered with care and respect. 

In terms of recovering evidence, what pieces of equipment do you expect to bring out?
Whatever items are identified as being of interest, where we are able to bring them out.  If something is a particularly big and heavy piece of equipment, it might mean dismantling it and bringing parts out.

Can’t you just start up that equipment and drive it out?  Put new batteries in if needed.
Underground mine equipment all runs on compressed air, no batteries are used underground.  It’s unlikely they would just restart after eight years of not being in use.  Plus any machines will no longer be compliant, as that requires regular maintenance and testing, so legally, we are unable to run them.  We have to drag them out, where that is possible.

In terms of other forensic clues, what else could be in there?
We want to look at everything.  We know there’s been a continual water flow – we don’t know a lot about what’s in the last 400m, and won’t until we’re inside the drift.