Questions the Agency gets asked, with answers.
Update 14 November 2019
- 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. The mine drift was re-entered on Tuesday 21 May 2019. The remains of the 29 men who lost their lives have not been recovered.
- Families of the Pike River miners have been working for nearly nine 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.
Agency set up:
Te Kāhui Whakamana Rua Tekau mā Iwa - Pike River Recovery Agency was established on 31 January 2018, to plan 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:
Have you re-entered the Pike River Mine drift?
On Tuesday 21 May 2019 a re-entry team comprising Chief Operating Officer Dinghy Pattinson, Mine Deputy Kirk Neilson, and geotechnical engineer Chris Lee opened the airlock doors at the 30m wall and stepped through back into the mine drift.
How will you carry out the recovery?
Single entry – our manned re-entry of the approximately 2300 metre drift access tunnel will be carried out 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 safe to re-enter and recover 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 Mine. Safety is paramount.
What about a second means of egress for the recovery?
One of the options we were considering last year 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:
What does breaching the seal mean?
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”. A concrete cutting specialist drilled holes through around 800mm of concrete around the perimeter of the man door and fed a wire concrete cutting string through the holes to cut 2m x 1m block sections out of the seal until the man doors were exposed. Another 1m x 1m hole was cut out to allow for the ventilation ducting to pass through. Once this and all requirements under the ventilation plan were completed, manned re-entry took place.
What happened after the opening of the airlock doors 30m into the drift?
Fresh air ventilation was established up to the existing 170 metre wall and the door there closed. A fully engineered barrier was established at 170 metres. Re-entry teams working in fresh air have cleared away the rest of the infrastructure up to that point (weirs, barriers, gabion baskets etc) to enable full access by mining equipment. At the same time, plans for going beyond the 170 metre barrier have been finalised with assistance from our international experts. WorkSafe, the regulator, will provide input and feedback to the Agency before the removal of the 170m barrier. After that, the teams will be moving carefully and deliberately up the drift observing actual conditions, pausing and replanning as required, and identifying anything of potential forensic interest.
Why don’t you use respiratory gear?
The mine drift atmosphere beyond the 170m barrier 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 / drift and enter with breathing apparatus?
Recreating an explosive mixture: Nitrogen is an inert gas. By using nitrogen pressure in combination with a remotely placed (Rocsil) ventilation plug to separate the mine workings from the drift we eliminate the risk of explosive mixtures. Since the explosion, the mine had been stable with an atmosphere of around 96% methane. The gas management plan we are executing purges the methane from the drift and the mine workings, by venting through upper level boreholes (methane being lighter than air/nitrogen). The residual methane originating from the workings (approx. 30 l/sec) is managed in the same way. We will follow the same process when we introduce fresh air into the drift as far as the Rocsil plug. 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 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.
Will the nitrogen displace methane in the mine workings area, as well as in the drift?
Methane continues to be emitted at a rate of around 20 litres/second, and is being vented through boreholes in the mine workings, as it is displaced by nitrogen. Nitrogen is being pumped into both the mine workings and the drift via a combination of boreholes and a pipeline through the 170m barrier. The reason the nitrogen and methane mixture is vented through the boreholes is to prevent an unwanted pressure build up.
We’ve heard you have flushed out the methane, then pumped 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 in the drift and mine workings area.
How will you control the atmosphere in the mine drift when you remove the 170m barrier?
Our Final Gas Management and Ventilation Plan (2019) provides for a number of ventilation control devices. The first, a Rocsil “plug” remotely inserted using boreholes close to the roof fall was completed in early November; at least one additional ventilation control device (VCD), (possibly more) will be constructed as the drift is recovered. One will be set up just inbye pit bottom in stone – this seal will provide a stable atmosphere for an extensive investigation of the hundreds of metres of tunnel and mining infrastructure housed in the pit bottom in stone area.
How will you control the atmosphere in those last few hundred metres before the roof fall?
The Agency has installed a Rocsil “plug” remote ventilation control device just outbye (portal / entrance side) the roof fall. This entailed pumping an expanding foam substance down an adjacent borehole. The foam has hardened up and forms a barrier which (assisted by a venturi) will allow fresh air to be circulated right up to the plug. The inbye side of the plug will be held at a higher pressure with nitrogen to ensure that fresh air will not leak through the plug to the roof fall.
Won’t the remote ventilation control device/foam plug cover up forensic evidence? How much space will it cover?
The “Rocsil” plug (Rocsil is a brand name) covers the width of the drift (about five metres), from floor to roof and a distance of between 10 and 15 metres from one end to the other, so between five and seven metres either side of where the borehole sits in the drift. Using a camera lowered down a borehole, we have photographed as much of the area as is possible before the foam is pumped in, and Police experts have indicated they are unable to see any items of interest in the area where the foam sits. As the Rocsil plug is removed it will be examined by the Police forensics team for any items of evidential interest. Safety of our underground team remains our paramount principle, and the use of the foam barrier is a key safety measure in our Gas Management and Ventilation Plan.
Is the plug able to be removed?
Yes. Our intent when we reach that point is to remove the plug and recover the remaining drift to the roof fall. The detail for this final phase of the recovery has not yet been finalised and will be dependent on gas management and conditions ‘as found’, particularly geotechnical.
Who was involved in installing the remote ventilation control device/foam plug?
The contractor and materials came from Australia – Wilson’s Mining Services. For the installation, we also used EcoDrilling; Mainland Pipeline Inspections for camera work; and Garden City Helicopters. As well as our own mining staff.
How much did the foam plug work cost? Approximately $1 million all up.
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 Ventilation Report are on our website, search “ventilation” at www.pikeriverrecovery.govt.nz(external link). A further and final plan will be posted on our website after it has been authorised.
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.
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 went into the mine first?
The first re-entry on Tuesday 21 May 2019 was led by Agency Chief Operating Officer / Site Senior Executive Dinghy Pattinson, with Mine Deputy Kirk Neilson and geotechnical engineer Chris (Rick) Lee. All people involved in recovering the drift are trained in working underground.
How far have the families been underground?
On Thursday 3 October, 26 family members of the Pike 29 chose to go underground by driftrunner up to the 170m barrier. Some family had previously gone underground as far as the 30m barrier.
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. Our role is also 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.
How long will all this take?
Based on our current understanding we anticipate the recovery operations to be completed by June and the rehabilitation and close down of the Agency by the end of September 2020.
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 they consider it safe for their staff.
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 unlikely 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 that human remains could be found 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, we will. 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.
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.