Questions the Agency gets asked, with answers.
Update 14 May 2020
What is happening with the Pike River Recovery?
Miners recommenced working underground at Pike River Mine on Thursday 14 May, following the COVID-19 lockdown and the country moving to alert level 2.
The mine has been in a ‘care and maintenance cycle’ during COVID-19 Level 4 and 3.
During this time the Pike River Recovery Agency has developed and risk-assessed plans and other documentation required for breaching the Rocsil plug near the end of the drift. We’ve also had a team rostered to maintain the mine site and carry out the statutory functions over that time, in accordance with the mining regulations, and mindful of keeping our team safe.
Under level 3, the mine site, drift access tunnel and specialist equipment were prepared for recommencing operations underground, including all the required safety measures to prevent possible spread of COVID-19.
What was the Agency doing during the Level 4 lockdown?
The Agency was operating according to its business continuity plan:
- Ongoing government department reporting; health and safety steering committee meeting and management team meetings
- Providing regular updates to the Family Reference Group and wider families; daily COVID 19 updates to staff and contractors via email and on a dedicated Agency web page; along with weekly wellbeing checks
- Daily remote monitoring of the mine – (gas monitoring, strata monitoring and electrical supplies onsite), weekly scheduled site inspections and scheduled site maintenance
- Reviews of PHMPs, PCPs and draft of the risk assessment on breaching the plug
- Plans developed for how the mine would operate under Level 3 and Level 2 Covid-19 alert levels
Before the lockdown:
Our team were carrying out a detailed forensic scene examination of each recovered section of the drift. As they proceed, some items which are not essential for the investigation will continue to be removed to allow vehicle access. The teams underground work closely with New Zealand Police on site to discuss the removal and processing of any potential evidence.
After more than nine years with no maintenance, there are several sections in the mine drift which require new bolting of the roof, and that task takes some time in each section. As each section is recovered, air, water, communications, gas monitoring and ventilation is installed to the recovery point. A refuge chamber is moved to be reachable as the team progresses.
Why did Cabinet give you an extra $15 million?
A number of factors have put extra pressure on the Agency’s ability to complete the mandated recovery of the 2.3km drift access tunnel. They include: The ongoing need to attract and retain key staff with a range of specialist skills; the ongoing time and costs to ensure the mine is compliant with regulations; the time (more than 29,000 hours) and costs (including engaging leading international expertise) to develop all the required planning and safety management processes and documentation; the cost, availability and reliability of specialised mining equipment (in short supply and high demand and no longer available in New Zealand); prevailing weather conditions which impinge on the significant amount of helicopter work required; the dynamic atmospheric conditions underground where no maintenance has been carried out for the more than nine years the mine drift has been inaccessible; confirmation of the extent of forensic work underground being carried out by mining staff rather than NZ Police; geotechnical requirements underground.
When did you step through the 170m barrier, and who did it?
A team went in on Tuesday 17 December 2019. They checked for any hazards, inspected the state of the tunnel’s roof and walls, and had a brief forensic scan. Included were: Chief Operating Officer Dinghy Pattinson, Acting Underviewer Kirk Neilson, Mine Deputy Bryan Heslip, and Geotechnical Engineer Chris (Rick) Lee.
How do you control the atmosphere in the mine drift without the 170m barrier?
Our Ventilation and Gas Management Plan (2019)(external link) 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; with two confirmed ventilation control devices (VCD), (possibly more) – one inbye Pit Bottom in Stone and the second just outbye the Rocsil plug. 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.
I want to understand in detail how you’re planning to ventilate the mine with fresh air?
The Agency’s Ventilation and Gas Management Plan is on our website, search “ventilation” at www.pikeriverrecovery.govt.nz. It was part of the Exemption Documents submitted to WorkSafe on September 13 2019.
What were the documents submitted to WorkSafe on Friday 13 September?
The documents related to re-entering the Pike River Mine drift. As part of the application, these documents below were accompanied by Appendix 4: Timelines (redacted in its entirety under Section 9 (2) (a) of the Official Information Act 1982, to protect the privacy of natural persons); and Appendix 5: Police Plan (this document is currently not available).
- Ventilation and Gas Management Plan
- Entry and Exit Execution Plan
- Pike River Mine Drift Re-entry Geotechnical Assessment
- Force vs Exhaust Ventilation Risk Assessment
- Mine Entry and Exit Risk Assessment
- (external link) Pit Bottom in Stone ventilation arrangements
- Plan for rated machine doors
- Plan drawings for rated machine doors
- Rehabilitation, closure and handover report
Why did you need an exemption notice?
As previously announced, the plan includes an exemption for one aspect of mining regulations which has now been approved by WorkSafe under existing law. The Agency was required to demonstrate its plan was as safe or safer than the regulation.
Regulation 170 (4) (a) of the Mining Operations and Quarrying Regulations 2016 requires that there must always be an ability for workers to escape from a mine in an intake airway. The Agency sought an exemption to use a process called ‘forced ventilation’ in which fresh air is forced by a fan to the working space through a duct and then the air flows back (called return air) through the roadway to the entrance of the mine.
WorkSafe undertook a detailed review of the Agency’s exemption request and determined that worker health and safety outcomes were at least equivalent to the outcome of adhering to the regulation itself. WorkSafe was satisfied that the PRRA request met all legislative requirements for the granting of an exemption.
Agency Principal Staff Officer Karl Maddaford hugs Anna Osborne.
When did you first re-enter 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.
What’s the method of 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 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 30m 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 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 were finalised with assistance from our international experts. WorkSafe, the regulator, provided input and feedback to the Agency about its plans and has accepted they are safe. After fresh air trials, a team stepped through the 170m barrier on 17 December 2019. The barrier was removed early in 2020. After that, the teams are moving carefully and deliberately up the drift observing actual conditions, pausing and replanning as required, and identifying anything of potential forensic interest.
I want to understand in detail how you ventilate the mine with fresh air?
The two volumes of the Agency’s Ventilation and Gas Management Plan(external link) is on our website, www.pikeriverrecovery.govt.nz(external link) .
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 now we have introduced 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.
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 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. The reason the nitrogen and methane mixture is vented through the boreholes is to prevent an unwanted pressure and methane build-up. Nitrogen is being pumped into the mine workings and the chamber between the roof fall at the end of the 2.3km drift and the nearby Rocsil Plug. The drift now contains fresh air up to the Rocsil Plug.
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.
Underground images of the Rocsil plug in place in the drift.
How do you control the atmosphere in the mine drift after removing the 170m barrier?
Our Ventilation and Gas Management 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 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?
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 Ventilation and Gas Management Plan .
Is the plug able to be removed?
Our intent when we reach that point is to remove the plug and recover the remaining drift to the roof fall. The detail and plan 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.
How much did the foam plug work cost? Approximately $1 million.
The venturi at Gray Brothers in Greymouth.
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 in the mine drift?
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.
The 30m door is re-opened on 21 May 2019
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 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. The Government decided (Cabinet decision published 17 March 2020) there will be no work beyond the roof fall into the mine workings proper.
How much will the re-entry and recovery cost?
The current best estimate for the project using the preferred approach is $51 million. There are still some ‘unknowns’ that may affect the final actual cost of the project.
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 has developed a 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.
Will images of the drift and items found in it be made available to the media and public?
All images of the Pike River Mine drift taken during the recovery are potentially relevant to the ongoing criminal investigation. The same applies to any items of interest found within the drift. For this reason, as a general rule, Police will not be authorising the public release of this imagery.
Is this approach unique to the recovery of the Pike River Mine drift?
No. Police do not routinely release images of crime scenes to the media and public during the course of an active criminal investigation. Police are adopting the same approach here.
Who can authorise the release of images that are taken during the recovery of the drift?
Only the senior Police member in charge of the criminal investigation can authorise the release of any images taken during the recovery of the drift.
A glossary of mining terms from the Royal Commission on the Pike River Mine Tragedy is available on the Pike River Recovery Agency website.