Questions the Agency gets asked, with answers.
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 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.