Thursday, November 25, 2010

Pike River Coal Mine - What Went Wrong?

The tragic events of the last seven days, culminating in yesterday's horrifying explosion at the Pike River mine and the loss of twenty nine very much loved men, will stand as a black day in New Zealand's history for many years to come.

We'd like to pass on our deepest condolences to the families of all the New Zealand, British, Australian and South African miners.

We hope that the recovery of the men can be done as soon as possible so as to lessen their families anguish, and to give dignity to those who perished working in one of the most dangerous occupations in the world.

Now also begins the examination of what may have gone wrong, what lessons can be learned to prevent this from happening again? No more families should have to suffer like this.

Andrew Watson, Operations manager of Mines Rescue safety training service in the UK,  wrote a report for the BBC examining what may have gone wrong in the Pike River coal mine disaster.
He started out by explaining the obvious differences between the Chilean and New Zealand mines.
Then went on to say that with coal mining there was additional natural hazards from combustible, toxic gases and weakened strata around the coal that needed to be supported.

But all of those "should be able to be controlled by high standards, regulation and good management."

So what may have gone wrong?

In his opinion the level of methane in the mine  reached dangerous levels above which miners should have been evacuated - suggesting that " either the warning system was inadequate or it wasn't properly monitored."

This is an interesting comment because various news reports said that no- one above ground had realised that the initial explosion had occurred until two hours after it had happened, and that was only because the two survivors, Daniel Rockhouse and Russell Smith, who walked out, raised the alarm. That  two hour delay cut into a four hour window of opportunity that a mine rescue team may have used to go in and try to bring the remaining men out.

According to Mr Watson the ventilation shaft should have ensured that methane did not build up to dangerous levels. So why did it?

He wrote:
After explosion
Methane gas is explosive in atmospheric ratios between 5% and 15%. In coal mines in the UK, we aim for less than 1% methane. At 1.25%, the power automatically cuts off, and at 2%, all miners are evacuated.
At Pike River, the fact that there was an explosion suggests the methane reached 5% or more. So, either the warning system was inadequate, or it was not sufficiently monitored.
Once the initial explosion occurred, the following would have been lost:
* Communication
* Monitoring of the mine atmosphere
* Ventilation
In such cases, it means that rescuers don't have much information to work with.
In the case of Pike River, what they would have done immediately is gone to the return ventilation side of the mine and taken samples.
That would have told them how much methane, carbon monoxide and hydrogen was in the atmosphere at that point. What it would not have told them was what the conditions deep inside the mine were - which parts were safe and which weren't.
The explosion might have damaged ventilation equipment such as fans, ventilation doors and seals. It might also have caused rock falls.
The miners would have been trained in these situations to travel towards a safe haven. If this couldn't be reached, the hope is that they would have barricaded themselves in somewhere away from this toxic and noxious environment.
Rescue decision
At this point, the rescuers would have had to decide whether it was safe enough to deploy a rescue team into the mine to gain the information they desperately needed.
This did not happen at Pike River, so clearly the information obtained from the return side samples indicated that it was too dangerous to enter the mine.
Some people have accused rescuers of being too cautious, questioning whether a window of opportunity had been missed. They insist that emergency teams should have been sent into the Pike River mine soon after the initial explosion.
The team would have had access to breathing apparatus - what we call long duration sets. These weigh 17kg (37lb) and last up to four hours. But when you consider the distance that rescue team would have to travel, it is clear that the apparatus would have been right on the limit. It was almost 1,200m (3,940ft) to the first cross cut, and 2,300m (7,545ft) to the end of the tunnel.Double that distance - to get in and back out - and you are taking things to the extreme.
Now consider the conditions in the tunnel. It would be very, very hot - because the ventilation may well have gone. And, because of the rock fall, the terrain would be rough.
Too dangerous
This could have been challenging even for a fit team of rescuers.
So, instead of going into the mine to get this information, they drilled a borehole from the surface, which obviously took time. Once completed, it verified that the atmosphere inside the mine was too dangerous too enter and that the worst scenario for the miners had been realised.
From a rescuer's point of view, this is as frustrating and distressing as it can be. These men would have been trained to help and rescue their colleagues. It is in the nature of miners to work as a team and to help each other in this extreme environment, and that is what the rescuers would have wanted to do.
There is absolutely no doubt that, if it had been possible for them to enter the mine at any time, they would have done so.
These men would have been aware that the environmental readings were preventing this.
No doubt, in the days and weeks to come there will be much discussion about what lessons can be learned from this disaster.
Of fundamental importance is the need to maintain high standards. Mining safety standards in New Zealand are very similar to those in the UK.
But, at Pike River, something went badly wrong leaving many questions unanswered.
Background to Pike River Mine
On 12 March 2004, Minister of Conservation Chris Carter approved the access arrangement for Pike River Coal Ltd. The arrangement included four 1.5m-wide emergency escape shafts within the boundaries of Paparoa National Park and a requirement for Pike River Coal Ltd to spend $NZ70,000 annually on conservation projects.

Carter stated that the "safeguards and compensation" outweighed the inconsistencies with objectives of the Conservation Act 1987 and the relevant management plans.

Due to the location, the conditions of the access arrangement required special consideration for the environment, such as a need to minimise tree felling and a requirement to reinstate all above-ground areas after mining ceases.

Opponents of the mine strongly criticised the approval of the access agreement, noting that the coal is not intended for domestic use but simply a commercial operation, and thus should not have been allowed to go forward in a sensitive location.

Forest & Bird also criticised the fact that the Minister of Conservation chose to ignore the report from the Department of Conservation stating that the mine would be damaging to the local environment. Greenpeace Aotearoa New Zealand also criticised the project for furthering the use of fossil fuels instead of developing sustainable alternatives.

Mine operation
"The coal is mined 200m underground, at 800m above sea level, quarrying coal from the Brunner coal seam. The coal is taken from the mine via a 'drift', a gently-sloping 5 degree tunnel 2.3 km long. This tunnel has taken large amounts of dynamite to create, as the rock is described as being up to four times harder than concrete...

Another major feature of the underground works is a 110m-deep ventilation shaft. After local ground conditions were found to be worse than expected, it was excavated with a raise-bore system excavating the 4.25m ventilation shaft from a 0.35m pilot drill shaft.  Access to the top of the ventilation shaft is by helicopter only, even during construction, as conservation restrictions do not allow roads to be built to reach this point.

The mine will also include underground excavation for the coal slurry handling facility and mine water storage and pumping equipment, with several large galleries of up to 5.5m width and 11m height to be excavated. As of 2010, The mine has three main "drives" (shafts).

Originally, once at the processing plant, coal was to be trucked to Greymouth for reshipment...
The mine was to have about 150 full-time staff, though in 2007-2008, there were problems filling all positions, partly because of high demand for the same occupations on the Australian and international job markets." (source wikipedia)

For more posts about Pike River Mine click here

Today's posts - click here


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