Pike River coal mine re-entry to try to recover 29 dead miners: All you need to know

The entrance to the Pike River coal mine near Greymouth. Photo / Kurt Bayer

It's been more than eight years since 29 men died when an underground explosion ripped through the Pike River coal mine. Families have battled authorities ever since to try to bring back their loved ones. Tomorrow experts will chip off the concrete seal to the mine's entrance and start looking for remains and clues about what happened. Kurt Bayer explores some of the big questions about re-entry.

Why has it taken this long to go back into the mine?

For the last eight years, many of the families who lost loved ones in the disaster have pushed to get their men home. They've also wanted it to be treated as a crime scene, and any clues which may lead to a future prosecution, gathered and explored.

After the methane gas explosion, fears of further explosions prevented any search and rescue attempts. Toxic gas levels and safety concerns meant the first attempt back into the mine – four days after the initial explosion – came with a New Zealand Defence Force robot sent underground. It broke down just 550m in after reaching water. Four more robots would go in, with mixed results, including video footage on November 25, 2010 from 1600m into the mine which showed extensive damage from the second blast and ended hope of recovering the 29 trapped miners.

Former Prime Minister John Key had vowed to try to recover the men if there was a feasible and safe way of doing so. But after years of looking at it, Key's National Government, along with state-owned mining company Solid Energy which bought the mine in 2012, finally concluded that a manned re-entry could not be done safely and the decision was made to seal the mine permanently.

Anna Osborne, whose husband Milton died in the tragedy, and Sonya Rockhouse whose son Ben never came home, blocked the Pike River gates to block the sealing of the mine, and ultimately won. They've also battled all the way to New Zealand's highest court, the Supreme Court, to overturn the decision to drop charges against former mine boss Peter Whittall, who escaped prosecution under the Health and Safety in Employment Act by accepting to make a $3.41 million payment to families.

During the 2017 General Election, then Leader of the Opposition Jacinda Ardern pledged that, if elected, a Labour Government would back a manned re-entry. And after a safe re-entry option was established, the coalition Labour-NZ First-Greens Government established the Pike River Recovery Agency and took over the re-entry mission. Last November, Minister Responsible for Pike River Re-entry Andrew Little confirmed they would be going back in.

Pike River Mine family members Anna Osborne, left, and Sonya Rockhouse are emotional as Pike River Re-entry Minister Andrew Little announces he has approved re-entry of the mine. Photo / NZ Herald

Why is it safe now?

After exploring three different re-entry options last year the Government announced in November that it could be done. They decided on a "single entry" plan, which would see expert miners go back through the existing main entrance and into the mine's drift access tunnel in fresh air. The deal was they would only go 2300m in, to where the rockfall came down in the explosion. It's believed to be up to 50m long.

To make the drift safe, they've had to purge the potentially-dangerous methane gas out by pumping nitrogen in. Boreholes were drilled down through the mountainside to let the lighter methane escape. Just before the first team goes in, they'll start pumping fresh air into the tunnel. Once inside, they'll drag forced oxygen blowers with them, which will allow them to operate in 30-40m sections at a time.

Who is going back in?

The first team comprises three people, led by Pike River Recovery Agency chief operating officer Kevin "Dinghy" Pattinson, a fifth-generation West Coast miner. He'll be joined by two as-yet unnamed experienced, qualified miners and together their sole job is to do hazard assessments of each 30m-40m zone and to look for geotechnical and ventilation issues, along with any general mining hazards or roof faults. Police, who earlier this year confirmed that they won't send staff into the mine until it's been safely "fully recovered", have given the miners forensic training and as they move through the tunnel, they'll scan for anything that may be of forensic interest to investigators. It's being treated as a crime scene.

What happens if they find anything of interest, including bodies?

Once the first three-man team has combed a 30-40m section, they'll walk back out and debrief the rest of the re-entry team, including police. They'll document and hand over any items of potential exhibits. Any hazards, like Pike River survivor Russell Smith's abandoned loader 1570m into the drift, and four robots sent into the mine after the explosion will be carefully extracted, perhaps even dismantled and removed piece by piece.

If human remains or bodies are found, a forensic team capped at six people – a strategically-located "refuge chamber" in the drift can only accommodate that many - will follow. It'll include a statutory official – someone qualified in mining and who holds a certificate of competency – along with a mines safety expert and forensic team whose job will be to gather any evidence, take photographs and take exhibits.

Once they're out, and after another debrief, the first team of mining experts will go back in, advancing the forced air, water services, communications, and do the next section.

Memorial board to the 29 miners who died in the Pike River mine disaster in 2011. Photo / Kurt Bayer

Are they likely to recover the 29 bodies?

The last known location of the men placed them in the mine workings beyond the roof fall. The official line from the PRRA is that it is "less likely" that they will recover human remains. About 1600m of the drift has been examined using robots and camera footage, with 600m still unexplored. Pattinson rates the chances of recovering them as being "very slim" although, given it was shift change at the time of the explosion, with men going in and out, there is a possibility of human remains being in the drift. And at least they will have tried, and for the families, that's all they've ever asked.

"I know there's always going to be people who'll say, 'For God's sake just let them lie, they're dead, they're all miners'," ," says Anna Osborne. "Well actually, I take exception to that... That place killed my husband and robbed my children of their father. And they will not determine where my husband lies if we get the opportunity to go in and recover. That's how strongly I feel about that."

How long is it expected to take?

Weeks, even into months. While some days Pattinson says they'll clear 200m-300m in a day, there'll be other times when they'll be stuck in one spot for days, clearing hazards, shoring up the roof, or examining potential clues. It's also dependent on the notoriously fickle West Coast weather.

How much will it cost?

An initial budget of $23m has been extended to $36m. The PRRA says there are "still some significant unknowns", including the physical state and stability of the drift, along with prevailing weather conditions. They will continually review operating methods as they go, responding to the conditions and risks.

What happens next?

Depending on what they find, at the end of it all they will reseal the mine and hand the land over to the Department of Conservation. The families are hopeful of finding evidence that could be used in a prosecution against anyone found responsible for the tragedy. Police have not ruled out manslaughter charges. A Royal Commission of Inquiry concluded there had been "leadership, operational systems and cultural problems", and found that Pike River Coal knew that the mine's atmosphere was in the explosive range for a number of days leading up to the deadly incident.

Anna Osborne, chairwoman for the Pike River Family Reference Group, which has a mandate from 28 of the 29 families, believes someone needs to be held accountable. "We have had to fight every step of the way to get where we are today," she says. "They put a 30m concrete lid on our loved ones' coffins without it being explored. You simply cannot kill 29 men and walk away from it. That's appalling."

THE PIKE RIVER DISASTER – A TIMELINE

• November 19, 2010: Methane gas explodes in the mine at 3.45pm, trapping 29 men.

• November 24, 2010: A second, unsurvivable explosion hits at 2.37pm.

• November 29, 2010: A Royal Commission of Inquiry into the disaster is announced.

• December 13, 2010: Pike River Coal is placed into receivership.

• November 2011: The Department of Labour lays charges relating to health and safety failures against Pike River Coal, its former CEO Peter Whittall and VLI Drilling.

• July 2012: VLI Drilling pleads guilty in the Greymouth District Court to three health and safety charges.

• July 2012: Pike River Coal is sold to Solid Energy.

• November 5, 2012: The Royal Commission into the Pike River Mine Tragedy makes its report and recommendations public.

• February 2013: Experts meet to discuss body retrieval and decide it can be done.

• October 2013: The Defence Force completes phase one of the mine re-entry plan.

• December 2013: Whittall's charges dropped due to a lack of evidence against him; Pike River offers voluntary payment to families of the workers.

• February 2014: Second phase of work to re-enter mine tunnel begins.

• September 2014: Two families of mine victims apply for a judicial review of the decision to drop charges.

• November 2014: Solid Energy decides not to re-enter the mine due to safety reasons.

• November 2015: The mine site is dismantled as the Department of Conservation waits to resume ownership.

• November 2015: Environment Minister Nick Smith announces a new 45km Great Walk to be created near the mine as a memorial to the 29 lost workers.

• November 2017: The new Labour-led Government announces the establishment of the Pike River Recovery Agency to work on plans for a manned re-entry of the drift of the Pike River Mine.

• February 2018: Pike River Recovery Agency takes ownership of the mine.

• November 2018: Minister Responsible for Pike River Re-entry Andrew Little confirms Pike River Mine Drift re-entry plan to proceed.

• May 3, 2019: The first miners go back into the mine to try to recover the 29 men.