The Tasmania Reef is a gold-bearing quartz-carbonate-sulphide vein, occupying an old fault structure that crosses a series of sedimentary beds. It is about 3.1 metres thick, and dips to the south at an average of 60 degrees. One of the largest towns on the reef is Beaconsfield. William Paterson was the first European to arrive in the area - in 1804 - but settlement of Beaconsfield itself, known variously as Cabbage Tree Hill or Brandy Creek, did not occur until the 1850s.
Gold was discovered in 1869, and mining began in 1877. Three shafts were sunk to access the reef: the Hart, Main and Grubb shafts.
Beaconsfield became the richest gold town in Tasmania. In 1881 there were 53 companies working the field. But as they delved deeper, water became a serious problem. The last gold mine closed in 1914 due to regular flooding of the shafts.
But technology changes things. During the 1970s, new surveys confirmed that the reef continued at least another 200 metres below the original mine site. Later work extended this to close to 1000 metres.
In 1999, the Beaconsfield Mine Joint Venture was formed and the mine was re-opened. The shareholders were the Allstate group (51.51 per cent) and Beaconsfield Gold (48.49 per cent).
The re-opening of the mine was premised on new pumping technology, which would keep the water at bay. Initial work centred on the rehabilitation and de-watering of one of the original shafts, the Hart Shaft, to the 375 metre level. The new operators installed a pumping station 180 metres below the surface, with a capacity of 800 litres per second.
The gold was a prize worth fighting for, but the cost of working the mine proved bigger than the incomings. An administrator was appointed to Allstate on 8 June 2001 and creditors - notably Macquarie Bank - approved a Deed of Company arrangement.
At that time, Macquarie Bank was owed about $32 million - only part of which was secured. The only way that the bank could win back its investment was to keep the mine open.
On Anzac Day 2006, it all went pearshaped.
At 2126 Australian Eastern Standard Time that day, a seismic event triggered a rockfall deep underground. Geoscience Australia says that the earthquake had a magnitude of 2.2 at a shallow depth, at co-ordinates 41.190° S and 146.840° E.
Some dozen miners were in the mine at the time. All but three emerged. Larry Knight, Todd Russell and Brant Webb were working in a machine called a teleloader. Knight was operating the vehicle. The other two were in a basket at the end of the teleloader's arm, where they had been applying steel mesh to the walls of the tunnel to prevent rockfalls.
The exact details of what happened next are now the subject of the Beaconsfield Mine Rockfall Investigation. Greg Melick SC has been appointed as Special Investigator. He is a former member of the National Crime Authority. Melick's report will be handed to the state coroner, and could form the basis of a criminal action if deemed appropriate.
Ahead of the report, the head surveyor at Beaconsfield, Simon Arthur, refused to comment on the record.
Working from what is currently on the public record, parts of the story seem clear enough. On 26 April, a remotecontrolled earthmover moved in and began clearing the rock. Knight's body was found in the operator's cab of the teleloader. There was no sign of Webb and Russell. The logical thing, of course, would have been to clear away the debris around the teleloader and try to get access to its arm. However, mining inspector Fred Sears had deemed it too dangerous to approach the rockfall area.
The mine at this depth is a honeycomb of tunnels. A new tunnel was blown out of the rock towards the presumed location of the end of the teleloader arm from an adjacent tunnel.
But several of the miners directed to blast the four metre by four metre tunnel were deeply uneasy about the operation. One of them, Gavin Cheesman, climbed over the jumbled scree of rocks that had landed on the teleloader. At 1745 on 30 April, he made contact with Webb and Russell.
According to some reports, Cheesman was able to get close enough to the basket of the teleloader to shake Russell's hand. Later, he returned with water, food, thermal blankets and fresh clothing.
The fact that the two men were alive did not change the fundamental position of the management. The route over the scree was dangerous. Moreover, it was reported that Webb and Russell themselves did not want the rescuers to attempt to reach them through the rubble. It would have meant cutting through the wire on the side of their cage, which was under extreme pressure from the rock above. They were afraid that cutting the cage would cause it to collapse.
On the other hand, the rescuers could no longer risk using explosives to break up the rock in the new tunnel. The shockwaves were putting Webb and Russell at risk.
A decision was made to approach the trapped miners from underneath. From the beginning, it was accepted that it would be a slow operation, but mine managers decided that this was preferable to rash speed.
A 90 mm pipe was drilled 16 metres sideways into the men's small prison from the head of the access tunnel, so they could be watered and fed. Webb and Russell directed the work by listening to the sound of the drilling and judging the direction. Through this pipe also came, in time, mp3 players and letters from home, but not rescue.
To get an impatient public off their backs, management told the army of journalists camped at the top of the shaft that, somehow, a microphone had been poked through the broken rock. The men had been discovered by thermal imaging, they told the media. In fact, thermal imaging equipment had been taken down the mine, but it could not be used. The temperature of the rock at that depth is similar to that of the human body, so the camera would not have picked up the flare of body heat.
Rescue teams came in from around Tasmania and NSW. A boxhole borer, a type of raise borer, emerged as the preferred solution.
A raise borer is a machine used for drilling a circular shaft between two levels of a mine. The borer is set up on the upper level. A small-diameter hole is bored down to the level below, using a conventional drill bit. The bit is only large enough to accommodate the drill string. Once the drill has broken into the open below, the small bit is removed and a reaming bit - of the required diameter of the shaft - is attached to the drill string and raised back towards the machine.
The advantage of this method is that any tailings from the operation fall away from the cutting surface due to gravity. This eliminates the necessity for large amounts of water or drilling mud to remove the tailings.
The boxhole borer is a variant of a raise borer. It is used when there is not enough space on the higher of the two levels to be connected. The boxhole borer is set up on the lower level. It drills a pilot hole as a guide, then drives the reamer bit along the pilot hole from the lower level to the upper.
The term 'raise' refers to a vertical or inclined opening which joins two levels of a mine.
At Beaconsfield, a boxhole borer was used on its side, to ensure minimal vibrations during the rescue.
Trucked in from another Tasmanian mine, the machine had to be taken apart and sent down the narrow shaft. It was then transported to the rescue tunnel and reassembled on a concrete base.
While the borer was being set up, surveyors and engineers mapped and remeasured the exact path that the machine should take, using the mine's Leica 1100 total stations.
The rescuers decided to angle the raise borer's path slightly downward to a point below the men. The borer was operated cautiously. It had a capacity of one metre an hour, but it was cutting through at around one third of that pace. All the while, engineers were anxiously watching nearby vibration monitors.
At the same time, the trapped men were put to work attempting to stabilise the rock around them. Tubes of super grout were sent down, and they spent hours pasting it onto the rocks.
On 1 May, drilling commenced on a 12 metre long, 20 cm diameter pilot hole. This process alone took more than three days. According to Beaconsfield mine manager, Matthew Gill, the quartz rock they drilled through was five times harder than concrete.
The drilling operation was completed on 6 May, with only a few metres remaining to reach the trapped miners.
It took several hours to dismantle and remove the boring machine from the tunnel.
On May 7, the rescuers reached a belt of hard rock that they found hard to penetrate. Their diamond-edged chainsaws were having little effect so they used low-impact charges.
The following day, the horizontal tunnel was completed. The rescuers began a short vertical tunnel. At about 0930, a probe passed through the rock below where the miners were located, which indicated there was only a metre between them, including 400 millimetres of hard rock.
After 14 nights, on 9 May, Glenn Burns, Donovan Lightfoot and Royce Gill finally broke through. At dawn, Todd Russell and Brant Webb walked out of the lift cage unaided '...punching their fists in the air to the cheers of the Beaconsfield crowds', according to one press report.
Both were then transported to the nearby Launceston General Hospital. Russell had an injured knee and a damaged vertebra, which put pressure on his sciatic nerve. Webb had injuries to both knees as well as his neck and back. They left behind the lawyers and accountants to pick over the mess, and possibly provide answers to some of the awkward questions prompted by the disaster.
Was it really caused by an earthquake, or did the earthquake merely precipitate a crisis that was waiting to happen? Was it really necessary to spend a fortnight drilling the escape hole? Did the lust for gold and profits outweigh commonsense and safety in the Beaconsfield mine? Some of those questions will be answered by the inquiry over the next few months, but not soon enough to save Larry Knight.
