The Atacama region in South America is a very large mining area producing great volumes of copper and gold, which together are the largest GDP providers in Chile. Labour comes from not only Chile but also the neighbouring countries. The miners are drawn to the higher paying locations which are also the most dangerous. These range from semi-illegal operations employing just a handful of people to the larger mines with 600-700 people.
Yet there are only three government mine inspectors in the country. Codelco is one of the largest employers that run very safe operations underground but unfortunately this culture does not occur in all other mine operations.
San Jose
The scene of the 2010 accident was the San Jose mine in norhern Chile. It started life in 1889 with the existing headgear over the access shaft having been in place since around 1910. The ropes for this do not go down the full depth of the mine, so were no good for the rescue from the deep levels. The access shaft was further laid to waste by the removal and sale of many of its ladders in a bid for extra revenue.
Mining at San Jose has mostly been continuous since it opened except for a short closure in 2009 due to a dispute between the miners and owners over the safety of the mine. It still made a profit of USD 20M in 2009. There had been eight deaths in twelve years with the last in 2007 but this made little impact on the safety of the mine. The mine is about 600km north of Santiago and 90km from the coast though being a mountainous region, the transport of equipment to the mine takes about five days from the coast.
Collapse
On the afternoon of 5 August, 2010, a section of the mine from 350m deep to 630m deep completely caved in. This was day 0 for 33 miners in the deepest levels of the mine. This collapses surpassed any mine collapse before it and shocked the international mining community.
The 8.5km long ramp used to access the mine face had completely failed. It is belived that overmining of the ramp structure itself led to the collapse.
In an effort to make the mine more productive, the operator had remined the ramps support structure for any gold or copper left in it.
Immediately following the collapse all communication was lost with the trapped miners and it was impossible to know if anyone had survived.
Rescue workers and the Chilean Government officials were quickly on the scene but with no maps of the mine at all it was difficult to start assessing the damage. The maps now available were drawn after the event. The extent of the collapse was also unknown initially though it was thought that engineers could re-mine the ramp through the collapsed section to reach the trapped personnel. This started but stopped soon after it was realised it was futile and possibly fatal to continue, with the collapsed ramp and access shafts providing further dangers to rescue teams.
Other attempts to access the lower levels also failed due to blocked accesses and ongoing collapses.
With remining ruled out, Codelco sent 18 rigs to bore pilot holes to attempt to locate the trapped miners. Without any plans of the mine it was down to the mine’s foreman to guide the boreholes. Standing at the mine entrance the foreman paced out his journey down the ramp in his mind and suggested rig positions. Drilling operations were fraught with difficulties as drill bits encountered hard ground and existing mine plant and equipment.
As drilling continued it became clear that the mine was completely choked from 350 to 505m depth and at this point many were considering giving up. From a consensus on conversations between the mine rescue teams, until the full mine depth had been reached, there was still a possibility of finding live people. The Chilean government also supported this approach.
Contact
Two days later on day 14 the drill had reached 670m depth and reached a void where the drill was pulled back so a CCTV camera could be lowered down. Upon pulling the drill out, the rescuers were shocked to see on the end of the drill bit a poly-pocket with a note inside explaining that all 33 miners were alive at a refuge chamber.
It was decided to continue drilling with three rigs as a contingency in case any of the drill holes collapsed. The first hole was used as a supply route for water, food, messages and medical equipment.
On day 17, a camera was put down that allowed the first view of the miners. Obviously no medical staff could reach the miners but proper food and supplies could be delivered. Experts from NASA advised that no solid food was to be delivered initially. Only high energy drinks and liquids to rehydrate the miners, much to their consternation, though NASA also supplied a rolled up TV screen with DVDS for the miners to watch. The supply hole allowed charged light to be sent down which would last for 24 hours and was continually resupplied. Later on, ventilation was supplied with cool air along with cables for video conferencing.
The miners’ only lighting had been their cap lamps which ran out early on. A Toyota SUV was then used with its engine running to keep the headlights running. Once that had run out, water from the radiator was used for drinking water. Cannibalism had also been discussed.
Equipment and personnel from around the world were used to aid in the rescue attempt but once a large bore had reached the miners the other two rigs were shut down before they reached their full depth. Drill bits from Belfast were supplied.
Raise boring technology was used to enlarge the hole but the problem here was that normally you would have the large reamer in a single piece underground. For the rescue the reamer had to be lowered down and re-assembled. The 33 miners were engaged in removing excavated material. The foreman arranged three shifts and it proved to be a huge morale booster.
Extraction
On day 66, Phoenix Two, the rescue capsule was able to be tested and lowered down. The hole also passed through two roadways so it had to be a set length so it did not deviate off the required angle.Communications were maintained throughout the extraction process.
Two paramedics were sent down to check the miners over before they were allowed out.
On day 67 the miners were all successfully rescued with no major injuries.
Some of the miners did suffer from medical problems after the rescue including dental problems due to the acidic water, with some requiring surgery due its effects. Silicosis problems were also present though some miners had this already.
The cost of the rescue operation has not been finalised yet but estimated at between USD 10M and USD 20M. There were up to 800 people on the surface helping with the rescue attempt.
The assets of the mine were seized by the government five days after the mine rescue operation to help pay for the costs with the rest provided by Codelco and the Chilean government.
Future planning
In planning for future events, the supplies the miners had to rely on were looked at. Before the miners were reached, they only had the food with them and emergency food for two days.
The foreman had begun a rationing process with two spoonfuls of tuna, one biscuit, and a little milk every 48 hours until the supplies were exhausted on day 16. The miners experienced an average weight loss of eight kilograms each.
The UK did put together a contingency plan of heavy mining equipment which was ready to be flown out if necessary.
Lesson could be considered for major tunnelling projects such as Crossrail. With a full face TBM and lining behind, the chance of a similar incident occurring is very low, however a flooding event in South Wales in September 2011 led to the deaths of several miners.
If boreholes were to be sunk for rescue attempts in a major city, the existing infrastructure may well preclude large areas from being used for drilling attempts. For mining operations a register of personnel and equipment has been assembled if a similar rescue attempt is required.
