All 33 Miners Rescued, 2010 Copiapó Mining Accident, Chile

Percussion drills (rotary hammer drills) were used to make 6 boreholes about 5.5 inches (15 centimeters) wide to find the miners. The rescue effort was complicated by out--date maps and several boreholes drifting f-target because notoriously hard rock that exacerbated the drill's tendency to drift. On 19 August, one the probes reached the area where the miners were believed to be trapped but found no signs life.
Discovery
On 22 August at 07:15 CLT, another probe reached a ramp, at 688 meters (2,257 ft) underground, about 20 metres from a shelter where the miners were expected to have taken refuge. The miners had listened to the drills approaching for days and had prepared pre-written notes to their rescuers on the surface as well as making sure they had adhesive tape to secure the prepared notes to the drill once its tip poked into their space. The notes surprised the rescuers when they pulled the drill bit out and discovered the letters, the miners having survived longer than anyone had expected. At 15:17 CLT, President Sebastián Piñera showed the media the note after it had been placed in a document protector, sent from the miners' shelter far below, written on a piece paper with a red marker, that confirmed the miners were alive. The note read: "Estamos bien en el refugio los 33" (English: "We are well in the shelter, the 33 us").