We're waiting for more news about the “Plan C” drilling rig moved to the San Jose Mine in Chile. The rig, which is normally used for oil and gas work, is owned by Precision Drilling, based in Calgary. The big rig will chew a hole 35 inches wide and 2,300 feet deep. If the bit doesn't run into a major fault or get stuck in mine debris along the way, and if Plans A and B don't get there first, it could open an escape route well before December. At that point a man-cage would be lowered on a wire rope to pull the men up one at a time.
This may sound like a whopping big borehole, and it is, but there have been much bigger and deeper ones. A pioneer in the field was Fenix & Scisson, now part of PB Energy Storage.
Beginning in the early 1950s it excavated deep rock caverns for compressed gas storage, typically located near pipeline hubs and refineries. Fenix used a drill rig to make a vertical hole that was hundreds of feet deep but just wide enough for a man to wield a rock drill. While suspended in this chimney, a few dozen feet off the bottom, he drilled and blasted enough rock to clear out a small cavern, with the muck going into the bottom of the borehole. (Yes, he was hauled out of range each time a shot was fired ...) Once the cavern was roomy enough, Fenix lowered a small front-end loader in pieces. Workers reassembled it and went to work, hollowing out caverns as big as football stadiums.
Fenix bored a really big hole to prepare for the Atomic Energy Commission's Cannikin underground nuclear test on Amchitka Island in 1971. Fenix's hole (before the concrete liner) was a vertigo-inducing 90 inches across and 5,875 feet deep. At an approximate yield of 5 megatons, Cannikin was the biggest underground shot ever fired in the US. Here's a link to snips of ground-wave effects from an AEC video on YouTube.
So Rescue Plans A-C at the San Jose Mine are not pushing the margin in either size or depth.
But they are trying to move fast because 33 men have already been down there six weeks. As I mentioned in an earlier post, we know from other trapped-miner incidents that even over shorter periods, the men can suffer from erratic behavior and severe depression, and a few have attempted suicide. You may have read recent reports that some of the miners were still driving around in mine vehicles, despite orders. I'm trusting that the foreman Luis Urzúa, who seems quite capable, has put any explosives out of reach.