dcbass,
From what I have heard, the drilling from the Sinker to remove water from the other tunnels is "routine", if you can call it that. I'm not sure of the details, but as mentioned in the post, modern drilling methods are available that can handle high pressure. Not that I would want to be around when they break through, but then I'm not a miner. I think the historical records indicate the Sinker was only a couple hundred feet or so from the other tunnels when they gave up way back when. As far as draining water that is continually seeping into the tunnels, that is what the Sinker was designed to do. As indicated before, the Sinker is the key to reopening the mines. Once it is connected and expanded, then continual drainage is no longer an ongoing expensive problem (no pumping water up to the top of the mountain), and ore only has to be brought down to the sinker and then down the mountain (year round), not up to the top of the mountain and then all the way down (only part of the year).
I'm sure you wanted more detail (I'd like to see it myself, just out of curiousity), but hope this helps anyway.
spiny