Drilling a shaft: new entrance?

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I'm posting this question to gather information and feedback about the feasibility of having a new entrance shaft sunk into a cave. I know it's done because I've been down the Doyle Valley entrance at Mammoth. We're currently working in a cave that could benefit from such a shaft. How is it done? How wide? Is there anyone out there that can offer a starting place? I'm thinking drilling contractors (wells, etc.) are the people to do it. How to pay for it? Grants? Private contributions? Public organizations? Or is it just prohibitively expensive for small (read: dirt poor) survey groups?

Any thoughts on this?

CG

[Roppelcaver]

You ought to talk to Dave Weller on this one, who made the entrance to Roppel.

Doyle Valley was incredibly expensive requiring first an initial bore, then the large drill bit that made the 30in diameter hole.

For Roppel, Dave used a cheap drilling machine to make a series of two-inch holes. It might have been six -- one center and five around. He then blasted from the bottom up to create the initial hole that he worked into a large entrance.

The FIsher Ridgers made an entrance to, similar in approach I think.

In both cases of Roppel and Fisher Ridge, the project took over a year. I think it cost about $1500 out of pocket, and a whole lot of free labor.

At Webster, you might luck out with a vertical shaft (dome) close to the entrance, which might make it more feasible. In any event, make sure it is worthwhile for the long haul (do you really need that entrance, or can you just do a few hard trips), and be prepared to drop some dough unless you have a cheap and dependable labor pool. Of course, you need to radio survey the spot before you do any work. We relied on divine intervention (luck) once (Khan), but I would not recommend that as something to depend upon.

I can give you contact info -- just pm me.

[Scott McCrea]

You could check with the folks at the Carroll Cave Conservancy. They blasted a shaft in to the center of the cave.

John Ackerman (PDF) drilled/blasted a shaft into a mid-western cave (Coldwater?).

The folks at cavediggers.com probably know of others too.

Oh yeah, they blasted an entrance into Blue Spring Cave, TN recently.