I have a group of students who are interested in archaeology. I also live on a site with many sink holes from shaft mines for iron ore. Is there any precedent for excavating a sink hole safely? Any recommendations other than, "Don't do it!"?

Hi Frank,

Unfortunately (or fortunately?) no two sink holes are alike. A sink hole that appears as a 5 foot deep depression could actually be a 50, 100, even a 500+ foot deep shaft in disguise that is plugged with debris and then covered over by soil erosion. It could also be the result of a collapse of the underground roof of a 500+ deep stope very near the surface. Or, it could be a 5 foot deep test pit, which is rather uninspiring. There really is no blanket answer because all sink holes are unique. Earth movers have even been known to fall into sink holes.

However, you want your group of students to partake in this dire project... so really the issue for me is more about safety. I would strongly recommend against doing this for a few reasons (not least for liability reasons). First, there are potential fatal consequences if the earth opens up and your students or the earth mover slides into the hole while in operation. Secondly, you might need to foot the bill of stabilizing your newly rehabilitated 500+ deep mine shaft or "bottomless pit". And thirdly but not lastly, provided there are no casualties, you would need to justify the purpose of excavating the shaft in archeological terms. If you are trying to determine the shape or depth of the void, you can simply use a diamond drill rather than exposing the entirety of a shaft. But if you are trying to find any sort of archeological remains, you may come up empty handed other than the rotted remains of timbering or whatever was shoring or plugging up the hole.

All of this is not to say that shaft excavation has not or cannot be done. My point is you would really need to know what you're doing and such work would probably best be left to a company that specializes in mine reclamation or rehabilitation. If you have an adit tunnel on your property, that is a different story. But without knowing how vertically deep a sink hole might be or even why it is there, you are setting yourself for a risky proposition.

Frank, if you are in the NY, NJ, CT or PA area, we could perhaps take a look at your "sink holes" if you would wish to extend such invitation. With field analysis and historic research, we could possibly gain a picture of how the mine workings are laid out.

_________________
"If you thought old, abandoned mines were only in the west, then you haven't been to IronMiners.com!"

Wow! Thank you for your thoughts. The sink hole that I am talking about is a little more clear and a little less deep than you imagine.
In fact there are many of them to choose from. The closest one to where the mine shalt (which is blocked) enters is probably no more than 20 feet deep. It is about 10 feet in diameter and apparently 10 feet deep.
There is NO way that I would excavate this other than in absolute safety.
Why to do it? Frankly, I am not sure sure. Because it is there, I guess. My students could get into that impulse and would be way more reckless than I am.
The mines in question are in Pennsylvania. You can get very close to them on google earth at 151 Camp Ranch Lane, Bedford, PA 15522.
I would love to hear more from you.
Don't worry. I am not about to do anything hasty.

Frank

Also,
I would like to say that these mines are, I believe, of some historic significance. They date from no earlier than 1884, but were briefly fairly extensive, involving a narrow-gauge railroad and at least one inclined plane. There is virtually NO hardware left, but the footprint, of course, is still there and has been undisturbed.
Frank