Dodged a bullet - found a sinkhole

[tractchores]

Here's some info.
The Science of Sinkholes | Science Features

I had a hole open up in my yard but when I dug it up with my backhoe is was pretty small. I figured it was probably an old buried tree stump.

Thanks!

 

[tractchores]

I'll have to check, but i don't believe there is much limestone in this area, mostly granite. I have a friend who is a geologist so will see what he says. There are no utilitities in the area, so it wouldn't be froma burst pipe (nearest road is over .5 mi away and my well is downhill from the spot a good distance away.

It's been very wet here, so water is most likely the cause. The big question is where is it going that its taking soil with it. The weird part is i was fine driving on this area just 6 months ago so it either developed or grew a lot. I may try to pump it out and excavate when its drier to see what is going on. There is a building about 50' away so i don't want it to spread.

Someone said it could be a spring, anyone ever heard of that causing a big hole?

 

[tractchores]

.

Sometime ground water pumping will "empty" an underground void that is supported by the water. When the incompressable water is not there, the roof of the void collapses and the soil and rock above it will fall verticially.

Maybe useful

Interesting, any idea how you would find something like that out? Could a well do it, or would it have to be more substantial like gas or oil exploration? I don't think there are anything but residential wells within a few miles, there is a drinking reservoir and 2 other lakes within .5 miles, so lots of surface water.

 

[PRF]

Could it have been a burial ground for stumps?

 

[jerrybob]

We had a small sinkhole caused by an underground spring. Hole was about 4x6 and 4 ft. deep. Spring went dry a few years ago.....don't know why. Filled the hole from another project.....seems fine for now.

 

[tractchores]

I don't think there was anything burried, but who knows? The area does have good sized trees around it, so if something was burried it would have been small.

The spring description may make sense given that this has always been a wet area. I do think something changed as the water appeared to be on the surface before and is now underground and the surface is very dry. It used to be a bowl that held water almost year round.

 

[MarkV]

Won't help your problem but you might consider a temporary fence to keep any animals or people from accidently disappearing. Your local ag extension agent may well have some ideas or experience from other locations in the county. It is unlikely you have the only one around.

MarkV

 

[Don87]

I don't think there was anything burried, but who knows? The area does have good sized trees around it, so if something was burried it would have been small.

The spring description may make sense given that this has always been a wet area. I do think something changed as the water appeared to be on the surface before and is now underground and the surface is very dry. It used to be a bowl that held water almost year round.

You've answered your own question.:thumbsup:

Underground springs make their own way(water seeks it's own path). Something as simple as a rotted tree root can divert the path of an underground spring.
The drying of the wet area was a 'foretelling sign', but unless you've experienced or studied it, you wouldn't know.
If you know anyone who can 'witch', they can tell you where the water is going, or you could do it yourself if you look up water witching. I can do it with a clothes hanger, some can do it with tree branches.

Witching works basically by electrical current, so not only can water be detected, but underground electric, and phone lines can be traced in the same manner.

 

[tractchores]

I did some poking around in the area today, though didn't get a chance to excavate (I had to move a big pile of dirt first). The water in the hole was crystal clear (so maybe a spring?), feeling the bottom with a stick there's rocks in the bottom, some areas are gravel and some are much deeper and mud on the bottom. It extends about 4' in one direction and there are some areas around that are 5' deep mud (can push a stick in 5 foot with minor effort). I think it's been developing for a while now that I look at it. Last fall I cut a tree (you can see the stump in the pictures) because the roots had just pulled out and it was lifting out of the ground with the wind, other trees around had started to die and I lost a couple of others. The whole area is slightly sunken vs the other ground and there's a thick mat of tree roots, which is what's holding the surface up, where I fell through I stepped between the roots. I've roped the area off with flagging tape and will wait for it to dry before digging in further. The stone wall near it is my property line, so I probably will be unable to drain it - but maybe I can fill it with rocks and get a stable surface, my hope was to use the area to park a trailer.

The area of the sinkhole. The hole in the center is where my foot went through.


Another view showing where the area is. Note there's a compacted Pad for parking right next to it. The drain pipe is for my downspouts though due to a gutter problem (tree hit it), almost nothing drains out of it, it runs out the other end.


where my foot went through, looks innocent enough!


Inside the hole. The water is pretty clear and the level is about 6" under the level of the ground, the top level is being supported mostly by tree roots.

 

[Birdhunter1]

I was wondering about that, but haven't found anything that looks like man made sides. I can't imagine why one would be in that location though.

Search the area with a good metal detector and see if you come up with a pile of square shank nails. My cousin and I knew there was an old house on the farm in the early-mid 1800's and we knew the approximate area within a hundred feet or so but we differed on where it was. My dad had said he used to plow the field and once in a while he would break a shear bolt in the plow from one of the old foundation rocks. He plowed it last spring and I picked up several decent size rocks to throw in a flower bed as ornaments. My cousin showed up later in the day and by use of his metal detectors we found the house (several square shank nails) and the occasional broken bolt from where a shear bolt in a plow had broken and the broken pieces were left in the dirt). After a few hours we had mapped out the perimeter of the house and in a few feet of digging found the foundation.