I had an area of spongie grass, did some hand digging and found a air cavity underneith. Got out a shovel and dug it up. THere was indeed a cavity, somewhat deep going maybe 3 ft down at an angle and varing crossesction from 1 ft to 6 in.
What could cause it?
Moles?
It sounds more like the warren of a larger animal, either rats, rabbits, or groundhogs.
It sounds like an area being undermined by water, like a sinkhole.
Wait. . . 1 foot to 6 inches? It isn’t groundhogs, and probably not rabbits.
Possibly there was some wood or other organic debris, e.g., an old tree stump, that got covered up and rotted away. Around here, the builders dig huge holes, dump a lot of debris in, cover it and move on. Completely illegal but the county refuses to prosecute anyone. You can get holes so big they can swallow people and cause severe injury when someone mowing their yard falls thru.
it looks too big for any regular burrowing animal but I never really knew how much they borrowed anyway.
Water was my first thought but AFAIK there is not enough water to form such a hole, there is a cesspool about 20 ft away from this hole (to the outer edge) so there is somewhere for it to go.
rotting wood was my next thought, but wouldn’t there be some evidence of it like discolored soil?
Also it looks the hole has roots through it, I would wag an animal would have cut the roots as it makes traveling through difficult. This leads me back to the water hypothsis.
The real worry is that the soil had to go somewhere.
Where is the hole in relationship to your house? Does it flow towards your house, or towards the street?
Are sinkholes common in your area? Natural caves? Old foundations?
Are there major utilities in close proximity? Sewer lines, storm sewers? Underground power lines? If so, call the appropriate company and have them investigate.
Otherwise, consider getting a long, thin metal pole and doing some probing. As I said, it had to go somewhere. Is there a larger hole underneath that this you will have to worry about? Is your entire house about to collapse into a sinkhole?
Holes sometimes appear where a well was located decades ago. If you live in Pennsylvania, then it could be an old coal mine shaft that is collapsing underneath. I hope it’s just an animal’s burrow. Good luck!
did some more careful measurments, the hole where exposed (which I assume is the point closest to the surface) is apx 10 ft from the house and 15 ft to the outer edge of the cesspool.
There is no utility lines nor any piping from the house that lets out there.
The pipe to the cesspool comes from the other direction and there is no plumbing in that side of the house. The downspouts are about 30 ft away from this hole. The washing machine water is diverted into a trench about 20 ft from the hole with any overflow diverted through a pipe to the edge of the property, again not close to the sinkhole.
The hole seems to get deaper torwds the foundation
No but colapsing cesspools have been known to cause sinkholes - I don’t know much about it but think it’s too far away.
I am considering filling it with water just to get an idea how big it is.
My old land lord bought a farm 40 years ago.There was an old house on the land . He tore down the house
and burned the rubble.He then pushed it into the basement and filled it in with soil. 40 years later he still
has sink holes that show up every year…
Maybe a trip to see a long time resident of the area is due.