dirt erosion/sinkhole where sewer/water main were buiried

[Honky Lips]

so, 3 years ago in our clay soil the water and sewer main were installed. and I noticed today that there is a little sinking at the foundation directly where the mains run under the foundation. apparently the water is finding its way down the backfilled area. how deep its eroding I dunno. I'm assuming just keeping an eye on it and fill it back in as needed is all I can do. short of total excavation and re backfilling. but with the clay content I'm not sure you could get it perfectly backfilled. so, just keep an eye on it and keep adding a shovel full of dirt as needed?

 

[Bogus One]

Find a way to "mark" it's current level and monitor it from there
Our new (to us) house had/has a major sinking issue off the back patio. Knew it going in and am pretty sure of the cause. Not too worried about it in the short term.
I measured and recorded the width of slab cracks and elevation. Have it written in Sharpie at the locations and in the Den.
In two years it hasn't moved.

Now, I'm dealing with "Poof Dirt". Total silt outside of the main building pad.
With clay, you also need to be watching for too much moisture in it, as it will swell.
How wide and deep a trench was it originally?
Edit: And what is the bottom of footing elevation compared to bottom of trench?

 

[Honky Lips]

Find a way to "mark" it's current level and monitor it from there
Our new (to us) house had/has a major sinking issue off the back patio. Knew it going in and am pretty sure of the cause. Not too worried about it in the short term.
I measured and recorded the width of slab cracks and elevation. Have it written in Sharpie at the locations and in the Den.
In two years it hasn't moved.

Now, I'm dealing with "Poof Dirt". Total silt outside of the main building pad.
With clay, you also need to be watching for too much moisture in it, as it will swell.
How wide and deep a trench was it originally?
Edit: And what is the bottom of footing elevation compared to bottom of trench?

it was originally like 8-10 feet deep and 2-3 feet wide.
we have basements here. so its below the footer and under the basement floor. haven't noticed any cracking or settling in the basement floor.

 

[Bogus One]

it was originally like 8-10 feet deep and 2-3 feet wide.
we have basements here. so its below the footer and under the basement floor. haven't noticed any cracking or settling in the basement floor.

So it's surface level about 6'-8' ABOVE the basement floor level?
If so, probably not a big deal. U/G guy got lazy with the last few feet of backfill
Make yourself a probe out of some rebar, see how far your body weight will sink it in, and report back

 

[east_beast]

I have a big depression in my pasture (bisg as in maybe 15x10, maybe 3 feet deep). It was a small depression that kinda looked like a natural roll-off three years ago but now it's clearly a depression with soil cracking around it (clay soil). I found some old satellite images and it looks like there was rubble buried in that spot. Can't tell if it was construction debris or stumps but either way, it has settled and/or rotted out and now I have this depression. Think I'm gonna have a buddy who runs dump trucks bring me a load of fill dirt. I think one load would do it. One load is all it's gonna get. Just gotta wait for a dry spell this summer to firm up the ground.

 

[SomeGuyFromOlympia]

My Grandma lived in a neighborhood, evidently when they cleared the development they just dug big holes and buried all the stumps
All of a sudden, (30 years later) about every third house, between the houses, there was a sink hole pattern forming. Every third house. I ended up having to go cut some trees down that were leaning over the house and removing the stumps, the neighbors, it was up under their foundation, I fixed our side and sold the house
I hope it doesn't get too big, they can do damage

 

[arse_sidewards]

My Grandma lived in a neighborhood, evidently when they cleared the development they just dug big holes and buried all the stumps

"back in the good old days people took pride in their work"

 

[bgaidan]

so, 3 years ago in our clay soil the water and sewer main were installed. and I noticed today that there is a little sinking at the foundation directly where the mains run under the foundation. apparently the water is finding its way down the backfilled area. how deep its eroding I dunno. I'm assuming just keeping an eye on it and fill it back in as needed is all I can do. short of total excavation and re backfilling. but with the clay content I'm not sure you could get it perfectly backfilled. so, just keep an eye on it and keep adding a shovel full of dirt as needed?

Sounds like it's just settling caused by shit compaction. Unless there are open fissures where water is actively draining in to the soil and under the foundation, there's probably not much to worry about. Fill it in and keep an eye on it. If it keeps doing it, maybe get a little concerned.