Pipe Break Below Building

[CURVEB]

Hi - not sure if this is the right forum but wanted to see what kind of response I got. I'm investigating a "sink-hole" issue where a building owner is saying that a water pipe broke under his building, causing it to settle, shift, etc. The evidence of damage is some minor cracking in the caulk joints, separation of trim, and the fact that the floor elevation drops by up to 2" from one side to the other (over ~20 ft). I have reason to believe that there was a pipe broken somewhere below the ground floor (a slab-on-grade). and it happens to coincide with the most "sunken" area of the floor.

I'm trying to determine if it is possible for a building to shift by this much due to water in the soil. I'm thinking there should be evidence of the soil scouring out from around the building/below the footings, but I can't find any. Any thoughts on what evidence I should look for, or if the water in the soil could be a plausible cause for this movement/damage?

 

[oldestguy]

Sounds fishy. If it is a continuing break problem there ought to be some ground water showing and possibly even rising. A test boring or two might be a good idea. However, I'd get a geotech involved since he (she) may have suggestions as to where and just how to do this. What's the history of this? So far it sounds pretty minimal if there was a pipe break. I'd be more inclined to hear this has been a long time ago thing and possibly just related to other things, such as soil shrinkage due to drying. Is there a zone of clay under the building and trees nearby that may be taking water and causing shrinkage? It is common to hear of these things this time of the year in such country. Just where is this? and what is the geology?

 

[CURVEB]

Thanks for the response. It's an older building (50+ years), a 1-time break possibly caused by nearby construction, and located less than a mile from the beach on the west coast if that tells you anything about the geology. The water bills show a massive usage for this cycle as opposed to the previous ones (like 10x the normal usage).

Even if it did not scour away any soil, do you think it's possible the influx of water simply compacted the existing soil further and that caused the sinking issue?

 

[oldestguy]

With the water usage,yes a likely break. For fixing, yes you need to find it. So it's somewhere after passing the meter. Not being there I'd start with a stethoscope listening on any pipes that are "buried". Any use of test borings may help, look for high water table, etc. Is there an outside hydrant fed by a buried line? Flowing water can rearrange soil particles and cause some settlement. More likely erosion, but then where is the soil moved to? Any possible cracked sewer taking that water? Another possibility, but should be obvious. How about toilets with a leaking rubber stopper? Do you hear it re-fill by itself frequently? Is there a buried lawn sprinkling system that has a leak before the valve or distribution lines leaking, but not obvious on the surface? Another thought. Take a hammer and bounce it along the concrete floor. Over a solid contact with soil it sounds dull. Over an area with voids it rings more. Sometimes a hollow sound also. You may have more loss of soil than what the slab might indicate.Another idea. Assuming there might be a break under the slab, you can core the slab and look for water, take a soil boring with a small diameter auger, as from landscapers with a bulb planting auger.