Soil erosion outside gunite in-ground pool

[bobdobalina]

Hi. My wife noticed that the grass around our inground pool was starting to fall. We have owned the home and the pool for a little over a year. It "works" fine, and sits way, way above the water table.

So I took out the shovel and did some digging and I have established that there are a number of cavities (3-6 feet deep, but only 1-2 feet away from the pool) around the perimeter of the pool (on both long sides). I cannot examine the shorter walls without removing a lot of bluestone. I haven't done that.

The pool is ten years old, we were told that it was massively expensive and we believe it (not the money we would have spent, but whatever-- that's life in an overpriced Connecticut suburb.), and it has no cracks and no leaks (that we know of, at least). There are retaining walls on both long sides of the pool.

One hypothesis about the cavities is that they have been caused by the sprinkler system (it seems to have at least one leak, which corresponds with the biggest cavity).

So I guess I have three questions:

1. Is my hypothesis plausible, or is something more sinister likely to be afoot?
2. Should I just have some dirt delivered and shovel it into the cavities, or should I be consulting with engineers and/or evaluating more major surgery?
3. If the answer to #2 is "buy some dirt and shovel it in," what kind of fill should I be buying?

Thank you.

 

[JasonLion]

Welcome to TFP!

One way or another it must involve water flowing through the area. The cavities sound very large for a sprinkler leak. Perhaps rain runoff from the whole deck area is involved.

Use gravel for most of the fill. That way if there is more water in the area it won't wash out the gravel. Then top off with dirt.

 

[bobdobalina]

Thanks for the fast reply!

The runoff-from-the-deck hypothesis makes sense.

The pool has a valve that automatically fills it if/when the water level drops. Of course I could turn it off and watch it to be sure. But before d If the pool had a real leak, would I almost certainly know it?

 

[JasonLion]

With auto fill a fairly slow leak is not at all obvious. Your levels will fall from the water replacement, but for a fairly slow leak that won't be obvious right away.