[Cidertom]

Kind of related subject:
I was on an engine company defending a house against a wildfire a few years back.. We used the owners pool as a water source. It appears that the water table in that area is close to the surface. Soon after we emptied the pool it started out of the ground. Rose up about a foot.

Insurace Co paid and didn't whine (something about cost of pool vs 450K house).

So when taking a pool out of service be careful about ground water table.