This was the last winter I decided to take down out Intex Ultra frame, going to leave it up from now on for the winters. So I decided to pull back the foam sheets, and gorilla pad to see how things are under there after redoing it last year. I pulled some big roots out last year when I had redone it, after having a pool on it for the 3 years previous. (was on a sand pile then in a frame).
About 10,000 small roots somewhat surprised me, but not really. I knew I had some larger roots I pulled out last year so these are just the smaller ones still trying. Nothing came through the pad nor foam, so that was good.
My plan dealing for these was two fold. I was no way going to rip up the ground again so only thing to do kill the roots. Being in a rural area I had access to some vegetation killer that kills anything it touches. So the ground under the pad got a soaking (3 times), that should solve that issue. I also decided to sacrifice a chainsaw blade and cut a 8" deep swath around the pool perimeter, cutting any roots that invading from outside the area. This also made sure the vegetation killer did not work to the trees.
Worked like a charm, had to sharpen it several times, but it did the trick. You would be surprised how well a nice slot you can cut in the ground! The $8 for a new blade was worth it. Sure found a lot more roots than I though I would, plus a couple good size ones (3-4" diameter).
Gorilla pad and foam all back down, waiting for the pool to be put up in couple weekends. Hope this keeps those roots at bay now.