We just had our pool installed in May - 24' above ground round. I was in it today and felt something under my foot /under the liner. It feels like it might be roots. We had it professionally installed and the company came in with a backhoe to level out the yard - pulled up lots of roots & vines in the process. The pool installers leveled the ground, added a layer of sand and then installed the pool. There are no trees near the pool in that area. How concerned should I be? I can imagine that anything can grow under the weight of 15000 gallons of water with no sunlight!?! Could it be the weight of the water and use of pool packing the sand down more around what was already there? I'm worried about the liner getting ripped. Any advice? Precautions? Fixes?