I am not sure what the water table is at. The PB mentioned that it is soemthing what you described, to collect water that accumlates around the sides and I guess under the pool, sort of like a safety device I guess. He said the water should drainout naturally but it really hasnt moved since the end of summer. I will take the shop vac to it and take it down another foot or two. The PB said that not too many other builders put this on their pools, I guess its just an extra extra.

what about winter, I guess the water in there just freezes.