Unless you are in an area where teh frost depth is extremely low, I would think that the footing would be there simply by virtue of the depth of the pool. What is your frost depth?
I would definitely put the bottom of ftg below it, either way.
Assuming the pool is empty in the winter and the frost depth will be measured from the bottom of the pool. A complete footing down to frost depth under the pool,(not just the walls), will be prohibitively expensive. Use granular material to break the capillary action of moisture and horizontal insulation under the pool bottom to stop frost penetration. A good drain system around the perimeter is also recommended.
I'm with civilperson on this one. We have had great luck with more or less letting the design of the pool dictate the depth. The builders we work with wire up the reinforcing, shotcrete the pool and walk away. We have never seen any issues with pools breaking up during winter even though the pools we design are empty at that time. Just a good granular cushion underneath for resistance to frost. And yes, make certain a drain tile system is installed around the pool; you don't want the pool to float, just the people swimming in it.
pardon my ignorance, but coming from the southwest, draining a pool is rarely if ever done unless absolutely necessary. Are in-ground, outside pools in colder climates drained each winter? If so, wouldn't that tend to increase the frost depth at the bottom of the pool due to the trapping of cold air? (unless the pool was covered and insulated). It seems like just by keeping some water in the pool may help to keep the bottom of the pool warmer. I doubt it would ever freeze solid.
In this situation the guy wants to use CMU for the pool. IT will be in the side of a hill, and the bottom end will be exposed, and have a waterfall effect at the edge. My main concern is also settlement in the wall, and it becoming out of level.
cvg
Pools left unheated will freeze 8 feet down in Nebraska and similar climes. This freezing can be destructive in spring when alternate freeze/thaw occurs. Draining the pools is a Halloween/Labor Day ritual in many locales.
