How close for footings?

[mohawk]

Up here in Minnesota we have huge temp fluctuations, so we'll be digging in footings for an extension on the deck. The soil here is very sandy. I was wondering how close to the pool the footings can go without hurting the integrity of the pool sides. Right now I think there must be a hole in the lining because the water keeps going down lower-now that the ice is off. The pool was installed last year and it's a 30' round. Any advice is welcomed. Thanks. :)

[haze_1956]

I have 12 inch round footings about 8 inches from the bottom rail of my 21 foot pool.

Dug holes 36 inches deep, used cardboard sonatube as a form above ground and filled them with concrete, soil is sandy and I saw no effect on pool.

As long as the sides of the hole don't start falling in, you shouldn't have a problem. Although I wouldn't leave the holes open too long, dig them and fill them back up as soon as possible, why tempt fate?

If you need to have them inspected first, sleeve the entire hole with cardboard sonatube and cover it, in case of rain.

[matt4x4]

It all depends on soil conditions. Many use surface deckblock, it will heave (relatively even) with the frost - and then settle again to regular elevation, however, it CANNOT be anchored to your house then.
If you need/want to use footings, how close you can get to your pool is relative to the soil and conditions you are working in, if it's very sandy soil, it can cave at just about any time since it does not harden up when it dries, however, clay soil, once dry (mid summer) is very hard and you can cut into it vertically without risk of collapse.