Solid Base for Wall Support

by Brent
(NC)

I have read some very helpful information on your site and I figured you could help me make the right decision for a 27' install I will be doing in about a week.

I actually have two problems - the first is my soil is very sandy all the way down until I hit water (around 5').. there is no firm ground. What should I put down around the perimeter where the bottom track and wall will go to ensure I have a solid foundation?

Do I need to put patio blocks all the way around so not only the uprights sit on them, but the entire bottom track as well? Or, would solid packed gravel or something similar do the trick?

I'm also not sure how far outside (or inside) the pool wall I should be concerned with a hard packed surface.

My second concern is a 2-in-1 deal: My pool will be going over top a portion of my drain field for my septic system. There is really no way to avoid this as my fields are 3' wide by 75' long and I have 4 of them. Unless you tell me differently, the good news is that I have perfect soil for a septic system, and since I have several very long fields, I think I should be in good shape (and so most everyone else tells me including the county environmental health dept that deals with septic systems).

The 2nd part of this is after I removed the sod from the area where I want my pool, I keep finding rocks that were used

in the drain fields. I am not sure if this is leftover rock that was scattered on top of the ground, or if the rock just continues to go deeper until it reaches the actual drain field pipe. I do not want to dig any deeper than necessary so I can keep the most distance possible between my pool and the drain field below, but I also need something to protect my liner from the rocks - will the 1.5" styrofoam board work? I also have gorilla pad.. I know this is very thin, but is supposed to keep from rocks penetrating and piercing the liner - I figured I would put the gorilla pad down first, then the foam on top, then liner.

Sorry this is so long, I tried to consolidate it. I appreciate any advice very much.

Hi Brent.

The best thing to do is remove several inches of sandy soil in a strip about 2-3 foot wide around the circumference of the pool. This area could then be filled with a crusher run, crushed granite or anything the sand and rock company has that packs solid. The area should then be packed solid and then blocks can be used just under the uprights.

There is nothing wrong with using foam under the liner. It’s still important to remove as many of the rocks as possible and possibly pack the area before putting the foam down. Large rocks will cause the foam to crack and that could be noticeable under the liner.

In my experience your water pipes should be just fine. It sounds like you are well on your way to a very good installation.