Semi Inground Pool
I am installing a 15x30 BERMUDA 54" pool in the same foot print as an in ground pool that was removed. The previous pool was demoed and the concrete decking around the pool was used as fill in the deep end. I then took sand and filled the pool to about 3-4 feet from ground level. I then let it rain and allowed about 2 feet of water to sit in the hole for about 2-3 weeks. I then drained the water and noticed that the sand had compacted and there were several "sink holes". I was expecting this.
After letting this dry for a few days I again added sand to top this off. I added about 6 inches then packed it with a plate compactor. The next morning I noticed there was an area where the sand caved in and was almost quicksand like. I put more sand on top of this and allowed the sand to sink in again. I figured I would do this until this no longer happens.
I am assuming that there is still some voids in the concrete rubble under the sand. Another issue I came across is along one side where there was a large crack in the previous pool the sand is very spongy. No matter how much I compacted the area it remained spongy.
The questions I have are
1--Do you see any issues with me doing the pool install here. I have a gorilla pad that I plan on using under the pool as well as the coving for the smooth transition from wall to floor.
2--Is there anything I can do to fix the spongy soil. The area is along the straight side where the supports will go. Will this play a factor into the strength and support of the pool? Or will I have to shift the pool over to be out of this spongy area?
If you require any additional info I can provide as needed.
Hi Mark. If it were me I would remove the sand and fill the hole with something that will pack solid. Sand will always be soft and could easily shift under the weight of that much water.
Above ground pools should only be set on solid, firm ground. I would have either filled the hole with dirt or crushed granite. There are other types of materials that would work just as well but it needs to be something that will pack solid and never shift, or get spongy.
Sand is OK to use for a couple inches of cushion under the liner but not under the pool framework.