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I need guidance about how to place an above ground pool partially on top of disturbed soil.

Last year (june 2022) I removed a pond from my garden, width: 2mx1.5m approx, depth: 1.3m.

I filled the hole with some pieces of conglomerate wood and soil.

This year I would like to place a round pool on top of where the pond was. spec: 3m diameter, 1m depth, total capacity: 7000 litres.

I am thinking of digging again the pond hole and fill it with big stones, then smaller, then aggregate, then sand… and dig less deep the remaining parts of the circumference (based on stable soil) and add some aggregate and sand to level there too…

Am I on the right track with the idea or will it be very risky to do anyway?

Thank you in advance!

catch22
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  • Pools spread the weight over a large area, so disturbed soil is not as much as a problem as it is with building footings. – crip659 Mar 12 '23 at 20:53
  • @crip659 thank you. do you mean that I should not go through the process I mentioned? what problems do you refer to with the footing? – catch22 Mar 12 '23 at 20:57
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    A house footing is usually a foot and a half to two feet wide with a foundation and house on top of it. Must be on undisturbed soil. A pool spreads out a lot of the weight so much lighter per foot(a person might be heavier per square foot than the pool). The wood probably should be removed from under the pool, digging down and adding stone and sand might not be needed, just the sand. – crip659 Mar 12 '23 at 21:12
  • @crip659 got it, thank you so much for the clear explanation. The plywood is actually buried under and mixed with the soil.. it worries me that it decomposes and the soil on top of it ends up sinking. – catch22 Mar 12 '23 at 21:19
  • Plywood is usually thin so it should not sink much unless there is a good ply/stack of it on top of each other. Was thinking of small pieces that might push up, but flat plywood should be okay. – crip659 Mar 12 '23 at 21:43
  • I would put some gravel or sand and hire a plate compactor to compact it. – Rohit Gupta Mar 12 '23 at 21:56

2 Answers2

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Dig the junk out, remove the wood, rent a compactor, refill a few inches at a time, compacting each layer before adding more.

Wood is not fill.

If you wanted to wait several years, the "big stones approach" might work, after settling. Big stones are very hard to compact effectively.

Ecnerwal
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The biggest problem you want to avoid is all that junk coming up and puncturing the pool liner. You need to get rid of wood, sticks, potentially sharp stones, nails, screws, bits of glass, etc. in the soil under the pool. Some of those things, in the right circumstances will work themselves up to the surface and pose a threat to the integrity of the pool liner.

The way I've always done it is to dig out about 5-6 inches (12-15cm) of the soil and replace it with good quality sand. That allows you to easily level the surface--which is particularly important for an above-ground pool. Then it's a good idea to invest in an underlayment mat to prevent punctures and/or tears from objects in the soil.

As far as the pond fill, I'd dig out all the wood and whatever other miscellaneous debris that are in there and fill the resulting void with the soil that you dug out to install the sand layer. Stone, gravel, etc. are not really necessary and may make problems later. Using a power compactor is not a bad idea, but you can probably do without one if you take your time and compact the fill as much as possible as you go.

gnicko
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  • agree with the removal and fill but using sand could be problematic in rainy climates, as it can wash away from underneath the pool. "Crusher dust" or fine aggregate is best as it compacts well and does not wash away. – P2000 Mar 13 '23 at 14:29
  • @P2000 - It won't wash out if you "capture" the sand in the hole made by removing the top 4-5 inches of dirt. – gnicko Mar 13 '23 at 22:33
  • yes, good point to clarify: if it is solely a hole fill it would be fine, not an inch more, but sometimes people cheat and use it to raise & level, which is when it fails – P2000 Mar 14 '23 at 03:41