Mistake made - Need to build up back end of pool! HELP!

[madisonmama]

We are putting up a Bestway 20'x48" above ground pool, and we based our entire project off of keeping it level with the floor of our back porch (so we can basically walk right into the pool). The problem is that the porch is not level, and after all of the digging, tamping, and leveling was done we have discovered that the back end of the pool will be about 6 inches off of the ground in a few places because our entire yard is sloped. My husband's idea was to backfill and get it leveled and tamped (which we did), and then build a small retaining wall around it. I don't think this is going to work, and I am so worried about going forward with this plan. We plan on using the same 11" retaining wall stone we are using on the other side (where were had to dig down). I would appreciate and advice, I can't seem to find any info or "how to" videos on this anywhere. I can post a pic of the trouble spots in the comments. Thanks!

 

[madisonmama]

Here are the pics of the back part I’m worried about. You can see the orange paint lines where the edge of the pool will be

 

[bmoreswim]

I'm sorry you are having trouble with your pool installation. The reason you don't see many "how to" videos for this situation is that, as you suspected, it is a "how not to" situation. Building up for an above ground pool is generally a recipe for issues down the road. Any wall you build, unless you are going to spend more on the wall than the rest of the project, will likely not support the pressures exerted on it. Additionally, the soil is not adequately compacted. I can't quote you what mechanical compaction specifically needs to occur, but it will certainly involve more than has been done. The real issue is that soil compacts much more than your husband is thinking it will, based on the soil used and hand tamper approach. Replacing the soil with a different aggregate would be recommended, though I'm not the person to suggest specifically. And powered mechanical compacting would be needed. But then you would still need a proper retaining wall. I suspect the wall your husband had in mind would be woefully inadequate, based on his thinking that the above would work. Sorry for the not so good news (and perhaps my bluntness), but you were certainly correct to ask. Huge plus there.

I'm hoping that if there is a path forward to filling to achieve your desired elevation, someone properly educated can assist. But I know enough that the approach in the pictures won't work.

 

[Newdude]

+1 MM. Let's do some math. The pool has a volume of 1256 cubic feet. There are 7.481 gallons per cubic foot and each gallon weighs 8.33 lbs. 78,269 lbs needs to sit on your pad. That's the average weight of 16 Ford F-150s.

Always dig down to undisturbed ground, never raise the ground up.

 

[Bperry]

Best advice would be to dig it lower to avoid backfilling. Could pour a cement pad to build it back up some?

But all that said it’s not a hopeless problem. Backfill is compacted regularly all over the place and can be done with a rented plate compactor from Home Depot. Generally done in small lifts of ~6”.

For the retaining wall, you’ll want something other than just hollow home depot wall blocks. It’s hard to tell how high it will be but looks like maybe 18-24”? Versa-block makes a solid wall block that would be much better than hollow blocks. The issue with the retaining wall plan is that putting a pool right on top of it creates what they call a “surcharge” which is an abnormal load on a retaining wall. Generally surcharge walls will require a permit to be pulled and the wall designed by an engineer. It’s not rocket science, but not that hard either. General advice is making sure the surcharge is no closer to the wall than 2x the height of the wall. That would mean if your wall was 24” high, the pool needs to be inset at least 48” from the edge. All that is “rule of thumb” type advice that can be changed if hiring an engineer to design the wall or by building codes.

 

[madisonmama]

the "wall" we had to build up at the back end is approx 12" high. We bought nice 11"x4" retaining wall stone to use, not hollow blocks, and are putting it together as instructed. We are also using heavy duty glue even thought not all videos recommended this. I was thinking the same thing you mentioned, that sitting the pool right on the edge of the retaining wall would be a problem....so maybe we could bring the edge of the wall out by 24" from the pool (based on your info above). thanks for the idea

 

[Bperry]

the "wall" we had to build up at the back end is approx 12" high. We bought nice 11"x4" retaining wall stone to use, not hollow blocks, and are putting it together as instructed. We are also using heavy duty glue even thought not all videos recommended this. I was thinking the same thing you mentioned, that sitting the pool right on the edge of the retaining wall would be a problem....so maybe we could bring the edge of the wall out by 24" from the pool (based on your info above). thanks for the idea

You should bury a row or two of blocks under the ground and on top of non-excavated soil, preferably crushed stone. I’ve never heard of glue together retaining wall stone so can’t say whether that’s appropriate. Be careful with that and take a look at some YouTube videos of what happens when these pools aren’t built right and fail. It’s pretty spectacular.