33

Our house had a nice cedar pergola in the backyard, about 20'x16', whose posts began to rot at the base. It was covered in grape vine... Nice for shade but not for a falling down pergola. Needless to say, a few months ago we got a pretty good wind storm that finally blew the thing over.

I finally got to dismantling the thing and would you believe it, there's a damn swimming pool underneath it! At least that's our best guess as to what it is.

It's only ~3.5' deep at the deep end and ~2.5' deep at the shallow end... So if it was a swimming pool it wasn't for very large people.

Anyway, we have found ourselves with a huge amount of buried and likely reinforced concrete smack dab in the middle of our back yard. The original plan was to 1) remove pergola 2) plant grass. That's now a lot more complicated.

So the main question is:

How do we remove or mitigate the concrete situation so we ensure the backyard can be enjoyed for a long time.

pool1 pool2 pool3

isherwood
  • 119,766
  • 7
  • 148
  • 349
tbox
  • 749
  • 3
  • 12
  • 23
  • Related : [Decommissioned (Empty) Swimming Pool](https://diy.stackexchange.com/a/177797/41369) – J... Mar 28 '22 at 17:35

5 Answers5

36

Where I live (NJ, USA) it's illegal to bury a pool. If the pool was filled with soil and hidden it's possible you would have recourse to get the person who did it to pay for remediation. Unlikely but possible. However if the pergola structure was built over the pool like a platform, it may be legit.

The correct way to permanently remove a concrete pool, where I live, is to break the concrete up into pieces no bigger than 8 inches in any direction. For something that size you're looking at a jackhammer attachment to a sit-in machine of some kind. I think I saw a specialized one with an arm that had both a jackhammer and back-hoe on it so the pieces could be moved to their desired resting place..

You start by breaking up the floor of the deep end, then do the shallow end and push the pieces on top of the deep end. Then you break up the walls and make a layer on top, then the deck goes in last. All in small pieces.

All biodegradable material MUST be removed and not buried in the hole, as must metal, plastic, and anything other than concrete and dirt. Leaving beams or logs in the hole will cause problems later (and fail inspection).

After doing all that you get an inspection, then add clean fill if necessary (free from a local construction site) and finish with landscapers cloth and top soil. Expect some subsidence and to re-apply top soil after a couple of years. You may not need much fill but in a more typical pool with a real deep end you would. I'm not sure if the cloth goes between rock and fill or between fill and top soil. If someone adds that to the comments I'll correct this.

If your house is rated (for local taxes) as having a pool, removing it will reduce your tax bill and makes it worth the hassle of pulling permits and doing it properly.

Note there may be live buried wires in the area beneath and around the pool. Get to know the installation before you proceed, especially any surrounding lighting or pool machinery.

jay613
  • 28,850
  • 2
  • 36
  • 112
  • 1
    Thanks for the details on how to break it up. I'll pick this as the answer since it has more details than my answer and is clearly the only reasonable approach – tbox Mar 28 '22 at 05:19
  • I added a step to the answer: you might need some clean fill before adding top soil. Also, if you do this correctly you do not (per your answer) need to feel sorry for the next person to dig it up. That's the idea behind this method. – jay613 Mar 28 '22 at 17:38
  • This seems like a good procedure for leaving all the concrete on-site and just burying it... much of it seems unnecessary though if they just want to remove the concrete and fill it in with soil. – TylerH Mar 28 '22 at 17:41
  • 1
    @TylerH this is the method used by professional pool demolition firms in my area. I *assume* carting and dumping the concrete costs more, otherwise they would do that. – jay613 Mar 28 '22 at 17:45
  • 3
    `Expect some subsidence and to re-apply top soil after a couple of years.` You shouldn't need to if it's done to code. When a pool is filled properly (to a degree that no longer requires you to disclose that it used to be there) the ground must be finished to a level that allows it to be used as a foundation for any other out-building type structures that might be built upon it later. This means the load bearing capacity of the ground should be solid at the end of the burial - you use a packer and finish it like you would a foundation. – J... Mar 28 '22 at 17:49
  • 11
    BTW if burying a pool is illegal where you are and you purchased title insurance when you bought the property, you may be covered for the costs involved in bringing this up to code. It may be worth checking into. – jwh20 Mar 28 '22 at 22:28
  • 1
    Also: aside from old pool wiring, be on the lookout for the remnants of pool support plumbing (water lines for filling the pool, overflow/drain lines, etc) still hidden in that area. You'll need to make sure they're properly capped/disconnected. If not done properly, a slow underground leak can cause serious problems over time. – bta Mar 29 '22 at 04:25
  • 1
    @bta Pools generally don't have buried water lines for filling. The rest of the plumbing will be abandoned and no longer connected to a pump, so there's no reason to cap old overflow, drain, or circulating lines. There's no pump and no water, so... empty pipes can't leak. – J... Mar 29 '22 at 11:17
  • @bta Actually, I don't even see a skimmer or any jets, so most likely this was just a wading pool with no plumbing whatsoever - just a concrete bathtub. – J... Mar 29 '22 at 13:47
13

Sounds like a nice size Koi pod; I am jealous , mine is only 5 X 10. Depending on intended use , filling it is a option. Use any cheap fill then put about 6 in. of topsoil on top. At Koi / pond club meetings, I have heard about more ponds being filled than being removed ( if reinforced concrete).

blacksmith37
  • 8,143
  • 1
  • 14
  • 30
  • 1
    We thought maybe a koi pond but it has a pool drain in the deep end. Do koi ponds usually have bottom drains like that? Ones I have seen use submersible pumps. Either way, sound like the best approach is going to be to jackhammer it. I am curious to see where the drain pipe plumbing leads to. – tbox Mar 28 '22 at 05:10
  • 2
    @tbox Koi pond was my first guess as well. Drain is possible for ease of cleaning. Koi ponds need quite a bit of maintenance. One of my neighbors has oen with a drain. To clean he temporarily moves his koi to 2 big plastic (1000 liter) barrels, then drains the whole pond, cleans it and refills. Natural drainage, he doesn't even have a pump to empty it. (The filtration pump can't do dual-duty in his case, although there exist filtration pump systems that do have that capability.) – Tonny Mar 28 '22 at 08:39
  • 13
    Given that pools are (mostly) watertight, just filling it with dirt might not be the best idea if the area gets significant rain. At least unless you want to end up with a 20'x16' swamp right in the middle of your garden. – TooTea Mar 28 '22 at 10:01
7

To propose one solution to my question: rent a ride-on-back skidsteer with a jackhammer attachment, break it all up (bottom included for drainage) then backfill with dirt. Not sure if there would be long term consequences other than feeling sorry for the poor person who tries to dig in this spot in the future.

tbox
  • 749
  • 3
  • 12
  • 23
  • 1
    That sounds reasonable. Whatever it was before (fish pond? wading pool?), the previous owner put the pergola on top because that was cheaper/easier than removing the concrete. – manassehkatz-Moving 2 Codidact Mar 27 '22 at 22:20
  • 1
    This is really the only answer if your goal is a lawn. You need to lower the wall height and allow drainage. – isherwood Mar 28 '22 at 00:14
  • 2
    Someone did this in my yard and I can see the outline of the pool every summer because it browns out above the wall before the rest of the lawn. Perhaps the wall wasn't taken down far enough. – JimmyJames Mar 28 '22 at 15:32
  • 2
    You can't just DIY a pool removal. You need permits, it needs to be done according to rules (which depend on the jurisdiction), it needs an approved engineering plan, etc. If you just fill it in like this, it remains a "used-to-be pool" and you're required by law in many (most?) jurisdictions to disclose when selling that there's an improperly buried pool in the backyard (which *will* negatively affect the value of the home). If you do it right that liability goes away. – J... Mar 28 '22 at 19:18
3

You have suggested jackhammering, but from my experience concrete cutting is the better option for thick and/or reinforced concrete. It is cleaner, quicker, less noisy, and less frustrating. Call an expert to do it.

I would remove the concrete rather than leaving it. Concrete immediately underneath the soil makes it more difficult to grow anything. It is a large amount of concrete (I would estimate about 8-10 tonnes) so will definitely cost a bit to dispose of, but it will be worth it in the long run.

Xavier
  • 31
  • 1
  • 1
    This is especially something you might want to think about if you'd ever want to plant a tree in the area. A layer of concrete can restrict how deep the tree's roots can penetrate, which can limit the growth of the tree. This can be particularly confusing for a future owner who doesn't know about the concrete. – bta Mar 29 '22 at 04:27
  • 1
    From the other direction, if you're into working out busting up the pool could be an entire summer of fun with a sledge hammer. I know someone who did it that way. – Dan Is Fiddling By Firelight Mar 29 '22 at 11:50
-2

First question is, what state and county do you live in? I can assure you that your state Environmental Protection Division and your local county or city has a code or an ordinance that's gonna cover this exact thing. Take a few minutes to either go online, call or even better take a field trip to your local governmental building and go to the code enforcement department and I'm almost positive they will either one, give you the exact answer you're looking for or two, they'll be able to lead you to exactly where you need to go to get the answers you're looking for.

I hate to see people being led to spend money based on opinions of others who don't first ask the correct questions about your situation for example, what state do you live in? Every state has different laws about everything, always remember that sir. Next, a septic tank will never, ever look like a swimming pool with a walk in entrance, that's just absurd on all levels come on now, let's be real here and never will a Coy Pond or not one which I've ever seen in my 52+ years anyway.

Azor Ahai -him-
  • 103
  • 1
  • 6
Jim Stolze
  • 11
  • 5
    That's a very coy pond you've got there... – FreeMan Mar 28 '22 at 23:11
  • 3
    Hi Jim, welcome to the site. You may be wondering why your answer has attached negative votes. Know that answers are where you provide answers to the question. Questions to the OP, and comments on other answers go in 'comments' under the respective posts. – Lamar Latrell Mar 28 '22 at 23:32