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How to fix backyard drainage & waterlogged clay soil?

Hi all, my backyard is suffering from waterlogged clay soil.

Previous owners never looked after the yard. Or had proper drainage.

We have a high water table, when I dig down 2 foot we are hitting the water table. I am thinking of digging 3-4 feet down and include a series of french drains that will be linked to an easement in the yard.

Would this be the best approach?

The soil is waterlogged when walking on it and doesn't dry out even after long periods of no rain. The neighbours say it is a high watertable so nothing can be done, I'm not so sure. Some other parts of the yard are like this, and others are not. Keen to hear your thoughts and I'll keep you updated on my progress!

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Comments

EricL

Hello @Alan_

Welcome to the Bunnings Workshop community. It's sensational to have you join us, and thanks for sharing your question about fixing your backyard drainage.

Putting in the French drains sounds like a good plan. Would it be possible for you to draw your drainage plans on paper and sharing it with the community. This will give us a better idea of its size and scope. My only other thoughts are to engage the services of a landscaping specialist who has experience in drainage and waterlogged soil.

I also suggest having a quick look at this discussion - Drainage to fix a muddy lawn by @Ben

Let me call on our experienced members @Dave-1 and @Nailbag for their recommendations.

If you have any other questions we can help with, please let us know.

Eric

Alan_

https://www.workshop.bunnings.com.au/discussion/comment/40640#Comment_40640

Thanks Eric,

I have done a rough design. The blue will be the french drain, the orange box will be service into the easement. The property has a slight fall from the front to the back of the property. Any further suggestions would be super. I looked at the posts you mentioned, thank you. Very similar issue, my pitch fork went all the way in like a hot knife in butter.

Dave-1

Evening @Alan_

Your problem sounds like an interesting one for sure.

When you say parts of your yard are drier would it be possible to have a couple of pics of the overall yard?

The idea of a French styled drain with gravel in it sounds like an idea, tho not sure if I would dig it as deep at 4 foot. If you hit water at 2 foot I would suggest to have the trench at that depth with someplace for the water to drain to.

After I installed new sewage pipes across my yard in a diagonal line you could see the subsurface water change as the ground and grass were a lot less green. I put it down the the two foot deep trench (600mm) with 8mm gravel around the pipe acting like a subsurface drain. For you I would try and figure out which way the water is draining. BTW I live on a hill, not step but has a slope

You can see a white PVC pipe in the pic, is it stormwater or sewage?

Id be tempted to dig a bit of a shallow well/small pond and use that water for your garden an drain the too wet section of your yard at the same time. At the very least a well could be drained away as well.

One last suggestion as I had it happen to me in similar type soil. Check your water meter and if its ticking over when all the water in the house and yard is turned off. I had a crack in my water pipe for a couple of months without realising it (thinking of your subsoil being so damp) and also factoring in your pool. Do you have to top it up regulary?

Dave

Alan_

https://www.workshop.bunnings.com.au/discussion/comment/40641#Comment_40641

Thanks Dave, yes the PVC you see is stormwater, this was recently put in as the previous owners did not connect their downpipes and had roof water running into the soil. This has now been fixed, so I am confident their is no crack with these pipes. We have a slight slope on the land that travels from the front of the property to the back, it tends to collect near the edge of the pool. I'm glad to be on the right track with the french drain idea.

We don't have to top the pool up at all, so confident it isn't the pool leaking either, and checked the water meter recently, as I thought the same. No cracked pipes. I am told the land was a creek bed over 50 years ago, so will have a high water table. Not looking to solve the problem, just to improve beyond a mud pit 🙂

I'll take a few reference photos tomorrow too.

Thanks for the advise so far!

Alan

Nailbag

Hi @Alan_

The advice I was going to suggest is exactly the one in the link that @EricL provided. I’ve installed several of these systems to address the very same issues your facing.

It’s quite an easy DIY project albeit a physical one that doesn’t require any special tools. But either a landscaper or plumber will be able to perform the work if preferred.

Though often a landscaper does it, only a plumber is legally permitted to make the final connection to the properties storm water system. It’s important this is done correctly and no short cutting because it’s closer to cut in to the sewer which a plumber would never do.

MitchellMc

https://www.workshop.bunnings.com.au/discussion/comment/40644#Comment_40644

Hi @Alan_,

Adding drainage to the area should hopefully resolve this issue. My only other thought, if the situation is particularly bad and only in certain areas, is to remove 300mm of soil. You'd then add 100mm of drainage gravel over the entire area and then replace 200mm of soil back over the top. That would effectively disconnect the top 200mm of soil from the waterlogged soil beneath. Any surface water would seep through the topsoil and then drop through the gravel into the waterlogged soil.

Mitchell

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