For safety reasons (we have a 17 month old son) we decided to get rid of our koi pond. It is roughly 11' x 4' x 5' deep.

I drained the water. Cut away all the lining. And found a layer of sand underneath. The walls are made of wood. I thought that the remaining inch or so of water that I cant pump out would gradually drain out. In the past few days we had rain and the remnants of the pond filled with roughly 12 inches of water. I have pumped that out too and am ready to fill it with stone and then top soil.

I am worried that this will become very soggy/water logged if it rains again because the water doesnt seem to want to drain. I would guess that the soil beneath the empty pond is likely a clay mixture, much like the rest of the yard.

What should I do?

@RpR

Rent a post hole digger, make a few holes, see what happens?
Hope RpR has info about possibilities.

Sharon - I would be tempted to take advantage of this poor drainage and make a sort of bog garden there. Just off the top of my head I would fill a lot of it with a stony/rocky fill topped with something to stop dirt just filtering down; add dirt then plant water-loving irises etc. If you make it a dense planting any falls in to this garden will be 'cushioned' and water won't gather either. Remember - just off the top of my head so details need refining

Actually Val's idea sounds nice, but did it ever over flow when the Koi were still in it.

Find out what is under neath the sand, take a steel rod, of some sort, and hammer it in the bottom of the pond.
If it goes in , then, a post hole digger to make severl drainage holes to totally drian it is the best idea.

It looks that whom ever made it did a good job, which means the soil under the pond was probably compacted so there would be no drainage if the liner was punctured some how.
It is a good idea of what is under the bottom sand before you start filling it in.

Remember RpR - the pool had a liner so while it was in place too much rain might well have caused it to overflow; can't tell what the surround is composed of though.

I would remove as much of the sand, frame and anything else that can be removed. Then find some soil that is as close to your native soil as possible and fill it in. Then plant what you want.

Judging by the size and depth of that koi pool you might find that a very expensive option and removing the sand, which I suspect is only inches deep to cushion the liner, would make the volume to be filled even greater

Thank you, everyone, for your input and suggestions! This is such a lovely community! I started to pour the rocks in but then saw some suggestions to dig first...

@RpR - I dug two feet down into the bottom. There was a bit of sand/silt. And then just normal dirt/clay mix, which is normal in my yard/area of CT. I also took a very long drill bit (3 feet) and it went straight down with no problem. So I think that you are right - the bottom is just very compact.

I will fill it with stone tomorrow. Put a layer of weed barrier. And then fill to top with top soil. Then I will hope for the best! If it is soggy, I will follow @Vals_Garden 's suggestion of using Iris' or something of the sort. I'll update with photos when complete!

It would drain better if it was filled with the same soil as what's around it. You have created a perched water table. Water won't go into the rock/gravel until the soil above is saturated and won't go into whatever is below until the rock/gravel is saturated. Talk about poor drainage!

CalPolygardener said: It would drain better if it was filled with the same soil as what's around it. You have created a perched water table. Water won't go into the rock/gravel until the soil above is saturated and won't go into whatever is below until the rock/gravel is saturated. Talk about poor drainage!

If she is filling it with clean rock, not gravel, it will drain well.

I have put in dry wells, which are holes in the ground , x feet deep, filled class 2 or 5 crushed granite that drain quickly, often put where a down spout ends.
Assuming the hole she made drains (some clay soils, especially if it is fill for building DO NOT DRAIN well. We used to replace a lot of trees planted in clay fill that did not drain. So we had to post hole drill till it was pierced ) but if the hole she dug when filled with water drains at an accepted rate, the water will filter through the rocks to the base quickly.

IF it does not drain a wet garden will look nice.

I wouldn't bother trying to fill it with your native soil. Judging from the rest of your yard, you are not lacking for planting spaces with native soil. People spend hundreds or thousands of dollars to create a specialized bog garden; you already have one! Take advantage of it. Plant it full of Louisiana irises, which love growing in soggy soil. It will be gorgeous! There are also many other types of interesting bog plants if you want a mixture. Browse places online that sell pond plants to see what is available. I am so jealous that you have this. I can't believe you're trying to get rid of it.

fiddler said: People spend hundreds or thousands of dollars to create a specialized bog garden; you already have one! Take advantage of it.
I am so jealous that you have this. I can't believe you're trying to get rid of it.

@stone seems to me I don't have a choice! Bog garden it is. I was never going to be able to remove all the framing of the old koi pond nor add enough of the same soil as the rest of the property to fill this big space. I filled the bottom with crushed stone, then a layer of as much clay soil that my yard could spare (maybe 1 foot), then top soil. After a lot of rain and snow recently, it is clear that this will remain wetter than the rest of the gardens.

I'd love to hear anyone's suggestions of what to plant here besides iris, which I will do too.

Thanks, everyone. Ill update once the freezing weather stops and I start to plant.

Since you have a child, my first suggestion would be a bug-eating plant. This one is rated hardy in your zone,
Purple Pitcherplant (Sarracenia purpurea)

They do require some special care, though.
https://www.plantdelights.com/...

When the child is older & knows not to eat random plants, you might try Lobelia cardinalis. It's beautiful and attracts the hummingbirds. (Lobelia does contain toxins so it's probably wise to wait to plant this one.)


Do you have a height limit you'd prefer for the plants?

Danita said: Since you have a child, my first suggestion would be a bug-eating plant. This one is rated hardy in your zone,
Purple Pitcherplant (Sarracenia purpurea) I had to damage the links in order to post since I'm still a new member.

They do require some special care, though.
[url=ttps://www.plantdelights.com/blogs/articles/carnivorous-pitcher-plant-nursery-sarracenia]ttps://www.plantdelights.com/b...[/url]

When the child is older & knows not to eat random plants, you might try Lobelia cardinalis. It's beautiful and attracts the hummingbirds. (Lobelia does contain toxins so it's probably wise to wait to plant this one.)

• Cardinal Flower (Lobelia cardinalis)
• Uploaded by molanic

Do you have a height limit you'd prefer for the plants?

Carnivorous plants need very low mineral soil as in 100% sphagnum peat moss or 50/50 Sphagnum/perlite. If you were going to make a CP bog you should have left the liner in place because you don't want your ground water getting into your bog.

Edit: On second thought, if you make a CP bog it does not need to be much deeper than 2 feet. You could still use your old liner if you didn't puncture it or throw it out yet.

Here's a Purple Pitcher blooming on May 28, 2020, the flowers are almost open. Maybe one more day. You can see some of the pitchers are brown at the top. That is normal winter damage and the plant will replace those pitchers by the fall.


Here is another S. purpurea on Oct 31, 2020