Restoring an unused bentonite liner

[Gilbert Fritz]

A large pond, maybe twenty feet across, was dug a good many years ago with heavy excavating equipment. Then five thousand pounds of bentonite were spread across it. That was as far as work got, and now, twenty years later, the pond is a depression covered by a healthy growth of weeds and grass.

How should I proceed to rehabilitate this? What is the first step? I imagine that the weeds have compromised the liner. If I puled out the weeds, raked the ground flat, and packed it down, would it become usable again? The underlying soil is clayey.

 

[tbendl]

I'm unfamiliar with bentonite but it sounds like it's a clay. If it's a hard clay that you can dig down to, I would clear all of the dirt and weeds and accumulation of years of muck. Does it hold water now?

 

[mariobrothersleeve]

Yes, bentonite is drilling mudd, fetches a high price for down hole drillers. No roots will pass through this liner, unless it's trees. If it's a silt fence, yes the roots would. Do you know why they used clay?

 

[Gilbert Fritz]

I figure that the price for an EPDM liner at this size would have been cost prohibitive. The plants appear to be mostly grass, and they certainly seem to be growing into the clay. I was wondering if all those roots will have created channels through it. I don't think the pond was ever filled: various events halted construction.

 

[tbendl]

I would think that you have to pull everything out and start with a blank slate. Do you have any pictures that you could post to give us a better idea of what you're dealing with. And when it rains now does it hold water?

 

[dieselplower]

Hi Gilbert. I saw your comment about this thread in your introductions post and wanted to come check it out to see if I could help. Sadly, I have no idea Good luck!

 

[RobAmy]

I have no idea either, I used a rubber liner. But I am intrigued on this issue. Very natural design. I would assume pull out the weeds and growth you do not want, if it holds water now then the base should be fine. Seeing it is a clay bottom, plant matter will always grow in it. However this is just a guess. Good luck and will love to see and hear the follow up on this.

 

[HARO]

Try to contact a local agricultural agency, they should be able to help. Farm ponds are often lined by this method.
John

 

[Gilbert Fritz]

A little bit more of an update: I went out in a pouring rain today, and there was no water in the pond at all. The nearby creek was in flood, even. And there is a really thick growth of weeds in the pond, including some bushes, so the clay liner must be shot. I will start digging out the vegetation, since I can hardly make things worse then they are.

 

[tbendl]

Good luck. At least you have most of the hole dug for you should you decide to put a liner in.

 

[dieselplower]

im going to make a comment and I want you to consider it a possibility and not a fact. After 20 years, quite a bit of dirt has probably blown into the pond. Leaves have probably fallen into it and decomposed as well. Plants have grown and died in there as well. It is possible that this has formed a thick layer of "soil" on the bottom on top of the bentonite and that is what the grass, bushes, weeds etc are growing in. If that was true, it is also possible that the rain water is soaking into the soil on top of the bentonite, so you wont see it. Maybe you can remove the top layer of debris and there will still be a good layer of bentonite underneath.

 

[Gilbert Fritz]

Hello dieselplower,

You might be right. I will find out when I start digging. My plan is to leave all the current soil in place, while carefully removing the plants. Whatever happened afterward, I am assuming that the bentonite cracked in the first summer. In some on line research, I found that if the pond level drops and the clay on the sides dries out, it will crack, and these cracks will not necessarily reseal themselves when the water level raises again, leading to a leak.

However, I did walk into the bottom of the pond yesterday, during the rain storm. I would have expected that there would have been at least a boggy or quicksand feeling if you were right, but there was not. And that was a lot of rain. We will see.

 

[dieselplower]

Makes sense about the cracks...

 

[steve/gridnot]

Hi Gilbert,
I was working on cleaning one of my older ponds and thought I might put a hole in it while cleaning. I bought a 14.5 liner from Pond Skin just in case. These are carried by Home Depot 13'X20',which is the largest one they keep in stock. They put them on sale for $100 at the end of the season. Since my pond cleaned up well without leaking I am about to use the liner and make another pond. These liners work very well and if you make your pond a little smaller might make an easy alternative and use the base you already have underneath? I have done bentonite before and unless it is available at a good price it can be very tricky. Sealing leaks with 50lb. sacks of bird seed is not always a good cure,LOL. Once something has put roots through it you are starting over.
I am putting this new one on a hill, which will allow me to install a window. If you want a window on a flat pond you just need another hole and some steel culvert. Interested?

 

[MitchM]

20 feet across is not all that big.
It might be a lot less headache if you were to hire a local contractor with a small excavator to dig it out and start over.
Depends on how much time and ambition you have.

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