Forge

[jayco]

My neighbor is using bag after bag of bentonite clay .......trying to seal seeps and leaks in his new farm pond. I have no idea whether that works or not, but he's getting it from a local "Southern States" dealer. (a farm supply store).
James

[Frosty]

As said, cheap kitty litter is bentonite clay. Look in the yellow pages for a drilling company, even if they do water wells they'll be able to put you in touch with a supplier or drilling company that can.

How's the neighbor applying the bentonite to his pond James? It makes a difference.

Frosty

[jayco]

Frosty......he's pouring the clay on the inside of his pond.....trying to seal seeps from the inside. If it ever rains here,(we're in a drought), I guess we'll see if it works!
James

[Frosty]

I figured he was pouring it in the pond but there're different ways to do it.

If he knows where the leaks are putting it where pond water can carry it in will work well. Another method is to mix it by the drum about the consistency of thick gravy and using an outboard motor to get the pond circulating in a vortex slowly add the mix. Add it right after mixing as bentonite will continue to absorb water for . . .ever actually. Anyway, you want it to enter any leaks while it's still in it's major absorbtion phase.

It sounds though like he's applying it to a dry pond. This can be both good and bad.

Bad because the only way to be sure is to apply it to the whole pond and maybe use more than you need to.

Good because you can apply it dry and take advantage of it's maximum absorbtion and expansion to seal EVERYTHING.

If the pond sides are reasonably shallow spread it and rototill it in for at least 6", 1' is better, then hit it with a plate compactor. Do this dry first, then put a sprinkler on it and recompact it when dampened. The pond may still leak the first time or two it fills but the bentonite WILL expand into any void and plug it solid.

I'm not an expert but as I recall sandy soils will seal with as little as 3-5% bentonite and if it takes much more than 10-12% he needs to consider finer material in the sides.

Frosty

[jayco]

Frosty....he has about a foot of water in the pond. A bull dozer and a track hoe were both used to dig the pond.One side,(the leaky side),was raised and filled.....and packed as best they could. My neighbor spreads the bentonite on the inside of the wall........some in the water itself......the rest on the dry bank. He waters the clay in with a garden hose. I never knew about the unique properties of bentonite before now!
Thanks Frosty!!

[Frosty]

Just spreading it on the surface isn't going to work, it needs to get into the voids and expand. Using an excavator would make mixing it with the fill easier and then he can compact it with the bucket. The downside is using more bentonite than he probably needs to but that's okay as long as it isn't too excessive. More is NOT better.

He doesn't want a lense of solid bentonite, it makes a REALLY good lubricant when saturated and if there's water present it WILL saturate to and beyond it's liquid limit. Once it's hit it's liquid limit it will flow downhill, even a really shallow slope. this is bad for any structure. So, it's important to use the bentonite as an expanding filler to plug the voids. Expanding is also a key factor to think about because it WILL expand as it absorbs water, so like ice it will lift and shift things sitting on it.

Normally, well graded soils have plenty of fines to fill all the voids and when compacted will be water tight. So, a lot depends on what his soil gradation is, if it's all 1"+ gravel all the bentonite in the world isn't going to do it. If that were the case, adding sand and 3/4"- to the bentonite before mixing it with his fill would be a good idea.

If his soil is all sand cement stabalization may be a better way to go but NOT after dumping a bunch of bentonite on it.

Anyway, there're all kinds of ways to make his pond hold water. With a little more info I can maybe make some better suggestions.

Frosty

[jayco]

Frosty...I haven't been able to talk to my neighbor these past few days to find out exactly how he applied the bentonite, but I know he only used a small tiller and hand tools to mix with. I observed that much. We have predominately clay soils around here anyway. I think his pond would have started holding water in a few months even without the bentonite. Most of the farmers here have ponds that hold water. They never used any bentonite. Probably why I had not heard of it being used for stopping leaks.
With autumn coming on soon here, my new neighbor wanted to hurry up the process, I'm sure.
James

[Frosty]

If it's clayey (that's such an awkward word<grin>) soil it'll stop leaking shortly. That's all bentonite is though it has some unique properties. Plain old clay is going to swell and seal itself off after a while.

Frosty

[jayco]

Well, it took me long enough I reckon, but I finally got around to posting a pic of the now finished pond my neighbor had built........or is that 'dug'?
Anyway, he has a nice 75 ft. x 200 ft. pond with many bags of bentonite on the inside of the banks.

A combination of time and the bentonite cured his leakage problems.

At one point, last fall, during the dry season here, he had devised a plan to put himself and some bags of bentonite in a small row boat and have two volunteers pull him and the boat, (erie canal style) back and forth across the leaking areas of the pond with ropes so that he could pour the bentonite in 'just the right places'.

It's truly a pity he could not find those volunteers.........I would have liked to have been there and watched.........and maybe snapped a few pictures.

[KevinD]

Cool pond. Now he needs to add lots of lime to get a neutral pH and all that brown will go away.