Anybody know to "seal" a dirt pond?

   / Anybody know to "seal" a dirt pond? #1  


Elite Member
Apr 21, 2012
Cascade Mtns of WA state
Kubota B-series & Mini Excavator
I dug a small pond a couple days ago, and re-routed a tiny creek to fill it. It's about 5 feet from the original creek location. The creek is just a trickle, about the size of my finger. The pond is about 7 feet circle 2 feet deep.

In the first six hours it filled about a foot deep and then stopped. So I stuck the bucket in there and churned it into soup, which sealed it somewhat and it filled further. Today it's almost full, but stopped again. So I dug mud out of the bottom and poured it down the sides. And it filled another 2 inches over the whole day. It has just now reached the spillway but won't spill any water.

If it can't spill any water in March, it's not going to be much of a pond in the summer. Water is leaking out at the same rate it's coming in. Does anybody have tricks to make it hold water? Or do I just have to wait?



That's my 15 yo girl running the Mini-Ex, her first 20 minutes!


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   / Anybody know to "seal" a dirt pond? #2  
An old farmers trick of years ago was to spread Portland cement (out of the bag) across the top of the pond and let it sink. Seals up hole. Off topic but to drain a swamp or lowland they would row out find the deepest spot and pour in a couple of pounds of mercury. The mercury would work itself down thru the soft mud and drain the swampy area. Im sure that would be a big no no these days.
   / Anybody know to "seal" a dirt pond? #4  
Second the bentonite plan, once and done.
   / Anybody know to "seal" a dirt pond? #5  
Bentonite is what I would use. If you can go to a well drilling co. ask for hole plug. It is the clay in a tablet form. You could seed it with out draining the water. I have used it on a brick side walk where the rain would seep through and wash the fill out from behind the steps that I had built out of 6x6s. I gave the rest of the bag to someone who used it to seal around the standpipe in his pond. Don't over use it because it swell up. You could dump 50# in your pond and by the time it swells your pond would be full of mud. If there are any well drillers reading I'm sure they can tell you exactly how much to use.
   / Anybody know to "seal" a dirt pond? #6  
The old timers used to fence the pond and put some pigs in and let them root. They said that it works.
   / Anybody know to "seal" a dirt pond? #7  
Bentonite, Dolomite, or have a cow walk around in it to pack it.
   / Anybody know to "seal" a dirt pond? #8  
Bentonite works well when I have seen it used (for all sorts of things, like grouting wells or geothermal installations). But for a 7' wide 2' deep pond, you can also just buy a roll of black pond liner and install it. That's about the size of water features landscapers put in, and they all use liner. Doesn't seem that expensive, as I knew someone who bought it for other uses. Only downside in this case is that you'd have to drain the pond and divert or deal with the inflow trickle while installing, and that could be a hassle.
   / Anybody know to "seal" a dirt pond?
  • Thread Starter
Bentonite sounds like the way to go! THANKS! I cannot drain the pond easily (maybe siphon). Do you think I can make a slurry of it and (try to) pour down the sides? Or should I make a bentonite slurry in the pond with the excavator bucket? Will it settle out (thus remain in the pond)?

from Wikipedia:
Groundwater barrier[edit]
The property of swelling on contact with water makes sodium bentonite useful as a sealant, since it provides a self-sealing, low permeability barrier. It is used to line the base of landfills to prevent migration of leachate, for quarantining metal pollutants of groundwater, and for the sealing of subsurface disposal systems for spent nuclear fuel.[9] Similar uses include making slurry walls, waterproofing of below-grade walls, and forming other impermeable barriers, e.g., to seal off the annulus of a water well, to plug old wells.

Bentonite can also be "sandwiched" between synthetic materials to create geo-synthetic clay liners (GCL) for the aforementioned purposes. This technique allows for more convenient transport and installation, and it greatly reduces the volume of bentonite required.

It is also used to form a barrier around newly planted trees to constrain root growth so as to prevent damage to nearby pipes, footpaths and other infrastructure. Farmers use bentonite to seal retention ponds.

Wikipedia is the greatest but it never occurred to me to search it!

I thought about black plastic but didn't want to deal with hiding the edges, and the plastic has to be as high as the spillway, all the way around. It really seems like a lot more work,,,,. Want it to appear natural ASAP, the reason for this pond is entirely aesthetic, also for my daughter to feel like she "created something" every time we go past it.
   / Anybody know to "seal" a dirt pond? #10  
See if you can find hole plug. You probably will not have to drain it.