We have an old pond on the farm, behind our house. I would estimate it's 50x100 feet and 7-8 feet deep if it ever filled. The farm has been in our family since 1928, and when we acquired it in 2020 we had someone clean out the pond, and rebuild up the "dam" where it was washed out. I know that he re-cored the part of the dam that had washed out, but the other half I have no idea how it was made, and was left as is. From what I can see on Aerial Photos, the last time this pond really held water was the 1950's.
After the initial work was done on the pond, it tried filling over the winter (This pond gets very little runoff) but anytime it starts to fill it leaks back out. It seemed to me that it's leaked since day one, even when there was a small amount of water in it, but this also could have been a result of saturation. It never got more than 3 to 4 feet deep, except for after a big rain, when it probably leaked down a foot within a couple of days.
We had the guy come back and he cleaned it out again, dug it out deeper, and then lined it with a foot of clay. (Only tracked in with a D6 LGP for compaction, and he suggested a plate tamper would help provide some compaction, so we did that also.) It's leaked worse since this, and has probably only made it up to half the fill height it used to reach after a big rain.
We've had a really dry summer and it's only about a foot deep at this point, so I'm looking for options to try and make progress. We've discussed a liner or Bentonite, but I'm looking for any suggestions of alternatives to try first. I've considered running my disc harrow through it and then trying to get better compaction with my tractor (approx. 9000lbs). If we added Bentonite, my idea was to add it between the disc harrow and compaction steps, but I'm not sure on an application rate. Could this be done on just the lower section of the pond to see if any improvements are made, or should it all be done at once? I've also considered letting the cattle in it when we get them up to our farm next spring.
Does anybody have any low cost ideas that are worth a try before spending a bunch more money on it? I can have the pond completely dry within a couple days with a garden hose. I've seen the stuff that you spread over the water and it supposedly suspends itself and gets sucked down into the leaks. Is this worth a try if the pond ever fills back up again, or a waste of 500 dollars?
I've attached the only picture I have of recently, where you can see our "hole in the ground" pond. Thank you for any ideas!
With regards to Bentonite application rate, Natural Waterscapes suggests "The application rate for bentonite ranges from 2 pounds to more than 6 pounds per square foot depending on the soil characteristics." If you have some decent clay it will be on the lower end. 5000sf would require 1,000 to 3,000 lbs by their recommendation to do the whole pond. A 2,000 lb supper sack costs $1,1175 from them. You may find it cheaper but gives you an idea of what it would cost from one supplier.
I chose to mix it 3:1 with decent clay and spot treat my pond with a 1-2' compacted layer where it appeared we were making connection to the water table. If you do have a water-table pond then you might be able to find where some of the water enters and exits. These are hard to plug but I'm sure M. Otto and M Gray have written about it in PondBoss Magazine.
An alternative is to use a polymer sealant like Soilfloc, but I think this only works if water is only flowing out, not in.
Good luck, and some of the folks that do this for a living might chime in.
I help folks nationwide with Pond Construction, rehab, and leak abatement, and I’m happy to share my insights if you’d like to chat sometime. Feel free to reach out, glad to help any of my Pondboss family with leak issues.
