We started to have this dug out for a pond and ran into cinder and stopped. We wanted the pond here because the water run off from the land goes right past it. It fills up during a heavy rain during the monsoons but drains out within a day or two. At first it drained overnight but due to the sediment slowly filling it back in over time, it has taken just a little bit longer now.
I also realize that the sides should be more of a gradual slope instead of straight up and down. I do not think I can fix the left side because the trees are right there but I can work on the other three sides if needed. We are also thinking of putting the ducks next to it so they can have a pond.
My research only came up with two options. The clay powder or a liner. We do not want to do pigs.
Anyway ... thoughts?
You might also want to build in a wide shallow shelf edge to the pond. That will help with the erosion to a point, though planting (or transplanting if you have elsewhere on your land) pond edge plants will also help in that regard. I've been reading up on natural pond building, and this image from an article on mother earth news shows what I mean:
Having the center much deeper even if only in part of the overall pond bed will also help retain water for the ducks.
Since your image shows an area with room for other land shaping, you might also want to consider roughing in a leadup area as the water naturally flows to your pond in either a rain garden sort of set up or dry creek bed where the rocks will buffer erosion some as well.
On the tree side, you might want to think about attempting a vernal pool. It would depend on the current natural water flow, but if it wouldn't take much effort to redirect it through the tree line, that might work. I don't know where you are, so it might not be good for your area. The article I linked might help you decide.
What would happen if you were to mix lime into the top few inches with a disk harrow and pack firm???
Be careful what you wish for you may get it!
Demand/give fair measure and longevity in all your dealings.
It's cheaper to go first class the first time rather than go second class the first time and first class the second time .John Ruskin???
You are probably using the wrong machine for the job. There is nothing wrong with using excavators or backhoes to dig out the bulk of the material, but ultimately you will want to use a bulldozer. That is because they not only smooth the sides with their wide blades, but that their tracks pack in the soil. This helps with side slope stability, and also locks the rocks and earth into place. The tracks on an excavator have 3 short grousers where as a bulldozer has one deep one. It will get your slopes really uniform and to the 2 to 1 slope you are probably looking for as well. That will go a long way to helping your pond hold water.
Bulldozers can be rented pretty cheap at around $450 per day not counting transportation. A small John Deere 450 will be all you will need (or equivalent), and should take a day to do what you want. Add in a second day if you have never operated one before. They are great little machines and perfect for slopes because with their low center of gravity, they are almost impossible to flop over: a very safe machine to operate.
IF that does not work, then you will have to bring in bentonite to seal it, but I think between the bulldozer and ducks, it will seal up so it will soon be holding water.
I fixed my pond with a product called dammit pond sealer. You broadcast it on the water. If you are gently filling it, you can broadcast it on the ground. It's the size of a grain of sugar and expands to about 80 times its size. The leak flow carries it down into the leaks and it expands.
I took a big risk with it, thought it was snake oil, but it worked. From dropping 6" a day to about 1" a week( likely evaporation).
My pond sunk to 1ft deep and was stable at that point. At this depth i could use a hand broadcast spreader to apply it. A box covers 1600 sq ft and costs just over $300 at amazon. After that application i added 2 ft of water and broadcast that perimeter of water. This method allowed shoreline application. Then i talked to mfgr and he said i could broadcast it on the ground. At that point i applied the rest of it and used my well to fill it. Its been full since.
You have to decide the permie factor of this. Like the OP, hogs was not an option for me. Ive had the pond for 3 or 4 years and there is a fish population. Draining to apply bentonite didnt seem like an option. Dumping bentonite in the water did not work (i bought a pallet of it. Total $ waste). Running a water hose to keep it full is not permie friendly either.
Bentonite is probably preferred while building a pond, since it has to mixed into the dirt, something you can't to with an established pond.
If you have a known leak, like a culvert through the dam and you can see the water seeping out at that area, you can remedy it cheaply by applying to that area only. If its unknown, then full application is needed.
Same stuff but different brand. Mine is shalex industries. The only reason i used it was convenience of one click buying at amazon. Both are made and shipped from australia. Buying direct and having to wait for shipping quote from different time zone.....
With shalex, i did have questions and received answers via email in a reasonable amount of time considering the time zone difference.
I just put "dammit pond sealer" in Amazon seach and it came up. $325 for the box that covers 1650 sq ft of surface area.