I recently bought a house with a small pond. Picture attached; I'm letting it drain while figuring out what repairs it needs.
* Eyeballing, it's about 30' diameter * 2-3 feet deep when full * Kept full year round by pumping from a well * Probably been here like this for 50 years * In California... it's hot, it never freezes, and it barely rains
It's right next to the house and as far as I can tell it's unlined. Not only does this require fairly continuous pumping in the summer, but water saturated ground has been causing the foundation to sink.
I've fixed the foundation and probably won't have further trouble, but I'd also like to do something to slow the water intrusion and reduce the pump rate. I'm thinking more along the lines of "reduce the leakage" rather than "make it watertight", but I'm not really sure what's possible or even a good idea.
My goal for the pond is just to have something pretty to look at, that grows reeds and frogs and dragonflies. No interest in fish and I want it to be as low maintenance as possible. I don't mind pumping water but I don't want to manage filters or chemistry or anything like that.
Should I try to mix some bentonite into the bottom? Or just put some overlapping plastic liner layers without worrying about sealing them too much? If I do seal it too well, do I need to worry about making a miniature Great Salt Lake with the summer evaporation?
First things first, carefully excavate a hole somewhere in the basin to get through the accumulated muck and check for a liner that already exists. You don’t want to add new holes so be careful. A small pond like that is likely to have a liner that has failed due to age, and hidden due to thick muck. What that will tell you is if the soil has any chance of sealing or not, and how much work it will be to restore or improve it as the old liner will need removal.
IMHO a pond this size and smaller requires a liner unless you have a very high water table or natural water source that never quits. A nice heavy duty felt protection layer and thick UV protected liner is a worthwhile investment, especially if you are filling in a dry climate area. It may pay for itself over time in water cost differences. Even in our normally wet climate I must top off our lined pond a few times a year due to evaporation. Ours is 20x18 before lining with rocks and plants.
If you decide to line it, and have some elevation to your advantage, install a bottom drain. I wish I had as cleaning it out is a chore without one. What is nice with a liner is it does allow a partial drain and clean out periodically. Natural liners are not nearly as easy.
There are a lot of resources for designing and building lined garden ponds. I find the hobby incredibly rewarding, as I did my project myself with the help of a neighbor’s excavator.
Best of luck and please keep us posted on what you choose to do!
I would do like liquidsquid said and check carefully for a liner. If no liner, I'd excavate to get all the existing "muck" out of the pond basin, and go 12" deeper. Get a 1 piece liner, install per mfg. recommendations and cover it with 12" of dirt that came from the last layer you removed. NOT the muck that you removed.
Pieces of liner that aren't glued together (sealed) won't work and you will be losing water. With that so close to the house, it is probably contributing to the foundation problem you had.
As for no fish. I'd rethink that and toss in some mosquito fish or fathead minnows to dine on any mosquito larvae. Mosquito fish will do a better job of that and they may be available free from the county vector control agency.
The dirt is needed to protect the liner from UV rays, and the dirt will be the growing medium for your plants. Frogs need it too - they burrow down and hibernate during the winter, no matter how short it is.
Thinking to the future, "making it watertight" will probably save you money in the long run looking at current utility prices vs. "reducing the leakage".
)
