I am building 2 small ponds to hold excess water, we are planning to use bentonite clay with the intention of sealing the pond 70-80% with some seepage to benefit the surrounding vegetation.
The soil is mostly sandy loam, a tiny bit of clay, but very permeable, and the sides quickly erode and change shape when the water pours in.
One of the ponds is 3m in diameter, and the other is a bit more oval (4 meters long, 2 meters wide), but we do not have access to any heavy rollers and want to use the clay to line the ponds by hand. Any advice (regarding the shape of the ponds and the application method)?
You will need to rent a rototiller to mix the bentonite with the soil, then use a hand tamper to compact as much of the soil as possible. Here you can also rent a small mechanical vibrating compactor that is about 1/2 meter square that is used to compact sand before placing bricks on top of it for a walkway.
We used a similar rented compactor to prepare a manure storage area. It was gasoline powered and about the size of a push lawn mower. The handle flipped back and forth when you changed the direction you were moving it.
"Live like you'll die tomorrow, but manage your grass like you'll live forever." -S. M. Stirling
Here are some images of the pond we build. It is 4 meters in diameter, and 1.5m deep in the center.
A few questions.
1. The owner of the property has given us 370kg of bentonite clay to line the pond - is it enough so that it will hold water for at least a week? We can refill it from the aquaduct every Monday.
2. The walls are steep, so applying the clay with a rototiller doesn't seem feasible. What would be an easy and practical way to do the application? Are the stones that we have placed to prevent erosion from entering water going to be a problem in the lining of the pond with clay?
3. Will it be possible to grow aquatic plants even with large amounts of bentonite clay?
4. The bottom berm is a bit high but matches the level of the back wall and is 20cm above the overflow -- is this necessary?
5. What might you expect to as maintenance for a pond like this?