A Bentonite Clay Pond Step-by-Step
Also known as Clay Puddling, this is how you make a natural pond without a liner.
Not only does bentonite enable you to create a beautifully natural-looking pond, it is inexpensive and relatively simple to use. No special skills are necessary, and it will take you only a few days to complete. If yours is a large pond, you would be advised to hire a compacting machine, otherwise tools are minimal. The secrets of success with a bentonite pond are to follow the guidelines carefully and to avoid working in wet weather. You will need at least three days of constant sunshine to complete this project.
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For an irregular, meter-deep (3 ft 3 in) pond 5 m x 4 m (15 ft 5 in x 13 ft 1 in):
200 kg (440 lb) bentonite or sodium clay
Step 1. Mark out the perimeter of your pond to get an idea of the outline you want. The shape does not have to be as precise as in some other methods and can be changed as you start excavation if you wish.
Step 2. First dig out the soil to the required depth, bearing in mind that quite a lot (200 mm/8 in) will be returned to the hole. Make sure that the walls of the pond do not slope more than 1:3. Dislodge and remove all vegetation, stones and tree stumps. You can take most of the soil away, although you will need to retain some to mix with the bentonite and to spread over the mixture once it has been compacted. There is no need to weigh the soil out, but you will need a total of 5 m³ (6½ cu yd), which is a hefty pile.
Step 3. Compact the floor area of the pond with a punner or with a compaction machine (plate compactor). Make sure the banks are also compacted thoroughly.
Here are a few bentonite/sodium clay items for you:
Step 4. Spread the bentonite powder evenly over the surface of the excavation. Each 40 kg (88 lb) bag should cover about 5 m² (6 sq yd)
Step 5. Now spread a layer of soil about 100 mm (4 in) thick over the blanket of bentonite. You can usually utilize the excavated soil for this purpose.
Step 6. Working systematically from one side of the pond to the other, thoroughly mix the bentonite and soil with a spade; or use a rake to combine the materials.
Step 7. Compact the walls and basin of the pond for the second time. Once again, you can use a homemade punner or a plate compactor machine.
Step 8. Spread a 100 mm (4 in) layer of soil over the compacted materials. This will act as a protective layer.
Step 9. Use a hose to sprinkle water over the prepared surface, and then compact well once again.
Step 10. Leave the pond for about 48 hours to allow the water to react with the bentonite. As the clay draws out the moisture, you will be able to see the top layer of soil drying out. This is essential if the sealing process is to be successful.
Step 11. Wet the surface again thoroughly, with a gentle spray of water, after the Step 10 two-day period and then leave overnight.
Step 12. The following day you can fill the pond. NOTE. Do this slowly, with a fine spray, to avoid damaging the sealed surface.