A Step-by-Step Guide
Creating a small pond with bentonite clay adds a natural beauty to your landscape and attracts wildlife. Bentonite clay, when activated by water, forms a watertight seal, eliminating the need for a plastic liner. However, it’s important to understand the process and limitations before diving in.
Is Bentonite Clay Good for Ponds?
Yes, bentonite clay can be a good choice for a small pond. It’s natural, cost-effective for small areas, and self-healing to a certain extent. However, it requires more preparation than a liner and might not be suitable for all climates.
How Long Does Bentonite Clay Take to Seal a Pond?
Bentonite clay activates quickly upon contact with water. However, it can take several weeks or even months for the clay layer to fully cure and reach maximum effectiveness.
How Do You Use Bentonite Clay in a Pond?
Bentonite clay is applied as a dry powder directly to the bottom and sides of the excavated small pond. Water is then added to activate the clay and create a seal.
How Much Bentonite Clay Do I Add to My Small Pond?
The amount of bentonite clay needed depends on the size and depth of your pond. Generally, aim for a 1-2 inch layer of dry bentonite clay compacted over the entire bottom and sloped sides of the pond.
Step-by-Step Guide to Building a Small Bentonite Clay Pond
Here’s a step-by-step guide to building your small bentonite clay pond:
1. Plan Your Small Pond
- Size and Depth: For a small pond using bentonite clay, a depth of 2-3 feet is recommended. This depth allows for some water retention during dry periods and helps prevent complete freezing in colder climates. The size is up to you, but remember, a larger pond requires more clay and maintenance. Sketch your desired shape and dimensions on paper.
- Location: Choose a well-drained area that receives at least 6 hours of sunlight daily for healthy plant growth. Avoid placing the pond under large trees due to falling leaves and potential root problems. Consider underground utilities and call 811 before digging.
2. Call Before You Dig (Underground Utility Locating)
Before any excavation, it’s crucial to have underground utility lines marked to avoid accidents. Contact your local utility locating service, usually a free service, a few days before digging.
3. Excavation
- Mark the perimeter of your small pond according to your plan.
- Begin digging the pond, removing all vegetation, roots, and rocks. Aim for smooth and sloped sides, ideally with a 1:3 slope (1 unit vertical rise for every 3 units horizontal). This slope ensures stability and allows for easier planting later.
- Once you reach the desired depth, ensure the bottom is level.
4. Subsoil Preparation (Optional):
- Test your existing soil. Bentonite clay works best with a sandy loam or clay loam base. If your soil is very sandy or rocky, consider adding a thin layer (½ inch) of bentonite clay mixed with damp sand to the bottom of the small pond before proceeding. This creates a better bonding surface for the main clay layer.
5. Bentonite Clay Application
- Purchase bentonite clay specifically designed for pond lining. It’s often sold in granular form for easier application.
- Spread a 1-2 inch layer of dry bentonite clay evenly over the entire bottom of the pond.
- Work your way up the sides, maintaining the recommended slope and ensuring complete coverage. Overlap the clay at the edges for better sealing.
6. Compacting the Clay Layer
- This step is crucial for a successful seal.
- Rent a mechanical tamper or use a homemade substitute like a large, flat board attached to a heavy object.
- Systematically compact the clay layer from the bottom to the sides, ensuring even density throughout. Add more dry clay to any low spots that appear during compaction.
7. Adding Water (Initial Cure)
- Slowly start filling the small pond with water. The water will activate the bentonite clay, causing it to swell and form a seal.
- Monitor the water level and add more water as the clay absorbs it.
8. Checking for Leaks (Optional)
- Once the pond is almost full, you can perform a leak test (optional but recommended).
- Fill the pond completely and leave it for 24-48 hours.
- Monitor the water level. A significant drop might indicate leaks that need addressing.
9. Addressing Leaks (Optional)
- If you identify a leak, you can attempt to fix it by adding more dry bentonite and create a thicker layer.
- Add dry bentonite clay to the suspected leak location underwater. Use a weighted sock or dispenser to focus the clay on the leak. The water pressure will help activate and push the clay into the leak.
- Another option is to drain a portion of the water, expose the leak, and patch it with a slurry of bentonite clay mixed with water. Let the patch dry completely before refilling the pond.
- Add dry bentonite clay to the suspected leak location underwater. Use a weighted sock or dispenser to focus the clay on the leak. The water pressure will help activate and push the clay into the leak.
- Another option is to drain a portion of the water, expose the leak, and patch it with a slurry of bentonite clay mixed with water. Let the patch dry completely before refilling the pond.
10. Small Pond Curing Time
- Be patient! While bentonite clay activates quickly, it takes time to fully cure and reach maximum effectiveness. Allow several weeks, or even months in colder climates, for the clay layer to completely cure. During this time, monitor the water level and top it off as needed due to evaporation and potential minor leaks that may self-heal as the clay cures.
11. Edges and Liners (Optional)
- For a more finished look and additional security against leaks, you can add a liner to the top edges of the pond. Use a material like pond liner fabric or natural stone edging. Overlap the liner onto the bentonite clay layer for a secure connection.
12. Filling the Pond Completely
- Once the curing time is complete and you’re satisfied with the water level, fill the small pond completely.
13. Planting
- Adding aquatic plants is essential for a healthy pond ecosystem. Choose plants suitable for your climate and water depth. Submerged plants oxygenate the water, while marginal plants growing around the edges provide habitat and help control erosion.
14. Filtration (Optional)
- Depending on the size of your pond, fish stocking (if any), and desired level of maintenance, you might consider adding a filtration system. This helps maintain water quality and clarity.
15. Enjoy Your Pond!
- Sit back, relax, and enjoy the beauty and life your new small pond attracts. Remember, maintaining a healthy pond involves monitoring water quality, controlling algae growth, and managing any fish population.
Additional Tips:
- Bentonite clay can be messy to work with. Wear gloves, boots, and clothing you don’t mind getting dirty.
- Consider using a tarp or liner under the clay bags to minimize cleanup during application.
- Adding a layer of straw or landscaping fabric over the exposed bentonite clay after curing can help prevent wind and rain from eroding the clay layer.
- Bentonite clay ponds might not be suitable for areas with freezing temperatures and frequent freeze-thaw cycles. The freeze-thaw process can cause cracks in the clay layer.
By following these steps and considering the additional tips, you can build a beautiful and functional small pond using bentonite clay. Remember, patience is key during the curing process, and proper maintenance will ensure your pond thrives for years to come.
