Sealing A Pond With Bentonite – A Complete Guide

Sealing a pond with bentonite is the most effective method to make the pond retain water. Sodium Bentonite clay is used for this purpose. In this article, you will learn how to seal a pond with bentonite by three methods.

The methods of fix a leaking pond with bentonite are as follows-

1. Sprinkle Method
2. Blanket Method
3. Mix Blanket Method

Method 1: Sprinkle Method

The Sprinkle method is simple to perform. You have to sprinkle the bentonite to the leakage area by a broadcast spreader or by hand. This method is less effective than the other two methods of sealing pond with bentonites. This is because it’s not possible to place the bentonites evenly to the bottom of the pond when you are spreading them from the top of the water.

When to Adopt This Method

• There is no way you can drain the pond.
• Draining the pond isn’t feasible.
• Leaks are isolated from each other.
• The leaks needed to be fixed quickly.

Which Bentonite to Use?

For sprinkle method, you have to use the granular bentonite. Bentonite particles are very fine. If you sprinkle them, they will float on the pond surface and will not reach the bottom of the pond. On the other hand, granular bentonite is large and it will sink to the pond bottom. Therefore, you have to use the granular bentonite for the proper sealing of the leakage.

How Much Bentonite Will You Need?

The application rate for the sprinkling method is higher than the following two methods. For proper sealing of the pond bottom, you have to apply almost 5 pounds of granular bentonite for every square foot.

How to Apply

Step: 1

In sprinkle method, your first task is to clear the pond bottom. Remove any debris such as trash, leaves, rocks, pondweeds, etc.

Step: 2

After that you have removed all the debris and identified the leaks, your final job is to sprinkle the granular bentonites evenly in the leakage areas. The particles will reach the pore and swell to fix the leak.

If you can identify the more porous areas, apply bentonite to these areas first. It can reduce seepage to a great extent so that you may to need to apply it to the whole pond.

Cautions

• Bentonite particles are very fine. When you apply them to the pond, you may inhale some with air. Therefore, use a face mask to prevent them from reaching your lungs.
• Don’t carry out this method if the weather is too hot.
• If there are excess leaks and it requires you to apply a large amount of bentonite, do the job in the course of several days of interval. And not never if possible.
• Using bentonite in the sprinkle method to seal a pond can cause cloudiness in pond water. This is not permanent and the water will be fully clear within several days. As bentonite isn’t toxic, you can use the water for any purpose.

Method 2: Blanket Method

The blanket method is the most effective method of sealing a pond with bentonite. You can adopt this method for both newly excavated and old ponds.

When to Adopt This Method

• The soil of the pond bottom is highly porous and the permeability rate is high.
• Livestock has access to the pond.

Which Bentonite to Use

For the blanket method, you will need fine or powdered form bentonite.

How to Apply

Step: 1

If you have an old pond with water, first drain the water from the pond. Collect all the debris from the pond bottom.

Step: 2

Let the pond dry until the soil reaches the optimum moisture content. The optimum moisture content of the soil is necessary for maximum compaction.

Step: 3

Divide the pond bottom in a number of plots. You can take any area from 100 square feet to 200 square feet.

Step: 4

Remove the topsoil and gather them in a place. If livestock doesn’t have excess to the pond, remove 5 to 6 inches of topsoil. But if the pond is accessible to livestock, remove at least 8 inches of topsoil although 10 inches is recommended.

Step: 5

Find any holes and fix them with five parts of soil and one part of bentonite.

Step: 6

Prepare the bottom surface of the pond by smoothing it with a roller. This will also compact the soil to some extent which will reduce the porosity of the soil and help it to retain water.

Step: 7

The next task is to spread the bentonite clay in the area. Be sure that you spread them evenly and there is no thin layer. This is very important for an effective seal.

Step: 8

Now spread the soil that you have gathered in step 4 over the bentonite layer. Be sure you don’t disturb the bentonite layer while spreading the soil.

Step: 9

The final task is the compact the soil. Use a roller or temping plate for this job.

After you have completed all the tasks, you can wait some days to swell the bentonite clay. Again if you are in a hurry, you can fill the pond with water just after completing these 9 steps.

When you add water in the pond after bentonite treatment, make sure the flow is gentle. Because a turbulent flow can disturb the layer of bentonite and seepage can occur in these places.

Cautions

• Remove all the debris from the pond before you start the job.
• Be sure you take small plots to fo this job.
• Leave no blank space.
• Carefully add the water so that you don’t disturb the bentonite layer.
• Maintain a good depth of soil layer.
• Have good compaction by achieving an optimum moisture content of the soil.

Also Read: Sealing a pond with lime

Method 3: Mix Blanket Method

The mix blanket method is almost similar to the blanket method. The only difference is here a layer of bentonite and soil mix is used instead of a pure bentonite layer.

How to Apply

Step 1:

Strain the pond if it has water and cleans all the debris from the pond bottom.

Step 2:

Let it be dry to reach optimum moisture content.

Step 3:

If you find any hole patch them with 1:5 bentonite and soil mix.

Step 4:

When the soil has reached the optimum moisture content, plow it at a depth of 6 inches if the porosity is less. Again if the porosity is more, you have to plow it up to 12 inches.

Step 5:

Apply the recommended amount of bentonite to the soil. Use a broadcast spreader for this job to get an even spreading of bentonite.

Step 6:

Now mix bentonite and soil altogether by discing and tilting. You can use a rake for this job if the pond is small. But if the pond is large, then you can plow it again to have a good mixing. Have multiple cross-passes when you plow the pond so that you get the maximum mixing and leave no bare spot.

Step: 7

Finally compact the soil and bentonite mix with a roller. You can use a large mechanical roller for this job if the pond is large. Again for a small pond, this job can be done with a small lawn roller.

Cautions

• Maintain good depth if livestock has access tot he pond.
• Leave no bare space.
• Use the recommended amount of bentonite.
• Thoroughly mix soil and bentonite together.
• Gain maximum achievable compaction.
• When you add water, make sure you don’t disturb the bentonite-soil layer.

FAQ’s (Frequently Asked Questions)

How much bentonite is needed to seal a pond?

The amount of bentonite required to seal a pond depends on the porosity of pond soil. Because high seepage of water occurs if the porosity is more. Texas Bentonite recommends you use it in the following amount depending upon the type of soil of your pond –

• Clay Soil: 1.0 to 1.5 lbs per sqft
• Sandy Silt: 20% Clay Min 2.0 to 2.5 lbs per sqft
• Silty Sand: 3.0 to 3.5 lbs per sqft
• Clean Sand: 4.0 to 4.5 lbs per sqft
• Rock Or Gravel: 5.0 to 6.0 lbs per sqft

How much bentonite do I need for a 1-acre pond?

It depends on the soil type of your pond. As you know 43560 Square feet make an acre. For example, if you have clay soil in you will need 4356 lbs of bentonite. But if you have gravel or rock in the pond bottom, then you will need 5 times more of clay soil

Is bentonite harmful to fish?

Bentonite is a natural substance. It is nontoxic to fish. But as the particles are fine if the concentration is high in water it can attach to the fish gills. This can reduce the oxygen absorbing capacity of the gills and fish may die due to the lack of oxygen.

How much does bentonite cost?

According to Statistica, the average price of bentonite is $77 per ton when this content was written. This price is applicable when you buy them directly from the manufacturing factory. But the cost will increase if you buy them in a small amount. The average price of a 50 lb bentonite bag is about $85

What is bentonite waterproofing?

Bentonite is a clay. When it is exposed to water, it absorbs water and expands. In the leaks, it expands by absorbing water and thus fills leaks to make it waterproof.