Seminole Mud Co., Inc.
12160 NS 3610  |  Seminole, OK  74868 |  405-382-1973

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Sealing Ponds With Bentonite
Sodium Bentonite as Pond Leak Sealer
for Newly Constructed Ponds or Dry Ponds

When sealing a pond to prevent  water loss through seepage, bentonite can be applied directly to the soil in the pond bottom, or it can be sprinkled on the surface of the water and allowed to settle to the bottom.  There are three basic methods: the blanket method, the mixed blanket method, and the sprinkle method.  These methods are discussed below.


BLANKET METHOD (Labor Intensive)

The blanket method is usually the most effective method for sealing ponds.  However, more care is required during it's application.  The grade of bentonite, "Pond Seal," is best suited for this method.

The first step is to prepare the surface to be sealed.  Remove all rocks, trash and vegetation, including trees and roots.  Roots left in the ground will decay over time, leaving the potential for future leakage problems.  Remove the top 4 to 6 inches of the soil from the pond bottom.  Fill any deep holes or crevices with a uniform mixture of one part bentonite to five parts soil.  Then smooth the area by roller or drag.

Cover the area with the prescribed amount of sodium bentonite.  We recommend a grade of Bentonite, "Pond Seal," for this application.  It is very important that the bentonite layer is even and that there are no bare or thin spots.  This will ensure complete coverage and a water tight seal.  After the bentonite has been spread as evenly as possible, carefully replace the 4 to 6 inches of soil that was removed earlier.  While spreading the soil, be certain not to disturb the bentonite layer, as this could leave bare spots which could allow the water loss to continue.  If livestock will have access to the pond, the cover coat must be more than 4 inches, perhaps 8 to 10 inches.

Finally, compact the pond bottom by rolling or tamping.  Use care when filling the pond.  A gentle water flow is recommended to prevent erosion of the soil and bentonite layers during this final phase.  It may take several days for the bentonite to reach the point of full saturation and fill the voids in the underlying soil.

MIXED BLANKET METHOD (Most Commonly Used)

Begin by preparing the surface to be sealed.  Remove rocks, trash and vegetation, including trees and roots.  Roots left in the ground will decay over time, which leaves the potential for future leakage problems.  Plow, disc or till the bottom of the pond 4 to 8 inches deep, then roll or drag the surface until it is smooth.  This initial plowing and blending of the soil will assure consistency of the soil throughout the bottom of the pond before the bentonite is mixed into it.  When this is complete, apply the prescribed amount of sodium bentonite.  We recommend a grade of Sodium Bentonite, "Pond Seal," for this application.

The bentonite can be spread by several different methods, however, we recommend a fertilizer or seed spreader to ensure even spreading.  Mix the bentonite with the top 3 to 6 inches of soil by discing, tilling or by hand raking.  It is extremely important for the bentonite to be mixed uniformly with the soil.  To insure that no bare or thin spots will be left, we recommend multiple passes over the area.  If livestock will have access to the pond, a cover coat of 4 inches is advisable.

Finally, compact the pond bottom by rolling or tamping.  Use care when filling the pond.  A gentle water flow is recommended to prevent erosion of the soil/bentonite layer during this final phase.  It may take several days for the bentonite to reach the full saturation and fill the voids in the soil.

SPRINKLE METHOD

The sprinkle method is recommended only when it is not feasible to drain the existing pond or in cases of isolated leaks when a spot treatment may be a possible alternative.  This method is less effective than the other methods mentioned above for several reasons:  Uniform and accurate placement of the bentonite soil is difficult; The pond bottom may include debris such as trash, vegetation, logs, rocks, etc., which may prevent sufficient coverage.  If the bottom of the pond can be cleared, this method has greater chances of providing a good seal.

The granular grade of bentonite, "Granular Seal," is best suited for this method of placement.  The granular bentonite should be used when using the sprinkle method because the particles are large enough to sink to the bottom, while finer particles cloud the water and stay in suspension.  Begin by simply sprinkling the prescribed amount of granular bentonite (Granular Seal) on the water surface and allow it to fall into place.  The granular bentonite particles will sink to the bottom of the pond or be drawn into porous areas where they will swell and reduce the seepage rate. 

This method could possible harm fish if the treatment is done during hot weather and at high rates of concentration.  Although the sodium bentonite is not toxic, the tiny micro-particles of bentonite could attach to the fishes gills and cause them to suffocate due to lack of oxygen.  Treatments during hot weather and in ponds that are low due to loss of water should be done over the course of several days and preformed on one portion at a time rather than treating the entire pond at the same time.  This will minimize the hazard to fish in the pond.

Due to the many variables involved with the "sprinkle" method, such as depth and turbulence of the water, features of the pond bottom like vegetation, sediment, rocks, soil types, the "sprinkle" method is thought to be only 50% as effective at stopping leaks as the "blanket" methods where the bentonite is blended with the soil. 

If you have an idea where the leak is originating from, such as a tree in the dam, big rock, or a layer of sand/gravel, treatment is recommended at up to five pounds per square foot of suspect area, when treating ponds with water in them.

The granules are to be scattered out as evenly as possible by the broadcast method, meaning that they may be slung out with a fertilizer spreader, or simply slung out of a gallon can or five gallon bucket.

This sodium bentonite is approved by the Corporation Commission and the EPA for the purpose of sealing ponds, and it shouldn't harm aquatic life, however, due to the liability involved, the manufacturer states that the heavy treatment rates 'may' harm fish. The worst thing I have seen which may be considered harmful is a temporary "clouding" of small degree of water clarity which clears up quickly unless something is agitating the water, like cattle wading in ponds or heavy winds resulting in high wave action in shallow waters.

Unless the pond is built in very sandy soil, the area which is leaking is likely to be small and perhaps right where the dam meets the original undisturbed soil upon which it was built. Rock and gravel beds are also common which, when dug through, let the water percolate through their bedding plane and under the dam to surface behind the dam. Many ponds are built by persons who push large tree roots and/or limbs or whole trees into the dam as it is being built, which later rot and cause leakage.

Pond Sealer Sodium Bentonite Pond Sealant
Environmentally Safe    ~    Cost Effective    ~    Easy to Apply
			Many ponds composed of a variety of soil types are prone to water loss by seepage. Pond Sealer is a high swelling, chemically unaltered, sodium bentonite that contains no additives. It is an economical and environmentally safe way to accomplish pond and lake sealing to  reduce seepage losses. Sodium bentonite is a natural clay which has the characteristic of swelling bentonite is applied in a layer over porous soil or mixed with a porous soil, and moistened with water, it forms an impermeable layer. When properly applied bentonite does not affect the water or wildlife. Sodium Bentonite is easily applied. In the case of small ponds, bentonite can be applied with simple hand tools and for larger ponds can be applied using ordinary farm equipment. Bentonite makes an excellent liner for new pond construction, for sealing existing ponds with seepages or for spot treating specific problem areas. When sealing a leaking pond to prevent seepage, bentonite can be applied directly to the soil in the pond bottom or it can be sprinkled on the surface of the water and allowed to settle to the bottom. There are three basic application methods: The Blanket Method, the Mixed Blanket Method and the Sprinkle Method.     BLANKET METHOD The blanket method can be used in new pond construction as well as in existing ponds that can be drained. This is usually the most effective method to control water loss. However, more care is required during the application process. MIXED BLANKET METHOD The mixed blanket method can also be used in new pond construction and existing ponds that can be drained. It may be less effective than the blanket method due to uneven mixing, but increased amount of bentonite and/or thorough mixing can minimize this possibility, SPRINKLE METHOD The sprinkle method is recommended only when it is not feasible to drain the existing pond, or in cases of isolated leaks when spot treatment may be a possible alternative.   Soil type and pond size are key factors in determining the amount of bentonite required for sealing. Normally coarse soils require more bentonite. If you know the size of your pond and the type of soil you have, the chart below can help you estimate the amount of bentonite you would need to seal your pond. The chart is based on water depths of up to eight feet. Since greater water depths increase the pressure on the bottom of the pond, increase the application rate by one pound per square foot for water depths from eight to twenty feet and for areas subject to wave action. It is always recommended to perform a soil test yourself or contact your local soil conservation service. Soil Type Clay Sandy Silt Silty Sand Clean Sand Rock or Gravel Lbs. Per ft² 1.0 - 1.5 2.0 - 2.5 2.5 - 3.0 3.5 - 4.0 4.0 - 5.0 Permeability of Pond Sealer is 1.9 x 10 -9 cm/sec.   Pond Sealer is available in 50lb. polyethylene bags; 3,000 lb. bulk bags; and bulk loads.

Seminole Mud Co., Inc.
12160 NS 3610  |  Seminole, OK  74868 |  405-382-1973