Sodium Bentonite

“Benseal” Granular Bentonite
50 lb. bags / 48 bags
per pallet

Sodium bentonite has proven to be one of the most effective sealants on the market.  The fact that sodium bentonite swells many times its mass, then forms a strong water and chemical proof seal makes it an ideal, inexpensive, permanent, and easy to install liner. Because it contains no chemicals, no additives, nothing toxic, sodium bentonite is environmentally-friendly.

Read:  Sealing With Sodium Bentonite

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What Is Sodium Bentonite?

Sodium bentonite is a natural sealant and is used for sealing stock and recreational ponds, dairy and sewage lagoons, and city landfills. It is also effective as a hole plug as well as for controlling dust on highways. Sodium bentonite is one of the “most effective low cost methods” of treating porous soils. It is so effective, that the Federal Government and most states require a liner of sodium bentonite or material comparable, to be used to seal toxic waste lagoons and abandoned water and oil wells. It is environmentally safe, because it contains no chemicals, no additives, nothing toxic.

How Does Sodium Bentonite Work?

Sodium bentonite swells 15-18 times its dry size when wetted by water.

Over several years of testing, Sodium bentonite has proven to be one of the most effective sealants on the market. The United States E.P.A. has ruled that all landfills and waste disposal sites must be lined to prevent the leaching of hazardous chemicals into the existing ground water to protect the environment. The fact that sodium bentonite swells many times its mass, then forms a strong water and chemical proof seal makes it an ideal, inexpensive, permanent, and easy to install liner. Sodium bentonite is environmentally friendly and safe to use.

There Are Big Differences in “Bentonites”

There are several companies selling bentonite clay for various markets. Some of these companies are misrepresenting their product because the public they are selling to does not know the difference.

We at Sturgis Materials are trying to educate the public on using sodium bentonite as a pond sealant.

If you are considering using bentonite as a pond sealant, Please read on!

There are two types of Bentonite clay:

  • Sodium Bentonite: Sodium Bentonite has a natural swelling ability and will maintain its swelling ability throughout its use.
  • Calcium Bentonite: Calcium bentonite is a non-swelling bentonite. It will not swell without additives or chemicals. Calcium bentonite enhanced with additives will quickly lose its swell…It is short lived.

It is the swelling ability of the sodium bentonite that enables this clay to bond with the soil to create an impenetrable liner in the soil.

Bentonites Are Mined Clays

The quality of the bentonite deposits will vary. Some deposits of Sodium Bentonite are very high quality swelling deposits, while others are not as good. Some of the best deposits are deep in the ground and will require many man-hours recovering this bentonite.

So a good quality sodium bentonite begins with a good deposit!

Processing The Clay

All bentonites will contain a percentage of other minerals; Aluminum Oxide, Potassium Oxide, Magnesium Oxide, to name a few and a percentage of sand and silt. It is the process of removing the sand and silt from the bentonite that will produce a higher quality product. The process of removing most of the sand and silt takes time and is costly.

Some companies are not interested in producing a quality product. Thus they will use poor deposits of bentonite and process the material quickly enabling them to sell their product at a cheaper price. However, if this product were tested, it would probably result in a large percentage of sand; something a leaky pond does not need.

The key to using bentonite to seal a pond is:

  • Use a high quality sodium bentonite
  • Apply the product properly
  • Use the recommended amount based on your soil type and square footage of area being treated.
  • And remember: Cheaper is Not better!

How Much Bentonite to Seal a Pond? Use the “Bucket Method” to determine:

In the bottom of a 5-gallon plastic pail, drill 20 to 25 eighth inch holes. Gather enough soil from the area to be sealed to fill about 3 inches of the pail. You can either select the most porous soil, (sand) or a mixture of soil taken from several areas of concern in order to present an “average” soil.

In this soil, mix one to two pounds of bentonite and tamp down in the bottom of the pail. Into this pour a gallon or two of water and see if the bentonite provides the necessary seal. If not, repeat the process and increase the amount of bentonite by half a pound until the water is contained within the pail.

The bottom of the pail represents about one square foot. When you know how many pounds of bentonite it takes to seal the pail, then we know how many pounds per square foot to distribute and roto-till into the pond, dam or other earthen structure.

Bentonite Application Methods

The Mixed Blanket Method

Mixed Blanket Method

  • Drain the area to be treated and remove all rocks and plant growth.
  • Use 1 part granular or powdered bentonite mixed with 5 parts soil to fill large holes and crevices.
  • Plow the area to be treated to a depth of 4 to 6 inches and allow soil to dry.
  • Apply bentonite to the area using the ratio determined by the bucket method or the application rate chart.
  • When the entire area has been covered, mix the bentonite with the top 3 to 4 inches of soil, using a disc, spike tooth harrow or hand rake, and then roll or tamp to compact it.
  • Sandy soil works best for mixing with bentonite because it compacts better. If clay soil is used it must be fine and without lumps.

The Pure Blanket Method

Pure Blanket Method

  • Drain the area to be treated
  • Spread powdered bentonite (unmixed with soil) at a rate of 1 to 4 pounds per square foot over the bottom of the pond
  • Cover bentonite with 3 or 4 inches of soil, sand or fine gravel
  • This is the best method but requires the most care, because bentonite must cover the entire surface to prevent leaks

Sprinkle Method

The Sprinkle Method

  • The pond does not need to be drained but the exact location of the leak must be known
  • Scatter granular bentonite on the water’s surface wherever seepage occurs
  • Bentonite sinks to the bottom where it swells
  • The bentonite gel that is created is drawn into the leaky seams and closes them.
  • This method is not as successful as the mixed or pure blanket methods but will generally work if the location of the leak is known and enough bentonite is used

In all methods of bentonite application, it’s the swelling of the particles that stop the leak. Bentonite will not stop the leak immediately. Some seepage is to be expected for up to a week after the bentonite is applied. Bentonite will not swell in water containing large quantities of mineral salts or acids.

Sealing ponds or earthen structures:
Disc in or mix  the predetermined amount (1 to 4 pounds) of BENSEAL sealing and plugging agent per square foot uniformly over the area to be sealed so that a 6-inch blanket of soil and BENSEAL sealing and plugging agent is formed. Do not neglect the edges of
the dam or the sides/walls of the pond. This sealing blanket should then be compacted in place. As added protection to the sealing blanket, 2 to 4 inches of local soil or sand should cover the sealing blanket and be compacted.

If the leaking area can be identified and isolated, an attempt can be made to broadcast BENSEAL uniformly at 4 to 6 pounds of BENSEAL per square foot of surface area into the water over the area of concern.

Note: Bentonite is more effective as a sealing agent when confined. Therefore, every effort should be made to cover the BENSEAL after it is broadcast with a 2-3 inch layer of sand. This will reduce the potential for dispersion into the water and un-yielded bentonite particles interfering with the gill action of fish.

Sodium Bentonite as a Waterproofing for Basements

As long as homes have had basements, homeowners have been dealing with seepage. As soon as a builder digs a hole in the ground and builds a foundation in it, ground water goes to work, trying to find its way in. One of the most common ways occurs when surrounding soil, expanding due to saturation, causes foundation walls to crack.

And, as long as there have been basement wall cracks, there’s been somebody out there ready to fix them. Like many other forms of home repair, foundation crack repair has had its share of new ideas, but one early method is still in use today because it works.

How Does Sodium Bentonite Stop Seepage from Foundation Wall Cracks?

One method of repairing basement wall cracks is the use of sodium bentonite, a granular clay, to form an impermeable dam against the wall from the exterior. Sodium bentonite is one of a family of bentonite clays; it’s a chemically inert, organic material that is dug from the earth and supplied in powder form. Besides basement waterproofing, it is also used to cap old water wells and for sealing dams and landfills.

To repair a foundation wall crack using sodium bentonite, the basement waterproofing contractor first locates the site of the crack on the exterior of the home. Then, he digs a small hole against the foundation, down to the bottom of the footing. The hole is then filled nearly to the top with the clay powder and is covered with soil so there is no outward sign of the repair.

In average soil conditions, the dry sodium bentonite absorbs water from the surrounding earth, which causes it to expand and harden, sealing the crack. In dry conditions, the installer may add water to get the process started. In any event, the repair created by the sodium bentonite clay process is permanent and durable.

There are, of course, other methods for repairing foundation wall cracks, most notably urethane injection performed from the interior of the basement. In this process the basement waterproofing company seals the crack with epoxy after inserting a number of injection ports. Expanding polyurethane is then injected into the ports, filling and sealing the crack to the outside soil. This newer technology is more commonly used today but is not always applicable in all situations.

When is Sodium Bentonite the Best Choice for Foundation Crack Repair?

Because sodium bentonite is applied from the exterior of the foundation, it is an obvious choice when the crack is not accessible from the inside of the basement. This is usually because the basement has been finished and the foundation walls have been covered by drywall or paneling that the homeowners does not want to remove. In other instances, the interior of the basement may not be accessible for crack repair because of how it is being used or due to other construction.

There are a few obstacles to the use of sodium bentonite that limit access to the site of the crack. For example, if a patio, sidewalk or driveway covers the ground next to the foundation the basement waterproofing contractor can use the sodium bentonite process in that spot but will have to chip out the paving material and patch it afterward. Trees or significant landscaping close to the foundation also present a problem and may have to be removed. It is possible, though, to partially dismantle wooden structures such as decks or porches to gain access.

Even though the sodium bentonite process is a relatively simple one, most homeowners are best served by a basement waterproofing contractor that is intimately familiar with the process and its alternatives.

How to Purchase Benseal

Benseal (granular sodium bentonite) is available in 50 lb. bags. Pallets are 48 bags per pallet. Please call 913-371-7757 for a price quote. Shipping rates vary by location and by quantity ordered. Residential deliveries are subject to a higher rate than deliveries to a business with a loading dock. All deliveries are made by carriers contracted by Sturgis Materials.

What People Are Saying

“I wanted to send you a note to tell you that the Bentonite is working! Thank you so much for all your help with this — we’re so glad we have found a way to deal with the leak and make sure our pond is healthy, and manage the expense at the same time. You have been awesome — thank you!”

CMT- Stow, Massachusetts

Bentonite pond CMT-1 (2) Bentonite pond CMT-1 (1)Bentonite pond CMT-1 (3)


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