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Bentonite FAQ

What is Sodium Bentonite Clay?

Sodium Bentonite Clay is a naturally occurring clay that is used for its unique swelling and sealing capabilities. The clay is generally delivered in a granular form for use as a soil amendment in ponds, lagoons, lakes, and water treatment facilities. The bentonite clay is gray to white in color with extremely fine clay particle sizes. The bentonite clay can expand up to 30x it's dry volume when exposed to water.

How does Sodium Bentonite Clay seal a pond?

Sodium bentonite swells into pores in the soil matrix sealing the pores and preventing water flow. Proper application of the bentonite is critical so that the bentonite is thoroughly mixed with compacted soil or in a uniform layer between compacted soil layers. The confinement of bentonite allows it to force its way into soil pores when it is exposed to water.

Does Calcium Bentonite work as well as Sodium Bentonite for sealing soils?

NO, Calcium Bentonite is NOT the same type of clay as Sodium Bentonite. Calcium Bentonite is a NON-swelling clay. The high swell Sodium Bentonite clay can expand to over 30 times its dry volume when exposed to water. This swelling action helps to force the sodium bentonite clay particles into soil pores which seals the pond soil. While the non-swelling clay does have a fine particle size it does not expand and push into voids in the soil matrix. Calcium bentonite and some other clays can be treated with additives to create some expansion, but the effects of the additives are NOT long lived.

How is Sodium Bentonite Clay processed?

Sodium Bentonite is mined from deposits found in a relatively few locations. Once the raw clay has been exposed, it is stockpiled for processing (drying and sizing). There are two methods of drying, Sun Drying and Kiln Drying. This may seem like a minor detail, but it is significant in assessing the quality of the bentonite clay produced and packaged. Kiln drying exposes the clay to very high temperatures which alter the clay. This can significantly reduce the ability of the clay to swell and fill soil voids. Sun drying is preferred as it does not expose the clay to excessively high temperatures and also results in a major decrease in the amount of fossil fuels consumed to process the clay.

Is there a laboratory analysis of the Bentonite clay?

Yes, please contact us for specific laboratory analyses.

Can you send a Material Safety Data Sheet (MSDS)?

Yes! The MSDS for our granular sodium bentonite clay can be dowloaded here.

Do I need to drain the pond to apply Bentonite?

For best results we do recommend draining the pond. The two most effective pond sealing methods require the pond to be drained and relatively dry to be most effective. Mixing sodium bentonite clay with the top 3 to 6 inches of soil then compacting with a pad foot roller is the preferred method of application. The blanket method is achieved by applying a continuous blanket of bentonite clay over the entire pond bottom. This is followed by a cover layer of 6” of soil. The swelling characteristics of the clay work to the pond owner’s advantage when the swelling clay is confined using one of these methods.

Can I sprinkle bentonite through the water column to seal a leak?

In some limited scenarios this can be effective. First, it is important to know the precise location of the leak. If you want to attempt this method, we recommend a pelletized form of Sodium Bentonite known by the trade name Holeplug. This bulkier form allows more precise application of bentonite though the water column. If you do not know the precise location of the leak, a polymer application that will migrate to open pores and fissures in the pond bottom is a better choice.

Does bentonite quality vary?

There are a large variety of clay deposits of varying quality. One of the primary analysis to determine the quality of Sodium Bentonite is the Swell Capacity. The deposit of Sodium Bentonite Clay that Natural Waterscapes has secured has been laboratory tested with swell capacity of 30! This high quality deposit is ideally suited for pond sealing. Detailed results available upon request.

Do the bulk sacks of bentonite come on a pallet?

All of the bentonite clay bulk sacks are placed on a pallet when shipped by enclosed van trailer and in less-than-truck load quantities. For dedicated flatbed trailer deliveries, pallets are typically not used and the sacks can be unloaded using the four lifting loops on the top of the bulk sack. For lifting on the construction site, the bulk sacks are equipped with pallet fork loops on each corner of the top of the bulk bag.

What do I need to unload bulk sacks of Bentonite?

You will need a forklift or other pallet fork equipped loader capable of safely lifting and moving 2,200 lbs for the 2,000 lb bulk sack, 3,200 lbs for the 3,000 lb bulk sack. For dedicated truck deliveries, you will need a pallet puller to move the pallets to the rear of the cargo trailer unless a flatbed trailer delivery is specified.

Is residential or construction site delivery available?

Yes. Adequate unloading equipment and a level area to safely operate that equipment is required. Lift gate service is NOT included in the list pricing. For small orders of 2,000 lb super sacks (6 or less) lift gate service may be available in select locations. Contact us for details.

How do I empty the bulk sack of bentonite?

Each granular bentonite bulk sack is equipped with a drawstring pour spout on the bottom of the back for conveniently dispensing the bentonite pond sealer. The spout allows easy distribution of the bentonite and can be used to control the flow rate out of the bulk sack as well.

What is the best way to spread bentonite clay in a pond?

For the light application rates using the "Mixed" bentonite application method, we often recommend an agricultural broadcast spreader like those used for spreading fertilizer or lime. With this type of spreader you can control the application rate and evenly distribute the bentonite across the pond bottom and sides. For heavier (2lbs per square foot and higher) "Mixed" and the "Blanket" bentonite application rates it is often easiest to dump the bentonite in a straight line or pile from the pour spout of the bulk sack. Then, using a bulldozer, skid loader bucket, or agricultural rake spread the bentonite into layer of even thickness.

Detailed Bentonite Application Rates for Pond Sealing