Pond Boss Forums POND CONSTRUCTION Selecting a site Bentonite

I dug some technical ponds in Lower Alabama to use for training Labs. The sand content in the soil is high. I have put some Bentonite in the ponds, but now I want to let them go dry so I can use a vibratory compactor to compact the bottom and sides. My question is, "will the Bentonite which has been previously hydrated, if allowed to dry, reexpand when rehydrated?
Thanks.

Yes. To the best of my knowlege, any clay expands and shrinks with moister and dryness respectfully. Bentonite is just a fine clay that expands more than other types but it will tighten up again when rehydrated. George

Scott,

Yes the bentonite will rehydrate but it may take years to really dry out depending on its thickness. As it drys, a crust will develop and the bentonite will form large prizms with wide cracks. You might want to sheepsfoot or disk it prior to rehydrating (if you can get on it) just to aid in redeveloping an even thickness especially as you said it is the seal for sandy soils.

As George said, it is only a type of clay which is highly expanding (and contracting) depending on moisture content. Ideally, if you bury it before it hydrates the added pressure makes it even tighter.

Thanks for your responses. The pond is about to dry and I am looking forward to doing some work on the bottom. Does anyone have any thoughts on the use of sheepsfoot rollers vs. vibratory compactors? I will adequately disk the bottom prior to using either.

Upon reflection of my previous post and not knowing the particulars of your situation, I should qualify:

If the bentonite layer is <6" thick or so, an offset disk may mix in too much sand and dilute the bentonite's "mojo". A light disking with a straight disk would be preferable. If the bentonite layer is very thin, 1"-3" you might be better off leaving well enough alone and hoping it redistributes itself into the prism cracks after rehydrating. It sure is tough giving good advice over the web and not looking at the project in person!

If the pond is dry you could take advantage of the situation and track in additional bentonite into the sidewalls up to the target waterline. The stuff is like snot when wet so it's pretty easy to tell if it's in a dry enough condition to work.

The construction on my pond was completed in May of 2003--- just two years ago. It filled up with the first major rain and then dried up within 3 months! It filled up again... and dried up. When it was only about 2 ft. deep I added 2050lbs of Bentonite. The pond was completely full last November and is down about 4 feet today. It seems to be dropping about 4 inches per week... but it is very dry in North Texas this spring. I can't say for sure whether the pond is just tightening up or if the Bentonite did the trick. It can't hurt anything but your pride and your pocket book to give it a try. It's still cheaper than pond liners. Pictures of the pond are available if you want to shoot me an e-mail. GS