Pond Boss Forums POND CONSTRUCTION Soil questions Optimum Clay% for Embankment Pond

I have a mix of sandy loam, loam, and clay loam soils in the location for our new ponds. There is also pure blue clay about 6-8' deep.

I intend to build some forage ponds above grade that will be drained and allowed to dry over the winter.

I originally thought my blue clay would be awesome for sealing these ponds. I now realize the pure clay will almost certainly crack when the ponds dry out and then cause leaks on the next fill cycle.

I am trying to determine the best material to use for these embankment type ponds.

Here is what my trusty resource (Agriculture Handbook Number 590: Ponds - Planning, Design, and Construction) says:

Suitability of a pond site depends on the ability of the soils in the reservoir area to hold water. The soil should contain a layer of material that is impervious and thick enough to prevent excessive seepage. Clays and silty clays are excellent for this purpose; sandy and gravelly clays are usually satisfactory. Generally, soils with at least 20 percent passing the No. 200 sieve, a Plasticity Index of more than 10 percent, and an undisturbed thickness of at least 3 feet do not have excessive seepage when the water depth is less than 10 feet.

In other portions, they state that material with a good mix of grain sizes and 10% clay is sufficient to seal a pond with good compaction. A clay blanket to seal over permeable material should have at least a 20% clay content.

Are there still any "dirt guys" on the forum that know what clay% would be most suitable for embankments/berms that need to be capable of holding water, but not cracking when allowed to dry?

Thanks,
FishinRod

Have you bought this book? https://www.pondboss.com/item.asp?id=163&r=store%3Fc%3D8

Since you are going to be digging ponds, I think it would be a great investment.

Good idea Scott

Another great resource, esshup! Yes I have Mike Otto's excellent book.

I religiously followed Mike's advice about testing the soil by making clay balls and clay pencils. My test hole digging went very slowly because I got out of the seat so many times to evaluate samples!

From Just Add Water:

"As a general rule, a site should have 60% clay, if you can possibly get it. This is ideal for a great dam and reservoir. Unfortunately, I very seldom have the pleasure of building a lake with all good material. Often there are lots of different kinds of soil on a single piece of property. Most engineers recommend a 30 percent clay content for compaction."

That is his advice for optimal sealing. However, he also notes that if your ground has big cracks during the summer months, then you know you have clay in your soil.

I am trying to figure out the correct clay% for a pond that will seal (against only 6' of maximum hydrostatic pressure), but won't crack during a dry out period.

Right now, I am considering going towards the lower end on clay content (10-30%?), and then if the forage pond is too leaky, it should be very economical to treat with the addition of some Soilfloc.

I did have several soil tests where I could make good clay balls that held together but contained some fine to medium sand grains. Some of that material would also roll out to "crumbly" pencils. I did have some material that rolled out to some pretty good pencils, yet I could feel that there was still some sand content in the samples.

I am pretty sure I have the optimal material on our property to make raised forage ponds. (Or I could make it by mixing two soils).

I just lack the requisite knowledge. (Which is not unusual for me!)

Rod - based on my experience with multiple forage and grow out cells they won't dry out over Winter to the degree they start cracking - but likely would if left fallow all Summer. You can always refill cells immediately following collection efforts in the Fall and avoid the situation entirely - even with 6-12" water to keep main basin hydrated and clay expanded to discourage leaks from forming.

TJ, thanks for that additional info based upon your experience!

I only wanted the capability to run some "dry out" periods to break any parasite cycles that may develop in an intensively managed forage pond.

[Good Bill Cody link on that below.]

Forage Pond Parasites

IF my cells were subject to cracking, I was going to leave a little water in the bottom. Even if I dried the ponds completely over winter, we still get some winter rains and snows that should keep enough moisture in the clay to avoid cracking.

Further, I think it would have to be a pretty tough parasite to survive a hard-freeze of any puddle of water at the bottom of the pond, plus several inches of frozen pond-bottom soil.

I think the best advice is just to get 'em built and get going on some good water for the forage fish!

Yes, per Cody if you see signs of parasitic or bacterial infection probably a wise course of action to allow cells to remain fallow over Winter after you identify the origin of the issue. Knock on wood I've never experienced any issues in my forage or grow out cells with infections. I've had a forage cell fallow all Fall and Winter and it's still very soft/moist in basin and sidewalls yet this Spring. I can only safely walk on the top 1/3 of sidewalls, everything else is still mucky. I think the layers of organic material and silt provides a blanket keeping clay moist and expanded...the only positive spin I can put on eutrophication process! I plan on filling next week and starting to fertilize to get blooms kicking. Still not sure what I'll be raising there - just setting the stage for whatever project interests me. I harbor zero concerns with leaks originating from leaving pond dry over Fall and Winter.

One thing I have found is that if you have vascular plants in the pond, and let the water get below where they are growing and it goes through a freeze cycle for the winter it won't reliably kill the plants....... Or maybe the seeds stay vialbe in the pond bottom even though it's frozen solid? In any case, EWM, CLPW and American Pondweed all will grow back.

I also have Mikes book and his discussion about plasticity of clay. He says his most used test is getting one of the grandkids to make a ball out of the soil. Then throw it against the side of his pickup. If it sticks, start the dozer.

"I also have Mikes book and his discussion about plasticity of clay. He says his most used test is getting one of the grandkids to make a ball out of the soil. Then throw it against the side of his pickup. If it sticks, start the dozer."

That is SO Mike Otto right there! Every time I hang out with him, I look for little round mud spots on his truck, broken toys, nails under his tires, and any other gifts a grandkid might offer.

At LL,2, we had two 1/10-acre hatchery ponds. Raised literally tens of thousands of fish over the 18 years we lived there. As a matter of fact, seined one of them with the new owner Saturday afternoon and moved at least 2,000 bluegills 5-6" long and stocked the other ponds.

I drained those ponds about every three years because they were so productive I didn't want to disrupt their mojo. About 4 years ago, I drained both of them and had Otto's son-in-law push out the silt and collection of years of fish waste.

The clay is so thick that it couldn't really dry out. The longest I let them sit was four months. The only cracking happened with the silt, not the clay.

Thanks Bob. That is the kind of "real world" advice that leads to practical solutions.

There is significantly more published information regarding the construction phase of pond building compared to the maintenance phase of the "bones" of the pond.

I am happy to get as much real world maintenance advice as possible!