Pond Boss Forums POND CONSTRUCTION Soil questions Cleaning out and adding clay...

I have a run off pond that is down 5' and I am planning to clean out the shallow end and would like to have clay hauled in to reseal the bottom and sides.

When the pond was dug...clay had to be pushed from the deep end to the shallow end and I don't think it was done very well. I am thinking that I am loosing water from the shallow end on the sides. The water level drops and holds...so I am thinking the bottom is ok and that I just need to add clay on the sides.

My shallow end...when full...could hold 7' of water. How thick should I put in the clay so it can hold the weight/pressure?

Does anyone have an equation to figure out the number of yards needed? If someone can tell me how thick I need the clay...I know the number of square feet that I would like to cover.

Thanks,
Wes

How do you pack clay on the sides?

wmaurer,

Welcome to the forum. Your posts in quotes below followed by my response.

"When the pond was dug...clay had to be pushed from the deep end to the shallow end and I don't think it was done very well. I am thinking that I am loosing water from the shallow end on the sides. The water level drops and holds...so I am thinking the bottom is ok and that I just need to add clay on the sides."

Generally in my experience ponds do not leak from the shallow ends unless there is some kind of underlying structure problem such as rocks or fissures or such. My ponds have no clay, only sandy soil in the very shallow ends and they do just fine. The water pressure is toward the deeper end, toward the clay dam. Water always flows downhill. That is where most leaks happen. Do you have rocks or some kind of bottom formation that caused them to push clay into the shallow ends?

"My shallow end...when full...could hold 7' of water. How thick should I put in the clay so it can hold the weight/pressure?"

If 7 feet is your shallow end, how deep is your deep end? Generally, if you have good clay, 2 feet thickness of clay is sufficient to prevent leaks through the bottom.

Something about this just does not compute. Someone dug your shallow end out to 7 feet which included pushing some amount of clay from the deeper end back into the shallow end? And its still 7 feet? It just does not compute to me.

To keep this simple...If you had to make a liner out of clay for a pond that is 7' deep...How thick would you make the liner?

Wes,

Good clay or bentonite should be incorporated into the top six inches of existing material with a disk, rototiller or other implement and not just spread onto the soil surface. Recommended quantities vary with existing soil conditions. Probably 2 to 3 pounds of good bentonite per sq. ft. should do the trick. Doesn't sound like much until you do the math for a surface acre..... 43 to 65 tons per acre!! This can get expensive in a hurry unless you have some other good clay material on hand.
Good luck,

Ed

Wes,

I use USDA publication 590 as my "Bible" for pond construction. On page 63 of that reference is the following statement for thickness of a clay liner:

"Thickness of the blanket depends on the depth of
water to be impounded. The minimum compacted
thickness is 12 inches for all depths of water under 10 feet."

Personally, I have talked to many pond guys in my area and the consensus among them is 2 feet of compacted thickness. If it were me, I would error on the safe side and go with 2 feet even though that is a lot of clay. Good luck and please let us know what you decide and how it works. Thanks.

p.s. you can download that pub from their website...or I would be happy to forward one to you.

Yep...I've got the same advice. My NRCS agent says 1' thick clay liner, and the "best in three counties" pond contractor says 2'. I based my calculations on 2'.

PJ,

I've found that 2 feet of good Texas clay will stop anything...