I started a DIY project last fall to renovate an old 1/4 acre pond into a new 2 acre pond. Without going into all the details, I got caught short by the fall rains and was unable to finish. I lowered the spillway to accomodate the reduced dam height until I could get back to it this spring.

Well, I started back to it this past weekend and found significant leaks in one corner of the dam. I'm attempting to plug those leaks by adding layers of clay to the backside of the dam...can't do anything about the front side because it is under water. This seems to be working, but I'm still a bit nervous...anyone repaired a dam in this manner? From the backside? Thanks in advance for any comments.

not sure i like this idea very much,this normally does not work in our part of the country.i would put something on the front side of the levee then pack the back side like you are doing.can you get bennointe are drilling mud,both of these will work very good on the water side of levee.

Bentonite seems to only work about half the time, if that often.

Why shouldn't it work? Clay is clay whether it is packed from the front or the back...yes the water pressure does work against you on the back side but that pressure should be significantly reduced by the front side clay.
You may be right...but like I said it seems to be working. No visible leaks now for a week and I'm still packing the clay to it....and getting a larger pond in the process.

Why won't it work?

Just a thought.
By packing clay on the back side of the dam you are stopping the water at that point. The water can no longer flow through the dam so it begins to saturate the soil the main part of the dam is constructed of.
Saturated soil will not withstand the water pressure created by a pond of water and may even add to it.
If you pack as much clay on the back side as is in front it might work. Otherwise I would think it will eventually break.

Again, I don't know that the above is true, but it seems logical.

Ric,

What you say makes sense to me, kind of. Seems like it would saturate whether it was seeping on through or not, but then just about all ponds seep some. I just don't know. Seems that theoretically, there is some amount of clay that packed from behind would hold....whether that is 1 foot or 15 feet I don't know, but given enough clay it should hold, seems intuitively...but intuition doesn't work on ponds.

Any other opinions?

I guess time will tell and I'll try to pack as much as I can back there...I've already added about 5 feet of good solid clay to that location...and made a big hole for fish on the front side.

can you drop large loads of clay on the front side.i do not normally do this,but over time it too will settle and add something to the front side.i just have not had alot of luck with fixing leaks from back side of dam.i think over time your water will come out in a different place.however,one time we added clay to front side of a dam and on top of dam and kept packing with track hoe and we did seal this pond.good luck.

outdoor family,

Thanks for your comments. I do appreciate it. I have already stocked the pond, so I'm afraid that adding clay in the front would really cloud the water for a long time. I may try the bentonite.

The leaks are or rather were coming from a section of the dam where I had some difficulty (otherwise known as getting the dozer stuck!) and I suspect that the process of removing the stuck dozer affected the integrity of the dam.

Its dry there now due to the clay packing, although that may only be temporary. Based on your comments and Ric's theory which is very plausible, I think I should try the Bentonite as an insurance policy. Thanks.

It would be interesting to know the distance and extent of pond water penetration through dams. Anyone want to drill some test holes into the back of their dam and let us know when it gets wet? Or come up with a non-destructive way to find out?

'Lark, when I was first married I had some "difficulty" bush-hogging at my In-Laws' farm. I mowed the flat spot next to the creek, not knowing it was the "duck pond" which had silted up. The other two available tractors and their motor home were unable to pull me out. We ended up spending the afternoon winching it out with a come-along cabled to a big tree. I think my Father-In-Law was still laughing about it 15 years later when he passed on.

Theo,

Then you would have had a good laugh if you would have seen my dozer sitting in water over the tracks on the face of the dam....just one more pass to get that last bit of dirt and then disaster. Happened so fast, nothing I could do. What a circus getting that thing out!

I can laugh now, but didn't at the time.

Theo,

Interesting, you are referring to what Engineer’s call the “freatic line”. In other words there is a predictable wet line inside the structure from the water surface on the front side of the dam to the seepage area on the back slope. This internal wet line can be manipulated prior to construction by incorporating a sand drain inside the structure. This is generally a 2 ft X 2 ft. trench filled with course sand at or slightly below natural grade. Some landowners even install a 4 inch perforated pipe inside this sand envelope to assist the sand trench in draining off any water trying to make its way through the dam. The eventual system works similar to your sewage drain field, only in reverse. The objective, is to control the freatic line and eliminate wet and unstable backslopes. I probably didn’t do a very good job explaining. Suffice it to say, there are ways to counter seepage problems prior to construction.

Edward,
At the base of my dam, at the very lowest elavation, I often have a puddle of stagnet water that is a mess when I brushhog. The slope of the land is only a few degrees, but falls toward a wet weather creek ditch. I would like the field to drain better. Do you think it would help dry up the field if I plow a trench to the ditch, lay in a four inch perforated drain line, cover it with coarse sand, and then cover with top soil? Is this simular to the drain tiles farmers use for wet fields? Any comments are appreciated.

Jeff,

Exactly; only before you cover the sand with topsoil, try to find a roll of landscape or drain fabric. These fabric rolls are generally 6 to 8 ft. wide. The fabric is porus and allows water to penetrate into the sand but not your topsoil. If you do not use the fabric you may plug your sand with fine soil particles eventually rendering the system in-effective.

Good luck,

Ed

Many Thanks!

Meadowlark. I hope your pond camara has done its job. On your question about pond dam leaks we fixed a similar problem with drilling mud.It comes in sacks and is dry bentonite clay.It was called aqua-gel. We had a sand that was leaking into the dam at the bottom. We used 5 or 6 sacks on a 5 acre pond.The clay powder when wet did not cloud the water as it sank toward the bottom and toward the leak. In about a week the clay had been pulled to the leak and mixed with and covered over the sand. Good luck and report your results. Thanks ewest.

ewest,

No sign of trespassers. I have informed some possible suspects that cameras are deployed along with traps. Even showed one of them a camera, the fake one. Made a hell of an impression. I think it is having an impact, I really do.

Meadowlark,
No two ponds are the same. You might of hit just the right spot with your clay and sealed it.

Kent,

I think it is very possible...better to be lucky than good.

While trying to pack it, I found a very soft spot in which the dozer kind of sank down. I believe that was a cavity or something. It was kind of scary to hit it while sitting halfway up the backside of the dam that was leaking. The thought did cross my mind that maybe the whole thing was going to give way. Its holding great right now, no sign of leaking or moisture at all.

It never ceases to amaze me with what I don't know and worse, failed to think about.
The area where my pond was dug was an old rice paddy, ground water at the surface in the lower half of the plot. As the sandy clay was being excavated I could see the water running from it back into the hole. The pond filled to 8' in about 2 weeks with ground water and seepage from the banks. This process slowed, but continued for another 2 weeks. We are experiencing a severe drought and day time temps have been in the high 90s for a couple of months. The water is now receding, I believe from evaporation and seepage back into the banks. I can see a wet line that looks to be about 2' above the water line and any where on the borrow dams I can dig to, damp to moist soil in 6" or less. There is no visible water line on the exterior surface of the dams, the pond is about 10 weeks old. I had assumed that the moisture would eventually drain. I was planning to take the water level to within a foot of the top when the monsoon started in another month or so, which would be about 11' deep in the center and 7' at the highest dam, 10' tall on the backside.
Is there a practical way to remove or reduce the water content of the banks?
Sorry for the windy question.

By way of adding closure to this thread, here's the final results of my "dam repair from behind the dam" experiment:

Out of four leaks, three were successfully sealed by adding clay behind the dam in the leak area (no moisture at all for over a month). Very easy fix, assuming an adequate supply of good clay. The three that were repaired in this manner were part of a new dam segment that had been added to an existing dam.

The fourth leak, which was part of the existing dam segment, was originally caused by critters, e.g. beavers and/or nutria. It has proven to be the most difficult to stop. It may be that the only real fix will be to tear into the old dam and repair the leak at the source.

So, what I learned was that yes, a leak can be repaired from behind with adequate clay, but it is by no means a guranteed fix. Leaks originating from internal dam structure problems probably can not be fixed with this technique. However, other leaks that are associated with new construction, may be repaired with this technique in a manner more economical and efficient than use of other alternatives.

Meadowlark,
I too had a dam leaking on a pond I had built last Aug. It was very dry after it was dug and it cracked the clay core. It didn't finish filling until Feb. Since the frost was still in the ground I had no idea it was leaking until the spring thaw. It was 1/2 full in Oct. and I went ahead and stocked it, so there was no way I was going to drain to fix. My excavator said he would repair for free if I could come up with a way to do it on my terms. I read this post and figured what the heck. He cut about 1/2 way thru the dam and repacked at the leaks back in June. Hadn't had any real rain since and between the leak and lack of rain the pond was down almost 5'. Well the rains have finally came ( 9 1/2" in 8 days ) and filled the pond within a foot of full with no signs of leaks. It worked for me too.....THANKS!

h20fwlkillr,

Well done! And it didn't cost you a penny. A good contractor will stand behind his work...if he doesn't find one who will before ever turning the first dirt.

Tried to convince a couple of other folks on here that this approach would work for leaks of that type, to no avail. Thanks for your report.