Pond Boss Forums POND CONSTRUCTION Building a dam Dam Seaping

I purchased my grandfathers property a few years back years after he had passed. The current owner had let everything grow up including the ponds. I decided to renovate the larger pond and fill in the old livestock pond.

The renovation/expansion went well. We took a 1/2 pond that was 10' deep and made a 2 acre pond 26' deep at the damn and 4' deep at the intake.

I finished the project just in time for spring last year and waited on mother nature to fill er up....oh wait we had a drought last year. I have a farily large creek that runs the property line, I purchased some pumps and 5 million gallons or so later it's full!

A week or so after filling the pond I noticed a few damp spots on the dam towards the bottom. I didn't worry much, but the other hand we took an already existing dam that was wide enough for a bicylcle, added about 600 tons of dirt, made it 60 foot wide at the bottom and 30 foot wide at the top.

Over time (a few more weeks) the damp spots now have become little streams in two places at the bottom of the dam. It's hard to say how much I'm losing but my pump will run about 40,000 gallons of water before it runs out of gas. It will take about 2 weeks before I need to run it again.

So here's where I screwed up I think when building the dam. We used the existing dam and built off it, BUT...I was told that I should have keyed the old dam (which makes since duh) and that the water is seaping through the old dam and the new.

That being said, and that's a best guess btw, over the winter I could not pump water and I lost approximately 8' from November to March. We got heavy rains this spring, the pond filled and I was busy with everything else, plus the river has been out 5 times, so I didn't start pumps until last week. This time around it looks like I lost around 4 or 5 feet and the dam was moist but there was no standing water or tiny streams.

All that being said, does anyone think that it will seal up on its own? I've been giving a few options but not really liking either. One is to drain the pond and put a liner on the dam, this is an issue for the 1800 or so fish I have. The other is to dig the middle of the dam out down to the old dam and install a tile to help direct the water. I don't care for that one either considering my backhoe wouldn't be able to go deep enough and I would have to redo all of my pipes.

My thought is to pump water until (fingers crossed) it seals. the only bad part is I have a road behind the dam, I learned last fall I can not use it without at least putting tile down. Buried my side by side to the frame....

Any ideas, thoughts, suggestions from the experts out there would be much appreciated! Chad

Unfortunately you won't like what I have to say. I think it will keep getting worse over time. Key/Clay/Compaction is the only way in my mind to fix it.

I was afraid of that. How would I go about packing the key? Would a track hoe be enough to pack it using the bucket? Or would I have to drain the pond remove the dirt to the old dam and then do the key? One thing I forgot to mention, there were several trees on the old dam. I found out later that when you cut the trees down and the roots die that was a potential for leaks. Wish I would have consulted this site before I took this project on myself!

My guess on this is you would need to dig a trench deep enough to go way deeper than the old dam which is then the new key. This needs to go the whole length. Then pack the new key and trench all the way back up to top surface with good clay using a sheepsfoot roller.

I also wonder if it would be a possibility to put a keyway and new dam on the backside of the current dam, providing there is enough room and you would have enough available clay.

There was an old thread that I read where one pond builder (was it Otto?) said that sometimes you can dig out and then repack with clay a wetspot from the backside and it will work. That thread talked about doing just this and how it worked. My thought is that it's iffy.

Interesting concept, digging the key into the back of the dam, I would have enough room to do so.

This isn't the one I remember, but check it out.

http://forums.pondboss.com/ubbthreads.php?ubb=showflat&Number=4987#Post4987

26 feet at the dam is a lot of pressure for an earthen dam, however a 60' base and 30' topper is pretty stout. A few questions.

1) Did you add dirt(fill, topsoil rubble) or clay to make the damn bigger?

2) Did you compact the clay in 6" layers, for the new dam?

3) When you added to the dam; did you scarify (peel off the top of the original dam) and compact the existing dam.

4) What is the inside slope of the earthen dam? ex. 1:4 rises 1 foot for every 4 foot of run. Im coming up with probably about a 2:1 (very steep), however the backside may be steeper.

I will try to help in any way i can.

Hi BirdD@wg, to answer your questions;

1) I added clean clay to the top of the dam to make it bigger. When we hauled the clay in it was a little moist.

2) We actually compacted it in 3 to 6 inch layers on the new dam

3) I did peel some of the old dam off, mostly because there were tree stumps I had to remove. The existing dam had been there for more than 30 years.

4) This is where is gets somewhat screwy. In November when we were finishing the dam we recieved a large rainfall that filled the pond to the orignal dam height. The slope on the water side is close to 2:1 and I put large flat 6" thick slaps of concrete from nearly the bottom to the top. When we added the new clay I was not able to pack the water side slope only the top as I was laying it down. The backside of the dam is actually about a 1:3 slope up.

At first we thought maybe we had dug below the key on the original dam and it was going under the dam. But we really didn't take much out of the bottom of the old pond and the builder thought he originally made the pond around 15' deep. When we drained the pond it was about 10' deep.

This spring with all of the rain the pond filled quickly, 8' overnight and was coming out of my 12" discharge pipe quickly about 3/4 pipe full. At the end of the year last year we did not have time to put our down pipes in on the backside of the dam. The water coming out of the pipe cut about a 5' deep chanel in the backside of the dam. When we were putting the pipes in and finishing the backside out is when we came up with the theory that the water was coming between the old dam and the new. About halfway down the cutout the clay was moist about 6"s below the dirt surface. We figured that the water was traveling down the backside of the dam underground until it got to the bottom of the dam and had nowhere to go but up and out.

They are very minor leaks, but I would prefer to fix them if need be. I really don't want to pump water the rest of my life if I don't need too. Thanks again!

One other thing, when building the dam, before the rains came, we added probably 7' to the old dam in width on the water side. That was packed in. With all that dirt I never would have thought an issue. But then again it is a lot of pressure. We thought it was getting better beings it quit leaking 4 or 5' below pool rather than the 8' last winter.

I don't know what to say OSS. It sounds like you did everything the right way. I really thought it was a seam between the old dam and the new dam. It could be the root system of the old stumps. If there is any cracks; a dam that is 26' deep will find it. Another question. When you compacted the soil did you use a sheepfoot roller or just a dozer? One thing I do not like is the damn having a 2:1 slope. I personally would never go tighter then a 1:2 (your dam is 4 times steeper). When any earthen slope is greater then a 2:1 it will slip and i dont care how well its compacted (even with vegetation or concrete rubble).

Hey BirdD@wg, sorry for the delay...it's been pretty hectic! I agree with the slop, the front side of the dam is pretty close to straight up and down for the 1st 10 feet or so only because of the water in the pond while constructing it. I know I should have pumped it back out, but it would have taken me days and by the time it would have dried it would have been January.....Hence the reason for the huge concrete slabs we put down. So far so good, but yea I agree eventually we will probably see slipping. I couldn't get my hands on a sheeps foot....wish I could have...packed with my JD 650 dozer. It could be the old root systems....I really wish I would have tore the old dam out entirely and started over....but as the saying goes hindsights always 20/20. There were large amounts of trees on the dam, so much so you couldn't hardly see it. I don't know sir, for this year I'm going to keep pumping and keep my fingers crossed. It doesn't leak much, I have to run the pump a little less this year than last. My pump runs about 15,000 gallons for about an hour and a half. I half to run the pump about twice a week to maintain full pool. Last year I nearly had to run it everyday after it was full, but it was also virgin soil with soaking in etc....we shall see! Thanks again!