Any ideas to stop a leaking pond ****?

[Jeff244]

We have a 1+ acre pond and I noticed a 6" to 8" "bulge" in the side of the dam about 1/2 way down and approx. 20'x10'. The area is wet but I don't see water flowing anywhere. I was wondering if adding bentonite to the water might fix it or if I need to drain the pond and do something more drastic. We drained the pond a couple years ago because of a leaked that turned out to be from some old mining cores in the bottom. We filled in the cores and added bentonite to the the bottom of the pond but not the sides. The top of the dam is a road that we do drive across. I was going to have some stone delivered but I really don't want 50,000 lbs going across the dam at this point.



Thanks,
Jeff

 

[Tororider]

Hehe, funny about the dam.

I kinda agree with you that bentonite might not work until pond is drained, just too hard to place it while there is water in the way.

I would try Pond Boss Forum - Powered by UBB.threads™ They have a forum over there with nothing but pond experts.

Good luck.

 

[Jeff244]

Thanks Tororider, looks like a great site.



Jeff

 

[Dmace]

Here I am trying to think of what you were swearing about in the title of the thread. I read it over an over filling in the blank and it never made sense.

I get it now, you spelt Dam with an "n" on the end.

 

[EddieWalker]

We have a 1+ acre pond and I noticed a 6" to 8" "bulge" in the side of the dam about 1/2 way down and approx. 20'x10'.

Because of this statement, I don't think you have any choice here. Drain the pond and rework the dirt. You didn't say how old the dam was, or if there was any trees on it, but my guess is there is some tunneling going on that has ruined the integrity of the dam. With the formation of the "bulge" you have movement. Now that this has started, it's just a time bomb waiting to go to the next level.

Not knowing your funds or what equipment that you have available makes it tough to guess what you should do to fix it. At a minimum, you need a backhoe in there that can dig it all up and then compacted.

Betonite will help with poor soils, but not for movement in the dam. Once the dam if repaired, it might be a good idea to disk in betonite onto the entire dam just to make sure you don't have this happen again.

Good luck,
Eddie

 

[Jeff244]

I think my original spelling of "dam" was a Freudian slip.

Eddie, the dam was built in 2002. There are no trees, but the clay is a little gravely. We drained the pond in 2006 because it would only reach a certain level, about 6' below the overflow pipes. We found some old mining core holes. We plugged them and added bentonite to the bottom of the pond and maybe 1/3 of the way up. This year is the first year the pond has filled up and stayed up(so far). The pond is about 16' deep when full. From the top of the road to the bottom of the dam on the water side is about 20'. The bottom of the dam on the dry side is about 30' below the road because of the slope of the land. It's also about 240' long. There may be another "bulge" on the other side of the dam. I am trying to figure out a way to monitor the areas either by shooting some grades or by using some string lines to see if there is any movement.

If I drain the pond, I was thinking of removing about 4' of dirt from the water side and mix in some bentonite and replace the dirt. I would also add another 3' or 4' of additional dirt with bentonite. Does this make sense? I am also considering some type of lining could be placed on the dam. I have a Kioti DK 65 with a backhoe. I could rent a sheepsfoot roller to pull behind the tractor for compaction or rent a self propelled one.


Thanks,
Jeff

 

[EddieWalker]

One of the most miserable thing about leaks is figuring out where they start at. It's never a straight line and it's never where you expect it to be. Saying that, I've never actually had to do what you are dealing with. My expereince is with water lines and roofs, so everything I say is based on theory and what I've been told.

The sheepsfoot is for open areas when building up soil in lifts. For a patch/repair job, I don't think it's going to accomplish anything.

There is a special attachment for backhoes and excavators that is similar to a sheepsfoot that's used in trenches, but it's expensive and not what I'd recomend.

Since you have the backhoe, I'd dig out a fairly large hole where the bulge is. Dig out the bulgs and several feet around it. Then dig back to the pond, through the dam. In this situation, I'd think digging more would be better then digging what you think is enough. The water is probably coming in from multiple locations and not just one area. You'll also have to adjust your digging according to what you discover whild digging. You might find an obvious issue like a log that was burried in the dam, or an area of gravel or sand that isn't sealing.

After you have it dug and have inspected the trench closely, start putting dirt back in. To compact it, rent a Jumping Jack or a Thumper type compactor. If you are not familiar with those terms, it's sort of like a jack hammer, except it has a flat plate that bounces on the ground. It's very effective in trenches and small areas. Rental fees are not too bad, but I don't remember exact numbers. Don't try to compact to much dirt at a time as the thinner the layers, the better job it will do.

Eddie

 

[Jeff244]

Eddie, thanks for the response. I agree that the area dug out should go a few feet beyond any problem I find in order to be safe. The area is going to end up being huge. If the affected area is 20' long, I should dig around 30' long. I am including a picture of the dam so you can get a better idea of what it looks like. The problem is that the dam is at least 16' deep. So I will be digging 30' long x 16' deep by probably 40' wide or more at the bottom. I can't really dig from the dry side of the dam because of the angle and there would be nowhere to put the dirt. I could dig from the pond side out and stage the dirt in the pond. Or, I could dig from the top in kind of a bowl shaped area so I can drive the tractor in it and use the bucket. That way I think I could blend it in better when filling. I am just trying to go through as many scenarios as possible so it gets done right when I finally do it. Any and all ideas are appreciated. I opened a photobucket account and put some pictures of the pond and dam on it. 7jeff22 - Photobucket - Video and Image Hosting

Thanks,
Jeff

 

[meadowlarkponds]

Jeff,

I agree with Eddie's comments regarding lowering the water level and digging the area out. One thing to be real careful about is to not put the same dirt back in the hole unless it is high quality clay. If you have to, bring in the best clay you have for the repair.

One other comment from looking at your pictures...it appears you do not have nearly enough freeboard and that may possibly contribute to the bulge. I like to have a minimum of two feet of freeboard below the clay line...not the top soil line, don't count it. It is especially important for a new pond to maintain this freeboard for at least a year. A lot of County ASCS guys will tell you to maintain three feet minimum of freeboard below the clay line, but I've always used two feet and never had problems. After a couple of years, I usually raise the water line 6 to 12 inches, but only if conditions show absolute stability.

Good luck!!

 

[EddieWalker]

Meadowlark brings up a good point about the water level being too close to the top of the dam. But what really cought my eye when looking at your pics was the spillway. Water running over the top of the dam is always a very bad idea. It looks like there is a culvert at one end of the dam, but there is a picture with water on the road with what looks like the pond overflowing.

The problem with water flowing over the dam is that it's just a matter of time until it starts to erode. When this happens you can do absolutely nothing to stop it until it stops flowing and the ground dries up. Without knowing for sure, I belive this is the number one reason dams fail.

The bulge is one thing, the level of freeboard is another thing, and the spillway adds up to a phone call to the builder of the dam. It's starting to look like allot of things were not done properly.

Do you know how he compacted the soil when the dam was built? Most guys can get away with running the dozer tracks over the dirt when building up the dirt in lifts. This works fine with good clay soil and a big heavy dozer. To really do it right, the soild should be compacted with a sheeps foot roller, or a vibrating sheeps foot on a tractor for the very best compaction. If your soil is marginal, then you really need to go the extra mile to get proper compaction.

Eddie