Pond Boss Forums POND CONSTRUCTION Building a dam I think I have a leak around the overflow pipe

Wasn’t sure exactly where to post this. Hopefully this is the correct place. This is the first time in years my pond is full. I’ve noticed it really seems to drop quickly when completely full. It’s down about 4” now, which would have been fantastic a few months ago, because it was almost 2 feet down. I was back at the base of the dam looking for any evidence of a leak. There was a trickle of water in the old ravine we dammed up to build the pond. It didn’t appear to be coming out at the base of the dam. When walking around back there, which is very brushy with briars and poison ivy, I stepped near where the drain pipe comes out at the base of the dam. My foot sank in to deep mud, with water coming to the surface. It almost has to be from water seeping along the pipe.
The guys that built the dam put in the pipe. I was there 10 years ago when they put it in. They put collars on it to block seepage. I’m not sure they’re in the right places, and I’m fairly certain they didn’t get the clay packed in tight enough around the pipe and collars.
I’ve dug it out around the head of the pipe and packed in kitty litter, and soil floc. I thought it was fixed, or at least slowed down. Now I’m not so sure. Maybe from being so low for so long, the leaking area has opened back up.
I’m thinking of getting a hold of some heavy plastic and trying to fit it around the pipe at the inflow. Cinch it very tightly around the pipe. Then spread the plastic out maybe 8 feet down into the water and along the water line. Then dumping clay on top of the plastic.
Any thoughts on this being a viable solution? Any better ideas?
Just an FYI, I was told by a member here (Rex Rainman) many years ago, that this was probably my situation. His recommendation was to completely remove the drain pipe, and put in a siphoning system. I elected not to go that direction. The soil above the pipe at the top of the dam, definitely settled where the pipe goes through. That indicated to Rex that the pipe wasn’t packed in properly, and why he suspected a leak.

Picture from 10 years ago, when they put in the pipe. Looking from top of dam to out flow.



From below, about where they put in the first collar.



Looks like it’s packed in fine, but the ground really settled above it.



Early fix attempt in 2015.



Pic from 2016 shows water in original ravine behind the dam, and the relationship of drain pipe to ravine.


What it looked like in October last year. I’d have to clean up around it to get any plastic to adhere to the dam.

Another thought.. How about just removing the pipe, and leaving it out. Just letting the spillways at both ends of the dam handle any overflow? Our county in NE Missouri is pretty dry. We seldom get big rains. This is the first time in a few years the pond has actually been full.

Right at the face of the dam where the pipe enters the dirt is gonna be pretty hard to seal off, if it was me I would try to go about ten twelve ft behind that and dig down around the pipe, try to get above but close to one of the seep collars, and compact really good clay along with generous amounts of bentonite and use a plate compactor to pack it really good all the way up past the water level at a minimum.
I have sealed several minor leaks off that way.
At that depth it is more likely to stay moist whereas at the surface it will dry and crack much worse.

Good Luck!

Hmmm. That sounds doable. I heard from another source to pour concrete around the pipe and maybe 5 feet out from the pipe. The thought is that the concrete would adhere to the plastic pipe and seal it off. What are your thoughts on that? Not a good idea?
Thanks by the way.

I was going to type a comment similar to gehajake's. I believe he has proposed probably the best solution.

However, I think you need to be certain you have correctly identified the problem. I like that your pond goes down 4" very quickly when full and then the water level drop more slowly. Can you confirm that behavior?

Put an easily-read measuring stick in the pond and note the daily water drop after the pond is full. If the pond drops the first 4" very quickly and then slows under nearly identical evaporation conditions, then I suspect you have a pipe seepage leak very high in the face of the dam. That is absolutely the best place to have it!

As to your top seal solutions: Clay actually expands in contact with water, as does bentonite (a specific type of clay). Unfortunately, these clays then shrink (and crack) when they are desiccated during exposure to air. Soil floc (and its near cousins) are types of cross-linked polymers that also swell when exposed to water. However, I do NOT know if they subsequently shrink after long-term exposure to air. (You might need to send a PM to TJ?) If his product also shrinks, then I don't think you can create a "top seal" at your drain pipe with those types of materials since they will all crack after multiple wet/dry cycles.

Concrete does not have that property, but I still think it would be a poor material to create a top seal - without some additional labor. Dry cement mixture does expand as it is hydrating with water, but it then begins contracting slightly as it cures. Therefore, your sealed concrete around the pipe may still let a tiny bit of water through after it cures. However, the good thing about concrete is that it is erosion proof in your application. Once compacted clay and soil materials develop a tiny water flow path, it tends to get bigger over time as a few particles lining the path eventually get dislodged and washed away. Concrete does NOT suffer from that particular problem.

I might try a cheap fix first? Dig out the dam face with shovels as deeply as you can along the pipe. Then use wood (or well-compacted) clay to create your concrete form. I would then rough up the pipe and spread the heavy black mastic they use to seal concrete water pipe (bell and lip). If you can't find that, use the black roofing mastic with embedded fibers. Spread your sealer to ensure 360 degree coverage plus coverage for all of the concrete thickness around the length of the pipe plus an extra inch that will stick out into the air. Then pour your concrete "collar" at the top of the drain pipe. After the concrete has cured, use a putty knife to push the exposed mastic down into the pipe/concrete circumferential joint.

(If you do have some membrane type material similar to a pond liner, you could even line the bottom of your "form" with a sheet fitted tight to the pipe like a traditional anti-seep collar.)

If that concrete "top seal" doesn't work, then I would go to gehajake's solution and expose a much longer section of the outlet pipe with a mini-excavator and try creating a good seal across a larger length of the troubled area.

FR, I’ve not poured a lot of concrete. Do you think I could put quickcrete in the form, right out of the bag? Then let it set up as it pulls moisture from around it? Or, do I need to mix it in a wheelbarrow or portable mixer and pour it? I just wasn’t sure I could get a big enough batch made to get it all done at once. Where I know I could get enough powder in place.
I’m not up there often enough to measure the drop daily, maybe every two weeks. I was really surprised when I went up last Thursday to mow. It had been down a few inches, we had just had a two inch rain. I expected it to be running out the pipe again. Instead it was still two inches down. It had dropped that much in a week. That’s quite a bit faster than what I’d been seeing last year. Especially when you think about how much volume is in those last few inches.
Thx

I don’t think concrete will cure all the way to the center if you just dump it into the ground and hope there is enough water to penetrate the whole thing before the shell cures. Just eat your Wheaties, get a friend, and mix up one bag at a time and keep dumping the mix in. Standard concrete takes quite some time to cure, longer than it will take you to mix several bags up.

Of note, you cannot go too think, as the heat of curing can cause the concrete to crack. I don’t know what that limit would be.

I am starting to think that plastic pipe for a drain is problematic from a thermal expansion point of view. If the soils are warn surrounding the pipe in the dam center, but cold water flows through, the pipe may shrink enough to allow water to make its way along the outer edge despite a good installation. Sure the collars should stop it, but only if the soils around the collar are well packed, which seems difficult to do below the pipe. Maybe it would be ideal to box in the collars with concrete when installing? Even if it is just the lower half to seal the collars that are difficult to pack.

Also, concrete may stick to the plastic at first, but a shrinking cold pipe may still pull away.

At.east I won’t have to haul water down there. Haha!

I have limited concrete work experience, but I have observed some terribly weak and flaky concrete where guys tried the "dry bag" wall and in other circumstances.

I have done dry Quikcrete mix for 4x4 fenceposts and had zero problems. However, I expect the cured concrete still had cracks in it deep underground. In that application, the cracks are no harm, because you still couldn't pull the fencepost free (unless the cracks created a perfect upwards bevel).

I have mixed small batches of concrete in a shallow mixing tub with a concrete hoe. (The tubs are cheap at your big box store.) I have also rented the rotary mixers for slightly larger jobs. ($50 for the weekend?) You either need 120VAC at the site, or your own generator.

As to monitoring the water level, I couldn't remember if you lived at your pond or not.

Do you have a game camera with a time lapse feature? If so, set it up to take photos every 8 hours from a location where you can read the water staff in your pond. That should get you good data over a month where hopefully, your pond fills and then goes down a few times.

My experience with Quikcrete was not a positive one. That stuff cures way too fast and runs hot. I used it to set in block windows for my basement, and I didn’t move fast enough for that crap to harden before the windows were in. Next thing I knew I was the sad owner of a new hammer drill,

Use plain old concrete mix, it will give you time to work it.

I guess I’ve found a solution. Just get rain. Lots of rain.
Water is going out the overflow pipe as I type.

I"m not following, how does that solve your leak concern around the pipe? The water is eroding all the dirt around your pipe too or it is just going through the pipe and the dirt around it is solid yet?

Setter, how often do you get this problem? Although not desirable, how often does it impact the integrity of the dam? Or does it?

What are the odds on you fixing the side and not creating another leaky spot? I probably would.

My pond recently filled for the first time in over 30 to 40 years. My overflow pipe finally lost its virginity.

To do it properly, you would have to dig it all out and start over.

If you’re worried, pump the water level down below the pipe and start over. If really worried, pump it down and put a sleeve around the pipe.

My comment was a bit sarcastic. I have water going out the pipe. The pond is full. I’m still planning on a repair, but not until the water drops down below where the pipe comes out of the dam. As long as it keeps raining like this, I will have a very full pond. I don’t think I’m getting any erosion. It’s seeping out, I don’t think it’s moving fast enough to carry any soil away.

My pond has been down for a few years. It would appear our drought is over. It’s difficult to say if the seep around the pipe is much worse now than it was 11 years ago. Maybe a little worse, because it had been dry for a few years. I do not think it’s effecting the integrity of the dam. At least I sure hope not.

SG,

Big rains are doubly a good deal for you. Obviously it is nice to get your pond to full pool.

However, it also gives you a chance to track your leak better! Did you ever get a chance to set a water elevation staff and set up a game camera on time lapse? If not, then you can still collect some valuable information just based upon your actual visits to the pond.

I would definitely mark the date and water level when your pond quits passing water through the overflow. Then measure your water elevation on your next trip, especially if you have had zero rain.

Also, I would start checking the area behind the dam as soon as the ground is dry after the latest rains. If you THEN find a wet spot, you are starting to figure out your leak path.

Good luck finding and stopping your aggravating leak, and congratulations on reaching full pool!

FR, I came up Sunday. I think it rained Saturday. Nothing since. The water is still right at the bottom of the pipe. So, it hasn’t dropped in three days. I generally just measure down to the water from the bottom of the pipe. I’ll be back Friday I’ll see if it’s dropped any. Possibly the soil has expanded back with saturation? I don’t know.
I’ve been on the tractor for the last three days. I just got down to the pond to jump in and cool off. Not sure of the temp, but 3” down it seems very cold. Ha! Reminds me of a Seinfeld episode. Haha!

Lol, some shrinkage is normal!

Speaking of, good clay shrinkage is what Im referring to, when it dries out it will shrink and you will have cracks, hopefully it has filled the pond up long enough, and kept adding a little to be able to get that clay swelled up to its full potential.

That crap gets tight as a drum when its dampened just right. Our old Missouri clay gets as tight as any of it around I suppose. its crazy the amount of ponds and lagoons I have messed with over the years, when you have a 40 yr old body of water and you get under the silt and scrape a few inches of clay off you are on solid, seems like almost dry, clay that you can barely tell its been under water for a week. you can literally drive a loaded dump truck across it.

It’s like concrete when dry. Our pond suffered from too much rock mixed in with the clay. Kind of made for a funny square shape to the pond. When they found good clean clay they took all they could. When they got into the rock they stayed away.
The clay is so solid, I really think if I’d have just left the drainpipe out, and let the spilllways do what they are supposed to do, I’d be fine. Water runs across places and doesn’t cut any clay away.

It’s like concrete when dry. Our pond suffered from too much rock mixed in with the clay. Kind of made for a funny square shape to the pond. When they found good clean clay they took all they could. When they got into the rock they stayed away.
The clay is so solid, I really think if I’d have just left the drainpipe out, and let the spilllways do what they are supposed to do, I’d be fine. Water runs across places and doesn’t cut any clay away.

Quick update. .3” of rain in the last 7 days. Water is still sitting at the bottom of the pipe. I do believe from all the heavy rains we received last week that the ground surrounding the pond is saturated. Probably some water still seeping towards the pond. Either way, this represents a significant slow down in the rate the water was dropping.
More rain in the forecast. Off and on for the next two weeks. It’s difficult to track the water drop with all the rain. Some slow some with runoff. Etc.
Happy Father’s Day to everyone.