Plugging a leak in EPDM

[Whistling Badger]

Hi, everybody. Haven't been on the forum for a while because, ironically enough, I've been too busy working on my pond.

We put a new 45 mil EPDM liner in my big irrigation pond this past spring, and I am working on covering it with stones--it's about 3/4 done. Right now, there's only about a foot of water in the bottom, but I plan on filling it back up soon. For the first time in a decade or so, this thing's going to stay full!

Except..Big Problem. Today I noticed a long stream of bubbles coming up from the bottom. I did some feeling around (this is under a foot of water, and mostly covered with rocks, remember) before I found the hole. At a guess, it's about 1/8". Right in the very bottom, in a little space between a few big rocks. Oy.

It has to be plugged and/or patched, of course. And because the hole is in the middle of a very big liner mostly covered with a dumptruck load of stones, whatever patch I do will have to be done in-place.

I have EPDM tape, primer, and liquid rubber that would take care of it, no problem, except that there is ground water under my liner that I suspect will well up through and keep the patch from curing properly. I'll try, but I fear that's a no go.

So, here's what I'm wondering: What if I just got a big bag of good-quality, expanding bentonite and dumped it into the space between rocks? Anybody ever try this? Any suggestions?


Thanks--Tom

 

[addy1]

I have never used it, but that seems like a viable fix. @Meyer Jordan he may have a solution.

 

[Lisak1]

Hmmm... Do you suspect a puncture or a tear? I think your idea would work for the first scenario; not so sure about the second.

 

[Whistling Badger]

Lisak, I don't know if it's a puncture or tear. It is a small hole, though--I could plug it with a fingertip. Why would it matter?

 

[Meyer Jordan]

Do you have any idea as to the hydrostatic pressure under the liner? In other words, how fast is the ground water infiltrating the pond through this puncture in the liner? You likely will not be able to determine this until the pond is completely drained, which you will be required to do to repair the leak.
If it is only a slow seepage, a simple patch should work. It should cure properly if weight is applied to the patched area, such as a large stone.
Benonite will not work in a situation like this as it would be subject to being redistributed around the bottom of the pond by water movement.

 

[Whistling Badger]

No idea what the pressure is at the moment, MJ. It varies wildly, anyway. I have irrigated hayfields for a mile or so in every direction, and the groundwater in the pond varies from nothing in winter and late summer, to very high in june and early july--it all depends on how much rain and how much irrigation is going on. My fear with using a patch is that the tape won't stick and the liquid epdm won't cure if it's wet. If there's even a tiny dribble coming through that hole, I don't see any way to keep it dry long enough to patch it. And the liquid EPDM won't cure if it's wet--the instructions say not to use it if rain is forecasted that day.

What if I cover the bentonite with stones to help it stay put?

Either way, I'm going to have to go ahead and fill the pond. The pressure from beneath is pooching the liner out between the rocks so hard, I'm afraid it's going to burst if I don't get some water on top of it. I'm afraid to walk on it any more--in fact, it's so unstable that I'm pretty sure my walking over the stones is what pierced the liner in the first place. Makes me wonder how many more leaks I have...

I'll probably try the bentonite and hope MJ is mistaken--not sure what else to do. If I can figure out a patch, I'd rather do that. Wish me luck!

 

[Meyer Jordan]

Exactly how large is this pond? Is it going to be strictly for irrigation? It would certainly be an sizeable expense but I would consider backfilling the pond with high clay content soil and incorporating Bentonite across the entire ponds bottom.
What you state about keeping the leak area dry before patching is an obstacle. It would seem that the only time that this could be effectively done would be during the Winter months when the water table is at its lowest.

 

[Whistling Badger]

I think you might be right, MJ. It is about 50-60' across, and about 6-7' deep in the middle. It is lined with 45 mil EPDM. Pulling that out and backfilling with bentonite is not an option. The puzzling thing is that our soil is solid--I mean SOLID--clay. But the thing has never held water on its own--we tried for several years, thinking it would seal itself. There must be a gravelly layer down there somewhere.

I went ahead and dumped a bag of bentonite over the leak, filling the space between the boulders that surround the hole; I then covered it with a good cairn of stones, both to keep the bentonite in place and to hopefully be able to find it again if the opportunity and need arises to expose and reseal it with a patch--something I would very much prefer to do. We'll see how it goes. Usually, at haying time in the mid-to-late summer, there is a month or so with no irrigation and very little rainfall. I might try it then. We'll see how it goes.

Thanks for the input, the three of you. Tom