Plug leaking farm pond?

Caver Dave

Caver Dave

Just holdin' it down here in BFV
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Mar 10, 2005
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Hooterville (24171)
After 6 months of wondering why our small spring fed (20+ gal/min) farm pond (40'w x 60'l x 8'd) wasn't staying full, after almost 3 years of running out the standpipe/overflow, we found the hole (5" dia). Oddly, it's opposite the dam, towards the upper hillside. Basically, it's running out as fast it's running in.

I guess locating the "leak" is the good news? Bad news is I'm not sure how to plug it...

Assuming some combination of bentonite, gravel, compaction???
 
Seriously, i'd probably lower the water level, backhoe or excavator to dig out where the hole is (so water wont just find a new path), and then pack in a load of clay dirt.

Relatively fast, relatively easy, and relatively cheap. If it doesn't hold, you got bigger problems. Like a cave.

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Can you see where the water is going or is it just going in the hole and disappearing?
 
awheelterd said:
Can you see where the water is going or is it just going in the hole and disappearing?
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The later... appears to be going back under the pond, as I can't believe it would run back UP the hill, but stranger things have happened!

McCracken said:
Muskrat?
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Could be, but we haven't seen any and pretty sure the dogs would go ape shit if one were to show up :D
 
This is called piping. It’s common on farm ponds built with whatever material and usually follows the path(s) of roots, mole tunnels, etc. It’s a maintenance nightmare.


Packing the hole with clay will kind of work. Problem is you still have a shear plane between the new clay plug and the surrounding soil.


I would find the hole on the upstream side and some how keep the water from coming in the hole. This can be plastic, plywood, etc. keep the water low. Aqua dams work well and are reasonably affordable. I would pack the hole with some TR30 bentonite chips. These are time release and gives you 30 minutes of working time before they start to react with the water and expand and seal it up.

Then on the water side of the hole, I’d try to create a cap with some fat clay. If the hole is 5” or so, I’d at least do a 2’x2’ area, maybe 8-12” thick and pack this in. You could mix in some bentonite but I wouldn’t think it too necessary. Maybe cap it with some 57 to keep it from slowly eroding away over time. Of course the size of the cap would need to adjust depending on actual conditions.


Aside from tearing out that portion of the dam and redoing it, this is probably your easiest and most affordable option. You could inject a bentonite slurry and fix it but then you start to add lots of $ for a contractor to come out and do this.
 
kaiser715 said:
I read it as it's on the bank of the upper end of the pond, not the dam itself?
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Correct... that's what really surprised me! I "knew" it had to be in the dam, just because and the backside of the dam is 6' tall with brackberries!

rockcity said:
This is called piping. It’s common on farm ponds built with whatever material and usually follows the path(s) of roots, mole tunnels, etc. It’s a maintenance nightmare.
Packing the hole with clay will kind of work. Problem is you still have a shear plane between the new clay plug and the surrounding soil.
Click to expand...

Given the shape/roundness of the hole, root or buried log would be my bet too.

We started shoveling gravel (57s) into it and packing with 2x4, then some larger rock + packing and the last 3-4 layers were packed gravel and red clay...
Started coming up immediately and has been hitting the overflow standpipe since early this AM.

Worse case is I have to stop the flow, dig it all back out, dump some serious packing into it, and start all over, but honestly the best part was finding it! I've searched for months and never thought it'd be on the uphill side...
 
I'm just really curious as to where the water is going/ending up after going down the mystery hole.
 
Caver Dave said:
Me too! :lol:
The creek (catches runoff for 7-8 acres on each side) is about 10'-12' lower than the full pond level and 20' away from the dam side, so guessing it was going there?
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We need pictures from multiple angles so we can all make our determinations :lol:
 
So, apparently my gravel/red clay "plug" gave way... :rolleyes:

No pics looking INTO the "hole", but it's definitely the "leak", it's almost perfectly round at the surface (like the logs/roots @rockcity eluded to) down 1' or so then appears to branch over/above a rock fissure(guessing?)... because the water HAS to be going UNDER the rest of the pond to somewhere on the dam side and/or into the creek which catches the runoff?

Since, the prescribed TR30 bentonite could be "pouring $$ down a hole" ($80/50# and no guestimates on how much would be required), gonna give it another shot...
The 2x4 was a little too big & light for tamping, so I got a nice 18# digging bar... thinking the chisel end should tell me exactly "what's" under the hole (rock/clay/etc.) and the upper 3" dia. flat end should be more effective for tamping. Going to try alternating layers of 57s to "fill" the bottom, then smaller "pea" gravel to fill it further, and then either some clay or some type of cement... figuring worst case will be having a mini-ex come dig it all out and repair with non-organic fill?

Upper/Road side of pond looking towards dam
20200905_081122.jpg

Lower/dam side from looking up to road
20200905_081045.jpg

Dam side (from overflow) looking across to "hole" (under visible rock just down from high mark)
20200905_081022.jpg

Road/hole side looking straight across to overflow
20200905_081211.jpg
 
I wouldn’t put a washed stone in there. That’s not really doing anything to stop a leak as it has too many voids to let water percolate through.

I’d get some fat clay and mix in some bentonite and pour it in and tamp and repeat as much as possible. The clay and bentonite should work together to seal up any holes. Once the bentonite gets wet and expands, it should fill and small missed voids.
 
Fill it with Tannerite. I've heard it packs down nicely. Then shoot it. :sniper: No more pond issues :D
 
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