Pond Boss Forums POND CONSTRUCTION Building a dam Old dam, resurfaced and leaking

I have an old dam (probably 75 plus years old); 70 ft wide, 12 ft high,6ft wide at bottom, tapering up to 2 ft wide at top; solid rock and mortar; has created pond 70ft wide by 110 ft long in rock canyon. We have resurfaced the inside of the dam with 3" of cmt/mortar; it is almost full with recent rains and we have a leak (gal per minute). Can I sprinkle some bentonite or cement down the inside face of dam; will the bentonite 'find' the leak and seal it off.

I have never had either luck or skill at using bentonite. I would think there is some kind of waterproof mastic or something that would work better.

I'm with Dave. Never been able to buy/find that magic bentonite. However, if you knew where the leak was on the inside....it might just work depending on if the leak is in a small area. If you do find a magic bag please share your source : )

Is this a concrete dam?

Can you see where the water is comming out?

Sounds like you could drill a small hole on the backside of the dam just deep enough to connect a fitting to it and then pump in some kind of sealant.

No experience with this just thinking out loud.

The dam is mostly volcanic rock (8" by 12" blocks, irregularly shaped)cemented/mortared in place; approx 6 ft thick at bottom, tappered up to 2 ft wide at top; 60 to 70 ft wide and 12 ft high); it leaked in places, so we resurfaced the inside face of dam (layed out heavy fencing type material...goat fence type...as rebar, and then layered on a 4" thick facing); now the pond in nearly full, and there is a 1/2 gal per minute leak coming out of the face...baseball sized leaking area, approx 1/2 way up the dam, and approx 3/4 of the way across; can't tell for sure if the leak is coming straight thru the dam, or if it is seaping and channeling from somewhere else; my first idea was to sprinkle some bentonite or cement down the inside face, and hope the material flowed or got sucked into the flow channel and would help seal the leak; have a feeling that as the pond sits, that moss, algae and mud will eventually seal it off.

I have no experience with your type of dam but would doubt that moss, algae and/or mud would seal a leak of that size.

Other than draining to find the specific leak, I don't have a clue what to do.

Half of a gallon per minute is not a lot. Maybe just keep an eye on it.
But if you do anything --- I would do more than sprinkle, Put it on thick.