Hi! Couple years ago I bought a house with a nice bit of property in Westchester County, NY, including two ponds (I think about 0.5 acre each). The lower pond has a stone dam - it looks like a dry stack stone wall with a sluice gate in the middle.

Over the last 8 months or so, we’ve at 4 or 5 storms that have send the water level soaring, and water is pouring over and through the dam (not just through the sluice). I am now seeing some of the rocks bulging out where water is pouring through and am concerned that the dam will soon burst.

I’ve been googling in search of a company that can repair the dam but I can’t find anyone. Stone masons I’ve found don’t seem to do water, and pond construction companies I’ve found don’t seem to do stone. Any suggestions?

Thanks!

No advice at all about a stone dam. I personally have never heard of such a thing.

However, I would get the water pressure off of the dam ASAP to mitigate the damage.

Probably the easiest way would be to get some siphons running. There are videos on the internet for starting siphons with inexpensive corrugated plastic drain pipe.

If you can drain the pond low enough to get the pressure off of the dam, but still have enough water in the bottom to save fish?, then you can examine the dam and get the right kind of contractor to perform the repairs, hopefully.

"Dry stack stone wall" = no mortar (in my mind).

Does water normally (i.e. NOT when you are having storm events, just when the pond is sort of full) leak out between the stones?

"I’ve been googling in search of a company that can repair the dam but I can’t find anyone. Stone masons I’ve found don’t seem to do water, and pond construction companies I’ve found don’t seem to do stone." That seems like it ought to be true. Worst case, do you want/need the second pond enough to completely reconstruct the dam?

Thanks for siphon idea. Found some videos and am going to try that as a stopgap.

Yeah, no mortar. I think there had to have been mortar at some point, but this thing is likely 50+ years old and the mortar probably eroded.

Under normal conditions, water comes out the bottom of the dam in a trickle, not too bad but it does seem to have a noticeable effect on the pond level during dry summer months.

I think we do need to save the pond. It’s right in front of our house and thus is a major part of the view from the house. Plus, my wife has fallen in love with the koi in the pond…

Moments like this make me want to move back to the city!

Do you typically have so much water that a "slightly leaky" dam still holds the water level of the pond at an acceptable level?

If so, perhaps you can do the repairs yourself, if it doesn't have to be perfect.

One improvement compared to 50 years ago, might be to add a vertical strip of pond liner material behind one of your courses of stones. Perhaps that would lower your leak rate and make the stones less likely to shift if the dam is mostly holding equal pressure across the face.

Also, if you are considering a siphon, then you might consider a permanent siphon. That would be useful for your short term problem, would allow you to mostly drain the pond for your dam repair, and give you more pond outlet capacity as some protection against future big rains.

Here is a link to an automatic siphon system so you can see the concept.

Siphon System with automatic level

P.S. If you can send pictures, then some of the actual construction experts on the forum might drop into your thread with some good advice.

Pics would help, but consider drawing the pond down and using hydraulic cement to seal the wet face of the dam - a tuck-point job, so to speak.

Like others have said, pictures would help tremendously, I am having a hard time picturing just what you have going on, it would take a pretty wide, substantial block dam to withstand much water pressure.
Pictures can be a little cumbersome to get to show up on the site tho till you get the hang of it, there is a thread or two on the subject, look for the more recent one as it changes a little from time to time.

You are hosed. Any real fix would mean draining and sealing. But wife likes the koi and when mama ain’t happy, ain’t nobody happy.

just a thought. Not knowing the whole situation. Maybe drain pond down far enough to keep fish happy and sandbag an area needing repair?