Pond Boss Forums POND CONSTRUCTION Building a dam Epic Dam Fail

Last fall I built a dam for a 1/4 acre or so pond near my yard, which was to serve as a grow out pond for fish to be added to my big pond. I put the finishing touches on it this spring. In all that time we had little or no run off so it sat basically empty. Thursday night we had 3.5 inches so I was delighted to wake up and find it full (though it was mostly muddy water and cornstalks). The dam was holding, though I needed to raise the water level a little which I could easily do by adding to the stand pipe. Then Friday evening we got two more inches of rain in 45 minutes. Here's what I woke up to find Saturday morning.

And here is a view from the back.

I can't say that I was terribly surprised. I am trying to make a quarter acre pond fed with about 50 acres of run off. The white pipe was meant to control the level during light run off. It also has a gate valve so that I can drain the pond every couple of years to clean out sediment from the neighbor's field. In the second picture you see a 30'x10" plastic culvert. It was meant as the overflow after the stand pipe. It obviously couldn't handle this amount of water and when water started going over the dam it was washed out and ended up about 300 feet downstream. My other problem was lack of a proper spillway. I didn't have a transit/level and kept procrastinating about going off to rent one (I have on ordered now) and so the lowest part of the dam was the middle over new dirt instead of off to a side.
I'm not real upset about this and fortunately there were no fish in it yet. I plan to make the dam thicker, add another culvert for an overflow and a properly sized and located spillway, plus a few other improvements I could see needed to be made. Maybe this small of a pond with this much potential water shed is asking for trouble.

Can you build a "run around" or emergency spillway over to one side?

That's what I am going to try to do. I kind of thought it was, but since I was too lazy to go rent a transit, I learned the hard way that it wasn't.

Interesting pictures. I'm sure that if you don't mind, these will be archived and used to educate other dam builders/owners. Things like this have happened to all of us.

An idea. No need to cut a spillway. Reinstall the correct pipes there. Graduate the hole in the dam over the pipes and compact well. Put in a liner and put rock and concrete there as the emergency spillway.

Seep collar as well?....

Bullhead...
From your pictures, I see good rich black farmland in your dam, but no clay. Even with an overflow pipe and a spillway, I wonder if the water won't eventually work its way through the black dirt and cause a failure. The guy that build my dam went to great lengths to cut a "key" deep below the waterline and pack it with clay. That clay seam carried through all the way to the top of the dam. Your pond is a lot smaller, but there should be some guys on the forum who could give you an idea of how much clay should be in a dam your size.

Get1fiddle,

I was thinking exactly the same thing -- black dirt but no clay. The core trench and the front side of the dam should be well compacted clay.

Ewest sounds like he is suggesting putting in the emergency spillway over the top of the principal spillway pipe. I would be very surprised if an engineer would recommend this. It looks like your site would have an opportunity to put the emergency spillway around the left side of the dam. In my discussions with engineers, they prefer to have the emergency spillway as far away from the dam as possible.

Bill

That is so they can control where the dam washes out. Not the case here. If done correctly it should work fine. But you have to able to get the max flow over it without washing.

The only black ground on this place is where I change oil in the tractors. Believe me there was a lot of clay in the dam. The alluvial plane you see in the top photo is a bit misleading it was all loose soil that washed in from my neighbor's bean field. In the second photo note that to the left and right you see ground that was worked but down the middle is clay as hard as a hiway. I think another factor was that the dirt I had built the dam with was so dry it wasn't very cohesive. It was a pile of dry dirt in the shape of a dam.
No, I didn't have a seep collar on. I kind of spaced it off when building it. I'll add one now.
Sure Bruce, archive this thread. If for no other reason, at least I can be immortalized for my futility.

Definately EPIC my friend.. Sorry I kinda chuckled when I looked.. Atleast like you said it wasn't full of fish and YOUR not to worried about it, so live laugh and learn..

If someone hasn�t made any mistakes then in all likelihood they haven�t gotten off the couch to try and accomplish anything.

Eric, I never make a mistake. However, I have had quite a few experiments that gave other than expected results.