Dam Failure - Any Suggestions?

[justinramani]

An acre pond ~5' average depth is only about half the water you think. About 1.6M gallons.

A 100' roll of 6" solid drain tile is ~$100. That would flow alot of water. About what a 4" trash pump would but would consume no power.

If the water is close enough to where the discharge is gonna be, you can cut that 100' roll in half and have two siphons going. At ~25000 gph each, and two of them going....should be able to lower the water level about a foot every 6 hours.

The only issue with plastic tile is that it floats. SO you will need to do something to hold the end under the water.

I have seen several others suggest/ask, but never seen a response. What does the pond have currently, for overflow protection?

Right now the pond has an 8 inch overflow pipe. Looks like the pipe got clogged during the storm, which caused the water to surge over the dam. I know that the dam was not constructed propel now - its pretty evident based upon this failure. It was installed a long time ago by a previous owner.

 

[LD1]

Well, they must have done something right if it was indeed constructed "a long time ago".

Nothing last forever without upkeep. It seems perhaps everything would have been fine if the overflow didnt plug up?

HAve you cleared the overflow yet? and let that 8" pipe drain the level down at least to where it should be? That single 8" should flow as much as a pair of 6" pipes.

 

[Gary Fowler]

That is the reason pond construction in my state doesn't allow for a pipe overflow. They claim (and quite correctly) that a pipe cant be sized to handle unexpected overflow conditions. The overflow must be constructed on the upper end of the pond and a drainage channel built to channel the water around the pond dam toward the lower elevation end. When constructed correctly, the pond can fill to within inches of full dam height and then water will flow out the overflow from the high elevation, around the side of the pond and out thru the overflow channel. This might just be a grass covered swale or if the pond is larger, a rocked in swale to prevent erosion.

When we bought our property, there was 2 ponds already on it with pipe overflows. Large rains would wash over the dam creating erosion on the dam that had to be repaired several times. We decided to raise the dam height (during a drought that almost dried up the pond) using dirt from digging out the pond. We raised the dam height by about 2 feet, then added the state required upper elevation overflow. We kept the 12" overflow pipe that starts running when the pond reaches about 14" from top of dam. When that pipe cant handle the flow from heavy rains, the upper end overflow will start discharging when the water level reaches about 4" from flooding the dam. It is wide enough that only during super storms have we had a breach on the dam. I rocked the area that floods during one of those 100 year rain storm so if it does overflow the dam, it doesn't wash any soil out.
The overflow runs about 20 feet from the bottom of the pond levee and at times it looks like a small river running down thru my lower portion of lawn. So far the grass keeps it from washing.

We had another pond constructed per state requirements and it has no pipe overflow only the swale from the upper end. We came back after the state inspection and raised the swale overflow elevation about 3 feet so the pond would fill up more. The swale is about 20 feet wide so it will handle a lot of water. The pond has never overflowed the dam and the resting level is only about 6" below full capacity.

 

[justinramani]

Well we were able to get the over flow pipe unplugged, which is helping quite a bit. I also got a 4 inch pvc siphon going. I'll probably end up putting together another one this afternoon. Hopefully we can get the pond safely drained in a few days.

 

[dmccarty]

Well we were able to get the over flow pipe unplugged, which is helping quite a bit. I also got a 4 inch pvc siphon going. I'll probably end up putting together another one this afternoon. Hopefully we can get the pond safely drained in a few days.

That is great news. We did not get the rain that was forecast yesterday but it looks like there is a bit of rain out there today so hopefully you can get the pond drained to a safe level soon. The siphon was a great idea from the TBNers. :thumbsup::thumbsup::thumbsup:

The latest weather model says we have about a week before that low/Hurricane gets near NC. Hopefully, the model is wrong and that storm heads out more to the east. Hopefully, in a week you can drain that pond to a safer level.

Ironically, I drive by an old farm pond that is maybe 20 feet above a high way. The farm was sold long ago and houses are now being built which has caused quite a bit of run off and other issue. A year or so ago I saw water running over the top of the dam. :shocked: I called up the state dam engineer and he went out to have a check and that problem was fixed. If that dam had failed a major north/south road would have been destroyed which would have made travel a HUGE mess.

I noticed yesterday there was a couple pallets with bags and some other stuff dropped off near the dam. This morning they had guys about to start doing something. I am wondering if they were going to be putting in some bentonite. The dam is in a curve so it is hard to get a good look but it sure looks like there is water leaking at the bottom of the dam. :shocked:

 

[ultrarunner]

The problem around here is ponds silting up with heavy rain... several local ponds are just about no more...

They can be fine for years but don't handle days of rain well...

 

[justinramani]

That is great news. We did not get the rain that was forecast yesterday but it looks like there is a bit of rain out there today so hopefully you can get the pond drained to a safe level soon. The siphon was a great idea from the TBNers.

The latest weather model says we have about a week before that low/Hurricane gets near NC. Hopefully, the model is wrong and that storm heads out more to the east. Hopefully, in a week you can drain that pond to a safer level.

Ironically, I drive by an old farm pond that is maybe 20 feet above a high way. The farm was sold long ago and houses are now being built which has caused quite a bit of run off and other issue. A year or so ago I saw water running over the top of the dam. :shocked: I called up the state dam engineer and he went out to have a check and that problem was fixed. If that dam had failed a major north/south road would have been destroyed which would have made travel a HUGE mess.

I noticed yesterday there was a couple pallets with bags and some other stuff dropped off near the dam. This morning they had guys about to start doing something. I am wondering if they were going to be putting in some bentonite. The dam is in a curve so it is hard to get a good look but it sure looks like there is water leaking at the bottom of the dam. :shocked:

Yeah - I'm really hoping that the rain holds off for a while longer. My wife and I were never fans of the dam or the pond - so we aren't to sad to see it go. We just want to make sure that the pond water is released in a controlled and safe manner.

 

[justinramani]

Here is the siphon pump that I built - it took about four trys, but it finally started working - quite well I might add!

 

[dmccarty]

Here is the siphon pump that I built - it took about four trys, but it finally started working - quite well I might add!

View attachment 483103View attachment 483104

Impressive!

Did you use the the clean out to start the siphon?

Later,
Dan

 

[rekees4300]

Does anyone have any ideas that might help us get out of this situation?

FWIW - If you decide to keep the pond, I would strongly suggest an emergency spillway be constructed to prevent the topping of the dam (no matter how much it rains) in the future. Do not rely on an overflow pipe only. The level of the spillway should be between the overflow pipe and the top of the dam.

 

[justinramani]

Impressive!

Did you use the the clean out to start the siphon?

Later,
Dan

Yes - I capped one end and filled up the pipe using the clean out. Then I closed off the clean out and removed the cap from the out flow side. I got another one set up and working this evening...

 

[MossRoad]

Nice! I really like siphons. Its about as simple and elegant as you can get.

 

[justinramani]

Nice! I really like siphons. Its about as simple and elegant as you can get.

Question on the siphon - can I just keep adding pipe to the end of the side that is in the Pond without affecting the siphon (not needing to re prime it). Will it matter if the end that is in the pond gets longer than the amount on the discharge side?

 

[4570Man]

Question on the siphon - can I just keep adding pipe to the end of the side that is in the Pond without affecting the siphon (not needing to re prime it). Will it matter if the end that is in the pond gets longer than the amount on the discharge side?

Not as long as the pipe you add is full of water and the discharge side stays lower.

 

[Streetcar]

You can add pipe to the suction end. The discharge end must be below the water level in the pond for the siphon to work
Siphon will automatically stop when discharge is the same level as the pond surface

 

[justinramani]

I would like to thank everyone for the help. A few days ago I felt helpless - now I have a plan in place to get things under control - thanks TBN nation!

 

[MossRoad]

Question on the siphon - can I just keep adding pipe to the end of the side that is in the Pond without affecting the siphon (not needing to re prime it). Will it matter if the end that is in the pond gets longer than the amount on the discharge side?

Yeah, as others have mentioned, its the level of the pond that has to be higher than the discharge for it to work.

Let's say the pond is 10' deep when full. And you can discharged at a level on the other side of the hill that is only 5' lower than the surface of the pond when full. You could put the inlet pipe on the bottom of the pond, which is 5' lower than the discharge, and it will siphon. But the siphon will stop itself once the pond surface drops to the same level as your discharge. You can only drain its surface to the level of the discharge. Then, you'd need to find a way to make the discharge lower or you'd need a pump. Make sense?

 

[MossRoad]

I would like to thank everyone for the help. A few days ago I felt helpless - now I have a plan in place to get things under control - thanks TBN nation!

Ha! Sounds like a man with a plan! Good luck and send more pictures. WE LOVE PICTURES!! :thumbsup: