Dam Failure - Any Suggestions?

[PILOON]

Don't know in your area but environment people can get very fussy about dams.
If you have any quantity of large rocks around I'd dump them downstream to control water flow as a minimum precaution.
In my area a person would be wide open to lawsuits for any downstream damage and the environment guys would force all kind of engineering studies prior to a repair.
If you do decide to drain be sure it is a controlled flow so as to prevent downstream damage.

 

[MossRoad]

How much of a drop is it from the pond to the other side of the road? You could siphon it out for cheap if its just a few inches lower. No pump needed.

 

[justinramani]

If that's your road the water is running over, who ever built it did not put in (or size) the overflow properly. With a pond (and water) you need a plan "B" to handle too much flow for plan "A", your pipe.
Water should never flow over the berm/dam.

No, this is the dam that is upstream of our road. If the dam goes - our road won't be able to handle the surge. I'm guessing that a 1 acre pond is about 3 million gallons of water....

 

[justinramani]

How much of a drop is it from the pond to the other side of the road? You could siphon it out for cheap if its just a few inches lower. No pump needed.

It ranges form about 2 feet in some areas to as much as 15+ feet in other areas.

 

[justinramani]

Doesn't your pond have an overflow? In any case a 4" trash pump at approximately 24K gallons/hour will take 65-70 hours of continuous pumping to completely drain your pond.

I'd be very careful about any type of overflow trench. Chances are the water will erode the trench and you might end up with a big gulley. Might be better to get some 6" plastic pipe & elbows and make a siphon over the dam. This will drain the pond without the chance of washing out the road.

I saw a video showing people using the 4 inch black pipe to create a siphon. Will that work too?

 

[MossRoad]

As long as there is just a slight drop in elevation the siphon will work. The more drop, the faster it'll run.

There's lots of videos about siphons and just how fast they work.

Try and get the outlet as far below the height of the pond surface as possible. As long as you don't have to go over a hill that's more than about 30' high, it will work if there's only an tiny difference(like even a fraction of an inch) from the surface of the water being drained to the opening of the outlet tube (the height has something to do with the barometric height of the liquid... if it gets too high, gas bubbles get pulled out of the liquid, form a bubble in the high spot in the pipe and break the siphon effect).

 

[roadhunter]

Start siphoning the pond off to lower the level and install Rip rap/cloth on other side of the road below a large culvert(s) that crosses under the road should be the first project IMO. You should be able to use collapsible pipe for siphoning. I've had them siphon after turning pumps off on many occasions. Withe the drainage system in place you could dump more water with additional hoses or a rental trash pump. Once the water in the pond is lowered you can install a proper overflow device of your choice and repair the dam. Then when you are finished you should be able to control the water level as well as protect your road.

 

[hosspuller]

I have a dam too. Your overflow is missing or has been blocked. I also say get a siphon going Now to reduce pressure on the dam. Do not dig a trench. You'll not have any control. 4 inch pipe will flow water but remember the area of a pipe increases by the square of the diameter. A 6 inch pipe has 28 inches of area while a 4 inch pipe has only 12.5 of area. A 10 inch pipe has 78 inches of area. Two 4 inch pipes still doesn't equal a single 6 inch pipe.

A simple siphon can be built using a plug, a length of flex pipe. lay the flex pipe over the dam. Plug the lower end. Fill the pipe with water and hold the uphill end under the surface. as deep as you want the level to be without sucking debris. When you remove the plug on the lower end, water will flow. any time you wish to stop the siphon just raise the suction end to the air. You won't be able to get a plug into the lower end against the water flow.

 

[Streetcar]

Start siphoning the pond off to lower the level and install Rip rap/cloth on other side of the road below a large culvert(s) that crosses under the road should be the first project IMO. You should be able to use collapsible pipe for siphoning. I've had them siphon after turning pumps off on many occasions. Withe the drainage system in place you could dump more water with additional hoses or a rental trash pump. Once the water in the pond is lowered you can install a proper overflow device of your choice and repair the dam. Then when you are finished you should be able to control the water level as well as protect your road.

The pond side of the siphon must resist the suction forces. The downhill side can be a collapsible pipe

 

[LD1]

No, this is the dam that is upstream of our road. If the dam goes - our road won't be able to handle the surge. I'm guessing that a 1 acre pond is about 3 million gallons of water....

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?