I'm building a new pond by daming a creek. The engineering firm that surveyed and designed the dam structure used the stand-pipe system for claiming less maintenance, valves, and proven technology. We have an Ag exemption from the Corp of Eng for the pond as drawn using the standpipe system. We have a steady flow in the creek in addition to ~ 400 acre watershed into the creek. In 8 years I have seen the creek out of it's banks twice. Can a siphon system handle this? The dam is 112', < 25' high, ~5200 cubic yds estimated for construction. One of the 3 contractors quoting the job has suggested installing a Siphon System rather than a stand-pipe system stating the advantages of it being cheaper, less penetration to the dam stucture, and the availability to impound water (for duckhunting). Any advice on this matter?
Thanks.

Welcome to the forum!!! Glad you found us before any dirt has moved...We love new ponds construction threads....especially with lots of pics and a descriptive documentation.

A siphon system using equally sized piping will allow much more water to flow out by creating a lower pressure than a conventional system.

What surface acreage do you plan the pond to be? Given the size of your dam, unless the groung being flooded is a large lower area, a 400 acre watershed in a heavy rain event could wash out any earthen dam that small.

Personally, if I couldn't increase the pond size to at least 30 acres to handle the watershed, I would install both a siphon and a stand pipe, plus a huge emergency earthen spillway.

You made no mention of a large earthen emeregency spill way that can handle a 100 year flood, but if your engineers did not plan for one...fire them as that is job one!

Make sure you find a pond builder and not just a dirt mover. Any pond requires special construction experience and damming a year round creek with your sizw watershed is particularly dangerous if done improperly in any way.

Well put Rex. I agree with everything you said.. Please note I know nothing about pond construction

The NRCS worked closely with the engineering group for the design so I'm comfortable it's engineered correctly - even though it calls for a 72" riser pipe which seems excessive, but perhaps not with a 400 acre watershed. Either way, is that not what a spillway is for? Surface is spec'd out to cover 3.14 acres @ normal, 5.25 acres @ maximum level. According to the scale on the drawing the way I fiqure the Dam looks to be ~ 200' long planning for a 1:3 slope with an est 5200 cu yds of dirt to be moved. A Spillway is included in the plan 75'W X 23'L.

I agree with Rex - I would install both a siphon and a stand pipe, plus a huge emergency earthen spillway.

It is best to have a system that does not require a valve at the bottom of the riser. I have doubts about a 72 inch riser. We have a 16 acre lake with with springs and about 500 acres of watershed and only a 54 in pipe. It is huge and going down in it to mess with a stuck valve is no fun. It is closed and by-passed with a siphon now.

Wouldn't that be dangerous too Eric?

Not too much Cecil as the valve and outlet pipe are at the bottom. You usually get wet. Biggest danger is that someone up top might drop a wrench on your head when trying to open the system with the wheel. Other problem is having to climb down the wet ladder. Both are no longer a problem as it is by-passed now.

Ewest, Does that mean your conventional stand pipe system has basically been replaced with a siphon system? And if you could do it all over again you would have installed a siphon system?

Each lake is different. All have a siphon system. 2 have stand pipes as well. The one I designed has both with no valve in the stand pipe.
The stand pipe has a small (6 inch) directional pipe which flows first from about 5 feet under full pool. When that pipe is full then the separate siphon pipe will start. When it gets full the water will next go over the top of the 24 inch stand pipe.If the water goes even higher it will go out the emergency spillway. It goes as follows over full pool. First 6 inches out the directional flow pipe ,next 6 inches out the siphon, next 12 inches out the stand pipe and then the next foot + out the emergency spillway. The spillway has never been used even with a huge watershed and flow.




Here is a different one