Farm or Recreational Pond Design 1

[fivestring]

While I have designed many ponds for storm water control such as detention/retention ponds, I have been asked for the first time to design a pond for recreational purposes. It is basically a small farm pond in extreme northeast GA (silty clay soils) in which the owner wishes to stock with trout. I don't want to make a huge deal out of it as farmers over the years have basically just been doing this themselves with no design. However I want to do it technically correct. I am familiar with the environmental permitting as that is a whole different matter. Most of these recreational ponds are killed by the permitting before we get to the point of design. This one isn't dead yet.

The dam will be about 12' high and the water surface will be around 1/2 acre. The owner was told that since it will be built on a trout stream, this pond has to be a "cold water release". I'm assuming that means that the water going out of the pond has to be the same temperature as the water coming in. I have discussed this with the local NRCS extension service and they recommended a type of siphon system to pull water from the bottom of the pond.

I have seen some technical data available for small dam design but it seems to be for much larger dams than what I have. When we design storm water ponds for development, we do not specify the dam grading to be any different than the rest of the site. But I was wondering, due the use, would a certain specification be applicable? Would there be any need for a pond liner? Does anyone have an opinion regarding the outlet?

Any assistance would be much appreciated.

 

[beej67]

If he stocks it with trout and they all die off when the pond goes dry in the next drought, he's going to call back you with angry words. The checks to ensure against that are fairly simple.

Test the soil for hydraulic conductivity. I would spec a clay core in the dam if your site soils are more on the silty side than the clayey side, and an anti-seep collar on the pipe through the dam. Old SCS ponds often had clay cores in their berms.

I would look at the watershed going into the pond, and do a water balance analysis on inflows and outflows, taking into account evaporation and any farm withdrawals he may want to do. If it's to be set above the groundwater, then you need to take infiltration into account as well with this water balance analysis. If it's down near the water table, don't worry about infiltration. I believe there's a section in the Blue Book on water balance calcs, start there.

Then check 100 year freeboard / etc, but it sounds like you already know how to do that pretty well.

Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East -

http://www.campbellcivil.com

 

[fivestring]

Thanks for the heads up on the water balance. I'm familiar with that. This stream does have decent flow, though, from a spring. I'm afraid the trout will die, regardless.