Been snooping on this site for a while. Glad i found it.

Started on a new project and wanted some feedback on outlet structure size.

10-12 surface acreas of water when finished
400-450 acre drainage area

primary spillway: 8x6 concrete inlet box into a 48" pipe through the dam.

there will be a secondary spillway but woudl like to depend on primary 99% of the time.

Does anybody in this part of the country have experience with this drainage area or this size outlet.

With that size BOW and covering that large of watershed I would imagine the Corps of Engineers will want to have a say in it and they will have their own requirements and will probably want to be smack dab in the middle of your plans.

I know I'm not giving you the answer you wanted, but in Kansas once you get past a certain surface water area, water holding capacity and drainage area, there suddenly gets to be a lot more agencies interested in your project than your local NRCS guy.

Maybe a warning as much as helpful information.

Hi Mac, Welcome to PB!!! You will get good advice here by others. It just may be a bit slow because of the holidays, give it time.

There are many members that have a large pond like what you plan. You will want to hook up with some of them for advice, especially if they live in your area. They would have a better idea on what hoops you may have to jump thru. Like snrub mentioned, you may want to tread carefully until you get some advice thru members who have been there.

Not looking to attract any attention, the pond was already there at one point in time and failed. Just wanting to correctly re-establish to prevent furture failures.

Gotcha . I know in many areas, if its not upkept it falls back to naturalization. Best to keep working on it to avoid it being "reclaimed".

I think you have the right idea, the main outflow is used most of the time. The second one(emergency spillway) is for those rare 100 year floods. I don't know who you would contact to find out the proper watershed to overflow pipe size, without raising to much hackles.

What caused troubles for the pond to be in the shape it is in now?

Possibly Ewest will be able to help. I think he is somewhat close. Might try PM him if he don't chime in here.

from looking at it they tried to run all that water over the top of the dam (soil) as the primary spillway. thats way to much water to do that. They also didn't core the dam and the material they used was questionable at best. lots of organtics and rocks in what i have inspected so far. putting all that togeather that makes me question their ability to constuct a legitimate dam. my guess is was someone who rented or borrowed some equipment and thought it sounded fun to build a dam, without the knowlege to do so.

Thanks,

400 plus acres of drainage into 10 or 12 acres, you will sure want a lot of free board between drain inlet and spillway. As bad as I hate opening up a can of worms, I would suggest that you visit with your county soil and water district

Welcome, Mac15. While this is not my area of experience, I have to agree that your drainage area sounds awfully large for the size of pond involved. If there was no other water control feature other than letting it overtop the dam, that overflow standpipe may well make a big difference when you rebuild. I would think you'd want to ensure that you have a very capable secondary spillway to handle heavy rain events, one that is sufficiently constructed to withstand a potentially high volume of water flowing over it for an extended period.

Be patient and some others will come along who have plenty of experience to offer you some insights on the project. Do you have any pictures of the area you could share? How about aerial/satellite photos or topo maps?