Well here is the latest from the local SWCD folks:
I again talked with our engineer, and I also figured the acres of watershed for your pond. So with not being at your pond site before, the numbers are rough estimates. I came up with 32 acres of watershed for the pond. From that ran some numbers and the CFS (cubic feet per second) for the watershed for a 2 year storm would be 23 CFS, and for a 10 year storm around 47 CFS. So with that being said the 18” diameter pipe you currently have installed in your pond would carry the normal 2 year storm with anti-vortex hood. However you would have the need for an emergency spillway as we discussed earlier on the phone in the event of a larger storm. Also I would recommend extending the existing pipe further without any angles because the angle would cause a reduce of flow in the pipe. There would also be the need to increase the elevation of the dam to meet the required head pressure for the 18” pipe to flow full (which we talked about on the phone). See attached for hooded inlet drop structure form to better explain. Again the numbers are rough estimates. I will try to make it out to your pond site around 10:00 if that works for you.
