Just wanted to give you folks an update! Thanks for your replies. I finally got my pond drained and the valve that was in place was an armco 12" slide gate valve, it was perfectly preserved with no rust or deterioation at all, it had been coated with tar so I plan to use the same valve.
As for as cutting a swell at one end of the dam, it would present a whole new set of problems ( check out tropical storm BILL he plans to be around for a few days dropping tons of RAIN) I currently have a 40' long cement wall at one corner of the dam for an emergency overflow and enough freeboard space on the dam to allow the wall to work perfectly when needed. I know in Indiana you folks don't have to prepare for tropical storms or hurricanes but on the Gulf coast it pays to be prepared, and sometimes maybe over prepared!!!!!!
Thanks again for your advice!!!