Won't happen if you trench the length of the lower end of the area as I now do. With the cost the state paid for this project, I think they could have done this easily.
I am no rocket surgeon, but it seems to me that sealing a pond or wetland would be exceedingly difficult with a previously installed outlet pipe!
Since the state people probably helped advise the farmers on installing the drain tiles a generation ago, you would think they would at least have "Check for drain tiles." on their pond job planning sheets.
I am glad to hear you found the tile in the basin of your wetland. I suspect packing it with clay should be effective in sealing it completely. Especially if there is less than 10 feet of water on the tile when your wetland is at full pool.
Hopefully you will have a multitude of happy wetland creatures by the end of next spring!
