In my real job we always have "safety margins" - so you don't have to rely on luck.
If the bare minimum is 1/20th of an acre and 4' deep in our region, I was planning to go a little larger on the surface dimensions and 6' deep.
Hopefully, you can expand the dimensions of your sediment pond a little when you are finally forced to dig out the silt. That way you will have lots of FHM to keep your gamefish fat and happy.
