Omahah, go to a topographical map of the area, look at the elevations. Find the elevation that the pond is at now, add 5' to that and look back up and out to the sides of the drainage for that level. Then try and trace around that rough area using google planimeter to give you an area.

Digging the silt out will be a job for an excavator. Do you have a place to dispose of it? What you're planning is feasible, providing you have good dirt for the dam and a way to compact it. I'd do some searching to see what the state/county says, and try and figure out what would happen if the dam were to give way. Would the road wash out?


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