I've got another thing to ask you guys. He wants to use three six inch culverts through the dam at the top and go down the back under ground to the bottom of the dam instead of using a twelve inch as he planed in the beginning
The idea to distribute the outflow amongst multiple principal spillway pipes makes sense in as this allows "back-ups" if one becomes clogged...particularly during a gulley-washer. The issue then becomes focused on each pipe to determine it's potential to become clogged. If there are no trees around the pond (leaves, sticks) or any other potentials for obstruction, I imagine 6" splillway(s) can be reliable....? Is it possible for one fat Cat to plug the hole? (I'm having issues with the 6" pipe...maybe it's just me.)
The opening of one 12" spillway is 113 sq inches. Three 6" spillways is 85 inches.
All of these calculations correspond directly to inflow/outflow. What is your pond size in acre/feet and surface acres? What is your watershed size?
Usually there is at least 24" more dam height above the top of your emergency spillway. I presume the concrete spillway is your emergency. I would expect 24" more dam height above this structure on the balance of the dam.
