Pond Boss Forums POND CONSTRUCTION Building a dam Critique My Overflow Stand Pipe Design

I think you have the right idea. I don't know if the 2" holes are necessary, and I'm unsure whether the 8" to 12" pipe will leave enough water thru before it starts going over the top (you are close on matching volume)s. But, it would be easy enough to bump up the 12" pipe after the fact. Just make sure that the emergency spillwas will handle the amount of water that is expected in a major hurricane/rain event and won't wash out.