bc, My conservation agent also specified a small 6" pipe for my 2 acre pond. I went with a ten inch pipe. My conservation agent explained that they typically recommend the smaller pipes so water runoff is buffered/ accumulated by your pond, and then slowly is released downstream to rivers. My two acre pond will hold 1 million gallons of water between the one foot elevation difference of the primary pipe spillway and the emergency overflow spillway. I think it is better to go with the bigger pipe to prevent erosion damage in the emergency overflow spillway.

Jeff Gaines