I live in a town on top of a hill in south central Pennsylvania. Actually just outside a town famous for a flood. My back yard has so much water in it that I can't let my dogs run. Problem is, it is all clay and not accessible by machine. My question is. Do I have to go twelve inches deep and twelve inches wide when digging my trench, or can I dig enough to cover the pipe? My main problem is rainwater run-off.