I am preparing to dig four 12" diameter, 36" deep holes for footers for a new deck. The problem I have in that somewhere in the area of where I will be digging is an underground PVC pipe that collects and removes rainwater from my roof. The discharge end of the pipe is about 100' away. Is there a way to detect the location of PVC pipe that is approximately 18" to 24" underground so that I can adjust my footer locations if necessary or do I just start digging and hope for the best?