is there a print for the house? On the blueprint, it should show how far the foundation goes out. As for drains, they can always appear anywhere. If this is a new job, as the GC in charge of the job. If it is an old home, look for any pipes leaving the house near where you want to install ground rods, look for cable TV wires, Telco wires, gas lines, etc. and cross your fingers.
#14946 - 10/05/0204:36 AMRe: Ground Rod Installation
Common practice for me is to be at least 30" from the drip edge of the building, to ensure a wet area for better continuity to ground.
Plus there's something like a 30" radius around the rod that is it's "effective area", so to speak, and I'm under the impression that the code change in 2002 for the 18" burial depth of a horizontal rod to 30" falls under the same line of thinking.
I really need to get Soare's Book on Grounding...
-Virgil Residential/Commercial Inspector 5 Star Inspections Member IAEI
#14947 - 10/05/0207:54 AMRe: Ground Rod Installation