2002 NEC 250.56
A little more explanation:
Unless you have the equipment and time to prove that your one grounding electrode has a resistance of 25 Ohms or less (and the Power Company doesn't mind only one) then the NEC requires no less than two.
Ground Meggers are expensive...
Also, 250.52(A)(5) requires 8 ft to be in contact with the earth. 10 ft. could be your local PoCo requirement.
[This message has been edited by sparky66wv (edited 03-14-2002).]
