1)When a ufer ground is installed is a supplemental electrode required? (2) If one is required do I need 2 rods and do they have to be 6' min away from each other and the foundation?(as this is used for an electrode)(3)Can the #4 grounding electrode conductor be run through bored holes in the 2x10's to the panel?
I remember reading Mr. Ufer's reports on his grounding electrode. Under extremely adverse conditions, his method always performed far better than the 25 ohms code calls for. This was confirmed by Max Macomb, in his documentation that finally persuaded the code panels to accept the "Ufer ground."
If you're measuring over 25 ohms, I would suspect a problem with the measurement method.
But, there is no rule agains adding an electrode if you want to....but it needs to be six feet, or more, from the Ufer...which, in this case, means the entire slab. With a "Ufer," your slab is the electrode- not just that little copper wire!
While many measure the resistance of the ground by simply sticking their meter probe in the dirt....there has to be a reason for those pricey clamp-on meters, and other fancy equipment, used to measure grounding impedence.