Ground wire between SC & Sub

[mphillipps]

I'm running #4 awg 250' from a service entrance to a new sub panel. Both panels will be properly grounded and bonded. Will I need to run a ground wire the entire 250' from panel to panel or will the ground electrodes at both ends be sufficient?
I've spent some trying to looking in the NEC but did not come up with anything specific.
A NEC reference be great.

 

[LarryFine]

Will I need to run a ground wire the entire 250' from panel to panel or will the ground electrodes at both ends be sufficient?

No, you absolutely must use an EGC.

A NEC reference be great.

250.4(A)(5)

 

[infinity]

If these are two separate structures then 250.32 would be your reference.