Where in the code book does it require 2 ground rods ?

250.56

Two rods are not required, but they are typically done to avoid having to test for resistance, or if the required resistance is not met.

A State Electrical Inspector may require more than one rod as a rule in that state.

Depends what city/state you're in. Here usually they just put one ground rod and run the ground wire to the cold water pipe and the ground rod.

Los Angeles Electrician (http://www.branovercontractors.com)

Depends what city/state you're in. Here usually they just put one ground rod and run the ground wire to the cold water pipe and the ground rod.

This may be true for your area, but he asked where it was in the code book.