I just posted this question on Mike Holt's site but thought I would also post it here also.
We just installed a new 200 amp service for a single family dwelling. We connected the grounding electrode conductor to the underground water service (aprox. 30' of 1 1/4" copper) and to a concrete encased electrode. The concrete encased electrode consisted of two 20' sections of rebar tied to the bottom rebar in the footing. The total length of the concrete encased electrode exceeds 50' and was signed off by the inspector before the foundation was poured. Today we had the inspection on our service and the inspector said that unless we can prove that the concrete encased electrode has a resistance of 25 ohms or less we must install a ground rod to supplement it. 250.56 requires the rod, pipe and plate electrodes must have a resistance of 25 ohms or less but does not say anything about concrete encased electrodes. I have been in business in Northern California for almost 20 years and have never had an inspector question the resistance concrete encased electrode but am curious as to what inspectors require in other areas so any feed back would be appreciated. The inspector also we could make the test with a ohm meter which is definitely not the proper piece of equipment to use to test grounding electrodes.