18.) The improper installation of ground rods.
There are a number of deficiencies found with the installation of ground rods. Section 250-52 ( c) (3) requires that the rod be installed so that at least 8' of length is in contact with the soil and the upper end of the electrode must be flush with or below ground level unless the aboveground end and grounding electrode conductor attachment is protected against physical damage. The most common deficiency found is that the 8' rod has been installed so that the upper end of the rod has been left above grade. In this case the rod is not in contact with the soil for the full eight feet. This problem also occurs when rod electrodes are installed inside through concrete slabs. Usually the rod has been left so the upper end and grounding electrode connection are just above the slab. Again, the rod is not in contact with the soil for the full eight feet and it is very likely that the grounding electrode connection is subject to physical damage.
Another common deficiency found with rod electrodes is the non-installation of the second ground rod. Section 250-56 requires that a single rod, pipe or plate electrode that does not have a resistance to ground of 25 ohms or less must be augmented by a second electrode of any type. This problem is more common in out lying areas of the State where inspection is limited. It is possible that the only inspection in these areas is made by the utility company. Depending on which utility company you are dealing with they may only look for one rod.
The 1999 NEC makes it clear in Section 250-50 (a) (2) that the 25 ohms to ground resistance, described in 250-56, also applies to a supplemental electrode if a rod, pipe or plate electrode is used. A supplemental electrode is required when a metal underground water pipe is used as the main grounding electrode. The supplemental electrode was first introduced in the 1981 NEC as a result of some municipalities replacing metal water systems with plastic. Typically, in the past, only one rod electrode was installed as a supplemental to the underground water pipe.