Section 250.52(A) 1-8 describes all of the permitted grounding electrodes. There is one thing that all grounding electrodes have in common; they are all installed underground.

Section 250.52(A)(2) is all about “metal in-ground support structure(s)”. In order for a metal in-ground support structure to qualify as a grounding electrode, it must be in direct contact with the earth vertically for 10 feet or more, with or without concrete encasement.

The informational note makes it clear that metal in-ground support structures include, but are not limited to, pilings, casings, and other “structural metal”.

Below is a preview of Article 250. See the actual NEC^® text at NFPA.ORG for the complete code section. Once there, click on their link to free access to the 2020 NEC^® edition of NFPA 70.

2020 Code Language:

250.52(A) Electrodes Permitted for Grounding.

(2) Metal In-ground Support Structure(s).

One or more metal in-ground support structure(s) in direct contact with the earth vertically for 3.0 m (10 ft) or more, with or without concrete encasement. If multiple metal in-ground support structures are present at a building or a structure, it shall be permissible to bond only one into the grounding electrode system.

Informational Note: Metal in-ground support structures include, but are not limited to, pilings, casings, and other structural metal.