Grounding Electrode Burial Depth Requirements

Where rock bottom is encountered when driving a ground rod at an angle up to 45 degrees, the electrode can be buried in a trench that is at least ______ deep.

a) 18 in.
b) 30 in.
c) 4 ft
d) 8 ft

See answer and applicable Code reference

The correct answer is: b) 30 in.

Article 250 covers the requirements for bonding and grounding. Part III of this Article focuses on the grounding electrode system and grounding electrode conductor requirements. As noted in 250.53(G), "The electrode shall be installed such that at least 8 ft of length is in contact with the soil. It shall be driven to a depth of not less than 8 ft except that, where rock bottom is encountered, the electrode shall be driven at an oblique angle not to exceed 45 degrees from the vertical or, where rock bottom is encountered at an angle up to 45 degrees, the electrode shall be permitted to be buried in a trench that is at least 30 in. deep." 

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