Hello,
We were having a discussion at my work today about how deep grounding rods must go for a substation in relation to the presence of ground water. Several of my colleagues were suggesting that the rods must be deep enough to penetrate that water table, and not much further than that. However, I and another coworker were of the mind that a water table will present itself in a soil survey, and thus we should be "ignorant" of the depth of the water table and design a grid that creates suitable potentials according to the provided soil model (and therefore, we may still need 24 foot rods even if the water table is 6 feet below grade).
The question seemed to boil down to trusting the models versus trusting that the groundwater would dissipate a fault. I was just curious of the opinions of others in this regard, would you stop the rods at the water table, or drill them as far as your "ignorant" model proposes?