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How can I specify a deep grounding well for a substation? For example, let’s say I have a high resistivity soil that increases with depth (top layer 6m of 900 ohm-m, lower layer 2500 ohm-m). My grid resistance is 6 ohm and I want to achieve 1 ohm. I know some utilities have a predetermined well arrangement, lets say 1.5m dia and 20 m deep filled with bentonite. They install it and then measure the resistivity after. Seems more experimental rather than theoretical. Is it also possible to model deep grounding wells?

Hi Eduardo,

Thank you for your question regarding deep ground wells, it is our pleasure to help.

Yes, it is quite possible to calculate the predicted resistance-to-ground of an electrode prior to installing it.  The following link will show you the simplified formula:


However, the best way to do this calculation is with computer modeling software.  We use the CDEGS engineering software program, the most validated software in the industry.   Not only can a grounding system that meets the 1-ohm resistance-to-ground specification be accurately calculated (it may take a combination of deep wells along with the grounding grid), but the federally mandated Human Safety requirements (29 CFR 1910.269) can also be calculated.

Feel free to call us at 310-318-7151 California time and someone will be glad to speak with you about your project, free of charge.

Best regards,

The Engineering Team at E&S Grounding Solutions


Photo credit: E&S Grounding Solutions

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