Grounding on Bed rock

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https://en.wikipedia.org/wiki/Ufer_ground[/URL]]History
During World War II, the U.S. Army required a grounding system for bomb storage vaults near Tucson and Flagstaff, Arizona. Conventional grounding systems did not work well in this location since the desert terrain had no water table and very little rainfall. The extremely dry soil conditions would have required hundreds of feet of copper rods to be inserted into the ground in order to create a low enough impedance ground to protect the buildings from lightning strikes
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Ufer discovered that concrete had better conductivity than most types of soil. Ufer then developed a grounding scheme based on encasing the grounding conductors in concrete. This method proved to be very effective, and was implemented throughout the Arizona test site.
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Concrete is naturally basic (has high pH). Ufer observed this meant that it had a ready supply of ions and so provides a better electrical ground than almost any type of soil. Ufer also found that the soil around the concrete became "doped", and its subsequent rise in pH caused the overall impedance of the soil itself to be reduced.[3] The concrete enclosure also increases the surface area of the connection between the grounding conductor and the surrounding soil, which also helps to reduce the overall impedance of the connection

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