I am trying to design a ground grid, but I need to add a ground well ( a ground rod that is driven deep enough till it is in water, e.g. 300ft..). The problem is, when I do this it seems that the soil resistivity of the 2nd layer will be assumed to be 1 ohm-meter. I am following a previously designed grid and I do not know where the engineer got this assumption. I do not think this assumption is right because the calculated (modeled) results were very different from the tested results after the grid with the well was put in. The engineer is not around and I cannot seem to find much information on ground wells. Can someone shed some light on this for me. I was also wondering what was the best method for doing the calculations for a ground grid that provides an accurate model, when designing for a substation. I appreciate any suggestions. Thank you.