It is most often thought that the lightning threat comes from above.  Once you have good aerial protection systems incorporating surge arrestors and grounding systems all will be fine.  This was the conventional wisdom until it was discovered that lightening can strike several miles away, and be conducted through the soil and enter into your grounding systems and power input lines.  The power input lines may have surge protection, but the grounding system is left vulnerable. Damage to equipment, erratic and diminished performance and personnel safety is at severe risk through sub surface lightning conduction.