It's a little tough to make out, but can you see the ring of dead grass around the four concrete blocks? The blocks supported the primary coil of our biggest Tesla Coil system. We started noticing discoloration in the grass about 4 days after a single night of high-power runs. During those runs, the coil was pulling roughly 75 amps @ 240 volts...about 18kVA of input power. There were *constant* powerarcs to the ground, with very few streamers. Notice that the grass is still green immediately around and between the concrete blocks. There were no hits to this area as the primary coil took the hits instead ; )