Hi John,
If you remember how BigBlu 155 is mounted at ESSA, it sits on a one inch thick stall mat. When the building was built either the architect or contractor messed up and put the isolation pad in the wrong place for it, at the other end of the building away from the forges. The floor where it sits now is the standard 4 inches thick and Blu is bolted down with anchor's. After using a while the floor started to crack around the hammer and a square around Blu was cut with a concrete saw to isolate it and make it free floating. It's been working fine since then no more cracking.
Randy