As one who has worked as a licensed electrician in multiple states, I will mention the predictable nature of electricity to take ALL paths to earth, ohms law decides the amount but this phenomenon convinces me that earth bonding of blasting equipment should be done 100% independently of the electrical / water....
Also, worth mentioning, bonding equipment to earth or earth"ish" as I like to say, you create a greater potential between the earthed equipment and any unearthed personnel in the vicinity.
Equipotential bonding should be considered as well where stray neutrals could present themselves such as pool surround patios and the like. Stray voltages can stop dairy cows from lactating and blow up your rig.