Vacuum excavation to expose underground electrical utilities

Discussion created by brian.britain on Oct 20, 2016
Latest reply on Oct 21, 2016 by Steve Benton

We use vacuum excavation to expose underground utilities to precisely locate them.  When using this technique on buried electrical utilities, we are concerned about both arc flash and electrocution if we inadvertently damage the energized electrical utility.  We have a procedure that has us offsetting the test hole location such that we are not digging directly above the utility.  We use insulated air knives and other digging tools. We also have our employees in Arc Flash PPE category 2 FR clothing, EH-rated boots, and Class 0 lineman's gloves, as the vast majority of our work is on utilities under 600 volts.  My question is about PPE for work to expose electrical utilities greater than 600 volts.  Is it necessary to go to Arc Flash Category 4 PPE if the voltage is above 600 volts?  Table 130.7(C)(15)(A)(b) in NFPA 70E doesn't specifically mention exposing buried electrical utilities, and given that this work is performed outdoors in the heat, I'm concerned about introducing additional heat-related hazards.