Bidding on small welding shop 400 amp 1 ph It is a metal butler building , already built on slab , sidewalk poured all the way around . Question is , I can tie ground to steel easily but with slab already poured , and sidewalk , I can't tie to rebar or use ground rods without cutting concrete . any advice would be appreciated .
I have seen them drill a hole in the concrete for a rod, just bear in mind it has to be 8' in the dirt so the rod needs to be longer than 8'. If you can find a place that is out of the traffic path that may be an option.
With the sidewalk already poured does that mean that all the plumbing lines to the street are already roughed in? That would be a readymade route to use if the plumbing is not in. Otherwise, I would use a short length of rigid steel to cross the walk with a kick down on the outside end.
I've done this by drilling, as gfretwell suggested. I drilled through the slab with a 7/8 bit (avoiding the 2' footer around the parameter of the building if at all possible) and then drove a 10' copper clad ground rod. If I recall, I even did this with a stainless rod ages ago for one application. Some heavy duty urethane caulk in and around the hole and rod and squeezed into the hole (after you blow it out) is a good touch to avoid water intrusion.
NOTE: Be VERY carefull not to drive the rod anywhere near a possible water or waste run. Carefull note where plumbing fixtures are in relation to your desired rod location BEFORE you even think about drilling and driving. Nobody wants to chip and dig to do a reapir on a sewer line =)