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I'm no expert, however, the rebar in concrete has to be properly bonded as does any metal around the tub within 6' (I think, like I said, I'm no expert). I would contact the electrician and ask him when he needs to be involved. I used an EZ-Pad so my electrician said he could come the day the tub was installed.
this will depend on your area, check local codes...in MN for example bonding is not necessary
As for the code requirements, I agree with the other posters that you need to check with a licensed electrician or local code enforcement to make sure your installation is safe and legal. As for the actual mechanics of it, you have several options. Some people like to have the electrical line totally hidden and will run the line in conduit under the slab and bring it up from below the tub. I wasn't a fan of that idea. So, we ran the conduit along the edge of the slab over to where one of the tub's electrical openings in the skirt would be. We knew right where to run it because we knew what tub we were going to buy before we started site work. We ran the conduit while the concrete guy's backhoe was here to dig the trench. Saved us some $. Electrician came while tub was being delivered and finished the wiring then. All you see is a foot or so of flexible conduit from ground to tub. Looks good.