dirty ground in facade

I have a project where LED's are installed in a building facade in SF.
My 12,000 LED's are supplied with 2.5 V + and the building, or parts thereof are my ground.
Since this installation extends to a height of 170 feet, I was wondering what sort of ground for my negative pole I could expect.
My power supply vendor brought up the possibility, that I would have my negative pole of the supply riding on incredibly dirty ground, polluted with induced AC and spikes of unknown shape.

IF so, what would be a good approach to make this work anyways?

Probably would be best to run a separate wire for the ground rather than trying to use the building frame.

That is what I thought as well.
But the difference seems by degrees only.
I can look at the entire metal facade/structure, what sort of a ground is that?

Or I look at my 6 000 feet of SS tubing and insulate it from the building, possibly even run a separate grounding wire, which could also act as an antenna, and ground my installation with that?

Or float the whole thing?