Drilling for supports, I guess

If they do a lot of such drillings this could be related to the poor ground and they may have to put the building on piles.
Or maybe they just take soil samples.

Probably required by building codes. I doubt it's for soil samples, but maybe looking for diamonds!

Probably putting in piles to get support below the water table. It looks very technical whatever they're doing. Fascinating photo Diane.

Yes, something like that. A concrete parking garage is pretty heavy, so I imagine they need "anchors!" It doesn't look too unusual, to me, but I'm just a casual observer. Oh, also, every few decades there is an earthquake in the moderate category, here. Enough to have destroyed several 3-story brick buildings on Main St. in 1996. That included the courthouse and part of the cocunty gov't building.

Oh, do you have a water table there? It looks like desert to me. I like the earthquake theory.