Strange Grounding Question

[Fearno42]

Iam currently working on a New 3t mri project at a local hospital.The question is I have three 480/277 to 208/120 xfmers.Sized 45kva,30kva,15kva.
They are ceiling hung all side by side one is normal power,one is emergency power,and the last is ups protected power.Th local ahj said he wanted them all tied on to the ground bar that serves as the common grounding point.Where all the grounds come together.Do I have to run a seperate wire for the xo from each xfmer back to the ground bar?Or can I tap the Xo sized to the largest 45 kva xfmer.

 

[Fearno42]

I should also mention there is no building steel to speak of only the ground bar where the ufer grounds and ground rods tie in.

 

[RUWired]

Article 250.30(A)4 allows a single gec with taps from each transformer.The size of the gec and the taps are from 250.30(A)4(A)and(B).