There are a number of ways to do it. Often, I'll see nice thick ground bars under the false floor, way oversized, with big lugs from all the racks. He's concerned about higher frequency ground currents, so the properties are very different than for 60Hz safety grounds. For instance, a metal raised deck that's insulated and not even touching the ground will have lower impedance to ground than a 20' ground rod, because the capacitance between the false floor and ground is essentially a short at higher frequencies, wheras the ground wire and rod function as a 0-loop inductor and have a high impedance.
Google MIL-HDBK-1012/1, it's a miliary handbook dealing with datacenters. It's free, and a good design reference
MIL-HDBK-419 also deals with grounding. You can ignore TEMPEST (security) and HEMP (nuclear) requirements.