How should I handle the grounding electrode system for a 400 amp service?

I plan on installing a 1/0 copper from the main disconnect to the within 5' of where the water service enters the building and jump the water meter unspliced. I am also installing a #6 from the main disconnect to 2 ground rods spaced at least 6' apart.

However, this building has a separate incoming water service for the sprinkler system. Can I install a bonding jumper sized according to 250.66 (1/0) from the sprinkler service to the water service and connect it to the GEC using a split bolt? Or should this conductor also be run back to the main disconnect? I'm a little confused by 250.70 which I beleive is referring to my situation.

Thanks