ECN Forum Forums Code Related Discussion NEC & other Code issues bonding two 200 amp main breaker panels

IMHO, what Greg said and provided the sketch for should solve the issue.

200' to the water piping, to the wireway, and irreversible crimps to go to each MOCP.

There are numerous solutions in comm/ind sites to install compliant grounding systems, building steel, rebar, etc.

I trust that you checked the water piping from the utility, and it is metallic??

Also bear in mind, the service can be grounded anywhere between the service point to the service disconnect so there may be other opportunities to ground it if you can't get into the meter can.