Instrument Earth pit


I am working on a fuel farm automation project of Airport. We have supplied DCS system. I came to know after visiting site that there is no separate earth pits are available for instrument system. All the earthing system including lightning are connected to a single grid. I am using IS, Non IS and FF devices and have separate busbars for each in the DCS panel. Since a common grid is there, I am getting continuity between all. Now the construction work at site is already completed. Is there any way I can make sure safety of my system and instruments and provide isolation??

Thanks in advance GJ

Generally you need to have system earth and electrical earth separate. Raise it as concern and make minutes of meeting and circulate to project team. But make sure at the end they dont ask you to build one for free!