New home service has 2 grounds. a 20' rebar in the footing, and 2 ground rods (5' each?)
Water lines, water heaters, etc. should also be connected with bonding wire. Use something like this:
https://www.homedepot.com/p/Blackburn-Bronze-Ground-Clamp-1-2-1-in-for-Direct-Burial-JD-B1-15/202907610
Can you re-run the 18' over head or in a wall instead? Concrete and steel don't get along, especially in southern florida.