Earth-ground off-grid electric panel

[Robkh]

Planning off-grid 240V 25A EV charge system with EG4 6000XP inverter and EG4 PowerPro 14.3 kWh battery in my house garage. My house is built on riprap (boulders to raise it above a flood plain) which I cannot drive an 8 foot grounding rod into.
Nearby is a steel garage on concrete pad - I attached a 25 foot long bare copper wire 4AWG as a ufer ground to the steel for concrete underground before the concrete was poured
Question is how to earn-ground the planned EV charging electrical panel in my house garage.
Can I run a copper wire 4-6AWG to the steel garage ufer ground.
Code states that a grounding conductor cannot exceed 20 feet in length and should preferably be shorter. The run to the steel garage would exceed the 20 foot minimum.
Any suggestions would be welcome.

 

[G00SE]

@timselectric

 

[Bop]

I would think that asking the people that do the inspections would be the best bet...

Here in Australia, they can always make exceptions if it is physically impossible to meet the Au/Nz 3000 standards, but these have to be done on a 'case by case' basis, and have to be 'functionally identical'

I had to do a gridtie system on a holiday house that was literally on top of a 'huge' rock- literally the entire hill it was on was a single giant rock- obviously in that case a standard earthrod was totally out of the question- we had to provide an earth rod down the hill to actual 'ground', but because of the distance it was running- it had to be specced in 120mm^2 cable (thicker than a cars starter motor cable by quite a bit) and be run in metal conduit the whole way, and measured afterwards to ensure the final earth up the top was 'with specs' for resistance

I am sure they have something similar- most bureaucracies aren't 'that' hidebound...

 

[Robkh]

Thank you all. I bought two copper ground rods and drove both 8 feet down 10 minutes each about 7 feet apart - review of my house plan showed the riprap boulders were further south from the site of the ground rods. I connected the two rods with a 6 AWG copper wire. Problem solved.