Stumped on discoloration

Today’s inspection circa 2001. 200 amp Siemens 42 circuit panel with 35 of the available circuits being utilized. All 8 of the 2-pole 240v breakers were stacked left and the 19 single pole 120v breakers on the right side. Unable to determine connection to earthen ground connection as the grounding electrode was not exposed (covered over with poured concrete side walk servicing garage man door.
This is a back to back service (first point of disconnect) located in the garage with neutrals and grounds sharing the same bars. Upon removing the dead front cover observed that all of the bare ground wires were blackened, but the neutrals and load carrying branch circuit wiring had not been affected. Opened GFCI outlets within the garage and no discoloration was observed at these devices.
While realizing that load balancing is not really that big of a deal on a residential service it is not common to see all of the single pole and 2-pole breakers stacked?
Can not verify earthen ground? Home is located on brackish waterway, irrigation water provided by public utility. No other blackening of copper wire observed at various other devices within the home and no discoloration of other wiring within the panel kinda rules out a type of environmental contaminate? I am stumped

It is typical to see that where the cable has gotten wet.

Are you thinking that perhaps the home was not dried in before electric rough; that because the current carrying conductors would not have been stripped for landing at this point and therefore would not have be affected by exposure to moisture

Isnt it humid if FL. Not being a smart azz but just sayin. Some darkening of bare copper wiring is common IMO in areas that are suject to outdoor envirometal conditions. A open garage would be no different.

also looks like white wire used on a 240 volt circuit should be painted or taped, black

Underground service?

Yes underground service


Your correct, but until March 1st 2002 Building Officials had description as to when they adopted new code articles.As this prorpetty was permitted before FBC 2002 am unable to confirm

Try post #8 in this thread and see if it makes sense to you, makes sense to me.