I recently inspected a main service panel in a house that was reportedly built in 2009, for which service grounding could not be confirmed, and in any case was strangely configured, with 4 solid wires that were evidently 8 gauge copper consistent in appearance with grounding wires observed running from the main panel, and one such wire as a jumper across the water meter, which was in a closet above the crawl space, which was inaccessible, its opening obstructed by the finished basement wall and ceiling (nice!).
No exterior grounding rod connection was observed, either from the main panel or the meter, and most of the foundation was the inaccessible crawl space, with about 1/4 of the foundation being an almost completely finished basement, so the wire runs were not visible, except perhaps as noted near the water meter.
The 4 solid 8 gauge wires were consistent with 2 connections of 2x8 gauge wiring. Would such doubled grounding wires be proper if an Ufer ground was used that was obstructed from view? It seems such wires would have sufficient current-carrying capacity, but it’s certainly unusual.
I advised my client to investigate permits.