In eastern SC along the coast (low Country), there is never any frost in the ground. Fottings are often hand dug to undisturbed earth (a foot or 2).
Seems like we are in the same area!! Back when I was working construction, I was a part of 3 different custom homes from the ground up. Two of them were West of Highway 17 in Mt. Pleasant and the third was on Isle of Palms. All footing trenches were dug with a backhoe, but the house on IOP required much deeper footings. The entire lot was just like digging in the sand from the beach! Installing the onsite septic system didn't make things any easier either!