Clay is the recurring problem
South Carolina classifies soils with massive or platy structure and expansible clays as unsuitable for conventional systems, and SCDES states plainly that clay soils require more space. On the Piedmont side of the Fall Line that is a live constraint on a lot of Aiken parcels.
Rural parcels, rural constraints
Larger lots sound like they solve the problem, but slope, well setbacks at 75 feet for private and 100 for public, and the required fifty percent repair area still narrow where a field can actually go.
Engineered work needs Tier 3
If your Aiken lot gets denied for a conventional design, the answer is a Standard 610 engineered system, prepared by a professional engineer with a licensed soil classifier. In South Carolina only a Tier 3 installer can legally install it. Most contractors here are not Tier 3.