Richland County's SSURGO septic rating
Very limited
Richland County, SC's SSURGO dominant class comes back "Very limited", covering 68.9% of the county. That reading means a conventional system is a poor bet here - 68.9% of Richland County lands in the strictest "very limited" bucket USDA uses. The county spans 757.309 square miles, home to 430,651 people.
What this number does and doesn't tell you
Two lots a mile apart in Richland County can carry different soil, even though they share one countywide rating. Budget $750-$1,850 for a real perc test on any specific parcel - that's the only figure a permit application accepts.
Richland County: conventional vs. engineered cost
68.9% of Richland County carrying a "Very limited" reading changes the realistic budget here. Conventional systems run $3,000-$8,000 where they pass; where they don't, engineered alternatives (mound or aerobic treatment, whichever the health department requires) run $10,000-$40,000 - budget toward the higher figure until a perc test says otherwise.
Where this sits nationally
Among the 3,058 rated counties on this site, Richland County, SC ranks 2,499 most-constrained nationally, and 25 of 46 within South Carolina.
Further reading
How this rating is built, and its real limits · Conventional vs. engineered septic systems