Allendale County, SC's soil, for a septic absorption field

Very limited

Soil across 80.4% of Allendale County, SC rates "Very limited" in USDA's septic-absorption-field interpretation. Practically, that rules out a simple gravity system for most of the county - 80.4% of it sits in USDA's most-constrained bucket. Allendale County covers 408.095 square miles and counts 7,551 residents.

This is a county figure, not a parcel figure

Nothing about Allendale County, SC's SSURGO figure applies to a specific address - it's a county-wide average. A site-specific perc test, usually $750-$1,850, is what a health department will actually require before permitting a lot in Allendale County.

System cost, conventional vs. engineered

Given Allendale County's rating, plan for the engineered-system range rather than the conventional one. The engineered-system range, $10,000-$40,000 (mound or aerobic treatment), is the more realistic number to plan around, against $3,000-$8,000 for a conventional system on the rare lot that passes.

How Allendale County, SC compares

Nationally, Allendale County, SC is the 2,025-most-constrained of 3,058 rated counties for septic soil. Within South Carolina alone it ranks 19 of 46.

Before you act on this

How this rating is built, and its real limits · Conventional vs. engineered septic systems