Madison County, NC's soil, for a septic absorption field
Very limited
In Madison County, NC, 96.1% of the surveyed land carries a "Very limited" rating for a standard septic drain field. Expect the ground itself to work against a plain gravity system; USDA's strictest bucket alone covers 96.1% of the county. Madison County, NC is 449.615 square miles with a population of 22,352.
What Madison County's reading doesn't cover
This is a countywide, area-weighted figure across every soil survey map unit in Madison County, NC - never a reading for one specific parcel. A local percolation test, typically $750-$1,850 (around $1,300 typical), is the only way to know what one lot in Madison County will actually do.
What a system would cost here
With 96.1% of Madison County rating "Very limited", a standard gravity system is not a safe assumption here. 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.
Where this sits nationally
Nationally, Madison County, NC is the 515-most-constrained of 3,058 rated counties for septic soil. Within North Carolina alone it ranks 3 of 97.
Related guides
How this rating is built, and its real limits · Conventional vs. engineered septic systems