Septic soil in Giles County, TN, by the numbers
Very limited
81.6% of Giles County, TN's surveyed soil comes back "Very limited" in USDA's own SSURGO data, the county's dominant condition for a septic absorption field. That reading means a conventional system is a poor bet here - 81.6% of Giles County lands in the strictest "very limited" bucket USDA uses. Giles County covers 610.931 square miles and counts 30,971 residents.
This is a county figure, not a parcel figure
USDA's survey covers the whole of Giles County, TN at once, not any single address. A site-specific perc test, usually $750-$1,850, is what a health department will actually require before permitting a lot in Giles County.
System cost, conventional vs. engineered
Given Giles 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.
Where this sits nationally
Nationally, Giles County, TN is the 1,959-most-constrained of 3,058 rated counties for septic soil. Within Tennessee alone it ranks 51 of 95.
Related guides
How this rating is built, and its real limits · Conventional vs. engineered septic systems