White County, TN: the USDA septic-suitability picture
Very limited
White County, TN: USDA's soil survey calls 67.2% of the county "Very limited" for a septic leach field. This is the reading that pushes a project toward an engineered system rather than a conventional one, and it covers 67.2% of White County's land. The county spans 376.678 square miles, home to 29,108 people.
What this number does and doesn't tell you
Nothing about White County, TN's SSURGO figure applies to a specific address - it's a county-wide average. Budget $750-$1,850 for a real perc test on any specific parcel - that's the only figure a permit application accepts.
White County: conventional vs. engineered cost
67.2% of White 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, White County, TN ranks 2,556 most-constrained nationally, and 83 of 95 within Tennessee.
Further reading
How this rating is built, and its real limits · Conventional vs. engineered septic systems