Carroll County, TN: the USDA septic-suitability picture
Very limited
USDA puts Carroll County, TN at "Very limited" for septic absorption fields, the dominant reading across 96.5% of the county's soil. This is the reading that pushes a project toward an engineered system rather than a conventional one, and it covers 96.5% of Carroll County's land. The county spans 597.658 square miles, home to 29,107 people.
What this number does and doesn't tell you
Nothing about Carroll 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.
Carroll County: conventional vs. engineered cost
96.5% of Carroll 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, Carroll County, TN ranks 454 most-constrained nationally, and 4 of 95 within Tennessee.
Related guides
How this rating is built, and its real limits · Conventional vs. engineered septic systems