What Ross County, OH's soil rates for a septic system
Very limited
Soil across 97.3% of Ross County, OH rates "Very limited" in USDA's septic-absorption-field interpretation. Practically, that rules out a simple gravity system for most of the county - 97.3% of it sits in USDA's most-constrained bucket. Ross County, OH is 689.166 square miles with a population of 76,046.
What Ross County's reading doesn't cover
USDA's survey covers the whole of Ross County, OH at once, not any single address. A local percolation test, typically $750-$1,850 (around $1,300 typical), is the only way to know what one lot in Ross County will actually do.
What a system would cost here
With 97.3% of Ross 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.
How Ross County, OH compares
Nationally, Ross County, OH is the 340-most-constrained of 3,058 rated counties for septic soil. Within Ohio alone it ranks 34 of 87.
Further reading
How this rating is built, and its real limits · Conventional vs. engineered septic systems