Septic soil in Richland County, OH, by the numbers
Very limited
96.4% of Richland County, OH's surveyed soil comes back "Very limited" in USDA's own SSURGO data, the county's dominant condition for a septic absorption field. A standard gravity system routinely fails on ground like this; the same share of the county falls in USDA's worst absorption-field bucket outright. Richland County covers 495.227 square miles and counts 124,853 residents.
This is a county figure, not a parcel figure
USDA's survey covers the whole of Richland County, OH 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 Richland County.
System cost, conventional vs. engineered
Given Richland 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, Richland County, OH is the 463-most-constrained of 3,058 rated counties for septic soil. Within Ohio alone it ranks 48 of 87.
Related guides
How this rating is built, and its real limits · Conventional vs. engineered septic systems