Yell County, AR: the USDA septic-suitability picture
Very limited
USDA puts Yell County, AR at "Very limited" for septic absorption fields, the dominant reading across 87.9% of the county's soil. Practically, that rules out a simple gravity system for most of the county - 87.9% of it sits in USDA's most-constrained bucket. The county spans 930.386 square miles, home to 20,134 people.
What this number does and doesn't tell you
Two lots a mile apart in Yell County can carry different soil, even though they share one countywide rating. Budget $750-$1,850 for a real perc test on any specific parcel - that's the only figure a permit application accepts.
Yell County: conventional vs. engineered cost
87.9% of Yell 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.
How Yell County, AR compares
Among the 3,058 rated counties on this site, Yell County, AR ranks 1,475 most-constrained nationally, and 51 of 75 within Arkansas.
Further reading
How this rating is built, and its real limits · Conventional vs. engineered septic systems