Union County, AR's soil, for a septic absorption field
Very limited
Soil across 95.8% of Union County, AR rates "Very limited" in USDA's septic-absorption-field interpretation. Expect the ground itself to work against a plain gravity system; USDA's strictest bucket alone covers 95.8% of the county. Union County, AR is 1,039.067 square miles with a population of 37,008.
What Union County's reading doesn't cover
Two lots a mile apart in Union County can carry different soil, even though they share one countywide rating. A local percolation test, typically $750-$1,850 (around $1,300 typical), is the only way to know what one lot in Union County will actually do.
What a system would cost here
With 95.8% of Union 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.
Where this sits nationally
Nationally, Union County, AR is the 553-most-constrained of 3,058 rated counties for septic soil. Within Arkansas alone it ranks 11 of 75.
Related guides
How this rating is built, and its real limits · Conventional vs. engineered septic systems