Septic soil in Hampshire County, WV, by the numbers
Very limited
Soil across 97.2% of Hampshire County, WV 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 97.2% of the county. Hampshire County, WV is 640.402 square miles with a population of 23,793.
What Hampshire County's reading doesn't cover
Two lots a mile apart in Hampshire 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 Hampshire County will actually do.
What a system would cost here
With 97.2% of Hampshire 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.
Hampshire County's rank among West Virginia counties
Nationally, Hampshire County, WV is the 356-most-constrained of 3,058 rated counties for septic soil. Within West Virginia alone it ranks 17 of 55.
Further reading
How this rating is built, and its real limits · Conventional vs. engineered septic systems