Septic soil in Spotsylvania County, VA, by the numbers
Very limited
In Spotsylvania County, VA, 50.9% of the surveyed land carries a "Very limited" rating for a standard septic drain 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. Spotsylvania County, VA is 401.942 square miles with a population of 152,021.
What Spotsylvania County's reading doesn't cover
USDA's survey covers the whole of Spotsylvania County, VA 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 Spotsylvania County will actually do.
What a system would cost here
With 50.9% of Spotsylvania 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.
Spotsylvania County's rank among Virginia counties
Nationally, Spotsylvania County, VA is the 2,861-most-constrained of 3,058 rated counties for septic soil. Within Virginia alone it ranks 94 of 110.
Further reading
How this rating is built, and its real limits · Conventional vs. engineered septic systems