What Washington County, FL's soil rates for a septic system
Very limited
Soil across 85.7% of Washington County, FL rates "Very limited" in USDA's septic-absorption-field interpretation. 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. Washington County covers 584.677 square miles and counts 26,503 residents.
This is a county figure, not a parcel figure
Two lots a mile apart in Washington County can carry different soil, even though they share one countywide rating. A site-specific perc test, usually $750-$1,850, is what a health department will actually require before permitting a lot in Washington County.
System cost, conventional vs. engineered
Given Washington 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, Washington County, FL is the 1,645-most-constrained of 3,058 rated counties for septic soil. Within Florida alone it ranks 35 of 65.
Related guides
How this rating is built, and its real limits · Conventional vs. engineered septic systems