Jefferson County, WV: the USDA septic-suitability picture
Very limited
Jefferson County, WV: USDA's soil survey calls 75% of the county "Very limited" for a septic leach 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. The county spans 209.289 square miles, home to 61,264 people.
What this number does and doesn't tell you
Nothing about Jefferson County, WV's SSURGO figure applies to a specific address - it's a county-wide average. Budget $750-$1,850 for a real perc test on any specific parcel - that's the only figure a permit application accepts.
Jefferson County: conventional vs. engineered cost
75% of Jefferson 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.
Where this sits nationally
Among the 3,058 rated counties on this site, Jefferson County, WV ranks 2,277 most-constrained nationally, and 51 of 55 within West Virginia.
Related guides
How this rating is built, and its real limits · Conventional vs. engineered septic systems