Jefferson County, ID Septic Rating
Jefferson County's SSURGO septic rating
Very limited
Jefferson County, ID: USDA's soil survey calls 81.1% of the county "Very limited" for a septic leach field. Expect the ground itself to work against a plain gravity system; that share is already USDA's strictest bucket, not a lesser constraint layered on top. The county spans 1,094 square miles, home to 34,854 people.
What this number does and doesn't tell you
Nothing about Jefferson County, ID'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
81.1% 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, ID ranks 1,986 most-constrained nationally, and 32 of 44 within Idaho.
Related guides
How this rating is built, and its real limits · Conventional vs. engineered septic systems