Fayette County, IL: the USDA septic-suitability picture

Very limited

Fayette County, IL: USDA's soil survey calls 91.2% of the county "Very limited" for a septic leach field. Expect the ground itself to work against a plain gravity system; USDA's strictest bucket alone covers 91.2% of the county. The county spans 716.451 square miles, home to 21,157 people.

What this number does and doesn't tell you

Fayette County's rating is an average across the whole county, not a promise about any one lot inside it. Budget $750-$1,850 for a real perc test on any specific parcel - that's the only figure a permit application accepts.

Fayette County: conventional vs. engineered cost

91.2% of Fayette 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.

Fayette County's rank among Illinois counties

Among the 3,058 rated counties on this site, Fayette County, IL ranks 1,150 most-constrained nationally, and 43 of 101 within Illinois.

Before you act on this

How this rating is built, and its real limits · Conventional vs. engineered septic systems