Crawford County's SSURGO septic rating
Very limited
USDA puts Crawford County, IL at "Very limited" for septic absorption fields, the dominant reading across 97.6% of the county's soil. 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 443.643 square miles, home to 18,388 people.
What this number does and doesn't tell you
USDA's survey covers the whole of Crawford County, IL at once, not any single address. Budget $750-$1,850 for a real perc test on any specific parcel - that's the only figure a permit application accepts.
Crawford County: conventional vs. engineered cost
97.6% of Crawford 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.
Crawford County's rank among Illinois counties
Among the 3,058 rated counties on this site, Crawford County, IL ranks 306 most-constrained nationally, and 15 of 101 within Illinois.
Related guides
How this rating is built, and its real limits · Conventional vs. engineered septic systems