Coles County's SSURGO septic rating
Very limited
USDA puts Coles County, IL at "Very limited" for septic absorption fields, the dominant reading across 97% of the county's soil. That reading means a conventional system is a poor bet here - 97% of Coles County lands in the strictest "very limited" bucket USDA uses. The county spans 508.272 square miles, home to 46,423 people.
What this number does and doesn't tell you
Two lots a mile apart in Coles County can carry different soil, even though they share one countywide rating. Budget $750-$1,850 for a real perc test on any specific parcel - that's the only figure a permit application accepts.
Coles County: conventional vs. engineered cost
97% of Coles 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.
Coles County's rank among Illinois counties
Among the 3,058 rated counties on this site, Coles County, IL ranks 379 most-constrained nationally, and 18 of 101 within Illinois.
Related guides
How this rating is built, and its real limits · Conventional vs. engineered septic systems