What Effingham County, IL's soil rates for a septic system
Very limited
95.4% of Effingham County, IL's surveyed soil comes back "Very limited" in USDA's own SSURGO data, the county's dominant condition for a septic absorption field. Expect the ground itself to work against a plain gravity system; USDA's strictest bucket alone covers 95.4% of the county. Effingham County, IL is 478.767 square miles with a population of 34,602.
What Effingham County's reading doesn't cover
Effingham County's rating is an average across the whole county, not a promise about any one lot inside it. A local percolation test, typically $750-$1,850 (around $1,300 typical), is the only way to know what one lot in Effingham County will actually do.
What a system would cost here
With 95.4% of Effingham County rating "Very limited", a standard gravity system is not a safe assumption here. The engineered-system range, $10,000-$40,000 (mound or aerobic treatment), is the more realistic number to plan around, against $3,000-$8,000 for a conventional system on the rare lot that passes.
Effingham County's rank among Illinois counties
Nationally, Effingham County, IL is the 613-most-constrained of 3,058 rated counties for septic soil. Within Illinois alone it ranks 31 of 101.
Related guides
How this rating is built, and its real limits · Conventional vs. engineered septic systems