Septic suitability in Whiteside County, IL
Very limited
Whiteside County, IL: USDA's soil survey calls 71% of the county "Very limited" for a septic leach field. That reading means a conventional system is a poor bet here - 71% of Whiteside County lands in the strictest "very limited" bucket USDA uses. The county spans 684.099 square miles, home to 54,657 people.
What this number does and doesn't tell you
Whiteside 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.
Whiteside County: conventional vs. engineered cost
71% of Whiteside 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, Whiteside County, IL ranks 2,432 most-constrained nationally, and 80 of 101 within Illinois.
Related guides
How this rating is built, and its real limits · Conventional vs. engineered septic systems