Septic suitability in Clinton County, IA
Very limited
Clinton County, IA: USDA's soil survey calls 95.7% of the county "Very limited" for a septic leach field. That reading means a conventional system is a poor bet here - 95.7% of Clinton County lands in the strictest "very limited" bucket USDA uses. The county spans 694.959 square miles, home to 46,015 people.
What this number does and doesn't tell you
This is a countywide, area-weighted figure across every soil survey map unit in Clinton County, IA - never a reading for one specific parcel. Budget $750-$1,850 for a real perc test on any specific parcel - that's the only figure a permit application accepts.
Clinton County: conventional vs. engineered cost
95.7% of Clinton 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, Clinton County, IA ranks 565 most-constrained nationally, and 43 of 99 within Iowa.
Further reading
How this rating is built, and its real limits · Conventional vs. engineered septic systems