Dunklin County, MO: the USDA septic-suitability picture
Very limited
Dunklin County, MO's SSURGO dominant class comes back "Very limited", covering 91.4% of the county. Practically, that rules out a simple gravity system for most of the county - 91.4% of it sits in USDA's most-constrained bucket. The county spans 541.909 square miles, home to 27,002 people.
What this number does and doesn't tell you
USDA's survey covers the whole of Dunklin County, MO 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.
Dunklin County: conventional vs. engineered cost
91.4% of Dunklin 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, Dunklin County, MO ranks 1,122 most-constrained nationally, and 74 of 114 within Missouri.
Related guides
How this rating is built, and its real limits · Conventional vs. engineered septic systems