Septic soil in Cooper County, MO, by the numbers
Very limited
94.2% of Cooper County, MO's surveyed soil comes back "Very limited" in USDA's own SSURGO data, the county's dominant condition for a septic absorption field. That reading means a conventional system is a poor bet here - 94.2% of Cooper County lands in the strictest "very limited" bucket USDA uses. Cooper County, MO is 564.746 square miles with a population of 17,122.
What Cooper County's reading doesn't cover
This is a countywide, area-weighted figure across every soil survey map unit in Cooper County, MO - never a reading for one specific parcel. A local percolation test, typically $750-$1,850 (around $1,300 typical), is the only way to know what one lot in Cooper County will actually do.
What a system would cost here
With 94.2% of Cooper 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.
Where this sits nationally
Nationally, Cooper County, MO is the 760-most-constrained of 3,058 rated counties for septic soil. Within Missouri alone it ranks 54 of 114.
Further reading
How this rating is built, and its real limits · Conventional vs. engineered septic systems