What Charles Mix County, SD's soil rates for a septic system
Very limited
Soil across 84.8% of Charles Mix County, SD rates "Very limited" in USDA's septic-absorption-field interpretation. This is the reading that pushes a project toward an engineered system rather than a conventional one, and it covers 84.8% of Charles Mix County's land. Charles Mix County, SD is 1,097.141 square miles with a population of 9,343.
What Charles Mix County's reading doesn't cover
Nothing about Charles Mix County, SD's SSURGO figure applies to a specific address - it's a county-wide average. A local percolation test, typically $750-$1,850 (around $1,300 typical), is the only way to know what one lot in Charles Mix County will actually do.
What a system would cost here
With 84.8% of Charles Mix 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.
Charles Mix County's rank among South Dakota counties
Nationally, Charles Mix County, SD is the 1,712-most-constrained of 3,058 rated counties for septic soil. Within South Dakota alone it ranks 42 of 66.
Further reading
How this rating is built, and its real limits · Conventional vs. engineered septic systems