Septic soil in Mille Lacs County, MN, by the numbers
Very limited
81.3% of Mille Lacs County, MN's surveyed soil comes back "Very limited" in USDA's own SSURGO data, the county's dominant condition for a septic absorption field. This is the reading that pushes a project toward an engineered system rather than a conventional one, and it covers 81.3% of Mille Lacs County's land. Mille Lacs County, MN is 572.297 square miles with a population of 27,577.
What Mille Lacs County's reading doesn't cover
This is a countywide, area-weighted figure across every soil survey map unit in Mille Lacs County, MN - 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 Mille Lacs County will actually do.
What a system would cost here
With 81.3% of Mille Lacs 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, Mille Lacs County, MN is the 1,978-most-constrained of 3,058 rated counties for septic soil. Within Minnesota alone it ranks 70 of 86.
Further reading
How this rating is built, and its real limits · Conventional vs. engineered septic systems