What Clay County, MN's soil rates for a septic system
Very limited
Soil across 90.1% of Clay County, MN rates "Very limited" in USDA's septic-absorption-field interpretation. Expect the ground itself to work against a plain gravity system; USDA's strictest bucket alone covers 90.1% of the county. Clay County, MN is 1,045.176 square miles with a population of 66,848.
What Clay County's reading doesn't cover
This is a countywide, area-weighted figure across every soil survey map unit in Clay 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 Clay County will actually do.
What a system would cost here
With 90.1% of Clay 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, Clay County, MN is the 1,258-most-constrained of 3,058 rated counties for septic soil. Within Minnesota alone it ranks 44 of 86.
Related guides
How this rating is built, and its real limits · Conventional vs. engineered septic systems