What Hamlin County, SD's soil rates for a septic system
Very limited
In Hamlin County, SD, 94.2% of the surveyed land carries a "Very limited" rating for a standard septic drain field. Practically, that rules out a simple gravity system for most of the county - 94.2% of it sits in USDA's most-constrained bucket. Hamlin County, SD is 507.071 square miles with a population of 6,596.
What Hamlin County's reading doesn't cover
Nothing about Hamlin 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 Hamlin County will actually do.
What a system would cost here
With 94.2% of Hamlin 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, Hamlin County, SD is the 763-most-constrained of 3,058 rated counties for septic soil. Within South Dakota alone it ranks 10 of 66.
Further reading
How this rating is built, and its real limits · Conventional vs. engineered septic systems