Roscommon County, MI: the USDA septic-suitability picture
Very limited
USDA puts Roscommon County, MI at "Very limited" for septic absorption fields, the dominant reading across 88.5% of the county's soil. That reading means a conventional system is a poor bet here - 88.5% of Roscommon County lands in the strictest "very limited" bucket USDA uses. The county spans 519.897 square miles, home to 23,932 people.
What this number does and doesn't tell you
Roscommon County's rating is an average across the whole county, not a promise about any one lot inside it. Budget $750-$1,850 for a real perc test on any specific parcel - that's the only figure a permit application accepts.
Roscommon County: conventional vs. engineered cost
88.5% of Roscommon County carrying a "Very limited" reading changes the realistic budget here. Conventional systems run $3,000-$8,000 where they pass; where they don't, engineered alternatives (mound or aerobic treatment, whichever the health department requires) run $10,000-$40,000 - budget toward the higher figure until a perc test says otherwise.
Where this sits nationally
Among the 3,058 rated counties on this site, Roscommon County, MI ranks 1,420 most-constrained nationally, and 64 of 83 within Michigan.
Related guides
How this rating is built, and its real limits · Conventional vs. engineered septic systems