Mason County, IL Septic Rating
Mason County's SSURGO septic rating
Very limited
Mason County, IL: USDA's soil survey calls 90.3% of the county "Very limited" for a septic leach field. This is the reading that pushes a project toward an engineered system rather than a conventional one, covering that same share of Mason County's land. The county spans 539 square miles, home to 12,543 people.
What this number does and doesn't tell you
Nothing about Mason County, IL's SSURGO figure applies to a specific address - it's a county-wide average. Budget $750-$1,850 for a real perc test on any specific parcel - that's the only figure a permit application accepts.
Mason County: conventional vs. engineered cost
90.3% of Mason 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, Mason County, IL ranks 1,237 most-constrained nationally, and 49 of 101 within Illinois.
Related guides
How this rating is built, and its real limits · Conventional vs. engineered septic systems