Mayes County, OK: the USDA septic-suitability picture
Very limited
Mayes County, OK: USDA's soil survey calls 76.5% of the county "Very limited" for a septic leach field. A standard gravity system routinely fails on ground like this; the same share of the county falls in USDA's worst absorption-field bucket outright. The county spans 655.326 square miles, home to 40,144 people.
What this number does and doesn't tell you
USDA's survey covers the whole of Mayes County, OK at once, not any single address. Budget $750-$1,850 for a real perc test on any specific parcel - that's the only figure a permit application accepts.
Mayes County: conventional vs. engineered cost
76.5% of Mayes 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, Mayes County, OK ranks 2,204 most-constrained nationally, and 56 of 77 within Oklahoma.
Related guides
How this rating is built, and its real limits · Conventional vs. engineered septic systems