Montgomery County, KS: the USDA septic-suitability picture
Very limited
Montgomery County, KS: USDA's soil survey calls 97.2% of the county "Very limited" for a septic leach field. Expect the ground itself to work against a plain gravity system; USDA's strictest bucket alone covers 97.2% of the county. The county spans 643.594 square miles, home to 30,459 people.
What this number does and doesn't tell you
Nothing about Montgomery County, KS'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.
Montgomery County: conventional vs. engineered cost
97.2% of Montgomery 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.
Montgomery County's rank among Kansas counties
Among the 3,058 rated counties on this site, Montgomery County, KS ranks 352 most-constrained nationally, and 26 of 105 within Kansas.
Further reading
How this rating is built, and its real limits · Conventional vs. engineered septic systems