What Ida County, IA's soil rates for a septic system
Very limited
Soil across 81.7% of Ida County, IA rates "Very limited" in USDA's septic-absorption-field interpretation. Practically, that rules out a simple gravity system for most of the county - 81.7% of it sits in USDA's most-constrained bucket. Ida County covers 431.513 square miles and counts 6,810 residents.
This is a county figure, not a parcel figure
Nothing about Ida County, IA's SSURGO figure applies to a specific address - it's a county-wide average. A site-specific perc test, usually $750-$1,850, is what a health department will actually require before permitting a lot in Ida County.
System cost, conventional vs. engineered
Given Ida County's rating, plan for the engineered-system range rather than the conventional one. 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.
How Ida County, IA compares
Nationally, Ida County, IA is the 1,954-most-constrained of 3,058 rated counties for septic soil. Within Iowa alone it ranks 82 of 99.
Further reading
How this rating is built, and its real limits · Conventional vs. engineered septic systems