Septic soil in Blaine County, ID, by the numbers

Very limited

Soil across 88.2% of Blaine County, ID rates "Very limited" in USDA's septic-absorption-field interpretation. Practically, that rules out a simple gravity system for most of the county - 88.2% of it sits in USDA's most-constrained bucket. Blaine County covers 2,637.738 square miles and counts 25,261 residents.

This is a county figure, not a parcel figure

Two lots a mile apart in Blaine County can carry different soil, even though they share one countywide rating. A site-specific perc test, usually $750-$1,850, is what a health department will actually require before permitting a lot in Blaine County.

System cost, conventional vs. engineered

Given Blaine 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.

Blaine County's rank among Idaho counties

Nationally, Blaine County, ID is the 1,448-most-constrained of 3,058 rated counties for septic soil. Within Idaho alone it ranks 20 of 44.

Further reading

How this rating is built, and its real limits · Conventional vs. engineered septic systems