Septic soil in Gem County, ID, by the numbers

Very limited

In Gem County, ID, 92.2% of the surveyed land carries a "Very limited" rating for a standard septic drain field. That reading means a conventional system is a poor bet here - 92.2% of Gem County lands in the strictest "very limited" bucket USDA uses. Gem County covers 559.774 square miles and counts 21,857 residents.

This is a county figure, not a parcel figure

This is a countywide, area-weighted figure across every soil survey map unit in Gem County, ID - never a reading for one specific parcel. A site-specific perc test, usually $750-$1,850, is what a health department will actually require before permitting a lot in Gem County.

System cost, conventional vs. engineered

Given Gem 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 Gem County, ID compares

Nationally, Gem County, ID is the 1,014-most-constrained of 3,058 rated counties for septic soil. Within Idaho alone it ranks 11 of 44.

Before you act on this

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