Septic soil in Navajo County, AZ, by the numbers

Very limited

Soil across 67.9% of Navajo County, AZ rates "Very limited" in USDA's septic-absorption-field interpretation. Expect the ground itself to work against a plain gravity system; USDA's strictest bucket alone covers 67.9% of the county. Navajo County covers 9,949.496 square miles and counts 109,516 residents.

This is a county figure, not a parcel figure

USDA's survey covers the whole of Navajo County, AZ at once, not any single address. A site-specific perc test, usually $750-$1,850, is what a health department will actually require before permitting a lot in Navajo County.

System cost, conventional vs. engineered

Given Navajo 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.

Where this sits nationally

Nationally, Navajo County, AZ is the 2,530-most-constrained of 3,058 rated counties for septic soil. Within Arizona alone it ranks 9 of 15.

Related guides

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