What Ferry County, WA's soil rates for a septic system

Very limited

Soil across 91.3% of Ferry County, WA rates "Very limited" in USDA's septic-absorption-field interpretation. Practically, that rules out a simple gravity system for most of the county - 91.3% of it sits in USDA's most-constrained bucket. Ferry County, WA is 2,203.23 square miles with a population of 7,543.

What Ferry County's reading doesn't cover

Two lots a mile apart in Ferry County can carry different soil, even though they share one countywide rating. A local percolation test, typically $750-$1,850 (around $1,300 typical), is the only way to know what one lot in Ferry County will actually do.

What a system would cost here

With 91.3% of Ferry County rating "Very limited", a standard gravity system is not a safe assumption here. 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, Ferry County, WA is the 1,142-most-constrained of 3,058 rated counties for septic soil. Within Washington alone it ranks 21 of 39.

Before you act on this

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