Franklin County, WA: the USDA septic-suitability picture

Very limited

USDA puts Franklin County, WA at "Very limited" for septic absorption fields, the dominant reading across 56.9% of the county's soil. Practically, that rules out a simple gravity system for most of the county - 56.9% of it sits in USDA's most-constrained bucket. For scale: 1,241.596 square miles and 101,238 people call Franklin County home.

Before you rely on this for one lot

This is a countywide, area-weighted figure across every soil survey map unit in Franklin County, WA - never a reading for one specific parcel. The real answer for one lot is still a site-specific perc test, running about $750-$1,850 (typically near $1,300).

Budgeting for a system in Franklin County, WA

Franklin County's soil reading pushes the likely outcome toward an engineered system rather than a conventional one. Conventional systems run $3,000-$8,000 where they pass; where they don't, engineered alternatives (mound or aerobic treatment, whichever the health department requires) run $10,000-$40,000 - budget toward the higher figure until a perc test says otherwise.

How Franklin County, WA compares

Among the 3,058 rated counties on this site, Franklin County, WA ranks 2,784 most-constrained nationally, and 38 of 39 within Washington.

Related guides

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