Washington County's SSURGO septic rating

Very limited

USDA puts Washington County, OR at "Very limited" for septic absorption fields, the dominant reading across 96.7% of the county's soil. Expect the ground itself to work against a plain gravity system; USDA's strictest bucket alone covers 96.7% of the county. For scale: 724.272 square miles and 611,272 people call Washington County home.

Before you rely on this for one lot

USDA's survey covers the whole of Washington County, OR at once, not any single address. 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 Washington County, OR

Washington 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.

Washington County's rank among Oregon counties

Among the 3,058 rated counties on this site, Washington County, OR ranks 408 most-constrained nationally, and 8 of 36 within Oregon.

Related guides

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