Sonoma County's SSURGO septic rating

Very limited

Sonoma County, CA's SSURGO dominant class comes back "Very limited", covering 95.4% of the county. A standard gravity system routinely fails on ground like this; the same share of the county falls in USDA's worst absorption-field bucket outright. For scale: 1,575.337 square miles and 485,375 people call Sonoma County home.

Before you rely on this for one lot

This is a countywide, area-weighted figure across every soil survey map unit in Sonoma County, CA - 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 Sonoma County, CA

Sonoma 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.

Sonoma County's rank among California counties

Among the 3,058 rated counties on this site, Sonoma County, CA ranks 604 most-constrained nationally, and 11 of 57 within California.

Related guides

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