San Mateo County, CA: the USDA septic-suitability picture

Very limited

San Mateo County, CA's SSURGO dominant class comes back "Very limited", covering 60.1% of the county. This is the reading that pushes a project toward an engineered system rather than a conventional one, and it covers 60.1% of San Mateo County's land. For scale: 448.603 square miles and 742,893 people call San Mateo County home.

Before you rely on this for one lot

Two lots a mile apart in San Mateo County can carry different soil, even though they share one countywide rating. 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 San Mateo County, CA

San Mateo 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 San Mateo County, CA compares

Among the 3,058 rated counties on this site, San Mateo County, CA ranks 2,726 most-constrained nationally, and 56 of 57 within California.

Before you act on this

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