Septic companies in Sonoma, CA

What the ground in Sonoma is like

The USDA soil survey rates mapped ground in Sonoma for septic drain-field suitability across roughly 2.7 square miles. About 100% of the rated ground is classed "Very limited", meaning the soil has one or more features unfavorable for a conventional drain field, and the limits generally cannot be overcome without major soil reclamation, special design or expensive installation.

In Sonoma, the leading limit is depth to a cemented pan: a hard, nearly impermeable layer sits partway down the profile. Water and effluent pond above that pan instead of moving through the full soil column. The survey flags that limit on about 74% of the rated ground here.

The limiting features the survey records most often here:

• Depth to cemented pan73.8%
• Slow water movement68.3%
• Slope13.4%
• Depth to bedrock9.7%

This is survey data for mapped areas, not a substitute for a site evaluation on your own lot. Conditions on a single parcel can differ from the map.

USDA NRCS SSURGO, ENG Septic Tank Absorption Fields · 99.9% Very limited · Depth to cemented pan · 16 map units · 2.74 sq mi · read 2026-08-30