You may need an upgrade of your current septic system or a new septic system in accordance with OWTS Manual Section 6. You should retain a qualified septic consultant to assist you with this process. Consultants who provide these services can be located by searching for "Qualified Septic Consultant Sonoma County."
In addition, if you are in a water scarce area as defined in the Sonoma County General Plan, you will need to do dry weather well yield testing.