Onsite Waste Treatment Systems (OWTS) Manual
The Onsite Waste Treatment Systems (OWTS) Manual provides the regulations, procedural and technical details governing individual onsite wastewater treatment systems (also referred to as septic systems). State law mandates the State Water Resources Control Board (State Water Board) adopt standards for regulation of onsite waste treatment systems (State Water Board OWTS Policy). The OWTS Manual complies with the State Water Resources Control Board OWTS Policy Tier 2 Local Area Management Program (LAMP) requirements.
OWTS Manual Adoption
The Director of Permit Sonoma published the County of Sonoma’s Onsite Wastewater Treatment System Manual, version 6.0, dated May 21, 2019, pursuant to Sonoma County Code section 24-31.5. The comment period started on June 22, 2019, and ended July 5, 2019. The Director received and considered numerous comments. Revisions included fixing various typographical errors and cleanup language. The statutory requirements of Sonoma County Code section 24-31.5 have been satisfied.
As such, the Director hereby adopts the County of Sonoma’s Onsite Wastewater Treatment System Manual, version 7.0, dated August 15, 2019.
Proposed Revisions Onsite Wastewater Treatment System Manual
OWTS Proposed Revisions 8.4 (PDF: 12.91 MB)
2022 Land Use and Advisory Panel Comments on OWTS Manual v8-4 (PRMD: 1.35 MB)
OWTS Manual Revisions v8-4 Justification (PRMD: 288 kB)
The OWTS Manual and associated documents are presented below.
Entire Manual in a Single Document
Please note you must have Adobe Flash installed on your computer to view this portfolio. Alternatively, you can scroll down to view the manual as individual sections below.
OWTS Portfolio (PDF: 8.99 MB) (Adobe Flash required)
Manual Broken Into Sections / Accessible Version
Each document below is in PDF format and is under 550 kB unless otherwise noted.
- California Plumbing Code Memorandum
- OWTS Cover and Table of Contents
- Section 1 – General
- Section 2 – Sewer Connection Required
- Section 3 – Acronyms and Definitions
- Section 4 – Criteria for All OWTS
- Section 5 – Abatements, Abandonments and Repairs of Failing Systems
- Section 6 – Requirements for Approval of Building Permits
- Section 7 – Site Evaluation Methods and Investigation Requirements
- Section 8 – Criteria for OWTS Components
- Section 9 – Criteria for Standard OWTS
- Section 10 – Criteria for Water Reuse
- Section 11 – Criteria for Commercial, Industrial, and Institutional OWTS
- Section 12 – Non-Standard Experimental and Alternative OWTS Approval Process
- Section 13 – Non-Standard Experimental and Alternative OWTS Standards (Size: 2.61 MB)
- Section 14 – Non-Standard and/or Commercial OWTS Operational Permit and Monitoring
- Section 15 – Vesting Certificates
- Section 16 – Subdivisions and Lot Line Adjustment Requirements
- Section 17 – Variance Requirements
- Section 18 – Variance Prohibition and Special Standards Areas (Size: 3.40 MB)
- Section 19 – Dispute Resolution
- Section 20 – Tier 3 Treatment, Monitoring, Inspection and Sampling for Supplement Treatment Units
- Section 21 – Waterless Toilets
- Appendix A – Experimental and Alternative OWTS