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.

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.

The County of Sonoma is pleased to release the latest draft of our Onsite Wastewater Treatment Systems (OWTS) Manual. We will held Zoom meetings the week of June 26, 2024 to receive public comments and answer questions.

A summary of why the OWTS Manual is being revised, the implications to existing and new development, how this manual interacts with the Total Maximum Daily Load (TMDLs) in the County, and an overview of the changes on the OWTS Revisions can be found on our Regulations Website. We also provide links to comments and responses received from the OWTS design community as part of developing the proposed revisions to the OWTS Manual.

Staff will be presenting a Local Agency Management Program and the revised OWTS Manual to the Board of Supervisors on August 13, 2024 (revised date).

Draft OWTS Manual:

• OWTS Manual version 8.0 (PDF: 10.3 MB)
• OWTS Manual version 8.0 edits shown (PDF: 10.9 MB)

Staff are seeking authorization to submit these two documents to the North Coast RWB as the County’s application for a local OWTS program. This is being done pursuant to the State’s OWTS Policy.

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