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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)

OWTS Manual

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.