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Revised Onsite Wastewater Treatment System (OWTS) Manual

Published: February 27, 2018

Permit Sonoma is releasing, for public review and comment, a revised Onsite Wastewater Treatment System (OWTS) Manual. The OWTS Manual is primarily a reformatted version of existing County regulations and standards to comply with the State Water Resources Control Board OWTS Policy Tier 2 Local Area Management Program (LAMP) requirements. The purpose of this document is to allow continued Permit Sonoma authorization for oversight of OWTS countywide.

The OWTS Manual was reviewed by the Land Use Advisory Panel in January 2016 and the general public in March 2016. In May 2016, the Board of Supervisors approved submittal of the OWTS Manual and the County’s LAMP to the North Coast Regional Water Quality Control Board for review and approval. The Regional Water Board provided comments that required edits to the OWTS Manual. It was anticipated that the OWTS Manual would be reviewed and updated periodically to keep pace with new issues, policies, procedures, and technologies affecting the use and management of OWTS.

The revised OWTS Manual was reviewed recently by a subcommittee of the Land Use Advisory Panel in February 2018 and is being published for public review and comment pursuant to Sonoma County Code section 24-31.5 starting on February 22, 2018 and running for twenty (20) days with the end date being March 15, close of business.

We are providing a clean version and a strikeout/underline version. The strikeout version is also annotated with yellow highlights to help the reader understand why a particular change was made or where that provision was located in the prior version. Many provisions simply were moved for clarity and/or organization. Below are links to two folders—one for the clean version and one for the strikeout version.

Revised OWTS Manual -- Clean version:

Revised OWTS Manual -- Strikeout-Underline-Annotated version:

The main changes, relative to the 2016 version, include the following:

  • Re-organization of sections 4, 5, 6, 7 and 17.
  • There are three types of permits: new, replacement and repair. New OWTS are for undeveloped properties. Replacement OWTS are for tank replacements and/or dispersal system replacements for developed sites (previously known as a voluntary repair). And Repairs for the relatively minor work: d-box, valves, etc.
  • The previous voluntary repairs are being eliminated. The typical voluntary repair includes replacing the dispersal system. A new or replacement dispersal system must meet a two (2) foot separation to groundwater, have adequate soil type and depth, and be designed by appropriately licensed professional defined as qualified consultants.
  • Elimination of Class I, II and III classifications which are being replaced with either a Code Compliant or a Legal Non-Conforming systems.
  • Remodel/Rebuild. The remodel/rebuild and minor/major addition thresholds are staying the same. The definitions have been revised for clarity. The requirement relative to roofs has been deleted.
  • The OWTS Manual includes a financial hardship provision that allows a client an exemption from the standards provided a hardship exists as demonstrated by the client and as approved by the Director of Permit Sonoma. The hardship replacement permit will not grant any building permits.
  • The North Coast Regional Water Quality Control Board adopted a revised Waiver of Waste Discharge Requirements that now includes OWTS that cannot meet the two foot (2’) separation to groundwater. The OWTS Manual contains a provision that if the system cannot meet the two foot separation standard, the mitigation is to apply with the RWB for their “wavier.” Local programs cannot waive or mitigate this standard per the state’s OWTS Policy.

A couple things to note: the page numbering and table of contents will be inserted and made correct once the document is final. Also in the “strikeout/underline/annotated” folder there are some documents labeled as “clean”. These sections were not edited and are in this folder so that each folder is complete.