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Permit Sonoma › Instructions and Forms › WLS-008 Septic System Application Requirements
Instructions & Forms

WLS-008 Onsite Wastewater Treatment System Application Required Contents

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Version 07/12/2024

Purpose

To provide submittal requirements for Onsite Wastewater Treatment System (OWTS) applications and checklists for OWTS plans and design reports for OWTS applications.

OWTS Applications

The following identifies the minimum submittal requirements for various OWTS application types.

Before submitting an OWTS application, be sure you are applying for the correct type!

More Information About Available OWTS Application Types

Register for an account and apply electronically via Permits Online

OWTS Design Applications for New or Replacement OWTS

  1. OWTS site plan (all sheets in one PDF document)
  2. OWTS design report (all sheets in one PDF document)
  3. Variance request(s), if applicable (variance requests must be submitted as a separate application)

OWTS Construction Applications for New or Replacement OWTS

  1. OWTS site plan (all sheets in one PDF document)
  2. OWTS design report (all sheets in one PDF document)
  3. WLS-043 Non-Standard OWTS Application Acknowledgement form (PDF) (only needed for OWTS utilizing supplemental treatment)
  4. Variance request(s), if applicable (variance requests must be submitted as a separate application)

OWTS Construction Applications for Repairs and New or Replacement Tanks, Pretreatment Units, Interceptor Drains

OWTS site plan (all sheets in one PDF document)

OWTS Design Requirements: Designs must comply with the provisions of the Sonoma County Code (SCC), Sonoma County Onsite Wastewater Treatment System Regulations and Technical Standards (OWTS Manual) and all relevant laws, ordinances, regulations and conditions of approval. Most systems must be designed by a Qualified Consultant (a civil engineer or an environmental health specialist holding a valid California registration).

OWTS Site Plans: Plans shall be of sufficient clarity to indicate the nature and extent of the work proposed. A valid California seal of professional license and signature is required on all sheets for plans prepared by a Qualified Consultant. Plans shall include and clearly identify the applicable items listed under OWTS Site Plan Requirements section below. Additional information may be required to ensure compliance with SCC, OWTS Manual, or to clarify the work proposed.

OWTS Design Reports: Design reports shall be prepared with sufficient clarity, calculations, and supporting documentation to justify the OWTS design. A valid California seal of professional license and signature is required on the cover sheet of design reports prepared by a Qualified Consultant. Design reports shall include the applicable items listed under the OWTS Design Report section below. Additional information may be required in order to ensure compliance with SCC, OWTS Manual, or to support the plans.

Approval of an OWTS Application shall only constitute compliance with the provisions of the County’s OWTS Manual and shall not mean or imply any other land use entitlement or construction approval.

OWTS Site Plan Requirements

The following items are required to be clearly shown and identified on OWTS site plans, if they apply:

  1. Cover Sheet
    1. Name of project
    2. Site address(es)
    3. Vicinity map, location map and site access path
    4. Assessor’s Parcel Number(s)
    5. Project description identifying proposed scope of work
    6. Property owner name and contact information
    7. Qualified Consultant/Designer/Applicant name and contact information
    8. Sheet Index
  2. General items
    1. Seal and signature of Qualified Consultant on all sheets
    2. Date plans prepared and subsequent revision dates
    3. Sheet number in lower right corner (example: sheet 1 of 3)
    4. Space for approval stamps in lower right corner
    5. Drawn to an engineering scale, minimum 1 inch = 20 feet
    6. North arrow and scale (written & graphic)
    7. Legend and list of abbreviations
    8. All proposed and existing OWTS components and features (septic tanks, dispersal areas, reserve replacement areas, sump tanks, pretreatment units, interceptor drains)
    9. Site evaluation test holes/pits labeled and identified (soil profile/pre-perc’s, soil percolation, and groundwater determination) 2, 3
    10. Cross sections of leachlines/dispersal system 2, 3 and interceptor drains3
    11. Contours and elevations (or direction of slope in dispersal area identified by arrows with accurate slope percentage)
    12. All applicable setbacks identified and dimensioned
    13. Existing and proposed buildings, structures, decks, retaining walls, swimming pools, subsurface tanks
    14. Existing and proposed roads, driveways, cut banks, fill placement areas, large trees or other potential installation obstructions
    15. Existing and proposed septic systems, water lines, wells (active & destroyed), springs, lakes, ponds, marsh areas, wetlands, streams, drainage features and underground utilities within 150 feet of any portion of the proposed OWTS components and features, located on-site and off-site/adjacent properties
    16. Specifications and details for septic tanks, sump tanks, pumps, pretreatment units, performance wells, valves, alarms, control panels and all other relevant septic components 1
    17. Construction notes 1
    18. Property lines and rights-of-ways identified on all pertinent views and details
    19. Assessor’s Parcel Numbers for adjacent lands
    20. Existing and proposed easements identified
    21. Erosion prevention/sediment control measures & details

OWTS Design Report Requirements

OWTS design reports are not required for OWTS Construction Applications for Repairs and New or Replacement Tanks, Pretreatment Units, Interceptor Drains.

The following items are required to be clearly shown and identified in the OWTS design report, if they apply:

  1. Cover Sheet
    1. Name of project
    2. Site address(es)
    3. Assessor’s Parcel Number(s)
    4. Property owner name and contact information
    5. Qualified Consultant and contact information
    6. Seal and signature of Qualified Consultant
    7. Date prepared and subsequent revision dates
  2. Project Narrative
    1. Project description/proposed scope of work
    2. Disclosure of existing on-site and off-site conditions
    3. Assumptions and calculation methods pertinent to design
    4. Conclusion addressing adequacy of septic design
    5. Historical site conditions and permitting documentation including septic or operational permit numbers
  3. General Requirements and Attachments
    1. Table of contents with report sections, appendices, etc.
    2. Page numbers
    3. OWTS design calculations
    4. Soil profile evaluation (pre-perc) results
    5. Soil percolation test results
    6. Groundwater table determination results
    7. Pump calculations, pump curve and detail specifications 1
    8. Septic easement information
    9. Approved variance request letter and conditions
    10. Any other supporting documentation relevant to design

Footnotes

  1. These items are not required for OWTS Design Applications.
  2. These items are not required for OWTS Construction Applications New or Replacement Tanks, Pretreatment Units, Interceptor Drains.
  3. These items are not required for OWTS Construction Applications for Repairs.