On-Site Sewage Systems (OSS)

Pursuant to Governor Inslee’s Safe Start-Stay Healthy proclamation

  • The EHU will be closed to the public for the duration of the Order
  • Applications will be accepted by the following methods:
  • No work will commence until payment (check or money order) has been made in full
  • Inspections will be performed in accordance with the Governor’s Proclamation and subsequent addenda (if applicable)
  • Inspection Services Update 6/1/2020 - Cowlitz County has entered Phase 2: all construction, including new work, is allowed under this phase. Please refer to Phase 2 Construction COVID-19 Job Site Requirements for more details. Social distancing of 6 feet or greater will be required at all times. Failure to do so may impact the inspector’s ability to complete your inspection.

For more information regarding the Governor’s response, please click the links below:


The Environmental Health Unit of the Health & Human Services Departments administers the on-site sewage program through the Rules and Regulation of the State Board of Health, Chapter 246-272A WAC.

Staff performs a wide variety of activities to carry out this regulatory oversight, including:

  • plan reviews
  • site evaluations
  • final inspections of individual on-site sewage systems
  • technical assistance to home owners on maintenance and repair of existing systems

The Environmental Health Unit oversees the annual licensing of:

The section also maintains a list of OSS designers and engineers who regularly practice in our County.

There are brochures available with more information about septic systems.

Staff investigates all complaints of failing septic systems.

Permit application forms are available for downloading on our Forms Page. Site evaluations are done by a licensed engineer or on-site septic designer. After the site evaluation is completed, a copy of the evaluation, the septic system design and permit application, along with the appropriate fee will need to be submitted to our office.

Planning on Submitting an OSS Application?

The application materials required for submission to the EHU are unique to each record type. Despite the differences, most septic-related applications within County jurisdiction must include a Planning Clearance Certification (PCC). The Planning Division of Building & Planning reviews requests for PCCs. This service does not extend to projects outside County jurisdiction.

To submit a request for PCC online, click here.

Please Note: The form is not a request for PLANNING CLEARANCE!
While the Building & Planning Permit Center remains closed to the public for the duration of Governor Inslee’s Stay Home - Stay Healthy proclamation, applications for Planning Clearance can be submitted by the following:

Ask your septic professional for help if you do not fully understand any of the form’s questions. Submitting incorrect information may lead to the request being rejected and subsequent project delays.