Septic System Program
If you are a Designer or Installer, click here
The Onsite Sewage Program is responsible for evaluating site conditions for onsite septic systems, characteristics of soil in test pits, setting permitting conditions, and issuing permits for onsite septic systems. Onsite Program staff review and comment on land development projects and activities such as subdivisions, Special Use Permits, Boundary Line Adjustments, SEPA documents, and other planning processes proposing onsite wastewater treatment and disposal.
Rules and Regulations
We follow regulatory mandates and guidance documents from the State Legislature, Washington State Department of Health, the Environmental Protection Agency (EPA), and Lewis County Codes.
Learn about: Gravity Installation requirements | septic permits.
Certified Professional Service Providers
Current list of county certified septic installers
Current list of county certified septic pumpers
Current list of county certified septic designers/engineers
Any septic designer or Professional Engineer (P.E.) licensed in the State of Washington may design onsite sewage systems in Lewis County. This list contains the names of those professionals who have indicated they would like to be listed on the Lewis County webpage.
To verify if your designer, engineer, or septic system installer is licensed to practice in Washington state, follow the appropriate link below.
Look up a Designer or Professional Engineer - WA State Department of Licensing
Look up a Contractor - WA State Labor and Industries
Frequently Asked Questions (FAQ's)
Q: Do I need a permit to replace my pump?
A: No. Any work that is conducted within the septic tank does not require a permit. Examples of this type of work includes cleaning, changing, or retrofitting your tank with an effluent filter, measuring sludge accumulation in or pumping the septic tank or pump chamber, or cleaning of the backflow prevention valve.
Q: How much does a septic permit cost?
A: The permit application fees are available here.
Q: Do I need a permit to repair my drainfield?
A: Yes. Any work outside of the septic tank requires a permit.
Q: How do I find out information about my septic system?
A: Stop by the Lewis County Public Works building (2025 Kresky in Chehalis) and fill out a public records request. We should be able to provide you with the as-built drawing of your particular system.
Q: How do I report a failing septic system or onsite system installed without a permit?
A: Call the County Code Compliance Office at 360-740-2718.
Past and Present Training
25-26 January 2008 - WOSSA 12th annual conference, Vancouver, WA
21 February 2008 - Operation and Maintenance (O&M) Training at the Forest Grange, 3397 Jackson Highway.
Helpful Links and Forms
Lewis County Community Development
Lewis County Conventional System Guidance
Test hole guidance document
Septic Permit application - Page 1
Septic Permit application - Page 2