On-Site Sewage Disposal Permit

(More than 100,000 gallons per day)
What is the purpose of this permit?
Businesses and residences that locate outside areas served by sewer systems often treat and dispose of sanitary sewage through nearby septic tanks and subsurface drain fields. The purpose of this permit is to control discharges so that they do not degrade ground water or surface water quality. In some rural areas, industrial and commercial operations may use on-site systems for treatment and disposal of process wastewater, as opposed to or in addition to residential-strength domestic wastewater (sewage). Ecology is the only agency with jurisdiction over this discharge and may require state discharge permits for either domestic or industrial/commercial on-site systems. For more information on state discharge permits for domestic systems, see http://apps.oria.wa.gov/permithandbook/permitdetail/20. For more information on state discharge permits for industrial/commercial systems, https://fortress.wa.gov/ecy/publications/summarypages/ecy040178.html. Ecology generally requires public ownership, operation, and maintenance of domestic wastewater (sewage) facilities.
Who issues this permit?
Department of Ecology
What activities require this permit?
Large On-site Sewage Systems with any of the following characteristics require coverage under this permit:
  • A design flow exceeding 100,000 gallons per day;
  • Systems whose discharge includes industrial/commercial process wastewater or stormwater;
  • Systems that discharge to the land surface (such as wetlands or infiltration lagoons without a drainfield); or
  • Systems that discharge to surface water (including those that discharge to ground, where groundwater is in hydraulic continuity with surface water).
How much will this permit cost?
There is both an application fee and a coverage fee for this permit; both vary depending on the permit specifications. The fee schedule can be found under WAC173-224.
Where can I get the application for this permit?
The application is called 'Application for a Wastewater Discharge Permit for Discharge of Municipal Wastewater to Groundwater' is online and can be accessed at https://fortress.wa.gov/ecy/publications/SummaryPages/ecy040178.html.
Do I need to include anything with my application?
The design of a large on-site sewage disposal system is first approved by Ecology under WAC 173-240. The applicant must then apply for the Large On-Site Sewage Disposal System Permit for operation of the system under WAC 173-216. When making the decision on your permit, Ecology will consider the applicable laws and rules, the contents of your application, and the background environmental conditions.
How long will it take to review my application?
Ecology will work with applicants to develop a permit issuance schedule that recognizes the applicant's needs. A public notice must be published at least once each week for two consecutive weeks in a single newspaper of general circulation in the county or city in which the district or entity is located. See the NOI instructions for the public notice language requirements. Permit coverage will not be granted sooner than 31 days after the date of the second public notice.
How long is my permit valid?
The permit is good for 5 years.
What is the appeal process for the permit?
You have a right to appeal this permit coverage to the Pollution Control Hearings Board (PCHB) within 30 days of issuance of this general permit. The appeal process is governed by Chapter 43.21B RCW, Chapter 173-226 WAC, and Chapter 371-08 WAC. “Date of receipt” is defined in RCW 43.21B.001(2). To appeal you must do both of the following within 30 days after the date of receipt of issuance of this general permit:
  • File your appeal and a copy of the permit cover page with the Pollution Control Hearings Board (PCHB) during regular business hours.
  • Serve a copy of your appeal and the permit cover page on Ecology in paper form, by mail or in person.  E-mail is not accepted.
Notes / Comments:
For an overview of the permitting process, see the on-line publication Wastewater Discharge Permits in Washington State.
Legal Authority:
Local Government - City or County
Planning Departments
For assistance contact 1-800-917-0043 (Office for Regulatory Innovation and Assistance)
Website: http://mrsc.org/Research-Tools.aspx
Triggering Questions:
  • Will you have one of the following sewage systems: On-site sewage system that exceeds 5,000 gallons per day Sewage system that uses mechanical treatment or lagoons with flows above 3,500 gallons per day A system that receives state or federal construction grants under the Clean Water Act
* Permit information last updated 8/21/2023