Regulations & Permits > Permits & Certifications > Water treatment plants

Water Treatment Plant General Permit

Water treatment plants produce water for drinking and for industrial businesses. The Washington State Department of Health assures drinking water is safe and reliable. Our role ensures that the water treatment byproducts released from these plants do not harm the environment.

Treatment can involve:

  • Filtering and settling out sediment and disease-causing organisms.
  • Using chemicals to kill organisms or remove excess minerals and other contaminants.
  • Adjusting disinfection and chemicals to reduce scaling or corrosion within the delivery system.
We have developed the Water Treatment Plant General Permit (WTPGP) to help treatment facilities comply with state laws and the Federal Water Pollution Control Act. This permit contains specific requirements and conditions for permittees to protect rivers and other waterbodies that receive wastewater discharges.

The current permit expires on Aug. 31, 2019. The new permit is effective on Sept. 1, 2019, and expires on Aug. 31, 2024.

Current permit documents

Water treatment plant reports 

Between 2014 and 2018, we reviewed data concerning water treatment plants in Washington, including:
  • Arsenic monitoring data provided by WTPGP permittees
  • Data about raw water sources, finished water production rates, volumes of wastewater discharged, and populations served for more than 900 water treatment plants statewide
The two reports identified below summarize that work and our findings and conclusions.

Permit reissuance 

We held a public review and comment period of the draft permit, Fact Sheet, Notice of Intent, and a special-purpose questionnaire from Feb. 20 through April 2, 2019. We received comments from the public on the draft permit and considered all of them in developing the final permit. See comments online

We held a workshop and public hearing on March 26, 2019, at our headquarters in Lacey. The purpose of the workshop was to explain the general permit and to answer questions prior to the formal public hearing. The hearing was an opportunity for people to give formal testimony and comment on the proposed draft permit. The public could attend in-person or via webinar.

If you want to be included in future emails concerning the reissuance of the water treatment plant general permit, please email

Does my facility need this permit?

You need this general permit if your water treatment plant discharges wastewater to surface waters and:

  • Produces 35,000 gallons per day or more (monthly total divided by the number of days in the month) of finished drinking and industrial water.
  • The primary function of the facility is treatment and distribution of potable or industrial water.
  • Produces wastewater by filtration processes.
  • Is not a part of a larger permitted facility.

Operations not covered by this permit include discharge of wastewater that is:

  1. Produced by one of the following processes:
    • Ion exchange
    • Reverse osmosis
    • Slow sand filtration
  2. Sent to a publicly-owned treatment works delegated by Ecology.
  3. Released to land where runoff or overflow is impossible.

If any of these are the case, you may need an individual permit.

How to request coverage under this permit

Apply online through SecureAccess Washington and use the WQWebPortal to submit your NOI (Notice of Intent), or contact the permit administrator in your region.

See instructions for applying online.

Previous permit documents

For assistance, contact your permit administrator


For permittees located in the following counties:

Benton, Chelan, Douglas, Kittitas, Klickitat, Okanogan, and Yakima

Marcia Porter
Permit Manager

Eastern Northwest Southwest