WSR 26-15-127 (26-15)

The Washington state department of ecology (ecology) proposes modification of the phase I municipal stormwater National Pollutant Discharge Elimination System (NPDES) and state waste discharge general permit. The current permit went into effect August 1, 2024, and expires July 31, 2029. The draft of the modified general permit and fact sheet explaining the legal and technical basis for the draft modification are available through 11:59 p.m., September 18, 2026. Ecology will host a public meeting and hearing on the draft modification.

Purpose of the permit: Under the authority of the federal Clean Water Act, Title 33 U.S.C. Section 1251; and the state Water Pollution Control Act, chapter 90.48 RCW, this permit requires local governments to manage and control stormwater runoff so that it does not pollute downstream waters. This permit regulates stormwater discharges in the most highly populated areas in the state.

Background: We develop and administer Clean Water Act NPDES municipal stormwater permits in Washington. Our phase I municipal stormwater permit covers discharges from large and medium municipal separate storm sewer systems (MS4s), except for the Washington state department of transportation's MS4s.

Phase I cities and counties must run a stormwater program that protects local waters just as well as the requirements in Appendix 1 of the permit and ecology's 2024 Stormwater Management Manual for Western Washington.

Seattle, Tacoma, Clark County, King County, Pierce County, and Snohomish County each submitted their own local programs for review. Ecology has now determined these programs are functionally equivalent. This modification adds them to Appendix 10, Part 3, the official list of manuals and ordinances each municipality uses to comply with this requirement.

Submitting comments: Ecology will accept comments on the draft modification to the permit from 9:00 a.m., August 5, 2026, through 11:59 p.m., September 18, 2026. Ecology prefers online comment submission. Comments should reference specific permit text when possible.


•	Submit comments online at https://ecology.commentinput.com?id=3RYHksTdB (preferred method).
•	By United States mail to Abbey Stockwell, Washington Department of Ecology, P.O. Box 47696, Olympia, WA 98504-7696.
•	At our hearing.

Public meeting and hearing: During the comment period we will host an online public meeting and hearing where we will explain the proposed changes to the permit and answer questions prior to the formal hearing. The hearing provides opportunity for the public to give formal spoken testimony on the proposed draft permit. The public hearing begins immediately following the meeting and concludes when public testimony is complete. Spoken testimony will receive the same consideration as written comments.

Online public meeting and hearing: On September 9, 2026, at 2:00 p.m. Register in advance for this meeting at https://waecy-wa-gov.zoom.us/meeting/register/mNTxfyZETsq_siG9AX8-0A. Ecology will review and consider all comments received. We will make appropriate revisions based on public comments, publish an official response to comments as an appendix to the fact sheet, and plan to make a final decision on permit issuance in November 2026.

Copies of the draft permit and fact sheet: The draft permit, fact sheet explaining the legal and technical basis for the permit, and related documents are available online at https://ecology.wa.gov/MS4. You may request hard copies from the water quality program by contacting Jackie Lince at jackie.lince@ecy.wa.gov or 360-407-6600.

Ecology contact: Abbey Stockwell, Washington State Department of Ecology, Water Quality Program, P.O. Box 47696, Olympia, WA 98504-7696, phone 360-280-2934, email abbey.stockwell@ecy.wa.gov.

Americans with Disabilities Act (ADA) accessibility: Ecology is committed to providing people with disabilities access to our information and services by meeting or exceeding the requirements of state and federal laws.

To request an ADA accommodation, email abbey.stockwell@ecy.wa.gov, call 360-280-2934, or call ecology through the Washington telecommunication relay for services including TTY at 711 or through your preferred relay service provider. Visit https://ecology.wa.gov/accessibility for more accessibility information.

Language services: Ecology is committed to providing language services, including translation and interpretation, for people whose primary language is not English. To request these services, email abbey.stockwell@ecy.wa.gov or call 360-280-2934. If you call, ask for an interpreter to be connected with one.

El departamento de ecología está comprometido a ofrecer servicios de idioma, incluidos traducción e interpretación, para personas cuyo idioma principal no es el Inglés. Para solicitar estos servicios, envíe un correo electrónico a abbey.stockwell@ecy.wa.gov o llame al 360-280-2934. Si llama, pida que le conecten con un intérprete.