About one year from this month, the Department of Ecology's (DOE) National Pollutant Discharge Elimination System (NPDES) Municipal Stormwater Permit will expire on July 31st, 2024. This will happen as part of the regular 5-year permit cycle. The DOE and permit holders are already hard at work on what the 2024-2029 Permit will look like.
The changes to the permit make a significant impact on the local requirements for stormwater regulations in Washington State. Significant updates to be proposed to the permit will include:
- Address tire wear research findings – Road Runoff
- Update Stormwater Planning & Structural Stormwater Control programs
- Consider retrofit implementation program for Phase II
- Enhance Source Control requirements
- Street sweeping program
- PCBs in building materials
NPDES Permit Timeline
- Fall 2022/Early 2023 - Preliminary drafts of permit sections may be provided for specific permit sections for informal comment.
- Late Summer/Fall 2023 - Draft Permits will be issued. DOE will hold a formal public comment period, which will include a workshop and hearing, on the draft permits.
- July 2024 - DOE will make the decision to reissue the NPDES Permits.
Listening sessions were held by the DOE on June 6 and 13, 2022. The presentation can be viewed here. An excellent video of the upcoming changes to the stormwater manual was played during the listening session. I summarized those changes below. You can watch the video on YouTube here.
Early Input
In preparation for the new permit language, several municipal permittees participated in ad-hoc groups hosted by the Washington Stormwater Center and led by local government staff to develop white papers on a variety of topics. The white papers provided early input to the DOE on the next permit cycle and give insight to the opinions of local jurisdictions on how to improve the permit requirements to continue to protect our local creeks.
The white papers focused on the following areas:
- Stormwater Management Action Planning, SMAP White Paper
- Shared Planning Priorities Planning, Shared Priorities White Paper
- Proportionality/Scaling/Tiering and Permit Obligations, Proportionality-Scaling-Tiering White Paper
- Structural Stormwater Controls, SSC White Paper
- Annual Reporting, Annual Reporting White Paper
- Stormwater Action Monitoring, SAM White Paper
- 6PPD-Quinone/Pre-spawn Mortality, 6PPD White Paper
- Operations and Maintenance, Operations & Maintenance White Paper
- Stormwater Management Manual for Western Washington, SWMM White Paper
- Education and Outreach, E&O White Paper
- Equity and Environmental Justice, Equity & Environmental Justice White Paper
- S4F Adaptive Management, S4F White Paper
- Outfall Reporting Standards, Outfall Reporting Standards White Paper
- Source Control and Illicit Discharge and Detection Elimination, Source Control & IDDE White Paper
- Total Maximum Daily Load, TMDL White Paper
- Overlapping Regulations, Overlapping Regulations White Paper
Additional information on the ad-hoc process can be found at https://www.wastormwatercenter.org/permit-assistance/municipal/2024-western-washington-ad-hoc-process/.
Stormwater Manual Updates
The Eastern Washington and Western Washington Stormwater Management Manuals were previously published on different timelines, which created issues in the process. This permit cycle, DOE will publish both manuals on the same schedule.
Planned Changes to Stormwater Manuals
- Statewide Consistency
- General Usability and Clarifications
- New (to the Manual) Pollutants - pollutant specific guidance will be added to the SWMMWW Volume I-1.4 for Nitrogen, PCBs, and 6PPD-quinone
- Climate Change - this will be a new topic added to the manuals. For Western Washington rainfall data from 1948-2009 is used for continuous simulation modeling to design stormwater facilities. DOE explained that they do not think adding the latest 12 years of data would make a significant difference, which I tend to agree with. Instead, they will spend time researching and recommending an alternate way to size stormwater facilities using future predicted rainfall data.This is not likely to be implemented for this manual update.
- Wetlands - they will refine wetland guidance to make the Minimum Requirements 7 and 8 more realistic to achieve while still protecting wetlands.
- Street Sweeping -
- Bioretention Soil Mix - will have several soil mix options added to allow use around phosphorus sensitive lakes. Past soil mixes were found to be a source of phosphorus.
