Stormwater manuals

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​Emerging guidance

Stormwater management is evolving. As such, stormwater management guidance documents are often published in between versions of Ecology’s SWMMs. Stormwater management guidance documents released after publication of the latest SWMMs are provided in the “Additional Resources” folder within the interactive online version of the SWMMs. Direct links are provided below:

• Emerging Guidance in the 2019 Stormwater Management Manual for Western Washington (SWMMWW)
• Emerging Guidance in the 2019 Stormwater Management Manual for Eastern Washington (SWMMEW)

Preparing for our 2024 SWMM updates

We anticipate publishing the next version of our SWMMWW and SWMMEW in July of 2024. The anticipated timeline for the update process:

• Fall 2021: We hosted an open house regarding proposed consistency updates to the SWMMs. 
  • Watch the October 2021 video presentation
• Feb. 2022: Early input was given to Ecology by SWMM stakeholders.
• Spring 2022: We hosted listening sessions regarding early thoughts on proposed SWMM updates.
  • Watch the May 2022 video presentation
• Fall 2022: We provided preliminary draft sections of the SWMMs for informal public comment, and hosted virtual workshops with presentations on the preliminary draft topics.
  • ​​SWMMWW Preliminary Draft package (PDF) 
  • Watch the Western focused November 2022 video presentation
  • SWMMEW Preliminary Draft Package (PDF)
  • Watch the Eastern focused November 2022 video presentation
• August - November 2023: Draft SWMMs are available for formal public comment (see section below for details).

• July 2024: Publish the 2024 SWMMs

Comment on the Draft SWMMs

• Draft Eastern Washington SWMM
• Draft Western Washington SWMM

We prefer to receive comments through our online comment form. 

We will be hosting six informational workshops and hearings to provide information about the proposed changes, answer questions, and allow the public to offer formal testimony. Please see event details below.

Eastern WA Permit and SWMMEW focus 

• SWMMEW Video Presentation

Virtual hearings
Sept. 18, 2023, 9 a.m. - register here
Nov. 6, 2023, 1:30 p.m. - register here

In-person hearing
Oct. 3, 2023, 9:30 a.m.
Moses Lake Civic Center
Council Chambers
401 S. Balsam St
Moses Lake, WA

Western WA Permit & SWMMWW focus

• SWMMWW Video Presentation

Virtual hearings
Sept. 18, 2023, 1:30 p.m. - register here
Nov. 6, 2023, 9 a.m. - register here

In-person hearing
Oct. 17, 2023, 9:30 a.m.
Lacey Community Center
6729 Pacific Ave SE
Lacey, WA

Hearings will follow the workshop and will close after all the testimony is provided. The workshop portion is anticipated to be about two hours.

Equivalent regional stormwater manuals

In some cases, municipal stormwater permittees have the option of either adopting portions of the appropriate Ecology Stormwater Manual or portions of a regional manual determined to be equivalent to the Ecology Stormwater Manual.  For more information, visit the equivalent stormwater manuals for municipal stormwater permits webpage.

Other references for stormwater management and design

Publications

• Low Impact Development Technical Guidance Manual for Puget Sound (December 2012) 
• Eastern Washington Low Impact Development Guidance Manual (June 2013)
• Rain Garden Handbook for Western Washington: A Guide for Design, Installation, and Maintenance (July 2013)
• Aviation Stormwater Design Manual: Managing Wildlife Hazards Near Airports (December 2008)
• Underground Injection Control (UIC) Stormwater Management Program (SWMP) Components (June 2021)

Ecology webpage links

• General stormwater permit page
• Stormwater permittee guidance & resources page
• Low Impact Development (LID) guidance
• Emerging stormwater treatment technologies (TAPE)
• Western Washington Hydrology Model (WWHM)