Stormwater manuals

Our stormwater manuals provide stormwater permit implementation and management guidance. Contact your municipality or permit administrator to determine which manual you need and for questions regarding implementation of stormwater management guidance.

Ecology's Stormwater Management Manuals (SWMMs)

The dropdowns below provide access to past and present SWMMs.

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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:

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:

  • July 2024: Publish the 2024 SWMMs

Comment on the Draft SWMMs

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 

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

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


Ecology webpage links