Update: Previously, this article stated that the new Stormwater Management Manual (SWMM) would take effect on October 1, 2024. The implementation of the new manual has been delayed. Parts of the SWMM will be posted for a second public comment period. We anticipate a new effective date of early 2025.
The SWMM provides policy and design requirements that govern stormwater management. All development, redevelopment, and improvement projects within Portland on private and public property and in the public right-of-way must meet SWMM requirements.
The SWMM enables the City of Portland to comply with regulatory requirements, protect watershed resources and infrastructure investments, and achieve important citywide goals with every development or improvement.
Along with the SWMM, Environmental Services is also updating Portland City Code Chapter 17.38, Drainage and Water Quality, and proposing a green infrastructure inspection, planting and establishment fee for public works projects. More information on this is provided below.
What are the goals of the changes?
- Improve user navigation of the manual.
- Adjust requirements to apply to fewer projects.
- Increase infiltration in areas that drain to streams to improve watershed health.
- Continue to comply with regulations.
What changes are proposed?
Below is an overview of the proposed changes. For the complete language of the proposed manual and a summary of the changes, documents are available below to help navigate the revised SWMM.
New chapter structure
- Additional chapters that better align with user needs. This includes a new Simplified Approach chapter and moving details and forms into individual chapters.
Changes to Applicability and Exemptions
- Increases impervious area development or redevelopment threshold from 500 square feet to 1000 square feet.
- Expands eligibility for projects to pay the Staff Review Special Circumstances off-site fee to include:
- Sidewalk and shoulder widening projects.
- Public works permit projects in the combined sewer system that cannot use a sedimentation maintenance hole with a sump system.
- Public works permit projects with less than 120 linear feet of frontage.
Changes to Technical Requirements, Engineering Design Assumptions and Standards
- Increase the duration of the water-quality storm size of 1.61 inches of rainfall from 24 hours to 36 hours.
- Require, when feasible, infiltration of the water quality design storm event for sites with at least 0.5 inches per hour infiltration rate in areas that drain to upland streams.
- Update facility designs and details to facilitate infiltration of the water quality design storm event by elevating underdrains.
Simplified Approach
- A new Simplified Approach chapter for easier navigation of the requirements.
- For sites with at least 0.5 inches per hour infiltration rate, changes to infiltration facilities compliance requirements:
- Elevating the underdrain for vegetated facilities.
- Including a soakage trench design with an off-site overflow connection.
Process Changes
- Environmental Services will record operations and maintenance for sites in Multnomah County. A recording fee will be charged.
- Public works permit project applicants will no longer be required to do green infrastructure planting and establishment. Instead, Environmental Services will collect a fee to cover this work. City Council will establish this fee through an ordinance.
Public comment period is closed
Environmental Services accepted public comment on the proposed changes from 8 a.m. July 15, through 5 p.m. August 19, 2024.
Public information sessions
If you were unable to attend an information session, the slides and presentation are posted below.
Public hearing request
Environmental Services did not receive a request to hold a public hearing by 5 p.m. Monday, July 22. The hearing has been canceled.
When will the changes take effect?
The implementation of the new manual has been delayed. Parts of the SWMM will be posted for a second public comment period. We anticipate a new effective date of early 2025. If you would like to be added to the notification list for the second public comment period, please email bescoderule@portlandoregon.gov.
Documents for review
Related code and fee updates
Environmental Services is also taking two legislative items to City Council related to the SWMM. These are not open for public comment but are shared here to provide more complete information. Any comments on these changes can be submitted to City Council as public testimony.
Portland City Code Chapter 17.38 Drainage and Water Quality. Environmental Services is proposing minor updates to the 17.38 that provides the authority for the SWMM and other stormwater regulations. The plan is to bring the ordinance on the consent agenda with the first reading on July 31.
Green Infrastructure Inspection, Planting and Establishment Fee. Environmental Services is asking City Council to approve a change in the process for green infrastructure inspection, planting and establishment for public works projects. If the proposal is approved, public works permit project applicants will no longer be required to complete green infrastructure planting and establishment for the 2-year maintenance warranty period. Instead, Environmental Services will collect a fee to cover this work. The plan is to bring the ordinance to Council for a first reading on August 28. Information about this will be provided during the SWMM information sessions and in the presentation posted above.