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2020 Stormwater Management Manual

The 2020 Stormwater Management Manual (SWMM) became effective Dec.14, 2020. The manual sets City policy and design requirements for stormwater management on all development, redevelopment, and improvement projects on both public and private property in Portland.
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Updated: April 7, 2021 10:00 a.m.

The 2020 Stormwater Management Manual

The manual 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 Bureau of Environmental Services regularly revises the SWMM to meet current regulatory requirements and to provide current technical standards. Portland City Code 17.38 authorizes the SWMM.

  • The complete manual is available for download— 
  • Review a summary of changes— 
  • Find individual downloads from the manual of design details, forms, vegetation and soils information, and approved manufactured stormwater treatment technologies below.

Design Details

Design details and CADD support are provided for the construction of stormwater management facilities as specified by the 2020 SWMM. For ecoroof and filter strip details, consult the 100 series.


Download a fillable PDF of 2020 SWMM forms to apply for tree credit work in the right-of-way, size stormwater facilities using the simplified approach, develop operations and maintenance plans, record drainage reserves, and apply for special circumstances.

Vegetation and Soils

Find 2020 SWMM plant lists, specifications, vendor information, and options for maintaining a public works permitted project.

Presumptive Approach Calculator

The Presumptive Approach Calculator (PAC)allows design professionals to enter catchment area characteristics and facility details for planters, basins, and green streets. The PAC analyzes the information and determines whether a design meets the water quality, infiltration, and/or flow control requirements of the selected hierarchy level. The PAC creates a report of project information and PAC analysis in PDF format.

Manufactured Stormwater Treatment Technologies

Environmental Services maintains a list of approved Manufactured Stormwater Treatment Technologies (MSTTs). MSTTs on the list have been reviewed and approved to meet the water quality treatment standards of the current SWMM when properly maintained. Projects proposing to use an MSTT must select devices from the list in Chapter 6 and also meet Environmental Services' conditions of use, including the sizing requirements.

MSTT vendors can submit their product for review using the 2020 SWMM MSTT Application Form.

Approved Technologies – Conditions of Approval

Important Dates

The City of Portland 2020 SWMM became effective Dec. 14, 2020. From the effective date until Apr. 6, 2021, project designers could choose to use either the 2016 SWMM or the 2020 SWMM. As of Apr. 7, 2021, all projects must meet 2020 SWMM requirements.

Please note:

  • Land use reviews will be conducted under the manual in place at the time of submittal of a complete application.
  • Building permits will be reviewed based on the permit “in date.”
  • Public Works Projects will be reviewed based on the date the Concept Development Submittal is accepted for review.
  • Capital Improvement Projects and Interagency Projects will be reviewed based on 60% plan submittal date.


Environmental Services provided trainings on the new manual in early 2021. Find video recordings of those trainings below.

Additional Information and Older Manuals