For more information and recent updates, visit the Bureau of Environmental Services 2020 Stormwater Management Manual webpage, https://www.portland.gov/bes/stormwater/swmm.
Stormwater Management Manual
1.1 Purpose of the Stormwater Management Manual
Urbanization results in removal of vegetation, compaction of soils, and creation of impervious surfaces. These changes increase the amount and rate of stormwater runoff and contribute to increased pollutants washing into creeks and rivers. Pollutants in waterways impact watershed health and habitat value. Construction of impervious areas prevents groundwater recharge. Increased flows can erode stream channels and contribute to localized flooding, combined sewer overflows, and basement sewer backups. Stormwater management maintains and enhances the City’s livability and improves watershed health by mitigating the impacts of urbanization and conserving the existing and future conveyance capacity of storm sewers, drainageways, and combined sewers.
Portland adopted its first citywide Stormwater Management Manual (SWMM) in 1999 and completes regular updates to keep standards current with best practices and regulatory requirements. The SWMM includes retention, water quality, and flow control design standards for stormwater management facilities. Strategies for meeting the requirements in this manual depend on several site factors, including infiltration feasibility and the characteristics of the storm system or drainage basin to which stormwater from the proposed development is discharged. The SWMM allows the City to protect both watershed resources and infrastructure investments as the City experiences development by public and private entities. As each project subject to the SWMM meets the requirements of this manual, it will contribute to achieving these important citywide goals
HISTORY
Adopted July 1, 1999 by Bureau of Environmental Services. Revised September 1, 2002 and filed for inclusion in PPD May 14, 2003.
Revised September 1, 2004 and filed for inclusion in PPD September 29, 2004.
Greenstreet Details interim administrative rule adopted by Director of Bureau of Environmental Services and filed for inclusion in PPD August 10, 2007.
Revised administrative rule adopted by Director of Bureau of Environmental Services August 1, 2008 and filed for inclusion in PPD October 13, 2010.
Revised administrative rule adopted by Director of Bureau of Environmental Services and filed for inclusion in PPD December 20, 2013.
Revised administrative rule adopted by Director of Bureau of Environmental Services August 4, 2016 and effective August 19, 2016.
Revised administrative rule adopted by Director of Bureau of Environmental Services March 22, 2019.
Revised administrative rule adopted by Director of Bureau of Environmental Services July 17, 2019.
Amended by Director of Bureau of Environmental Services December 14, 2020.