STORMWATER MANAGEMENT MANUAL
Administrative Rule Adopted by Bureau of Environmental Services Pursuant to Rule-Making Authority
What follows is an excerpt from the introduction to the manual:
1.1 Purpose of the Stormwater Management Manual
As the City of Portland is developed, impervious surfaces create increased amounts of stormwater runoff during rainfall events, modifying drainage patterns and flows and disrupting the natural hydrologic cycle. Without stormwater management, these conditions erode stream channels and prevent groundwater recharge. Parking lots, roadways, rooftops, and other impervious surfaces increase the pollution levels and temperature of stormwater transported to streams, rivers, and groundwater resources. Implementing the requirements in this manual helps protect Portland’s water resources, which in turn will provide great benefit to human health, fish and wildlife habitat, recreational resources, and drinking water.
Stormwater management is also critical in terms of protecting Portland’s sanitary and stormwater infrastructure. Increased runoff contributes to combined sewer overflows (CSOs), basement sewer backups, and localized flooding. Implementing onsite infiltration and flow control measures will conserve the existing and future conveyance capacity of storm sewers, drainageways, and combined sewers.
Strategies for meeting the requirements in this manual depend on a number of site factors, including infiltration and system capacity, available infrastructure, proposed development plans, and the storm system or drainage basin the proposed development is in. The standards addressed in this manual are intended to make site-specific improvements across the City and to comprehensively manage stormwater by watershed.
Stormwater management is critical to maintaining and enhancing the City’s livability and improving watershed health. The Stormwater Management Manual (SWMM) allows the City of Portland to protect both watershed resources and infrastructure investments with every development or improvement. As each project meets the requirements of this manual, it will contribute to achieving these important citywide goals.
The text of the 2014 Stormwater Management Manual is also available.
Adopted July 1, 1999 by Bureau of Environmental Services. Revised September 1, 2002.
Filed for inclusion in PPD May 14, 2003.
Revised September 1, 2004. Revision 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. Revision 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.