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Technical guidance for stormwater projects
Stormwater permit-related drainage design resources
Surface Water Design Manual (SWDM)
A technical manual detailing stormwater management requirements for parcel development in King County, WA.
Applicable in other municipalities that have adopted this manual. It offers help for engineers designing storm drainage systems that reduce problems for downstream neighbors and minimize damage to our natural environment.
View the Surface Water Design Manual
Stormwater Pollution Prevention Manual (SPPM)
Regulatorily-required best management practices (BMPs) for managing stormwater on commercial, multi-family, and residential properties.
Where structural BMPs (area covers, for example) are required, those are described the SWDM (above), citing specific sections in the SPPM.
View the Stormwater Pollution Prevention Manual
Hydrologic and hydraulic modeling software
Runoff Time Series (RTS) and Backwater Analysis are required by the SWDM for sizing detention and infiltration flow control facilities and for conveyances.
The King County Runoff Time Series is not approved for use as of the 2016 and later SWDMs. Approved models and vesting dates are noted on the hydrologic and hydraulic modeling software page.
Stormwater permit-related drainage maintenance resources
Erosion and sediment control for construction sites
Drainage system professionals in King County
Stormwater infrastructure
Stormwater facilities
What are stormwater facilities?
Interactive stormwater facilities map
Wastewater system
Stormwater disposal
Dispose of liquids and solids from cleaning stormwater drains.
Learn more about stormwater disposal
Combined sewer overflow status map
Older combined sewer and storm drain lines were designed to let diluted wastewater overflow untreated into rivers, lakes or Puget Sound to avoid sewage backups in homes and businesses.
Combined sewer overflow real-time map- Seattle area
Combined Sewer Overflow Control - Wastewater Treatment Division
Regional Inflow and Infiltration Control Program
What we are doing to reduce surface water and groundwater leaks into the sewer system.
Learn more about the Regional Inflow and Infiltration Control program
King County Industrial Waste Program
We administer regulations to make sure the wastewater generated by industries is treated properly.
Stormwater legislation and regulations
The United States Environmental Protection Agency (EPA) develops the stormwater regulations, in accordance with the Clean Water Act (CWA).
The Washington State Department of Ecology (Ecology) develops stormwater regulations in Washington State, in accordance with Chapter 90.48 of the Revised Code of Washington, Water Pollution Control.
King County administers its Stormwater Management programs in accordance with King County Code Title 9 - Surface Water Management.
References
Stormwater glossary of terms and abbreviations
Industrial stormwater terms and abbreviations can be confusing. We have compiled a helpful list of terms with definitions.