Stormwater services and information

Report a drainage or water quality problem
The Stormwater Services Section investigates more than 600 drainage and water quality complaints annually.

Stormwater Pollution Prevention Manual

2009 King County Surface Water Design Manual

Surface Water Management Fee- updated information
How your fees pay for these services

Learn about stormwater and how to reduce pollution

Rainfall washes pollutants from yards and pavement into our local streams, lakes and Puget Sound.

Introduction to stormwater in King County
Learn about the science of stormwater, common problems related to stormwater including causes and solutions, homeowner tips, regulations, and how to get help from King County.

• Stormwater runoff pollution and how to reduce it
• What are stormwater facilities?
• Stormwater science
• Stormwater educational videos 
• Stormwater quiz - test your stormwater knowledge
• Stormwater glossary of terms and abbreviations
• King County precipitation map (5.1 Mb Acrobat pdf)

Reduce stormwater and its pollution at home

• Stormwater Matters video: How you can improve stormwater to help Puget Sound 
• Carwash kit - Find out how to build and use a car wash kit to help reduce water pollution in streams, lakes and Puget Sound.
• Rain barrel information and sources for the Pacific Northwest

• Puget Sound Rain Gardens (external link)
  Rain gardens filter pollution from stormwater and support unusual native plants, and WSU has set a goal for register 12,000 rain gardens in the Puget Sound basin:

  • Wet, shady native plant list
  • Wet, part shade native plant list
  • Wet, sunny native plant list
• Join Puget Sound Partnership on Facebook (external link)

Act to reduce local flooding

• Clear storm drains, reduce local flooding - 15-sec video (WMV) or 30-sec audio (MP3)
• Join Take Winter by Storm on Facebook (external link)

Neighborhood Drainage Assistance Program (NDAP)
Get technical assistance for questions about construction, permitting, and storm drainage and request capital improvements or repairs to address flooding, erosion and sedimentation problems affecting private property in unincorporated King County.

Drainage design resources for professionals

2009 Surface Water Design Manual
Documents and software to help engineers design storm drainage systems that reduce problems for downstream neighbors and minimize damage to our natural environment.

• the Integrated Pond - architectural design tips for buidling beautiful and usable stormwater facilities
• Design Manual training
• Roadside stormwater monitoring and treatment - King County Road Services Division

KCRTS hydrologic and KCBW hydraulic modeling software

• The King County Runoff Time Series (KCRTS) hydrologic model is a required methodology under the 1998 King County Surface Water Design Manual for sizing detention and infiltration flow control facilities.
• The King County Backwater (KCBW) Program is a standard step backwater analysis program for pipe networks, culverts, and simple open channels.

Drainage maintenance resources

• Erosion and sediment control for construction sites
• Drainage maintenance standards - self assessment handbook (2005)
• Drainage system maintenance contractor list
• Drainage system design engineer list
• Notice of SEPA Action: King County Agricultural Drainage Assistance Program for Maintenance of Agricultural Waterways New

Low impact development

Low impact development reports and resources (external link)
The Puget Sound Action Team (PSAT) has some great Low Impact Development Information, Reports, and Resources on their Web site.

• Green River Stormwater Retrofit Planning Project
• Model Low Impact Development Strategies for Big Box Retail Stores
• Low-impact development for roads
  Example project for "green building" in the county's transporation infrastructure, incorporating features such as porous concrete sidewalks and a bioretention facility/rain garden.

Wastewater system

Combined Sewer Overflow Control Program - Wastewater Treatment Division
Combined sewer overflows - Dept. of Health, Seattle/King County
Some old segments of our regional sewers were designed to drain stormwater too, but these combined systems occasionally flood in big downpours.  Combined sewers 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

Regional Inflow and Infiltration Control Program
What King County is doing to reduce the unintended flow of surface water and groundwater into the sewer system.

King County Waterworks Garden stormwater facility
Example of a beautiful and functional stormwater treatment facility that integrates art, technology and nature.

Stormwater plans

King County Stormwater Management Program (SWMP)
Describes our action plan to comply with the National Pollutant Discharge Elimination System (NPDES) phase I municipal stormwater permit issued by the Washington State Department of Ecology.

• 2011 Public Review Draft Stormwater Management Program

King County climate change plan
How King County seeks to reduce greenhouse gas emissions, adapt to projected climate change impacts, and embed mitigation and adaptation into county policy decisions. The plan incorporates issues, goals and actions related to stormwater.

Flooding, stormwater and wastewater breakout session results, King County Climate Change Conference
Review a summary report describing anticipated affects of global warming on flooding, stormwater and wastewater in Washington State with proposed adaptation strategies. Also, look up the flooding, stormwater and wastewater session agenda, presentations, speaker credentials and biographies.

Background information

King County's surface water management fee
We provide surface water management services for Unincorporated King County including Vashon Island, and this page describes the finances that support these services.

Stormwater resources and references
Links to regulatory agencies, environmental organizations, King County stormwater staff directory, and other resources for information on stormwater and related water resource topics.

Interactive map - stormwater complaints, facilities, projects and studies
Note: this link will open a new browser window
Zoom in to view the full set of map layers including drainage complaints, the regional, commercial and residential stormwater facilities, neighborhood drainage projects, stormwater studies, and aerial imagery among other things. Viewing information about individual map features may take some practice: choose the "active" (or queryable) map layer from the layers list, select the tool, and click on one of that layer's features to display associated data.

Annual reports to Ecology for the NPDES Municipal Stormwater Permit

Facility and permit compliance - King County performance measures
These performance measures track King County's compliance with its surface water management permit among other things.

Stormwater treatment and flow controls map - Post 1990 (17.5 Mb Acrobat pdf)
This map shows parcels in King County that were developed after 1990, when stormwater treatment controls and substantially more effective stormwater flow controls started to be required for new development. Thus the map presents a general graphic illustration of where modern stormwater controls are presumed to have been implemented and where development has occurred with no treatment control and little or no flow control. Note, the map is based on the year of latest development and does not represent actual stormwater control. In addition, the area presumed to have modern stormwater controls is likely smaller than what is shown because not all incorporated areas began requiring such controls when unincorporated King County did in 1990.