Stormwater services and information
King County, Washington
Public Rule Notice - Stormwater Manuals
Your comments welcome as we update the Surface Water Design Manual and Stormwater Pollution Prevention Manual
45-day comment period open from April 28, 2021 through June 11, 2021
Under the authority of King County Code Chapter 2.98, this notice is given of the intent to adopt revised versions of the following King County Water and Land Resources Division (WLRD) public rules:
- PUT 8-3-5 Surface Water Design Manual - 243 KB PDF
- PUT 8-8-3 Stormwater Pollution Prevention Manual - 217 KB PDF
Your comments become part of the administrative record.
WLRD will respond to comments as part of the formal administrative record, and finalize the rules taking into account the comments received, if needed.
Learn about stormwater and how to reduce pollution
Reduce stormwater and its pollution at home
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
- Stormwater science
- Stormwater educational videos
- Stormwater glossary of terms and abbreviations
- King County precipitation map (5.1 Mb Acrobat pdf)
- Homeowner requirements in unincorporated King County
- Rain barrel information and sources for the Pacific Northwest
- How to build a rain garden
Rain gardens filter pollution from stormwater and support unusual native plants:
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
2016 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 building beautiful and usable stormwater facilities
- Design Manual training
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
- Improving ditch maintenance for water quality
- Erosion and sediment control for construction sites
- Drainage maintenance standards - self assessment handbook (2005)
- Drainage system maintenance contractor list
- Drainage system design engineer list
Combined sewer overflow status map
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
- Combined Sewer Overflow Control - Wastewater Treatment Division
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.
Stormwater projects and plans
The Restore and Protect Project
Project to identify habitat stressors and recommend restoration and protection actions to improve freshwater quality and aquatic habitat in lowland Puget Sound streams.
King County Stormwater Management Program (SWMP)
Describes King County's 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.
Green River stormwater retrofit planning project
Study modeling and comparing methods to manage stormwater and reduce pollution in developed areas, to establish best practices to manage stormwater.
Miller and Walker Creeks stormwater retrofit planning for improving streams
Project to reduce stormwater pollution in urban creeks that drain into Puget Sound.
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.
Low impact development
Low impact development resources (external link)
The EPA offers Low Impact Development guides, fact sheets and other resources.
- Green River Stormwater Retrofit Planning Project
- Model Low Impact Development Strategies for Big Box Retail Stores
King County's surface water management fee
How your fees pay for these services in Unincorporated King County including Vashon Island.
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
View map layers related to stormwater by clicking the layers icon , expand the "Stormwater Services" group of layers and check those layers you want to view and query including drainage complaints, stormwater facilities, neighborhood drainage projects, and stormwater studies among other things. Click a symbol or area to display the data about it.
May 4, 2021
External article, Seattle Times
Installing a rain garden? You could be eligible for a rebate
Aligning Across Watersheds: A Regional Stormwater Summit
Register to join May 18 & 19, 9am-1pm
Apr. 24, 2021
External article, Seattle Times
How to build a rain garden — a creative, pollinator-friendly way to keep pollution from flowing into Puget Sound
Apr. 8, 2021
External article, Bothell-Kenmore Reporter
Salmon update: King County wants cleaner water, more habitat
Dec. 3, 2020
External article, Seattle Times
Tire dust killing coho salmon returning to Puget Sound, new research shows
Nov. 12, 2020
External report, KING5 News
Chances for a La Niña winter in Pacific Northwest a 'sure bet,' meteorologists say