Surface Water Plan

The current SeaTac Surface Water Plan  was developed in 2013; a Surface Water Utility Rate Study was also completed in 2013. Combined, they confirm priorities, outline programs and projects, evaluate the effectiveness of previous plans, evaluate current challenges and opportunities, and establish rates and revenue needs necessary to support future Utility projects and programs.

The City of SeaTac is updating the Surface Water Management Plan and we want your feedback. Please visit this page to read about the new plan and complete the survey.

NPDES Stormwater Permit Program 

Stormwater that moves across the urban landscape picks up trash, sediment, chemicals (automotive fluids and fertilizers) and other pollutants from parking lots, yards, streets and roofs. These pollutants can eventually enter downstream natural waterways if not addressed effectively. The City of SeaTac works to protect stormwater quality in our lakes, streams and the Puget Sound by complying with state and federal water quality regulations.

Issued to the City by the State of Washington Department of Ecology (Ecology), a National Pollutant Discharge Elimination System (NPDES) permit authorizes discharges into and out of SeaTac's municipal storm sewer system. The expiration date of the current five-year permit is July 31, 2024.

Western Washington Phase II Municipal Stormwater Permit

Part of our work involves the development and implementation of a comprehensive Stormwater Management Program (SWMP) to meet permit requirements. SWMP actions and coordinated activities include the following elements:

• Stormwater planning
• Public education and outreach
• Public involvement and participation
• Stormwater system mapping and documentation
• Illicit discharge detection and elimination
• Prevention and control of stormwater runoff impacts from new development, redevelopment and construction activities
• Stormwater system operations and maintenance
• Source control program for existing development
• Water quality monitoring

The SWMP Plan is updated annually to provide written summaries of each permit program component. The document is designed to inform the public regarding how we implement stormwater management activities scheduled each calendar year.

A permit-required Annual Report is also generated and submitted to Ecology pertaining to each year. The online report itemizes specific SWMP information, tracking data, documents and programmatic statements.

A description of current permit compliance with the City of SeaTac NPDES Stormwater Permit is found within the two following program documents:

• The 2024 Stormwater Management Program (SWMP) Plan
• The 2023 Annual Report
  • 2023 Annual Report Attachments

Previous City of SeaTac Annual Reports can be accessed via the Department of Ecology PARIS Database, Permitting and Reporting Information System (wa.gov). 

Known Areas Infeasible for Low Impact Development (LID)

In an effort to promote development and limit the financial impacts on the development community from the state mandated LID requirements that went into effect  January 1, 2017, the City has created a series of outfacing web maps that indicate known areas of infeasibility for LID, by best management practice (BMP) type.  Click here for more information on these maps and how to view them.

Private Stormwater System Inspection Program

The City of SeaTac Public Works Department conducts yearly or every-other-yearly inspections of commercial and multifamily private stormwater systems to ensure the stormwater facilities are being maintained and functioning properly. Link: Private Stormwater System Inspection Program .

Public Education and Involvement

The City of SeaTac has a variety of stormwater education and involvement programs focused on raising awareness and adopting practices which help protect our natural water ways.  These programs include Fish Friendly Car Wash Kits, Storm Drain Markers and annual Green Events full of educational information, and sales of rainbarrels at a reduced rate to the resident.  For more information on these and other programs, follow this link: Stormwater Public Education and Involvement Page . 

Stormwater Management Program Documents & Manuals

King County Surface Water Design Manual 2021
Addendum to 2022 King County Surface Water Design Manual 
Stormwater Pollution Prevention Manual 
Flow Control Application Map 
Water Quality Applications Map    
2012 LID Manual-Technical Guide for Puget Sound 
LID Audit Evaluation Matrix

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