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Maritime Stormwater Program

Car driving through stormwater

Stormwater is the flow of water generated by precipitation and runoff from land, pavement, building rooftops and other surfaces. These are called 'impervious surfaces' and they do not allow rainfall to absorb into and filter through the soil.

Runoff from these surfaces carries pollutants including oil, grease, metals, and bacteria. Annually, the Maritime Port manages over 1 billion gallons of stormwater runoff from approximately 1,000 acres of facilities.

Marine Stormwater Utility

The Marine Stormwater Utility was established to provide services, facilities, and programs for surface water and stormwater management and  pollution control. A benefit of Utility work is water quality protection of Puget Sound.

Municipal Stormwater Permit

The Port of Seattle holds a Phase I municipal stormwater permit for Maritime Port properties.

The Phase I Permit requires the port to develop and implement a Stormwater Management Program (SWMP)

The Port also publishes an Annual Report as part of the permit requirements.

What does the Maritime Stormwater Program Cover?
The management of stormwater is a crucial part of the Port of Seattle's responsibility in protecting the Puget Sound. Covering 1,000 acres, the Maritime port's paved surfaces are more than 20 times larger than Seattle Center and almost twice the size of New York's famed Central Park.
These surfaces require the Maritime port to manage more than 1billion gallons of runoff annually. 
The Washington State Department of Ecology regulates discharges of stormwater runoff through a permitting process. The port works closely with the agency and our tenants to minimize the impact of stormwater runoff on local waters and their habitat. 

Stormwater Regulatory Overview

The Maritime port operates under a Phase I National Pollutant Discharge Elimination System (NPDES) General Permit for Municipal Stormwater, issued by the Washington State DOE under the Federal Clean Water Act (CWA). Phase I Permits apply to municipalities with populations of 100,000 or more, and to agencies located within the municipality. The Phase I Permit establishes a framework for controlling pollutants from stormwater runoff to the maximum practical extent. Its goal is restoring and maintaining the chemical, physical and biological integrity of our region's waters including rivers, streams, lakes, wetlands, and marine waters.
Most of the Maritime port's property is leased to commercial and industrial tenants. Approximately 70 percent of these properties are covered by a General Industrial NPDES stormwater permit rather than the Phase I Permit. 
Regulatory compliance activities: Municipal Stormwater Permit.
Learn more about Maritime Division's Phase 1 Municipal Permit

Stormwater Information

The Maritime port is a secondary permittee under the NPDES Phase 1 Municipal Stormwater Permit (Phase I Permit) issued by the Department of Ecology. The Phase I Permit regulates discharges to waters of the state from large and medium storm sewer drainage systems. The port is regulated under the Phase I Permit because the stormwater system drains to the Duwamish River, Ship Canal, and Elliot Bay. The port received secondary permit status because it owns and operates its own storm water system within the incorporated area of the City of Seattle.
The Phase I Permit requires the port to develop and implement a Stormwater Management Program (SWMP). The port's SWMP includes the following components:
1. Education Program
2. Public Involvement and Participation
3. Illicit Discharge Detection and Elimination
4. Construction Site Stormwater Runoff Control
5. Post Construction Stormwater Management for New Development and
6. Operation and Maintenance Program
        a. Operation and Maintenance Manual
7. Source Control in Existing Developed Areas
8. Total Maximum Daily Load Requirements
9. Monitoring and Assessment
10. Reporting Requirements
Maritime tenants play a crucial role in protecting water quality in Puget Sound. Any polluting activity has direct effects on the Lower Duwamish, Shilshole Bay or Elliot Bay. The port is actively working with current tenants to improve operations and manage stormwater runoff to protect the natural environment. Detailed tenant information can be found here

Stormwater Permit Coverage

The Washington State DOE regulates how the port handles stormwater runoff on all of the its properties. Stormwater regulations are part of the National Pollutant Discharge Elimination System of permits created by EPA. Approximately 70% of port tenants are covered by one of the following permits:

• Industrial Stormwater General Permit
• Boatyard General Permit
• Construction General Permit
• Individual Permit

The 30% of tenants not covered by an Industrial or Boatyard general permit are subject to the conditions of the NPDES Phase I Municipal Stormwater Permit issued to the Maritime port in 2007. The Municipal Permit requires most other tenants to develop a Stormwater Pollution Prevention Plan that includes structural and operational mechanisms to protect water quality.

View maps indicating what permits properties are subject to - North Extent Map (347 KB, PDF), South Extent Map (366 KB, PDF) If you have additional questions regarding stormwater permit coverage, please refer to your lease or contact your property manager.

State and Local Permit Information








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