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Marine Stormwater Utility

Vision: Leading the way to a clean, healthy, and sustainable Puget Sound

Mission: Supporting a sustainable Maritime Industry with innovative stormwater management that benefits local communities and marine life

The Port of Seattle (Port) created the Marine Stormwater Utility (Utility) in 2014 to benefit regional water quality by investing in stormwater infrastructure and supporting the Port’s compliance with stringent and expanding federal, state, and local regulations. The Utility provides services to customers that support an environmentally sustainable maritime industry.

In 2016, the Utility began assessing stormwater infrastructure for all 70+ miles of stormwater pipes and completed the evaluation in 2019. The collected data guide future rehabilitation and reassessment programs.

The Utility completed its first Strategic Plan in 2021, addressing work priorities from 2021 through 2025 that focused on the following:

  • Infrastructure rehabilitation and enhancements including green stormwater infrastructure
  • Sustainability Framework applied to all Port projects
  • Habitat restoration program collaboration to design stormwater projects that are mutually beneficial
  • Equity, diversity, and inclusion to consider the needs of historically marginalized communities
  • System resilience planning to address climate change and ensure our infrastructure is built to last
Stormwater Utility by the Numbers
Decorative996.6 acres drainage area Decorative70 miles of stormwater pipe
Decorative2,720 catch basins and 1,066 manholes Decorative3,455 drains, filters, vaults, etc.
Decorative195 outfalls Decorative186 tenants (Port of Seattle and Northwest Seaport Alliance)


Stormwater Utility Rates

The Utility began collecting stormwater drainage fees in 2016 for all Port Maritime properties, including Port operations, tenants, and those managed by the Northwest Seaport Alliance. These revenues are used to fund evaluation, cleaning, repairs, and upgrades to the Port’s aging stormwater infrastructure, which includes stormwater pipes, treatment systems, catch basins, and manholes that convey stormwater from Port properties into Salmon and Elliott Bays, the Duwamish Waterway, and Puget Sound. Ultimately, the Utility revenues will support rehabilitation of 75 percent of the stormwater infrastructure by 2035, fund ongoing compliance with stormwater permits, and help the Port reach its goal of being the “…greenest and most energy-efficient Port in North America”. For more details, please see the Stormwater Utility Frequently Asked Questions.

The Utility re-evaluates rates annually to determine whether changes are needed to meet short- and long-term maintenance and rehabilitation goals. The Port Commission reviews and approves rates each fall, and customers are informed of rate changes before they become effective in January.

Stormwater Rate Categories 2022 2023 2024
Undeveloped (0 – 15% Impervious Coverage):  
Regular $41.23 $43.13 $46.58
Low Impact $24.14 $25.25 $27.27
Light (16 - 35% Impervious Coverage):  
Regular $63.76 $66.69 $72.03
Low Impact $50.15 $52.46 $56.65
Medium (36 – 65% Impervious Coverage):  
Regular $92.61 $96.87 $104.61
Low Impact $74.49 $77.92 $84.15
Heavy (66 – 85% Impervious Coverage)  $124.25 $129.97 $140.37
Very Heavy (86 – 100% Impervious Coverage)        $146.97 $153.73 $166.03
Annual rates are charged per 1,000 square feet of billable land area  


The Utility had accomplished much in its short history including stormwater management innovations, green stormwater infrastructure, best practices education and awareness, and asset rehabilitation.

Asset Management

Installing tide valve


Dock cleaning

Cleaning catch basin and pipes

A jetter tool for cleaning pipe

Installing pipe repair band inside

Repaired pipe


Stormwater Treatment

Oyster shell barrel at Terminal 102
Treatment media washing machine

Splash Boxx treating roof runoff

Rain garden in Centennial Park



Notable awards garnered by the Utility include the following:

  • American Association of Port Authorities (AAPA) 2017 Environmental Improvement Award for Comprehensive Environmental Management: Formation and Operation of the Marine Stormwater Utility
  • AAPA 2019 Environmental Improvement Award for Environmental Enhancement, Award of Excellence: Innovative Stormwater Operations and Treatment Techniques
  • Port of Seattle 2019 Innovation Award recognized the Utility's media washing machine used to clean oyster shells for reuse in treatment barrels

The Port's 2019 Innovation Award recognized the Marine Stormwater Utility's oyster shell washing machine project

Looking Forward

The Utility Strategic Plan is intended to move us forward to better serve customers and ensure a resilient Utility while supporting the Maritime industry. The strategic plan forms the basis of the annual Utility business plan and budget as reflected in the Port's annual budget. This also helps track progress in meeting the Port’s Century Agenda goals and objectives. The strategic plan will be periodically revisited to update strategies and tasks in support the Port and Utility’s goals.

Questions? Contact the Maritime Stormwater Team at:

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