Puget Sound Innovation Stories

Bainbridge Island Downtown Corridor Bioretention Facilities Maintenance

Maintaining effective stormwater treatment and building partnerships

In 2018, the City of Bainbridge Island identified maintenance needs for the publicly owned and operated bioretention facilities collecting street and sidewalk runoff from the main downtown corridor of Winslow Way, where stormwater flows directly to Puget Sound. The facilities are staggered along a quarter mile stretch of Winslow Way and are a mix of rain gardens, swales, planters, and trees with porous concrete bases. The bioretention facilities provide stormwater treatment as well as a visual barrier for pedestrian and vehicle safety and a landscape aesthetic for the street and business storefronts. Bainbridge Island Rain Garden Mentors (WSU Master Gardeners) voluntarily provided free facility assessment and rain garden training to City Engineering and Operations and Maintenance staff. Through an established Interlocal Agreement between the City and Kitsap County Conservation District, District staff helped with further facility assessment, with finding plant replacements, and with organizing the Washington Conversation Crew for part of the labor.  The maintenance activities included removing sediment and contaminated soils and replacing them with clean soil and mulch, splitting and replacing plants, and removing and replacing inlet rock material. Regular maintenance of these stormwater bioretention facilities is critical to ensuring they continue to prevent toxics from the city’s urban center from entering Puget Sound.

What worked:

  • Removing six inches of contaminated soil from the bioretention systems prevents toxics from entering Puget Sound.
  • Involving many community partners builds community engagement in preventing water pollution.
  • Cross-training and technical assistance between partners saved on costs and created efficiencies.
  • Splitting overgrown plants and spreading them out to fill bare patches saved costs for plant replacement.


  • Effective Operation & Maintenance of stormwater infrastructure improves stormwater treatment and protects Puget Sound water quality.
  • Cross-training and technical assistance between partners builds capacity for continued regular maintenance activities.
  • Improved water quality for nearshore-dependent fish and wildlife.
  • Established LID stormwater maintenance partnerships.
  • Prolonged the life of stormwater infrastructure.


  • Congressional District: 6
  • Legislative District: 23
  • WRIA: 15
  • County: Kitsap


  • City of Bainbridge Island
  • Department of Ecology
  • Bainbridge Island Rain Garden Mentors (WSU Master Gardener Program)
  • Kitsap County Conservation District
  • Washington Conservation Corps
  • Tilz Soils & Compost
  • Sundquist Nursery

Project Funding:

  • City of Bainbridge Island
  • Department of Ecology Capacity Grant

More Info

Publish Date: July 5, 2019
Category: Stormwater
Congressional Districts: Congressional Dist. 6
Legislative Districts: Legislative Dist. 23
Counties: Kitsap
Habitat Types: Puget Sound
Restoration Focuses: Reduce Pollution | Water Quality
Activities: Education | Stewardship
Funding Sources: