Seattle Public Utilities Mami Hara, General Manager/CEO

Ballard Natural Drainage

Ballard Natural Drainage system cell

Natural drainage system cells and plantings in the Ballard neighborhood.

What & Why

Seattle Public Utilities (SPU) constructed natural drainage systems (roadside rain gardens) in the planting strip along several blocks in the Loyal Heights neighborhood in Ballard to help improve water quality in local water bodies.

About two-thirds of Seattle is served by a combined sewer system designed to carry sewage from inside homes and businesses along with polluted runoff from streets and rooftops in a single pipe — a “combined sewer.” When the area experiences heavy rain events, the pipes can become overloaded with stormwater and the mixture of polluted runoff and raw sewage can overflow into lakes, streams, and Puget Sound.

The mixture of polluted runoff and raw sewage may harm fish, wildlife, and swimmers in the areas where overflows occur. In 2012, during a year of high-rain, Ballard deposited 54 million gallons of raw sewage and polluted rainwater into Salmon Bay when the combined sewer system reached capacity and overflowed. By keeping polluted runoff out of the sewer system with natural drainage systems, we can leave more room in the pipes for sewage and help prevent these overflows.

This project added natural drainage system cells along 17th, 19th, and 26th avenues northwest and Northwest 75th, 77th and 80th streets in Ballard. The natural drainage system cells are maintained by SPU Operations and Maintenance to ensure stormwater functionality.

Features and benefits

By placing natural drainage systems along the best walking and bicycle routes, the project:

  • Protects our waterways from polluted stormwater runoff, which helps keep families and marine life healthy
  • Provides neighborhood improvements such as pedestrian and bicycle safety
  • Reduces demand on existing pipes and sewage treatment facilities
  • Reduces an average of 1 million gallons of sewage and stormwater from entering the Ship Canal and Salmon Bay annually

Project documents

Maps of rain garden locations (pdf) – April 2016

Ballard Phase 1 hydrologic monitoring report (pdf)

Timeline

  • Summer – fall 2013
    Site selection
  • Winter 2014
    Preferred alternative identified
  • Spring 2014 - spring 2015
    Design completed
  • Spring 2016 - winter 2017
    Construction completed

Connect


Shani Colwell, project manager
shanti.colwell@seattle.gov
(206) 386-1501