Ballard Natural Drainage System (NDS) Project

Photo of plantings in the Ballard neighborhood
Natural drainage system cells and plantings in the Ballard neighborhood.

Project Description

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.

Project Results

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


Construction was completed in winter 2017.

Public Utilities

Andrew Lee, General Manager and CEO
Address: 700 5th Avenue, Suite 4900, Seattle, WA, 98104
Mailing Address: PO Box 34018, Seattle, WA, 98124-5177
Phone: (206) 684-3000

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Seattle Public Utilities (SPU) is comprised of three major direct-service providing utilities: the Water Utility, the Drainage and Wastewater Utility, and the Solid Waste Utility.