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Natural drainage system cells and plantings in the Ballard neighborhood.
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.
By placing natural drainage systems along the best walking and bicycle routes, the project:
Maps of rain garden locations (pdf) – April 2016