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The expansion of the existing program would increase the sweeping frequency, extend the sweeping season, and add a route.
Expanded street sweeping for water quality is included in the Integrated Plan because it would increase the annual amount of pollutants removed by 40 percent.
Just 16 percent of Seattle’s surface area is streets, but they contribute more than 40 percent of the pollution load in stormwater runoff. Street sweeping is a very cost-effective, flexible stormwater pollution control practice that removes pollutants from streets, keeping them out of storm drains where they would be carried into creeks, lakes, the Duwamish River, and Puget Sound.
Special street sweepers use state-of-the-art regenerative air technology, picking up much finer particles of pollution than a traditional sweeper. These particles can be less than one-sixth the diameter of a human hair. Some of these pollutants include:
Expanded street sweeping would remove an additional 40 tons of pollutants per year at a cost of $11 per pound of pollutant removed per year. To achieve the same benefit with a water-quality treatment facility, the cost would be between $15 and $25 per pound per year. Plus, with street sweeping, we can start the cleaning immediately, and not wait to site, permit, and build a facility. Street sweeping also provides multiple city-wide benefits (clean water, clean streets, and clean air). Extending the sweeping season to include fall leaf-drop season also reduces flooding related to leaf-blocked drainage inlets.