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ice control salts, domestic wastes, lawn chemicals, and vehicle combustion products. Street surface <br /> contaminants contain significant concentrations of particle sizes less than 250 microns(Sartor and <br /> Boyd, 1972). <br /> Pollutant Control Approach: Conduct efficient street sweeping where and when appropriate to <br /> minimize the contamination of stormwater. Do not wash street debris into storm drains. <br /> Facilities not covered under the Industrial Stormwater General Permit may consider a minimum <br /> amount of water washing of streets.All facilities must comply with their local stormwater require- <br /> ments for discharging to storm sewers. Municipal N PDES permittees are required to limit street <br /> wash water discharges and may have special conditions or treatment requirements. <br /> Recommended BMPs: <br /> • For maximum stormwater pollutant reductions on curbed streets and high volume parking <br /> lots, use efficient vacuum sweepers. <br /> Note:High-efficiency street sweepers utilize strong vacuums and the mechanical action of <br /> main and gutter brooms combined with an air filtration system that only returns clean air to the <br /> atmosphere(i.e., filters very fine particulates). They sweep dry and use no water since they do <br /> not emit any dust. <br /> High-efficiency vacuum sweepers have the capability of removing 80 percent or more of the <br /> accumulated street dirt particles whose diameters are less than 250 microns(Sutherland et <br /> al., 1998). This assumes pavements under good condition and reasonably expected accu- <br /> mulation conditions. <br /> . For moderate stormwater pollutant reductions on curbed streets use regenerative air sweep- <br /> ers or tandem sweeping operations. <br /> Note:A tandem sweeping operation involves a single pass of a mechanical sweeper followed <br /> immediately by a single pass of a vacuum sweeper or regenerative air sweeper. <br /> • A regenerative air sweeper blows air down on the pavement to entrain particles and <br /> uses a return vacuum to transport the material to the hopper. <br /> o These operations usually use water to control dust. This reduces their ability to pick up <br /> fine particulates. <br /> These types of sweepers have the capability of removing approximately 25 to 50 percent of <br /> the accumulated street dirt particles whose diameters are less than 250 microns. (Sutherland <br /> et al., 1998). This assumes pavements under good conditions and typical accumulation con- <br /> ditions. <br /> . For minimal stormwater pollutant reductions on curbed streets use mechanical sweepers. <br /> • Note: The industry refers to mechanical sweepers as broom sweepers and uses the <br /> mechanical action of main and gutter brooms to throw material on a conveyor belt that <br /> transports it to the hopper. <br /> • These sweepers usually use water to control dust. This reduces their ability to pick up <br /> fine particulates. <br /> 2019 Stormwater Management Manual for Western Washington <br /> Volume IV-Chapter 3-Page 519 <br />