220 OLYMPIC BLVD VA OUTPATIENT CLINIC 2023-02-09

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