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Mechanical sweepers have the capability of removing only 10 to 20 percent of the accu- mulated mulated street dirt particles whose diameters are less than 250 microns(Sutherland et al., 111 1998). This assumes pavements under good condition and the most favorable accumulation conditions. . Conduct vacuum sweeping at optimal frequencies. Optimal frequencies are those scheduled sweeping intervals that produce the most cost-effective annual reduction of pollutants nor- mally found in stormwater and can vary depending on land use,traffic volume, receiving Iwater,and rainfall patterns. . Train operators in those factors that result in optimal pollutant removal.These factors include sweeper speed, brush adjustment and rotation rate, sweeping pattern, maneuvering around parked vehicles,and interim storage and disposal methods. . Consider the use of periodic parking restrictions in low to medium density single-family res- 1 idential areas to ensure the sweeper's ability to sweep along the curb. . Establish programs for prompt vacuum sweeping, removal,and disposal of debris from spe- cial events that will generate higher than normal loadings. . Disposal of street sweeping solids must comply with Appendix IV-B: Management of Street Waste Solids and Liquids. I . Consider developing ordinances that prohibit citizens from putting yard debris in the street gut- ters,or doing vehicle maintenance on the street. I . Provide incentives to property owners for installing permeable pavement parking areas and driveways. I . Consider installing catch basin inserts in high use areas to remove trash and yard debris before it enters the system. . Implement a storm drain stenciling program to label and educate the public not to dump mater- ials into storm drains or onto sidewalks, streets, parking lots, and gutters. . Provide household hazardous waste collection and used oil recycling for citizens to avoid Iillegal dumping. I I I I I I 2019 Stormwater Management Manual for Western Washington Volume IV-Chapter 3-Page 520