The Role of Street Cleaning in Stormwater Management

The authors have been involved in numerous street cleaning research projects for over 30 years. This paper will give us a unique opportunity to highlight the historical use of street cleaning as a method for reducing stormwater pollutants, and will examine newly emerging street cleaning technologies. There have been many misconceptions concerning this potential stormwater management control. This paper will examine the limitations of street cleaning, and describe how it can be more effective. Street cleaning plays an important role in most public works departments as an aesthetic and safety control measure. Street cleaning is also important to reduce massive dirt and debris buildups present in the spring in the northern regions. Leaf cleanup by street cleaning is also necessary in most areas in the fall. Early Street Cleaning Tests Factors significantly affecting street cleaning performance include particle loadings, street texture, street moisture, parked car conditions, and equipment operating conditions (Pitt 1979). If the 500-1000 μm particle loadings are less than about 75 kg/curb-km for smooth asphalt streets, conventional street cleaning does little good. As the loadings increase, so do the removals: with loadings of about 10 kg/curb-km, less than 25 percent removals can be expected, while removals of up to about 50 percent can be expected if the initial loadings are as high as 40 kg/curb-km for this particle size. The removal performance decreases substantially for smaller particles, including those that are most readily washed off the street during rains and contribute to stormwater pollution. Much information concerning street cleaning productivity has been collected previously in many areas. The early tests (Sartor and Boyd 1972) were conducted in controlled strips using heavy loadings of simulates instead of natural street dirt at typical loadings. Later tests, from the mid 1970s to mid 1980s, were conducted in large study areas (20 to 200 ha) by measuring actual street dirt loadings on many street segments immediately before and after typical street cleaning. These large-scale tests are of most interest, as they monitored both street surface phenomena and runoff characteristics. Many if these tests were conducted as part of the Nationwide Urban Runoff Program (NURP) directed by the EPA (1983). The following list briefly describes these large-scale street cleaning performance tests: • San Jose, California, tests during 1976 and 1977 (Pitt 1979) considered different street textures and conditions; multiple passes, vacuum-assisted, and two types of mechanical street cleaners; a wide range of cleaning frequencies; and effects of parking densities and parking controls. • Castro Valley, California, NURP tests during 1979 and 1980 (Pitt and Shawley 1982) considered street slopes, mechanical and regenerative-air street cleaners, and several cleaning frequencies.