Street & Parking Lot Sweeping
=Key components of a successful sweeping program
Pollutants collect on surfaces in between storm events as a result of atmospheric deposition, vehicle emissions, winter road maintenance, construction site debris, trash, road wear and tear, and litter from adjacent lawn maintenance (grass clippings). Sweeping of materials such as sand, salt, leaves and debris from city streets, parking lots and sidewalks prevents them from being washed into storm sewers and surface waters. Pollution Prevention and the MS4 Program 15
Timing, frequency and critical area targeting greatly influence the effectiveness of sweeping. This fact sheet provides an overview of studies assessing the benefits of street and parking lot sweeping and guidance on improving the pollution reduction benefits of sweeping programs applicable to MS4 SWPPPs.
Benefits / Pollution Reduction
Regular street sweeping reduces the amount of pollutants that get washed into the storm drain and ultimately discharge to lakes, rivers and wetlands. Targeted pollutants include sediment, trash and debris, leaves, organic matter and nutrients; metals and hydrocarbons. The following pollutant removal efficiencies for total solids (TS), total phosphorus (TP) and total nitrogen (TN) are from a conceptual model developed by the Center for Watershed Protection based on research findings from a variety of studies.
Street sweepings can be filtered and recycled for sanding or filling Image Courtesy of Emmons & Olivier Resources, Inc.
The lower removal efficiencies represent monthly street sweeping by a mechanical street sweeper. The upper efficiencies characterize the pollutant removal efficiencies using a regenerative air or vacuum street sweeper at weekly frequencies. Note that the relatively high frequencies of sweeping generate particularly low removal efficiencies, indicating that sweeping, although an effective aesthetic practice, does not necessarily translate into improved water quality. This is a similar finding of Selbig and Bannerman (2007) in their study of street sweeping in Madison, WI. Even so, every pound of trash and debris removed by sweeping is another pound not entering local waterbodies.
Pollutant removal efficiencies from street sweeping for total solids, total phosphorus, and total nitrogen. Source: Deriving Reliable Pollutant Removal Rates for Municipal Street Sweeping and Storm Drain Cleanout Programs in the Chesapeake Bay Basin. Center for Watershed Protection.
Link to this table
Program Development & Implementation
Surface Sweeping Program Assessment
The Center for Watershed Protection recommends considering the following questions in order to improve the efficiency and effectiveness of your surface sweeping program.
Image Courtesy of Emmons & Olivier Resources, Inc.
- What surfaces or streets in the community are dirtier than others (e.g. have higher street particulate matter loadings compared to others)? Which streets drain to sensitive water bodies? Prioritize streets with higher loadings. The City of Rochester, New York, has an online street sweeping request form. This contributes to the City’s ability to identify dirty streets and surfaces for more frequent cleaning.
- Many cities identify street areas draining to sensitive receiving waters, such as lakes, or to BMPs that could clog with debris and prioritize sweeping on those streets. Consider conducting a street and storm drains investigation, a visual inspection of pollutant accumulation along streets, curbs and gutters, in lake deltas, and storm drain inlets based on the Center for Watershed Protection’s Urban Subwatershed Restoration Manual No. 11: Unified Subwatershed and Site Reconnaissance: A User's Manual. (See the Additional Resources section).
- What proportion of streets and surfaces in the community is swept? Increase this proportion to the extent feasible. The City of Rochester, New York, developed a database to track street sweeping and calculate the total lane miles swept annually. This provides a benchmark for setting goals for future years.
- What is the frequency of street sweeping for public streets? Ensure the frequency is at a minimum twice per year (in the fall after the leaves have fallen and in the spring after the snow is gone to get the sand and winter debris); see the recommendations in the Key Program Elements section below.
- What problems affect the performance of street sweeping (e.g., on-street parking, inadequate budget, untrained operators, distance to storage and disposal facilities)? Once identified, explore means to address the problems.
- What technology is being used? Increase the range of particle size swept by using regenerative air or vacuum sweepers.
- What is the size of the street sweeper fleet? Consider if fleet size is a barrier to efficiency. Many cities hire contractors rather than buy their own sweepers.
- How do you dispose of material collected from the street sweepers? For example, the City of Madison hauls most debris to the county landfill where it gets used as a daily cover for the trash and therefore, is disposed of at no charge. In the fall, when most collected material is leaves, the material is composted at a county site. Some cities filter and recycle their street sweepings for sanding or fill. For additional guidance on reusing street sweepings, see Managing Street Sweepings by MPCA in the Additional Resources section.
An ideal surface sweeping program would answer yes to the following questions. Any missing program elements should be further considered to improve the surface sweeping program:
- Does your community schedule leaf pickup and subsequent street sweeping in the fall to pick up leaves and other organic matter? Do sweepers pick up leaf piles?
- Does your community schedule street sweeping in the early spring to pick up sand, salt and other street deicing materials?
- Does your community use street sweeping equipment (e.g. regenerative-air sweepers, vacuum-assist sweepers) that is capable of picking up a wide range of sediment particles?
- Is tandem sweeping used?