Street sweeping

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The MPCA is working on development of a credit for street sweeping. We will update this page as this project proceeds.

Project overview

MPCA is working with University of Minnesota researchers and TetraTech to develop a method for crediting street sweeping. The objective is to develop a credit system that can be used by cities and other entities to calculate reductions in pollutant loading associated with street sweeping. These reductions can be applied toward TMDLs or other water quality objectives.

The work includes the following tasks. 1. Conduct a literature review of existing credit methodologies 2. Conduct a survey street sweeping practices conducted by cities 3. Conduct research to establish relationships between sweeping practices and pollutant removal 4. Develop a credit method that can be widely used by cities or other entities.

The project includes a core team consisting of U of M researchers, TetraTech staff, and MPCA staff. A technical support and review team includes representatives from cities, whose role is to provide input as the method is developed.

• Link to project scope of work

Literature review

A literature review was conducted to identify existing street sweeping programs in the United States. Below is some summary information from the review.

Crediting methods vary by governing agency. Over 70% of state MS4 permitting agencies do not require or provide a nutrient or sediment reduction credit for street sweeping, regardless of whether there is an applicable TMDL. Generally, street sweeping is regarded as a good housekeeping measure and annual miles swept are tracked. Most street sweeping programs set schedules and prioritize streets based on traffic volume. Some programs attempt to measure the amount of debris removed by street sweeping. However, relatively few entities establish documented quantifiable crediting methods using research-based estimates of pollutant load removal. Of the roughly 30% of states and the District of Columbia that do have a street sweeping crediting program, half adhere to the Chesapeake Bay TMDL crediting method. While California does not have consistent crediting programs throughout the state, individual permitted entities do have street sweeping crediting programs.

While MS4 permits require varying degrees of quantitative and qualitative documentation on street sweeping activities, this literature review focuses on documenting permitting entities that have an established pollutant reduction crediting methodology. These programs typically require documentation, at a minimum, of the length or area of street swept or a measurement of the materials collected with reductions calculated from established pollutant concentrations or reduction efficiencies or individual load reductions based on permittee-specific data.

Crediting methods vary widely across programs. Some rely on weight conversions of wet or dry material to an estimated reduction of total nitrogen, total phosphorus, or total suspended sediment. Other programs credit based on lane miles swept. Some programs use advanced modeling and provide a wide array of options based on equipment used, number of times swept, and seasonal breaks.

To see the literature review, link here.

Survey of street sweeping practices

The MPCA conducted a survey of cities to determine their street sweeping practices, their interest in a street sweeping credit, and their ability to implement different methods for crediting sweeping. We have not yet fully analyzed the data, but some general conclusions include the following.

• 75 cities responded to the survey and indicated they operate a sweeping program. This was a response rate of close to 50 percent. The responses were distributed geographically across the state and covered a wide range of city sizes (large to small).
• About 78 percent indicated they would be likely to participate in a crediting program
• All but 7 cities can track sweeping information, but 66 percent said they cannot relate material collected to a specific geographic area. This is a question we likely will follow-up with, since being able to relate material to a geographic location is potentially a way of targeting sweeping efforts.
• Most cities estimate volume or mass of material collected, but few measure volume or mass or have the ability to measure dry weight of material collected
• Most cities sweep quarterly or less and most do not specifically sweep in response to fall leave drop

The summary information can be found here