As society continues to build more roads, buildings and parking lots we create fewer opportunities for rain and snowmelt to infiltrate into the ground. Instead the precipitation flows directly into our surface waterways, but not without first accumulating debris, litter and other pollutants that gather around these impervious surfaces.
The Environmental Protection Agency considers street sweeping to be a best management practice in helping to reduce stormwater pollution. However, while street sweeping, along with storm drainage practices, is among the oldest methods used to remove pollutants from municipality roadway networks, there are several factors that must be considered before determining where to send the sweepers.
Street sweeping in general is one of the most expensive pollutant removal methods, with removal rates only reaching around five percent. But as a society we realize the importance of completing the task. So when we decide where and how often to allocate resources, we must consider the factors that will make our distribution efforts the most efficient and effective.
The ability to increase efficiency within budget restraints is a critical factor. While many municipalities choose to sweep all their interstate, secondary and local roads a set number of times per year, we took a science-based approach to determine which types of roads tend to collect the most waste. Sweeping roads with curbs is more effective where the sediment or fine particles have not already been washed off the road during rain events. Modeling and GIS analysis can be used to identify target roadways and help set sweeping frequencies. These methods demonstrate that concentrating on certain roadways that are prone to gathering waste and sweeping those more frequently, not because they are interstates or expressways but because they are targeted roads, can actually be more efficient and save money.
While there are many practices in place to reduce the amount of pollutants that reach our surface waters, it is important to analyze each method and find the technique that will make the most measurable impact. Although street sweeping has a lower pollutant removal rate compared to other methods, using GIS to map out the best possible routes helps make the process much more efficient.