In 2022, the City of Woodbury, in partnership with SWWD, launched the Enhanced Street Sweeping pilot program and saw immediate success. Two years and three street sweepers later, SWWD takes a look at just how effective this BMP has been for stormwater management.
Managing stormwater runoff is important to maintain water quality and reduce environmental impacts. Many of these areas include structural Best Management Practices (BMPs) such as detention ponds and infiltration basins, which are designed to capture and treat stormwater. However, the efficiency of these systems can be highly sensitive to the accumulation of solids, highlighting the importance of regular maintenance to ensure they function as intended.
Street sweeping has long been recognized as a cost-effective and proactive strategy for managing urban stormwater runoff. Not only does it improve the performance of stormwater management systems, but it also offers several added benefits for communities, such as:
- Reduced Clogging and Flooding: Regular street sweeping prevents the accumulation of debris and sediments that can clog storm drains, reducing the risk of flooding during heavy rainfall events.
- Reduced Maintenance Needs: By removing solids from the streets, street sweeping minimizes the need for costly repairs to downstream stormwater infrastructure.
- Improved Pedestrian Safety: Sweeping eliminates hazardous debris such as broken glass, litter, and dirt from walkways, making the streets safer for pedestrians.
- Pest Control: Keeping streets clean reduces the presence of standing water, which can attract pests like mosquitoes.
SWWD conducted comprehensive diagnostic studies to identify pollutants of concern, particularly Total Phosphorus (TP) and Total Solids (TS). Both of these pollutants contribute to water quality degradation in lakes and wetlands, which can cause algal blooms, oxygen depletion, and overall ecosystem imbalance.
The 2018 South Washington Watershed District Six Lake Management Plan Study identified specific TP reduction goals for several key water resources in the region. These goals outline the significant reductions needed to maintain beneficial uses of these water bodies:
- Colby Lake: 1,303 lb/yr (63% of total TP load)
- La Lake: 17 lb/yr (28% of total TP load)
- Markgrafs Lake: 209 lb/yr (63% of total TP load)
- North Wilmes Lake: 265 lb/yr (26% of total TP load)
- South Wilmes Lake: 108 lb/yr (14% of total TP load)
The Enhanced Street Sweeping Plan focuses on eight lakes and four wetlands identified as key water resources within the City’s 2040 Stormwater Management Plan (SWMP). These include:
- Lakes: Bailey, Colby, La, Markgrafs, Powers, Wilmes, Battle Creek, and Carver.
- Wetlands: Tamarack East and West, Evergreen Park, and Marsh Creek Pond.
In total, approximately 655 lane-miles1 of street sweeping are conducted in Woodbury each year, covering both the city’s streets and critical upstream areas that discharge stormwater into key resources.
Street sweeping occurs between April 1st and October 31st, over approximately 140 workdays. Sweeping during this season allows for a more focused and seasonal approach to pollutant removal. This duration takes into account federal holidays and non-operating days due to maintenance, inclement weather, or staffing shortages. On average, the sweeper is operational for about 30 weeks per year.
The pollutant recovery achieved through the enhanced street sweeping plan is substantial. For a fully implemented program, it’s estimated that 979 tons of total solids and 779 pounds of total phosphorus could be removed annually from the streets, preventing these pollutants from entering stormwater systems and impacting water bodies.
One of the key advantages of street sweeping as a BMP is its cost-effectiveness. The estimated cost for phosphorus recovery through street sweeping is between $300 and $350 per pound, making it a highly efficient method for significantly reducing pollutant loads. This level of cost efficiency is a crucial consideration for municipalities striving to meet water quality goals while managing budget constraints.