How Street Sweeping Preserves our Waterways
By Ava Schimnowski, Aquatic Plant Management Specialist Individual Placement /AmeriCorps member at Minnesota Department of Natural Resources Division of Fish and Wildlife
If you park on the street in a city, you’re probably familiar with the routine street sweeping that happens a few times a year. When I was 18 and freshly moved into the city, I ignored the “No Parking” signs, and came out to find that my car had been towed. Little did I know that street sweeping is an essential tool for protecting our waterways.
Stormwater runoff is one of the primary pathways through which pollutants enter rivers, lakes, and streams. Runoff carries with it debris like leaves, dirt, and garbage, which can degrade aquatic habitats, fuel nuisance algal blooms, and deplete dissolved oxygen in water bodies, threatening aquatic life. In urban areas, this is a persistent issue due to the abundance of impervious surfaces like roads, which prevent water from filtering through the ground.
Why Street Sweeping Matters
Street sweeping helps to mitigate these problems by removing pollutants before they can be washed into storm drains. In the fall, leaves are a major culprit, contributing to spikes in phosphorus levels that encourage excessive algal growth. This is a good time to mention that is illegal to sweep your leaves into the street, and rightfully so. In waterways, phosphorus accelerates harmful algae blooms that can reduce oxygen levels and harm fish and other aquatic organisms.
In the spring, residual road salt, used for winter de-icing, becomes another concern. Chloride from road salt doesn’t dissipate or degrade—it stays in the environment, where it can cause long-term damage to aquatic ecosystems. Sweeping helps to remove road salt from streets, reducing the amount that makes its way into waterways, where it can harm aquatic life by disrupting natural water chemistry.
A Brief History of Street Sweeping
Street sweeping has been around for a long time, though its purpose has evolved. Historically, sweeping was conducted manually by sanitation workers with brooms and shovels. In the 19th century, the primary goal was to clean up animal waste from horse-drawn carriages, a bit different than today’s focus on environmental protection.
The first mechanical street sweepers appeared in the mid-1800s, featuring broom systems attached to horse-drawn carts. By the early 1900s, street cleaning wagons were developed that sprayed water to wash away debris. Motor-driven street sweepers were patented in the U.S. in 1917, and they only evolved from there.
A significant shift occurred in the 1970s when street sweeping began to focus on water quality, coinciding with increased environmental awareness brought about by the Clean Water Act. Modern sweeping technology has become far more efficient, with an emphasis on removing fine particles—sand-sized debris and smaller—which contribute to instream sediment and nutrient pollution.
The Effectiveness of Modern Street Sweeping
Recent research highlights just how effective street sweeping can be. A study by Bill Selbig from the U.S. Geological Survey (USGS) showed that streets cleared of leaf litter before a storm can significantly reduce the amount of phosphorus and organic matter that washes into nearby water bodies. This proactive approach helps cities prevent nutrient overloading, which is crucial for maintaining healthy water ecosystems.
Take Minneapolis as an example: its Public Works crews sweep more than 1,100 miles of streets and nearly 400 miles of alleys from curb to curb each season. In addition to these large-scale cleanups, routine sweeping occurs at other times, ensuring that debris doesn’t accumulate between major sweeps.
Conclusion
Street sweeping may seem like a routine part of urban life, but it plays a vital role in preserving water quality. By keeping streets clean of leaves, dirt, and road salt, cities can prevent many of the pollutants that contribute to degraded waterways. Combined with other strategies like vegetative buffers, street sweeping is a key tool in the fight to keep our waterways healthy.
Don’t Get Towed! Check the Minneapolis sweeping schedule
Want to help protect our waters? Adopt a storm drain in Minneapolis!