How Street Sweeping Contributes To Stormwater Management

Street sweeping is a common, inexpensive, non-structural stormwater best management practice (BMP). This simple action removes debris that would otherwise clog the inlets and basins used to store and move rainwater runoff. Researchers have studied whether routine street sweeping reduces the amount of bacteria, nutrients, and trace heavy metals that enter stormwater drains during wet-weather flows. A paired plot experimental design was employed to test this hypothesis.

Cleans The Surface

While sweeping reduces dirt and debris accumulation that can damage vehicles, it also helps to clean the air. Tiny particles from road dust contribute to air pollution levels that exceed health standards. Street sweeping Everett removes these particles, one of the most cost-effective and readily available methods to improve local air quality. Historically, urban runoff pollutants have been captured using “end-of-pipe” strategies such as stormwater ponds and infiltration basins. Research led by U of M researchers demonstrates that sweeping can provide a similar benefit but at the source.

Sweeping streets achieve this new source-reduction strategy before rainstorms, which can capture the sand, grit, and other materials that pollute stormwater runoff to catch basins and waterways. When complemented with other best management practices, such as proper timing, this approach can significantly decrease the amount of sand and grit that reaches streams and rivers.

Prevents Clogging

Since the early 1900s, mechanized street sweeping has removed debris from roadways and parking lots. However, conventional wisdom has long dictated that street sweeping is done for “cosmetic” reasons rather than to control pollutants. Recent studies are challenging that assumption. A properly executed sweeping program can significantly reduce organic and inorganic contaminants and particulate matter contributing to stormwater runoff and foul urban air quality.

By preventing the buildup of materials on the road, the sweeping process prevents sediment from entering the stormwater system and clogging structural controls. It also decreases the load of phosphorus, total nitrogen, and other pollutants on downstream treatment and water quality measures. As a result, a regular street sweeping program is an unsung hero in the war against stormwater runoff, local flooding, and pollution. It is one of the lowest-cost and most effective stormwater management practices. Consequently, it’s a good investment for municipal budgets.

Cleans Catch Basins

Unless otherwise directed, anything on your street and sidewalk ends up in the grated openings of curbs called catch basins. These basins are a vital part of stormwater management, as they help direct water away from streets to avoid street flooding and into the stormwater system to be treated before it flows downstream. But when these basins become clogged, they can’t do their jobs. That’s why street sweeping is so important. While urban runoff pollution has traditionally been captured using “end-of-pipe” approaches like stormwater ponds, there’s untapped potential in “source reduction” practices like street sweeping. These source reduction methods focus on reducing the amount of pollutants entering the stormwater system at the start rather than collecting them toward the end of their journey through urban landscapes. Urban runoff can significantly reduce the quantity of nitrogen and phosphorus leached from paved surfaces by performing enhanced street sweeping up to four times a month.

Prevents Pollution

Researchers have found that street sweeping decreases pollutants that enter the stormwater system. Pollutants like nitrogen and phosphorous leach from organic materials like sticks, leaves, and dirt that accumulate on roadways. These substances drop into catch basins and the stormwater drainage system, carrying them to streams and rivers. Keeping these catch basins clear allows them to divert stormwater from buildings and structures and helps prevent flooding from clogged drains during heavy rains.

Unlike structural stormwater treatment methods, which can be very expensive to install and maintain, street sweeping is an inexpensive best management practice for reducing the quantity of hazardous waste in a community’s waterways. Sweeping at specific times of the year, such as early spring after the snow melts to remove sand and rock salt or in June after trees have dropped their seeds and flowers, can help increase the amount of phosphorus removed from stormwater runoff.