How street sweeping helps with stormwater management

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Controlling stormwater runoff is no easy task. High levels of organic and inorganic contaminants in street dust pose a double risk to stormwater and air quality. However, if localities focus their approach on targeting “hot spots” or areas of high concern with high efficiency street sweeping, it has been found that pollutants decrease under such circumstances.

Equipment

Newer sweepers are more efficient than ever at picking up dirt from the streets. Most street sweepers fall into one of the following three categories; mechanical air, vacuum and regenerative. Power sweepers are effective at picking up wet vegetation, gravel, and coarse sand, but are less effective at removing fine particles. Vacuum sweepers have gained popularity due to their ability to remove fine dust more effectively than their mechanical counterparts. Vacuum sweepers are like a household vacuum: they suck in air with a fan, pick up dust and debris, and then exhaust the air.

Regenerative air sweepers have the ability to clean a larger path than vacuum sweepers, remove small debris andThe closed-loop regenerative air system uses the force of a high-speed, controlled air jet created by the powerful blower wheel.TYMCO release less exhaust gases and particles into the environment.

“Regenerative air sweepers were invented in the mid-1960s by the late founder of TYMCO, BW Young,” said Tom Rokas, Inside Sales Manager at TYMCO. “As with a vacuum sweeper, dirt and debris are sucked into a hopper, where the large volume of the hopper drops the heaviest material, while a sieve traps lighter materials such as leaves. Rather than being exhausted, the air is cleaned by a dust separator and then returned to the blowhole of the pickup head in a closed loop cycle.

These sweepers use a blast and suction effect, which has been shown to be more effective in cleaning hard-to-reach places that a vacuum or mechanical sweeper cannot reach. The blast force of the machine is able to reach and clean the entire area that the sweeper is trying to cover.

Regenerative air sweepers are better at picking up smaller particles than mechanical and vacuum sweepers because the blowing and vacuuming action of the collection head, which covers the entire width of the sweeper, reaches inaccessible areas. cylindrical brushes, ”said Rokas.

Street sweeping removes contaminants

Debris and street contaminants are the most easily controllable sources of urban stormwater pollution. The Environmental Protection Agency (EPA) has established the National Pollutant Discharge Elimination Program (NPDES) for stormwater to protect the country’s waterways from pollution, and the agency has developed a number of Best Management Practices (BMPs) that should be included in such a program. .

“When it rains, all the pollutant load ends up in the waterways,” said Shelly Basketfield, head of Seattle’s street cleaning program for water quality. “When it comes to all the pollutants that wash our streets away, it’s much more efficient for us to remove them now than it will be at some point in trying to clean them from the water once the pollutants are already there. . Have been able to show us definitively that street sweeping is one of the most cost effective measures we can use to protect our waterways from street runoff. “

In a report, Evaluating Street Sweeping as a Stormwater Quality Management Tool in Three Residential Ponds in Madison, Wisconsin, published by the USGS, “The variability of street dirt yields was not as high as that of stormwater quality loads. The ability to physically reduce the amount of dirt present on a street surface, described in this study as the efficiency of sweepers, was measured by comparing the yields of street dirt after a sweeper cleaned the streets. in a basin to those measured before cleaning with the sweeper. a weekly program, removed 5% of the average street dirt yield. Each sweeper has shown increasing collection efficiency with increasing street dirt yield. The majority of street dirt yield was measured in April and May of each grade. So in the spring when the yield of street dirt was the highest, the street sweepers were more efficient. Street dirt in the spring also seemed to be more evenly distributed over the street surface than during the rest of the year. t probably due to residues from the spreading of sand in winter. During the summer, 75% of the dirt yield is within 3 feet of the curb. Therefore, street sweeping in the spring could be more effective if the entire street is cleaned and not just the areas close to the sidewalk. “

From the study, experts found a difference in removal efficiency that could be associated with the technology of each sweeper.

“Combining a metal bristle gutter broom with an air blast or vacuum suction appears to increase the ability of street sweepers to pick up available street dirt. The use of regenerative air and power-assisted sweepers per basin street dirt yield of 76% and 63%, respectively. The use of the high-frequency mechanical broom resulted in a 20% reduction in the average yield of pond street dirt. “

Frequency matters

Numerous reports and studies have indicated that there are many variables that impact the actual effectiveness of scanning. These variables include structural BMPs, type of sweeper, sweeper maintenance, operator training, pavement quality and, perhaps most importantly, sweep frequency.

At a minimum, sweeping should take place in early spring (before rain) and in fall after most leaves have fallen. Early spring sweep collects the leftoversRegenerative air sweepers have a pickup head that covers the entire width of the sweeper, allowing for deep cleaning over a wider path.Regenerative air sweepers have a pickup head that covers the entire width of the sweeper, allowing for deep cleaning over a wider path.TYMCO pollutants from winter activities, including sand and ice control material. Street sweeping in the fall should be coordinated with leaf picking in areas with significant deciduous trees.

The city of Rochester, Minnesota, includes the following in its stormwater pollution prevention plans: “The annual sweep cycle usually begins in the spring. A complete sweep of the city is carried out to remove sediment and waste that has accumulated during the winter. Sweeping continues throughout the summer primarily to pick up trash, but also to target areas with known chronic problem areas, such as certain industrial areas or topographical areas that serve as collection points for sediment and debris (for example, downs). hills). Due to the variety of tree species and tree density, fall sweeping requires multiple cycles in multiple areas to pick up leaves. When temperatures permit, the sand is swept from the streets during the winter months ”.

Sweeping materials such as sand, salt, leaves and debris from city streets, parking lots and sidewalks prevents these contaminants from being washed into storm sewers and surface water. The more frequently a roadway is swept, the less quantities and concentrations of contaminants flow into storm sewers and water bodies.

“Historically, street and parking lot sweeping was done for aesthetic purposes,” Rokas said. parking lots and other paved surfaces today.

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