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| | {{alert|''This page is an edit and testing page use by the wiki authors. It is not a content page for the Manual. Information on this page may not be accurate and should not be used as guidance in managing stormwater.''|alert-danger}} | | {{alert|''This page is an edit and testing page use by the wiki authors. It is not a content page for the Manual. Information on this page may not be accurate and should not be used as guidance in managing stormwater.''|alert-danger}} |
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| − | This page provides an overview of street sweeping and a discussion of water quality benefits and co-benefits of street sweeping.
| + | [[Cost and maintenance information for street sweeping for water quality]] |
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| − | ==Street sweeping overview==
| + | Information on cost and maintenance for implementing a street sweeping program is variable. This is due to several factors, including but not limited to equipment cost and maintenance, frequency of sweeping, operator skills, and disposal methods. |
| − | Street sweeping (also called street cleaning) refers to removal of sediment, litter, or other accumulated substances on roadways, particularly in urban and suburban areas. Street sweeping does not include removal of large quantities of leaves brought to the street/verge for removal, large debris or bulky items; removal of these items is typically handled by large vacuum leaf collectors or dump trucks, respectively.
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| − | Historically, street sweeping was conducted manually by a sanitation worker with a broom or shovel to remove animal waste from horse-drawn vehicles and other detritus on roadways. Mechanical sweepers such as broom systems attached to horse carts came about in the mid-1800s, and in the early 1900s street cleaning wagons sprayed water onto roadways to wash away debris. Motor-driven street sweeping vehicles were patented in the US in 1917.
| + | ==Cost information== |
| | + | Data compiled from the [https://stormwater.pca.state.mn.us/index.php?title=Case_studies_for_street_sweeping case studies in this manual] are illustrated in the adjacent table. The median cost per curb mile is $94 while the mean cost is $487, showing the wide variation in cost information. The cost information provided by the cities typically does not include equipment costs but typically does include disposal costs. |
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| − | Modern street sweeping has improved efficiency of debris removal from roadways dramatically. The focus of street sweeping was simple large “cosmetic” debris removal until the 1970s when concerns about water quality arose. In the decades following, improvements in street sweeping technology focused more on the removal and collection of coarse <span title="Particles with a diameter of between 0.075 and 4.75 millimeters (ASTM basis). Sand is commonly divided into five sub-categories based on size: very fine sand (1/16 - 1/8 mm), fine sand (1/8 mm - 1/4 mm), medium sand (1/4 mm - 1/2 mm), coarse sand (1/2 mm - 1 mm), and very coarse sand (1 mm - 2 mm)."> '''sand'''</span> particle-sized street dirt, and smaller particles which contribute to instream sediment and nutrient pollution when swept off of or washed into waterways. Even when a street was cleaned of large refuse, the amount of tiny particulate matter that could not be effectively removed manually remained to wash-off into waterways following precipitation. Pollutants in stormwater runoff have long been recognized as contributors to <span title="A habitat with water. It includes areas that are permanently covered by water and surrounding areas that are occasionally covered by water. Estuaries, rivers, and marshes are examples of aquatic habitats."> '''aquatic habitat'''</span> degradation, nuisance algal growth, low <span title="Dissolved oxygen (DO) is a measure of how much oxygen is dissolved in the water - the amount of oxygen available to living aquatic organisms."> '''dissolved oxygen'''</span> and toxicity in receiving water bodies . More recently, there has been a focus on street sweeping to remove the <span title="Carbon-based compounds, originally derived from living organisms"> '''organic matter'''</span> produced by street trees (leaves, seeds, flowers, etc), which can contribute significant amounts of [https://stormwater.pca.state.mn.us/index.php?title=Phosphorus phosphorus] to runoff, especially in the fall during leaf drop. <span title="A mixture of solid particles and liquid droplets found in the air. Some particles, such as dust, dirt, soot, or smoke, are large or dark enough to be seen with the naked eye. Others are so small they can only be detected using an electron microscope."> '''Particulate matter (air)'''</span> also poses significant air-quality concerns when entrained in the air due to wind.
| + | Three cities from the case studies (Mankato, St. Cloud, Roseville) reported information on mass or volume of material collected. We used the [[Street Sweeping Phosphorus Credit Calculator]] to estimate cost per pound of phosphorus removed. We used the wet mass method and calculated values for fall and for the remainder of the year. |
| | + | *Mankato: Cost ranged from $293-408 per pound of phosphorus |
| | + | *St. Cloud: Assuming a bulk density of 0.11 kg/L for material collected ([https://openjicareport.jica.go.jp/pdf/11712825_07.pdf]), cost ranged from $174-243 per pound of phosphorus. The City estimates the cost as $195-246/lb-P over a period of four years, with a median cost of $226/lb-P. |
| | + | *Roseville: Cost ranged from $85-119 per pound of phosphorus. The City estimated $193/lb-P in their calculations. |
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| − | ==Water quality benefits of street sweeping==
| + | The City of Prior Lake and University of Minnesota researchers conducted [https://stormwater.pca.state.mn.us/images/5/5e/Prior_Lake_Street-Sweeping-Study_final-9-24-2014.pdf an intensive study of street sweeping in Prior Lake] (Kalinosky et l., 2014). This study included a literature review of other sweeping studies. Cost per mile swept was computed on a monthly basis and ranged from $20-29 per mile. This is similar to the cost data reported by Mankato and St. Cloud, which were the two best documented case studies. Cost effectiveness of sweeping was $41-lb-P in October, less than $100/lb-P during March, April, October, and November, and $400-600/lb-P in the summer months. While tree canopy and cost effectiveness were correlated, other factors such as particle size of solids affected the cost effectiveness of sweeping. |
| − | [[File:Street sweeping benefits.png|500px|thumb|alt=Graphic of street sweeping benefits|<font size=3>Benefits of street sweeping</font size>]] | |
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| − | Roadways accumulate debris and material such as sediment, vegetation, vehicle debris/waste, industrial emission particle deposition, and litter. Harmful pollutants which accumulate on roadways, parking lots, and pavement include metals, organics, nutrients, and particulate matter, which street sweeping helps remove. The effectiveness of street sweeping for removing specific pollutants depends on the timing and methods of sweeping, including season, frequency of sweeping, timing relative to runoff events, type of sweeper(s), sweeping practices such as speed of sweeper and vehicle parking, and the characteristics of the surface being swept (land use, surface roughness, etc.). Below is a qualitative summary focused on pollutant and sweeper type.
| + | A discussion of cost consideration can be found [https://stormwater.pca.state.mn.us/index.php?title=Recommended_street_sweeping_practices_for_water_quality_purposes#Cost_considerations at this link]. |
| − | *Nutrients (phosphorus and nitrogen): In areas with annual leaf drop from trees, nutrient removal is greatest at the time of leaf drop. Some additional benefit occurs with spring sweeping during seed drop. Sweeping at other times of the year provides limited benefit. For more information on phosphorus, see [[Event mean concentrations of total and dissolved phosphorus in stormwater runoff]].
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| − | *Sediment and metals: Sediment removal as discussed here does not include coarse organic sediments, which would be included in the discussion for nutrients. Removal of metals is strongly correlated with sediment removal for most metals. In areas where sweeping cannot be done during winter, sediment removal is greatest immediately following snowmelt, or during snowmelt if streets can be accessed. Sediment buildup increases with length of time between runoff events. Sediment and metal concentrations are typically greatest in industrial and major transportation areas. Sediment associated with first flush is a greater concern in small watersheds with highly connected impervious surfaces. Focused sweeping should occur in areas where there is a significant amount of construction activity. For more information on sediment see [[Event mean concentrations of total suspended solids in stormwater runoff]].
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| − | *Chloride: Chloride is a concern in areas where road salt is applied as a deicer. Sweeping in late winter and early spring can remove residual road salt from impervious surfaces and decrease chloride loads in those areas. However, since chloride is a mobile pollutant, disposal of these sweepings may create concerns in other areas.
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| − | *Bacteria and pathogens: There is limited information on the effectiveness of street sweeping for bacteria and pathogens, though we have a better understanding of factors affecting bacteria loads in runoff. Bacteria concentrations in stormwater runoff are typically greatest in warmer months and in residential areas. Street gutters and grit chambers may be important sources of E. coli contamination due to presence of moist conditions and an organic substrate. Limited studies indicate street sweeping is about 50 to 75% percent as effective for removing bacteria compared to sediment. Dry vacuum sweepers appear to be more effective at removing bacteria compared to other sweepers.
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| − | *Sweeper type: Generally, the effectiveness of sweepers is High efficiency > Regenerative air > Vacuum > Mechanical broom. However, effectiveness varies with a variety of factors, including type of material being collected, targeted pollutant, characteristics of the impervious surface (e.g. roughness), operation factors (e.g. speed), supplemental technology (e.g. use of LIDAR), and whether sweepers are used in tandem (e.g. brush and vacuum). For example, brush sweepers may be more effective that regnerative air sweepers at removing coarse sediment ([https://pubmed.ncbi.nlm.nih.gov/12403017/ Tobin and Brinkman], 2002). For more information see [[Key functionality, limitations, and examples of street sweeping equipment]] and [https://centralvalleysweepingllc.com/different-types-of-street-sweeping-technology/ Different Types of Street Sweeping Technology].
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| − | For more information on stormwater and pollutants in stormwater, [https://stormwater.pca.state.mn.us/index.php?title=Overview_of_basic_stormwater_concepts link here].
| + | {| class="wikitable" |
| | + | |+Cost information for cities from [https://stormwater.pca.state.mn.us/index.php?title=Case_studies_for_street_sweeping street sweeping case studies] |
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| | + | ! City !! Annual cost ($) !! Curb miles swept !! Cost per curb mile |
| | + | |- |
| | + | | Lakeville || 246000 || 1200 || 205 |
| | + | |- |
| | + | | Mankato || 400000 || 11814 || 34 |
| | + | |- |
| | + | | Rochester || 80000 || 11000 || 7 |
| | + | |- |
| | + | | St. Cloud || 70000 || 1825 || 38 |
| | + | |- |
| | + | | Bloomington || 850000 || 342 || 2485 |
| | + | |- |
| | + | | Fridley || 225000 || 1500 || 150 |
| | + | |- |
| | + | | colspan="4" | Costs typically do not include sweeper replacement cost |
| | + | |} |
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| − | ==Co-benefits of street sweeping== | + | ==Comparison of cost effectiveness of street sweeping with other stormwater best management practices== |
| − | [[File:Leaves by drain photo.png|300px|thumb|alt=photo leaves blocking storm inlet|<font size=3>Storm drain inlet partially blocked by leaves, increasing the potential for street flooding.</font size>]]
| + | There is considerable variability in cost effectiveness of different stormwater practices. Some studies show street sweeping to be ineffective for phosphorus removal compared to other practices, while other studies indicate sweeping is highly cost effective. A challenge in comparing studies is gaining access to specific information for each practice. In the case of street sweeping, for example, studies comparing sweeping to other practices rarely provide information about the sweeping practice, such as time of year, type of sweeper, and frequency of sweeping. Another challenge is studies do not contain the same set of bmps, and street sweeping is often not included in these studies. Another concern is that some studies favor specific bmps and therefore the data presented are questionable. |
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| − | Street sweeping provides several benefits in addition to water quality improvement. The most cited co-benefits include improved appearances (aesthetics), improved roadway safety, potential reduction in flooding associated with clogging of stormwater conveyance systems, and reduced air pollution. Many key benefits associated with street sweeping have cumulative impacts as well. For example, increased removal of fine particulate matter can reduce the sediment load to downstream BMPs, extending the life of these practices which provide improved water quality further downstream.
| + | We conducted a cursory review of the literature to get a range of information on cost effectiveness for stormwater practices, including street sweeping. |
| − | *Aesthetics: Sweeping removes debris from streets.
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| − | *Safety: The removal of roadside debris lessens the rate of vehicle accidents and improves driver, biker, and pedestrian safety.
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| − | *Pavement protection: Establishing a routine sweeping schedule in your community will help remove wearing debris and extend the life paved roads and paths.
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| − | *Environmental: Street sweeping helps eliminate the number of plastics and litter that end up on the sides of roads and ends up harming local wildlife.
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| − | *Air quality: Street sweeping removes particles and associated pollutants, including toxics, that could otherwise be transported in air. Regenerative air street sweepers appear to provide the most benefit with regard to collection of small particles and prevention of re-entrainment.
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| − | *Flooding: Removal of debris reduces the likelihood of blocking stormwater conveyances, thus reducing the likelihood of street flooding.
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| − | *Effects on downstream best management practices: Sweeping is a form of source control or <span title="Pretreatment reduces maintenance and prolongs the lifespan of structural stormwater BMPs by removing trash, debris, organic materials, coarse sediments, and associated pollutants prior to entering structural stormwater BMPs. Implementing pretreatment devices also improves aesthetics by capturing debris in focused or hidden areas. Pretreatment practices include settling devices, screens, and pretreatment vegetated filter strips."> [https://stormwater.pca.state.mn.us/index.php?title=Pretreatment '''pretreatment''']</span>, which decreases loading to downstream bmps, extending the life of and decreasing the need for maintenance of those bmps.
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| − | ==References==
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| − | *Bogacki, M., R. Oleniacz, M. Rzeszutek, A. Szulecka, and M. Mazur. 2018. [https://www.e3s-conferences.org/articles/e3sconf/pdf/2018/20/e3sconf_infraeko2018_00009.pdf The impact of street cleaning on particulate matter air concentrations: a case study of a street canyon in Krakow (Poland)]. E3S Web Conf. Volume 45, VI International Conference of Science and Technology INFRAEKO 2018 Modern Cities. Infrastructure and Environment. https://doi.org/10.1051/e3sconf/20184500009.
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| − | *Calvillo, S.J. 2015. [https://pubmed.ncbi.nlm.nih.gov/25367134/ Street dust: implications for stormwater and air quality, and environmental through street sweeping]. Rev Environ Contam Toxicol. 233:71-128. doi: 10.1007/978-3-319-10479-9_3.
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| − | *Central Valley. 2018. [https://centralvalleysweepingllc.com/3-benefits-of-street-sweeping-you-didnt-know-about/ 3 Benefits Of Street Sweeping You Didn’t Know About].
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| − | *Curtis, M. 2002. [http://lshs.tamu.edu/docs/lshs/end-notes/streetsweeping%20for%20pollutant%20removal-1357933594/streetsweeping%20for%20pollutant%20removal.pdf STREET SWEEPING FOR POLLUTANT REMOVAL].
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| − | *Wiese, J.J. 2019. [https://conservancy.umn.edu/bitstream/handle/11299/208968/Wiese_umn_0130M_20747.pdf?sequence=1&isAllowed=y Determining Sources of E. coli Contamination in The Minnehaha Creek Watershed using Rep-PCR DNA Fingerprinting Technology]. A THESIS SUBMITTED TO THE FACULTY OF THE GRADUATE SCHOOL OF THE UNIVERSITY OF MINNESOTA.
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| − | *Zarriello, P.J., R.F. Breault, and P.K. Weiskel. 2002. [https://pubs.usgs.gov/wri/wri024220/pdfs/wrir024220.pdf Potential Effects of Structural Controls and Street Sweeping on Stormwater Loads to the Lower Charles River, Massachusetts]. Water-Resources Investigations Report 02-4220.
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| | + | [[Category:Level 2 - General information, reference, tables, images, and archives/Reference]] |
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| | *[https://stormwater.pca.state.mn.us/index.php?title=MS4_staff_contact_information_and_staff_assignments MPCA MS4 staff contact information] | | *[https://stormwater.pca.state.mn.us/index.php?title=MS4_staff_contact_information_and_staff_assignments MPCA MS4 staff contact information] |
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| − | [[Category:test page]]
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Warning: This page is an edit and testing page use by the wiki authors. It is not a content page for the Manual. Information on this page may not be accurate and should not be used as guidance in managing stormwater.
Cost and maintenance information for street sweeping for water quality
Information on cost and maintenance for implementing a street sweeping program is variable. This is due to several factors, including but not limited to equipment cost and maintenance, frequency of sweeping, operator skills, and disposal methods.
Cost information
Data compiled from the case studies in this manual are illustrated in the adjacent table. The median cost per curb mile is $94 while the mean cost is $487, showing the wide variation in cost information. The cost information provided by the cities typically does not include equipment costs but typically does include disposal costs.
Three cities from the case studies (Mankato, St. Cloud, Roseville) reported information on mass or volume of material collected. We used the Street Sweeping Phosphorus Credit Calculator to estimate cost per pound of phosphorus removed. We used the wet mass method and calculated values for fall and for the remainder of the year.
- Mankato: Cost ranged from $293-408 per pound of phosphorus
- St. Cloud: Assuming a bulk density of 0.11 kg/L for material collected ([1]), cost ranged from $174-243 per pound of phosphorus. The City estimates the cost as $195-246/lb-P over a period of four years, with a median cost of $226/lb-P.
- Roseville: Cost ranged from $85-119 per pound of phosphorus. The City estimated $193/lb-P in their calculations.
The City of Prior Lake and University of Minnesota researchers conducted an intensive study of street sweeping in Prior Lake (Kalinosky et l., 2014). This study included a literature review of other sweeping studies. Cost per mile swept was computed on a monthly basis and ranged from $20-29 per mile. This is similar to the cost data reported by Mankato and St. Cloud, which were the two best documented case studies. Cost effectiveness of sweeping was $41-lb-P in October, less than $100/lb-P during March, April, October, and November, and $400-600/lb-P in the summer months. While tree canopy and cost effectiveness were correlated, other factors such as particle size of solids affected the cost effectiveness of sweeping.
A discussion of cost consideration can be found at this link.
Cost information for cities from street sweeping case studies
| City |
Annual cost ($) |
Curb miles swept |
Cost per curb mile
|
| Lakeville |
246000 |
1200 |
205
|
| Mankato |
400000 |
11814 |
34
|
| Rochester |
80000 |
11000 |
7
|
| St. Cloud |
70000 |
1825 |
38
|
| Bloomington |
850000 |
342 |
2485
|
| Fridley |
225000 |
1500 |
150
|
| Costs typically do not include sweeper replacement cost
|
Comparison of cost effectiveness of street sweeping with other stormwater best management practices
There is considerable variability in cost effectiveness of different stormwater practices. Some studies show street sweeping to be ineffective for phosphorus removal compared to other practices, while other studies indicate sweeping is highly cost effective. A challenge in comparing studies is gaining access to specific information for each practice. In the case of street sweeping, for example, studies comparing sweeping to other practices rarely provide information about the sweeping practice, such as time of year, type of sweeper, and frequency of sweeping. Another challenge is studies do not contain the same set of bmps, and street sweeping is often not included in these studies. Another concern is that some studies favor specific bmps and therefore the data presented are questionable.
We conducted a cursory review of the literature to get a range of information on cost effectiveness for stormwater practices, including street sweeping.
