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Florida Stormwater Particulate Removal Studies 2007, 2011 and 2019



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The following interview was conducted, and article written by, Ranger Kidwell-Ross, M.A., Editor of

The Bottom Line: If You Don't Read Any Further...

Recovery Chart

Editor's Note: Click on the chart shown above to access a PDF file/handout of the above information suitable for printing.


Summary of Conclusions

The 2019 University of Florida/Florida Stormwater Association Phase III Study and Report linked above, and referenced in the interview below, confirmed data collected in the 2011 Phase II Study it was designed to build upon.

The study found street sweeping to be the most economical and dominant practice that MS4s can implement and optimize in order to maximize nutrient and particulate matter (PM) recovery benefits to urban drainage systems and the environment. The study, which involved a total of 14 Florida MS4s, also showed conclusively that recovery of particulates matters!

Three Methods Graphic

The findings included that the median cost of recovery via street sweeping for total nitrogen (TN) and total phosphorus (TP) was $189 and $294 per pound, respectively, based on 2020 costs. By multiplying these values by the recovered nutrients' mass on an annual basis, the cost of street sweeping is obtained. The miles that need to be swept to recover 1.0 lb of TP and/or TN can then be calculated.

The median cost of recovery via catch basin maintenance showed removal of TN to be $1,162 per pound, and for TP it was $1,894 per pound, 2020 costs. The cost of catch basin cleaning can then be obtained for catch basins on an annual basis as an upper limit of cost. To recover 1.0 lb of TN and/or TP, the number of catch basins needed can then be calculated.

To calculate the cost of recovery via other best management practices (BMPs), considered to be composed of hydrologic functional units (HFUs), the same summary in the Phase II report showed: The cost of BMP construction per pound of nitrogen removed is $2,173, and for phosphorus is $12,006 per pound (from Florida-based BMP category) 2020 costs. The results are the cost of recovering TN and TP from these BMPs. To recover 1.0 lb of TN and TP, the number of BMPs needed can then be calculated.

The differential benefit of street sweeping for a moderate size MS4 in Florida – think "cost savings" – when compared to adding the number of any other BMPs needed for an equivalent load recovery, has been shown to be equivalent to tens of millions of dollars.

The above was documented through spreadsheet particulate matter data provided by the Florida Department of Environmental Protection and presented at the Florida Stormwater Association's Annual Conference in 2018.

John Sansalone

The following chronicles the audio interview (linked above) conducted in December of 2019 with Dr. John Sansalone, the Eckler Professor of Excellence in Engineering at the University of Florida. Dr. Sansalone also works closely with the Florida Stormwater Association.

He was the principal author of the comprehensive study on stormwater pollution control, referenced above, that was completed in 2019. The 2019 study was built upon similar data from studies completed in 2007 and 2011.

WorldSweeper: Thank you for taking the time to discuss the information detailed in the University of Florida/Florida Stormwater Association's 2007, 2011 and 2019 water quality studies you spearheaded.

Dr. Sansalone: Thank you for this opportunity. [The information I have] can really benefit your reading audience, the ones who carry out a very valuable task, one that is good for the municipalities, the environment and, frankly, good for human health.

WorldSweeper: There are a lot of places in the country where stormwater management isn't considered as important as it is in Florida, but water quality is getting more and more critical throughout the United States and the world all the time. I believe what you have to say will be good information for water quality professionals around the world because getting ahead of the curve is ideal, rather than playing catch-up like we are currently on all of the U.S. coastlines. Please educate our listeners about the scope of the problem in Florida and what it is you are trying to bring out in the study.

Dr. Sansalone: The study that was completed this year is really part of a trilogy of studies that were first initiated in 2007. The first study wasn't a paper study but, rather, looked at documentation of maintenance practices in general, not only in Florida but elsewhere.

[We were trying to find out] if we could classify the chemical loads of interest in the particulate matter being swept into, deposited on, remaining in or generated from pavement systems. [We wanted this to include everything] from coarse gravel, biogenic materials like leaves and grass clippings, all the way down through find silts and even clay-sized particles that end up on pavement.

The chemicals of interest in the state of Florida, and many other places as well, have been, predominantly, nutrients: nitrogen and phosphorus. My [actual] background is one with respect to heavy metals, which I studied during my tenures at the University of Cincinnati and Louisiana State University. Metals are probably, other than particulate matter, the dominant chemical of concern in these environments. However, at the University of Florida [and in these studies] the main focus has been nutrients.

I have also gone to Italy to teach and do research. Their focus has been metals, but as time moves on there is much more interest also in the treatment of or, even better, the recovery of, nutrients and particulate matter in urban environments. Europeans are well organized and have well-defined and effective street sweeping programs. They are much more organized and developed than what I have seen here in the United States. I can attest that the Italians do great organizational work in terms of street sweeping.

Even given their tight urban environments they still require vehicles to move to certain sides of the streets on certain days, [in accordance with] a regular street sweeping and cleaning process. In much of Europe as well as in Italy, where I am most familiar, they have combined sewers. As a result they must do their best to eliminate particulate matter before it enters their roadway drainage systems.

When we started in 2007 we didn't go out and collect data. Rather, we examined data that were already available. Our question at the time was "Can we take all these disparate results and all of the disparate techniques that had very wide variability, and can we design a study that is Florida-specific? One where we can reduce that variability so that in the end we can produce a yardstick – or metric – that says 'If you recover X pounds of particulate matter, associated with that X pounds will be Y pounds of nitrogen and/or Z pounds of phosphorus.'"

The concept is simple but becomes more complex because you have to deal with all kinds of moisture content, since all types of particulate matter contain moisture even though it may appear to be dry. So, we had to tease out moisture content results.

After that study we were able to obtain funding through the Florida Stormwater Association (FSA). With the help of FSA's Kurt Spitzer, we lined up 14 MS4s to help fund the study. We then set up a protocol and experimental program for them to collect data. The land uses we looked at were highway, commercial and residential.

Highway, especially, is a distinct land use because it is dominated by pavement. The loads in the highway environment are dominated by vehicular traffic. This was in 2008 and the municipalities conducted sampling to our specifications. That provided us with well over 500 particulate matter samples that had to be analyzed. This all took a considerable amount of time so we didn't finish that report until 2011.

The report focused on what we call, in Florida, 'outside of wastewater-reclaimed areas.' In other words, these areas were ones where wastewater was not used for irrigation. We did that because we didn't want that nitrogen and phosphorus component [from wastewater re-usage] added back in, since this would introduce an additional complication.

However, at the end of the study, we decided to satisfy our scientific curiosity by looking at three municipalities that were inside of wastewater-reclaimed areas, even though doing so was outside the scope of the project. From a historical perspective, that's what led to this third study that we completed in 2019, which looked at data both inside and outside of wastewater-reclaimed areas.

One of our goals was to see what we could say, specifically, about differences between those two types of areas. All of the previous (2011 study) municipalities participated in the 2019 study and we also had a number of new municipal participants. The study was funded through the Florida Department of Environmental Protection via the Florida Stormwater Association.

WorldSweeper: That's a great overview of how this entire project was developed. What did you ask each of these municipalities to do, on an overview basis?

Dr. Sansalone: Where we were in terms of the Phase II study, in the portion where we focused specifically outside the wastewater reclaimed areas, we asked 14 municipalities across Florida to collect particulate matter samples from street sweeping, from catch basin cleaning and from best management practice cleaning. We had very specific protocols on how these were sampled; sample holding time for results to be returned to our University of Florida lab; requirements for the amount of mass collected; where the material was collected in these municipalities, etc.

We then did the analysis for particular matter granulometry, basically, particle size distribution; inferences about organic versus inorganic content; water content, which is critical; as well as nitrogen and phosphorus content of the particulate matter collected, whether it be from street sweeping, catch basins or other best management practices.

Just the data collection and laboratory analysis, which was all done outside of reclaimed-wastewater areas, easily took us a couple of years. This gave us metrics, both probabilistic and statistical, that said "When you collect a pound of dried particulate matter – and we had a way to tell what dry meant based on moisture content – depending on land-use and hydrologic functional units (i.e., whether collected from street sweeping, catch basins or best management practices) then we now have a defensible yardstick that tells us how much total nitrogen and total phosphorus is associated with that pound of particulate matter."

One of the results that came out of the Phase II data, though, was that we noticed that for the three places we sampled that were inside of reclaimed-wastewater areas, there was a difference in nitrogen and phosphorus content in the particulate matter, just as one might hypothesize. There should be a difference, especially if there is wastewater overspray on the pavement surface, as there is in every municipality that reuses reclaimed wastewater.

[The unanswered questions in that regard] are what led to Phase III, which resulted in the 2019 study results. Our methodology for this most recent study was that we looked at an equal number of locations inside and outside of wastewater-reclaimed areas. We wanted to see if there is a defensible difference that a municipality can claim for added load credits if they are located inside of a wastewater-reclaimed area.

In addition, we wanted tighter control on moisture content so that municipalities did not have to go out and measure moisture content every time they brought in a load of street sweepings, or cleaned out a catch basin or used another best management practice like a sump.

WorldSweeper: Can you give some examples of what some of those BMP practices you're talking about consist of?

Dr. Sansalone: The initial thought was to include only one BMP; however, municipalities in Florida have chosen a wide range of [end-of-the-pipe] BMPs and I wanted to include data such that it was representative across Florida. The BMPs can be nonproprietary, like grassy swales. They can be wet or dry basins, which are very common in Florida as in other parts of the United States. They can be infiltrating under-drains.

We examined all of those as well as manufactured or proprietary BMPs, a classic one being a hydrodynamic separator of which there are many models on the market. These are pretreatment devices that are able to capture coarse particulate matter but that are quite ineffective at capturing fine particulate matter.

And, a larger problem with many of these BMPs is they contain wet sumps that go aerobic, so you then have to wonder about what the leaching potential is from the particulate matter such that, when the next storm comes in, the chemicals that were bound to the material are transferred out.

That's a real concern because most of these BMPs will become anaerobic in a 48-to-50-hour period. Sumps are a great environment for an anaerobic bacteria build-up: they have moisture, an organic substrate, nutrients, and a lot of surface area to grow on. It's an ideal home for microorganisms. That is a very problematic issue with those BMPs in urban environments.

There are not very many people who will argue with the fact that if you can remove the particulate matter, and the chemicals and pathogens associated with that material, before they become part of the hydrologic cycle – and therefore have to be removed by treatment systems – the better off we are in terms of water chemistry, load reduction and the receiving water and soils' environment.

BMPs do fill up with coarse material and need to be cleaned up very frequently and, yes, [it's a plus] that you can move just the screen and clean out catch basins. From my experience the latter need to be cleaned out on an annual basis. Other BMPs need to be cleaned out even more frequently.

However, ideally, if we are doing street sweeping/pavement cleaning efficiently, effectively and on a routine basis, none of these catch basins or the other BMPs are going to fill up with particulate matter. Their maintenance frequency is going to go down and their performance in the long term is going to be better.

WorldSweeper: It's been a very difficult task in the 30+ years I have been involved with power sweeping to educate public works managers about the importance of getting pavement-based material off the ground first. One of the studies we covered previously indicated that, although only about 10% of the material on an average street is 250-microns or less – a human hair being about 72-microns – for reasons of physics up to 60% of the pollutant load may be contained in that 10% fraction.

Another problem with end-of-the-pipe solutions is that some of the materials we're trying to eliminate are water-soluble. So, it stands to reason that capturing water-soluble material will be more difficult with an end-of-the-pipe solution.

Dr. Sansalone: I have three comments to that: First, water solubility is a function of the chemical. For example nitrogen, in terms of water solubility, is completely different as compared to phosphorus. When we look at metals it very much depends on the specific metal. The problem you have to be careful about is solubility. Re-partitioning to the particulate phase is not a one-way street but, rather, is a two-way street. These different chemicals can partition back and forth as a function of time.

The partitioning issue is quite complex and dependent upon the physical situation of the chemical and the particulate. This is particularly true in the BMPs. Partitioning is a function of particle size.

Allow me to get a little more complex and talk about concentration versus load: If you're speaking about chemical concentration on particulate matter you can show fairly simply that, as you go to smaller and smaller particles, by definition concentration always goes up. By concentration, I mean milligrams of a chemical per kilogram or pound of dried particulate matter. As we move to finer and finer particles, by definition that concentration has to go up.

On the other hand, if my interest is strictly mass, or load, in the highway settings of urban municipal settings, most of the total mass, and most of the total load – whether phosphorus or metals and, to a reasonable extent, nitrogen – are associated with the coarser fraction of particulate matter and not the finer fraction. Basically, I'm integrating across the particle size distribution.

This was a hard sell 15 or 20 years ago and, in fact, some number of people accused me of being a heretic. Eventually, though, as I got peer-reviewed publications out there that demonstrated this for nutrients, as well as my early work on metals, I think that most people now acknowledge that if you're after load then you want the entire particle size distribution. However, it is the coarser fraction that dominates the total load not only in terms of particulate matter but in terms of chemicals associated with that particular matter.

Having said that, I also need to say that, from a bioavailability point of view, I'm really concerned about the finer fractions of particles. Those particles typically left on the ground, typically about 25-microns, are considered to be the 'suspended particles,' (they will remain suspended in an Imhof cone for 60 minutes) and are the most bioavailable.

On the other hand, if I go back and look at the coarse fractions, the sediment and fractions larger than about 75-microns, that is the most labile [easily broken down or displaced] and leachable fraction. It also happens to be the fraction that is the most readily separated by a BMP and the problem is that, in a wet sump, that is the fraction that is most labile and leachable.

From a concentration point of view I worry about the fine particles because they are the most bioavailable and they are the most mobile. That said, I am worried about the coarse fraction because that is where most of the chemical load is associated. The coarse particles also happen to be the particle size range that are more readily removed by a BMP. Unfortunately, though, in a wet sump these are also the most leachable.

WorldSweeper: That's a very complex message...

Dr. Sansalone: Yes, it is. However, over my 25+ years of work to create that message the simplification of it is this: We need to be focused on the entire particle size distribution, not just the coarse fractions, because we are able to remove those with most of the chemical and particulate matter load. We also need to remove the finer fractions, the suspended fractions, because that's the most bioavailable of all of it. Unfortunately, that's the fraction that is not removed by BMPs.

WorldSweeper: What you are saying all points to sweeping, because you are removing the coarse particles as well as, when done correctly, a large amount of the fine particles. You want them all, of course, and the question is how to do that most effectively.

Dr. Sansalone: The reality is [that what you want to do is] remove most of the coarse particulate matter on the roadway, so that it is not ground up by traffic into finer and finer particles.

WorldSweeper: And because the larger material is also not going to be available to run off easily in storm or wind events.

Dr. Sansalone: Absolutely!

WorldSweeper: So, an important factor on the sweeping side is that air sweepers tend to get more of the finer particles. Even though you have water-based dust suppression on mechanical broom sweepers, without the suction component there will typically be more small particles left on the ground. Some studies have even shown that broom sweepers may create and leave, via the brushing action of the main broom, more small particles on the roadway than were there before they swept.

Municipal managers tend to want to use mechanical broom sweepers because they have the ability to pick up mufflers, tire casings and other larger items as they travel along the roadway, something [that won't fit up the @14" intake tube] on an air sweeper. However, the fact of the matter is with a broom-only sweeper you will typically be leaving more small-micron material than would be happening with an air sweeper.

Let's talk about the actual results of your 2019 study. In general terms, what was the information you found when comparing sweeping with catch basins and BMPs?

Dr. Sansalone: The real take-home message from the 2011 study, which was reinforced by the 2019 study – and this holds for wastewater-reclaimed areas as well as for areas where wastewater is not being reclaimed – street sweeping dominated. And, when I say dominated I mean by several orders of magnitude as compared to load recovery from all of the other BMPs which, by the way, I am totally agnostic between.

Nonproprietary BMPs, such as wet and dry basins, have a role from a hydrologic point of view. But the reality is that street sweeping absolutely dominated load recovery, particulate matter and nutrient retrieval. Frankly, I am confident that if we had looked at metals in these studies it would have shown us the same thing, as compared to both nonproprietary or manufactured BMPs.

If you think about it conceptually, that has to be the case. Roadways are long, linear systems. If I design my source control to target that kind of geometry, as is the case with street sweeping, I'm able to recover these particles before they become part of the hydrologic cycle. Both [the 2011 and the 2019] studies demonstrate that, with street sweeping, I have the ability to recover particulate matter and, therefore, particulate load. [This ability is] orders of magnitude greater with street sweeping and, therefore, orders of magnitude more economical than any other BMP, period.

Don't get me wrong: I am a fan of BMPs. My work has been mainly water treatment and computational fluid dynamics for unit operations in water treatment. However, there is nothing that touches pavement cleaning in terms of effectiveness, load recovery and efficiency in terms of cost per pound of particulate matter or chemicals recovered. That's the simplest message that I can deliver.

WorldSweeper: That's a very strong message, and one that I, too, have also been trying to get out for many years based on other, less exhaustive, studies. I'd like to ask for your opinion on something that I recommend. Today, many jurisdictions allow resident fees put onto such items as garbage collection, fees that are earmarked for stormwater pollution management.

My advice to municipal managers is to combine their street sweeping program with their storm water management program, in order to remove budgetary conflicts and 'turf wars.' Then, figure out what your cost is to pick up, via sweeping, a pound of whatever pollutant(s) you are targeting. As your frequency of sweeping goes up, that cost per pound will, of course, also rise since you won't be picking up as many pounds per curb mile and yet you'll still have the same basic cost per mile of running the sweeper.

When you calculate your cost of removing a pound of a given pollutant via sweeping, and you also know your cost per pound for removing stormwater pollutants via other methods, when the expense curves cross – i.e., when the cost of picking up your last pound of pollutant by sweeping, as you have increased the frequency, equals the cost of picking up the first pound of pollutant at the end-of-the-pipe – then it's time to quit sweeping and spend money on catch basins and other BMPs.

Public works, DOT and other infrastructure professionals trying to keep our water sources clean really need to figure out what is their cost per pound of picking up targeted pollutant(s) via sweeping. When you know that information, then increase the frequency of sweeping until the cost per pound increases to where it is more cost-effective to put the money into alternative BMPs. Would you say that makes sense?

Dr. Sansalone: That makes absolute sense. To be able to develop coordination and communication in different departments in the municipality is just a win-win situation for everyone. Part of the emphasis that drove the 2007 study – and based upon the results that came out of it – is that we said to the Florida Department of Environmental Protection "Instead of holding out a 'stick' to municipalities if they do not complete the required load reductions with their BMPs, why not give them a 'carrot'? Tell them that if they can document their load recovery of particulate matter, nitrogen and phosphorus, then give them the carrot, which is to say load credits in their basin management action plan."

That was the driving force for the 2007 study and it proved to be wildly successful, really beyond anyone's prior imagination. By the time we finished the last of the studies in this trilogy, large municipalities in Florida were saving tens of millions of dollars in their basin management action plans because they had metrics from the studies, in both the 2011 and 2019 studies, that documented their load recovery.

Sweeping, instead of being something that was cut, now becomes the preferred tool for load recovery and, by the way, it's much, much more effective and efficient. Speaking to the economics of the situation, which is as much of a driver as the environment and human health, let's just look at the total cost of phosphorus removal in terms of dollars per pound removed. From a BMP treatment typical to Florida, removing a pound of phosphorus costs about $32,000.

[As was shown in the chart at the top of this article] The Florida database of BMPs was at $10,000. Hydrodynamic separators varied anywhere from $3000-$36,000. With street sweeping, we're not even in the thousands! For total phosphorus, [removal by street sweeping] was $257 per pound.

Here's another example: For [removal of a pound of] total nitrogen it cost $165 per pound when removed via sweeping. That same cost per pound for other BMPs ran from close to $1000 up to $14,000.

With conventional BMPs, particulate matter removal cost dollars per pound, anywhere from $4 to $41. For street sweeping the cost for removing a pound of particulate matter was 10 cents! That's really the only thing people need to know.

So knowing, [educated stormwater professionals] will put their money into pavement cleaning as their first line of defense. Then, if that's not sufficient for their receiving water or receiving soil conditions, they will add in an engineered strategy to pick up the fine particulate matter, or whatever else needs to be picked up, for additional load reduction or concentration improvement. It's that simple.

WorldSweeper: Those are very strong results and conclusions that came out of your study. There's something else I believe is often lost in a comparison between sweeping and other BMPs – whether catch basins or grassy swales or whatever – and how they remove pollutants: In addition to all of the pollutant removal done via street sweeping, most all of the larger materials on the roadway are also removed, and that's the stuff that causes slip and falls, roadway accidents and that are available to become smaller, more polluted, particles as they get run over by vehicles over time.

When that occurs, those smaller particles are much more available to be blown into the air or transported into waterways since their size has been decreased. This fact needs to be factored in along with the cost of removing whatever kinds of pollutants you are targeting to get out of the stormwater pollutant runoff.

Triathalon John Sansalone Dr. Sansalone: I agree. As an aside, I am a triathlete, and the matter of particulate matter on roadways is problematic not only from a shoe puncture problem but also as a matter of stability. I don't want to go down when I'm running at high-speed because of that fine, granular material being on the pavement. Cleaning the pavement is absolutely critical.

WorldSweeper: One thing that I noted was not differentiated in your study was which of the loads brought in by the municipalities were picked up by mechanical broom sweepers and which were from air-based sweepers. Is that anything that could be teased out after the fact?

Dr. Sansalone: I believe those data could be teased out. I have a huge database from each municipality and I think [the broom sweeper data vs. air sweeper data] is a factor that should be found out. Once we get the 2019 study's primary results published, perhaps we will have the time to work on the differentiation effort you suggest.

Air-based sweepers have a different functionality than broom-based sweepers. Although really important, that comparison was just not within the scope of our study. In the future, that may be another aspect in the study that we can find out. I think we could design a set of experiments where we could really answer that question.

WorldSweeper: Although it's been back over a decade now, I recall publishing a study that showed the effectiveness of tandem sweeping. To the astonishment of most all observers, even within the knowledge base of the industry, after the mechanical broom sweeper went by and the roadway looked essentially clean, the air sweeper following behind picked up enough that the cost analysis showed that for residential streets, the higher cost of tandem sweeping was more than countered by its greater removal benefit. Not surprisingly, the material picked up by the air sweeper all tended to be small-micron particulates, as compared to what was picked up by the broom sweeper.

Dr. Sansalone: The analog I would offer to that is from wastewater treatment: You always follow primary treatment at a wastewater plant, i.e., the broom sweeper, with secondary treatment, i.e., the air sweeper. Both are effective, but for a different particle size distribution.

WorldSweeper: What else do you think we should bring up as part of our discussion, now that we are closing out our podcast hour? How would you sum up all of this?

Dr. Sansalone: I would say that from the Phase II study, which was completed in 2011, as well as the Phase III study completed in 2019, the clear dominant message that comes out is this: Yes, there is a lot of complexity and detail in this work. However, there is a clear primary message that comes out, which is that street sweeping in the urban environment can dominate both load and particulate recovery, as well as removal of 'you name the chemical of your choice.' That is true both from effectiveness – a load recovery point of view – as well as from an cost-effectiveness point of view.

Both are by orders of magnitude when pavement cleaning, i.e., street sweeping, is compared to the other best management practices although I am not arguing against best management practices. That said, based on load recovery it's important to do those techniques that recover the most load, both on the coarse particle fraction distribution and, as much as you can, on the finer particle size distribution.

Street sweeping is the most effective and most economically efficient. If sweeping does not solve the load reduction and concentration reductions that you need then, and only then, you need to add engineered treatment systems. But [our data clearly says to] go after that low hanging fruit first, before implementing the more expensive treatment.

Economically, it's great for the municipalities, is a benefit to the urban environment and, quite honestly, if we think about human health – and this is about human health for those of us who live in urban environments, walk in urban environments and bike in urban environments – these results show us how to improve our health.

If I remove that fine particulate matter then it is material that doesn't end up in my lungs and therefore in my bloodstream, and it is not a source of potential damage to my cardiovascular system. It does not end up on my skin and it does not end up in my eyes. If I remove the material via street sweeping as close to the source as possible and as frequently as possible – here in Florida the sweepers are out every single week in many of the lake regions to make sure those lakes stay clean and pristine – it improves all of the ecology, including human ecology.

WorldSweeper: I couldn't agree more. Before we finish, would you please explain the credit system that Florida has enacted to replace the 'stick concept' with one of 'carrots?'

Dr. Sansalone: Florida municipalities literally get load credits for every pound of nitrogen and phosphorus that they are able to document as having been removed by their maintenance programs. [As a result of the studies] these programs are now dominated by street sweeping. They get to offset those loads that they recover via street sweeping against loads that they would otherwise have to deal with, or prove that they will deal with, through the use of other much more expensive BMPs.

WorldSweeper: And, your experience in Italy as well as your knowledge of other parts of Europe is that they move the cars and that provides a large increase in pickup efficiency?

Dr. Sansalone: Yes, they move the cars. People have been trained to understand why and to give that entire concept value. As anyone realizes who has been to Italy and has been in urban areas, large or small, given the proximity of buildings next to the street and the narrowness of the pavement the pavement serves as a collector of particulate matter.

Street sweeping is seen as a very critical process for those urban environments and for human health because people are out walking and biking much more in Italy than they are in the U.S.A. And, because [most Italian and European cities] have combined sewers, they really need to keep that particulate matter out of their systems so it cannot create a problem either in their conveyance system or in their treatment plants.

WorldSweeper: I believe a very large component of this process is the education. People need to be taught why street sweeping, along with the importance of moving cars when they do so, is so critically important and the substantial difference it will make.

Although you will always have pushback on required vehicle moving by some of your populace, it's something that is very important to get done. Further, once vehicle removal programs are in place then it's also very important to bring the fact of the improved results out to people through your municipal education networks.

Dr. Sansalone: I have to thank the State of Florida for having the vision, through Florida's Department of Environmental Protection and the Florida Stormwater Association, that it's far better to provide a carrot, in terms of load credits, as opposed to enforcing a stick aimed at the municipalities. It has been a very positive experience for the Florida municipalities and they now value their street sweeping maintenance programs much differently.

WorldSweeper: What we are doing with this article is educating the public works and stormwater professionals in America and around the world to the enormous value of not only doing more sweeping, but also in doing it correctly.

Let me provide them with this thought: Use the astounding conclusions of these three studies to go out there and get this type of 'carrot instead of stick' credits enacted in your state. This is important even in those states that don't currently have a stick; there is no doubt those requirements will be coming. For years, people have said that water will someday "become the new oil." That day is today.

Dr. Sansalone: Yes, go out there and get those credits. Clean water is absolutely critical and a clean, healthy environment behooves not only clean water but it is vital to human health!

Dr. John Sansalone is the Eckler Professor of Excellence in Engineering at the University of Florida. In addition, in his 25+ year career he has been a visiting professor at a number of other institutions both in the United States and in Italy. He has spearheaded three studies in the Florida municipal arena, all of which have shown that street sweeping is, by far, a municipality's first line of defense in water quality maintenance and improvement. You may reach Dr. Sansalone via email sent to To reach the Florida Stormwater Association call 888-221-3124.

The author, Ranger Kidwell-Ross, is a Masters-level economist who has covered the worldwide power sweeping industry for over three decades. Over that time he has traveled to 15 countries to document the worldwide power sweeping industry and, in the process, has won over twenty U.S. national writing awards for his coverage of the industry. Ranger is the Editor of and the Executive Director of the World Sweeping Association.

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