Known for its pristine waterways and sunshine, the City of Pensacola's sweeping program is working hard to combine effectiveness and the realities of the Florida climate, propensity of sand and difficulty of vegetation removal.
Al Garza, who will this year celebrate his 10-year anniversary as Director of Public Works for the City of Pensacola, offers a thoughtful perspective on how his organization is evaluating the role of street sweeping in its pollution removal program. As increasing pressure is brought to bear in terms of mandated pollution removal, Garza is faced with difficult decisions on how best to operate his entire department.
by Ranger Kidwell-Ross
As you will hear in our accompanying audio interview, Garza is very active in his evaluation of exactly how street sweeping should best be positioned and utilized in order to maximize both his city's visual cleanliness and pollution removal. He fully recognizes that sweeping provides a quantifiable value in pollutant removal, as well as an additional–often unconsidered value–in removal of 'gross particles.' The latter, although they may not have a significant pollution concentration, do create an enormous volume of material that can clog the runoff system.
As is beginning to occur in many areas, Pensacola government has set a quantifiable goal of reducing storm water pollution loading. In this case, the target is a 50% pollution reduction in storm water, a formidable task in an area that's 95% developed and that prior to 1982 didn't even have a storm water treatment facility. As a result, much retro-fitting has to be done.
To be in a better position to find the correct mix of sweeping and 'end-of-the-pipe' solutions, City of Pensacola government officials have combined the storm water and sweeping departments. Over the long term, this makes it easier to evaluate relative costs and benefits between sweeping frequency and things like catch basin cleaning.
"One of the things we have discovered is that street sweeping is one of our most effective pollution reduction efforts," said Garza. "The City has been street sweeping for over 30 years, but we've never tried to categorize the impact of that effort as it relates to storm water pollution reduction.
"And, with the advent of TMDLs and nutrient restrictions on receiving waters, this has become more of an issue with political jurisdictions. (The questions becomes) 'How do you reduce the impact of your storm water in the most cost-effective manner?' (After investigation we discovered) our street sweeping efforts were equal to our storm water ponds and treatment efforts."
For many years, the City of Pensacola has used Elgin Pelican sweepers for its street sweeping. In recent times, they have been transitioning to Elgin Eagles due to the latter machines faster transport speeds. For reasons that become clear in our audio interview with Garza–and which reflect the dilemma voiced by many public works officials around the U.S.–broom sweepers are felt to provide a better year-round solution.
"We have about 42% vegetative cover over and around our city streets," said Garza. "That puts a lot of leaves and similar material onto the roadway that we need to pick up. We feel broom sweepers do a better job for us, especially here in Florida where we have a preponderance of sand and not so much smaller, fine material to deal with. Because of the rain–we get about 64" per year –the small material gets washed into the storm sewer system and gets treated at that level, anyway."
The City is evaluating what regenerative air sweepers can do, but have found so far that the high sand content in the Pensacola area is highly abrasive. "We have been working with TYMCO to take a look at what their air sweepers can do," continued Garza. "Because our sand is so abrasive, and we have so much of it, we're having difficulty keeping the regenerative air sweepers from sandblasting in particular spots. Plus, we typically have quite a bit of material on our roadways that cannot be picked up by an air sweeper. That creates another set of problems."
The latter is a sentiment echoed by many in public works. Although air sweepers do a better job in removal of the smaller micron materials being increasingly targeted by the EPA and various state agencies, the reality is that they cannot handle the larger debris commonly found on highways and some City of Pensacola streets. That fact mandates advance vehicles for hand pickup, which increases the cost and has safety implications.
By having a combined budget, it will be easier to ultimately have an overall program that utilizes sweeping until the cost of the last pound of pollutant picked up becomes equal to the cost of the first pound removed from the initially more costly end-of-the-pipe solutions.
Garza also discusses the City of Pensacola's movement toward using a trommel screen as a way to both reduce disposal costs to the City and to help them have a better environmental solution for disposal. Florida state law requires sweepings to be disposed of in a Class 3, lined landfill, so disposal costs are more significant than in other parts of the U.S. The trommel screen has reduced landfill cost and volume by about 90%.
Whether you are one of the managers of a municipal street sweeping program or a contractor involved in sweeping streets, you will benefit from the thoughtful analysis Garza provides about the thought processes that need to be involved in today's decisionmaking regarding sweeper types and sweeper frequency. Particularly prominent is that his evaluation is being done for the conditions of his area, something that is perhaps the biggest 'takeaway' for listeners.
In Garza, the City of Pensacola appears to have a public works director who is leading an investigation into what best practices are currently available while evaluating new, emergent technology. At the same time, he is firmly rooted in finding the best solution for the City of Pensacola today.
Note: The following audio interview with Al Garza will play without downloading any files onto your computer. If you hear the interview at 'chipmunk speed,' you will need to download the latest version of Adobe's free Flash player.
If you'd like to contact Al Garza, send an email to firstname.lastname@example.org.
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