...It's Moot Without Data We still don't know how to sweep effectively for 'fines.'
We invited the San Francisco Bay Regional Water Quality Control Board, the state's water pollution control authority for the bay area, to provide comments on the opt-out program. Tom Mumley, their Urban Runoff Control Manager, wrote the following article on that topic, and included as well that organization's current view on street sweeping as a best management practice of the Clean Water Act.
From our perspective, the jury is still out as to whether street sweeping is truly a stormwater best management practice. Most street sweeping is currently done for its aesthetic value and litter control, and is not operated in such a way as to get the 'fines,' the small particles where we expect the toxic pollutants to be.
We would like to consider street sweeping to be an effective stormwater pollutant control measure. However, there are still many questions about current sweeping practices and improved practices that must be answered before this determination can be made. My observations are that most street sweepers are operated at a speed way too high to be functional relative to small particles and toxic pollutants.
As I recall, the studies done during the Nationwide Urban Runoff Program concluded that to be effective, street sweepers, whether broom or vacuum, would have to be operated at about 4 or 5 mph. I've never seen a sweeper go that slow in my life. The question is not necessarily whether the opt-out program, in and of itself, is bad. It's more a matter of getting to the heart of what we can do for better management of runoff, through improved performance of street sweeping. Until we truly answer that question, we can't really answer the question of opt-out.
For all we know, the opt-out program could actually be more effective, if people actually followed through by getting out there and sweeping the streets by hand. By doing so they might, indeed, get the smaller particles.
There are indications that a significant source of copper may be coming from brake pad wear. If that is the case, then it's accumulating in the dust on the roadways, and it probably tends to be in fine particles. So, clearly, the question that is out there is "Is street sweeping an effective means of dealing with copper associated with automobile brake pad wear?" That question is certainly being asked by us, because of our concern about copper levels in the bay, but we don't have hard data on what street sweepers can really do about this.
We simply need more data, and to me it's amazing how little information is out there for an industry that's so big. We're talking about machines that cost $100,000 and up, being used by cities throughout the country. All of the large cities are now expected to do stormwater management. There is really a role for the industry to play in getting this information out, developing the studies that are needed, etc. What we're running into is a reluctance to change. We're dealing with city maintenance folks who are used to one type of sweeper, sweeping in a particular manner, whether requiring parked cars to be moved or not, and they don't like to change.
A valid argument might be that vacuum sweepers can pick up more 'fines' than mechanical broom sweepers, but the response will be, "Who says they're better, that's hearsay." It may seem logical, but there isn't sufficient empirical data to truly justify any type of change. We simply need better data and, until then, the issue of opt-out relative to stormwater quality will remain pretty much a moot point.
Our regulatory approach to stormwater management in California, at least in the early days, is to not mandate any particular measure until it has been demonstrated that the measure is indeed effective. Also, even if a particular control measure, or Best Management Practice (BMP), is effective, we would always allow for an equivalent alternative. So, we would say,
"Okay, if you can remove a certain amount of pollutants from the streets with effective street sweeping, then that is the performance standard to be met." At that point, an opt-out program could be offered which would require that anyone doing their own sweeping would have to meet that standard. Without a performance standard in place, however, the whole issue can be argued to death.
Street sweeping, in and of itself, is not a solution unless it is done right; in such a way as to make the impact that needs to be made. In this, parked cars become a big issue, because if you can't get to the curb you've lost the opportunity to get to where the pollutants accumulate. Along with that, we are concerned about the issues related to proper waste management. We need to figure out how to classify the waste that is picked up, then take care of it correctly.
There is a video (Portal to the Bay) that L.A. Wood took of activities at a municipal corporation yard showing that the municipal sweepers being operated by a city were being washed out directly over a storm drain inlet. This is clearly not appropriate, but what, on the other hand, is? There are so many questions about how to handle municipal waste: should it be classified as something out of the ordinary, if so, what type of waste; can we manage it in such a way as to distinguish some types of it from others; what can be gained by screening in terms of discriminating between qualities of wastes? Perhaps regionalization of waste collection would allow the truly nasty waste to be dealt with, and at the same time legitimize what may be many uses for the relatively good stuff.
These are complex issues that need some serious untangling. We all need to work together to find solutions to these difficult problems. This article is reprinted from American Sweeper magazine, v3n3.