I posted a quick note earlier about installing porous asphalt in a green community in Oregon. In that note, I made an offhand comment questioning the water quality coming off the road. After posting the article, I also wondered if the lifetime of the surface would be shorter in areas prone to freezing weather due to the expansion and contraction of ice in the pores.
It turns out that had I been less lazy in doing my research, I’dve had all these questions answered much more quickly. I just found a great article on porous asphalt that covers a lot of topics, including water quality (82% removal efficiency for organic carbon) and lifetime in freezing weather (longer than standard asphalt).
Additionally, the article points out that the porosity allows for less use of salts for deicing and that:
The water drains through the pavement and into the bed below with sufficient void space to prevent any heaving or damage, and the formation of “black ice” is rarely observed. The porous surfaces tend to provide better traction for both pedestrians and vehicles than does conventional pavement. Not a single system has suffered freezing problems.
Pretty darned cool, if you ask me. One has to ask what the factors are that are keeping this from being installed in every new parking lot being built. Undoubtedly, the subsurface strata affect the design – this is also covered in the article – but I suspect strong that the major factor is simply ignorance.
On a lighter note, the best quote from the article is this one: “Fortunately, even without regular maintenance, the systems continue to function (we routinely send graduate students and recent hires out in hurricanes to confirm this).”