Summary Reader's Response: Porous Road Surfaces (Summary/Reader's Response Draft 1)

The article “Porous Asphalt Is King of the Road” (PaveGreen, n.d.) presents the benefits of porous asphalt surfaces and explains its utility in improving stormwater management and road safety. Rainfall naturally sinks into the soil and is filtered through it. However, in cities, rainfall or “runoff” causes flooding on roads and parking lots, along with contaminants, such as oils and minerals. It then flows straight into drains without being filtered naturally.

The article states that porous asphalt is a natural material consisting of rocks combined with asphalt cement, except that there are fewer fine aggregates to provide space for water to pass through open spaces between large aggregates, as compared to conventional roads. Underneath, a “recharge bed” composed of spaced-out stones with 40% voids retains rainwater until it is filtered into the soil, hence cleaning it. Porous asphalt is extremely beneficial as it reduces stormwater drainage costs and increases road safety while decreasing the environmental pollution.

As porous asphalt redirects runoff into the soil instead of stormwater drains, this reduces the need for storm sewers. The need for retention ponds is also reduced or even eliminated (Lombardo, 2020). Since there is less space used by such stormwater management solutions, the area can be used as “a profitable asset that adds value to the property” (Mrugacz, 2017). Even though the stone bed underneath costs more than a conventional road, it is typically outweighed due to substantial savings in reducing stormwater pipes and inlets needed, as well as additional money-making assets on the property. More savings can be expected as the article points out that there is less unearthing as it conforms to the topography of the land. Furthermore, porous asphalt can be “poured and rolled in less time than what is needed” (Boysen, Carlson, Harris & Zanoni, 2018) for traditional concrete roads, thus reducing construction time which leads to fewer labor costs (Boysen, Carlson, Harris & Zanoni, 2018).

The article mentions that during storms, porous asphalt greatly reduces accidents as fewer road splashes lead to higher visibility. As there is less surface runoff, roads are less likely to be flooded. This also prevents limited access to essential services such as hospitals, fire stations, and police stations (Boysen, Carlson, Harris & Zanoni, 2018). The article also mentions that for areas with heavy snowfall, it reduces the need for “deicing” to make roads less slippery. The voids in porous asphalt contain air that traps heat which helps in the melting and thawing of ice and snow on the surface (Boysen, Carlson, Harris & Zanoni, 2018). Hence, road safety is improved in both rainstorms and winter climates.

As toxins from runoff are treated by the multiple layers in porous asphalt, they will not end up in public waterways which will harm human and aquatic life. During deicing, salt is applied on roads which decreases the melting point of ice, hence preventing ice from forming on road surfaces (Pollock, 2019). However, when it dissolves into the soil or flows into the runoff, the “chlorine-laden treatment” (PaveGreen, n.d.) ends up in bodies of water which can destroy aquatic life and reduce drinking water quality (Boysen, Carlson, Harris & Zanoni, 2018). Therefore, with the natural heat insulation warming the surface, the need for deicing is mitigated and promotes environmental protection.

However, porous pavement is not perfect. It can get clogged due to sediments and debris getting caught in pore spaces (Boysen, Carlson, Harris & Zanoni, 2018). This reduces or even eliminates the utility of porous asphalt. Constant and regular maintenance is required to establish its effectiveness. The soil underneath also needs to be highly permeable (Lombardo, 2020). If it is saturated, the microbiological decomposition of pollutants may be hindered (Lombardo, 2020) and the effectiveness of porous asphalt might be reduced to the point that additional drainage needs to be installed (HomeLogic, 2019). The lifetime expectancy of porous asphalt is only 20 years (Mrugacz, 2017), while standard concrete roads last up to 25 years (Ayres, 2022). 

The article shows that porous asphalt is known by the Environmental Protection Agency as “a best practice for stormwater management” (PaveGreen, n.d.). Despite the several disadvantages of porous asphalt, it is still widely and successfully implemented everywhere due to its outstanding benefits, which cut stormwater management costs, improve road safety, and promotes environmental conservation.

References: 

PaveGreen (n.d.). Porous Asphalt Is King of the Road.

http://www.pavegreen.org/index.php?option=com_content&view=article&id=58%3Aking-of-the-road&catid=35%3Aporous-asphalt&Itemid=110

Lombardo, J. (2020, May 21). How It Works: Porous Asphalt Pavements. For Construction Pros.

https://www.forconstructionpros.com/asphalt/article/21134321/how-it-works-porous-asphalt-pavements

Mrugacz, J. (2017, May 2). Porous Asphalt Paving - Cost And Environmental Benefits. Wolf Paving.

https://www.wolfpaving.com/blog/bid/55431/porous-asphalt-paving-cost-and-environmental-benefits

Boysen, A., Carlson, M., Harris, J. & Zanoni, L. (2018, November 28). The Benefits of Using Porous Asphalt Pavement in Comparison with Other Forms of Pervious Pavements. University of Illinois, Chicago.

https://www.il-asphalt.org/files/3715/4896/1291/Luke_Zanoni_2018_UIUCgo.pdf

Pollock, J. (2019, February 12). Salt Doesn’t Melt Ice—Here’s How It Makes Winter Streets Safer. Scientific American.

https://www.scientificamerican.com/article/salt-doesnt-melt-ice-heres-how-it-makes-winter-streets-safer/

HomeLogic (2019, September 18). Porous Pavement Pros And Cons: The Ultimate Guide. 

https://www.homelogic.co.uk/porous-pavement-pros-and-cons#:~:text=Porous%20Pavement%3A%20The%20Cons&text=More%20expensive%20%E2%80%93%20in%20many%20cases,large%20part%20of%20the%20expense

Ayres (2022, February 2022). The Long and Short of It: Lifespans of Paved Roadways. 

https://www.ayresassociates.com/the-long-and-short-of-it-lifespans-of-paved-roadways/#:~:text=According%20to%20the%20WisDOT%20Facilities,asphalt.