As California and several other states have recently found out, water conservation is a huge deal to resident’s quality of life and the environment’s overall health. Allowing water to drain naturally is a huge part of keeping our aquifers filled with water, but our roadways and parking surfaces are mostly impermeable surfaces, causing us to redirect rainfall unnaturally into drains and sewers. Sudden and large amounts of rainfall in a short period of time can lead to extremely hazardous conditions, like flooding.
The difference between rainfall ground infiltration in natural and impervious surfaces. Graphic by the US Environmental Protection Agency.
This graphic from the EPA shows the major difference between the amount of water infiltration in a natural area (50%) to an impervious one, like many of our cities have (15%). In urban areas, roughly 55% of rain water has to be taken care of by drains and sewers and this runoff is one of the leading causes of floods.
A new type of concrete paving, Topmix Permeable, has been created by English company, Tarmac, that can swallow hundreds of gallons of water every minute and allowing it to drain into the ground below. Unlike traditional paved surfaces, Topmix Permeable has a void content of 25-30%, which allows water to drain at a rate of roughly 40 to 250 gallons per 10 square feet. The water is then filtered through a layer of pervious aggregate sub-base and then through undisturbed permeable soil.
Because of the high void content, this system will not be as strong as traditional paving systems, so it’s only recommended in low volume and low weighted areas, such as lightly traveled residential roads, sidewalks and pathways, driveways, alleyways, sports courts, and other similar applications. There have also been some concerns regarding Topmix’s ability to withstand freezing temperature, but the company claims that the voids allow expansion of water to ice without damaging the surface. Most of the water passes through the top surface, as well. The company also claims that the material, due to being much less dense than concrete and asphalt, does not contribute as much to heat island effect in urban areas. On their website, Tarmac also explains that Topmix is designed to function effectively even when blocked by dirt or other debris up to 95%.
It’s a pretty incredible system and really fun to watch. After watching the video below, let us know what you think!
Topmix Permeable | Tarmac
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