The majority of urban surface area in the U.S. consists of concrete, asphalt, and other pavements that are impermeable to water. There are unintended consequences for the millions of miles of collective streets, sidewalks, parking lots, and rooftops that cover our cities.
It’s estimated that over 10 TRILLION GALLONS of untreated stormwater, wastewater, and sewage gets discharged into clean water bodies every year. Traditional concrete and asphalt surfaces have a major role to play in this.
When it rains, stormwater that should naturally soak into soils and recharge groundwater instead becomes polluted runoff as soon as it hits the pavement. In some regions that are experiencing larger and more sudden flashes of rain, the issue has evolved from one of stormwater pollution into one of urban flooding.
Interlocking “gap” concrete pavers are prone to collecting debris within the gaps.
On the other end of the spectrum - in drought-ridden regions - when it actually does rain, every drop of rain that turns into runoff is wasted. Permeable pavement’s role in solving these issues is now undeniable.
So what exactly is Permeable Pavement?
In the most basic sense, permeable pavement is a type of paved surface that is designed to allow rainwater to pass through it and back into the ground naturally. It seems like a no-brainer, but as great as the concept might be, the market for permeable pavement remains nascent due to a technology lag. Solutions such as porous asphalt, pervious concrete, and interlocking “gapped” pavers have been around for decades with very little innovation.
More specifically, the lack of durability and a propensity to quickly clog up from debris has limited the real world potential for these products. Expensive maintenance and replacement costs haven’t helped, and the irony of portland cement-based permeable pavements should not be lost on us. The cement industry is responsible for 8% of global CO2 emissions. Elevated greenhouse gasses are amplifying climate change which is delivering more extreme weather. In other words, the very technologies meant to help cities adapt to climate change are in part contributing to it.
This pervious concrete installation became impervious from clogging and moss growth.
Leaping Technology Forward
Despite all of this, permeable pavement should still be a key component of stormwater infrastructure moving forward, just not as it has existed in the past. Fortunately, new technologies are being developed that are resistant to clogging, as durable as normal concrete, and made with new types of “cement” that are environmentally friendly. At AquiPor, we’ve been fortunate to have a front row seat as the technology has evolved.
In conjunction with reliable engineering, good hydrologic analysis, and an accounting of the capacity of the underlying soils to accept stormwater at a given rate, this type of material can be implemented into a permeable system design for full infiltration, partial infiltration, or even full attenuation where stormwater reuse is desired.
Hard surfaces are very useful in our cities. Unfortunately, as they exist today they also contributed significantly to urban water issues. But with the right permeable technology and good engineering, they can be transformed to help improve the sustainability and quality of our natural water systems.