Tarmac, a British company, shows just how much water their permeable concrete can absorb. Using mixer truck, 4,000 liters of water are sucked through the concrete and into the ground in 60 seconds. One of the biggest challenges to urban environments is drainage and water quality. Could this be an innovative solution for the future?

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Stephen is an urban planner with a passion for sustainable, livable, and diverse cities. He is especially interested in how policies, regulations, and programs can promote positive outcomes for communities. Stephen lives in Kenmore and primarily covers land use and transportation issues for The Urbanist.

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That could be a game changer for sidewalks. Right now, a big part of the expense of adding sidewalks is water drainage. Studies have to be done to prevent the water from funneling into areas that would cause a lot of damage. Gravel would be a reasonable solution, but that is practically useless for those in wheelchairs or those pushing a stroller. This has the potential of saving a huge amount of money.

But then again, if this is really expensive …


Good points, Ross. My reaction was similar; great stuff but it’s no better than the absorption ability of the ground underneath. Lots of gravel and sand under this concrete, then no problem. A layer of hard clay under the base and there will likely be ponds growing on top during a heavy rain.

Porous concrete is not exactly new. What’s new here appears to be the quicker rate of absorption.

Stephen Fesler

See above.

Stephen Fesler

Actually, gravel isn’t always a reasonable solution. Most gravel surfaces are considered impervious surfaces under drainage manuals and for good reason: they compact so tightly to effectively result in low water seepage and instead sheet flow. Worse, they spread sediment far and wide. For streams and fishies, that’s a bad outcome. Gravel should really be a last choice for any urban environment where other options are available like bioswales and pervious concrete.

I’m not sure about how expensive this is. I’ll make a note to ask around for cost estimates from colleagues. My gut is that it’s still pricier than standard concrete to install, but there could be some cost savings as well by removing the need for some drainage infrastructure. More than that, there is the long-term maintenance from understanding. I hear that you have to routinely clean the pours.

Roger notes a fair point as well. The soil makeup below also plays a role on how effective pervious concrete operates. On top of that, there are concerns about roughness. Is it comfortable to people in wheelchairs and bikes? I’m not sure. Still, it’s a cool technology with massively positive aspects to it.