Porous pavement at parking lot at Mercer Museum, Doylestown, PA (click to expand)

Here’s something interesting spotted on a recent visit to Doylestown, PA: it’s a parking lot with porous pavement. As seen in the photo above, the area where cars are parked is made up of a type of asphalt that allows water to flow through.

The porous asphalt looks pretty similar to the regular stuff, but appears to have coarser grains when viewed up close:

Left, regular asphalt. Right, Porous asphalt. (click to expand)

The  benefit of using porous asphalt is that water does not flow off the surface into storm drains. New Jersey has a big problem with dealing with floodwater, which tends to surge into local waterways after a storm, carrying with it all kinds of garbage and pollution, and increasing the risk of flooding. Porous asphalt surfaces reduce run-off. The porous surface layer allows water to trickle into a bed of small stones underneath. The water then drains slowly into the surrounding soil, and is therefore naturally retained at the site. Porous pavement is not currently used in Princeton, but it could be applied to reduce the environmental impact of our many parking lots and paved areas.

Sign explaining water management techniques at Mercer Museum in Doylestown, PA. (click to expand)

This porous parking lot is located at the Mercer Museum. If you’ve ever wondered what a seven-story castle made out of poured concrete would look like, it’s well worth checking out.