Water scarcity and water pollution are expected to be two of the biggest environmental problems of the coming century. One way to reduce water pollution and replenish groundwater supplies is with porous pavements.

Runoff from impermeable sources is one of the leading causes of water pollution in the world, responsible for an estimated 70% of surface and groundwater pollution. Porous pavements, on the other hand, mimic the effects of plant cover or mulches by allowing water to soak through to the soil below instead of running off into sewer systems or nearby waterways. This replenishes groundwater supplies and improves the health of nearby plants.

Porous pavements also provide better traction during snowy or icy weather, because melting snow and ice sink into the ground, rather than melting and refreezing, and reduce the urban heat island effect compared to traditional pavements, thanks to their higher albedo level.

Porous pavement should not be used in areas with low soil permeability or areas at high risk of toxic spills, but they make great choices for moderate to low traffic areas such as driveways, patios, sidewalks, alleyways, and many parking lots.

Types of Porous Pavement

There are several different types of porous pavement that are suitable for residential and commercial areas.

• Porous asphalt allows water to pass freely through small holes and passages in the asphalt. These are created by reducing the amount of tar and small particles from asphalt mix. It looks almost identical to traditional asphalt and uses the same equipment to mix and install. Porous asphalt is one of the most durable porous pavement options, and is suitable for commercial parking lots and other areas of moderate to heavy traffic. However, it requires a bit more maintenance than other porous pavement options because the pores must be kept free of dirt and debris or they can become clogged.
• Porous concrete also uses the same equipment as traditional concrete, but looks noticeably rougher and more pebbly. Like porous asphalt, porous concrete is relatively durable and can be used in moderate to heavy traffic areas, but it also needs to be kept relatively free of debris that can clog the pores.
• Bricks, concrete blocks, or other interlocking pavers set into a layer of sand or small aggregate are an attractive semi-permeable option for low or moderate traffic areas. Because of their attractiveness and the wide variety of choices available, they are especially well suited to residential areas and commercial areas of high visibility.
• Plastic grid systems are sometimes called geocells or reinforced turf. They consist of plastic grids filled with gravel or soil, sometimes with grass or other plants seeded in, and are especially useful for preventing erosion. They are best suited for low traffic areas.
• Rubber pavers are made from recycled tires and are growing in popularity as a porous sidewalk option because in addition to being porous, they also cause less stress on joggers’ joints and are less dangerous for small children and the elderly in case of falls.
• Gravel, mulch, and similar materials can be used as an easy and inexpensive substitute for more durable alternative pavements in areas where they are allowed by building codes. However, these materials generally suffer from compaction that reduces the permeability over time, and they may have problems with mud or dust.

Choosing porous pavement for your home or business is a great way to reduce your environmental impact and help preserve plentiful, clean water sources for future generations.

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Image credits: EPA Smart Growth and Center for Neighborhood Technology