In contrast, normal pavement is an impervious surface that sheds rainfall and associated surface pollutants forcing the water to run off paved surfaces directly into nearby storm drains and then into streams and lakes.
These contaminants can kill not only vegetation throughout the city, but wildlife that drinks from the streams and rivers which is fed by this drainage fallout. Many wildlife species are in danger of becoming extinct due to their short life cycle.
Pervious/Permeable Pavers: This material can be used to create a porous surface with the aesthetic appeal of brick, stone, or other interlocking paving materials. They are most often used for driveways, entryways, walkways, or terraces to achieve a more traditional, formal appearance.
Permeable pavers are an environmentally friendly and attractive alternative to traditional paving methods. Unlike standard concrete, asphalt or even paver installations, permeable paver installations provide for drainage and filtration of water into underlying soils or water storage system. Permeable pavers allow water to percolate through joints or holes in the paver itself but also provide a solid surface that can withstand weight loads that are comparable to those of standard concrete or asphalt surfaces.
Permeable pavers come in many designs, and may be made from concrete, plastic or even combinations with recycled rubber. These pavers can be used for in many commercial and any residential paving application including patios, walkways, driveways, and parking lots.
Bituminous permeable paving is appropriate for pedestrian-only areas and for very low-volume, low-speed areas such as overflow parking areas, residential driveways, alleys, and parking stalls. Permeable paving is an excellent technique for dense urban areas because it does not require any additional land. With proper design, cold climates are not a major limitation.
Porous Concrete: Again, the same equipment may be used as for standard concrete. Larger pea gravel and a lower water-to-cement ratio is used to achieve a pebbled, open surface that is roller compacted. This material was recently used in a parking area in Fair oaks, California as a way to reduce solar heat-gain solar from absorption. Project costs were reduced because no retention pond or connection to the municipal storm drain system was required.
The grids provide a support structure for heavy vehicles, and prevent erosion. After heavy rains, the grids act as mini holding-ponds, and allow water to gradually absorb into the soil below.
Loose aggregate such as uniformly sized crushed stone can provide porous paving, although it is only suitable in light-traffic applications where it won’t quickly be displaced, ground down, or mixed with organic matter. Soft materials such as chipped bark or crushed seashells may be used as porous paving in pathways. Conventional dirt roads use mixed aggregate, including fines, and are largely impermeable.
Information found at the NAHB Research Center