Green Terms Defined: Pervious Concrete
Pervious concrete is rare in our area, but is growing in popularity. It is simply concrete that allows water to move through the material into a storage area under the pavement. The storage area is typically a gravel bed. By capturing stormwater (rain) and allowing it to seep into the ground, groundwater is recharged, pollutants are filtered, and erosion is reduced.
This pavement approach can be used to reduce the need for retention ponds, swales, and other stormwater management devices. A pervious concrete mixture contains few fines (sand and small aggregates) allowing “holes” in the material that water flows through into the storage area. Typically the voids represent 15% – 25% of the total assembly. It does require annual cleaning to avoid the voids from being filled with debris.
Pervious paving can be made of concrete, pavers, or asphalt. In our area, pervious paving is more expensive than traditional types of pavement. However, if you also calculate the stormwater measures it is more competitive.