Permeable Pavement

Standard forms of asphalt and pavement are impermeable surfaces, meaning that water cannot seep through them. Permeable pavement is a specific type of pavement with a high porosity that allows rainwater to pass through it into the ground below.

Through this movement, the pervious surface mimics the natural process that occurs on the ground’s surface, reducing runoff and returning water to underground aquifers. It also traps suspended solids and pollutants, keeping them from polluting the water stream.

Permeable pavements are somewhat limited in their use: for example, you could not replace a busy roadway with permeable pavement due to the daily wear and tear. However pedestrian throughways, parking spaces, bike lanes, and other low-traffic paved areas represent an opportunity to reduce the impact of the urban settings on the environment.

Permeable Pavements include:

 

Permeable interlocking pavers
Popular, precast modular units made of concrete, pervious concrete or rubber/plastic composite, with open joints between pavers, filled with fine, washed gravel.

Permeable interlocking grids
These precast concrete or manufactured plastic grids have open cells that can be filled with fine gravel or a mixture of gravel, sand and topsoil and planted with grass or low-growing ground covers.

Pervious concrete
Rigid pavement is installed as pre-cast blocks or poured in place, using a binder to adhere aggregate together, similar to conventional concrete — except that the fine aggregate component is minimized or eliminated, resulting in the formation of connected pores throughout.

Porous asphalt
This flexible pavement uses a binder to adhere aggregate together, similar to conventional asphalt, except that the fine aggregate component is minimized or eliminated — resulting in the formation of connected pores throughout.

Permeable articulating concrete block
These precast concrete blocks are designed with open joints that require no gravel joint fill mate-rial, linked together into mats by cables.

In Action

Chicago, Illinois: One particularly creative application of permeable pavements (and natural infrastructure) is Chicago’s Green Alleyways project. Chicago’s 3000 km of alleyways take up a total land surface of 14 km². Many lack proper connection to the stormwater system, causing alleyway drainage issues. Chicago addressed a number of issues that intersect with stormwater management, and adopted a comprehensive strategy to “green” its alleyways through the use of permeable pavements, bioswales, and rain gardens.