Permeable pavement, also known as pervious or porous pavement, or porous concrete or asphalt, is a type of hard surface with large spaces that allows stormwater runoff to infiltrate into drainage layers and the underlying soils below.
This water either replenishes ground water sources or is removed by a sub-drain placed in the drainage layer that connects to the existing stormwater system. Permeable pavement is one of many low impact development practices that helps manage Calgary's stormwater system.
Information on permeable pavement including specification requirements can be found in the following documents:
- Stormwater Source Control Practices Handbook
- Permeable Pavement Development Approvals Checklist
- Module 6: Permeable Pavement
Types of permeable pavement
The two main types of permeable pavement are:
- Permeable concrete and asphalt
This type of pavement is poured on site and resembles solid concrete or asphalt. The difference is that fine material like sand is removed from the mix to create larger void spaces in the final pavement for water to flow through and into the drainage layers and soil below.
- Permeable paving stones
Permeable pavers are solid individual units typically made of pre-cast concrete, brick, stone or cobbles. The paving stones are set with gaps between stones which allow water to flow between them and into the drainage layers and soil below.
How does permeable pavement work?
Like other low impact development technologies, the main purpose of permeable pavement is to slow down stormwater and to reduce the volume of stormwater returning to our local waterways.
Incorporating permeable pavements into development reduces the hard surface area without losing functionality of a stable load-bearing surface like a road.
Benefits of permeable pavement
Permeable pavements offer a number of benefits such as:
- Allowing ground water levels to be replenished
- Reducing peak runoff periods which can minimize local flooding
- Reducing the total volume of stormwater runoff from a catchment area which reduces the potential for erosion of our riverbanks
- Filtering pollutants through the rock drainage layers and the subsoils below. Research on permeable pavement shows they are effective in removing pollutants such as total suspended solids, heavy metals, oil and grease.