Permeable pavement allows precipitation to slowly soak into the ground, thereby reducing runoff from driveways, roads and parking lots. There are two main types of permeable pavement – permeable pavers (also known as interlocking concrete blocks) and porous pavement. These BMPs can be incorporated into designs for new developments, or used as a retrofit option for existing homes and buildings.
Permeable Pavers consist of impervious concrete blocks or tiles that allow water to infiltrate between blocks in voids filled with gravel or grass.
|Permeable Paver (photo: bit.ly/be1x3a)|
|Parking space at the Ecology Action Centre|
Porous Asphalt or Concrete consists of standard asphalt or concrete mixes with the finer aggregates removed resulting in pores within the pavement that allows water to permeate through the surface.
A parking lot on the Dalhousie University campus uses porous pavement to reduce stormwater runoff. The lot was graded allowing runoff to flow towards the strip porous pavement area at one end of the lot. There is a clear stone base under the permeable area with a perforated PVC pipe leading to catch basin in the corner of the lot. Water that infiltrates through the pavement has a chance to soak into the ground before being picked up by the perforated pipe. A strip of permeable pavement on a graded lot works well, therefore repaving the entire parking lot is not necessary. Some concern exists about how porous pavements can withstand Nova Scotia's harsh winter conditions, however this was put in during the Fall of 2010, and there has been no damage reported to date.
|Strip on porous pavement on a Dalhousie University parking lot (width of the car)|
|Regular asphalt on the left, porous pavement on the right|
The City of Vancouver is using an alternative approach to reduce imperviousness on residential side streets called ‘Country Lane Treatment’. This design incorporates a soil and grass covered plastic mat between two parallel concrete driving strips. Permeable pavers were used to connect driveways to the driving strips. Click here to see more examples of road treatments from Vancouver.