Changes

*Risk of Soil Contamination: Available evidence from monitoring studies indicates that small distributed stormwater infiltration practices do not contaminate underlying soils, even after more than 10 years of operation (TRCA, 2008).

*Risk of Soil Contamination: Available evidence from monitoring studies indicates that small distributed stormwater infiltration practices do not contaminate underlying soils, even after more than 10 years of operation (TRCA, 2008).

*Winter Operation: For cold climates, well-designed mixes can meet strength, permeability, and freeze-thaw resistance requirements. In addition, experience suggests that snow melts faster on a porous surface because of rapid drainage below the snow surface. Also, a well draining surface will reduce the occurrence of black ice or frozen puddles (Cahill Associates, 1993; Roseen, 2007). Systems installed in the Greater Toronto Area have generally not suffered from heaving or slumping (TRCA, 2008b). Permeable pavement is typically designed to drain within 48 hours. If freezing should occur before the pavement structure has drained, then the large void spaces in the open graded aggregate base creates a capillary barrier to freeze-thaw. Permeable pavers have the added benefit of having enough flexibility to handle minor heaving without being damaged. Permeable pavement can be plowed, although raising the blade height 25 mm may be helpful to avoid catching pavers or scraping the rough surface of the porous pavement. Sand should not be applied for winter traction on permeable pavement as this can quickly clog the system.

*Winter Operation: For cold climates, well-designed mixes can meet strength, permeability, and freeze-thaw resistance requirements. In addition, experience suggests that snow melts faster on a porous surface because of rapid drainage below the snow surface. Also, a well draining surface will reduce the occurrence of black ice or frozen puddles (Cahill Associates, 1993; Roseen, 2007). Systems installed in the Greater Toronto Area have generally not suffered from heaving or slumping (TRCA, 2008b). Permeable pavement is typically designed to drain within 48 hours. If freezing should occur before the pavement structure has drained, then the large void spaces in the open graded aggregate base creates a capillary barrier to freeze-thaw. Permeable pavers have the added benefit of having enough flexibility to handle minor heaving without being damaged. Permeable pavement can be plowed, although raising the blade height 25 mm may be helpful to avoid catching pavers or scraping the rough surface of the porous pavement. Sand should not be applied for winter traction on permeable pavement as this can quickly clog the system.

*On Private Property: If permeable pavement systems are installed on private lots, property owners  or managers will need to be educated on their routine maintenance needs, understand the long-term maintenance plan, and may be subject to a legally binding maintenance agreement. An incentive program such as a storm sewer user fee based on the area of impervious cover on a property that is directly connected to a storm sewer (i.e., does not first drain to a pervious area or LID practice) could be used to encourage property owners or managers to maintain existing practices.  

*On Private Property: If permeable pavement systems are installed on private lots, property owners  or managers will need to be educated on their routine maintenance needs, understand the long-term maintenance plan, and may be subject to a legally binding maintenance agreement. An incentive program such as a storm sewer user fee based on the area of impervious cover on a property that is directly connected to a storm sewer (i.e., does not first drain to a pervious area or LID practice) could be used to encourage property owners or managers to maintain existing practices.  

*Clogging: Susceptibility to clogging is the main concern for permeable paving systems. The bedding layer and joint filler should consist of 2.5 mm clear stone or gravel rather than sand. Key strategies to prevent clogging are to ensure that adjacent pervious areas have adequate vegetation cover and a winter maintenance plan that does not include sanding. For concrete and asphalt designs, regular maintenance that includes vacuum-assisted street sweeping is necessary. Isolated areas of clogging can be remedied by drilling small holes in the pavement or by replacing the media between permeable pavers.

*Clogging: Susceptibility to clogging is the main concern for permeable paving systems. The bedding layer and joint filler should consist of 2.5 mm clear stone or gravel rather than sand. Key strategies to prevent clogging are to ensure that adjacent pervious areas have adequate vegetation cover and a winter maintenance plan that does not include sanding. For concrete and asphalt designs, regular maintenance that includes vacuum-assisted street sweeping is necessary. Isolated areas of clogging can be remedied by drilling small holes in the pavement or by replacing the media between permeable pavers.

*Setbacks from Buildings: Permeable pavement should be located downslope from building foundations. If the pavement does not receive runoff from other surfaces, no setback is required from building foundations. Otherwise, a minimum setback of four (4) metres down-gradient from building foundations is recommended.  

*Setbacks from Buildings: Permeable pavement should be located downslope from building foundations. If the pavement does not receive runoff from other surfaces, no setback is required from building foundations. Otherwise, a minimum setback of four (4) metres down-gradient from building foundations is recommended.  

*Proximity to Underground Utilities: Local utility design guidance should be consulted to define the horizontal and vertical offsets. Generally, requirements for underground utilities passing under or near permeable pavement will be no different than for utilities in other pervious areas. However, permeable pavement has a deeper base than conventional pavement which may impact shallow utilities.

*Proximity to Underground Utilities: Local utility design guidance should be consulted to define the horizontal and vertical offsets. Generally, requirements for underground utilities passing under or near permeable pavement will be no different than for utilities in other pervious areas. However, permeable pavement has a deeper base than conventional pavement which may impact shallow utilities.