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→Planning Considerations:
<h3>Physical Suitability and Constraints
<h3>Physical Suitability and Constraints
In general, permeable pavement systems can be used almost anywhere a traditionally paved system might have been installed. However, these systems have the same site constraints of any infiltration practice and should meet the following criteria:
*Wellhead Protection: Permeable pavement should not be used for road or parking surfaces within
two (2) year time-of-travel wellhead protection areas.
*Winter Operations: Sand or other granular materials should not be applied as anti-skid agents during winter operation because they can quickly clog the system. Winter maintenance practices should be limited to plowing, with de-icing salts applied sparingly (i.e., not as a preventative measure).
*Site Topography: The slope of the permeable pavement surface should be at least one percent and no greater than five percent. The impervious land surrounding and draining into the pavement should not exceed 20% slope (Smith, 2006). Pervious surfaces should not drain onto the pavement
*Water Table: The base of permeable pavement stone reservoir should be at least one (1) metre above the seasonally high water table or bedrock elevation.
* Soils: Systems located in low permeability soils with an infiltration rate of less than 15 mm/hr (i.e., hydraulic conductivity of less than 1x10 -6 cm/s), require incorporation of a perforated pipe underdrain. Native soil infiltration rate at the proposed location and depth should be confirmed through measurement of hydraulic conductivity under field saturated conditions using methods described in Appendix C.
*Drainage Area and Runoff Volume: In general, the impervious area treated should not exceed 1.2 times the area of permeable pavement which receives the runoff (GVRD, 2005). The storage layer under the permeable pavement must be sized to accommodate runoff from the pavement itself and any impermeable areas draining to it.
*Pollution Hot Spot Runoff: To protect groundwater from possible contamination, source areas where land uses or human activities have the potential to generate highly contaminated runoff (e.g., vehicle fueling, servicing and demolition areas, outdoor storage and handling areas for hazardous materials and some heavy industry sites) should not be treated by permeable pavement.
*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.