Permeable pavement sub-base and base course

Because permeable pavements may be required to support heavy loads (driveways, laneways, etc.), the sub-base and base course may require compaction to prevent heaving and shifting.

Sub-base reservoir

In permeable pavement systems, the sub-base is the layer of granular material that is laid on the sub-grade. The granular sub-base should be clear, crushed 50 mm stone. See the Permeable pavements: Specifications page for detailed sub-base material specifications. The construction steps, key inspection points, and mistakes to avoid for sub-base reservoir are the same as / similar to the guidance given in the storage reservoir section.

However, depending on the municipality and the design, compaction of the sub-base reservoir may be required. For example, the City of Toronto’s Construction Specification for Permeable Interlocking Concrete Pavers details the following steps for sub-base installation.

Construction Steps:

1. Place sub-base aggregate in 200 mm lifts (maximum)
2. Compact each lift with a 9-ton vibratory roller, with two passes in vibratory mode and two passes in static mode, or until there is no visible movement of the aggregate.
3. Use a plate compactor for smaller areas that the vibratory roller cannot reach.

Base course

In permeable pavement systems, the base course lies on top of the sub-base reservoir. See the Permeable pavements: Specifications page for base material specifications. The construction steps, key inspection points, and mistakes to avoid for the base course are the same as the guidance given in the storage reservoir section.

However, depending on the municipality and the design, compaction of the base course may be required. For example, the City of Toronto’s Construction Specification for Permeable Interlocking Concrete Pavers details the following steps for base course installation.

Construction Steps:

1. Place base course aggregate in 100 mm lifts (maximum)
2. Compact each lift with a 9 ton vibratory roller, with two passes in vibratory mode and two passes in static mode, or until there is no visible movement of the aggregate.
3. Use a plate compactor for smaller areas that the vibratory roller cannot reach.

An alternative practice to traditional impervious pavement, prevents the generation of runoff by allowing precipitation falling on the surface to infiltrate through the surface course into an underlying stone reservoir and, where suitable conditions exist, into the native soil.

Gravel, or crushed stone of various size gradations (i.e., diameter), used in construction; void forming material used as bedding and runoff storage reservoirs and underdrains in stormwater infiltration practices.

An underlying bed filled with aggregate or other void-forming fill material that temporarily stores stormwater before infiltrating into the native soil or being conveyed by an underdrain pipe.

A broad category of particulate material used in construction, including sand, gravel, crushed stone, slag, recycled concrete and geosynthetic aggregates, and available in various particulate size gradations.