Inspection and Maintenance: Permeable Pavement

Inspection & Maintenance Guidance of a built vstormwater best management practices that treats the stormwater that falls on them and can be designed to also receive runoff from adjacent impermeable surfaces (e.g., pavements and roofs) as either sheet flow or from a pipe (e.g., roof downspout) connected to the washed gravel base, where captured water is temporarily stored in the base where it later soaks into underlying native soil or sent to a municipal stormsewer/other BMP via underdrains (TRCA, 2016)

Overview

Permeable Pavement Permeable pavements contain many small openings (i.e., joints or pores) that allow rainfall and snowmelt (i.e., stormwater) to drain through them instead of running off the surface as it does on impervious pavements like conventional asphalt and concrete. An overflow outlet is needed to safely convey flows during flood events. Depending on the permeability of the underlying soil and other constraints, the pavement may be designed with no sub-drain for full infiltration, with a sub-drain for partial infiltration, or with an impermeable liner and sub-drain for a no infiltration practice. The sub-drain pipe may feature a flow restrictor (e.g., orifice cap or valve) for gradually releasing detained water and optimizing the amount drained by infiltration into the underlying soil.

Key components of Permeable pavements to pay close attention to are the:

• Inlets
• Aggregates
• Choker layer
• Underdrains
• Pavement Surface
• Contributing Drainage Area
• Geotextile
• Overflow outlets

Associated Practices

• Permeable Interlocking Pavers (i.e., Block Pavers) – Precast modular units made of concrete, pervious concrete or rubber/plastic composite designed to create open joints between pavers that are filled with fine, washed aggregate and installed on an open graded aggregate (i.e., clear stone) base and sub-base.
• Permeable Interlocking Grid Systems (i.e., grid pavers) – Precast concrete or manufactured plastic grids with open cells that can be filled with aggregate or a mixture of sand, gravel and topsoil and planted with grass or low-growing ground covers and are installed on an open-graded aggregate base.
• Pervious Concrete – a rigid pavement installed on an open-graded aggregate base that uses a cementitious binder to adhere aggregate together, similar to conventional concrete, except that the fine aggregate component is minimized or eliminated which results in the formation of connected pores throughout.
• Porous Asphalt – a flexible pavement installed on an open-graded aggregate base that uses a bituminous binder to adhere aggregate together, similar to conventional asphalt, except that the fine aggregate component is minimized or eliminated which results in the formation of connected pores throughout.

State of the art methods or techniques used to manage the quantity and improve the quality of wet weather flow. BMPs include Source, Conveyance and End-Of-Pipe Controls.

The portion of water precipitated onto a catchment area, which then flows as surface discharge from the catchment area past a specified point.

Water from rain, snow melt, or irrigation that flows over the land surface.

The natural ground material characteristic of or existing by virtue of geographic origin.

Best management practice. State of the art methods or techniques used to manage the quantity and improve the quality of wet weather flow. BMPs include: source, conveyance and end-of-pipe controls.

Toronto and Region Conservation Authority

Surface runoff from at-grade surfaces, resulting from rain or snowmelt events.

A hard surface area (e.g., road, parking area or rooftop) that prevents or retards the infiltration of water into the soil.

A mixture of mineral aggregates bound with bituminous materials, used in the construction and maintenance of paved surfaces.

The slow movement of water into or through a soil or drainage system.

Penetration of water through the ground surface.

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.

State of the art methods or techniques used to manage the quantity and improve the quality of wet weather flow. BMPs include Source, Conveyance and End-Of-Pipe Controls.