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Pavements should be constructed as flat as possible for pedestrian safety with drainage systems that effectively capture and release stormwater

Pavement Design

Flat and level pavement design reduces risks to pedestrian safety and requires an efficient surface water management system to prevent hazards caused by ponding and standing water. Effective surface water management also prevents damage to buildings and preserves the life of the pavement. There are two main approaches to surface water drainage; grated pit and pipe drainage and linear drainage.

Grated pit and pipe drainage

1. Grated pit and pipe drainage

Precise and exact grading is required to intercept surface water with the grated pit and pipe option. The pits are located at strategic areas on the pavement to collect the water which is removed from the site via a network of underground pipes.

Not aesthetically pleasing
Undulating pavement involves complex construction and requires costly and extensive earthworks for pipe network
May cause pedestrian safety hazards and property damage, for example runaway shopping trolleys
The longevity of the pavement will be compromised if the pavement settles, creating areas for standing water
Pipes may be easily blocked requiring frequent maintenance
Initial product costs are low, but are generally offset by the issues raised above

2. Linear drainage

Simple one-way falls are required for linear drainage, enabling a continuous line of water capture which quickly and efficiently collects and transfers surface water off site.

Aesthetically pleasing
One way grading is simple and quick to construct, requiring minimal underground pipework
Minimal standing water extends the life of the pavement
Linear drainage can be useful to prevent water transgressing into environmentally sensitive areas and across thresholds
Factory manufactured modular trench drains are produced with a consistent quality and comprise:

  • built-in slopes ensuring efficient drainage to outlets
  • advanced V-shape profiles minimising the build-up of silt
  • precast polymer which is more durable than concrete

Cast-in-situ concrete trench drains require a complex construction process and may result in substandard quality.
There is a limited range of grate options available
Open swales cannot be walked on and may block with debris

Linear drainage

Modular drain price comparison

A report prepared by independent quantity surveyor, Rider Levett Bucknall compared the installation costs of precast modular grated trench drains with cast-in-situ grated pit and pipe systems. The results showed precast modular solutions were the cost effective option.

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