Water Source Control

Sub-base replacement

In certain circumstances such as brownfield sites or roof decks, it is important that the overall depth of the pavement can be reduced. This can be achieved by the use of shallow box attenuation systems which have a substantially greater void ratio than a stone sub-base would, therefore the overall depth of the pavement can be much less. The advantages are as follows:

Brownfield sites

• Savings on excavation
• Savings on haulage of excavated material
• Savings of tipping charges (may be considered contaminated material)
• Savings on aggregate
• Savings on earthwork support

Roof decks

• Minimise overall depth of pavement(200-300mm)
• Minimize load on slab.
• Load spreading capabilities.
• Minimizes point loadings on slab tanking
• Simple easy construction

Downpipe into sub-base

Incorporating sand bedded pavements

On certain projects such as residential schemes, it is entirely feasible to use “standard” sand bedded pavements in the individual driveways, and discharge the storm water falling on them into the permeable pavements on the roadways by standard pipe drainage and geocellular diffuser boxes. The design of these systems will be site specific, dependant upon surface areas, infiltration rates or attenuation requirements. For specific design advice contact us.

Roof drainage

As part of the overall scheme design, the water from roof drainage must be considered. This can be approached in at least two ways.

Re-use
Systems are now readily available on the market to harvest rainwater to provide a valuable free source of water for uses such as toilet flushing, water for washing machines and for watering gardens but to name a few. As we become more aware of the value of this commodity water harvesting will be designed into more and more schemes.

Diffusion
The rainwater from our roof drainage systems can be diverted into the permeable pavements, therefore negating the need to have a separate system to deal with it. As these pavements tend to be quite shallow, perforated pipes are not a practical solution as they cannot carry loads at such shallow depths. A system using geocellular boxes wrapped in geotextile has been developed to increase the surface area available for diffusing the rainwater into the pavement therefore preventing flooding.