Description

The SUDS used at Bristol Business Park incorporated a number of features including permeable paving, swales and a detention pond.

Permeable paving

By capturing run off and slowing its flow, the permeable paving system prevents flooding without requiring the same volume of retention pools as other types of urban drainage system.

The permeable paving comprises paving blocks with ‘notches’ at the ends to allow water to drain down, running through a grit bedding layer and into the porous sub-base. The bedding layer helps to clean the water, while the porous gravel slows the water flow rate.

The designer chose the ‘Formpave’ permeable paving system, as it encompasses all aspects of collecting and discharging surface water. It features ‘geotextile’ below the bedding grit, which makes it easy to maintain without removing the porous sub-base. The design team saw ease of maintenance a priority so that the SUDS would remain functional in the long term.

Detention pond

Water that collects in the porous gravel layer is discharged into swales and stored in the detention pond in the south-east corner of the site. This pond also holds run off from earlier phases of the business park, replacing the need for the dry detention pond and roadside ditch that had been used for this phase.

Car parks and rooftops

The car parking areas in the final phases of the business park are surfaced with a mixture of permeable and impermeable paving, both supplied by Formpave, with a porous sub-base running throughout. The impermeable paving has been laid in such a way that water falling onto it runs on to the permeable paving.

Some of the buildings have rainwater downpipes that allow rain that falls onto the rooftops to be fed into the permeable paving drainage system. The downpipes discharge the water into shallow pipes, through small accessible silt traps and into the porous gravel layer.