East Midlands Airport

Working in partnership with Aggregate Industries UK Ltd and the Environmental Protection Group a conceptual SUDS design was developed as an alternative to a conventional stormwater drainage and storage scheme for extensions to existing public and staff car parks.

Discharges from the site were constrained and there was need to develop drainage schemes that did not impact on the capacity of the onsite balancing ponds. Site tests established that the soil permeability was low.

Each car park site was considered on its individual merits and different solutions were developed to optimise the characteristics at each location. A combination of SUDS components was utilised, including pervious pavements, Permavoid attenuation and detention ponds.

Traditional drainage solutions for the scheme using a gravity pipe network would result in high flow rates and the need for large ‘end of line’ storage tanks combined with complicated flow and velocity control devices in order to meet site specific drainage requirements. The use of these elements was not possible for numerous reasons; firstly this approach would have invalidated the sustainability aspect of the existing scheme as such traditional solutions are not sustainable at all; furthermore, space and water quality constraints (hydrocarbons and siltation) could not be overcome and finally, target costs could not be met.

The Permavoid system has been designed to address all the problems successfully and economically.

The key components utilised were Permavoid sub base replacement units and Permachannels. The Permavoid system has been designed to:

• Replace sub-base and capping layers with a structural ‘raft’ within the pavement.
• Provide shallow attenuation directly beneath the surface. This simultaneously replaces the traditional pipe network and volume storage system.
• Capitalise on the very high perforated exterior of the Permavoid system (exceeds 65%) to maximize of the infiltration capacity of the existing soils.
• Permachannels were utilised as SUDS source control components. These provided a flexible and economical method of petrol and sediment interception.

The incorporation of a Permavoid system within a carefully designed SUDS scheme facilitated the expansion of the car parking facility with negligible impact on the existing drainage infrastructure and minimal disruption to the existing operation of the facilities.

ClieClient: Manchester Airports Group

Contractor: Bardon Contracting

Design Engineer: EPG Ltd

Permavoid distributor: Aggregate Industries

Date: 2004

Key design aspects: The SUDS design is based on the following parameters:

Area of Permavoid: 750 sq.m (3000units)

Length of Permachannel: 85 lin.m

Area of Pavement: 2550 sq.mnt