Cloughbank A Drainage Remedial Trial – 2024-2025

Sector: Aviation (landside).

Client: Manchester Airport Group (MAG).

Value: £2,100,000.

​​​​Duration: May 2024 to March 2025. 

Scope: 

• Site clearance.

• Service clearance.

• Removal of the existing limestone aggregate and asphalt surfacing

• Installation of FORMAVOID © drainage system

• Installation of new kerbing to the carriageway. 

• Installation of a new asphalt spine road, and porous asphalt surfacing of the parking areas

• Installation of new line marking, street furniture (including bus shelters) and lighting columns

• Installation of new pit and duct containment associated to new pH monitors.

Summary: Allied Infrastructure was awarded this project in early 2024, following a competitive tender process on the MAG Small to Medium Framework. The project was focussed on rehabilitating a disused section of landside car park adjacent to Manchester Airport’s “Staff South” Car Park, whilst also trialling a new surface water management system. This would provide 2 main benefits – increasing operational parking capacity, and proving the efficacy of a new attenuation system in advance of future projects. 

The existing car park had historically suffered from surface water discharge issues, predominantly due to the very high pH level of the water discharging from the site. This necessitated the collection, pumping and treatment of the drainage effluent, prior to discharge. The project was commissioned to bring the circa 8,400M² car park back into operational use, whilst ensuring that surface water could effectively drain into the adjacent watercourse without treatment, and with no contamination occurring.

The main trial construction phase ran from May 2024 to November 2024, with an additional trial area added in the latter stages of the project. Key scope elements included:

The FORMAVOID © drainage system was supplied and installed by our sub-contractor SEL Environmental Ltd. It is based around an impermeable membrane, overlaid with a layer of lightweight, plastic void pots. These pots are then filled with an open-graded granular material. This creates a strong but permeable sub-surface layer, which enables effective attenuation, without the need for deep drainage. The void pots are manufactured from "Carbon Zero" recycled polypropylene, ensuring sustainability.

As the works were delivered within an operational car park and adjacent to the SSSI Cotterill Clough Woodland, there were a variety of sensitivities to be considered. Key controls included: 

The escorting of all vehicle movements through the car park, the use of eco-friendly site cabins (negating the need for large quantities of bulk fuel), and service-proving activities using vacuum excavation, prior to the main works.