Sustainable drainage key to success at mega B&Q hub

As a result of an internal audit, B&Q decided to locate a new regional centre in the south of the UK for high volume products. The aim of this was to bring goods closer to the stores, and in turn enable B&Q to improve customer service, cut transport costs and reduce CO² emissions.

Appointed by GLP, we delivered civil, structural, highways and geotechnical engineering for the detailed design of the development and associated highway improvement works for the 74,000 sq. m B&Q distribution facility at G.Park in Swindon.

Our co-ordinated and innovative approach across all elements of the on-site and off-site detailed design enabled the client to work within the tight budgetary and programme constraints identified at the outset of the project.

We played a significant role in the planning process involved providing structural, civil and highways input into the planning submissions for the Reserved Matters Planning Application, including information required to discharge the conditions of the outline planning permission.

Our design included a cost-effective ground improvement solution to address poor ground conditions at the northern end of the building as an alternative to piling. Wick drains and vibro stone columns were installed below lime-stabilised fill material and the completed platform was surcharged for a two-month period.

The sustainable urban drainage (SuDS) solution we created was key to gaining approvals for the drainage strategy. Commended by the Environment Agency as being a “good example of best practice”, the scheme incorporated the full SuDS management train approach with water butts and rainwater harvesting as prevention measures, permeable paving and filter trenches as source control measures, and large attenuation ponds as site-wide measures restricting the flow to the local watercourse to mimic the pre-development rates. In line with B&Q’s aspirations for the centre to be as environmentally friendly as possible, the centre has achieved a BREEAM rating of excellent.

We also successfully overcame a major challenge in relation to foul water disposal. Thames Water initially thought that the closest sewer had insufficient capacity to receive waste water from the development based on estimated flow rates using the available guidance. We researched water use data from similar developments to demonstrate that the actual discharge rate would be significantly lower than previous estimates. As a result, Thames Water accepted the proposed connection, therefore saving the considerable cost of alternative solutions.

We were also responsible for the detailed design of the s.278 off-site highway scheme to improve traffic flow in the area, including the reconfiguration of three roundabouts on one of the main commuter routes into Swindon town centre. We achieved technical approval to the detailed design of the substantial works in a seven-month period – a significant achievement for a project of this nature and size where the highway impacts affect both the local and the strategic road network.

Our performance on this project was commended by our client, GLP, the Environment Agency and the Highway Authority.