Case Studies

Westgate Shopping Centre

SDS GEOlight® protects new shopping centre from risk of flooding.


The original Westgate Centre was built between 1970 and 1972 by Taylor Woodrow; the redeveloped Centre opened in Autumn 2017 and represents the largest single development in Oxford’s history. In addition to over 100 shops spread over 3 storeys, including a flagship 142,000 ft2 John Lewis store, the Centre also incorporates 25 restaurants and cafes, a five screen cinema and 61 residential flats, as well as a new landscaped walkway and two major public squares.

The city’s expanded retail provision supports the role of the City Centre as a designated regional centre. Westgate is one of the most environmentally friendly shopping centres in the UK, with stringent sustainability targets including a full long-term embodied carbon analysis, a UK first for a retail centre.

SDS worked closely with Waterman Group who were commissioned to provide multidisciplinary services covering structural, civil engineering, environmental and flood risk services.

Work commenced on site in February 2015 including construction of a 1,000 space, 2 level, car parking facility with a combined footprint of 45,000m2.


How it works

As part of the sustainability strategy, no pumping is allowed on site, requiring part of the enabling works to include a 2m2 culvert to divert captured rainwater via a major system of attenuation tanks into Castle Mill Stream.

The SDS GEOlight® geo-cellular attenuation tanks are suspended above the basement car park and beneath the John Lewis store and have the capacity to store up to 950m3 of water. The tanks located beneath the footpath that adjoins the bus link road are ultra-high strength GEOlight® 800. In order to meet demands for their longevity the tanks were required to have a minimum design life of 60 years.

The tanked basement and service yard has been designed to take 600mm depth of flood water. The second level basement car park has the potential for use as a flood water storage area should this ever be required. Furthermore, attenuation ensures the surface water discharge will be no greater than the pre-existing situation and will cater for the effects of climate change.


The inherent flexibility of GEOlight® systems meant that SDS alone was able to meet the client’s brief.

As the scheme is founded on Oxford clay, ground conditions and the extensive basement precluded the potential for infiltration basins, wet ponds, swales and constructed wetlands, filter drains, perforated pipes and filter strips. The most viable solutions were identified as living roofs, rainwater harvesting and attenuation tanks. The site is located next to a river so the tanking system was required to prevent lateral water movement.

Harry Chetty, Senior Associate Director, Waterman Infrastructure & Environment Ltd: “The principle of sustainability is fundamental to the development of Westgate Shopping Centre and our adherence to this principle provided our surface water drainage requirements with a number of difficulties to overcome. In close co-operation with SDS we established a unique solution comprising a combination of attenuation tanks, suspended above the basement car park and sandwiched between down stand beams and ground floor slab. Having researched extensively the options available to us it became apparent that only SDS was able to conceive and engineer an effective solution and also undertake its manufacture and installation.”

Westgate is a large and complex urban regeneration scheme that substantially reconfigures almost 6 acres of land in the heart of Oxford.

The Centre’s owner, Westgate Oxford Alliance, is a Joint Venture (JV) between Landsec (Land Securities Group plc) and The Crown Estate, the UK’s largest commercial land owner. The  JV spent 4 years preparing the plans and undertaking extensive consultation with the local community and key stakeholders.

What our other Customers say

The installation of a system comprising a device of concrete construction, until now our only option, would have required the use of a 350 tonne crane and most likely, due to the massive inconvenience not just to us but to the airport and local road network, would not have been feasible at all. The Aqua-Swirl™’s versatility meant that we could design the devices for the specific requirements of this site, without the need for any bends in piping, whilst their inherent strength allowed us to save on time and cost through not requiring a concrete surround. Their compact size and small footprint, together with the lifting supports and straps provided, meant installation was very quick and simple and final placement could be done manually; we needed only a single day in which to dig, position, connect up and back fill.

Brian Fegan, Site Engineer, Whitemountain.

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