ACO’s space-saving stormwater attenuation tank, StormBrixx, has played an important role in the completion of the challenging groundworks phase at Network Rail’s Didcot Parkway station redevelopment in Oxfordshire.
Main contractor Balfour Beatty sought a sustainable surface water management solution that could be installed quickly, with minimal disruption – and the unique modular design offered by StormBrixx, provided the answer.
Due to complete this Spring, the £6.7m redevelopment of Didcot Parkway Station centres on resolving the station’s poor layout, traffic congestion and its vulnerability to flooding. The project will result in an attractive and efficient interchange for public and private transport, ensuring it has the capacity to meet future travel demand as the number of people living and working in the area increases.
To tackle the flooding issue, main contractor Balfour Beatty installed a sustainable surface water management scheme (developed by Jacobs Engineering Group) that utilises space beneath two of the station’s three new car parks, to accommodate attenuation tanks with sufficient capacity to hold and safely discharge run-off from across the redesigned pedestrian piazza and forecourt.
“In order to achieve the volume required, we had to excavate virtually the entire deck area of the two car parks,” said Balfour Beatty Site Agent, Tony Mills. “Restricted by a major trunk road on one side and the rail track embankment on the other, it left very little free space for the groundworkers and tank installers to store equipment. Tight installation schedules added to the challenge. To avoid delays we needed to have all the tank components on-site to allow the build team to work unhindered once the excavation stage was complete.”
Key to Balfour Beatty’s decision to use ACO StormBrixx was its unique modular design, which allowed all the tank components to be stacked, transported and stored in just 25% of the space required by conventional crate-based systems. Less cumbersome and easier to handle, StormBrixx produces a stronger more stable structure that can be configured to any size or location, overcoming the construction limitations and drawbacks suffered by traditional tanks.
Tony adds: “By using StormBrixx, not only were we able to hold sufficient stock within the tight space to keep the laying team adequately supplied, but we were also able to reduce transportation costs as both tanks could be loaded onto a single truck. This had the added benefit of significantly lowering the whole logistics operation’s carbon emissions.”
The two tanks are inter-connected with a single discharge (limited to a maximum 10 litres/second) to an adjacent watercourse. The upstream ‘offline’ tank has a volume of 297m3 and only fills if run-off flowrates from its catchment exceed 4 litres/second. The downstream ‘online’ tank attenuates both the run-off from the offline catchment as well as from its own.
Run-off discharge rates from both catchments are controlled using two ACO Q-Brake Vortex flow control units. The discharge from the online tank first passes through an oil separator before being released into the watercourse.
As the tanks are set up to attenuate stormwater, each is wrapped in a two part membrane that prevents any infiltration into the surrounding sub-soil and eliminates any silt penetrating the tank walls. First a welded geomembrane liner system sits immediately adjacent to the tank walls; this is then encased in a protection fleece, which safeguards the integrity of the overall structure.
Stormbrixx is part of ACO’s core surface water management system offering and is part of a wide range of solutions suitable to rail infrastructure projects, which also includes more specialist products designed specifically for applications such as track slab, platforms, station buildings and infrastructure; parking areas, maintenance and storage depots.