Posted by Callum Vallance-Poole, on September 19, 2024.
Hollandgreen is a luxury apartment complex located in London’s Kensington, consisting of three residential blocks with 54 apartments. The development also shares its site with the new Design Museum, a Grade II-listed building featuring the world’s largest parabolic copper roof. The museum’s unique roof design channels rainwater to two specific points, necessitating a specialised stormwater management solution. To comply with the Royal Borough of Kensington and Chelsea’s strict discharge limits, engineering consultancy Arup needed to find an effective solution.
Arup collaborated with GRAF UK to design a bespoke stormwater management system. The museum’s siphonic drainage system, which discharges rainwater instantaneously at rates up to 180L/s, required a solution to limit discharge to the public sewer to just 30% of this rate. Together, Arup and GRAF UK developed a tailored system comprising two EcoBloc Flex stormwater attenuation tanks, designed to fit the project’s specific size and shape requirements. Given the clay-heavy soil, these tanks were ideal for controlling water release into the sewage system.
The EcoBloc Flex tanks were strategically placed to align with the existing drainage network, positioned lower than the water flow but higher than the sewer outlets. This setup allowed for precise control of stormwater discharge, ensuring compliance with local authorities and Thames Water regulations. Originally, a capacity of 315m³ was proposed, but detailed analysis and the compact design of the EcoBloc Flex tanks allowed the project to meet requirements with just 212m³, resulting in significant cost savings.
The installed EcoBloc Flex stormwater attenuation tanks provide a highly efficient drainage solution, significantly reducing the load on public sewers and meeting stringent runoff requirements. The system successfully lowered the instantaneous discharge to 70L/s, well within the prescribed limits. The efficient design and installation process also offered substantial financial benefits.
Mike Carter, project director for Arup, expressed his satisfaction: “The flexible, modular design of the EcoBloc Flex stormwater attenuation crates meant we were able to make the tank fit seamlessly with the existing drainage network by positioning it exactly where we needed it: lower than the water flow, but higher than the outlets into the sewers. The GRAF UK team was similarly flexible, working closely with our design team to make sure the system ticked all the boxes while keeping within the project’s tight timeframes.”