Greener Grangetown is a sustainable drainage system (SuDS) project that has also been designed to transform the quality of the public realm and improve cycling and pedestrian infrastructure across a city centre neighbourhood. The result is a more resilient urban sewer network and a street environment that is more attractive - and more useful - for residents and commuters.
This green infrastructure project in Cardiff, the capital city of Wales, removes more than 40,000m³ of rainwater each year from entering the combined sewer network.
The project was driven by a need to reduce volumes of rainwater entering Cardiff’s sewerage system, both to maintain sufficient headroom and to protect the system’s long-term resilience. Our pioneering approach brought civil engineers together with our placemaking team to create ‘rain gardens’ that slow rainwater run-off flows and remove contaminants, cleaning and diverting rainwater directly into the nearby River Taff. Previously, rainwater run-off was pumped 8km for treatment before being discharged into the sea.
Our design team worked closely with our client, City of Cardiff Council as well as scheme partners water utility Dŵr Cymru Welsh Water and environmental authority Natural Resources Wales. In this collaboration, we maximised the project’s benefits and transformed streetscapes, creating new green infrastructure and enhancing an existing riverside cycle-footpath.
40,000m³ surface water removed from the public sewer network annually
108rain gardens created and 130 trees planted
1st'bicycle street' in Wales
Arup’s detailed feasibility study was instrumental in securing scheme funding from the project partnership. Arup then took on, and successfully delivered, an innovative and award-winning design. ” Ian Titherington Lead Officer - Drainage, City of Cardiff Council
A sustainable approach to rainwater treatment
Rain gardens deliver visual amenity improvements and a more sustainable approach to rainwater treatment. In a natural environment most rainwater gradually soaks into the ground, but in urban environments impermeable surfaces push rainwater run-off into storm drains where it enters the sewer system, mixes with waste water from residences, and is routed for costly sewerage treatment.
Greener Grangetown's rain gardens are planted areas that mimic the natural environment, providing a more sustainable method for catching and cleaning rainwater. When it rains, water flows into the rain gardens where hardy plants and trees soak it up and filter it, capturing and breaking down some pollutants along the way. During heavy storms, water that cannot be absorbed by soil and vegetation travels through pipes at the base of each rain garden and is conveyed to the nearby River Taff.
Managing rainwater close to where it falls not only reduces the volumes of water that otherwise must be treated downstream, but also encourages engineering solutions to be designed as part of wider public realm improvements, creating what is described as ‘green infrastructure’. In this way, civil engineering contributes to community health and wellbeing, raises awareness about sustainable water management, and delivers benefits to local ecology.
Creating Wales' first bicycle street
Greener Grangetown’s public realm improvements include a new 555m ‘bicycle street’ along Taff Embankment. The installation of new crossings, attractive planting that moves parking away from junctions, and a central textured strip in the road that prompts drivers to take extra care have transformed the street. A better-quality street environment for users and residents has been created, reducing motorists’ speeds and improving the visibility of cyclists and pedestrians. The result is a residential street where bicycles take priority.
Improving cycling infrastructure along Taff Embankment emerged as a Greener Grangetown design priority, as the street forms part of the UK National Cycle Network Route 8 - one of the busiest sections of Wales’ cycle network. During rush hour, it is heavily used by commuters cycling and walking to and from work. This street is the only part of the Cardiff section of Cycle Route 8 that mixes cyclists with motorists, and until the Greener Grangetown design improvements, it was a noticeably weak element of the route. Now cyclists' safety has been improved.
We're so pleased to have worked on such an innovative and forward-thinking project like Greener Grangetown. This exciting scheme, and Arup's extensive work to bring our initial thoughts and community feedback to life, demonstrates a different approach to managing our natural resources - one that looks at the whole picture rather than focusing on single solutions or individual parts of our environment. Not only does this scheme contribute to a healthy and resilient local environment, it also supports economic and social prosperity. ” Martyn Evans Senior Policy Advisor, Natural Resources Wales
Engineering Project of the Year
2018 UK Water Industry Awards