In urban environments impermeable surfaces push rainwater run-off into storm drains where it enters the sewer system, mixes with wastewater from residences, and is routed for costly sewerage treatment. This 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. 

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. Our pioneering approach brought together civil engineers and 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.

We maximised the project’s benefits and transformed streetscapes, creating new green infrastructure and enhancing an existing riverside cycle-footpath. The result is a more resilient urban sewer network and a street environment that is more attractive - and more useful - for residents and commuters.

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

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.  

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.