EGY worked with the City of London Corporation to develop the Retrofit SuDS Feasibility Toolkit, a practical framework designed to help their engineers identify and integrate Sustainable Drainage Systems (SuDS) into public realm and highway projects across the Square Mile. The toolkit supports the long-term ambition to create a climate-resilient, greener and more liveable urban environment.
The guide provides a structured, step-by-step process for evaluating SuDS opportunities early in project development – from site familiarisation and catchment review to utility coordination, infiltration testing and detailed feasibility design. It focuses on retrofit-appropriate techniques such as rain gardens, SuDS tree pits, and permeable paving, each accompanied by data sheets, installation considerations, technical section drawings, and benefit ratings.
The toolkit normalises SuDS as a core component of street design, helping practitioners recognise opportunities within constrained urban environments and understand how SuDS can simultaneously manage surface water, support biodiversity, improve air quality, reduce heat, and enhance amenity. Importantly, the guidance clarifies how and when to engage specialist input, ensuring that climate-positive design thinking is embedded from the outset of each project.
By equipping City engineers with a clear methodology and adaptable tools, the Retrofit SuDS Feasibility Toolkit accelerates the delivery of blue-green infrastructure across the Square Mile. It represents a significant step in the City of London’s shift toward multi-functional, sustainable public realm design — ensuring streets and spaces are not only more resilient to climate change, but also healthier and more enjoyable for the people who use them every day.
