Grey to Green (Phase 1)

Grey to Green (Phase 1)

CEEQUAL Very Good – Construction Award
Version 5 for Projects, May 2016

Sheffield, England, UK

Shortlisted – CEEQUAL Outstanding Achievement Awards 2016

Project team

Client: Sheffield City Council;
Constructor: North Midland Construction;

Assessor: Selina Morson (North Midland Construction)
Verifier: Lucinda Farrington (Seriously Green)


The ‘Grey to Green Phase 1’ project is a radical proposal from Sheffield City Council to transform redundant carriageway in the city centre into a network of sustainable drainage and rain gardens. The project has improved the city’s resilience to climate change, enhanced the public realm, and increased connectivity in the city centre. The project is now attracting investment in new and existing jobs.


Located in the Riverside Business District of the city centre, the area is home to the Law and Family Courts, South Yorkshire Police West Bar offices, and several important regional businesses. It is surrounded by significant numbers of residential flats that overlook the River Don in the Riverside and Kelham Island parts of the City Centre. The area suffered catastrophic floods in 2007 and several large development sites within the area have largely been overlooked by developers due to the previously poor physical environment and facilities.

The completion of the Inner Relief Road in 2008, which used to come through this area, offered an opportunity to address these issues in a new way.

The overall project aims to transform 1.2 kilometres of redundant roads into attractive linear public spaces, improving the links between the Riverside Business District and the rest of the city centre. It includes innovative perennial meadows, an interlinked Sustainable Urban Drainage System (SUDS), rain gardens, eye catching public art totems exploring local history, and high quality paved footways and street furniture. The scheme has been designed to improve the environment, making it easier to walk and cycle. The completed Phase 1 scheme comprises around 0.5 km.

The Client for the scheme was Sheffield City Council (SCC) and following a competitive procurement process, the construction was awarded to North Midland Construction. The Design Team was led by SCC’s Landscape Design Team, both for the landscape as well as the Sustainable Urban Drainage elements. Amey were the Highway and Lighting Engineers. The University of Sheffield’s Landscape Department provided technical advice on the planting element. Robert Bray Associates provided advice on the SUDs design and hydrological modelling. Turner & Townsend provided the project management and quantity surveyor roles. SCC’s Drainage Department have adopted the SUDs system.

Funding was secured from The European Regional Development Fund (ERDF) and the Sheffield City Region Infrastructure Fund (SCRIF) for Phase 1. The project started on site in February 2015 and was significantly completed in February 2016.

The scheme has raised a lot of national interest and achieved a CEEQUAL ‘Very Good’ Construction Award. Feedback since the significant completion of the scheme, particularly as the planting starts to mature, has been very positive from both the businesses and residents in the area as well as the increasing number of visitors who come to see the scheme.

Funding is currently being sought for Phase 2 which will continue the approach onto Castlegate. Phase 3 will finally take the scheme on to Kelham Island and Victoria Quays.


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Environmental improvements through good quality planting are recognised as adding economic value to city centres. The Creating a Setting for Investment project promoted by South Yorkshire Forest (2008) concluded that quality public realm and open spaces and good sustainable design works in a business sense by providing higher returns on investment. Landscape quality also helps to create the right business image.

Once the decision had been taken to construct the significant SUD system, and make permeable a large area that had been impermeable, it was important to think about the planting scheme for both the SUDs and other soft landscaped areas created by the Grey to Green scheme. The easiest solution would have been to grass the SUDs. However, the Council had the vision to achieve an urban meadow in the middle of the City Centre through low input perennial planting.

The construction of the Grey to Green public infrastructure improvements has followed the Sheffield Urban Design Compendium and a three year dedicated maintenance regime has been agree in order to enable the plants to establish fully. SCC landscape experts led the design with technical advice on the planting from the landscape department experts at the University of Sheffield that designed the wild flower meadows for the Olympic Village in 2012.

The following have been planted as part of the project:

  • 40 new additional trees: 30 semi mature (12 Gleditsia triacanthos ‘Skyline’; 11 Quercus palustris and 7 Cercis siliquastrum) plus 10 multi-stemmed (Betula pendula);
  • 45,000 bulbs including: Allium, Camassia, Cyclamen, Eremurus, Fritillaries, Galanthus, Galtonia, Gladiolus, Lilium, Nectaroscordum, Nerine, Ornithogalum and Tulipa.
  • 665 evergreen plants including: Artemisa Arborescens ‘Powis Castle’, Cornus kousa ‘China Girl’, Euonymus alatus ‘Compactus, Phlomis tuberosa ‘Amazone’, Pinus mugo ‘Mops’, Rosmarius ‘Miss jesops upright’, Sarcococca hookeriana ‘Digyna’, Viburnum plicatum, ‘Mariesii’ and Yucca flaccida ‘Ivory’.
  • 26,000 herbaceous plants including: Achilleas, Amsonia, Aster, Betonica officinalis, Calamintha, Dianthus, Erodium, Iris, Kniphofia, Lychnis, Miscanthus, Panicum, Persicaria, Primula, Salvia, Saponaria, Sedum, Verbena and Veronicastrum

The growing medium is not a traditional ‘topsoil’. Instead, it uses a custom mix of crushed sandstone aggregate, recycled glass sand, composted green waste, and sandy silt loam. This creates a very free draining growing medium that suits the species chosen and also minimises weed growth.

The result is a striking planting scheme that is very different to anything the Council has ever done before and it is believed to be unique in a UK City Centre setting. It will provide changing seasonal interest while remaining low maintenance – the main operation being a once per year cut in the autumn before the plants and bulbs come back in the spring.

The feedback on the planting scheme has been extremely positive. The following comment was received on 9th June:

“I work in Sheffield’s Riverside Business District and walk everyday through the Turning ‘Grey to Green’ project. The wild flower scheme that has been recently planted on Bridge Street is beautiful… The design of the new space and planting scheme is one of the most inspiring developments I have seen in Sheffield. Good luck with the rest of the project!”

Water Environment

The Grey to Green project has involved removing considerable areas of Highway surfaces within a highly impermeable city centre location. This not only reduces the area generating surface run-off but also provides the space to manage the remaining areas more robustly. Newly created green infrastructure modified as a series of swale cells provides environments to capture, clean, infiltrate, move, and store water.

Reconfiguring the surfaces within urban areas provides the opportunity to achieve improvements in water management for both flood risk and water quality benefits. Not only are there local benefits in the immediate environment but potentially cumulative impacts of these activities as part of the wider catchment.  As has been identified in various studies, opportunities need to be utilised to improve future resilience whenever investments are made in the urban fabric. These environmental improvements allow climate proofing of drainage networks by building new on or near surface capacity to take account of future predicted increases in intensity of rainfall. Green infrastructure can aid with interception of flow paths of water particularly prominent within the steep topography of Sheffield.  This retaining of surface run-off also promotes groundwater recharge – returning this part of the catchment to a more natural hydrology and in so doing retaining moisture within what are predicted to be higher temperatures within the city core.

The scheme has sought to maximise the spatial opportunity for surface run-off flow management taking into account the complexities presented by a city centre with extensive services and ground contamination.  This has meant depths and locations of the SuDS has had to remain flexible during design – and to some extent the actual construction – as determining the exact location of services proved challenging. Geoenvironmental assessment of contamination pathways under infiltration conditions has proven that systems need not always be lined in such conditions.  This has allowed proper connectivity between new planting media and the underlying ground promoting a more sustainable planting system and more natural catchment behaviour with losses into the ground of clean water.

Sheffield has increasingly made a resource of its water for example through promoting river access and water quality improvements. Grey to Green has provided the opportunity to redirect rainwater to watercourses that was previously sent to treatment works through combined sewers. This supplements the base flow of watercourses that have otherwise been isolated from their catchments.

The Grey to Green project has applied the principle of using water in the landscape, which has proven a successful element within city centre regeneration. Green infrastructure provides the most robust treatment mechanism for highway run-off in capturing and breaking down pollutants. As a result of this this project can demonstrate clean water becoming an asset to a wider landscape through its movement.

The SUDs techniques proposed have been little utilised within a UK city centre context. Receiving landscapes are of a scale where maximum benefit can be made of the temporary water. The Grey to Green Phase 1 SUDs scheme is believed to be the longest retro-fitted in an urban setting in the UK.

This scheme has realised the opportunity to demonstrate best practice to inform further investments in the highway environment. Improving the performance of sewers to reduce sewer flooding and combined sewer overflows and managing overland flows are national issues driven by legislation such as the Flood Directive, Water Framework Directive and Flood and Water Act. Inter-agency working to address these issues is often hindered by restrictions on individual organisations. Regeneration projects driven by a range of aims can unlock these difficulties and demonstrate on the ground tangible results, which encourages wider confidence to work in partnership (SCC, Robert Bray Associates, Amey and Yorkshire Water), as the Grey to Green project has demonstrated.